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Volume 30
Issue S1
September 2014
ISSN 1120-1797
Physica
Medica
European Journal
of Medical Physics
The official journal of the
Associazione Italiana di Fisica Medica,
European Federation of Organizations for Medical Physics,
Irish Association of Physicists in Medicine and
Société Française de Physique Médicale
Abstracts from the 8th European
Conference on Medical Physics
September 11th–13th, 2014
Athens, Greece
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Editor-in-Chief: Paolo Russo
Past Editor-in-Chief: Fridtjof Nüsslin
30-08-2014 17:14:06
Abstracts from the 8th European Conference on
Medical Physics
September 11th–13th, 2014
Athens, Greece
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Physica Medica:
European Journal of Medical Physics
Volume 30, Supplement 1, 2014
The official journal of the European Federation of Organizations for Medical Physics,
Associazione Italiana di Fisica Medica, Société Française de Physique Médicale
and Irish Association of Physicists in Medicine
Physica Medica is recognised by the European Physical Society
CONTENTS
Invited Lectures
8
Oral Presentations
23
E-Posters with presentation
52
E-Posters
82
Physica Medica 30S1 (2014)
Contents lists available at ScienceDirect
Physica Medica
journal homepage: http://www.physicamedica.com
Invited Lectures
PATIENT DOSE AND IMAGE QUALITY: ROLE OF MEDICAL PHYSICISTS
Francis R. Verdun. Institute of Radiation Physics (IRA), CHUV, Lausanne,
Switzerland
Introduction: Radiation protection in medicine is becoming a real challenge when dealing with the use of technologies such as CT, fluoroscopy
and PET/CT. In Switzerland, since January 2012, medical physicists have to
be involved with the medical team dealing with “high dose procedures”
such as the ones mentioned above to strengthen the optimization process.
This new role for medical physicists has a strong potential in the framework of medical radiation protection. The aim of this presentation is to
show, using a few examples, how the introduction of this new legal
requirement can improve radiation protection not only of the patient but
also of the staff.
Material and Method: Our Institute is in charge of consulting more than
twenty-five centers (50 CT units; 10 fluoroscopy units used for interventional radiology and cardiology and 5 PET/CT units). These units have been
monitored using common protocols that, while integrating some standard
quality assurance measurements, mainly focus on the way the unit is used
in practice.
Results: A wide variation of protocols is applied for comparable indications. For example, patient doses for a standard abdominal CT examination can vary by a factor of 23. Cumulative doses over 5 Gy can be very
common in some centers without taking any special measures to inform
the patient of the possibility to develop tissue reactions. To improve the
present situation, several measures should be introduced: standardization
of the CT protocols nomenclature, standardization of the interventional
procedures’ names, and definition of clinically relevant image quality
levels.
Conclusion: The implication of medical physicists in radiology and nuclear medicine has the potential to improve the optimization of radiological procedures. As opposed to radiation therapy, precision in dose
measurements should not be the main role of medical physicists. She/he
should part of the medical team to improve the standardization of the
examinations’ or procedures’ nomenclature and to develop a strategy to
provide the physician with clinically relevant measures of image quality.
Then one could work on the balance between diagnostic information and
risk.
DOSE REDUCTION IN INTERVENTIONAL RADIOLOGY & CARDIOLOGY
Renato Padovani. ICTP Abdus Salam Int. Centre for Theoretical Physics,
Trieste, Italy
Optimisation of patient and staff exposure in interventional radiology
(IR) and cardiology (IC) practice is the objective of more than 20 years of
national and international studies, recommendations and actions. But,
the large and increasing number of procedures and the large involvement of professionals outside the radiology department have partially
impaired these efforts with the results, as demonstrated by recent
studies, that the practice in general has not yet reached acceptable
optimisation levels.
For patient exposures, national and international surveys are showing
large variations in the practice, n the performance of radiological equipment, in the technical protocols and, finally, in the patient doses. The
optimization instrument of the DRLs, assessed only for few procedures and
mainly for IC, is rarely implemented and used. The ICRP is putting new
efforts in redefining the methods to assess and use DRLs as a tool to limit
non acceptable dose levels and helping in the optimization process.
For staff exposure, ISEMIR project has highlighted a poor monitoring
practice in IC bringing to important underestimation of doses and, new
challenges for eye lens dosimetry are coming from the 2011 ICRP statement recommending a new and lower eye lens dose limit. Staff monitoring, aiming to assure the compliance with the dose limits, is in general
affected by large uncertainties for staff exposed near the radiation source
and partially protected. These uncertainties are larger for lens eye
dosimetry for the use of protective glasses and for the laterality and the
from-below direction of the irradiation. These large uncertainties, when
the doses are of the same order of magnitude of the limit as happen for
eyes, are not assuring the compliance with the new dose limit. As an
example of advanced dosimetry, the active dosimetry technology can
improve staff monitoring providing instant information on exposures,
allowing the integration of staff and patient exposure data and, finally,
supporting staff education.
To progress in the staff optimization it will be necessary to advance in
dosimetry methods, harmonise dosimetry practice, to develop international databases to support benchmarking, promote optimized procedure
protocols, and require harmonized and certified education and training.
QA IN DIGITAL MAMMOGRAPHY: LOCAL ACTIVITIES AND REMOTE
CONTROL
Hilde Bosmans. KU Leuven, Department of Imaging and pathology, Belgium
Quality assurance in mammography should ensure the optimal balance
between X-ray dose and image quality. The European Guidelines on QA in
mammography include a protocol for digital mammography equipment
that allows to evaluate the X-ray tube, detector, settings of the automatic
exposure control, the monitor and overall image quality. There are no indications as to how assure the quality of the clinical image quality. The
protocol recommends that daily or weekly quality control tests should be
centrally supervised.
Our regional government has required to perform breast cancer screening
in line with the chapter on physico-technical tests. To do so, we implemented yearly and half yearly tests for digital mammography and daily
tests of the X-ray system and the monitors. AQ new X-ray modality has to
pass a type test procedure first. Seen the large number of mammography
systems in our region, the daily and weekly procedures have been largely
automated.
We have contracts for QA activities on 103 mammography units, including
CR and DR systems of all major vendors and 3 more film-screen systems.
During the lecture we will show the software networking platform for
daily QC supervision and the link between these daily data and the results
of half yearly tests.Every day, the centres make 2 acquisitions of a homogenous test object that is rotated over 180 between the 2 exposures.
Raw data are sent to a DICOM receiver program, analysed and sent to the
QC platform of our centre (product of qaelum NV, Belgium). The centres
test also the monitors with a variable test pattern, that shows every day
different low contrast characters to allow the testing of the characteristics
of monitor and reading room. The same platform (qaelum NV, Belgium) is
used for quality supervision.
2
Abstracts / Physica Medica 30S1 (2014)
Recently, 2 scientific papers have confirmed good performance of our
screening program. These studies are also a confirmation for the group of
physicists who have worked at a strict physic-technical quality assurance
system. The networking approach could be copied in other countries of
course.
Session number of session in which the abstract is presented: Scientific
session: QA in radiology; Thursday afternoon, 14.30 e 15.30
Session title of session in which the abstract is presented
FULLY AUTOMATED TREATMENT PLAN GENERATION IN DAILY ROUTINE
B. Heijmen, P. Voet, M. Dirkx, A. Sharfo, L. Rossi, D. Fransen, J. Penninkhof,
ndez Romero, A. Al-Mamgani, L.
M. Hoogeman, S. Petit, J.-W. Mens, A. Me
Incrocci, S. Breedveld. Erasmus MC Cancer Institute, Rotterdam, The
Netherlands
Background: Currently, treatment plans are generated by dosimetrists
using a trial-and-error procedure. The process may take several hours and
plan quality is dependent on the skills and experience of the dosimetrist,
and on allotted time. We have developed and clinically introduced a system for fully automatic plan generation, using lexicographic multi-criterial
optimization to replace the labour-intensive and operator-dependent trialand-error approach.
Materials and Methods: For each patient, the treatment plan is fully
automatically generated by the clinical treatment planning system
(Monaco, Elekta AB), based on a patient-specific template that is automatically pre-generated with our in-house lexicographic multi-criterial
optimizer (“Erasmus-iCycle”, Med Phys. 2012; 39(2): 951). Automatic plan
generation in Erasmus-iCycle is based on a ‘wishlist’ with hard constraints
and treatment objectives with assigned priorities. For each treatment site
(e.g. H&N cancer), a single fixed wish-list is used for all patients. In case of
IMRT, Erasmus-iCycle can be used for integrated beam profile optimization
and (non-coplanar) beam angle selection.
Results: In a prospective clinical H&N cancer study, radiation oncologists
selected the AUTO-plan in 97% of cases rather than the MANUAL-plan
generated by trial-and-error (IJROBP 2013; 85(3): 866-72). For a group of
44 cervical cancer patients, dual-arc VMAT AUTO-plans were superior to
MANUAL-plans generated by an expert cervical cancer planner, spending
many hours; reduced small bowel V15Gy, V45Gy, and Dmean, bladder Dmean,
and rectum Dmean, p<0.001. For 30 prostate cancer patients, differences
between VMAT AUTO- and MANUAL-plans, the latter generated by an
expert planner with up to 4 hours planning hands-on time, were statistically insignificant (IJROBP 2014; 88(5): 1175-9).
Discussion: Automatic plan generation with consistent high plan quality
and vast reductions in planning workload is feasible and has been clinically
introduced for major treatment sites.
imaging systems, as well as the ability to adopt technical advances more
easily in combined imaging hardware, SPECT/CT, PET/CT and PET/MRI will
likely be explored to their full potential. This includes a trend towards
acquiring listmode data routinely and employing different type of models
(kinetic, motion, etc) for subsequent corrections. With PET/MRI, in
particular, we will likely see a trend towards assessing tumor heterogeneity through the adoption of dedicated MR sequences applied locoregionally. This information can be used further for improved imageguided interventions. We will likely see a revival of ideas on anatomyguided corrections (e.g., PVC) and reconstructions with the wider adoption
of combined imaging.
Image fusion in 2020, and beyond, will strongly depend on our ability to
accept combined imaging as a collaborative affair and our intent and
endurance to cooperate with neighbouring disciplines. This pertains to
primarily to medical doctors, but also to technologists and medical physicists.
THE ANTIKYTHERA MECHANISM: DECODING
ANCIENT GREEK ASTRONOMICAL COMPUTER
AN
ASTONISHING
John H. Seiradakis. Aristotle University, Department of Physics, Section of
Astrophysics, Astronomy & Mechanics, GR-541 24 Thessaloniki, Greece
The Antikythera Mechanism was found by chance, in a shipwreck, close to
the small Greek island of Antikythera, in April 1900, by sponge divers. The
shipwreck was dated between 86 and 67 B.C. (coins from Pergamon). Later
the Mechanism was stylistically dated, around the second half of the 2nd
century B.C. (100 e 150 B.C.). About this time the great Greek astronomer
Hipparchos (190 e 120 B.C.) lived in Rhodes.
It was a portable (laptop-size), geared mechanism which calculated and
displayed, with high precision, the movement of the Sun and the Moon on
the sky and the phase of the Moon for a given epoch. It could also calculate
the dates of the four-year cycle of the Olympic Games. It had one dial on
the front and two on the back. Its 30, precisely cut, gears were driven by a
manifold, with which the user could select, with the help of a pointer, any
particular epoch (at the front dial). While doing so, several pointers were
synchronously driven by the gears, to show the above mentioned celestial
phenomena on several accurately marked annuli. It contained an extensive
user’s manual. The exact function of the gears has finally been decoded and
a large portion of the manual has been read after 2000 years by a major
new investigation, using state of the art equipment.
Based on new surface photography and high resolution tomography data, a
new model has been built at the Aristotle University, revealing the technological abilities of ancient greeks.
No complicated geared instruments are known before the Antikythera
Mechanism and for several centuries after. Therefore, this astronomical
device stands out as an extraordinary proof of high tech in ancient times.
IMAGE FUSION IN 2020
Thomas Beyer. Medical University of Vienna, Austria
CURRENT APPROACH IN CLINICAL ELECTRON BEAM DOSIMETRY
Image fusion describes the process of spatial-temporal alignment of
complementary image information. Images can be acquired retrospectively or prospectively. Most commonly image sets originate from different
image modalities. However, image sets from the same modality can be
aligned and fused also for the purpose of longitudinal assessments. Image
fusion is commonly motivated by the need to gain additional information
from the aligned image sets, such as by localizing small lesions on functional, low-resolution images through matched, high-resolution anatomical images.
This presentation reviews briefly the origin of clinical image fusion, which
traces back to the 1960’s when the outline of the neck of patients was
transposed manually on scintigrams for better localization of thyroid uptake and nodular disease. Image fusion advanced quickly by means of
adopting computer-based automated processing. With the introduction of
prototype PET/CT and SPECT/CT systems by the late 1990’s image fusion
became hardware based, thus, offering a number of advantages over
retrospective image fusion. Since 2006 combined PET/MR has become
available for use in humans.
This sets the stage for rapid advances in image fusion in the years to come.
Given the availability of high-end imaging components in the combined
Dimitris Mihailidis PhD. Charleston Radiation Therapy and West Virginia
University, USA
The absolute dosimetry calibration of clinical electron beams is increasingly based on the AAPM Task Group #51 (TG-51) protocol. In addition,
recently published dosimetry data on electrons beams bring up the
question of: how would one need to modify the widely used TG-25 that
originally was based on the older AAPM Task Group #21 (TG-21) calibration protocol?
The 2009 Task Group #70 (TG-70) by the AAPM, is trying to address the
issue above. TG-70 operates as supplement and update to TG-25 on issues
that needed to be modified because of TG-51 approach to electron
dosimetry and because of the more recent data on clinical electron beams.
It describes in detail the method of converting measured depth-ionization
curves with ion chambers into depth-dose curves, making use of recently
published stopping-power ratios and other conversion factors. It also describes the use of water equivalent phantoms to perform relative electron
dosimetry based on recently published conversions factors. The report
discusses small and irregularly shaped electron field dosimetry using the
Abstracts / Physica Medica 30S1 (2014)
concept of lateral buildup ratio (LBR) as an avenue to evaluate electron
later scatter equilibrium and compute dose per MU for those fields. Finally,
it gives some common clinical examples where electron beam dosimetry
are applied.
This presentation will try to provide guidance to the audience for better
understanding the methods and recommendations in TG-70. In addition,
will describe how to link the absolute dose calibration recommendations
of TG-51 to the relative dose measurements of TG-71.
TOWARDS DAILY ADAPTED PROTON THERAPY
Tony Lomax. Centre for Proton Therapy, Paul Scherrer Institute, Switzerland
Proton therapy using Pencil Beam Scanning (PBS) is a highly conformal and
flexible form of radiotherapy. However, anatomic changes of the patient
during the course of therapy are a major challenge due to the potentially
major changes in proton ranges that can result. The challenge is even
greater given that such changes can occur on a daily basis and current
software systems and workflows in radiotherapy are too slow to react to
such changes. In order to fully exploit the highly conformal characteristics
of PBS proton therapy therefore, methods for the daily adaption of proton
therapy need to be developed, a concept we call ‘Daily Adaptive Proton
Therapy’ (DAPT). The concept of DAPT is to work towards a flexible and
fully automated workflow for PBS proton therapy, with the aim of imaging,
planning and delivering a ‘plan-of-the-day’ for patients on a daily basis. In
order to achieve this, the time between the imaging of the patient and
delivery of the plan has to be reduced to a maximum of 1-2 minutes. With
the in-room imaging capabilities of the PSI Gantry 2, and the inherent
flexibility of PBS proton therapy, we believe we already have the ideal
treatment machine for the implementation of DAPT. However, the challenges are more computational and workflow oriented than technological.
In order to move towards a DAPT approach for instance, image registration,
planning and optimisation procedures must be made computationally
efficient and fully automated. In addition, efficient and informative tools
need to be developed that will allow clinical staff to review these ‘plans-ofthe-day’, as well as to allow for fast, but nevertheless safe, quality assurance checks of the plans. For instance, with the introduction of DAPT type
approaches, it will be impossible to perform patient or field specific
dosimetric verifications, and other, automated methods for checking the
fidelity of treatments and treatment control files will need to be developed. Thus, there are many challenges to be met before DAPT will become
a reality. However, we firmly believe that moving in this direction is the
next major advance in clinical proton therapy, and its introduction could
have at least as large an impact on current clinical practice with protons as
the introduction of Intensity Modulated Proton Therapy. Indeed, one could
argue that PBS proton therapy, with its flexible and automated workflow, is
pre-destined for the DAPT concept.
FLUORESCENT NUCLEAR TRACK DETECTORS AS A TOOL FOR ION-BEAM
THERAPY RESEARCH
€kel a,b, c. aGerman Cancer Research Center (DKFZ), Division
S. Greilich a, O. Ja
of Medical Physics in Radiation Oncology, Im Neuenheimer Feld 280, 69120
Heidelberg, Germany; bHeidelberg University Hospital, Department of
Radiation Oncology, Im Neuenheimer Feld 400, 69120 Heidelberg,
Germany; cHeidelberg Ion-Beam Therapy Center (HIT), Im Neuenheimer
Feld 450, 69120 Heidelberg, Germany
Originally designed for optical storage, fluorescent nuclear track detectors
(FNTD) based on Al2O3:C,Mg single crystals contain aggregate F2+
2 (2 Mg)
color centers that show permanent radiochromic transformation when
bombarded with ionizing radiation. Transformed centers produce high
yield fluorescence at 750 nm when stimulated at 620 nm and a short (75±5
ns) lifetime. This enables non-destructive readout using confocal laserscanning microscopes (CLSMs, Akselrod and Sykora, 2011). Since the intensity signal depends on the local energy deposition, 3D particle trajectories through the crystal can be assessed. Together with the excellent
sensitivity Al2O3:C,Mg this enables the derivation of information on track
location, direction, energy loss, etc. over the entire particle and energy
3
range found in ion beam therapy. Effects such as projectile fragmentation
and secondary electron trajectories can be studied in detail with diffraction-limited resolution (Greilich et al., 2013). Due to their biocompatibility,
autoclavability and since post-irradiation chemical processing is not
needed, FNTDs can show significant superiority to existing technologies
such as plastic nuclear track detectors (PNTDs, e.g. CR-39).
Our group studies the FNTD technology for application on three main
fields:
Fundamental dosimetry quantities (w-value, I-value) in ion beams:
FNTDs allow determining particle fluence and range with very high accuracy (Osinga et al., 2013, Klimpki et al., 2013).
In-vivo track-based assessment of dose to organs at risk during therapy:
FNTDs represent one of a few systems that enable biological dose estimation which is the essential predictor for clinical outcome in ion beam
therapy. In addition, FNTD are small, resilient, wireless and biocompatible
and can be therefore used within phantoms, animal models or even
patients.
Radiobiology: our group was the first to use FNTDs as substrate for cell
(“Cell-Fit-HD”, Niklas et al., 2013). This enables to correlate microscopic
physical parameters and subcellular/cell response both in fixed and living
cell and study cellular processes fundamental to ion beam radiotherapy
that are hitherto little understood.
The talk will present the basic principle of FNTD technology, our group’s
technical implementation as well as the latest methodological developments and application results.
References
1. Akselrod MS, Sykora GJ: Fluorescent nuclear track detector technology e
A new way to do passive solid state dosimetry. Radiat Meas 2011,
46:1671e1679.
2. Greilich S, Osinga J-M, Niklas M, Lauer FM, Klimpki G, Bestvater F, Bartz
€kel O: Fluorescent Nuclear Track Detectors as a Tool for
JA, Akselrod MS, Ja
Ion-Beam Therapy Research. Radiat Meas 2013, 56:267e272.
€kel O, Greilich S: Ion
3. Klimpki G, Osinga J-M, Herrmann R, Akselrod MS, Ja
Range Measurements using Fluorescent Nuclear Track Detectors. Radiat
Meas 2013, 56:342e346.
4. Niklas M, Abdollahi A, Akselrod MS, Debus J, J€
akel O, Greilich S: Subcellular spatial correlation of particle traversal and biological response in
clinical ion beams. Int J Radiat Oncol 2013, 87:1141e1147.
€kel O, Greilich S: Absorbed
5. Osinga J-M, Brons S, Bartz J a, Akselrod MS, Ja
Dose in Ion Beams: Comparison of Ionisation- and Fluence-Based Measurements. Radiat Prot Dosimetry 2014.
INCREASING PRECISION IN PARTICLE THERAPY: IN VIVO DOSIMETRY
AND BEYOND
C. Richter a, b, c, d, G. Pausch a, b, d, J. Seco e, T. Bortfeld e, W.
Enghardt a, b, c, d. a OncoRay e National Center for Radiation Research in
Oncology, Faculty of Medicine and University Hospital C.G. Carus,
€t Dresden, Germany; b Department of Radiation
Technische Universita
Oncology, Faculty of Medicine and University Hospital C.G. Carus,
€t Dresden, Germany; c German Cancer Consortium
Technische Universita
(DKTK), Dresden, & German Cancer Research Center (DKFZ), Heidelberg,
d
Helmholtz-Zentrum
Dresden-Rossendorf,
Germany;
Germany;
e
Massachusetts General Hospital and Harvard Medical School, Department
of Radiation Oncology, Boston, MA, USA
The proton dose distribution including the steep dose gradient at the end
of range not only allows a better sparing of normal tissue. It also enforces
the need of a precise control of the dose deposition to ensure the correct
position of the dose gradient to take full advantage of the superior capabilities of proton therapy. Otherwise, factors like tissue heterogeneities,
patient positioning errors and intra-fractional motion can cause high uncertainties in proton distal range resulting in a failing tumor coverage or/
and an unnecessary high dose deposition in healthy tissue due to the use of
extended margins. Therefore, an in vivo verification or any other control of
proton range and delivered dose distribution is highly desirable.
Several in vivo dosimetry approaches will be presented and compared.
They rely on either nuclear interactions of the beam with the irradiated
matter (In beam-PET and prompt g-ray imaging) or on the visualization of
4
Abstracts / Physica Medica 30S1 (2014)
biological processes induced by radiation, e.g. with MRI. The most experience exists for in beam-PET. In Dresden, the current research focuses on
time-resolved acquisition (4D-PET) and on automated detection of range
deviations. In contrast, prompt gamma ray imaging is a relatively new and
dynamic field of research. Several prompt g-ray imaging detector systems
are under development in various research centers around the world
based on active- as well as passively collimated systems. A complementary
approach, based on the time spectrum of the g-ray emission, is investigated in Dresden. First promising results will be presented in the talk.
However, so far there is no clinical application of prompt g-ray based in
vivo dosimetry. In contrast, radiation-induced biological changes have
been used in clinical trials at the Massachusetts General Hospital in Boston
(MGH) for range verification in both, spine and liver. A recent study, also
carried out at MGH, aims at a better understanding of when those treatment related changes in the liver begin to appear.
Instead of assuring a safe and precise treatment by measuring the in vivo
dose deposition, another approach is to decrease dose deposition uncertainties before beam delivery. This can be done in several ways: One
approach tries to increase the robustness of the treatment plan against
different types of uncertainties. This can be realized by including the
robustness in the optimization and penalizing treatment plans with a dose
deposition very prone to expected deviations. A completely different
method for increasing dose deposition precision is based on online imaging during treatment: If the exact patient geometry would be known for
every time point, the delivered dose deposition could be calculated and
even adapted online if necessary. Online imaging could be performed with
MRI scanners integrated in the treatment room in analogy to the combined
MRI-linac approaches. At the moment this is a field of intense research
with quite impressing progress.
At this point it is not clear which of the different methods to increase
precision in particle therapy will find their way in routine clinical application. Nevertheless, the demand and the potential of these methods are
unquestionable.
MONTE CARLO MODELING AND IMAGE-GUIDANCE IN PARTICLE
THERAPY
G. Dedes, K. Parodi. Department of Medical Physics, Ludwig Maximilians
University, Munich, Germany
The use of protons and heavier ions in external beam therapy offers
distinctive advantages with respect to conventional radiotherapy using
electromagnetic radiation. The physical selectivity of ions with the characteristic Bragg curve can enable high tumor-dose conformity, resulting in
lower irradiation of healthy tissues and critical organs in close vicinity to
the target volume. Moreover, the higher relative-biological-effectiveness
(RBE), especially in the case of heavier ions, can offer improved control
probability for radioresistant tumors. In this context, Monte Carlo (MC)
particle transport and interaction methods are increasingly employed in
clinical and research institutions as vital tools to support several aspects of
beam modeling, treatment planning and quality assurance of high precision ion beam therapy.
This talk will review the role of MC methods in selected applications in
particle therapy. Drawing on own experience at different European particle
therapy facilities, the fine tuning of MC parameters for beam modeling will
be presented. In addition, based on ongoing studies and collaborations, we
will give an overview on the wide range of MC applications aiming at novel
tools for image guidance and treatment planning. These include the support to the development of heavy ion and proton computed tomography,
as well as the direct usage of MC-data in the inverse planning process,
featuring calculations of both absorbed and biologically weighted dose.
Development and validation of new solutions based on clinically established imaging modalities for adaptive strategies in particle therapy will be
also addressed, together with research efforts to support unconventional
imaging-based techniques detecting secondary radiation for in-vivo
confirmation of the actual treatment delivery. Finally, the application of
Monte Carlo tools in the emerging research area of laser driven ion acceleration for medical application will be briefly exposed.
Parts of this work have been supported by the DFG Cluster of Excellence
MAP (Munich-Centre for Advanced Photonics), the DFG Project on Ion
Radiography and Tomography, the FP7 Project ENVISION, and the BMBF
Project SPARTA.
IMAGE GUIDANCE FOR ADAPTIVE RADIOTHERAPY: IS THERE STILL A
NEED FOR SURROGATE SYSTEMS?
Torsten Moser. Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
In conformal radiation therapy, accurate and reproducible patient setup is
required. In this regard, initial setup errors, as well as day-to-day setup
variation, still poses a clinically relevant problem. The available anatomic
(„internal“) information of the patient, however, relies on the images of the
planning CT, acquired up to weeks prior to treatment and does not reflect
changes during the actual treatment. To correct in the actual situation, the
most reliable information is obtained by 3D-imaging techniques like cone
beam CT. Adaptive treatment techniques, moreover, adds a further
component to the treatment chain, the feed-back. Again by daily image
guidance, changes that occur during the treatment can be detected and
handled. Meanwhile, most linear accelerators are able to acquire images
(eg, kilovoltage/megavoltage setup images or cone beam computed tomography [CT] scans) that allow correlation of the actual patient position
with that during treatment planning CT. By the use of such image guided
radiation therapy techniques, the potential benefit for the patient has to be
weighed against the additional risk associated with the imaging dose.
For this reason, non-radiologic techniques to verify the setup position of
the patient are of great interest. As such developments, there are various
systems available that provide also information of motion and/or position.
There are devices available where electromagnetic markers have to be
implanted into the patient or technologies where other information’s are
used to generate signals that can be used for position or motion correction.
One of the latter are optical surface imaging systems. Optical surface imaging systems are able to reconstruct a 3-dimensional (3D) surface model
relative to the isocenter position. A setup correction is calculated by
registering actual images with reference images stored in the system beforehand. Although the technical accuracy of such systems has been shown
to be quite high, their suitability for clinical application depends on
additional aspects, in particular on a fixed spatial relation between the
surface and target region. To analyze this, setup corrections from a surface
imaging system were evaluated in 120 patients. As a measure of reliability,
the corrections derived by the optical system were compared with those
from 3D radiologic imaging, which is the current gold standard in image
guided radiation therapy. We found a dependence on the target region and
the used reference image modality. Therefore, additional radiologic imaging may still be necessary on a regular basis (e.g., weekly) or if the
corrections of the optical system appear implausibly large. Nevertheless,
such a combined application may help to reduce the imaging dose for the
patient.
SMALL PHOTON FIELD DOSIMETRY: PRESENT STATUS
Maria M. Aspradakis. Cantonal Hospital of Lucerne, 6000 Lucerne 16,
Switzerland
Background: IPEM report 1031 summarised existing knowledge on the
physics and challenges in the dosimetry of small MV photon fields,
reviewed available detectors for dose measurement, gave recommendations based on existing knowledge and experience, explained the need of
commissioning treatment planning systems for small field applications
and pointed out directions for future work. This presentation reports on
recent developments.
Materials and Methods: A megavoltage (MV) photon field is defined as
‘small’ when either the field size is not large enough to provide lateral
charged particle equilibrium at the point of dose measurement or the
collimating device obstructs part of the focal spot as viewed from that
point. The overlapping penubras from opposing jaws result that the full
width half maximum of the dose profile (FWHM) no longer matches the
collimator setting. Thus, the conventional defintion of field size in terms of
FWHM breaks down. The measurement of dosimetric paraments in such
non-flat narrow fields becomes a challenge because most detectors are too
large to resolve the non flat dose profile or that they perturb fluence in a
Abstracts / Physica Medica 30S1 (2014)
way that using available perturbation factors is not appropriate. Furthermore, changes in energy spectrum with field size, the fact that on some
modern radiotherapy equipment conventional reference conditions
cannot be realised or that the flattening filter is not present, means that
current dosimetry codes of practice do not provide recommendations for
dosimetry in such fields.
Results & Discussion: The new formalism for dose determination in small
and non-standard photon fields developed by the IAEA/AAPM is
explained2. Some results on detector-specific beam quality corrections
factors are presented.
References
1. Aspradakis, M.M., Byrne, J. P., Palmans, H., Conway, J., Rosser, K., Warrington, A. P., Duane, S. IPEM report 103: 'Small Field MV Photon Dosimetry'.
2010, York, UK: Institute of Physics and Engineering in Medicine (IPEM).
ISBN 978 1 903613 45 0
2. Palmans, H, Dosimetry of small fields: Present status and future guidelines
by IAEA, Radiotherapy & Oncology, Vol 111, Supp 1, April 2014, ISSN 01678140
MEDICAL PHYSICS CHALLENGES WITHIN THE MICROBEAM RADIATION
THERAPY (MRT) PROJECT
€uer-Krisch a, f, C. Nemoz a, f, T. Brochard a, f, M. Renier a, f, H.
E. Bra
Requardt a, f, R. Serduc b,f, G. LeDuc a, f, A. Bravin a, f, S. Bartzsch c, f, P.
Fournier d, a, f, I. Cornelius d, f, P. Berkvens a, f, J.C. Crosbie d, f, M.L.F.
Lerch d, f, A.B. Rosenfeld d, f, M. Donzelli a, c, f, U.Oelfke c, f, A. Bouchet e, f, H.
Blattmann g, f, B. Kaser-Hotz h, f, J.A. Laissue i, f. aEuropean Synchrotron
Radiation Facility, B.P.220, F-38043 Grenoble Cedex, France; bINSERM unit
836, CHU Grenoble, Grenoble, France; cIm Neuenheimer Feld 280,69120
Heidelberg,Germany; dCMRP, Northfields Ave., Wollongong, 2500, NSW,
€t Bern Institut für Anatomie Baltzerstrasse 2CH-3000
Australia; eUniversita
Bern 9, Switzerland; f CHU Grenoble, Grenoble, France; gNiederwiesstr. 13c
5417 Untersiggenthal, Switzerland; hAnimal Oncology and Imaging Center,
Rothusstr. 2, CH-6331 Huenenberg/CH,.Switzerland; iUniversity of Bern
,Faculty of Medicine, Murtenstrasse 11, CH-3010 Bern, Switzerland
Background: Microbeam Radiation Therapy (MRT) uses a spatially fractionated filtered white X-ray beam from a high energy wiggler Synchrotron Source (energies 50-350keV) with extremely high dose rates (up to
about 20kGy/s). The typical planar beam width in an array is 25-100mm
with 100-400mm wide spaces between beams. Such beams are very well
tolerated by the tissue, even the high “peak” doses delivered in the path of
the microbeams, when respecting a dose prescription in the “valley’ that
corresponds to a dose used of conventional Radiation Therapy (RT) converted to a single exposure . The superior tumor control when compared to
that realized by conventional RT is achieved by differential effects of MRT
on the normal tissue vasculature versus the tumor vasculature.
Materials and Methods: The MRT technique has been technically set up,
tested and successfully applied during the last 20 years on various tumor
models. Presently, the project is mature enough to be used for the treatment of spontaneous tumors in pets. Unified efforts from several teams
with very different expertise now permit Microbeam Radiation Therapy in
animal patients with a high degree of safety, in pursuit of the ultimate goal
of clinical applications in humans.
Results: The MRT trials for animal pets as tumor patients required substantial work for developing, upgrading and progressively implementing
instrumentation, dosimetry protocol, as well as the crucial patient safety
systems. Progress on the homogenous dose measurements using ionisation chambers and Alanine dosimetry as well as the comparison of high
resolution dosimeters with the dose calculations based on a novel tumor
planning system will be summarized. A general overview on the different
achievements will be presented as well as a vision for possible human
trials.
TEXTURE AS IMAGING BIOMARKER
Costaridou Lena. Department of Medical Physics, School of Medicine,
University of Patras, Rion Patras 26504, Greece
Quantitative image analysis involves derivation of quantitative measures
(extraction of image features), aiming to capture image manifestations of
5
underlying pathophysiological processes, with the ultimate goal to identify
image-based biomarkers and improve patient-specific disease management. While features capturing lesion contrast and shape, also mimicking
radiologists’ used image attributes, have been extensively studied in the
framework of image-based computer aided diagnosis texture analysis, not
directly intuitive to radiologists, is an emerging approach. In addition, the
tissue appearance modeling and classification task has been recently
enriched, encompassing tasks, such as prognosis, monitoring disease
progression and response to therapy, as well as cancer risk assessment.
Prognosis imaging biomarkers assess neoplasm aggressiveness, in terms of
their relationship to pathology and molecular classification, while treatment response imaging biomarkers could help early identification of responders/non responders to neo-adjuvant chemotherapy schemes prior to
surgical decisions. In this review, texture analysis methodologies exploited
towards the identification of potential imaging biomarkers will be
considered. Representative texture analysis approaches will be reviewed
across imaging modalities, with reference to methodological and technological aspects and challenges. The advent of multimodality imaging with
near isotropic 3-dimensional spatial resolution modalities, including
anatomical and functional modalities, is expected to enhance characterization and quantification of naturally occurring textures, as well as their
scale and orientation properties, while casting insight to texture dynamics,
provided by imaging tissue volume times series (spatiotemporal data).
TECHNICAL CHALLENGES AND CLINICAL RESEARCH APPLICATIONS OF
ULTRAHIGH FIELD MRI
Andrew Webb. Leiden University Medical Center, Radiology Department, The
Netherlands
With the rapid spread of 7 Tesla whole body MRI systems throughout the
world there has been significant recent progress in both clinical and
clinical research applications. Although predominantly in the neurological
area, there have also been many developments in the areas of musculoskeletal, cardiac and ocular imaging. Increased magnetic susceptibility
contrast, enhanced magnetic resonance angiography, and much higher
signal-to-noise in spectroscopy and heteronuclear imaging/spectroscopy
have been the driving forces for much of this progress. The major challenges have been, and continue to be, increased image inhomogeneity,
power deposition, and motion-induced artifacts. Many hardware advances
have already been necessary to deal with these problems, and many future
advances are required to keep the field moving forward.
Examples which will be presented include: (i) the use of navigator echoes
and phase imaging for high resolution MRI in Alzheimers patients, (ii) the
use of high dielectric materials to improve neuroimaging and spectroscopy
at high field, (iii) diffusion weighted metabolite spectroscopy in the brain,
(iv) high field cardiac and musculoskeletal imaging, and (v) the design of
new types of RF coil specifically for high field.
DOSIMETRY IN SUPPORT OF PATIENT PROTECTION IN DIAGNOSTIC
RADIOLOGY - A VALEDICTORY VIEW FROM THE UK
Dr Paul C. Shrimpton. Formerly Leader of Medical Dosimetry Group, Public
Health England, Chilton, OX11 0RQ, UK
Invited lecture in relation to EFOMP Medal Award Ceremony
The increasingly widespread use of x-rays in diagnostic radiology provides
not only enormous benefits to patients, but also significant radiation
exposure for populations. The protection of patients against potential radiation harm requires the elimination of all unnecessary x-ray exposure in
relation to effective clinical diagnosis. Dosimetry is an essential management tool for patient safety by allowing the assessment of typical radiation
risks in support of the justification of procedures, and the routine monitoring and comparison of typical doses in pursuit of the optimisation of
patient protection. Periodic assessment of patient doses should form an
integral part of quality assurance in x-ray departments and is best based on
practical measurements that provide useful characterisation of patient
exposure, such as entrance surface dose, dose-area product and, for CT,
volume-weighted CT dose index and dose-length product. Mean values
determined in a department for these practical dose monitoring quantities, from patient samples for each type of examination and patient group,
6
Abstracts / Physica Medica 30S1 (2014)
can form the basis not only for estimates of typical organ and effective
doses to reference patients utilising appropriate coefficients, but also local
diagnostic reference levels (DRLs). DRLs represent a pragmatic mechanism
for promoting continuing improvement in performance by facilitating
comparison with national values and practice elsewhere. The development
and application of DRLs in the UK over the last 30 years, within a coherent
framework for patient protection that has included periodic national
surveys for conventional x-rays and CT, has successfully helped reduce
unnecessary exposures, with national DRLs for many examinations having
fallen by a factor 2.
HOW TO OPTIMIZE EXPOSURES USING RADIOBIOLOGY AS A GUIDE
Klaus Trott, Vere Smyth, Andrea Ottolenghi. Department of Physics,
University of Pavia, Via Bassi 6, 27100, Pavia, Italy
Medical radiation exposures associated with the diagnosis and treatment
of diseases are, besides natural background irradiation, the main source of
radiation burden to mankind and may lead to an increased risk of various
diseases such as cancer, cardiovascular diseases, developmental disorders
and heritable health injury. Concepts for radiation risk estimation and
reduction were developed by ICRP, yet they do not apply to individual
patients but to the population at large. They are designed to be used as
guidelines for planning “safe” procedures e.g. in industry and public
health. Population risk estimates are based on mean doses to a list of
“critical” organs and on tissue weighting factors. The estimation of radiation risks for individual patients, however, has to be based on the determination of anatomical dose distribution within the exposed organs e
mean doses may be meaningless. Even within the same organ, pathology,
pathophysiology and pathogenesis differ between different potential
health complications from medical radiation exposures of the different
organs. They depend on dose to critical structures and subvolumes, on age
and sex of the exposed patient and most likely also on genetic predisposition and life style factors. Both, for diagnostic exposures and therapeutic
exposures of the individual patient, estimations of health risks need to be
based on radiobiological mechanisms of pathogenic pathways. Models of
risk estimation in particular those from therapeutic exposures are not
specific for particular organs but for particular clinical manifestation of
radiation-induced disorders and diseases. Moreover, dose volume histograms are of little value in these estimates since anatomy is more important than volume. Several exposure scenarios in diagnostic and therapeutic
radiology will be discussed to explain the problems and suggest possibilities to solve the problems.
Acknowledgments. This work was partially funded by EU (EC Contract FP7
605298, ‘EUTEMPE-RX’).
Badly written papers, not complying with requirements and including
mistakes, eg in references, immediately give the impression that the work
may also be poor. Work with experienced authors initially (eg supervisor).
Look critically at papers you read and note what you think works well. New
writers can learn good practice by example. Good luck!
REASONS FOR REJECTION
di Napoli Federico II, Naples, Italy
Paolo Russo. Universita
Rejection of a paper refers to the decision of the Editor of a scientific
Journal not to accept the submitted manuscript for publication in that
Journal. This condition may occur in any phase of the paper evaluation
process, but mostly occurs at the end of the first round of the peer-review
process, i.e. when one of two experts, asked for their independent
opinion, suggest reasons for acceptance, revision or rejection of the
manuscript. Typically, in the case of a negative peer-review, the Associate
Editor expresses a recommendation (e.g., reject) for the Editor-in-Chief,
who takes the final decision. The rejection rate of a Journal, i.e. the ratio of
the number of rejected to the number of evaluated manuscripts, has been
seen to increase over the last years in many well-reputed scientific
Journals, also in the case of medical physics Journals, and this has caused
concern both in the Journal's Editorial Boards, and in the authors' community. For example, for the Journal Physica Medica (European Journal of
Medical Physics, EJMP) the rejection rate is such that only about one
manuscript out of three is accepted for publication. This has then
prompted various actions from scientific Publishers and Journal Editors,
in order to increase the awareness of the authors toward the scientific
writing best practice, the peer-review process and the Journals' whole
paper evaluation process. This presentation, by the Editor-in-Chief of
EJMP, indicates possible reasons for paper rejection, based on the presenter's experience as an author, as a reviewer, as Associate Editor and as
Editor of a scientific Journal in medical physics. These reasons may
include lack of proper English writing, lack of motivations or originality,
weaknesses in the methodological aspects or in the significance of the
findings and other specific reasons, which overall may indicate a general
lack of convincing strength of the manuscript. Since publishing in a wellreputed scientific Journal is a competition for the acquisition of the
consensus in the Journal's audience, and hence in the corresponding
scientific community, toward the work carried out in the specific study,
lack of strength of a manuscript for one or more of the above reasons invariably leads to paper rejection. Ultimately, the efforts by the scientific
community toward reaching the best practice in scientific writing and
evaluation, will hopefully produce a reduced Journals' rejection rate, and
most importantly, an improved efficacy of the research work, for the
benefit of the scientific and social progess.
HOW TO PUBLISH A PAPER IN A PEER-REVIEWED JOURNAL
THE CURRENT STATUS OF MEDICAL PHYSICS RECOGNITION IN EUROPE
David Thwaites. Institute of Medical Physics, School of Physics, University of
Sydney, NSW2006, Australia
Publication of work is necessary to move the field forward. Using experience as an author, reviewer, editorial board member and editor, some
observations are summarized on writing a paper, submitting it and getting
it published, focussing on what makes a good paper and hence likely to be
acceptable.
First, consider your main message and hence material selection and writing
flow so that this is clear. Make the introduction relevant to where the work
fits into current related research, going quickly from generalities to specifics. Even good well-presented work will not get into high-impact-factor
journals unless it is clearly novel and/or significant. Methods should allow
the work to be repeated; ask yourself if they are clear and complete. Explain
acronyms. Results should clearly tie figures and tables to text. Conclusions
should relate back to the key message and be verifiably supported by results. Discussion and conclusions should not just be re-stated results!
Ask a colleague, unconnected with the work, to read the ‘final’ draft paper
and give comments on clarity. If they can't understand it, neither will the
referees! Re-read it yourself after a time gap. Check journal requirements
and comply! Hastily prepared submissions are usually poorly prepared!
Stelios Christofides. Medical Physics Department, Nicosia General Hospital,
Nicosia, Cyprus
The European Union recognises professions automatically if they meet the
requirements of Directive 2005/36/EC [1], as this was amended by Directive 2013/55/EU [2]. Automatic profession recognition gives the right of
professionals to move and work without any restrictions in any Member
State of the European Union.
European recognition of the Medical Physics profession will allow Clinically Qualified Medical Physicists (CQMP) the same privileges as other
recognised professions, such as Medical Doctors, Architects, Nurses, etc.
Furthermore, Medical Physics Experts (MPE), as defined by Directive 2013/
59/Euratom [3, 4], can have the same privileges, if are recognised by all the
Competent Authorities of all the Member States of the European Union.
Currently, neither the CQMPs nor the MPs are recognised automatically as
a profession by all the Member States of the European Union. The European Federation of Organisations for Medical Physics (EFOMP) is working
for many years in developing the education, training and competence of
Medical Physicists, both at the CQMP and MPE levels so as the
Abstracts / Physica Medica 30S1 (2014)
7
requirements of the above Directives are met for automatic professional
recognition.
The purpose of this presentation is to give a brief account of the efforts
made by EFOMP and the requirements that need to be met, at the national
level, in order for both the CQMPs and MPEs can be automatically recognised by the European Union.
References
[1] Directive 2005/36/EC of the European Parliament and of the Council of
7 September 2005 on the recognition of professional qualifications, OJ
L255, 30.9.2005, pp 22-142.
[2] Directive 2013/55/EU of the European Parliament and of the Council of
20 November 2013 amending Directive 2005/36/EC on the recognition of
professional qualifications and Regulation (EU) No 1024/2012 on administrative cooperation through the Internal Market Information System (‘the
IMI Regulation’), OJ L354, 28.12.2013, pp 132-170.
[3] Council Directive 2013/59/Euratom of 5 December 2013 laying down
basic safety standards for protection against the dangers arising from
exposure to ionising radiation, and repealing Directives 89/618/Euratom,
90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom,
OJ L13, 17.1.2014, pp. 1-73.
[4] European Commission, Radiation Protection Report 174, “Guidelines on
Medical Physics Expert”, Directorate-General Energy, Luxembourg, 2014,
available from: http://ec.europa.eu/energy/nuclear/radiation_protection/
doc/publication/174.pdf (last accessed on the 11th of May 2014).
continuous and fast, increasing the demand for high level scientists and
experts in the field. To ensure that ionizing radiation is safely used, the
presence of the medical physicist is essential. The medical physicist has
therefore become part of an indispensable “core team” within the hospital
to ensure safe and proficient use of medical equipment. His presence is
growing also within the industry and/or regulatory authority environment.
In order to meet all these demands, sufficient education and training is
indispensable. Collaboration and innovation in this field is imperative for
the appropriate professional response to all these challenges. The European Commission has for a number of years recognized the need for
adequate theoretical and practical training of medical physicists for the
purpose of radiological practices. This is clearly stated in a number of
European directives as well as in the latest European Basic Safety Standards. A number of questions arise based on all these facts. Do we have
sufficient number of adequately trained medical physicists or medical
physics experts to address the needs of the increasing number of medical
procedures in Europe? Is the education and training of such scientists
harmonized across Europe, that will facilitate in easier and mutual
recognition as well as improved cross-border mobility of medical physicists? The present paper will attempt to answer these questions using the
most recent information within Europe.
THE CURRENT STATUS OF MEDICAL PHYSICS RECOGNITION IN THE
MIDDLE EAST
Lama Sakhnini. Department of Physics, College of Science, University of
Bahrain, Sakhir, PO. Box 32038, Kingdom of Bahrain
Ibrahim Duhaini. Chief Medical Physicist & RSO, Rafik Hariri University
Hospital, Beirut - Lebanon & President of the Middle East Federation of
Organizations of Medical Physicists (MEFOMP), Lebanon
Education: The Department of Physics at University of Bahrain offers a B.Sc.
in medical physics program. The program produces B.Sc. degree graduates
with a broad knowledge of fundamental and applied physics. With a
specialization in medical physics, the graduates will be eligible for
employment in hospitals, clinics, environmental establishments or industrial health care centers. Students should also be suitably prepared to carry
out research in medical physics leading to a higher degree. The B.Sc. in
Medical Physics degrees gives the opportunity to study the many medical
applications of advanced physics. Medical physics courses, taught by staff of
the department of Physics, are supplemented by specialist lectures given by
senior practicing medical physicists and doctors from Salmaniya medical
complex and Bahrain Defense force hospital. The B.Sc. programs in Medical
Physics shares many common courses with the B.Sc. program in Physics,
but nearly 48 credit hours include courses which are specific to Medical
Physics program. A total of 42 female students graduated from the program
so far, only 3 students managed to get jobs in the medical sector.
Training: The B.Sc. in Medical Physics program ensures that the students
go through clinical training at hospitals in the Kingdom of Bahrain or in the
Kingdom of Saudi Arabia. In an ideal situation; the student spends a
minimum of 2 months of hospital training to complete a clinical rotation in
radiation therapy, diagnostic imaging and nuclear medicine. The student
observes and practices clinical procedures under the direct supervision of
a senior clinical medical physicist. The student is required to write a
progress report on the clinical procedures. However there is no well
designed training program in the hospitals. Hence there is a disparate need
for a “Residency Program” which is aimed at both educating and providing
practical experience so that the medical physicist would be ready to
practice in a hospital setting and obtain board certification. Training for our
students faced many challenges, as most hospitals do not have medical
physicists, most hospital administrators do not know the rule of medical
physicists, many hospitals have no quality management program and rely
on the medical supplier of their equipment to do yearly maintenance.
Medical physics is the branch of physics concerned with the application of
physics to medicine, particularly in the diagnosis and treatment of human
diseases. From the time when Wilhelm Roentgen and other physicists made
the discoveries which led to the development of Diagnostic Radiology,
Radiotherapy, Brachytherapy and Nuclear Medicine, Medical Physicists
have played a pivotal role in the development of new technologies that
have revolutionized the way medicine is practiced. In today's health care
scene, the medical physicist is essential to the safe and cost effective
operation of any creditable medical institution.
Medical Physics in the Middle East Region has passed in different stages. In
particular the ISEP Conference held in Bahrain in November 2007 and the
16 th ICMP Conference held in Dubai in 2008. During these conferences,
there were several meetings for all the medical physics societies in the
Middle East. The result was the establishment in September 2009 of the
Middle East Federation of Organizations in Medical Physics (MEFOMP)
which is part of the International Organization of Medical Physics IOMP.
The following countries have signed up for this chapter: Bahrain, Iran, Iraq,
Jordan, KSA, Lebanon, Oman, Qatar, Syria, UAE and Yemen. Ever since then,
the medical physics profession has gone the first mile in the road of
recognition in most of the ME countries. Governmental entities and University bodies started looking deeply into the need of promoting MP activities across the region.
Now, Medical physicists in the ME region are considered scientists who
through science are able to identify problems and unveil deficiencies. It is
also through science that they solve the problems and correct the deficiencies encountered in the diagnosis and treatment of diseases.
There will be exciting and difficult challenges not only in the field of health
care but also in the race for nuclear power in the ME region. Countries will
be counting on the science of Medical Physics to help meet these
challenges.
Keywords: IOMP, MEFOMP, Middle East, Medical Physics, Recognition.
EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN EUROPE
V. Tsapaki. Konstantopoulio General Hospital, Athens, Greece
Background: Medical exposure represents the utmost and fastest growing
contribution to manmade radiation exposure not only in Europe but also
across the world. Furthermore, the evolution of medical equipment is
EDUCATION AND TRAINING OF MEDICAL PHYSICISTS IN MIDDLE EAST
KINGDOM OF BAHRAIN AS AN EXAMPLE
EDUCATIONAL
IMPORTANT?
ACCREDITATION
IN
MEDICAL
PHYSICS:
IS
IT
John Damilakis. Professor of Medical Physics, Greece
An increasing number of higher education institutions have in recent years
started to offer courses on Medical Physics. Moreover, Continuing Professional Development (CPD) for medical physicists is of great professional
interest. CPD courses is an excellent way to ensure that Medical Physicists
8
Abstracts / Physica Medica 30S1 (2014)
become knowledgeable about all current issues in their field and to provide the necessary knowledge, skills and competences for certified Medical Physicists to become Medical Physics Experts. However, external
assessment of the quality of education or training provision is needed.
Accreditation is the formal recognition that education and training on
medical physics provided by an institution meets acceptable levels of
quality. Accreditation should be based upon standards and guidelines.
Requirements for accreditation of a training programme should take into
account several aspects including facilities, staff, educational material and
teaching methods. In Europe, ENQA (European Network for Quality
Assurance) promotes European co-operation in the field of Quality
Assurance in higher education. ENQA members are national agencies and
organizations, which play a major role in the accreditation process. A European organization is needed to offer accreditation of medical physics
CPD and training programs. Certification is the recognition of knowledge of
a professional who has completed his/her education or training. The EC has
developed tools and frameworks to promote training and facilitate
mobility. ECVET is a European system of accumulation and transfer of
credits designed for vocational education and training in Europe.
IMAGE-GUIDED RADIATION THERAPY IN THE PRECLINICAL SETTING
Ross Berbeco PhD. Department of Radiation Oncology, Brigham and
Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical
School, USA
Current clinical radiation therapy is delivered with multiple collimated
beams and accurate radiation dose calculation based on CT imaging.
Additional advances in image-guided delivery techniques have saturated a
majority of modern clinics. Therefore, modern translational research of
radiation biology and radiation physics using in vivo models of cancer requires a preclinical therapy platform that has the same capabilities as
modern clinical linear accelerators. In 2010, we established a preclinical
radiation biophysics laboratory at the Dana-Farber Cancer Institute and
Harvard Medical School (Boston, MA USA). The cornerstone of this facility is
a Small Animal Radiation Research Platform (SARRP) which was developed
by researchers at Johns Hopkins University (Baltimore, MD USA) and
commercialized by Xtrahl, Inc. (Surrey, UK). The SARRP combines a conventional x-ray tube with brass collimators to enable delivery of photon
beams as narrow as 0.5 mm at 220 kVp. Precise (sub-mm) image-guided
setup is performed using cone-beam CT imaging combined with a robotic
motion stage. Absolute dose output is measured with an ADCL-traceable
ion chamber. Percentage depth-dose and beam profiles are measured for
each collimator with EBT3 film. Monte Carlo modeling of the SARRP is
performed using EGSnrc. The phase space files are used in a GPU-driven 3D
dose calculation engine with the 3D Slicer platform for visualization
(Brigham and Women’s Hospital Surgical Planning Laboratory, Boston, MA
USA). Collimator size, gantry and collimator angles, and target prescription
are given and a 3D isodose distribution is calculated. Measurements in
heterogeneous media have validated the dose calculation accuracy. Routine
quality assurance procedures have been developed, based on those
employed for clinical radiation devices. The laboratory has facilities for
animal surgery, housing, anesthesia and injection. Our SARRP has been
outfitted with a tube for continuous isoflurane delivery during imaging and
therapy procedures. To date, more than 1,000 preclinical procedures on live
animals have been performed in the laboratory. Examples of current
translational research applications include genetic dependence of radiation
resistance, chemical radiation sensitizers, metabolic modifiers of radiation
therapy efficacy, metallic nanoparticles for enhanced radiation therapy and
imaging contrast, and dermatologic studies. We anticipate that by utilizing
a research instrument that provides accurate and precise radiation delivery,
the results will have high translational relevance. Funding for these projects has come from the United States Department of Defense, the National
Institutes of Health, philanthropic foundations and internal sources.
THE GEANT4-DNA PROJECT: OVERVIEW AND STATUS
bastien Incerti. CNRS, Bordeaux University, France
Se
On behalf of the Geant4-DNA collaboration
Understanding and prediction of adverse effects of ionizing radiation at
the cellular and sub-cellular scale remains a challenge of today’s radiobiology research. In this context, a large experimental and modeling activity
is currently taking place, aimed at better understanding the biological
effects of ionizing radiation at the sub-cellular scale. The “Geant4-DNA”
project was initiated by the European Space Agency [1]. It aims to develop
an experimentally validated simulation platform for the modeling of early
DNA damage induced by ionizing radiation, using modern computing tools
and techniques. The platform is based on the general-purpose and opensource “Geant4” Monte Carlo simulation toolkit, and benefits from the
toolkit’s full transparency and free availability [2].
This project proposes to develop specific functionalities in Geant4
allowing:
1) The modeling of elementary physical interactions between ionizing
particles and biological media, during the so-called “physical” stage.
2) The modeling of the “physico-chemical and chemical” stages corresponding to the production, the diffusion and the chemical reactions
occurring between chemical species. During the “physico-chemical” stage,
the water molecules that have been excited and ionized during the physics
stage may de-excite and dissociate into initial water radiolysis products. In
the “chemical stage”, these chemical species diffuse in the medium surrounding the DNA. They may eventually react among themselves or with
the DNA molecule.
3) The introduction of detailed biological target geometry models, where
the two above stages are combined with a geometrical description of
biological targets (such as chromatin segments, cell nuclei…). The Geant4DNA physics processes and models are fully integrated into the Geant4
toolkit and can be combined with Geant4 geometry modeling capabilities.
In particular, it becomes possible to implement the geometry of biological
targets with a high resolution at the sub-micrometer scale and fully track
particles within these geometries using the Geant4-DNA physics processes. These geometries represent a significant improvement of the
geometrical models used so far for dosimetry studies with the Geant4
toolkit at the biological cell scale.
The current status of the project will be presented, as well as on-going
developments.
[1] S. Incerti et al., “Comparison of Geant4 very low energy cross section
models with experimental data in water“ , Med. Phys. 37, 4692-4708 (2010)
[2] S. Agostinelli et al., “Geant4-a simulation toolkit”, Nucl. Instrum.
Methods. Phys. Res. A. 506, 250-303 (2003)
FIELD-CYCLING MRI: A NEW IMAGING MODALITY?
David J. Lurie, Lionel M. Broche, Gareth R. Davies, Nicholas Payne,
Kerrin J. Pine, P. James Ross, Vasileios Zampetoulas. Aberdeen Biomedical
Imaging Centre, University of Aberdeen, AB25 2ZD, Scotland, UK
Much of the contrast in conventional MRI arises from differences in the
NMR relaxation times, especially the spin-lattice relaxation time, T-1. It is
also well known, from in vitro measurements on small tissue samples, that
the variation of T1 with the strength of the applied magnetic field B0
(known as T-1-dispersion) is tissue-dependent, and that the shape of a
tissue’s T-1-dispersion curve is altered in disease. However, T-1-dispersion
is invisible to conventional MRI scanners, because each scanner can only
operate at its own native magnetic field (e.g. 1.5 T, 3.0 T). The aim of our
work is to exploit T-1-dispersion as a new MRI contrast mechanism, by
building new types of MRI scanner which make use of Fast Field-Cycling
(FFC) [1].
In FFC, the applied magnetic field is switched rapidly, while the sample (or
patient) is inside the scanner. Thus, the nuclear magnetisation can be made
to evolve at a range of magnetic field strengths, allowing the measurement
of T-1-dispersion. The magnetic field is always switched to the same value
prior to measurement of the NMR signals, so that the instrument’s radiofrequency system does not require retuning during the procedure.
In our laboratory we have built two whole-body human sized FFC-MRI
scanners, one of which makes use of a dual magnet in order to achieve field
switching [1,2]. The detection field of 59 mT is provided by a vertical-field,
permanent magnet. Inside its bore is located a resistive magnet which
generates an opposing magnetic field; field-cycling is achieved by
switching the current in the resistive magnet coil.
Abstracts / Physica Medica 30S1 (2014)
We have begun to explore bio-medical applications of FFC-MRI, and early
results have shown promise in the areas of thrombosis [3] and in osteoarthritis [4], where the technique seems to be an indicator of early diseaserelated changes. FFC-MRI is showing significant potential as a new variant
of MRI. Please consult our web site (www.ffc-mri.org) for further
information.
[1] Lurie D.J., Aime S., et al., Comptes Rendus Physique 11, 136-148 (2010).
[2] Lurie D.J., Foster M.A., et al., Phys.Med.Biol. 43, 1877-1886 (1998).
[3] Broche L.M., Ismail S. et al., Magn.Reson.Med., 67, 1453e1457 (2012).
[4] Broche L.M., Ashcroft G.P and Lurie D.J., Magn.Reson.Med. 68, 358-362
(2012).
STANDARDS FOR MRT DOSIMETRY: THE METROMRT PROJECT
Christophe
Bobin b,
Lena
Johansson a,
Leila
Vere
Smyth a,
Marco
D’Arienzo d, e,
Marco
Capogni d,
Hans
Joulaeizadeh c,
g a
. National Physical Laboratory NPL,
Rabus f, Maurice Cox a, Jaroslav Solc
Hampton Road, Teddington, Middlesex, TW11 0LW, UK; bCommissariat a
l’Energie Atomique (CEA) Bt 476, Pt Courrier 142, CEA-Saclay, FR-91191 Gifsur-Yvette Cedex, France; cVSL, Dutch Metrology Institute, Thijsseweg 11,
P.O. Box 654, NL-2629, JA Delft, Netherlands; dNational Institute of Ionizing
Radiation Metrology, ENEA-INMRI, C.R. Casaccia, 00123 Rome, Italy;
e
Department of Human Anatomy, Histology, Forensic Medicine and
Orthopedics, Sapienza University of Rome, Via Borelli 50, 00161 Rome,
Italy; fPhysikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, D38116 Braunschweig, Germany; gCzech Metrology Institute (CMI),
Inspectorate for Ionising Radiation, Radiova 1, CZ-102 00 Prague 10,
Czech Republic
The outcome for the patient of a molecular radiotherapy (MRT) procedure
is determined by the radiation doses to the target tissue, and to critical
normal tissue. It is well known that there is a wide variation between
individual patients in these doses for the same administered radiopharmaceutical activity. Generally a patient is given the maximum activity that
will be tolerated by the normal tissue, on the basis of average population
statistics obtained during clinical trials, in the hope that an effective
treatment dose will be received. This practice could clearly be optimised if
the respective doses could be determined for each patient, and the prescription based on this knowledge. Many clinical research centres are
developing dosimetry methods of increasing sophistication and accuracy,
but to date these developments have very rarely had any effect on individual patient management. There are many reasons why this is so, but the
obvious difference between MRT and other radiotherapy modalities is the
absence of a standard, internationally endorsed dosimetry protocol.
Development of a dosimetry protocol analogous to the IAEA TRS398 protocol (Absorbed dose determination in external beam radiotherapy, IAEA,
Vienna, 2000) is difficult because of the complex nature of the steps in the
MRT dosimetry process and dependence on the radiopharmaceutical being used. However, difficult does not imply impossible. An international
project funded under the European Metrology Research Programme,
MetroMRT (http://projects.npl.co.uk/metromrt/), is currently making
progress in addressing this problem. The dosimetry process is analysed
into its component parts: activity measurement, quantitative imaging (QI),
activity-time integration, and dose calculation, from which a measurement
chain is constructed, traceable to primary radiation standards of radioactivity and absorbed dose, with an evaluated uncertainty. The greatest
difficulties are relating a standard QI calibration to a measurement on a
patient, and accounting for the uncertainty resulting from the combination
of different biokinetics, measurement time points, and integration
methods in determining the uncertainty in the activity-time integration
step. The MetroMRT project is in the final year of its 3-year duration. Details of the individual tasks and success achieved so far will be presented.
RADIOPHARMACEUTICAL DOSIMETRY: FROM THE ANIMALS TO THE
CLINICS
s. UMR 1037 INSERM/UPS, Centre de Recherche en
Manuel Bardie
Canc
erologie de Toulouse, Toulouse, France
Nuclear Medicine dosimetry is not limited to the clinical scale (i.e. organ or
tumor).
9
Preclinical studies, involving animal (or cell experiments) also can benefit
from sound dosimetric studies. Small animal studies are required during
the development of new radiopharmaceuticals (diagnostics or therapy).
The general relevance of radiopharmaceutical dosimetry applies equally to
preclinical and clinical studies. The MIRD scheme can most often be
applied, even at the cellular level, as long as macrodosimetric parameters
(mean absorbed doses) remain relevant.
However, there are differences in the goals and in the methodology
required to perform studies:
For diagnostic tracers, during the development phase, small-animal
radiopharmaceutical biodistribution and pharmacokinetics are frequently
extrapolated to humans. However, absorbed dose delivered are usually not
considered.
For therapeutic nuclear medicine, absorbed doses are computed to document the biological effect observed (efficacy/therapy), and that can be
performed in a preclinical context. As for clinical dosimetry, the issue of
“model” versus “specific” dosimetry must be addressed.
Cumulated activity is most often determined from organ/tissues activity
measurements at different time points, from ex vivo counting.
Absorbed dose calculation can be carried out with more or less sophisticated radiation transport codes.The table below presents the various
possibilities offered to perform nuclear medicine dosimetry at the clinical
scale. How that table can be extrapolated in a context of preclinical
dosimetry will be discussed.
Context
Cumulated
activity (Bq.s)
S values
(Gy.Bq-1.s-1)
Absorbed
dose (Gy)
Diagnostics
Therapy
Therapy
Model
Specific
Specific
Model
Model ± adjusted
Specific
Model-based
Model-based ± realistic
Specific
Within multidisciplinary teams involved in radiopharmaceutical research, physicists should not only focus on the clinical aspects but also participate to preclinical
studies.
ACQUISITION PROTOCOLS FOR 18F-FDG WHOLE BODY
OPTIMIZING SCAN DURATION VERSUS ADMINISTERED DOSE
PET/CT:
Marco Brambilla. Medical Physics Department, University Hospital Of
Novara, Novara, Italy
Aim: The aim of this presentation is to describe the way in which contrastto-noise ratio (CNR)) behave when varying acquisition parameters (such as
emission scan duration (ESD) or activity at the start of acquisition (Aacq))
that in clinical practice can be selected by the user, or object properties
(such as target dimensions, target-to-background (T/B) ratio and activity
outside the field of view) which depends uniquely on the intrinsic characteristics of the object being imaged.
Methods and Results: In the first experiment CNR was studied as a
function of ESD and Aacq for different target sizes and T/B ratios using a
multivariate approach in a wide range of conditions approaching the ones
that can be encountered in clinical practice. Sequential imaging was performed to acquire PET images with varying background activity concentrations of about 12, 9, 6.4, 5.3 and 3.1 kBq/mL. The ESD was set to 1, 2, 3,
and 4 min/bed. The ESD resulted as the most significant predictor of CNR
variance, followed by T/B ratio and the cross sectional area of the given
sphere. Only last comes Aacq with a weight halved with respect to ESD.
Thus, raising ESD seems to be much more effective than raising Aacq in
order to obtain higher CNR.
In the second experiment a scatter phantom was positioned at the end of
the modified IEC phantom to simulate an activity that extends beyond the
scanner. The modified IEC phantom was filled with 18F (11 kBq/mL) and the
spherical targets had a target-to-background ratio of 10. PET images were
acquired with background activity concentrations into the FOV (Ac,bkg)
about 11, 9.2, 6.6, 5.2 and 3.5 kBq/mL. ESD was set to 1, 2, 3, and 4 min. The
tube inside the scatter phantom was filled with activities to provide an
Ac,out in the whole scatter phantom of zero, half, unity, twofold and fourfold the one of the modified IEC phantom. CNR diminishes significantly
with increasing outside FOV activity, in the range explored. ESD and Ac,out
have a similar weight in accounting for CNR variance. A recovery of CNR
loss due to an elevated Ac,out activity seems feasible by modulating the ESD
in individual bed positions according to the Ac,out.
10
Abstracts / Physica Medica 30S1 (2014)
Conclusions: The European Association of Nuclear Medicine procedure
guidelines for whole-body FDG-PET scanning still prescribe a dose proportional to the patient’s body mass. However, clinical practice and
experimental evidences show that using an FDG dose proportional to body
mass does not overcome size-related degradation of the image quality and
different algorithms should be devised instead.
NEW ANALYTICAL ALGORITHMS FOR PET AND SPECT
George Kastis. Academy of Athens, Medical & Biological Research Foundation
(IIBEAA), Athens, Greece
Positron emission tomography (PET) and single-photon emission
computed tomography (SPECT) are the most important nuclear medicine
imaging modalities that measure the in vivo distribution of imaging
agents labeled with emitting radionuclides. Image reconstruction is an
essential component of both modalities, allowing tomographic images to
be obtained from a set of two-dimensional of three-dimensional projection data. The existing image reconstruction methods can be classified
into two main categories: analytical methods and iterative (or statistical)
methods.
Filtered backprojection (FBP) is the predominant analytic reconstruction
method. Its mathematical formulation is based on the inversion of the
Radon transform through the central slice theorem. The main advantages
of FBP are speed and simplicity. However, in FBP it is difficult to incorporate
complex physical phenomena such as attenuation and scatter. The predominant iterative algorithms are the maximum-likelihood expectationmaximization (MLEM) algorithm and its accelerated successor the ordered-subsets expectation-maximization (OSEM) algorithm. The main
advantage of the iterative algorithms is the ability to model several aspects
of the imaging system, including elements of the noise characteristics,
sinogram blurring due to detector crystal penetration, depth of interaction,
photon scatter, and attenuation in the body. As a consequence, iterative
methods can improve image quality and achieve considerable resolution
recovery. However, iterative algorithms require more computing time and
power. Furthermore, there is the challenge of choosing the right number of
subsets and iterations which leads to a tradeoff between noise and bias.
Although iterative methods are now in widespread use in clinical and
preclinical systems, recent studies have concluded that analytical methods
could still have advantages over analytic methods in specific applications.
For example, a recent dynamic brain PET study by Reilhac et al. concluded
that analytical methods are more robust to low count data than iterative
methods. In another study by Conti et al., it was demonstrated that TOF FBP
has improved performance over TOF OSEM.
In this presentation we will present recent results from the spline reconstruction technique (SRT), a new analytic, two-dimensional reconstruction
algorithm based on cubic splines. We will present the mathematical
formulation of the algorithm and comparisons with FBP and OSEM, using
simulated data from a clinical PET system, as well as real data obtained
from clinical and preclinical PET scanners. Furthermore, we will present
preliminary results from IART (inverse attenuated Radon transform), an
analytic reconstruction technique based on cubic splines that inverts the
attenuated Radon transform and is better suited for SPECT where attenuation correction is needed.
AN OVERVIEW OF THE CONCERT PROJECT
John Damilakis. Professor of Medical Physics, University of Crete, Greece
The overall aim of the CONCERT (Conceptus Radiation Doses and Risks
from Imaging with Ionizing Radiation) project is to perform original
research from which new findings, innovations and practical guidelines for
optimal clinical management of pregnant patients needing radiologic
procedures will result. An additional objective is to generate dose data that
may be used for the implementation of a radiation protection program
designed for pregnant employees working in imaging departments,
interventional laboratories and electrophysiological suites.
The activities of the project focus on the following main tasks:
a) Conduction of a nation-wide study (survey) on current practice patterns
in imaging of pregnant patients and on policies for screening women of
childbearing age for pregnancy before imaging with ionizing radiation
b) Development of methods for estimation of conceptus dose from imaging examinations performed on the mother
c) Development of a method for (a) anticipation of conceptus dose
from occupational exposure of pregnant staff during fluoroscopicallyguided procedures and (b) estimation of maximum workload
allowed for each month of gestation period following pregnancy
declaration
d) Development of a software expert system that will allow a) calculation
of conceptus radiation dose and risk associated with imaging examinations
performed on the expectant mother and (b) anticipation of conceptus
dose and determination of the maximum workload for the pregnant
employee who participates in fluoroscopically-guided interventional
procedures
e) Organization of a workshop on pregnancy and radiation protection to
discuss the findings of the survey and disseminate the research results.
f) Development of guidance document on a) the management of pregnant
patients who need radiologic examinations, b) the management of pregnant employees exposed to considerable levels of occupational radiation
and c) policies for screening women of childbearing age for pregnancy
before imaging procedures
The project started in September 2012 and ends in September 2015.
CONCERT is supported by the Greek Ministry of Education and Religious
Affairs, General Secretariat for Research and Technology, Operational
Program 'Education and Lifelong Learning', ARISTIA.
HOW
TO ESTIMATE
CONCEPTUS
RADIATION
DOSE
FROM
RADIOGRAPHIC, FLUOROSCOPIC AND FLUOROSCOPICALLY GUIDED
INTERVENTIONAL PROCEDURES? (REVIEW COURSE TALK FOR THE
CONCERT PROJECT)
G. Solomou, J. Stratakis, J. Damilakis. Department of Medical Physics,
Faculty of Medicine, PO Box 2208, University of Crete, Iraklion 71003,
Crete, Greece
Radiologic evaluation may be needed during pregnancy to assess common
causes of acute abdominal or thoracic pain. Accidental irradiation of
pregnant women from radiologic examinations may occur during the
early postconception weeks. In each case, there has been a growing
concern about radiation exposure which invokes a great anxiety for the
pregnant patient as well as the treating doctor and may probably lead to
the unnecessary termination of pregnancy. However, conceptus doses
below 100 mGy should not be considered a reason for termination. While
such a high-level exposure rarely occurs during a single medical diagnostic procedure, the estimation of conceptus radiation dose is essential
to determine radiogenic risks to the unborn child and inform the
oncoming mother.
Several methods have been developed to estimate conceptus radiation
dose in pregnant woman who undergo radiographic, fluoroscopic and
fluoroscopically guided interventional procedures. These methods use
thermoluminescence dosimeters along with anthropomorphic phantoms,
which represent pregnant patients at various gestational stages. Computational methods, which are based on the Monte Carlo transportation code
as well as mathematical phantoms have also been applied to estimate
conceptus radiation dose in radiologic procedures. An advantage of the
latter methods is that they may take into account the somatometric
characteristic of the pregnant patients, such as body size, perimeter of the
abdomen and conceptus location.
A literature review on the methodologies applied to estimate conceptus
radiation dose in pregnant patient who undergo diagnostic radiological
procedures is presented.
HOW TO ESTIMATE CONCEPTUS DOSE FROM CT EXAMINATIONS
Kostas Perisinakis. Department of Medical Physics, Faculty of Medicine, PO
Box 2208, University of Crete, Iraklion 71003, Crete, Greece
The utilization of computed tomography (CT) in pregnant patients has
increased in recent years, following the same trend observed for nonpregnant patients. In case of a pregnant patient subjected to CT exposure,
apart from the risk for carcinogenesis to the expecting mother, there is also
concern about the teratogenic and carcinogenic effects of ionizing
Abstracts / Physica Medica 30S1 (2014)
radiation to the developing conceptus. To estimate the radiogenic risks for
an exposed conceptus to be used in risk benefit analysis for a certain CT
examination, the accurate determination of absorbed dose to the
conceptus is prerequisite.
CT exposures of pregnant patients may be categorized in three types
corresponding to conceptus a) entirely excluded, b) partially included
and c) entirely included in the primarily exposed body region. This
categorization is associated with the size of conceptus at the time of
exposure. As gestation progresses, conceptus size is increased and
therefore, partial conceptus exposures may occur with increased
possibility.
Several methods have been proposed in literature for the determination
of conceptus dose from CT exposures such as a) the use of the computed
tomography CT dose index (CTDI), b) the IMPACT CT Patient Dosimetry
Calculator, c) formulas and relevant data provided in the literature, d)
Monte Carlo simulation with standard anthropomorphic mathematical
phantoms simulating pregnant patients at different gestational stages
and e) the IMPACT MC dosimetry tool. Some methods are limited to the
1st trimester of pregnancy while others may be used in all gestational
stages. Some methods may be used only in case of entire or partial direct
exposure of conceptus while others may be also used in case conceptus
is not primarily exposed. Applicability of the above methods in association with z-overscanning effect and the use of adaptive section collimation, the use of automatic exposure control and the use of iterative
reconstruction algorithms will also be discussed. The pros and cons of
the above methods regarding accuracy, applicability, required equipment and cost will be discussed and guidelines will be provided
regarding the appropriate use of available methods to estimate
conceptus dose in case of intentional or inadvertent CT exposure of a
pregnant patient.
OCCUPATIONAL EXPOSURE OF PREGNANT PERSONNEL (REVIEW
COURSE TALK FOR THE CONCERT PROJECT)
John Stratakis PhD, Kostas Perisinakis PhD, Georgia Solomou MSc, John
Damilakis PhD *. Department of Medical Physics, Faculty of Medicine, PO
Box 2208, University of Crete, Iraklion 71003, Crete, Greece
Development of interventional radiology (IR) has been accompanied by a
significant concern for the safety of the staff involved in interventional
procedures, since patient and staff doses in the IR laboratory may be
increased because of case difficulty, patient condition, and operator’s
experience. Many researchers have pointed out issues of interest within
the optimization of radiation protection that included assessment of dose
and risks of interventional laboratory personnel focused mainly on radiation protection on cardiological, orthopedic and angiographic procedures.
Information about conceptus occupational exposure during IR procedures
still remains limited.
An anthropomorphic phantom was exposed at projections commonly used
in IR procedures. An extended range of combinations of tube voltage and
beam filtration were used. For the measurement of scattered air-kerma,
the area relative to the sides of the fluoroscopy table occupied by IR
personnel during a procedure was divided into a 0.25 m grid. Dose-areaproduct (DAP) rate normalized air-kerma values were calculated at all
points of the grid. Occupational abdominal surface doses and gestationage specific conceptus doses were derived using the projection specific air
kerma values for the senior inter, resident, and other present medical/
nursing staff. The effect of radio-protective gear to dosimetric data was
examined.
Normalized to DAP rate dosimetric iso-curves produced will assist
operators to visualize the spatial distribution of abdominal doses and
lower their abdominal exposure, taking shielding and positioning
precautions.
Normalized data are technique- and instrumentation-independent.
Normalized abdominal exposure and conceptus dose data may help
evaluated working conditions in IR laboratory and will enable estimation
of work restrictions such as permissible workloads and radiogenic risks
delivered to medical personnel. Additionally, anticipation of conceptus
dose can be derived for any gestational stage for pregnant staff carrying
ouy IR procedures. This method may assist the evaluation of the working
11
conditions following the declaration of pregnancy of medical staff involved
in diagnostic and therapeutic IR procedures.
FINAL RESULTS OF THE EUROPEAN 'GUIDELINES ON MPE' PROJECT
Carmel J. Caruana. Medical Physics Department, University of Malta; EFOMP
representative on the 'Guidelines on Medical Physics Expert' project; Past
Chair, EFOMP Education and Training Committee
The aim of the European Commission project 'Guidelines on Medical
Physics Expert' (TREN/09/NUCL/SI2.549828) has been to provide for
improved implementation of the provisions relating to the Medical
Physics Expert (MPE) of Council Directive 97/43/EURATOM (Medical Exposures Directive, MED) and the more recent 2013/59/EURATOM of 5
December 2013 laying down basic safety standards for protection against
the dangers arising from exposure to ionising radiation (BSS). In this way,
the results of the project support the European Commission in its actions
relating to the justification and optimisation of medical exposures. The
final results of the project have been an elaboration of the role of the MPE
including an agreed mission statement and detailed list of key activities,
agreed qualification and curriculum frameworks for the MPE in Europe,
recommendations for recognition of the MPE and minimum MPE staffing
Levels. It is expected that the project will lead to improved harmonisation
of the profession in Europe. This presentation will summarise the final
results.
EUTEMPE-RX: A NEW EC SUPPORTED COURSE FOR MEDICAL PHYSICS
EXPERTS IN RADIOLOGY
H. Bosmans a, K. Bliznakova b, R. Padovani c, S. Christofides d, N. Van
Peteghem a, Virginia Tsapaki e, C.J. Caruana f. aDepartment of imaging and
pathology, University of Leuven, Belgium; bTechnical University of Varna,
Bulgaria; cUniversity Hospital S. Maria della Misericordia of Udine, Italy;
d
Medical Physics Department, Nicosia General Hospital, Cyprus;
e
Konstantopoulio General Hospital, Greece; fMedical Physics Department,
University of Malta, Malta
The main responsibility of the medical physics expert (MPE) is to ensure
the optimal use of ionizing radiation in healthcare. To fulfill this responsibility it is essential that these healthcare professionals are trained
to the highest level, defined as European Qualifications Framework
for Lifelong Learning (EQF) level 8 by the European Commission’s
‘Guidelines for the MPE’ [1]. The main objective of the EUTEMPE-RX
project is to provide a model training scheme that allows the medical
physicist in diagnostic and interventional radiology (D&IR) to reach this
high level.
A European network of partners was brought together in an FP7 EC project
to ensure sufficient expertise in all aspects of the subject and to create a
harmonized course programme. Targeted participants are medical physicists in D&IR in hospitals, engineers and scientists in medical device industry and regulatory authorities. 12 course modules are being developed
at EQF level 8, with radiation safety and diagnostic effectiveness being
prevalent subjects. The course design will combine modern online
teaching methods (an e-learning platform) with more classical face-toface teaching using a blended learning approach. This is done to limit the
time away from home for course participants, allowing young parents and
busy workers to follow the course modules. A business plan is under
development to ensure the continued existence of the EUTEMPE-RX
project.
The course module topics are: (1) Development of the profession and the
challenges of the MPE; (2) Radiation biophysics and radiobiology; (3)
Introduction to Monte Carlo simulation; (4) Fundamental physics of Xrays; (5) Anthropomorphic phantoms; (6) The development of advanced
QA protocols; (7) Optimization of X-ray imaging; (8) Role of the medical
physicist in CT; (9) Achieving quality in mammography; (10) High dose Xray procedures in interventional radiology and cardiology; (11) Radiation
dose management of pregnant patients; (12) Personnel dosimetry.
References:
[1] Guidelines on Medical Physics Expert. European Commission. Radiation
Protection 174, (2014)
12
Abstracts / Physica Medica 30S1 (2014)
THE ‘EUROPEAN DIAGNOSTIC REFERENCE LEVELS FOR PAEDIATRIC
IMAGING’ PROJECT
John Damilakis. Professor of Medical Physics, University of Crete, Greece
Despite a large number of studies available from European countries, the
DRLs for paediatric patients are only available for some common radiological examinations. There is a need to consolidate what is available and
to provide guidance on what actions are needed in using Diagnostic
Reference Levels (DRLs) to further enhance radiation protection of children. The ‘European DRLs for Paediatric Imaging’ project is aimed to
attend to this situation. The professional organisations involved include
ESR as coordinator as well as EFOMP, EFRS, and ESPR, covering the key
European stakeholders and professional groups with relevance to radiation protection of paediatric patients. The project is divided into 4 Work
Packages (WPs); each work package covers specific tasks contributing to
the common objective of enhancement of radiation protection of paediatric patients through the concept of DRLs. WP0, chaired by the coordinator of the project, is responsible for the management and general
coordination of the project. WP1 is responsible for assessing and
agreeing on a methodology for establishing and using DRLs for paediatric
imaging, and for producing European guidelines including data provided
by WP 2. WP2 is responsible for updating and extending the existing
European DRLs to cover more procedures and a wider patient age/weight
range. WP 3 chaired by the scientific coordinator will organize the European workshop in Lisbon, Portugal from October 15th to October 17th
2015 to discuss the findings of the studies conducted under the project
and to subject the draft European Guidelines to critical review and discussion.
SYNERGY BETWEEN NUCLEAR RESEARCH, INNOVATION AND
EDUCATION IN EURATOM PROGRAMMES, WITH EMPHASIS ON
SAFETY CULTURE
Georges Van Goethem. European Commission, DG Research and Innovation,
Dir Energy - G.4 / Fission Energy, B-1049 Brussels, Belgium
In a rapidly changing multicultural world full of political and economic
uncertainties, research, innovation and education (RIE), in particular, in
nuclear fission and radiation protection are faced with a number of scientific-technological and socio-political challenges. In the European Union
(EU), these challenges are, for example, breakthrough technological developments of interdisciplinary type and enhanced public engagement in
nuclear matters. The aim is to continuously improve applications of nuclear fission energy and ionising radiation in the medical and industrial
fields for the benefit of all people.
In the EU, the recent “Council Directive 2013/59/Euratom laying down
basic safety standards for protection against the dangers arising from
exposure to ionising radiation” has a new Chapter IV “Requirements for
Radiation Protection Education, Training and Information” requiring
Member States to have systems in place for the education, training and
recognition of specific experts (in particular, “Medical physics experts” Article 83).
For power generation or for medical applications, experts with highly
qualified nuclear and radiation safety culture competences will be needed
over a long time period, in particular, to deal with radiation protection
issues in modern diagnosis and treatment. Safety culture is usually defined
as “an organisation’s values and behaviours - modelled by its leaders and
internalised by its members - that serve to make nuclear safety the overriding
priority.”
In this context, the main stakeholders of Euratom RIE programmes have
developed a common approach regarding needs, vision and implementation instruments. Focussing on knowledge creation and competence
building, their common approach can be summarized as follows:
1 e Analysis of needs: e.g. what kind of knowledge, skills and competences
(KSC) should be taught in order to continuously improve technical, human
and organisational aspects ?
2 e Convergence towards a common vision: e.g. towards a new type of
governance for RIE in the EU, integrating expert, policy and public
knowledge to support decision making processes
3 e Development of instruments: e.g. synergy of national and Euratom RIE
programmes aiming at preparing a new generation of experts in a global
economy (EU and beyond).
Making lifelong learning and cross-border mobility a reality is an important objective of the Education, Youth and Culture policy of the EU (e.g.
“European Credit system for Vocational Education and Training” /ECVET/).
Lessons will be drawn from the preliminary application of ECVET tools and
methodology, such as the description of qualifications in terms of “units of
learning outcomes” related to KSC, in Euratom projects.
INVOLVEMENT OF AAPM IN EUROPE
Gene Lief. White Plains Hospital, Radiation/Oncology Department, New York,
USA
With increased globalization of Medical Physics profession, American Association of Physicists in Medicine (AAPM) increases international activity.
Collaboration with EFOMP is one of the main priorities. Memorandum of
Understanding between two societies proposed in 2013 paves the way for
future collaboration.
The first step in the collaboration will establish free flow of information
between EFOMP and AAPM. The websites of the two organisations will
have links cross-referencing each other. Another aspect of the collaboration will be to organize joint sessions at each other’s society meetings. The
two societies believe that it would be beneficial to arrange joint sessions at
EFOMP and AAPM Annual meetings where practicable. Since both societies
have different Working Groups operating in various fields of Medical
Physics, a third important aspect of collaboration will include interaction
between these Working Groups.
Implementing those goals, we started building AAPM website with links to
different international organizations. Joint EFOMP-AAPM sessions are
being organized. International Educational Activities Committee of AAPM
organizes courses in countries that would mostly benefit from such activities. The last 3 courses in Europe took place in Prague in 2008, Patras in
2011, and Tallinn in 2014. A group of AAPM specialists in brachytherapy are
actively collaborating with European brachy GYN group EMBRACE from
Vienna.
In conclusion, future globalization of Medical Physics presents new opportunities of mutually beneficial transatlantic cooperation.
DEVELOPING INTERNATIONAL COMMUNICATION VIA THE WEB
George C. Kagadis PhD, FAAPM. Department of Medical Physics, School of
Medicine, University of Patras, GR 26504, Greece
Because of widespread availability of Information Technologies and
Internet, a lot of scientists are nowadays using them for education and
research purposes as well as collaboration in general. Accompanying this
growth, the discipline of medical physics has evolved and advanced. The
Internet provides us with the means of accessing electronic information
and resources at a click of a mouse. However, caution should be exercised
since the majority of the web resources are not peer-reviewed. Nonetheless, few organizations are developing web sites that provide adequately
reviewed material that can help current and future medical physicists to
advance communication in our science.
Internet is not just a publishing board with announcements and articles
in various websites, but it has furthermore established the appropriate
infrastructure for society transformation in a digital community, where
information is delivered anywhere from anyone. Social media and blogs
are taking the place of the conventional fora for idea and knowledge
exchange among scientists. The high availability of high bandwidth
Internet connection worldwide has reformed the type of information
delivered, since we can now share videos or large files and have a reliable video-based conversation with colleagues in the other side of the
world.
The ever-advancing technology of small and portable devices like tablets
and smartphones has changed the way we access information and
communicate. We can now easily read and answer our e-mails, watch a
video or conduct a video-call from our mobile device in a fast and reliable
manner.
Abstracts / Physica Medica 30S1 (2014)
13
ICRP COMMITTEE 3 OVERVIEW (PROTECTION IN MEDICINE)
Open Discussion
References
[1] European Commission Radiation Protection Report No. 174, “Guidelines
on Medical Physics Expert”, in publication
[2] Eudaldo, T., Olsen, K. “The present status of Medical Physics Education and Training in Europe: An EFOMP survey”, Physica Medica (2008)
24, 3 - 20
[3] EFOMP PS12, “The present status of Medical Physics Education and
Training in Europe. New perspectives and EFOMP recommendations”,
Physica Medica (2010) 26, 1 - 5
~ o a, D.L. Miller b, M. Rehani c. aICRP Committee 3. Chairman; bICRP
E. Van
Committee 3. Vice-Chairman; cICRP Committee 3
IAEA QUALITY AUDITS IN RADIOTHERAPY
The high penetration of cloud computing technology leads to a situation
where all applications will abandon their traditional operation and
move to the cloud, where they can be delivered as services. In medical
physics science, as the technology continuously breaks the ethical and
security barriers, sharing of medical imaging data between experts
world-wide tends to become a routine task. Examples of current accomplishments of international communication via the web will be
presented.
Committee 3 of ICRP is concerned with protection of persons and unborn
children when ionising radiation is used for medical diagnosis, therapy, or
biomedical research. According to the 2011-2017 Strategic Plan, Committee 3 develops recommendations and guidance for protection of patients,
staff, and the public against radiation exposure in medicine. This paper
presents an overview of the work of the Committee in recent years and
current work in progress. The ICRP reports dealing with radiological protection (RP) in medicine in the last 10 years cover topics on: education and
training in RP; preventing accidental exposures in radiation therapy; doses
to patients from radiopharmaceuticals; radiation safety aspects of
brachytherapy; release of patients after therapy with unsealed radionuclides; and managing radiation dose in interventional radiology, digital
radiology, computed tomography, paediatrics, cardiology and other medical specialties. Work in progress deals with RP in Ion Beam Therapy,
Occupational Protection in Brachytherapy, Justification in Imaging, RP in
Cone Beam CT, Doses to Patients and Staff from Radiopharmaceuticals
(update), Occupational Protection in Interventional Radiology, and Diagnostic Reference Levels for Diagnostic and Interventional Imaging. The
Committee is also involved in preparation of a document on effective dose
(and its use medicine).
SYMPOSIUM: EUROPEAN STANDARD ON MEDICAL PHYSICS SERVICES
Stelios Christofides a, Derek Pearson b, Gerard Colenbrander c, Luca
Moro d. aMedical Physics Department, Nicosia General Hospital, Nicosia,
Cyprus; bProfessional Adviser to the Chief Scientific Officer, NHS England.
U.K.; cDepartment of Medical Physics, Spaarnehospital, Hoofddorp, The
Netherlands; dMedical Physics Department, Salvatore Maugeri Foundation,
Pavia, Italy
One of the initiatives of the EFOMP at the European Level is the recognition
of Medical Physics as a profession by the European Union. As is evident
from the surveys carried out under the EC sponsored project ‘Guidelines
on Medical Physics Expert’ [1] and an earlier survey by EFOMP [2, 3] the
education and training of Medical Physicists and Medical Physicists at
Expert level is not harmonised across the European Union and therefore
the services they provide. This hinders the recognition of Medical Physics
as a profession by the European Union and restricts the free movement of
Medical Physicists and Medical Physics Experts from one European Union
Member State to another.
For the above reasons EFOMP has decided to initiate the development of a
Europe
en de Normalisation) standard for “Medical Physics
CEN (Comite
Services” in an effort to assist in the harmonisation of the Medical Physics
services provision across Europe. One aspect of this is the harmonisation of
the education, training and competence of Medical Physicists, Medical
Physics Experts and Technologists in the various fields of Medical Physics
for which they provide a service.
The EFOMP Council approved the establishment of a Working Group to
pursue this project at its meeting in Brighton, UK in September 2013. The
purpose of the Symposium is to present the work progress of this working
group and seek feedback from the workshop participants.
The symposium consists of the following short presentations that will be
followed by open discussion:
Introduction (Stelios Christofides)
CEN Standardisation Procedure (Luca Moro)
Survey results (Gerard Colenbrander)
Proposed Structure of Standard (Derek Pearson)
J. Izewska, P. Bera, G. Azangwe, P. Grochowska, A. Meghzifene. International
Atomic Energy Agency, Vienna, Austria
Quality audits in radiotherapy have proven to be a useful tool for quality
assessment and practice improvement in radiotherapy centres. The IAEA/
WHO TLD postal dose audits have been in operation since 1969 and to-date
it checked the calibration of 10500 radiotherapy beams in 2050 centres in
130 countries. Several discrepancies in radiotherapy dosimetry have been
discovered and rectified. Throughout the time, radiotherapy centres
improved their ability to deliver the dose accurately. The percentage of
acceptable TLD results has increased from 50% in early years to 95% at
present. However, there are still issues with basic clinical dosimetry that
need to be addressed.
Another dosimetry audit programme developed by the IAEA uses the endto-end approach, i.e. it assesses the entire workflow for conformal radiotherapy techniques, from patient data acquisition and computerized
treatment planning to dose delivery. It is based on a semi-anthropomorphic phantom circulated among radiotherapy centres. This programme
was implemented in Europe and it contributed to improvements in clinical
dosimetry and treatment planning in some participating centres.
The IAEA’s comprehensive clinical audits by the Quality Assurance Team
for Radiation Oncology (QUATRO) assess overall practices in radiotherapy
centres including the infrastructure, patient and equipment procedures,
quality assurance programmes, radiation protection, staffing levels and
professional training of the local radiotherapy staff. To-date QUATRO has
conducted over 70 audits on request, in radiotherapy centres of Central
and Eastern Europe, Asia, Africa, and Latin America. Some centres have
been acknowledged for the adequate level of practices; in other centres
auditors identified gaps and documented areas for improvement. Overall,
QUATRO audits have contributed to improvements at centres, but also
have identified common issues that have been addressed internationally.
QUATRO procedures, in addition, have been prepared for the resolution of
suspected or actual dose misadministrations in radiotherapy, including the
follow-up of inconsistent results detected by the IAEA/WHO TLD postal
dose audits. This way radiotherapy centres can receive help at an early
stage in the problem-solving process, focusing on prevention of incidents
or accidents in radiotherapy.
IAEA SPONSORED TREATMENT PLANNING SYSTEM AUDITS IN EUROPE
E. Gershkevitsh a, C. Pesznyak b, B. Petrovic c, J. Grezdo d, K. Chelminski e,
M.C. Lopes f, J. Izewska g. a North Estonia Medical Centre, Tallinn, Estonia;
b
National Institute of Oncology, Budapest, Hungary; c Institute of Oncology
Vojvodina, Sremska Kamenica, Serbia; d St. Elizabeth Institute of Oncology,
Bratislava, Slovakia; e M. Skłodowska-Curie Memorial Cancer Center and
Institute of Oncology, Warsaw, Poland; f Portuguese Institute of Oncology,
Coimbra, Portugal; 7 International Atomic Energy Agency, Vienna, Austria
Background and purpose: One of the newer audit modalities operated by
the IAEA involves audits of treatment planning systems (TPS) in radiotherapy. The main focus of the audit is the dosimetry verification of the
delivery of a radiation treatment plan for 3D conformal radiotherapy using
high energy photon beams.
Material and methods: The TPS audit reviews the dosimetry, treatment
planning and radiotherapy delivery processes using the ‘end-to-end’
approach, i.e. following the pathway similar to that of the patient, through
imaging, treatment planning and dose delivery. The audit is implemented
14
Abstracts / Physica Medica 30S1 (2014)
at the national level with IAEA assistance. The national counterparts
conduct the TPS audit at local radiotherapy centres through on-site visits.
TPS calculated doses are compared with ion chamber measurements
performed in an anthropomorphic phantom for eight test cases per algorithm/beam. The set of pre-defined agreement criteria is used to analyze
the performance of TPSs.
Results: TPS audit was carried out in sixty radiotherapy centers in eight
European countries e Estonia, Hungary, Latvia, Lithuania, Serbia, Slovakia,
Poland and Portugal. In total, 190 data sets (combination of algorithm and
beam quality) have been collected and reviewed. Dosimetry problems
requiring interventions were discovered in about 10 % of datasets. In addition,
suboptimal beam modelling in TPSs was discovered in a number of cases.
Conclusions: The TPS audit project using the IAEA methodology has
verified the treatment planning system calculations for 3D conformal
radiotherapy in a group of radiotherapy centres in Europe. It contributed to
achieving better understanding of the performance of TPSs and helped to
resolve issues related to imaging, dosimetry and treatment planning.
DOSIMETRY AUDITS IN RADIOTHERAPY IN THE CZECH REPUBLIC
Irena Koniarova, Daniela Ekendahl, Ivana Horakova, Michaela
Kapucianova, Vladimir Dufek. National Radiation Protection Institute,
Prague, Czech Republic
Background: The independent audits in radiotherapy are carried out by the
National Radiation Protection Institute as a part of the regulatory authority
activity since 1996. The system includes TLD postal audits (external radiotherapy) and on-site audits (external radiotherapy and brachytherapy).
TLD audit can be performed in several versions differing in the scope and
focus of dose measurements. Basic TLD audit consists in beam calibration
check. Each clinically used beam must undergo it at least once per two
years. During 1997 e 2013, a total of 1435 beams have been thus
controlled. Advanced versions of TLD audit focused on more complex
conditions of irradiation (non-reference geometries, MLC fields, small
IMRT fields, inhomogeneities) have been performed in the case of a
request or research studies.
On-site audit is performed after the commissioning of each unit. The
absorbed dose to water (or RAKR for brachytherapy), beam quality, output
and wedge factors, PDD, MLC positioning, MLC transmission, and dosimetric leaf gap (where applicable) are controlled. Mechanical parameters
(isocenter stability, radiation field size, table parameters, etc.) are evaluated as well. A number of 535 megavoltage photon and electron external
beams, 103 kilovoltage external beams, and 32 brachytherapy sources have
been controlled since 1996. 2 proton beams were checked in 2013. Checks
of non-dosimetric parameters and imaging functions of TPS with QUASAR
phantoms can be performed on request. In addition, 19 departments (23
treatment plans) have been checked using a special pelvic phantom in
end-to-end audit for IMRT and IMAT prostate treatment in 2013. Delivered
doses to PTV and rectum were measured with ionisation chambers in 3
planes. Planar dose distribution has been verified with EBT2 film. Retrospectively, it was possible to make DVHs analysis and compare all IMRT
plans for the pelvic phantom showing common planning practice in the
Czech Republic for photon IMRT and proton radiotherapy.
Conclusion: The audits revealed several significant errors that might
potentially lead to an accident. All results can be analysed retrospectively,
showing trends related to chosen indicators.
DOSIMETRY AUDITS IN RADIOTHERAPY IN GREECE
C.J. Hourdakis, A. Boziari, V. Kamenopoulou. Greek Atomic Energy
Commission
Background: Greek Atomic Energy Commission (EEAE) has been running
dosimetry audits by means of on-site visits in all Greek radiotherapy (RT)
and brachytherapy (BT) centers, since 2002. Two rounds (2002-2006 and
2006-2011) have been completed, the 3rd being in progress.
Materials and Methods: Dosimetry measurements and QC tests were
performed at RT and BT systems (linacs, 60Co and 192Ir HDR) using EEAE’s
phantoms and equipment. (a) The systems’ performance was evaluated
through mechanical and radiation tests. (b) Relative (TPR20,10, R50 , PDD)
and absolute dosimetry (absorbed dose to water) was performed at photon
and electron beams according to IAEA-TRS-398 protocol. For BT beams, the
reference air kerma rate was determined. The difference, dr, of the values
measured by EEAE, DM, to the stated by RT center, DS , was calculated
(dr¼DM/DS-1). (c) MU calculations (by TPS or manually) were assessed at
various irradiation conditions (depth, fields, wedges, etc), by comparing
DM (at same irradiation conditions and MU) to Ds for the same MU. (d) The
overall RT procedure (CT, simulation, planning, verification, irradiation)
was assessed qualitatively and quantitatively, using a solid water phantom,
with inhomogeneities and tissue deficits, irradiated at multiple photon
beams. The measured dose was compared to the TPS stated dose.
Results: More than 90% of the linacs and less than 80% of 60Co showed
satisfactory mechanical performance. Relative dosimetry for photons and
electrons was accurate in most cases (>95%). Photons beam absolute
dosimetry showed that in 95% of beams dr<3%. For electrons, 80% of the
beams exhibited dr<3%. All BT beams showed dr<3%. In comparing TPS
output data, 86% of the beams showed dr<3%, and 3% of the beams dr>5%.
Dosimetry assessment of the overall RT procedure, showed that in 90%
cases dr<5%, and in 5% cases dr>7%. Improvement of dosimetry accuracy
between the rounds was observed.
Discussion: Dosimetry audits contributed significantly to the dosimetry
accuracy and homogeneity improvement, in the country. On site visits
gave the opportunity to resolve all discrepancies and enhance knowledge
dissemination.
DOSIMETRY AUDITS IN RADIOTHERAPY IN POLAND
ski, J. Rostkowska. Department of Medical Physics,
W. Bulski, K. Chełmin
Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology,
Warsaw
Purpose: The Secondary Standard Dosimetry Laboratory (SSDL) of the
Medical Physics Department of the Centre of Oncology in Warsaw has
become a member of the IAEA/WHO international network of such laboratories in 1988. The SSDL has been carrying-out the external postal TLD
audits since 1991.
In the presentation the scope of dosimetry audits in Poland is overviewed.
Materials and methods: TLD runs for on axis measurements in nonreference conditions were performed in Co-60, X-ray and electron beams.
In recent years the audits were extended to off-axis measurements
(symmetric and asymmetric fields) and to MLC shaped irregular fields.
A heterogeneous cubic-shaped phantom developed in the frame of IAEA
Coordinated Research Project was used for the audits. The phantom consists
of frame made of polystyrene and the bone or lung inhomogeneity slabs.
Another phantom, an anthropomorphic CIRS 002LFC thorax phantom, was
used for dosimetry checks according to the IAEA-TECDOC-1583 report.
Results: The results of the TLD postal audit in non-reference conditions for
on axis measurements are in the majority o cases within the ±3.5% tolerance limit which is usually used for reference conditions.
Nine Polish radiotherapy centers (of total 30) were audited with the use of
the IAEA cubic phantom. Generally most of the results from TLD and
ionizing chamber were within ±5% tolerance.
Seven radiotherapy centers in Poland have been audited with the CIRS
phantom so far. Eight cases with different beam geometry and accessories
representing different complexity of the plan were performed on six
different TPS. All algorithm/beam datasets showed passing-rate higher
than 50% of predefined agreement criteria.
Conclusions: Over the last 20 years the postal TLD audits fulfilled their role
and remain the primary and well established dosimetric audit method.
The measurements allow to the detect limitations of TPS calculation algorithms. The audits performed with the use of the IAEA heterogeneous
phantom and with the CIRS phantom seem to be an effective tool for
detecting errors in radiotherapy procedures.
EUROPEAN DIAGNOSTIC REFERENCE LEVELS IN PAEDIATRIC IMAGING
Stephen Evans. Head of Medical Physics, Northampton General Hospital, UK
Children are at a much higher risk compared to adults from developing
cancer from exposure to the same quantity of ionising radiations. For many
radiodiagnostic examinations, significant variations in the levels of
Abstracts / Physica Medica 30S1 (2014)
radiation doses received by children undergoing the same examinations are
seen between radiology departments. A way of ensuring no child receives
more dose than is necessary for their medical exposure to ionising radiation
is to establish appropriate levels of diagnostic doses that should be achieved
(or not exceeded) by all radiology departments for every radiodiagnostic
examination. These are noted as diagnostic reference levels (DRLs).
DRLs for adult patients are commonly based on the dose values for the
average sized adult or phantom. The derivation of DRLs for paediatric
patients is more complex due to the wide variation in patient size. In 1996,
paediatric DRLs for plain radiography were provided (“European Guidelines
on Quality Criteria for Diagnostic Radiographic Images in Paediatrics” EUR
16261, European Commission, 1996) using the entrance-surface-dose for
standard five-year old children as the reference dose for all paediatric
patients.
In 1997 it became a requirement in European Member States that DRLs for
radiodiagnostic examinations are promoted and appropriate practical
techniques used - particularly for the medical exposure of children (Council
Directive 97/43/EURATOM, Article 4.2.a and Article 9).
It has long been recognised (“Guidance on diagnostic reference levels DRLs
for medical exposure”, European Commission Radiation Protection 109 (RP
109), 1999) that the exposures requiring the most attention and are of the
most importance for the establishment of DRLs are the high-dose medical
examinations, especially computed tomography (CT) and interventional
procedures (IR). The above publication also recognised the relative difficulty in defining these most important DRLs.
Since the publication of the above documents, a huge growth has been
observed in the use of CT and IR examinations with paediatric imaging
being among the fastest growing.
Much work has been done and many publications exist on paediatric
doses, however, despite the emphasis placed on the need for establishing
paediatric DRLs, difficulties have been encountered in producing DRLs for
children, particularly for IR procedures.
The talk will discuss the difficulties and challenges in providing paediatric
DRLs, identify some key publications and studies, particularly in Europe,
and consider what may follow.
PERSONAL DOSIMETRY
RESSSSOURCES
15
e
REASONABLY
USING
THE
EXISTING
€ntgendiagnostik und Nuklearmedizin,
Markus Borowski. Institut für Ro
Klinikum Braunschweig, Poland
Personal working in controlled areas is expected to be exposed to an
increased level of ionizing radiation. Apart from whole body exposure in
particular extremities or the eye lenses can be exposed to considerable up
to critical levels. To monitor the possible radiation exposure all persons
entering controlled areas are obliged to personal dosimetry. Within legal
dosimetry persons normally are asked to wear film or TLD based dosimeters for whole body monitoring. Personal with an expected increased
exposure of the extremities, e.g. within nuclear medicine departments, are
asked to use finger dosimeters. Because of an ongoing discussion on the
effect of ionizing radiation on the eye lens an upcoming requirement of
dosimetry of the eye lens, at least for interventionalists, can be anticipated.
Each year there are several million euro spend for personnel dosimetry
within the EU. On the other hand more than 95% of all persons monitored
with whole body dosemeters are exposed to dose levels below the
detection threshold. Extremity dosimetry, as became obvious from the EC
funded ORAMED project, suffers from large uncertainties. For the dosimetry of the eye lens not even the basic scientific research is done jet. Thus,
actually most of the persons do not benefit from the large effort paid. There
are, however, approaches to enhance the output of the personal dosimetry.
These are e.g. an exchange rate of whole body dosemeters, which is
adapted to the height of persons exposure within history or the two
dosimeter approach, which provides a by far more realistic estimation of
the persons effective dose. Another field is the use of active electronic
dosemeters (EPD). These facilitate a direct feedback on individual actions
and provide thereby input for teaching and optimization strategies. EPDs,
however, suffer from the fact that they can get blinded from too high dose
rates. The “more” on information, also, comes along with an increased
effort to analyze them.
Within the talk the usability and cost-effectiveness of different dosimetry
approaches will be discussed. The audience shall leave the session with a
well-founded basis for their own justified decisions. The talk shall open the
view to question normally unquestioned personal dosimetry practices and
show reasonable alternative approaches.
Physica Medica 30S1 (2014)
Contents lists available at ScienceDirect
Physica Medica
journal homepage: http://www.physicamedica.com
Oral Presentations
VALIDATION OF A CALCULATION ALGORITHM FOR ORGAN DOSES
IN THE EXISTING CT DOSIMETRY TOOLS USING PAEDIATRIC
ANTHROPOMORPHIC PHANTOM MEASUREMENTS
re
mie Dabin a, Alessandra Mencarelli a, Lara Struelens a, Choonsik
Je
Lee b. a Department of Radiation Protection, Dosimetry and Calibration,
Belgian Nuclear Research Centre, Mol 2400, Belgium; b Division of Cancer
Epidemiology and Genetics, National Cancer Institute, National Institute of
Health, Rockville, MD 20850, USA
Background: Rapid and user-friendly software tools for individual estimates of organ doses in CT are of the utmost importance to support the
professionals in the choice of the appropriate imaging modalities. Most
CT-dosimetry tools, like CT Expo [1], CT Dosimetry [2], as well as a new
dosimetry tool [3], rely on the assumption that organ doses estimated for
one CT scanner can be converted to other CT scanner using the ratio of the
Computed Tomography Dose Index (CTDI) between two CT scanners. We
tested this assumption for paediatric patients using physical phantom
measurements for various protocols and CT scanners. Measurements were
compared with dosimetry tools.
Materials and methods: Dose to 22 radiosensitive organs were measured
using thermoluminescence dosimeters inserted within an anthropomorphic 5-year old phantom. Dose measurements were performed for wholebody scans on 4 scanner models from the 4 major manufacturers (Siemens,
GE, Philips and Toshiba); both axial and helical modes were tested with
small collimations (below 12 mm). Measured doses were compared with
the results of Monte-Carlo simulations [3].
Results: Whereas the measured organ doses showed important variability
across the different scanner models, doses normalised to CTDI showed
significantly less variation. Higher tube voltage also showed less variation.
The simulated organ doses reasonably compared with the measurements.
For example, at 120 kV in axial mode with 10 mm collimation, the mean
coefficient of variation between the scanner models was below 10%; the
relative difference between measured and simulated organ doses was
within ±15% for most organs.
Discussion: For the tested collimations (below 12 mm), both in axial and
helical modes, the CTDI fairly accounts for the difference in CT design
across different models. Further measurements are being carried out to
test the algorithm against protocols more representative of the clinical
practice.
This study proved that, for small collimations and paediatric patients,
organ doses simulated from one CT scanner can be converted to other CT
scanners using CTDI-ratio. Those results are of interest for fast dose
assessment and retrospective dosimetry studies.
Acknowledgments: These measurements were performed within the
framework of the EPI-CT study, supported by the European Community's Seventh Framework Programme (FP7/2007e2013) under grant
agreement number 269912-EPI-CT: Epidemiological study to quantify
risks for paediatric computerized tomography and to optimise doses.
[4].
References
[1] Stamm G and Nagel H D 2002 CT-expo - A novel program for dose
evaluation in CT G. Stamm and H. D. Nagel, “CT-expodA novel program for
€ Fo: Fortschritte auf dem Gebiete der
dose evaluation in CT Ro
€ ntgenstrahlen und der Nuklearmedizin 174 1570e1576
Ro
[2] Impact Scan: CTDosimetry Version 1.0.4. [(accessed on the 30th of May
2014 )]. Available online: www.impactscan.org/ctdosimetry.htm.
[3] Lee C, Kim, K P, Long D J, Bolch W E 2012 Organ doses for reference
pediatric and adolescent patients undergoing computed tomography
estimated by Monte Carlo simulation Med. Phys. 39 2129e2146
[4] The Epi-CT study: http://epi-ct.iarc.fr/
STUDY OF DOSE PROFILES USING AUTOMATIC TUBE VOLTAGE
SELECTION IN AN ANTHROPOMORPHIC PHANTOM
M. Gabusi, L. Riccardi, M. Paiusco. Veneto Institute of Oncology IOV-IRCCS,
Medical Physics Department,Via Gattamelata 64, 35128 Padova, Italy
Background: Automated tube voltage selection (ATVS) has been
recently introduced as an innovative tool (CarekV by Siemens HealthCare; Forchheim, Germany [1]) aiming to reduce dose to patients in CT
scans and to preserve an acceptable contrast to noise ratio. Several
studies (e.g. [2]) on contrast-enhanced CT angiographies confirm a
reduction of the overall delivered dose to patients (up to 40% [3]). Fewer
publications on chest CTs have been carried out, especially about the
impact of CarekV in unenhanced CT (e.g. [4]), where a dose gain of
lesser amount is expected.
Materials and methods: In this work a study of the local dose profile for
unenhanced thorax CT scan using ATVS (CarekV on Siemens Definition)
was performed, using an Alderson Rando anthropomorphic phantom.
CTDIvol, exposure profiles and Dose Length Products (DLP) were calculated
from DICOM files along scan axis, as function of different voltage modulation parameters. Calculated and measured values were then compared to
fixed-voltage CT scan profiles. Mean CTDIvol and DLP estimated before the
scans were reported for comparison.
Results: The average dose gain calculated from post-scanning profiles
turns out to be lower (10%) than the estimated values. For high values of
contrast gain (low voltage, 80 kV), CarekV allows a dose lowering of
minimum 40% along the phantom chest. However, for low and intermediate contrast gain (sixth tick of the CarekV slider bar), a null CTDI gain or
even local CTDI increase (about 20% for 4th tick) in the upper chest was
found, due to the strong variations in current modulation. On the other
hand, CarekV starts to be effective for soft tissues (abdomen) even at low
contrast gain (2nd CarekV tick), and a substantial reduction (at least 10%)
of abdominal dose can be achieved using the same settings.
Discussion: In conclusion, ATVS may provide a reduction of the average
dose for high contrast settings. Nevertheless, for low contrast settings, a
reduction of the delivered dose along the whole patient's chest values
might not be possible if the image quality is kept constant. A careful position of scan window might be required, in order to systematically reduce
the dose along all the patient's body.
References
[1] Grant, K., and B. Schmidt. “CARE kVdAutomated Dose-Optimized Selection of X-ray Tube Voltage. White Paper. Siemens; 2011.” (2011).
[2] Winklehner, Anna, et al. “Automated attenuation-based tube potential
selection for thoracoabdominal computed tomography angiography:
improved dose effectiveness.” Investigative radiology 46.12 (2011): 767-773.
[3] Lee, Kyung Hee, et al. “Attenuation-based automatic tube voltage selection and tube current modulation for dose reduction at contrastenhanced liver CT.”Radiology 265.2 (2012): 437-447.
2
Abstracts / Physica Medica 30S1 (2014)
[4] Eller, Achim, et al. “Attenuation-based automatic kilovolt selection in
abdominal computed tomography: effects on radiation exposure and image quality.”Investigative radiology 47.10 (2012): 559-565.
OPTIMIZATION
DEPARTMENTS
OF
CT
PROCEDURES
IN
TWO
RADIOLOGY
I. Dyakov a, M. Alamin b, V. Groudeva c, J. Vassileva a, V. Stoinova c, V.
Hadjidekov b. a National Centre of Radiobiology and Radiation Protection,
Bulgaria; b “Aleksandrovska” University Hospital, Sofia, Bulgaria;
c
“St. Ekaterina” University Hospital, Sofia, Bulgaria
Technical advances allowed utilization of computed tomography (CT)
modality in different medical applications. With the increase in complexity
of CT scanners staff education, proper CT adjustment and optimization of
CT procedures are becoming of higher importance.
The purpose of this study was to improve the practice in two radiology
departments through implementation of optimized CT protocols. Image
quality and patient dose in CT urography (CTU) and cardiac CT were
compared when replacing the standard protocol with low-kV protocols.
Our study was performed with a 64-row detector and a 320-row detector
CT systems, both of Toshiba medical systems.
Three groups of patients examined with different kV in urography phase standard 120; 100 and 80 kV protocols were included in the study. CTDIvol
and DLP were recorded and effective dose was calculated using CT Expo 2.1
software. Image noise, signal to noise ratio (SNR), contrast to noise ratio
(CNR) and figure of merit (FOM) were estimated based on measurements
in clinical and phantom images. Image quality in phantom showed more
than 50% reduction of SNR, CNR and FOM when using 80 kV CTU protocol.
Clinical image quality of low-kV patient images was clinically acceptable.
Higher than 47 % reduction of patient CTDIvol when using 100 kV and more
than 60 % when using 80 kV CTU protocol was achieved. Effective dose was
reduced by more than 60 % with introduction of 80 kV CTU protocol.
Cardiac CT is routinely acquired with retrospective ECG-gating which leads
to increased patient dose, since data is acquired at the entire cardiac cycle,
and not all data is used for post-processing or reconstruction. For selected
patients prospective ECG-gating was applied. Further implementation was
made of low-kV cardiac protocol into practice. More than 56% reduction of
DLP was achieved with the implementation of prospective cardiac protocol. The preliminary results indicated significant dose reduction when
using low-kV cardiac protocol by keeping the adequate diagnostic quality
of clinical images.
EDGE-ENHANCING DIFFUSION NOISE REDUCTION IN DUAL-ENERGY CT
Georgios Vlachopoulos, Spyros Skiadopoulos, Andreas Petropoulos, Anna
Karahaliou, Lena Costaridou. Department of Medical Physics, School of
Medicine, University of Patras, Patras, Greece
Background: Dual-Energy Computed Tomography (DECT) is an evolving
field in radiology. DECT offers material decomposition by exploiting
spectral information of low and high kV energies. Furthermore, DECT allows for increased identification of iodinated structures and improved
differentiation from other high-density substances (e.g. calcium). This
study investigates the effect of an Edge-Enhancing Diffusion (EED) noise
reduction method on the quality of DECT images, derived by varying the
weighting factor (w) of the two spectra (w¼0.1 up to 0.9, in 0.1 step).
Materials and methods: A material equivalent head CT phantom (Mini CT
QC phantom, Gammex) was scanned with a Dual-Source CT system
(Somatom Definition, Siemens) in dual-energy mode. Dual-energy headangio analysis incorporated in the CT system was performed, using a
clinical image acquisition protocol (80kV/213mAs and 140kV/50mAs). An
EED parameter selection procedure was considered by means of quantitative image quality evaluation and qualitative assessment of edge preservation of the 80 kV images. The EED algorithm incorporating the selected
parameters is then used to reduce noise to weighted images of the material
equivalent CT phantom. The quality of EED-filtered weighted images was
quantitatively assessed by means of Contrast, Signal-to-Noise Ratio (SNR)
and Contrast-to-Noise Ratio (CNR) measured on regions of interest of
phantom images corresponding to 14 mg/ml iodine concentration and
bone equivalent material. The quality of EED-filtered weighted images was
also compared to the quality of median-filtered weighted images.
Results: EED filtering improved significantly the quality of DECT weighted
images, performing better as compared to median filtering. Using original
DECT weighted images as a reference, the average image quality
improvement of the filtered weighted images was: SNR¼60.1% and
CNR¼82.4% for EED filtering and SNR¼15.3% and CNR¼18.7% for median
filtering.
Discussion: Results demonstrate that EED improved significantly the
quality of DECT weighted images, suggesting the method potential in
establishing low-dose image acquisition protocols.
5 YEARS CONTINUOUS PATIENT DOSE SURVEY IN INTERVENTIONAL
CARDIOLOGY: LESSONS LEARNED AND FUTURE POTENTIAL
O. Dragusin a, N. Oumohand b, P. Frambach b, D. Wagner b, J.
^pitaux Luxembourgeois, Luxembourg; b INCCI,
ed
eration des Ho
Beissel b. a F
Haerz Zenter, Luxembourg
INCCI is the Luxembourgish national institute for cardiac surgery and
interventional cardiology. It has 2 catheterization laboratories equipped
with X-ray flat panel detectors. About 10 interventional cardiologists are
performing diagnostic and therapeutic procedures (including electrophysiology interventions). The number of interventions is around 3000 per
year. All patient doses are registered in the medical file.
The purpose of the work is to present the evolution of patient doses in last
five years. Yearly reports are generated and discussed with the medical
staff in order to assess current practice in our center.
The interventional cardiology procedures are performed in adults. We
distinguish 3 categories of procedures: diagnostic (coronary angiography),
therapeutic (percutaneous coronary interventions) and electrophysiology
studies.
Following information is available for each patient: radiation dose (total air
kerma-area product KAP, fluoroscopy time, dose at interventional reference point, number of cine acquisitions); personal data (age, body mass
index); procedural details (intervention, number of segments or stent
dilated/implanted, type of access to the lesion, cardiologist that performed
the intervention).
Our analysis is focused on two directions. Firstly, determination of local
reference dose levels for each group of procedures (considering the 75%
percentile of dose and fluoroscopy time) and identification of potentially
patients overexposed to radiation (cumulative dose for 3 months that
exceed 20000 Gycm2). Secondly, analyze of patient doses per cardiologist and how they report to the local reference dose levels. In this way,
we are able to identify eventually deviations and find the corrective
solutions.
For example, table 1 shows the yearly variation of local reference values for
diagnostic procedures (CA) and therapeutic (PCI) in terms of KAP and
fluoroscopy time.
Procedure
Reference values
year
2009
year
2010
year
2011
year
2012
year
2013
diagnostic (CA)
therapeutic (CA + PCI)
diagnostic (CA)
KAP (Gy*cm2)
KAP (Gy*cm2)
fluoroscopy time
(minutes)
fluoroscopy time
(minutes)
23,0
44,0
5
24,7
36,6
6
18,2
50,5
5
18,1
49,5
5
17,7
45,5
6
16
11
16
17
17
therapeutic (CA + PCI)
The record of patient doses is a routine in our center and gives us the
possibility to have a better image of our practice and identify the ways to
optimize the activity.
ESTABLISHING NON CENTER-SPECIFIC EUROPEAN TRIGGER LEVELS IN
INTERVENTIONAL PROCEDURES USING TLDS AND GAFCHROMIC FILMS
J. Domienik a, E. Carinou b, O. Ciaj-Bjelac c, I. Clairand d, J. Dabin e, C. De
c h, M. Majer c, F.
Angelis f, J. Farah d, C. Huet d, H. Jarvinen g, R. Kope
k k, T. Siiskonen g, A. Trianni l, F.
Malchair i, A. Negri j, L. Nova
Kne
Vanhavere d, Z.
zevic m. a Nofer Institute of Occupational Medicine,
dz, Poland;
Radiation Protection Department, Sw Teresy 8, 91-348 Ło
Abstracts / Physica Medica 30S1 (2014)
b
Greek Atomic Energy Commission (GAEC), P.O.Box 60092, Ag. Paraskevi.
15310 Athens; Greece; c VINCA Institute of Nuclear Sciences (VINCA), P.O.
e
Box 522, 11001 Belgrade; Serbia; d Institut de Radioprotection et de Sûret
Nucl
eaire (IRSN), BP17, 92262 Fontenay-aux-Roses Cedex, France; e Belgian
Nuclear Research Centre (SCK-CEN), Boeretang 200, BE-2400 Mol; Belgium;
f
(ISS), Viale Regina Elena 299, 00161 Rome;
Istituto Superiore di Sanita
Italy; g Radiation and Nuclear Safety Authority (STUK), P.O. Box 14, 00881
Helsinki; Finland; h Institute of Nuclear Physics (IFJ - PAN), ul
w; Poland; i Centre Hospitalier
Radzikowskiego 152, PL-31-342 Krako
^pital, 4000 Li
Universitaire de Li
ege (CHUL), Avenue de l'Ho
ege; Belgium;
j
Istituto Oncologico Veneto (IOV), Via Gattamelata 64, 35124 Padova; Italy;
k
National Radiation Protection Institute (NRPI), Bartoskova 28, 140 00
Prague 4; Czech Republic; l Udine University Hospital (AOUD), ple S. Maria
della Misericordia, 15, 33100 Udine; Italy; m RuCer Boskovic Institute (RBI),
Bijenicka c. 54, 10000 Zagreb; Croatia
Background: EURADOS WG-12 is performing a feasibility study to establish European trigger levels which would inform physicians about potential risk of skin injuries during interventional procedures.
Materials and methods: Six European centers participate in the measurement campaign focusing on three interventional procedures associated with high exposure levels: PTCA (coronary angioplasty), NE (neuroembolisations) and CE (hepatic chemo-embolisations). In order to measure
MSD (maximum skin dose), different dosimetric systems were considered
(TLD grids, XR-RV3 Gafchromic films and TL foils). The study investigates
the performance and practicability of each dosimeter, compares the
different systems and investigates simultaneous use of films and TL systems. To setup trigger levels, the correlations between MSD and online
dose indicators are investigated by recording values of kerma-area product
(KAP), fluoroscopy time (FT) and cumulative air kerma at reference point
(CK).
Results: The comparison of dosimetric methods showed that both films
and TL systems are good tools for 2D mapping of skin dose. TLDs,
however, are point like and may miss the MSD. The measurements are
still on-going and up to 155 patients were already included. The
highest measured MSD were 7.7 Gy (NE), 3.9 Gy (CE) and 3.2 Gy (PTCA).
Good correlations were found between MSD and CK (for NE and PTCA)
or DAP (for CE). The preliminary trigger levels for ICRP skin dose
threshold (3 Gy) are 6 Gy and 3 Gy, respectively for NE and PTCA. For
10 NE procedures during which skin doses were measured simultaneously with films and TLDs, the quotient of MSD vary from 1.2 to 2.7.
These discrepancies would result in significantly different values of
trigger levels.
Discussion: For the selected procedures, MSD exceeded the threshold
of 3 Gy in 12% of the cases which justifies the need for trigger levels.
Preliminary results show that MSD evaluation is strongly dependent
on the dosimetry system. However, due to poor statistics in dual
dosimetry, further attempts are necessary to select the most accurate
way for MSD measurement. The promising method would be the joint
use of the TL foils (which proved to have the best characteristic) and
films.
DOSE REDUCTION IN ITERATIVE RECONSTRUCTED CORONARY ARTERY
CT: A MULTIVENDOR DYNAMIC PHANTOM STUDY
Niels van der Werf a, Marcel Greuter a, Martin Willemink b, Bronislaw
Abramiuc a, Tineke Willems a, Tim Leiner b. a University of Groningen,
University Medical Center Groningen, The Netherlands; b University of
Utrecht, University Medical Center Utrecht, The Netherlands
Iterative reconstruction (IR) in computed tomography (CT) coronary calcium scoring (CCS) may allow dose reduction compared to filtered back
projection (FBP). The purpose of the current study was to evaluate the
influence of dose on CCS with moving calcifications in IR CT for high-end
CT scanners of the four major vendors.
Two calcifications (equal volume 198.4 mm3, different mass 157.1, 38.5 mg)
were used in an anthropomorphic thorax phantom at 20 mm/s. A medium
sized patient extension ring and vendor recommended clinical protocols
3
were used. The phantom was scanned five times at full dose and 80% dose
reduction on Brilliance iCT (Philips), Aquilion One (Toshiba), Discovery
CT750HD (GE) and Somatom Definition Flash (Siemens). CCS was quantified
as Agatston scores with vendor software, with full dose FBP as reference.
For the 157.1 mg calcification full dose FBP resulted in CCS of 500 ± 45, 442
± 14, 529 ± 55 and 717 ± 31 for Philips, Siemens, GE and Toshiba respectively. At 80% reduced dose CCS was 625 ± 96, 552 ± 21, 665 ± 36 and 710 ±
30. Using IR CCS decreased with 7-15% to 527 ± 54, 476 ± 19, 614 ± 29 and
639 ± 27. For the 38.5 mg calcification full dose FBP resulted in CCS of 102 ±
12, 99 ± 15, 100 ± 7 and 112 ± 10. At 80% reduced dose CCS was 265±41,
157±11, 148±9 and 187±15. Using IR CCS decreased with 34-58% to
110±48, 90±5, 97±8 and 85±7.
Given these results, dynamic coronary calcium scores can be overestimated up to 157% at 80% reduced dose, which can be compensated for
up to 58% using iterative reconstruction, depending on calcification density and CT system.
PATIENT RADIATION DOSES DURING CONVENTIONAL AND COMPUTED
TOMOGRAPHY CORONARY ANGIOGRAPHY
Ioannis Pantos a, Sofia D. Kordolaimi b, Agapi Ploussi b, Demosthenes
Katritsis a, Efstathios P. Efstathopoulos b. a Department of Cardiology,
Athens Euroclinic; b 2nd Department of Radiology, Medical School,
University of Athens
Background: Coronary CT angiography (CCTA) is a noninvasive imaging
technique widely used for the assessment of coronary artery disease (CAD)
providing high diagnostic performance. However, CCTA remains an examination with high radiation exposure and its relevance to cancer induction remains a major concern. In response to this concern, various
techniques like the implementation of iterative reconstruction (IR) to
reduce radiation exposure in CCTA have been implemented.
Purpose: We sought to assess patient radiation exposure in computed
tomography coronary angiography (CTCA) in the new era of iterative
reconstruction (IR) and compare findings with conventional coronary
angiography (CCA).
Materials and methods: We retrospectively assessed dose indices of 76
CTCAs performed at two multidetector CT scanners one of which was
equipped with an IR algorithm (iDose4 by Philips) and 93 CCAs performed
at a conventional monoplane coronary angiography unit equipped with a
flat panel detector. CTCAs were performed with either prospective or
retrospective acquisition and with either a full or reduced tube currenttime product (mAs) protocol. Full mAs CTCAs were reconstructed using
conventional filter back projection (FBP) while reduced mAs CTCAs were
reconstructed using iDose4. CCAs without ventriculograms were performed by a routine acquisition protocol by a single highly experienced
operator. Patient exposure from CTCA and CCA was assessed by effective
dose which was calculated using published dose length product (DLP) and
dose area product (DAP) conversion factors.
Results: All exam inations were considered acceptable regarding imaging quality and diagnostic accuracy. In CTCAs reconstructed with FBP and
retrospective acquisition, effective dose was 15.0 ± 3.1 mSv (scanner 1)
and 16.28 ± 7.70 mSv (scanner 2) while with prospective acquisition
effective dose was 3.3 ± 1.1 mSv. Corresponding values for CCTAs
reconstructed with iDose4 and retrospective or prospective acquisition
were 8.5 ± 2.5 mSv and 2.4 ± 0.8 mSv accordingly. In CCA effective dose
was 6.3 ± 2.8 mSv.
Discussion: In CTCA prospective acquisition provides substantial dose
reduction which can be further accentuated with the use of IR. The combined application of prospective acquisition and IR enables CTCA to be
performed at a low dose while preserving good image quality and diagnostic accuracy.
MODEL OBSERVERS LOW CONTRAST DETECTABILITY PERFORMANCE AT
DIFFERENT KV LEVELS IN CT PHANTOM IMAGES
I. Hernandez-Giron a, b, A. Calzado b, J. Geleijns c, R.M.S. Joemai c, W.J.H.
edica. Universitat Rovira i Virgili (URV),
Veldkamp c. a Unitat de Física M
Spain; b Departamento de Radiología. Universidad Complutense de Madrid
4
Abstracts / Physica Medica 30S1 (2014)
(UCM), Spain; c Radiology Department. Leiden University Medical Center
(LUMC), The Netherlands
Purpose: To study low contrast detectability (LCD) performance of two
model observers in CT phantom images acquired at different kV levels. To
compare the results with humans in a 2-alternative forced choice experiment (2-AFC).
Materials and methods: Images of the low contrast module of the Catphan 500 phantom were acquired at different kV levels (80-100-135kV) in
a 320-row CT scanner (Aquilion ONE). The module contains three series of
objects (contrast series: 0.3, 0.5, and 1.0%, diameters: 2-15mm each). Two
model observers (non-prewhitening matched filter with an eye filter,
NPWE, and channelized Hotelling observer with Gabor channels, CHO)
were applied to automatically measure LCD.
Two human observers evaluated the three contrast groups visibility in 2AFC experiments. The proportion correct (PC; measure of detection
probability) was obtained for each object size, for all contrast series and kV
values. Psychometric fits [1] were used to calculate the smallest object
visible (l, related to a PC of 75%) for each condition. To match NPWE and
CHO with human performance, efficiency factors (h) were determined.
Bland-Altman analyses were performed to compare PC values obtained by
models and humans after correcting the models performance using h
values.
Results: The model observers reproduced the human LCD performance
trends, improving detectability with increasing object size, contrast and
kV. The visibility thresholds for humans (and 80-100 and 135 kV) were (1%
contrast: 2.72.11.6mm; 0.5% contrast: 4.63.42.8mm; 0.3% contrast:
6.44.84.5mm) (Fig. 1). Both models gave higher detectability values
than the average human observer. The calculated efficiencies (h) calculated
to match human results were 0.5 (NPWE) and 0.3 (CHO) respectively.
Bland-Altman plots showed good agreement between models and humans
after the efficiency correction. For CHO and all contrast results together,
the average difference D and the range of the differences D±2s (s, standard deviation) with regard to human PC results were D¼1.2%, D±2s
¼[-3.1%, 5.4%]. For NPWE (Fig. 2), the results were: D¼0.3%, D±2s¼[-4.2%,
3.6%].
Conclusion: An automated method to investigate LCD in CT based on two
different model observers was developed. The models can be useful tools
to predict human performance in CT low contrast detection tasks in a
standard phantom.
References:
[1] Hernandez-Giron I, Geleijns J, Calzado A, Veldkamp WJH. Automated
assessment of low contrast sensitivity for CT systems using a model
observer. Med Phys 2011;28:S25-S35.
Fig.2. Bland-Altman plot of proportion correct (PC) difference between human and NPWE
model observer after correcting by efficiency (h¼0.5) for all contrast groups and kV values.
PERFORMANCE COMPARISON OF DIFFERENT DR DETECTORS USING
SIMPLIFIED EDQE APPROACH
Dogan Bor a, Ahmet Guven b, Turan Olgar a, Ozlem Birgul b. a Ankara
University, Faculty of Engineering, Department of Physics Engineering,
Turkey; b Ankara University, Institute of Nuclear Sciences, Department of
Medical Physics, Turkey
Background: Modulation transfer function (MTF), noise power spectrum
(NPS) and detective quantum efficiency (DQE) which is calculated using
MTF and NPS are frequently used for the evaluation of detector performance in digital radiological imaging system. In recent years, a new metric,
effective detective quantum efficiency (eDQE), that includes scatter and
focal spot effects which changes with different clinical applications has
been introduced to evaluate the performance of the system as a whole.
Materials and methods: One method for the calculation of eDQE, is to
measure MTF, NPS, scatter factor (SF) and transmission factor (TF) and use
the expression:
eDQE ¼
MTFðu; vÞ2 :ð1 SFÞ2
NNPSðu; vÞ:TF:K:q
where q is the number of photons on detector per unit dose per unit area
and K is the detector entrance dose. In this method, SF and TF must be
measured separately in addition to MTF and NPS measurements.
We modified this method by eliminating the (1-SF)2 from the above equation
since it causes the over estimation of the scatter effect. The long tails of the line
spread function were taken into account in the MTF calculation without any
truncation and smoothing so that only the frequencies related to the scatter
were included. Consequently, the MTF measurements were simplified.
Results: In order to see the performance of the detectors for the clinical
studies PMMA blocks were placed close to detector and eDQEs were obtained for a variety of tube voltages and detector exposures. Detector DQEs
were also find at similar beam qualities.
Measurements were carried out on digital radiographic systems having flat
panel detectors manufactured by different vendors. The effects of scatter,
geometric magnification, beam quality and detector exposures were
investigated separately and degradation of detector DQE to eDQE with
these factors were compared for each system.
Discussion: The use of all the scatter data in the MTF calculation better
reflects the system performance in terms of eDQE approach. Elimination of
the separate scatter measurements with beam stop technique also speeds
up the test procedure.
This work is partially supported by TUBITAK 112T965 Research Grant.
DOSIMETRIC STUDY OF THE USE OF CBCT IN DIAGNOSTIC RADIOLOGY:
SINUS AND MIDDLE EAR
Fig.1. Psychometric fits of the average human as a function of object diameter for 0.5%
contrast and all kV. The visibility thresholds (l, related to PC¼75%) were obtained after
fitting to the psychometric function.
C. Saldarriaga Vargas a, D. Dierckx b, F. Rogge b, S. Lichtherte b, L.
Struelens a. a SCKCEN, Radiation Protection, Dosimetry and Calibration,
Boeretang 200, 2400 Mol, Belgium; b Controlatom, Department of Medical
Physics, Jan Olieslagerslaan 35, 1800 Vilvoorde, Belgium
Abstracts / Physica Medica 30S1 (2014)
Background: The use of cone beam computed tomography (CBCT) in
diagnostic radiology departments is increasing. Several discussions arise
whether some Multi Slice CT (MSCT) examinations can be replaced with
the CBCT application. High hopes are set regarding the dosimetric aspects
of CBCT: are patient doses in between those of conventional X-Rays and
MSCT? A dosimetric advantage of CBCT respect to MSCT has already been
reported in dentomaxillofacial radiology [1-5].
Materials and methods: In this study [6] effective dose and organ doses
were evaluated for two non-dental CBCT examinations: sinus and middle
ear. The dose obtained with a NEWTOM™ 5G CBCT device (QR srl, Verona,
Italy) was compared with the dose obtained with a MSCT Philips Brilliance
CT 64-slice (Philips Healthcare, Eindhoven, the Netherlands). Moreover, for
the sinus examination, a comparison with the dose obtained by projection
radiography (RX) using the Siemens Ysio X-ray device (Siemens Medical
Systems, Erlangen, Germany) was also performed.
Effective doses were estimated from thermoluminescent detector (TLD)
dose measurements in a Rando Alderson (RA) anthropomorphic phantom
and were compared against Monte Carlo (MC) simulations using the MCNPX
2.7.0 code [7] and the PCXMC [8] and CTDosimetry [9] software tools.
Results: Results show that the effective dose for the sinus examination is
more than 3 times higher with MSCT than with CBCT and about 5 times
lower with RX compared to CBCT (see Table 1.), while for the middle ear
examination the effective dose obtained with MSCT is almost 6 times
higher than that of CBCT (see Table 2.). Finally, a sensitivity study on the
size and position of the CBCT field of view (FOV) showed the influence of
these two factors on the dose received by the patient.
Table 1
Effective dose, E (mSv), obtained from measurements with the RA phantom and
from MC simulations using CT-Dosimetry, PCXMC, PCXMCrotation and MCNPX, for
the sinus examination.
CT
E (mSv)
CBCT
RX
RA
CT-Dos
RA
PCXMCrot
RA
PCXMC
MCNPX
0.333
0.208
0.102
0.088
0.020
0.017
0.020
Table 2
Effective dose, E (mSv), obtained from measurements with the RA phantom and
from MC simulations using CT-Dosimetry and PCXMCrotation, for the middle ear
examination.
CT
E (mSv)
CBCT
RA
CT-Dos
RA
PCXMCrot
2.329
1.951
0.396
0.186
References
[1] Loubele M., Bogaerts R., Van Dijck E., Pauwels R., Vanheusden S.,
Suetens P., Marchal G., Sanderink G., Jacobs R., Comparison between effective
radiation dose of CBCT and MSCT scanners for dentomaxillofacial applications.
Eur J. Radiol. 71, 461-468 (2009).
€ser Y., Peltola J., Kortesniemi M.
[2] Suomalainen A., Kiljunen T., Ka
Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography
scanners. Dentomaxillofac. Radiol. 38(6), 367e378 (2009).
[3] Ludlow JB., Ivanovic M. Comparative dosimetry of dental CBCT devices
and 64-slice CT for oral and maxillofacial radiology. Oral Surg. Oral Med. Oral
Pathol. Oral Radiol. Endod. 106(1), 106e114 (2008).
[4] Loubele M., Maes F., Jacobs R., van Steenberghe D., White SC., Suetens P.,
Comparative study of image quality for MSCT and CBCT scanners for dentomaxillofacial Radiology Application. Radiat. Prot. Dosim., 129, 222-226
(2008).
[5] Ludlow JB., Davies-Ludlow LE., Brooks SL., Howerton WB., Dosimetry of
3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G
and i-CAT. Dentomaxillofac. Radiol. 35, 219e226 (2006).
5
[6] Dierckx D., Saldarriaga Vargas C., Rogge F., Lichtherte S., Struelens L.
Dosimetric analysis of the use of CBCT in diagnostic radiology: sinus and
middle ear. Rad. Prot. Dos. http://dx.doi.org/10.1093/rpd/ncu117 (2014).
[7] Pelowitz DB., Durkee JW., Elson JS., Fensin ML., James MR., Johns RC.,
McKinney GW., Mashnik SG., Waters LS., Wilcox TA. MCNPX 2.7.0 Extensions, LA-UR-11-02295, (2011).
[8] STUK, Helsinky, Finland, A Monte Carlo program for calculating patient
doses in medical x-ray examinations. PCXMC version 2.0.1.4. Supplementary programs (2012).
[9] IMPACT Group, London, United Kingdom, ImPACT CT Patient Dosimetry
Calculator. Version 1.0.4 27/05 (2011).
COMPARATIVE PERFORMANCE EVALUATION OF CONTRAST-DETAIL IN
FULL FIELD DIGITAL MAMMOGRAPHY (FFDM) SYSTEMS USING IDEAL
(HOTELLING) OBSERVER VERSUS AUTOMATED CDMAM ANALYSIS
Ioannis Delakis a, b, Robert Wise b, Lauren Morris b, Eugenia Kulama b. aSidra
Medical and Research Centre, Doha, Qatar; bRadiological Sciences Unit,
Imperial College Healthcare NHS Trust, Charing Cross Hospital, Fulham
Palace Road, London, United Kingdom
Background and purpose: Image quality evaluation plays an important
role in ensuring and enhancing the diagnostic value of mammography.
Image quality is typically is assessed using images acquired with the
Contrast Detail mammography (CDMAM) phantom (1, 2). However,
reading CDMAM images can be time consuming and suffers from limited
statistics. Recent work tried to link automated readings with humanobserver performance, but results can be dependent on structural differences between CDMAM phantoms (3-4). The purpose of this work was to
evaluate detector performance for a range of full field digital mammography (FFDM) systems using both CDMAM and ideal (Hotelling) observer
analysis and ascertain whether the ideal observer methodology can offer
some advantages.
Methodology: Five FFDM systems were included in this study, which
differed with respect to generation, detector, tube technology, and Automatic Exposure Control (AEC) behavior, as shown in Tables 1 and 2. Detector performance was first analysed using CDMAM phantom
methodology, as described by European and British guidelines (1, 2). Detector performance was then re-evaluated using ideal observer analysis, on
the basis of previous work, generalising the definition of Hotelling
observer to include the effects of focal spot unsharpness, magnification
and scattering (5-9).
Results and discussion: Both methodologies identified an improvement
in the performance of new compared to old generation FFDM systems,
but, as seen in Table 3, results showed the ideal observer methodology to
be a more sensitive performance differentiator. In addition, as seen in
Fugure 1, ideal observer results showed lower variability than CDMAM
analysis results in intra-system evaluation. The CDMAM phantom used
for inter-system comparison in our study appeared to overestimate
threshold contrast detectability across all diameter details when
compared to CDMAM phantoms from other groups. CDMAM results were
also consistently higher than ideal observer results, reflecting a similar
behavior.
Conclusion: We have shown that the ideal observer methodology can
provide a more reproducible and performance-representative alternative
to CDMAM analysis, as it is shows lower variability and is not phantomspecific. The ideal observer methodology also requires fewer exposures
than CDMAM methodology, which can be of practical benefit for regular
quality control of FFDM systems.
Keywords: Digital Mammography, Quality Assurance, CDMAM, Hotelling
Observer, Ideal Observer, image quality
References
[1] Van Engen R, Young K, Bosmans H, Thijssen H. The European protocol
for the quality control of the physical and technical aspects of mammography screening. Luxembourg: Euref; 2006.
[2] Commissioning and routine testing of Full Field Digital Mammography
Systems. NHSBSP Equipment Report 0604. Sheffield: NHS Cancer
Screening Programmes; In press. Report No.: version 4.
6
Abstracts / Physica Medica 30S1 (2014)
[3] Young K, Alsager A, Oduko J, Bosmans H, Verbrugge B, Geerste T, et
al. Evaluation of software for reading images of the CDMAM test object
to assess digital mammography systems. In Proc. SPIE 6913; 2008.
69131C.
[4] Young KC, Cook JJH, Oduko JM, Bosmans H. Comparison of software
and human observers in reading images of the CDMAM test object
to assess digital mammography systems. In Proc. SPIE 6142; 2006.
614206.
[5] Kyprianou IS. A method for total x-ray imaging system evaluation. PhD
Thesis. Buffalo, NY: University of New York. 2004
[6] Kyprianou IS, Rudin S, Bednarek D, Hoffman K. Generalizing the MTF
and DQE to include x-ray scatter and focal spot unsharpness: application to a new microangiographic system. Med. Phys. 2005; 32(2): 613626.
[7] Kyprianou I, Ganguly A, Rudin S, Bednarek D, Gallas B, Myers K. Efficiency of the Human Observer Compared to an Ideal Observer Based on a
Generalized NEQ Which Incorporates Scatter and Geometric Unsharpness:
Evaluation with a 2AFC Experiment. In Proc. Soc. Photo. Opt. Instrum. Eng.;
2005. (5749) 251-262.
[8] Liu H, Kyprianou IS, Badano A, Myers KJ, Jennings RJ, Park S, et al.
SKE/BKE Task-based methodology for calculating Hotelling observer
SNR in mammography. In Proc. of the SPIE, Medical Imaging; 2009.
7258.
[9] Liu H, Badano A, Chakrabarti K, Kaczmarek R, Kyprianou I. Task specific
evaluation of clinical full field digital mammography systems using the
Fourier definition of the Hotelling observer SNR. In Proc. of the SPIE,
Medical Imaging; 2010. 7622.
Table 1
List of FFDM systems included in the study.
Manufacturer
System Type
Installation
AEC setting
GE Healthcare
GE Healthcare
Hologic
Hologic
Hologic
Senographe DS
Senograhe Essential
Selenia (Mo target)
Selenia (W target)
Dimensions
July 2007
August 2010
June 2007
March 2011
November 2010
Contrast
Standard
Autofilter
Autofilter
Autofilter
Table 2
Detector properties of FFDM systems included in the study.
Manufacturer
System Type
Detector Type
Size(cm)
Pixel
size (mm)
GE Healthcare
GE Healthcare
CsI (indirect)
CsI (indirect)
19x23
24x29
100
100
Hologic
Senographe DS
Senographe
Essential
Selenia (Mo target)
24x29
70
Hologic
Selenia (W target)
24x29
70
Hologic
Dimensions
Selenium
(direct)
Selenium
(direct)
Selenium
(direct)
24x29
70
Table 3
Average ratio of threshold detectability results (New-to-Old FFDM system) is less
than unity, indicating the superiority in perfor-mance of new compared to older
generation FFDM systems.
GE Sen.
Essential/
GE Senog. DS
CDMAM fit to
predicted
Hotelling observer
Hologic Selenia
(W)/ Hologic
Selenia (Mo)
Hologic
Dimensions/
Hologic
Selenia (Mo)
0.83
0.89
0.99
0.89
0.90
0.89
Fig. 1 Mean and standard deviation (error bars) of threshold detectability results using
both methodologies on the same FFDM system for five consecutive days.
SIMULATED ANNEALING APPLIED TO
OPTIMIZATION: A COMPUTATIONAL STUDY
IMRT
BEAM
ANGLE
Joana Dias a, b, Humberto Rocha b, Brígida Ferreira c, d, Maria do Carmo
Lopes c, d. a Faculdade de Economia, Universidade de Coimbra, Portugal;
b
Inesc-Coimbra, Portugal; c I3N, Departamento de Física, Universidade de
edica, IPOC-FG, EPE, Coimbra, Portugal
Aveiro, Portugal; d Serviço de Física M
Background: Electing irradiation directions to use in IMRT treatments is
one of the first and most important decisions to make in treatment
planning. Beam angle optimization (BAO) is a difficult problem to tackle
from the mathematical optimization point of view. It is highly non-convex,
and optimization approaches based on gradient-descent methods will
probably get trapped in one of the many local minima. Simulated
Annealing (SA) is a local search probabilistic procedure, inspired from the
process of annealing in metallurgy, where a material is heated and cooled
in a controlled way in order to increase the size of its crystals, reducing
possible defects. Beginning with any admissible solution, the SA algorithm
searches the current solution's neighborhood looking for a better one. If a
better solution is found, it becomes the current solution. If a worse solution
is found, it can nevertheless become the current solution with a given
probability that depends on the cooling schedule and will be higher in
early iterations, decreasing with the number of iterations. The possibility
of worsening the objective function value gives SA the possibility of
escaping from local minima.
Materials and methods: SA was applied to ten clinical examples of
retrospective treated cases of head-and-neck tumors signalized as complex cases where proper target coverage and organ sparing proved difficult
to obtain. The number of directions to use was considered fixed and equal
to 5 and 7. Different algorithm's parameters and neighborhood structures
were tested.
Results: SA can lead to solutions that significantly improve organ sparing,
even considering a reduced number of angles, without jeopardizing tumor
coverage.
Discussion: It has been proved that, under asymptotic conditions, SA will
converge to the global optimum. However, in real applications and with
computational time limits, SA converges to a high quality solution but with
no optimality guaranties. The quality of the solution depends on the algorithm’s parameters and especially on the neighborhood structure chosen. Smaller neighborhoods seem to be preferable to larger ones, and
dynamically dimensioned neighborhoods can present a good choice,
allowing for a compromise between exploitation and exploration of the
searchable surface.
A VOXEL BASED NTCP MODEL FOR TREATMENT PLANNING
Andreas
Richter,
Christoph
Bert,
Markus
Hecht,
Reinhold
Müller. University Hospital of Erlangen, Department of Radiation Oncology,
€tsstr. 27, 91054 Erlangen, Germany
Universita
Abstracts / Physica Medica 30S1 (2014)
Background: For a more precise prediction of side effects in organs at risks
(OAR) during radiation therapy it is beneficial to include biological information in terms of the Normal Tissue Complication Probability (NTCP). For
this purpose, a voxel based NTCP model was developed by our group [1].
The basic idea of this model is that every organ is assumed to be consisting
of minimal damageable volumes (MDVs). The surviving probability of
these MDVs is directly given by the linear-quadratic model. The NTCP is
calculated from the number of the surviving MDVs by the Poisson’s
statistics.
Further information is needed about the structure of the organ (parallel or
serial) and on its functional reserve representing the minimal surviving
percentage of the MDVs required for proper physiology. Serial organs are
modeled as a series of subunits each treated as a parallel organ.
Materials and methods: The model was already fitted to the published
data of Emami et al. [2] for lung, kidney, parotid glands and spinal cord [3].
In this work a comparison of the model outcome for the parotid glands
with clinical xerostomia data of patients treated at the University Hospital
of Erlangen will be presented.
Results: The clinical xerostomia scores are only determined by interviewing the patients, so they show large fluctuations over time and
depend also on the physician who did the examination. Nevertheless, at
least a trend that low (high) clinical xerostomia scores result in low (high)
model calculated NTCP values has been observed. In the most cases the
calculated NTCP values are close to 0 for a mean clinical score of 1
(defined as ”no complication”) and values close to 1 for a mean score 2
(“complication”).
In addition, a sensitivity analysis of the parameters of the voxel based
model is ongoing.
Discussion: The NTCP values obtained by the model are promising. More
data for a further evaluation are still necessary.
[1] R. G. Müller et al.: Voxel by voxel NTCP algorithm for inverse treatment
planning in IMRT and particle therapy, IFMBE Proceedings 14:1770 (2007).
[2] B. Emami et al.: Tolerance of normal tissue to therapeutic irradiation,
Int. J. Radiat. Oncol. Biol. Phys. 21:109 (1991).
[3] A. Richter et al.: Development of a voxel-based NTCP algorithm for
treatment planning, Int. J. Radiat. Oncol. Biol. Phys. 87 (Suppl.):S687
(2013).
SECONDARY DOSES TO HEALTHY TISSUES DURING PROTON THERAPY
TREATMENTS: INFLUENCE OF IRRADIATION PARAMETERS
A. Bonfrate a, J. Farah a, L. De Marzi b, S. Delacroix b, J. Fontaine b, J.
rault c, R. Sayah a, F. Trompier a, C. Lee d, W.E. Bolch e, I.
He
e Nucl
eaire,
Clairand a. a IRSN e Institut de Radioprotection et de Sûret
Service de Dosim
etrie Externe BP17, 92262 Fontenay-aux-Roses Cedex,
France; b Institut Curie e Centre de Protonth
erapie d’Orsay (ICPO) ^timent 101, 91898 Orsay, France; c Centre Antoine
Campus universitaire ba
Lacassagne (CAL) - Cyclotron biom
edical, 227 avenue de la Lanterne,
06200 Nice, France; d Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institute of Health, Bethesda, MD
20852, USA; e Departments of Nuclear & Radiological and Biomedical
Engineering - University of Florida, Gainesville, FL 32611, USA
Context: Owing to the Bragg peak dose deposition in depth, proton therapy allows accurate cancer treatments while sparing healthy surrounding
tissues. However, secondary neutrons are produced during treatment and
can deliver unwanted doses to surrounding normal organs thus increasing
the risk of secondary cancer. This paper investigates the variation of secondary neutron doses with tumor size and location as well as patient age
and morphology.
Materials/methods: Beam parameters are specifically adjusted to conform
the clinical beam to the tumor. As secondary neutrons are mainly generated in beam line elements, large variations in organ doses are expected
depending on the treatment configuration. Monte Carlo calculations were
thus used to determine secondary neutron doses to healthy organs while
simulating realistic intracranial treatments and using the series of pediatric and adult hybrid computational phantoms developed at the University of Florida and the US National Cancer Institute. The facility and the
beam line modeled are those from Institut Curie e Centre de
7
rapie d’Orsay. The considered beam line parameters include
Prontonthe
beam energy, modulation width, patient collimator aperture size, air gap
and compensator thickness. Moreover, the distance between the target
volume and healthy organs is also considered for each configuration.
Results: For a 1-year-old patient and considering an anterior-superior
beam projection simulating a craniopharyngioma treatment, calculations
show that increasing the proton beam range from 8 to 10.5 cm (162 MeV to
178 MeV) leads to an increase in secondary neutron doses by up to a factor
2.1 for the salivary glands. Similarly, changing the collimator aperture from
3 to 10 cm in diameter results in a dose increase by a factor 3 for the
salivary glands and by 1.4 to the bladder. Finally, neutron absorbed doses
decrease with increasing distance to the target volume regardless of beam
parameters. Namely, with a proton beam range of 8 cm, neutron dose per
therapeutic dose received by the salivary glands is 103 mGy/Gy while the
bladder received 22 mGy/Gy.
Conclusion: Secondary neutron doses are strongly influenced by beam
line parameters and patient morphology. For healthy organs, proton
therapy remains nonetheless an interesting technique when compared
against conformal or intensity modulated radiotherapy.
DOSE VOLUME HISTOGRAMS DATABASE, REPORTING AND ANALYZING
SOFTWARE FOR RADIATION THERAPY
A. Perez-Rozos, M. Lobato, I. Jerez Sainz, C. Jodar, M. Pamos. UGC Oncologia,
Hospital Virgen de la Victoria, Malaga, Spain
Background: Dose volume histograms are a key and valuable tool when
comparing treatment alternatives and as predictor of treatment outcomes
in radiotherapy. The high number of region of interest and target volumens
in actual radiotherapy makes necessary use specifics tools for reporting
and analyze of DVH. In this work we show a tool to maintain a DVH
database, to generate population based DVH and relevant statistics. Population based DVH will be used as reference in treatment planning process.
Materials and methods: We have used our DVH database with more than
8000 treatments to generate population DVH for several treatment sites.
DVHs for regions of interest and PTVs were analyzed calculating mean
histogram and 10% and 90% percentile histograms. Probability distribution
of relevant evaluation parameters were calculated using these data (i.e
V20, mean dose, NTCP…). Mean and percentile histograms are established
as reference histograms in our reporting tool, allowing the interactive
comparison of actual treatment DVH versus database. It is possible to
incorporate DVH from several treatment planning systems (Philips
Pinnacle, Varian Eclipse and Brachyvision, Elekta Monaco and Oncentra).
Results: Plotting database DVH allows to fast identify outliers, and observe
variability in OARs and homogeneity in PTVs. Use of this tool warrants for
high homogeneity clinical dosimetry, that is really important when
participating in clinical trials. With these data it is possible to correlate
treatment outcomes with planning data. Comparison of actual patient
with reference DVH is straightforward using our application. Volume at a
dose, dose at a volume, NTCP, EUD, mean dose are successfully calculated
using DVH data. Comparison allows visual and numeric evaluation of DVH
using per protocol standards. Treatment plans that deviate from population histograms will require specific and comprehensive quality assurance
to identify reason of such differences.
Discussion: Population DVH comparison allows for a higher level of
quality assurance of clinical dosimetry process and has proven to be a
useful research tool for radiation therapy. Outlier treatments are easily
identified. Study of population based DVHs allows identification of better
predictive parameters to correlate with clinical outcomes.
EVALUATION OF THE ACCURACY OF MONITOR UNITS (MU) OBTAINED
FROM A TREATMENT PLANNING SYSTEM USING THE ELECTRON
MONTE CARLO ALGORITHM.
Ingrid R. Marshall. Medical University of South Carolina, Charleston, SC, USA
Purpose/ Objective: Electrons are used routinely in breast treatments,
either for scar or cavity boosts. Monitor units (MU) derived from treatment
planning systems (TPS) can be significantly different from so called “hand
calcs” which are still widely used. The MUs determined by the Electron
8
Abstracts / Physica Medica 30S1 (2014)
Monte Carlo (EMC) algorithm can differ by more than 10%. Hand calc MUs
are derived from homogenous water tank measurements, while treatment
planning MUs are based on heterogeneous calculations. The accuracy of
dose and isodose distributions from the Eclipse's EMC calculation model is
investigated.
Materials and methods: A breast phantom routinely used for teaching selfexamination was placed on top of the Matrixx ion chamber array which
included 1cm solid water build up. Measurements were made to test the
accuracy of the system to account for both curvature and heterogeneity at 3
positions of the breast phantom, with and without 4cm Styrofoam inserted,
at 100SSD, using 5 electron energies, a 6x6 cone and fixed MUs. The
calculation model was also verified using a standard flat homogenous
phantom. The IBA Matrixx measurements were compared with EMC calculations using the CT of the phantom and an IMRT analysis tool.
international protocol is identified i.e. for new low energy X ray source for
brachytherapy, for medium energy X rays, for small size high energy X-rays
beams and for hadron especially for scanned beams. These new standards are
based on calorimetric and ion chamber techniques for which new developments are made. For high energy X-rays in radiotherapy, the possibility
to measure a new integral quantity similar to dose area product (DAP) is
evaluated. The characteristics i.e. directional and energy responses, perturbation factors, linearity, homogeneity and spatial resolution of the transfer
dosemeters and their calibration and reading protocols are studied to finally
propose robust protocol for in vivo dosimetry and quality controls including
the developments of new anthropo and semi anthropomorphic phantoms
and to evaluate the possibility for assessing absorbed dose to water at a point
in small beams; the following dosemeters, (ion chambers, silicon diode, CVD
diamond, ESR/Alanine, radio-chromic and storage film, EPID and gel has been
chosen in order to cover the need for point, 2D and 3D dose measurements.
MetrExtRT gathers 10 partners as presented in the list of authors, two
Researcher Excellence Grants (REG) for the development of passive Frike gel
d’Auverge e France)
dosimetry without diffusion after irradiation (Universite
and the first diamond detectors commercially available (Tor Vergata University - Italy) and up to now 12 collaborators from industry, oncology centres
and universities. The presentation lays emphasis on the gel dosimetry and the
DAP concept applied to external beam radiotherapy. More information can be
found on the website of the project: http://radiotherapy-emrp.eu
Ă
Results: The measured dose plane for fixed MUs at the 3 positions of the
breast phantom compared well when using the EMC model, even when
heterogeneity in the form of 4 cm Styrofoam was introduced.
For the MU calculations all fields were normalized to dmax. The MUs from
“hand calcs” were compared with the MUs derived from EMC calculations
using the flat phantom and the 3 breast phantom positions. In the case of
the flat phantom the calculated MUs were within 2% of the “hand calc”.
However, variations of up to 20% were observed, when calculating the MUs
using the breast model, with the eMC MUs being larger.
Conclusion: The results show that both the isodose distribution and absolute dose are well predicted by the treatment planning system. Therefore,
the MUs determined by the TPS system can be trusted and should be used.
METROLOGY FOR RADIOTHERAPY USING COMPLEX RADIATION FIELDS
e EMRP PROJECT
Jean-Marc Bordy a, Claus Andersen b, Ulrike Ankerhold c, Veronique
Dedieu d, Frank Delaunay a, Jacco De Pooter e, Jarolav Compell f, Simon
Duane g, Ralf-Peter Kapsch c, Antti Kosunen h, Gabor Machula i, Marco
Marinelli l, Hugo Palmans g, Maria Pimpinella j, Gianluca Verona
Rinati l, Jaroslav Solc k. a CEA, LIST, DM2I, Laboratoire National Henri
Becquerel LNE/LNHB, F-91191 Gif sur Yvette, France; b Danmarks Tekniske
Universitet, DTU, Bygning 101, DK-2800 Kongens Lyngby, Denmark;
c
Physikalisch-Technische Bundesanstalt, PTB, Bundesallee 100, D-38116
Braunschweig, Germany; d Universt
e d'Auvergne, UdA, France; e VSL B.V.,
Thijsseweg 11, NL-2629 JA Delft, Netherlands; f Slovak Institute of
63, SK-842 55 Bratislava, Slovakia,; g National
Metrology, SMU, Karloveska
Physical Laboratory, NPL, GB-TW11 0LW Teddington, Middlesex, United
Kingdom,; h Radiation and Nuclear Safety Authority, STUK, Laippatie 4, FI00880 Helsinki, Finland,; i Magyar Kereskedelmi Engedelyezesi Hivatal,
g 1534 Budapest, P.f.: 919 Hungary; j Istituto Nazionale di
sa
MKEH, Hato
Metrologia delle Radiazioni Ionizzanti, ENEA - CR Casaccia, Via
Anguillarese, 301, 00123 Roma, Italy; k Cesky Metrologicky Institut Brno,
degli Studi di
CMI, Okruzni 30, 63800 Brno, Czech Republic; l Universita
Roma Tor Vergata,Dipartimento di Ingegneria Industriale, Via del
Politecnico 1, 00133 Roma, Italy
Abstract: This presentation is intended to give an overview of the on-going
work of the MetrExtRT research project. It is funded by the European
Metrology Research Program (EMRP). It started the 1st of June 2012 for 36
months and covers radiotherapy based on medium- and high-energy X-rays,
high-energy electrons, electronic brachytherapy and scanned proton and
carbon ion beams. The project covers all the steps of the dose traceability from
the primary standards to the tumour dose. The first step is to develop new
primary standards where a lack of references complying with the
CLINICAL IMPLEMENTATION OF 3D EPID-BASED IN VIVO DOSE
VERIFICATION OF IMRT/VMAT TREATMENTS
B. Mijnheer, A. Mans, I. Olaciregui-Ruiz, R. Rozendaal, H. Spreeuw, M. van
Herk. Department of Radiation Oncology, The Netherlands Cancer Institute,
Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
Purpose: To elucidate the clinical implementation of our 3D in vivo
dosimetry method for daily patient-specific QA of IMRT/VMAT treatments.
Methods: A back-projection algorithm has been further developed and
implemented to enable automatic 3D in vivo dose verification of IMRT/
VMAT treatments using a-Si EPIDs. New software tools were clinically
introduced to allow automated image acquisition, to periodically inspect
the record-and-verify database, and to automatically run the EPID
dosimetry software. The comparison of the EPID-reconstructed and
planned dose distribution is done offline to raise automatically alerts and
to schedule actions when deviations are detected. These tools are able to
measure on the first day(s) of a treatment the 3D in vivo dose distribution
thus tracing clinically relevant errors. It should replace pre-treatment
verification, except for single fraction and large field treatments.
Results: The implementation of fully automated 3D EPID-based in vivo
dosimetry was able to replace pre-treatment verification for more than
90% of the patient treatments, which may safe resources for other purposes. The process has been fully automated and integrated in our clinical
workflow where over 3,500 IMRT/VMAT treatments are verified each year.
The results of the analysis are available a few minutes after delivery and
alerts are immediately raised, without any human intervention, when
deviations are outside clinical criteria. 3D in vivo dosimetry is able to detect
a number of patient-related errors (e.g. anatomy variations, changes in
treatment parameters between planning and delivery) that cannot be
traced with pre-treatment verification. 10 to 20% of the verified plans
needs inspection by a medical physicist, and about one out of 300 verifications requires consultation with the responsible radiation oncologist.
Patient treatment is then resumed, or postponed until a new improved
plan has been generated and verified.
Conclusions: The automatic offline solution facilitated the large scale
clinical implementation of 3D EPID-based in vivo dose verification of IMRT/
VMAT treatments.
IMPLEMENTATION OF THE AAPM TASK GROUP 119 REPORT FOR IMRT
COMMISSIONING ON A 3D DOSIMETRIC PHANTOM
Raphaela Avgousti a, Ioannis Floros a, Maritina Rouchota a, Christina
Armpilia a, Pantelis Karaiskos b, Maria Lyra a, Christos Antypas a. a 1st
Department of Radiology, Medical Physics Unit, Aretaieion Hospital,
Abstracts / Physica Medica 30S1 (2014)
University of Athens, Greece; b Laboratory of Medical Physics, School of
Medicine, University of Athens, Greece
Background: For IMRT commissioning in our department, the AAPM's TG119 Report was implemented on the Delta4 (Scandidos, Uppsala, Sweden)
to evaluate step-and-shoot IMRT plans and verify the dose distribution
using a 6MV linac photon beam.
Materials and methods: TG-119 recommends a set of test cases to assess
the overall accuracy of planning and delivery of IMRT treatments. Delta4 is
used for quality assurance of patient specific treatment delivery. It is a
cylindrical phantom consisting of two detector planes with p-type diodes
that can measure point doses. Seven TG-119 plans, including the respective
structure sets, were transferred on the Delta4 geometry. The respective
dose distributions for a 6MV photon beam from a Siemens Oncor
Impression linac with a multileaf collimator (82 leaves, 1cm thick) were
calculated in the Oncentra v4.3 (Nucletron, Elekta) treatment planning
system. Two preliminary tests were performed with simple parallelopposed fields irradiating the cylindrical phantom. Additionally, five more
tests with mock structures were planned and irradiated with IMRT fields.
Dose distribution for all test cases was calculated using a collapsed cone
convolution algorithm for optimization and final dose calculation. TG119’s
optimization goals were intended for all cases. For the acceptance of the
verification process, gamma criteria of 3% dose and 3mm distance to
agreement were used.
Results: The gamma index passing rate for all tests was measured higher
than 90%. Preliminary tests were measured 99.3% for anterior-posterior
and 99.6% for the bands test. For the IMRT cases, it was measured 97.5% for
multitarget, 99.6% for prostate, 98.5% for head and neck, 95.2 for the easy
C-shape and 90.3% for the harder C-shape test.
Discussion: TG119 structures and plans were easily transferred and
implemented on the Delta4 dosimetric phantom. For all test cases the
gamma index passing rate was measured higher than 90%. Delta4 phantom
has proven to be fast applicable and reliable for the step-and-shoot IMRT
commissioning following the TG119 recommended tests.
ORGAN MOTION IN CHILDREN
PRECISION RADIOTHERAPY
DURING
IMAGE-GUIDED
HIGH-
Arjan Bel, Rianne de Jong, Raquel Davilo Fajardo, Rasch Coen, Tanja
Alderliesten. Academic Medical Center, Meibergdreef 9, 1105AZ,
Amsterdam, The Netherlands
Background: In image-guided radiotherapy accurate knowledge of organ motion is of the utmost importance. Especially for children, an
inadequate margin definition can result in severe consequences: a
decreased local control caused by a geographic miss of the tumor or an
increased risk of late effects from unnecessary radiation to healthy
tissues.
Organ motion in adults has been widely analyzed, but quantitative data for
children is extremely sparse. The aim of this study is to quantify kidney and
diaphragm interfraction motion in children during radiotherapy.
Materials and methods: Eight patients (age: 5-16 years) who underwent a
cranio-spinal axis irradiation were included. Cone Beam CTs (CBCTs) were
acquired during on the average 5 treatment sessions (out of 15) per patient. Per treatment session, three CBCTs were acquired, including the
entire spinal cord and brain.
CBCTs were analyzed using Elekta Synergy (version 4.5). Patients were first
registered using bony anatomy. Subsequently, each kidney was registered
separately with respect to the bony anatomy. Similarly, the diaphragm
position was measured in the caudal-cranial (CC) direction.
Interfraction motion was quantified in terms of overall mean and standard
deviations (SDs) of the systematic (S) and random (s) translations in the
three orthogonal directions (kidneys) and solely the CC-direction (diaphragm). Interpatient variation was analyzed by considering the range of
mean translational deviations per patient.
Results: Kidney motion could be measured on all CBCT datasets. The
largest kidney motion was in the CC direction (Table 1). For the other directions, the SDs ranged from 1mm to 3mm; overall means were 1mm or
less. The mean translational deviations per patient ranged from -11mm to
2mm for the right kidney and -4mm to 5mm for the left kidney in the CCdirection and were smaller for the other directions.
9
Diaphragm motion was measured for six patients, due to breathing artifacts in the reference CT. The magnitude was comparable to the kidney
deviations (Table 1).
Discussion: Most interfraction kidney motion during radiotherapy
occurred in the CC-direction. The large interpatient variation calls for daily
imaging and setup corrections where differences between left and right
kidneys are taken into account.
Table 1
Mean and standard deviations for both kidneys and the diaphragm. LR¼left-right,
CC¼caudal-cranial and AP¼anterior-posterior.
Right kidney
Mean
S
s
Left kidney
Diaphragm
LR (mm)
CC (mm)
AP (mm)
LR
(mm)
CC
(mm)
AP
(mm)
CC
(mm)
0.0
1.4
1.7
-3.4
5.4
3.6
0.0
2.5
2.8
0.0
2.2
2.2
0.1
3.4
3.1
0.0
2.7
2.5
-1.6
4.6
3.3
VIRTUAL DICOM-CT BASED PHANTOMS FOR THE ASSESSMENT OF
RADIATION THERAPY TPS VOLUMETRIC ACCURACY
L. Petrokokkinos a, A. Moutsatsos a, E. Pappas a, E. Pantelis a, P.
Karaiskos a, b, P. Papagiannis a. a Medical Physics Laboratory, Medical
School, University of Athens, 75 Mikras Asias, 11527 Athens, Greece;
b
Gamma Knife Department, Hygeia Hospital, Kifisias Avenue and 4
Erythrou Stavrou, Marousi, 15123 Athens, Greece
Background: In modern radiotherapy, 3D imaging techniques are coupled
with advanced irradiation techniques to deliver complex dose distributions intending to maximize the coverage of, usually complex, target
shapes while sparing surrounding healthy tissues and thus to provide the
highest therapeutic ratio. The decision on the optimal plan to be used for
treatment is based on clinical indices (such as DVH), which in turn are
based on the calculation of volumes of the target and surrounding organs
at risk. The finally calculated index’s accuracy partially depends on the
volumetric calculation accuracy.
Materials and methods: DICOM-CT based virtual phantoms were developed to be used to quantify the volumetric calculation uncertainty in several
TPSs used in modern 3D radiotherapy techniques (GammaPlan, MasterPlan,
Eclipse). Several, simple geometrical shapes (spheres, cylinders, truncated
cones, parallelepipeds and oval-shaped volumes), mathematically defined
with predetermined dimensions, were used to roughly simulate typical organs at risk and targets (such as optic nerves, spinal cord, nodes, eyes, metastases, rectum, prostate, etc.). The phantoms were subsequently written in
DICOM-CT files using specially developed MATLAB routines, resulting in two
sets simulating the head and the pelvic region. Finally, each structure’s TPS
calculated volume was compared with its actual volume.
Results & Discussion: The accuracy of volume calculation heavily depends
on the scanning parameters i.e. the way each shape is discretized, written
in a DICOM file, delineated and finally defined in space. Thus the structures
comprising each phantom were chosen to be of several different sizes and
shapes, while the designed phantoms were written in DICOM-CT format
using different discretization grids in terms of size and direction.
Smaller voxel size, finer slice thickness and smaller slice spacing were
found to increase the TPS volume calculation accuracy. Moreover the shape
and size of each structure play a major role, as well as the discretization
angle, the gray level differences of structures of interest relative to surrounding tissue and noise levels.
Research implemented within framework of Action «Supporting Postdoctoral Researchers» of Operational Program “Education and Lifelong
Learning” (Action's Beneficiary: General Secretariat for Research and
Technology), co-financed by ESF and the Greek State.
4D CBCT IMAGE GUIDANCE IN SBRT FOR LUNG TUMORS
A. Perez-Rozos, A. Roman Jobacho, I. Jerez Sainz, I. Garcia Rios, A. Otero, M.
Lobato, J.C. Ramirez Ros, C. Jodar, J.A. Medina Carmona.
10
Abstracts / Physica Medica 30S1 (2014)
Introduction and objective: To analyze 4D image guided accuracy and
dose volume histograms in SBRT for lung tumors.
Materials and methods: The treatment of forty patients with SBRT in lung
cancer using 4D image guidance are analyzed in this work. Patients are
inmovilized employing an arm support, knee fix and a dampening system.
The respiration correlated 4D CT is used to delineate gross tumor volume
(GTV) in 0% inspiration phase, this GTV is therefore propagated to eight
other phases with autocontouring tools and combined to create an internal
target volume (ITV). Comparing center of mass of GTV in every respiratory
phase with respiratory curves a set of CT images are chosen as reference. In
this reference CT organs at risk are contoured and it is selected to match in
the daily image guided radiotherapy (IGRT). IGRT using anatomy fiducials
respiration correlated 4DCBCT (symmetry xvi, Elekta) with automatic
registration of the planning reference CT is used to setup patient in every
treatment session. Results were compared for three registration techniques: 3D CBCT using mean ITV and soft tissue registration, 4dCBCT
clipbox and bone anatomy registration (4D bCBCT), and 4D soft tissue
registration using a 0.5 cm mask from ITV (4D mCBCT).
Results: Significant differences in ITV localization were observed between
4D mCBCT and the other modalities, up to 3.1 mm ± 1.2 mm (3D vector).
The differences between 4D bCBCT and 4D mCBCT are closer than 4DbCBCT
and 3D CBCT. These differences are larger when respiratory amplitude
increase. Mean respiratory amplitude was 6.8 mm ± 4.0 mm when
measured in simulation CT, in agreement with 6.2 ± 3.8 mm when
measured in 4D CBCT. Visual comparison of reference respiratory curve
and treatment daily respiratory curve makes possible to asses reproducibility of patients and tumor position reproducibility. Interobserver variability was reduced using 4D mCBCT and soft tissue automatic registration.
With this protocol we can assert that interpatient variability in dose volume histograms is due mainly to treatment planning technique and tumor
volume definition, and not directly correlated with motion amplitude.
Conclusions: Respiration correlated 4D CBCT with soft tissue registration
improves accuracy of IGRT because of the more precise target localization in
the presence of respiratory motion, allowing the comparison of reference
respiratory curve with treatment respiratory curve. Moreover, the system
(symmetry xvi, Elekta) enables the realization of 4D CBCT without external
surrogates with good correlation with reference 4D CT using external sensors.
PILOT DOSE INTERCOMPARISONS OF 3D AND 4D ADVANCED LUNG
RADIOTHERAPY
D.I. Thwaites a,b, C.R. Hansen a,c, M. Kafrouni a, M. Caloz a, Q. Leturgie a, S.
Corde d, S. Downes d, J. Barber a, e, J. Sykes a, b, P. Juneja a, J.
Lehmann a. a Institute of Medical Physics, School of Physics, University of
Sydney, Australia; b Medical Physics, Leeds Teaching Hospitals and
University of Leeds, UK; c Radiation Physics, Odense University Hospital,
Denmark; d Medical Physics, Prince of Wales Hospital, Randwick (Sydney),
NSW, Australia; e Medical Physics, Nepean Hospital, Kingswood (Penrith),
NSW, Australia
As part of an evaluation of advanced radiotherapy (RT) technology, a
number of pilot intercomparisons have been developed and carried out of
planning and ‘treatment’ delivery for advanced lung treatments ( FFF
beams, VMAT, SBRT and 4D RT, etc). There are few, or no, reported audits/
intercomparisons of many of these combinations.
Four main studies are involved, mainly on 6MV beams:
i) An SBRT plan parameter comparison across 6 combinations of linac and
TPS, using FFF and FF beams; for three lung patients, having targets: close
to chest wall; close to bronchial tree; more central in the lung.
ii) A consistent Arccheck-based dose delivery intercomparison of these
plans; currently on-going, with tolerances of 3%/3mm on distribution, 3%
on isocentre dose.
iii) An end-to-end test of 4D planning and delivery in 5 centres following
their current (different) standard approaches, using an in-house developed
4D thorax phantom, with a variable movement lung ‘tumour’. A mini-ionchamber was used (5% tolerance).
iv) The latter was extended to test 4D dose distributions, using a modified
‘target’ with radiochromic film in multiple planes; currently undergoing
initial testing.
Results have been encouraging:
i) differences in plan quality between FF and FFF were small. Protocol violations appeared to inversely correlate with clinical SBRT VMAT experience (up to a factor of 6);
ii) initial results indicate high Arccheck gamma passing rates, but some few
% average differences in absolute doses, currently under investigation.
iii) all 4D measurements were within the pre-determined 5% tolerance,
regardless of equipment, methods or techniques.
iv) static and small amplitude 4D dose distributions pass dosimetric
testing at acceptable levels, but more significant problems are observed for
greater amplitudes of motion, currently under investigation.
This work provides initial testing and feasibility/pilot studies of audit/
intercomparison phantoms and methods for 3D and 4D advanced RT
treatments. This is initially mainly for lung treatment but is extendable to
other sites and linkable to IGRT audits. Once tested, each system is gradually being used across NSW RT centres to test the implementation of
advanced RT methods. The work has potential for use as the basis of
development of national audits.
OBSERVATIONS ON MR-LINAC SYSTEMS AND RATIONALE FOR MR-LINAC
USE: THE AUSTRALIAN MR-LINAC PROJECT AS AN EXAMPLE
D.I. Thwaites a, b, P. Keall c, L. Holloway d, J. Sykes b, e, V. Cosgrove e. a Institute
of Medical Physics, School of Physics, University of Sydney, Australia;
b
Medical Physics, Leeds Teaching Hospitals and University of Leeds, UK;
c
Radiation Physics Lab, Medical Faculty, University of Sydney, Australia;
d
Medical Physics, Liverpool Cancer Therapy Centre, Liverpool (Sydney),
Australia; e Medical Physics, St James’s Institute of Oncology, Leeds Teaching
Hospitals. Leeds, UK
Image guided radiotherapy (IGRT) at the point of treatment is now widely
available in RT centres, based mainly on 2D and 3D x-ray systems, but with
ultrasound and other systems also used. MRI can provide excellent soft
tissue imaging and the potential for functional imaging and a number of
hybrid systems are being developed with MR in the RT treatment room for
imaging at the point of treatment. Notable examples are the pioneering
MR-linac work at Utrecht and the Viewray system combining MRI with Co60 radiation sources, now in clinical use. The University of Sydney in
partnership with Liverpool Hospital, is developing an MR-linac system to
investigate comparative performance of in-line and perpendicular (to the
magnet bore) systems, in a project lead by Paul Keall. The rationale of MRlinac use generally and the potential of the different layouts and systems is
reviewed and discussed.
The literature on a range of approaches for combining MRI imaging and
radiotherapy treatment systems is reviewed, to summarise the different
systems, their status, their potential advantages and disadvantages and
their intended development. The Australian system (6 MV linac, 1T magnet) is described in more detail along with the comparative rationales and
likely advantages and disadvantages of in-line and perpendicular systems.
Results. Pros and cons of the different systems are significant, but all provide
the advantages of MRI imaging, although with different strength magnets
and hence different potential. The likely advantages of the in-line mode in
the Australian system include benefits when considering effects on the linac,
although the layout requires the patient to be rotated, with potential organ
changes to be assessed and compensated for. Electron transport effects to
the patient and in the patient between the two modes are mixed.
Discussion and conclusion. MR-linacs have the potential for improved
IGRT and functional IGRT, the latter linked to biological targeting and dose
painting. Some systems are in clinical use or close to clinical use. Their
wider implementation is likely to follow, leading to a new paradigm in
IGRT.
MEDICAL DOSIMETRY WITH A RL/OSL PROTOTYPE: 6 MV PHOTON
BEAMS
L.F. Nascimento a,b, d, F. Vanhavere b, Y. De Deene b, c, D. Verellen d. a Gent
University, Department Radiotherapy and Experimental Cancer Research,
De Pintelaan, 185, 9000 Gent, Belgium; b SCKCEN Belgian Nuclear
Research Centre, Boeretang 200, Mol, Belgium; c Institute of Medical
Physics, School of Physics e University of Sydney, Australia; d University of
VUB, UZ Brussel, Radiotherapie, Groep Medische Fysica, Brussels, Belgium
Abstracts / Physica Medica 30S1 (2014)
Contemporary therapeutic radiation oncology treatments require the delivery of highly localized doses of radiation to well defined target regions
inside the patient. The efficacy of the radiation treatment, however, requires knowledge of the absorbed dose in the organ of interest to better
than ±5% as there is a higher risk of local recurrence or complications with
incorrect exposure. Furthermore, since it is inevitable that healthy organs
and tissue will also be exposed during treatment, overexposure increases
the risk of secondary cancers.
International regulations [1, 2] have been introduced to adapt to the fast
introduction of new radiotherapy technologies and demand an improvement of in vivo dosimetry. Ideally, a real-time in vivo dosimeter would
measure absorbed doses during radiotherapy.
Optical stimulated luminescent (OSL) dosimeters, using the high sensitive material Al2O3:C, have been successfully used for measuring whole
body doses that result from exposure to high energetic photon and beta
radiation. OSL dosimeters have also been introduced in medical dosimetry of low and high LET beams [3, 4]. Al2O3:C detectors can also be used
as real time dosemeters, because the emitted stimulated light can be
guided via light fibers to a remotely placed photomultiplier tube.
Furthermore, during exposure to ionizing radiation Al2O3:C emits radioluminescent light (RL), of which the intensity is proportional to the dose
rate [5].
In this study, we investigated the dosimetric response of an optical fibre
coupled Al203:C RL/OSL dosemeter prototype. In our prototype, a PMMA
fibre is coupled to an Al2O3:C detector composed of microparticles of
Al2O3:C with diameters ranging from 5 mm to 35 mm dissolved in a photocurable polymer.
The RL/OSL dosimeter prototype is a portable and robust instrument that
has been developed for the routine assessment of patient exposure to
ionizing radiation during radiotherapy treatments. The design principles of
hardware and software are described elsewhere [6]. In this study, we
present the results obtained using radioluminescence (RL) from Al2O3:C
irradiated with a 6 MV linear accelerator (Compact, Elekta, Crawly) and
preliminary results obtained using optically stimulated luminescence
(OSL).
The dose rate dependence was assessed by varying the photon flux (MU/
min) of the linac, effectively changing the pulse rate and keeping the dose
per pulse fixed. It was found that the RL measured dose response
demonstrated low dose-rate dependency, to within 1%. The dose response
was found to be linear in a dose range from 0.1 up to a dose of 6 Gy, with
reproducibility below 0.5%.
The dosimeter is benchmarked by evaluating the ability to measure depthdose distributions and lateral dose profiles accurately. RL derived dose
profiles have been compared with dose profiles measured with a standard
ion chamber (PTW). Depth-dose distributions in water were acquired for a
6 MV photon beam using a 1010 cm2 field, set at 350 MU/min, corresponding with 3.5 Gy/min at 10 cm depth. All data have been normalized
to the depth-dose maximum. The RL measured dose agreed with the
ionization chamber measured dose to within 1% (1 SD) for depths from 0.5
to 20 cm.
Lateral dose profile was set at 350 MU/min (3.5 Gy/min at depth 10 cm),
using a 10x10 cm2 field size. Differences between measured RL and ion
chamber are within 1.5% for de direct beam and 5% in the penumbra
region.
These results show that the RL/OSL detector system makes it suitable for
measurements of depth and lateral dose distributions in clinical photon
beams.
Furthermore, basic characteristics of OSL in irradiated fibers with Al2O3:C
for dosimetry in therapeutic 6 MV photon beam were investigated.
References
[1] International Commission on Radiological Protection, 2000. Prevention
of accidental exposures to patients undergoing radiation therapy. ICRP
Publication 86. Ann. ICRP 30, 1e70.
[2] IAEA Human Health Reports 8, 2013. Development of Procedures for In
Vivo Dosimetry in Radiotherapy. IAEA Publication.
[3] Viamonte, A., Rosa, L. A., Buckley, L. A., Cherpak, A., & Cygler, J. E. (2008).
Radiotherapy dosimetry using a commercial OSL system. Medical Physics 35.
[4] Akselrod, M.S., Lucas, A.C., Polf, J.C., McKeever, S.W.S., 1998. Optically
stimulated luminescence of Al2O3. Radiat. Meas. 29, 391-399.
11
[5] Marckmann CJ, Andersen CE, Aznar MC, Bøtter-Jensen L. Optical fibre
dosemeter systems for clinical applications based on radioluminescence
and optically stimulated luminescence from Al2O3:C. Radiat Prot Dosimetry 120(1-4), 28-32.
[6] Nascimento, L. F, Vanhavere, F, Boogers, E, Vandecasteele, J, De Deene, Y.
2014. Medical Dosimetry Using a RL/OSL Prototype. Radiation Measurements.
ION BEAMS OF THERAPEUTICAL ENERGY ON PMMA PHANTOMS
MEASUREMENTS IN VIEW OF AN INNOVATIVE DOSE PROFILER
REALIZATION FOR ON LINE MONITORING IN HADRONTHERAPY
TREATMENTS
F. Bellini a, b, l, F. Collamati a, b, l, E. De Lucia c, l, R. Faccini a, b, l, F.
Ferroni a, b, l, P.M. Frallicciardi a, e, l, M. Marafini a, e, l, I. Mattei c, i, l, S.
V.
Patera b, d, e, l,
L.
Piersanti c, d, l,
D.
Pinci b, l,
A.
Morganti b, l,
Russomando a, b, f, l, A. Sarti c, d, l, A. Sciubba b, d, l, E. Solfaroli Camillocci f, l, C.
di Roma, Roma,
Voena a, b, l. a Dipartimento di Fisica, Sapienza Universita
Italy; b INFN Sezione di Roma, Roma, Italy; c Laboratori Nazionali di Frascati
dell’INFN, Frascati, Italy; d Dipartimento di Scienze di Base e Applicate per
di Roma, Roma, Italy; e Museo Storico della
Ingegneria, Sapienza Universita
Fisica e Centro Studi e Ricerche “E. Fermi”, Roma, Italy; f Center for Life
Nano Science@Sapienza, Istituto Italiano di Tecnologia, Roma, Italy;
i
di Roma, Roma,
Dipartimento di Matematica e Fisica, Roma Tre Universita
Italy; l Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza
di Roma, Roma, Italy
Universita
Hadrontherapy is a technique that uses accelerated charged ions for cancer
treatment. The high irradiation precision and conformity achievable during hadrontherapy treatments allow the tumor control while sparing the
surrounding healthy tissues. The improved spatial selectiveness required
the development of a new dose monitoring techniques. It has been proved
that secondary protons emitted at large angles can be used to monitor
Bragg Peak (BP) position and the related dose release. In this contribution
we present the measured flux and energy spectra for secondary particles
produced by 12C He and O ion beams of therapeutical energy impinging on
PMMA phantoms. We found that the rate of produced protons is large
enough to provide the track sample needed for a fast online monitor
operating during a typical treatment with the required O(mm) spatial
resolution. A clear correlation between the proton generation region and
BP position has been measured.
In this work we also discuss a novel hadrontherapy monitor (DoseProfiler)
whose technology is based on the backtracking of secondary charged
particles and prompt photons emitted during the irradiation of the patient,
allowing for a precise reconstruction of the BP position and a measurement of the released dose. The DoseProfiler combines a tracker detector
made of scintillating fibers and a calorimeter built with pixelated LYSO
crystals, for gamma detection and energy measurements. The six tracker
squared layers, built from two orthogonal planes of squared scintillating
fibers, will provide the particle direction information, while the LYSO
crystals will measure the particle energy.
PROTON RADIOGRAPHY IMAGING TOOL TO IMPROVE A PROTON
THERAPY TREATMENT
N. Ghazanfari a, M.-J. Van Goethem b, M. Van Beuzekom c, T. Klaver c, J.
Visser c, S. Brandenburg a, A.K. Biegun a. a KVI-Center for Advanced
Radiation Technology, University of Groningen, The Netherlands;
b
Department of Radiation Oncology, University Medical Center, University
of Groningen, The Netherlands; c National Institute for Subatomic Physics
(Nikhef), Amsterdam, The Netherlands
Background: Radiotherapy is one of the most effective and a common
method in cancer treatment. Typically in clinics, patients are treated
with photons. Treatment with charged particles, mostly protons, due
to their highly localized dose deposition, have a significant advantage
over the commonly used photons in achieving a sufficient radiation
dose to the tumor area to ensure complete tumor destruction, while at
the same time minimizing the dose to the surrounding healthy tissue
[1].
12
Abstracts / Physica Medica 30S1 (2014)
The quality of treatment with protons critically depends on accurate
predictions of the proton stopping powers of the traversed tissues.
Nowadays, proton treatment planning is based on stopping power information derived from X-ray Computed Tomography (CT) images. The conversion of HU values from the CT to proton stopping powers has systematic
uncertainties in the calculated proton range in a patient of approximately
3-4% and even up to 10% in regions containing bone [1-7]. A direct measurement of the proton stopping power by transmission radiography of
high-energy protons will make it possible to reduce significantly these
uncertainties.
Materials and methods: Higher energy of a proton beam, compared to a
therapeutic beam, minimizes the multiple scattering of protons in the
traversed tissues [8-13]. By measuring both the energy loss and the
angular deviation from the original path of each proton, the two complementary radiographs can be obtained. The combination of the energy
and scattering radiographs delivers the complete information about the
proton paths.
In presented studies, the novel micro time projection chambers detectors,
being developed at Nikhef, are used in the radiography experiment, which
has been performed on phantoms with the double scattered proton beam
of 150 MeV at the AGOR cyclotron. The experiment was simulated with the
Geant4-based simulation package, TOPAS [14].
Results: The first experimental and simulated proton energy radiographs
have been obtained for the same geometry with different density materials. The scattering radiographs are being analized.
Discussion: It is concluded that both experimental and simulated proton
energy radiographs are in a good agreement. Further analysis merging
both types of radiographs is ongoing to finally obtain the accurate values of
proton stopping powers.
[1] Plautz, T. et al.: 200 MeV Proton Radiography Studies with a Hand Phantom Using a Prototype Proton CT Scanner, IEEE NSS/MIC (2012) R04-R24
[2] Schneider, U., Pedroni, E., Lomax A.: The calibration of CT Hounsfield units
for radiotherapy treatment planning, Phys. Med. Biol. 41 (1996) 111-124
[3] Schneider W., Bortfeld T., Schlegel W.: Correlation between CT numbers
and tissue parameters needed for Monte Carlo simulations of clinical dose
distributions, Phys. Med. Biol. 45 (2000) 459-478
[4] Paganetti, H.: Range uncertainties in proton therapy and the role of
Monte Carlo simulations, Phys. Med. Biol. 57 (2012) R99-R117
[5] Landry, G. et al.: Deriving concentrations of oxygen and carbon in human tissues using single- and dual-energy CT for ion therapy applications,
Phys. Med. Biol. 58 (2013) 5029e5048
[6] Schneider, U., Pedroni E.: Proton radiography as a tool for quality
control in proton therapy, Med. Phys. 22(4) (1995) 353-363
[7] Cirrone, G. et al.: The Italian project for a proton imaging device, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 576 (2007)
194-197
[8] I. Rinaldi, “Investigations of novel imaging methods using therapeutic
beams”, PhD, University of Heidelberg, Germany (2011)
[9] U. Schneider and E. Pedroni, “Multiple Coulomb scattering and spatial
resolution in proton radiography”, Med. Phys. 21, 1657-1664 (1994)
[10] H. Ryu, E. Song, J. Lee, and J. Kim, “Density and spatial resolutions of
proton radiography using a range modulation technique”, Phys. Med. Biol.
53, 5461-5468 (2008)
€kel, and K. Parodi,
[11] I. Rinaldi, S. Brons, J. Gordon, R. Panse, B. Voss, O. Ja
“Experimental characterization of a prototype detector system for carbon
ion radiography and tomography”, Phys. Med. Biol. 58, 413-427 (2013)
[12] R.W. Schulte, V. Bashkirov, M.C.L. Klock, T. Li, A.J. Wroe, I. Evseev, D.C.
Williams, T. Satogata, “Density resolution of proton computed tomography”, Med. Phys. 32, 1035-1046 (2005)
[13] V. Denyak, S. Paschuk, H. Schelin, R. Rocha, J. Setti, M. Klock, I. Evseev,
O. Yevseyeva, “Dose energy dependence in proton imaging”, Nucl. Instr.
Meth. Phys. Res. A, 652, 747-750 (2011)
[14] Perl, J. et al.: TOPAS-An innovative proton Monte Carlo platform for
research and clinical applications, Med. Phys. 39 (2012) 6818-6837
EXPLORING NEW PATHS IN PARTICLE THERAPY: A MONTE CARLO
STUDY ON THE USE OF SPATIAL FRACTIONATION OF THE DOSE
C. Peucelle, I. Martínez-Rovira, Y. Prezado. IMNC e UMR 8165, IN2P3-CNRS,
Universit
e Paris 7, Universit
e Paris 11, Orsay, France
Purpose: In order to overcome the current limitations of radiation
therapy (RT), a new irradiation approach was explored. It combines the
well-established healthy tissue sparing of minibeam radiation therapy
(MBRT) [1,2] and the high dose conformality of particle therapy. In
particular, this new concept might trigger the re-discovery of the use of
“very” heavy-ions (Ne and heavier) in therapy. Indeed, despite their
very high effectiveness in the treatment of hypoxic radioresistant tumours, their use was discarded due to important toxicity in healthy
tissue [3].
Materials and methods: Dose distributions were evaluated by mean of
the GATE (v.6.1)/Geant4 Monte Carlo simulation platform [4]. Arrays of
minibeams (700 mm 2 cm) of five different heavy-ions (O, Ne, Si, Ar,
Fe), covering a 2 2 cm2 area, impinged on a cylindrical water phantom mimicking a human head (16 cm high and 16 cm diameter).
Realistic beam divergences were considered. Beam energies were
chosen so that the Bragg peak was located at 8 cm-depth, which was
assumed to be the tumour location. Dose distributions were scored
considering several center-to-center distances (c-t-c) from 1400 to
3500 mm. To spare the healthy tissues high peak-to-valley dose ratios
(PVDR) and low valley doses are required [1]. Therefore, as a figure of
merit, PVDR, valley doses and penumbras were assessed. Additionally,
the contribution of hadronic and electromagnetic secondary processes
was also evaluated.
Results: Very high PVDR (>100) and low valley doses were reached in the
healthy tissues. Extremely small penumbras (<450mm) were also
observed. These results suggest a potential gain in healthy tissue sparing.
In the tumour (Bragg peak position), the dominant contribution to the
peak and valley doses was associated to hadronic processes. Whereas, in
the healthy tissue, the relative weight between hadronic and electromagnetic processes depends on the type of incident ion, the c-t-c distance
and the depth.
Conclusion: Preliminary results show that a spatial fractionation of the
dose in heavy-ion therapy might provide a promising alternative for
radioresistant tumours while preserving healthy tissue. Biological studies
are warranted.
References
[1] F. A. Dilmanian et al., Neurooncol., vol. 4, p. 26-39 (2002).
[2] Y. Prezado et al., J. Synchrotron Radiat. 19, 60e65 (2012).
[3] J. Castro et al, Int. J. Radiat. Oncol. Biol. Phys., 29 647-655 (1994)
[4] S. Jan et al, Phys. Med. Biol. 56 881-901 (2011)
Key-words: Heavy-ion therapy, Minibeam radiation therapy (MBRT),
Monte Carlo simulations
A COMPARISON OF TWO PRACTICAL APPROACHES FOR CONE BEAM
COMPUTED TOMOGRAPHY (CBCT) DOSIMETRY USING MONTE CARLO
TECHNIQUE
A.
Abuhaimed a, b,
C.J.
Martin b,
M.
Sankaralingam a,
D.
Gentle c. a Radiotherapy Physics, Department of Clinical Physics and
Bioengineering, Beatson West of Scotland Cancer Centre, Glasgow, UK;
b
Department of Clinical Physics, University of Glasgow, Glasgow, UK;
c
Health Physics, Department of Clinical Physics and Bioengineering,
Gartnavel Royal Hospital, Glasgow, UK
Purpose: Studies have shown that the computed tomography dose index
(CTDI) measured with a 100 mm long pencil ionisation chamber, used for
conventional CT scanners, is an inappropriate dose metric for use with
cone beam CT (CBCT). A number of alternative practical approaches have
been proposed to overcome the limitations. The aim of this project was to
compare two of these in terms of their dose efficiency using Monte Carlo
simulation.
Materials and methods: Monte Carlo (EGSnrc/BEAMnrc) and (EGSnrc/
DOSXYZnrc) codes were used to model dose distributions within PMMA
head and body phantoms with 16 and 32 cm diameters respectively for
the kV imaging system of the Varian Truebeam linac. The Monte Carlo
model was benchmarked against experimental measurements. The approaches studied were: (1) proposal by IEC (CTDIIEC) to replicate CTDI100
for a long pencil chamber, and (2) point dose measurements D(0) with a
small ion chamber. Three phantom lengths (150, 600, 900 mm) were
Abstracts / Physica Medica 30S1 (2014)
used, where the latter two were considered to represent infinitely long
head and body phantoms, respectively. The efficiencies were estimated
as the ratios of CTDIIEC and D(0) in 150 mm long phantoms to CTDI∞
calculated within the infinitely long phantoms. Beam widths studied
ranged from 60 to 300 mm.
Results: For beams of width 80 mm, the CTDIIEC,w was more efficient in
terms of recording a greater proportion of the absorbed radiation, but for
wider beams >80 mm the D(0)w was more efficient. The ratios for
CTDIIEC,w were approximately constant over all beam widths, where the
values for the head and body phantoms were 82.2 ± 0.9% and 75.7 ± 0.7%,
respectively. The ratios for D(0)w in the head and body phantoms
increased from 73% to 94% and 71% to 92%, respectively, with beam width
as the beam extended beyond the phantom edges, respectively.
Conclusion: As most CBCT machines utilize a beam width >80 mm, results
suggest that the D(0) approach is the better option for CBCT dosimetry.
This involves fewer measurements than CTDIIEC,w and is more practical for
regular use in the medical environment.
PATIENT DOSE ESTIMATION IN CARDIAC COMPUTED TOMOGRAPHY
WITH A 320 DETECTOR ROW SCANNER BASED ON MONTE CARLO
SIMULATION
ndez-Giro
n a, A. Calzado c, M.
M. Cros a, J. Geleijns b, R.M.S. Joemai b, I. Herna
d
a a
Dewey , M. Salvado . Unitat de Física Medica, Universitat Rovira i Virgili
(URV), Spain; b Radiology Department, Leiden University Medical Center
(LUMC), The Netherlands; c Departamento de Radiología, Universidad
Complutense de Mardrid (UCM), Spain; d Department of Radiology, Charite.
€tsmedizin Berlin, Germany
Universita
Purpose: To estimate organ doses and effective dose for CT calcium
scoring, CT coronary angiography and CT myocardial perfusion according
to the internationally recognized recommendations of the ICRP.
Materials and methods: Monte Carlo simulations based on the EGS4
code were used to model the Aquilion ONE CT scanner and the two
ICRP computational phantoms representing the standard female and
male patient models. Dose calculations were performed for the cardiac
CT acquisition protocol used in a multicenter study for the assessment
of the calcium score, coronary arteries CTA and CT myocardial perfusion (CORE320). All acquisitions were performed as axial volumetric
scans, covering the entire heart in a single (low heart rate 65 bpm)
or dual (high heart rate 66 bpm) heart beats. This was done by
positioning the phantoms in the isocenter (common practice in MC
calculations) and by centering their hearts to the rotation axis (clinical
practice). The effect of removing the arms from the phantom was also
evaluated since the ICRP phantoms have their arms stretched along the
body whereas in clinical practice the arms are removed from the
scanned volume.
Results and discussion: Effective dose averaged for females and males
was 1.9 mSv for coronary calcium score; 5.1 mSv for coronary CTA
including rest cardiac perfusion at low heart rates, 9.7 mSv at high heart
rates; and 4.3 mSv for stress cardiac perfusion at low heart rates, 8.5 mSv at
high heart rates. No significant differences in effective dose were observed
for centering versus off-centering for both phantoms. Removing the arms
from the scan region led to an increase of effective dose of about 6% to 8%.
For coronary CTA and rest cardiac perfusion and using the most relevant
configuration (phantom off-centered without arms) at low heart rate, the
highest organ doses averaged for females and males were 16 mGy in
breast, 15.5 mGy in heart and 11 mGy in lung. The k-factors used in other
studies led to underestimations of effective dose by a factor of 2 and 3 for
an average male and for an average female patient, respectively, compared
to this study results.
A NEW OPTICAL PHOTON TRANSPORT MONTE CARLO CODE FOR
MODELLING PARALLEL- AND FOCUSED-ELEMENT SCINTILLATION
DETECTOR ARRAYS AND ITS USE FOR EXAMINATION OF THE FULL
MTF RESPONSES OF THICK SEGMENTED CSI(TL) SCINTILLATORS
Mohammad Amin Mosleh-Shirazi a, Zinat Zarrini-Monfared b, Sareh
Karbasi a, Ali Zamani b. a Physics Unit, Department of Radiotherapy and
13
Oncology, Iran; b Department of Medical Physics and Engineering, Shiraz
University of Medical Sciences, Shiraz, Iran
Purpose: Arrays of thick segmented crystalline scintillators are considered
useful x-ray converters in electronic portal imaging and cone-beam
megavoltage CT for radiotherapy verification. They consist of a 2D matrix
of scintillators separated by optically opaque, reflective septal walls and
can offer a high quantum efficiency and acceptable spatial resolution.
However, it has been shown using ionizing-radiation-only simulations,
that in such parallel-detector-element arrays, obliquely incident x-rays
reduce modulation transfer function (MTF) performance and degrade
spatial resolution in peripheral areas. A focused geometry has therefore
been proposed. The full performance of such a focused geometry is still
unclear. The aim of this work was to investigate the imaging performance
of such arrays using a detector model that supported light transport, as
well as x-rays and electrons.
Methods: To simulate x-ray and electron transport, we used the MCNP
Monte Carlo code to model the required array geometries added to a
validated model of a 6 MV linac head. Then, the transport of the generated
optical photons was modelled using ScintSim2, an optical Monte Carlo code
we wrote in MATLAB for simulation of parallel- and focused-element
scintillation detector arrays. We present ScintSim2 and report the results of
using it to examine the full (ionizing and optical radiation) MTF responses
of focused- and parallel-element geometries, for a large array of 33 mm2
CsI(Tl) elements with thicknesses of 10, 40 and 60 mm. A slit geometry was
simulated to obtain the line spread function (LSF) of the energy deposited
in the elements (radiation-only) or the number of optical photons incident
on an underlying screen (full simulation). Then, for each case, a composite
LSF was calculated and Fourier transformed to obtain the MTF.
Results: Differences were observed between the radiation-only and full
MTF performances of the arrays. At the Nyquist frequency, focused elements provided an increase of up to 8 times in peripheral-area full MTF
values. Further, the light exiting thicker scintillators exhibited a more
forward-directed distribution.
Conclusion: The observed differences in the results obtained with and
without optical photon simulation justify the additional effort of including
light transport when optimizing these promising thick segmented
detectors.
Key words: Optical photon transport; Detector optimization; Thick
segmented crystalline scintillators; Monte Carlo simulation; Megavoltage
electronic portal imaging; Radiotherapy treatment verification.
OPERATIONAL EXPERIENCE FROM THE MANAGEMENT OF I-131 LIQUID
WASTES FROM PATIENTS TREATED FOR THYROID CANCER IN
“THEAGENION” CANCER HOSPITAL
M. Tsiouprou, M. Kotzassarlidou, N. Papadopoulos, S. Georgitzikis, V.
Chatzipavlidou. Nuclear Medicine Dept., THEAGENIO” Cancer Hospital,
Thessaloniki, Greece
Aim: Problems and pitfalls exist in management of I-131 liquid wastes, in
hospitals treating patients for thyroid cancer. In this report, data of current
practice drawn from the Nuclear Medicine Department of “Theagenio”
Cancer Hospital, where three radioactive decay tanks are installed, are
presented.
Materials and methods: Records of time period 2011-2013 are reported.Two single-bed isolation rooms exist, linked to three tanks positioned
in hospital’s second basement. Each tank’s volume is 6500lt, whereas total
capacity of filling is 85%, ie 5525lt. Tanks are equipped with submersible
blade systems and ultrasound system for level monitoring. Electronic
control system exists in the medical physics department, in order to
inspect effluent levels of tanks. Based on biokinetic data from ICRP 53
(ICRP, 1988), I-131 activity discharged in the sewage system is equal to 95%
of the administered dose to each patient. Prior tank’s drainage, samples are
taken out from it and activity concentration is measured by 1024 Multichannel Analyzer spectrometer of Captus 3000 Thyroid Uptake System.
Records for filling, closing, emptying, interruption of operation are saved
into the PC running the system’s management. SPSS Statistics was used for
statistical analysis of patient data, calculation of tank’s mean time for
filling and delay. General equation estimating activity at the end of filling
14
Abstracts / Physica Medica 30S1 (2014)
phase, as a function of the mean value of administered activity per patient
treated each week was also acquired.
Results: 675 patients were treated through 2011-2013. Mean administered activity 113,5±31.8mCi. Tank’s filling phase:42±4days.Rest decay
duration:63±3days. I-131 activity,T, at the end of tank’s filling phase is
given by the formula: T¼5.6*Aavg,[mCi] whereas Aavg[mCi] is the
average amount of administered activity during tank’s filling time
period. Tvalues:560-835 mCi and average monthly concentration
0.13mCi/lt. In accordance with Greek legislation, maximum limit of
discharge is 110MBq /day. Liquid samples collected at releasing time
documented radioactive releases of I-131, equal to those derived from
estimations, much below recommended levels of once release. During
the above time period a tank’s operation was interrupted twice as a
consequence of clogging. Graphs that depict the measurements beyond
are also provided.
Conclusions: Above real practice data may be useful for further studies of
environmental radiation protection from liquid waste of patients undergoing I-131 therapy for thyroid cancer. Physicists, taking into consideration
ALARA principle, economic and social factors, must design in advance,
emergency plan assuring that, any individual’s exposure is kept to the
minimum practicable, in case of system’s mulfunction.
A COMPARISON OF PATIENT SPECIFIC DOSIMETRIC CALCULATIONS
OBTAINED BY PLANAR IMAGES AND MONTE CARLO SIMULATION IN
111
IN OCTREOTIDE THERAPY
Maria Argyrou a, Maria Andreou a, Nefeli Lagopati a, Irini Baka a, Ioannis
Vamvakas b, Maria Lyra a. a Radiation Physics Unit, A’ Radiology
Department, Kapodistrian University of Athens, Aretaieion Hospital, 76 Vas.
Sophias Ave, Athens, Greece; b Medical Physics Department, Iaso Hospital,
Athens, Greece
Aim: The purpose of this study is to estimate absorbed doses in the
lesions and in critical organs after administration of therapeutic dose of
111
In octreotide, in patients diagnosed for neuroendocrine tumors in
liver.
Methods: 20 patients, with histologically confirmed neuroendocrine tumors located in liver and normal kidney function were infused therapeutic
dose of 111In octreotide, with mean activity of 4500 MBq, via intrahepatic
catheterization, which is well established technique in our Institution in
hepatocellular carcinoma and neuroendocrine tumors treatments. The
dosimetric protocol was based on quantitative bi-planar whole body
scintigrams to determine the pharmacokinetic properties and the estimation of the imparted energy per unit of accumulated radioactivity
implementing the Monte Carlo method.
Planar scintigraphy was performed after radiopharmaceutical infusion,
through hepatic arterial port, 24 and at 48 h post infusion, for the patients
with liver lesions. For this reason, gamma camera was calibrated in order
to estimate source organ activity considering count rate, patient’s body
diameter and source organ size.
The MIRD schema, as well as the Monte Carlo simulation (MCNP code) was
employed, for absorbed dose calculations. The Monte Carlo geometries,
were prepared in order to approach the patient’s anatomy. Two patients,
one male and one female of similar weights (70 kg), were considered to be
as representative cases, to be used in the simulation process. The tumor
was consider as sphere inside a spherical liver and the radioactive source
was considered as point source. One million events were counted.
Results: The results from planar scintigraphy showed that the tumor
absorbed dose ranged from 2.5 to 18.4 mGy/ MBq, depending on the lesion
size.
The overall standard deviation is about 11 % for planar data calculations
compared to those, obtained by Monte Carlo simulation.
Conclusion: High deviations of absorbed dose between patients were
observed. Consequently patient specific dosimetry calculations are
necessary in order to help the physician to optimize the planning of the
treatment, avoid side effects to healthy tissue and assign administered
dose to treatment results, so the optimization of this method is very
desirable. Monte Carlo simulation is an effective and easy method for dose
estimation taking into account anatomical features without the need for
experimental processes.
VALUE OF DOSIMETRIC CALCULATIONS OF SM-153 BETA PARTICLEEMITTER, IN TREATMENT OF METASTATIC BONE DISEASE
Irini
Baka a,
Maria
Argyrou a,
Marina
Michalitsi a,
Maritina
Rouchota a, Alexia Valassi a, Maria Lyra a, b. a Radiation Physics Unit,1st
Department of Radiology, Aretaieion hospital, University of Athens, Greece;
a
Nuclear Medicine Section, 1st Department of Radiology, Aretaieion
hospital, University of Athens, Greece
Aim: Optimum treatment planning of patients suffering from
painful skeletal metastases requires accurate calculations concerning
absorbed dose in metastatic lesions and critical organs, such as red
marrow. Delivering high absorbed doses to tumor cells, while limiting
radiation dose to normal tissue is the aim of palliation therapy. Such a
combination can be achieved with the application of bone-seeking
phosphonate
ethylenediaminetetra
methylenephosphonic
acid
(EDTMP) chelated with the beta particle-emitting radionuclide
Sm-153.
Methods: In our institution, patients received (18-37) MBq/kg per treatment cycle which has proved to be highly justified and efficient. Planar
scintigraphic images were acquired and used for an estimation of dose in
site specific lesions, according to the MIRD schema. For counts conversion
to activities, calibration factors were calculated. Planar images of cylindrical water - filled phantom, with five different known amounts of activity, were obtained. Corrections for scatter attenuation, collimator
efficiency and detector response were calculated. The MIRDOSE 3.1 software was used for the calculation of spot site absorbed dose.
For the crucial bone marrow dosimetry two different approaches are
presented. Marrow rich regions, sacral area and sternum were drawn.
Counts obtained and the mean residential time was the input for MIRDOSE
software template. By the second procedure, the activity in the whole body
was calculated as the residual of the activity excreted in urine, AWB (t) ¼A0Acum (Ur) (t). Using the MIRD formalism, DRM ¼Acum (skel) *0.5 *[SRM)TB
+SRM)CB] assuming an equal distribution of skeletal activity in the
trabecular bone and cortical bone and neglecting the contribution of activity in blood. S values (absorbed dose per cumulated activity) were taken
from RADAR software.
Results/conclusion: The site specific lesion dosimetry revealed a relatively
high uptake of Sm-153-EDTMP. The estimated marrow dose from the latter
procedure was 1.179 ±0.8 mGy / MBq demonstrating a good approach
comparing the results from the imaging method indicating heterogeneity
of the marrow itself or the radionuclide distribution. Patient specific
dosimetry is of primary importance in helping establish the optimum
activity dosage for each patient enhancing the therapeutic efficacy with
limited red marrow doses and no toxic effects in other organs. Dosimetry
of Sm-153-EDTMP is a necessary tool for its patient specific therapeutic
application.
EXPERIMENTAL DETERMINATION OF MINIMUM DETECTABLE ACTIVITY
FOR RADIONUCLIDE ACTIVITY METERS
F. Zagni a, F. Cesarini a, G. Lucconi b, G. Cicoria a, D. Pancaldi a,
A.Infantino c, S. Vichi c, M. Marengo a. a Medical Physics Department,
University Hospital “S.Orsola - Malpighi”, Bologna, Bologna, Italy;
b
Postgraduate School in Medical Physics, Physics Department, University of
c
Nuclear
Engineering
Laboratory
of
Bologna,
Bologna,
Italy;
Montecuccolino, University of Bologna, Bologna, Italy
Aim: Radionuclide activity meters are normally used in nuclear medicine to measure relatively large amount of activity, ranging from
few MBq to tenth or hundreds GBq. The aim of this work was to evaluate the minimum detectable activity (MDA) for these devices, in
order to check the feasibility of their use in the lower range of
measurement.
Materials and methods: Four different activity meters installed at our
institution were tested. For each device, a vial containing >10 MBq 11C
(positron emitter, half-life 20 minutes) was assayed at fixed time intervals until complete decay and each activity reading was recorded. The
Abstracts / Physica Medica 30S1 (2014)
ratio between the activity reading and the expected activity, based on the
exponential decay law, was evaluated (% relative error, RE%). Each
reading was decay corrected to the same reference time, and the coefficient of variation (CV%) was calculated for contiguous measurements.
The two obtained quantities were plotted and analyzed as a function of
the expected activity. This procedure was repeated using 99mTc, in order
to verify the minimum response, which is correlated to the MDAs
through the calibration factors, to be independent on the radionuclide
being assayed.
The MDA was estimated by selecting threshold values, based on the uncertainty level and taking the worse between the two observed
parameters.
Results: For each tested activity meter, both RE% and CV% gradually
increase as the activity of the source decreases. The minimum response
in term of ionization current for each equipment, was found to be
the same for the two tested radionuclides; we could then estimate
MDAs values for several commonly used radionuclides. For each
meter we obtained different MDAs. For example, for a Capintec CRC15PET, 180 kBq (99mTc) and 50 kBq (11C) estimated at 90% of confidence
level.
Conclusion: This work shows that MDA can be assessed in terms of
ionization current and be converted for different radionuclides using
specific calibration factors. The measurement technique can be reproduced
by every laboratory, allowing for use of activity meters in some radiopharmaceuticals quality controls procedure.
EVALUATION OF A NEW METHODOLOGY FOR PAEDIATRIC DOSIMETRY:
OPTIMIZATION OF SPECT PROTOCOLS, BASED ON MONTE CARLO
SIMULATIONS
WITH
HIGH-RESOLUTION
ANTHROPOMORPHIC
PHANTOMS
George
Loudos b,
George
C.
Panagiotis
Papadimitroulas a,
Kagadis a. a Department of Medical Physics, School of Medicine, University
of Patras, Greece; b Department of Biomedical Engineering, Technological
Educational Institute of Athens, Greece
Background: Patient specific dosimetry is of high interest, especially in
pediatric applications where the risks of the exposure to ionizing radiation
is widely debated. The aim of this study, is to evaluate the dosimetric
factors in nuclear imaging, exploiting the advantages of realistic Monte
Carlo simulations and the ground truth of accurate, high resolution
computational models.
Methods: The latest version GATE (v6.2) toolkit was used for the
execution of realistic simulations. A series of pediatric phantoms,
developed by the “IT’IS Foundation”, were preprocessed in order to be
inserted in the simulations serving as attenuation and activity maps.
The procedure was standardized on a 5 years old girl, 17.8kg. The full
series of the models includes 3 boys and 3 girls in the range of 5-14 y
old. The resolution of the phantoms was set to 2 mm3. The S-factors of
99m
Tc-MIBI biodistribution were calculated, in two different time periods (30 min and 2 h post-injection), considering the whole-body as
source and the most critical organs as target. The administered activity
was set equal to 232.5 MBq according to the EANM dosage protocol. 3D
maps with the deposited energy per voxel as well as their uncertainty
were calculated for every simulation.
Results: In figure 1 the results of the S-factors in Gy/(MBqsec) are presented for a 5 years old girl for the whole body exposure to 99mTceSestaMIBI, 30 minutes and 2 hours post administration. The mass of each
critical organ is also presented namely heart, kidney, liver, ovary, pancreas
and brain. The statistical uncertainty in the simulation procedure was kept
lower than 5%. The highest S-factor was calculated for kidneys and it is
equal to 9.2910-10 for 30 min and equal to 7.1610-10 for 2 h post
injection.
Discussion: We consider that the present study presents a new
methodology to evaluate dosimetric techniques in pediatric nuclear
imaging applications. Our goal is to extend the internal dosimetric
calculations for the most common imaging protocols using various
children models.
Fig. 1. Dosimetric calculations for a 5 y old girl for
and 2 h post injection.
15
99m
Tc-MIBI biodistribution 30 min
NUCLEAR CARDIOLOGY IMAGE ENHANCEMENT USING WAVELET
TRANSFORM ANALYSIS
A. Poulakis a, c, S. Angelakis a, b, G. Fountos a, G.S. Panagiotakis b, I.
Asteriadis d, I. Valais a. a Department of Biomedical Engineering,
Technological Educational Institute of Athens, 12210 Athens, Greece;
b
Department of Medical Physics, Medical School, University of Patras, 265
00 Patras, Greece; c Biomedical Informatics and Technology Graduate
Program, School of Computer Science, University of Crete; d Department of
Nuclear Medicine, General Hospital of Kavala, 65 500 Kavala, Greece
Background: Myocardial scintigraphy is a Nuclear Medicine Imaging
technique that commonly uses Thallium Chloride (201 Tl-chloride) as a
radioactive tracer. The main disadvantage of this method is the
increased noise level in the extracted images due to poor counting
statistics (low count rate, lung uptake etc). One method that can be used
to improve image quality is Wavelet Transform Analysis. The contrast, as
well as the background and the gray level tonalities have been
preserved.
Materials and methods: In this study, the task is to maintain image
integrity improving quantitative information data useful in patient diagnosis, therapy and care. DICOM images form patients undergone
myocardial scintigraphy where examined. Noise reduction by Wavelet
Coefficient Thresholding 2D was used (Matlab, yet another wavelet
toolbox), removing the background activity, followed by compression and
reconstruction of the image respectively.
Results: Results were calculated using both Discrete Wavelet Transform
(DWT) and Continuous Wavelet Transform (CWT) and are presented in a
detailed way with graphs and figures. The process of a nuclear cardiology
image with the use of Discrete or Continuous Wavelet Transform results in
a homogenized image background so that the medical information is
carefully outlined. The contrast, as well as the background and the gray
level tonalities have been preserved.
Discussion: This method doesn’t need much cpu time and can be
used after the post acquisition so, valuable image information can be
showed right away for a more precise diagnosis. Findings showed
that using Discrete or Continuous Wavelet Transform on Nuclear Cardiology images, more information is gained and the image quality
improves
LONG-LIVED
RADIONUCLIDE
IMPURITIES
ACEUTICALS: PRACTICAL ASPECTS
IN
RADIOPHARM-
John Kalef-Ezra, Stratos Valakis, Stavroula Pallada. Medical Physics
Departments, University of Ioannina and Ioannina University Hospital
Ioannina 451.10, Greece
16
Abstracts / Physica Medica 30S1 (2014)
Background: Long-lived radioactive impurities in radiopharmaceuticals
administered at time of calibration usually have minor impact on
image quality and the uncertainty of the activity measurement. However, such impurities may result to non-negligible additional radiation
burden to patients, personnel, relatives, caregivers and the public,
and may trigger innocent alarms in radiation portal monitors. In
addition, the presence of certain levels of impurities may impose
modifications in waste management policies. The aim of the present
study was to identify the most important long-lived impurities, quantify their amount in the patients’ body and address radiation protection
issues.
Methods and materials: Initial analysis of the radiopharmaceuticals used
at the Ioannina University Hospital indicated substantial amounts of longlived (T1/2> 14 d) photon emitting impurities only in 123I-ioflupene
(DaTSCAN, GE) and 153Sm-EDMTP (Quadramet, IBA). Spectroscopic analysis of the residuals of at least ten administrations per agent was carried
out at least five times per sample. A prototype shadow-shield whole body
counter equipped with 16 NaI(Tl) detectors was used to measure the activity present in at least 7 seven patients per agent, 2 to 5 five weeks postadministration. The in vivo activity measurements were coupled with
external dose rate measurements using a portable system with spectroscopic capabilities.
Results: 121Te, 123Te and 125I were the main photon emitting impurities in
123
I-ioflupene, resulting in a median 30 nSv/h external Hp(10) rate and a 3
kBq 121Te body burden. 152Eu, 152Eu and 156Eu were the main impurities in
153
Sm-EDMTP, resulting in a median 300 nSv/h external rate, mainly due to
the 152Eu (T1/2:13.5 y) and 154Eu (T1/2:8.6 y) presence in the body, 25 and 33
kBq, respectively. Thus patient and waste management protocols were
modified accordingly.
Conclusions: Both patient and waste management have to take into account the long-lived impurities present in some of the agents used in daily
clinical practice.
MEDICAL WORKERS OPERATING IN NUCLEAR MEDICINE VS PET/CT:
RADIATION EXPOSURE COMPARISON
K. Dalianis a, J. Malamitsi b, K. Gogos a, R. Efthimiadou a, J. Andreou a, V.
Prassopoulos a. a PET/CT Department Hygeia SA, Athens, Greece; b Medical
Physics Laboratory School of Medicine, University of Athens, Greece
Purpose: Personnel monitoring results provide information on routine
radiation exposure, assist in work planning and allow control of the
workplace. The aim of this study was to compare the gamma dose received
by dedicated medical workers operating in the first PET/CT department in
Greece and also by dedicated medical workers operating in conventional
Nuclear Medicine procedures in the same center. PET/CT studies are
restricted to the use of 18F fluorodeoxyglucose (FDG). In addition Tc-99m,
Tl-201, Ga-67 and I-131 are the radiotracers mostly used in our Nuclear
Medicine department.
Method: To estimate the effective dose from external exposure, all 9
members of the staff (2 nurses, 2 medical physicists, 5 technologists) had
TLD badges worn at the upper pocket of their overall and digital dosimeters worn at the side pocket. Nurses and Medical Physicists also had TLD
rings. The nurses and technologists 1,2 are working only in the PET/CT
department, while technologists 3,4,5 are operating only in the Nuclear
Medicine department covering the most common procedures. Medical
Physicists 1,2 are operating in both departments.
Results: In the period of January 2013 to December 2013 a total of 982 PET/
CT studies and 2157 conventional Nuclear Medicine procedures were
performed. The collective effective and finger doses received by all 4
members of the PET/CT staff were the following: Nurse 1 received 2,94
mSv as a whole body dose and 6,84 mSv as a hand dose and Nurse 2
received 2,87 mSv whole body dose and 5,91 mSv hand dose respectively.
Technologists 1 and 2 received 1,95 mSv and 1,56 mSv as the whole body
dose respectively. Medical Physicist 1 received 1,75 mSv whole body dose
and 7,77 mSv hand dose and Medical Physicist received 2 2,17 mSv and
4,68 mSv respectively. Technologists 3,4 and 5 received 1,85 mSv, 1,76 mSv
and 1,82 mSv as whole body doses respectively
Conclusion: The personnel dose results are significantly lower than
the recommended annual dose by International Commission for
Radiological Protection. The higher value of gamma dose for PET/CT
workers by comparison with the staff operating conventional Nuclear
Medicine procedures is attributable to the higher specific gamma
constant of 18F, as well as the longer exposure time required for accurate positioning.
THREE-DIMENSIONAL METRICS FOR QUANTITATIVE MONITORING OF
TREATMENT EFFECTS WITH PET/CT
N. Politis a, A. Georgakopoulos b, M. Metaxas b, S. Chatziioannou b, c, M.
Kallergi a,b. a Department of Biomedical Engineering, Technological
Educational Institute of Athens, Greece; b Nuclear Medicine Division,
Biomedical Research Foundation of the Academy of Athens, Greece;
c
Nuclear Medicine Section, 2nd Department of Radiology, “Attikon”
University General Hospital, National and Kapodistrian University of
Athens, Greece
Background: Quantitative monitoring of tumor response to treatment
with PET has been introduced in the last decade and volume-based criteria
have been proposed for this purpose (PERCIST 1.0 in 2009). The purpose of
this study was to evaluate the expansion of the standardized uptake value
corrected for lean body mass (SUL) metric to tumor volume size measurements pre- and post-treatment for more standardized and accurate
treatment monitoring.
Materials & methods: A database was developed of 24 serial PET/CT
scans of patients with non Hodgkin’s lymphoma; each patient had one
scan before and one after at least one cycle of chemotherapy. An expert
nuclear medicine physician manually outlined all tumors, before and after
treatment, on all PET and CT slices they are observed in. The expert’s
outlines were used as “ground truth” to image processing and tumor
segmentation that was done in MATLAB. A semi-supervised algorithm
was implemented for the generation of 2D and 3D outlines of the tumors
on PET and CT slices. The tumors’ maximum diameter and volume were
measured in addition to SUL estimates. Binary logistic regression was
used to evaluate the association between the three metrics (diameter,
volume, and SUL) and treatment outcome, expressed as progression free
survival (PFS) rate.
Results: The data analysis is ongoing. However, preliminary results suggest
that volume is a more standard and reproducible metric than the diameter
in assessing response to treatment; even a 10% in volume shrinkage can be
a strong predictor of long term outcome. In addition, the combination of
volume changes with SUL changes yields a significantly better predictor of
treatment outcome and correlates more to PFS rates than the tumor
diameter or SUL.
Discussion: Changes in tumor volume corresponding to anatomic
changes combined with SUL changes indicating metabolic tumor
response are stronger predictors of treatment outcome than changes in
tumor diameter or SUL changes alone as proposed by the RECIST or
PERCIST criteria.
POSITRON EMISSION TOMOGRAPHY'S NEWEST TECHNOLOGIES TO
ADDRESS PRESENT AND FUTURE APPLICATIONS: A FOCUS ON TIMEOF FLIGHT
L. Theodorakis a, b, G. Loudos b, V. Prassopoulos c, C. Kappas d, I. Tsougos d, P.
Georgoulias a. a Department of Nuclear Medicine, University Hospital of
Larissa, Biopolis, Larissa 41110, Greece; b Department of Medical
Instruments Technology, Technological Educational institute of Athens, Ag.
Spyridonos Str., Egaleo 122 10, Athens, Greece; c PET/CT Department, Hygeia
Hospital, Erythrou Stavrou Str. & Kifisias Av., Marousi 151 23, Athens,
Greece; d Medical Physics Department, Medical School, University of
Thessaly, Biopolis, Larissa, Greece
Introduction: Positron Emission Tomography (PET) is constantly moving towards newer applications, extending its scope far beyond of just
providing with the answer for the presence of cancer or not. Novel radiopharmaceuticals for the functional characterization in the brain or
stem cells tracking after their transplantation are among these applications [1]. Taking also into consideration that treatment planning and
response-to-therapy assessment usually involves a PET/CT scan, the
Abstracts / Physica Medica 30S1 (2014)
need for count rate sensitive scanners has been replaced by the need for
high spatial resolution, contrast and reproducibility in quantification
even in the case of really small activities [2]. In this work, the newest
technologies to address these needs are mentioned, with a focus on
reconstruction schemes that include the Time-of-Flight (ToF) kernel.
Monte Carlo simulations are used to project how ToF can improve NECR
(Noise Equivalent Count Rate ¼T2/(T+S+kR) for a given scanner geometry since they can record the history of all detected photons (T, S, R are
the trues, scatter and randoms count rate respectively, k¼2 for a delayed
window randoms correction).
Materials and methods: Monte Carlo simulations using GATE [3], an open
source software based on the GEANT4 toolkit, are used to provide
comparative NECR data between a scanner utilizing “ToF-permitting” detector crystals (Lu2(SiO4)O:Ce, or “LSO”) and the same scanner utilizing a
“non-permitting” one (Bi4Ge3O12, or “BGO”). The geometry and the digitizer settings for the simulations are based on an existing clinical system
(Biograph 16 HiRez, SIEMENS AG) and adapted to the crystal type. A 40 cm
cylindrical phantom uniformly filled with a range of 18F-FDG activities
between 1 and 30 microcuries (mCi) is also used to mimic the average
human size.
Results and discussion: Figure 1 shows the non-ToF NECR response for
the BGO and LSO scanner. The ToF implementation results in a NECR
magnification with a gain equal to 6 for the 40 cm phantom, compared
to the non-ToF NECR for the same activity [4]. The BGO and the LSO
scanner are presenting an almost identical NECR behavior for activity
values up to 15 mCi. Slightly higher values for the BGO scanner in this
range are due to higher density of the crystal material compared to its
LSO counterpart. NECR(non-ToF, BGO) shows a horizontal response for activity values beyond 25 mCi, mainly attributed to the broader coincidence time window and increased deadtime of detectors based on BGO.
Figure 2 shows the distribution of the deposited energy for the two
crystals.
Conclusion: Evolving technology for PET scanners is guided from the
needs dictated by novel applications. The advent of Lutetium-based
scintillators enabled ToF implementation, this way improving NECR
performance. The introduction of Silicon Photomultiplier detectors with
ToF capability is expected to further improve the performance of fast
scintillators. ToF is an excellent representative of such innovations to
address present and future challenges in the medical and research field.
References
[1] Zhou R, Acton P, Ferrari V. Imaging Stem Cells Implanted in Infarcted
Myocardium. Journal of the American College of Cardiology
2006;48(10):2094-2106.
[2] Freedenberg M, Badawi R, Tarantal A, Cherry S. Performance and limitations of positron emission tomography (PET) scanners for imaging very
low activity sources. Physica Medica 2014;30(1):104-110.
[3] http://www.opengatecollaboration.org/
[4] Conti M, Focus on time-of-flight PET: the benefits of improved time
resolution. European Journal of Nuclear Medicine and Molecular Imaging
2011;38:1147-1157.
17
Fig. 2 Distribution of total deposited energyĂ
OPTIMIZATION OF CONE BEAM CT PROTOCOLS USED IN IMAGE GUIDED
RADIOTHERAPY APPLICATIONS
Theofano Riga, Efi Koutsouveli, Christos Skarleas, Konstantinos Dardoufas
Pantelis Karaiskos. Medical Physics and Radiotherapy Department, Hygeia
Hospital, Athens, Greece
Image-guided radiation therapy (IGRT) using kilovoltage (kV) cone beam
computed tomography (CBCT) can provide accurate three dimensional
volumetric knowledge about the patient’s anatomy and target localization
at treatment position and thus has dramatically improved the delivery
accuracy in radiotherapy. This is achieved through registration of the CBCT
images with the reference CT images utilized for treatment planning
purposes, using automatic rigid body image registration algorithms.
However, the acquisition of CBCT images adds an additional radiation dose
thus entailing new radiation risks to the patient. The purpose of this work
is to study the relationship between the image registration accuracy and
the imaging dose and image quality for different CBCT protocols using a
commercially available image guidance system (Synergy, Elekta, UK). A
Catphan phantom (The Phantom Laboratory, Salem, NY) was used for
image quality (low contrast visibility, spatial resolution and uniformity)
measurements. Radiation dose was determined using a Farmer chamber
that had been calibrated in the kV energy range by an accredited laboratory. The ability of the CBCT system to correctly register the localization
geometry with the reference CT geometry was tested using a Rando
phantom (The Phantom Laboratory, Salem, NY) for a head and a pelvis
irradiation. For this purpose a pelvis and a head plan were created in the
reference CT images of the Rando phantom; for each plan its icocenter was
defined using the CBCT system and subsequently the phantom was moved
by specific distances in one or more directions relatively to the reference
icocenter position using the couch; these distances were compared to the
corresponding ones calculated by the CBCT system registration algorithm.
All measurements (including image quality, radiation dose and registration
accuracy) were repeated for different CBCT by changing the tube current
and pulse length per projection image and thus the total mAs. Results
show that a significant reduction of the additional radiation dose given to
the patient due to the CBCT images acquired during an IGRT treatment can
be achieved by optimizing the imaging protocol without a significant
reduction of image quality or a significant loss of dose delivery accuracy.
TESTING OF DEFORMABLE IMAGE REGISTRATION IN RADIOTHERAPY
USING COMPUTATIONAL PHANTOMS
Stephen Skett a,b. a Peterborough City Hospital, UK; b King's College London,
UK
Fig. 1 NECR response for the BGO and LSO scannerĂ
Purpose: Deformable image registration (DIR) involves ‘deforming’ one
image to match another ‘reference’ image of a given patient. This technique
has great potential in the drive towards adaptive radiotherapy. However, it
is crucial to benchmark the performance of DIR software before it is used
18
Abstracts / Physica Medica 30S1 (2014)
clinically. The present study concerns the testing of the DIR algorithm in
Prosoma 3.3, a radiotherapy virtual simulation and contouring software
package, to evaluate its geometric accuracy.
Materials & methods: DIR testing was undertaken by creating an in-house
software system (‘vCTphantoms’) capable of producing CT-like images
containing arbitrary combinations of geometric structures and performing
simple global deformations to them. DIR was performed in Prosoma for
several such phantom test images, including: a) a spheroid stretched to
differing degrees; b) two phantoms with anthropomorphic features
modelling the anatomy of lung and prostate radiotherapy patients
respectively. Where possible, the Dice Similarity Coefficient (DSC) was
computed by manually contouring significant volumes of interest in
Prosoma on both deformed & reference images, as a means of assessing
their geometric correspondence.
Results: When applied to the spheroid phantom images mentioned
above, the Prosoma DIR algorithm managed to achieve good correspondence (DSC0.99) for stretches of maximum displacement 11mm. For
the other phantom types, levels of visual correspondence were somewhat
mixed; discrepancies between deformed & reference images were in
some cases quite strident, and the DSC could not be evaluated since it was
impossible to generate valid contours of important structures in the
deformed images. Two other key observations were made concerning the
DIR functionality in Prosoma. Firstly, it was not possible to export the
deformed image data, or to obtain details of the deformation vector field.
Secondly, the displayed HU values did not correctly represent what was
seen for the deformed data set; rather, they were the same as those for the
reference image.
Conclusion: In simple test conditions, the DIR in Prosoma 3.3 responded
well to image changes at spatial scales similar to those expected in real
clinical anatomy. However, its testability and potential usefulness for
clinical radiotherapy is somewhat undermined by the inability to obtain
accurate quantitative information about the deformed image set.
References
R. Varadhan, G. Karangelis, K. Krishnan and S. Hui, “A framework for
deformable image registration validation in radiotherapy clinical applications,” J. Appl. Clin. Med. Phys., vol. 14, no. 1, p. 4066, Jan. 2013.
USING STATISTICAL MODELS TO OPTIMISE CURE AND MINIMISE SIDEEFFECTS IN CANCER RADIOTHERAPY
Herschtal Alan a,b, Te Marvelde Luc c, Mengersen Kerrie d, Foroudi
Farshad e, Kron Tomas f. a Senior Biostatistician, Centre of Biostatistics and
Clinical Trials, Peter MacCallum Cancer Centre, Melbourne; bPhD candidate,
Swinburne University of Technology, Melbourne, Australia; c Biostatistician,
Centre of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre,
Melbourne; d Research Professor of Statistics, Science and Engineering
Faculty, Queensland University of Technology; e Chair of Uro-Oncology,
Radiation Oncology, Peter MacCallum Cancer Centre,Melbourne, Australia;
f
Principal Research Physicist, Physical Sciences, Peter MacCallum Cancer
Centre
Traditional CTV-to-PTV margin recipes for external beam RT, are used to
ensure sufficient dose to tumour despite day-to-day variability in tumour
position relative to treatment beams (i.e. random error). Most methods of
setting margins assume that the random error is constant across patients
and hence provide a “one size fits all” margin. We have collected data that
shows that there is large variability in random error between patients, and
that therefore the one size fits all approach yields margins which are too
large for more stable tumours (small random errors), and too large for the
less stable ones (large random errors). A hierarchical Bayesian model is
capable of optimising the margin for each individual patient by optimising
the trade-off between the traditional generic group margin, and a personalised margin based on displacement data that accumulates as the
individual progresses through treatment. We have constructed a novel two
layered Bayesian model which can accurately calculate personal margins
despite time trends, unexpected “spikes”, and sudden shifts in tumour
position, thus ensuring maximum cure rates while minimising side-effects. By simulating on real patient motion data, collected for patients who
underwent hyperfractionated EBRT, we show that a single replan of the
patient after two weeks of an approximately seven week treatment course
yields an average reduction of 20% in radiation dose to healthy tissue
relative to current methods, with no loss of dose to the CTV itself and thus
no expected increase in the risk of recurrence.
This work was funded by an Australian National Health and Medical
Research Council grant
PERIPHERAL DOSE ASSESSMENT AFTER IMRT AND VMAT VS CFRT
nchez-Nieto a, R. El-far a, M.R. Expo
sito b, J.I. Lagares c, J.C. Mateo d, J.A.
B. Sa
n e, G. Zeladas f, L. Irazola g, F. S
anchez Doblado g. a Instituto de Física,
Terro
lica de Chile, Santiago, Chile; b Universitat
Pontificia Universidad Cato
noma de Barcelona, Barcelona, Spain; c Centro de Investigaciones
Auto
gicas, Madrid, Spain; d Hospital
Energ
eticas Medioambientales y Tecnolo
Duques del Infantado, Sevilla, Spain; e Hospital Universitario Virgen
Macarena, Sevilla, Spain; f Unidad de Radioterapia, Clínica Alemana de
edica y Biofísica,
Santiago, Santiago, Chile; g Departamento Fisiología M
Universidad de Sevilla, Sevilla, Spain
Background: The higher survival rate of radiotherapy patients entails a
growing concern on second cancers associated to peripheral doses. This is
enhanced due to the higher beam-on time of new techniques (VMAT and
IMRT). Currently, dosimetry of out-of field doses is still under development. Our group has developed a methodology to estimate neutron
equivalent dose in organs (PMB 57 (2012) 6167e6191) as well as an analytic algorithm for photon peripheral doses (RO 103 (2012) S530). The
aim of this study was to assess peripheral doses in IMRT and VMAT versus
CFRT.
Materials and methods: Prostate and rectum treatments where delivered
to the Alderson phantom using 3DCFRT and one modulated technique.
Plans were designed to get the same PTV coverage. Neutron doses at peripheral organs were estimated from the readings of a digital detector
using our methodology. Photon doses were calculated using our algorithm
from specific treatment and phantom parameters (prescription dose, MU,
PTV volume, phantom size, etc.).
Results: Photon and neutron doses for prostate treatments ranged 118-254
mSv and 35-232mSv, respectively. For rectum treatments doses ranged
210-255mSv and 25-136mSv. For both treatments, the highest and lowest
photon to neutron doses ratios were obtained for the 3DCFRT at 15MV and
IMRT18 at 18MV, respectively. Average neutron doses increased 7mSv per
1000UM (4mSv for photon doses).
Discussion: As neutron doses strongly depend on MU, multiplying by
three the MU at 18 MV (IMRT vs CFRT) implies doubling the peripheral
dose. At 15MV, comparing VMAT with CFRT (i.e., doubling the MU) has
almost no impact on peripheral doses.
MEASUREMENT, MODELLING AND REPORTING OF SMALL FIELD
OUTPUT FACTORS REQUIRES SYSTEMATIC APPROACHES FOR
ACCURATE DOSIMETRY
G.
Cranmer-Sargison b,
P.H.
Charles c,
J.V.
D.I.
Thwaites a,
c a
Trapp . University of Sydney, Institute of Medical Physics School of
Physics, Sydney, Australia; b Saskatchewan Cancer Agency, Department of
Medical Physics, Saskatoon, Canada; c Queensland University of Technology,
School of Chemistry Physics and Mechanical Engineering, Brisbane, Australia
Small field dosimetry is difficult, yet consistent data is necessary for
advanced radiotherapy techniques. However, the reported data in the
literature contains relatively large inconsistencies and differences. To help
to resolve these and to improve the approaches and associated uncertainties requires careful standardised measurements, validated MonteCarlo (MC)-based correction factors, possible new thinking on detectors
and clear reporting of data, correlating to actual/delivered/dosimetric field
size to enable comparison between linacs. For very small field sizes,
greater attention is required to the experimental measurement and
reporting methods, requiring clear guidelines for what is a ‘very small field
size’ and for when such more detailed methods are needed.
A range of measurements and MC modelling studies have been reported by
our group. Based on these methods and results, recommendations are
given as to:
Abstracts / Physica Medica 30S1 (2014)
commissioning/fine-tuning a MC model for small field sizes; and the
interplay between modelling and measurements to achieve this
modelling-based correction factors for a range of shielded and unshielded diodes for 6MV beams;
what constitutes a ‘very small field size’ (essentially fields smaller than
1.5 cm in size for 6 MV), based on the different effects as field size gets
smaller and their consequences for uncertainties;
measurement methods necessary to control uncertainties at these
smaller field sizes (essentially measuring beam profiles at the same time as
output factor, to ensure good alignment, but also to measure the exact
dosimetric field sizes
reporting of output factors for consistent comparison and applications; ie
reporting against an effective field size taking into account measured
dosimetric field sizes; and not just against nominal field size, in order to
reduce the variations in reported data and allow interpolation between
reported tabulated data eg on correction factors.
observations on detector design and modelling for possible ‘correctionfree’ small detectors (eg scintillators, but also modified standard detectors
such as diodes)
As national (eg AAPM) and international (eg IAEA) bodies develop protocols for small field dosimetry, it is critical that clear measurement and
modelling based methods and data are recommended to improve the
consistency and uncertainties involved and to provide the best accuracy
possible in these increasingly clinically-used conditions.
DOSIMETRIC EVALUATION OF A MICRODIAMOND PROTOTYPE IN
CLINICAL PROTON AND CARBON-ION BEAMS
Marco Marinelli a, G. Prestopino a, C. Verona a, G. Verona-Rinati a, A.K.
Mandapaka b, A. Ghebremedhin b, B. Patyal b, G.A.P. Cirrone c, G.
Cuttone c, S. La Rosa c, L. Raffaele c. a INFNeDipartiment of Industrial
Engineering, University of Rome “Tor Vergata”, Italy; b Department of
Radiation Medicine, Loma Linda University Medical Center, California, USA;
c
Laboratori Nazionali del SUD, INFN, Catania, Italy
Background: The aim of the present study is to evaluate the dosimetric
properties of a pre-market prototype of PTW Freiburg microDiamond
dosimeter for accurate relative dose measurements in clinical proton
beams. Preliminary results on carbon-ion irradiation will be reported as
well.
Materials and methods: The device was fabricated at the University of
Rome “Tor Vergata” and tested under clinical proton beams both at the
Loma Linda University Medical Center and at the INFN-LNS laboratory
in Catania, Italy. The performance were assessed by comparison with
reference parallel plate ionization chambers (PTW Markus Chamber
23343 and Advanced Markus Chamber 34045) and a micro ionization
chamber (Exradin A16). All measurements were performed in a water
phantom. The warm-up/stability of the detector response, dose linearity and dose-rate dependency were firstly evaluated. Comparative
dose measurements were performed by means of percent depth dose
curves and lateral beam profiles. ICRU 78 recommended beam parameters were used to compare the percent depth dose curves and
lateral profiles obtained using the SCDD and the reference ionization
chamber.
Results: During warm-up/stability test, the diamond detector showed
maximum deviation from the average reading less than 0.5%. The detector response as a function of dose was linear with deviations below
0.5% over a 50 cGy e 500 cGy dose range. The detector response was
also found to be dose rate independent, with deviations below 0.5% in
the investigated dose-rates. Percent depth dose curves and lateral beam
profiles obtained with the diamond detector were in good agreement
with those obtained using reference dosimeters. Percentage depth dose
curves were found in good agreement with the ones from reference
dosimeters and beam profiles evidenced the good spatial resolution
capability of the device.
Discussion: The performed dosimetric tests evidenced that the SCDD
response is stable, reproducible and LET independent, thus indicating its
suitability for accurate relative dosimetric measurements in large and
small field clinical proton and carbon-ion beams.
19
EVALUATION OF DNA DAMAGES INDUCED BY PHOTON AND PROTON
MINIBEAM RADIATION THERAPY (MBRT): A MONTE CARLO STUDY
M. Dos Santos a, R. Salmon a, C. Villagrasa b, Y. Prezado a. a IMNC, Imagerie et
Mod
elisation en Neurobiologie et en Canc
erologie, Orsay, France; b IRSN,
Institut de Radioprotection et de Suret
e Nucl
eaire, BP17, 92962 Fontenayaux-Roses, France
Nowadays, radiation therapy (RT) is one of the most effective methods
to treat cancers. Nevertheless, for radio-resistant tumors, RT is only
palliative due to the tolerances of the surrounding healthy tissues.
In order to overcome this limitation, the close bind of physics and
biology in RT may be exploited: the modification of some physical parameters, like the method of dose delivery, leads to different biological
outcomes.
Following this idea, two innovative approaches are under development:
photon and proton Minibeam Radiation Therapy (MBRT). They are based
on the combination of a spatial fractionation of the dose and the use
submillimetric field sizes (500 e 700 mm). The resulting dose profiles
consist in peaks and valleys [PRE09]. This type of dose delivery has proven
a remarkable tissue-sparing [DIL06, DEM12]. In parallel, significant tumor
growth delay was observed in highly aggressive tumor models (glioblastoma multiforme) [DEM12, PRE12].
However the biological basis are not yet well-understood. In order
to deepen the knowledge of the possible mechanisms, a nanodosimetric study has been performed. DNA damages induced by
MBRT at different depth on peaks and valleys regions have been
calculated by using Monte Carlo simulations (Geant4/Geant4-DNA)
[AG06, INC10].
Irradiations with proton (105 MeV) and photon (mean energy of 80 keV)
minibeams were simulated. As a target, a detailed DNA geometrical
model of a neuronal cell was generated. This geometry is composed of a
spherical nucleus of 10 mm in diameter and fill with nucleosomes
composed of a cylindrical histone wrapped by roughly two turns of DNA
double helix (200 bp) [DOS13]. The energy transfer points located on
the DNA were recorded and analyzed with an adapted clustering algorithm allowing the detection of DNA strand breaks (simple or double)
[DOS13, FRA11].
This has been the first nanodosimetric study in the context. The first results have shown an increase of the number and complexity (number of
energy transfer points composing the break) of single and double strand
breaks with the depth, so with radiation LET due to the increasing of the
track density. Theses results seem to corroborate the remarkable healthy
tissue-sparing with this promising RT technique.
Keywords: Mini Beam Radiation Therapy, Monte Carlo simulations, DNA
damages.
[AGO03] S. Agostinelli et al. Geant4: a simulation toolkit. NIMA 506, 250303 (2003).
[DIL06] F.A. Dilmanian et al., “Interlaced x-ray microplanar beams: A
radiosurgery approach with clinical potential”, Proc. Natl. Acad. Sci. USA
103, 9709e9714 (2006).
[DEM12] P. Deman et al., “Monochromatic minibeams radiotherapy: from
healthy tissue-sparing effect studies toward first experimental glioma
bearing rats therapy”, Int. J. Radiat. Oncology Biol. Phys. 82, e693ee700
(2012).
[DOS13] M. Dos Santos et al. Infleunce of the DNA density on the number of
clustered damages created by protons of different energy. NIMB 298, 47-54
(2013).
[FRA11] Z. Francis, C. Villagrasa, I. Clairand. Simulation of DNA damage
algorithm after proton irradiation using an adapted DBSCAN algorithm.
Comput. Meth. Programs Biomed. 101, 265-270 (2011).
[INC10] S. Incerti et al. Comparison of Geant4 very low energy cross section
models with experimental data in water. Med. Phys. 37, 4692-4708 (2010).
[PRE09] Y. Prezado et al “A new method of creating minibeam patterns for
syn- chrotron radiation therapy: a feasibility study”, J. Synchr. Radiat. 16,
582e586 (2009).
[PRE12] Y. Prezado, S. Sarun, S. Gil, P. Deman, A. Bouchet, G. Le Duc, “Increase of lifespan for glioma-bearing rats by using minibeam radiation
therapy”, J. Synchrotron Radiat. 19, 60e65 (2012).
20
Abstracts / Physica Medica 30S1 (2014)
CHARACTERIZATION OF GALLIUM NITRIDE RADIOLUMINESCENT
TRANSDUCERS FOR DOSIMETRY AND QUALITY ASSURANCE IN HDR
BRACHYTHERAPY
MEASUREMENT OF THE ATTENUATION OF HYALURONIC ACID IN THE
RECTAL PROTECTION DURING PROSTATE CANCER TREATMENT WITH
HIGH DOSE RATE BRACHYTHERAPY
Pierrick Guiral a, Patrice Jalade a, Julien Ribouton a, Patrick Pittet b, Ruoxi
Guo-Neng
Lu b,
Jean-Marc
Galvan c,
Denis
Wang 2,
Dauvergne d. a Hospices Civils de Lyon (HCL); Service de Physique et de
Radioprotection du Centre hospitalier Lyon Sud (CHLS), Pierre-B
enite Fe de Lyon; Institut des Nanotechnologies de Lyon
69495, France; b Universit
INL-UMR5270, CNRS, Universit
e Lyon 1, Villeurbanne F-69622, France;
c
Universit
e de Lyon; Institut des Nanotechnologies de Lyon INL-UMR5270,
e de Lyon; Institut de
CNRS, CPE, Villeurbanne F-69622, France; d Universit
Physique Nucl
eaire de Lyon IPNL, IN2P3/CNRS, Universit
e Lyon 1,
Villeurbanne F-69622, France
nchez Mazo
n a, A. Man
~ anes Pe
rez b,
J. Sa
M.A.A.S. García
Blanco a, Mendiguren Santiago a, P.J. Prada a. a Servicio de Oncología
pica, Hospital Universitario Marqu
Radiotera
es de Valdecilla. Avenida
Valdecilla s/n, 39008 Santander. Spain; b Departamento de Física Moderna,
Universidad de Cantabria. Avenida de los Castros s/n, 39005 Santander.
Spain
High dose rate brachytherapy (HDR-BT) treatments are typically administered in large dose per fraction (>5 Gy) and with high-gradient-dosedistributions, with serious consequences in case of treatment delivery
error. Thus, Quality Assurance (QA) and in vivo Dosimetry (IVD) should be
systematically and independently implemented. However, their use remains limited due to some instrumental issues [1]. For QA and IVD in
HDR-BT, we propose the use of Gallium Nitride (GaN) radioluminescent
transducers. They have a real time dosimetric response and their small
size (volume <0.4 mm3) makes them suitable for punctual dose measurements in high-dose-gradient profiles. Our studies include both
characterization of radioluminescence (RL) properties of GaN transducers
under 192Ir and 60Co irradiations and modeling of their dosimetric
response in such irradiation conditions. For the former, a QA instrumented phantom implementing GaN transducers has been designed and
tested for source strength verification (within ±5%), for seed position
monitoring (within ±2 mm), and of dwell time measurements (within
100 ms). For the latter, a GaN dosimetric response model based on
anisotropic TG43 formalism and specific correction factors for energy
dependence has been developed. GaN dosimetric response to HDR irradiations has also been studied by Monte Carlo (MC) simulations, with
obtained results in good agreement with measurements. These studies
confirm that GaN Transducers can be implemented for QA and IVD in
HDR-BT.
New techniques in Brachytherapy, either as an exclusive treatment or
combining both external radiotherapy and hormonal therapy, allow for
increasing the radiation dose to the prostate in order to achieve appropriate local tumour control [1,2]. The increasing doses produce nonnegligible rectal complications. Actually, the impact on late rectal bleeding
of grade II to 4 can be as high as 17% [3].
This research aims to determine the possible reduction in the rectal dose
due to the transperineal injection of hyaluronic acid (Restylane®) in the
anterior perirectal fat of the rectum. For that purpose, we have measured
the radiation attenuation in hyaluronic acid, and compared it to the
attenuation in water (which mimics natural tissues). In order to perfectly
control the geometry of the problem, we have used a 133Ba source instead
of the 192mIr conventional one, as 133Ba has one energy peak close to 308
keV (the most probable 192mIr energy peak), and it is less radioactive,
therefore easier to work with.
We placed the hyaluronic acid between the 133Ba source and a NaI scintillation detector (see Figure 1). Then we measured the photon attenuation
varying the mass thickness (see Figure 2). As can be seen in the green curve
in Figure 2 (E ¼ 299.9 keV, the closest to the most probable 192mIr energy
peak) the nature of the hyaluronic acid helps with the radiation
attenuation.
Fig. 1 Normalized measured response of GaN compared to MC simulated GaN response
as a function of the axial distance from GaN probe to a 192Ir source. Water response as
a function of the axial distance given by TG-43 protocol is plotted too for over-response
comparison. The source position is considered to be at 0 cm.
[1] K. Tanderup et al., “In vivo dosimetry in brachytherapy”, Medical
Physics 40, 070902 (2013)
Fig. 1 Experimental setup for the measurement of the radiation attenuation in hyaluronic acid. The hyaluronic acid lies on top of the NaI scintillation detector.
Abstracts / Physica Medica 30S1 (2014)
21
Acknowledgement: This research has been co-financed by the European
Union (ESF) and Greek national funds through the Operational Program
“Education and Lifelong Learning Investing in knowledge society” of the
National Strategic Reference Framework (NSRF). Research Funding Program: Aristeia.
INDICES FROM DOSE-VOLUME HISTOGRAMS AS TOOLS FOR OPTIMIZED
BRACHYTHERAPY IN INTERSTITIAL IMPLANTS FOR TREATMENT OF
SARCOMAS
Gialousis G a, b, Papageorgiou Sp a, b, Kostakis V a, b, Vamvakas
I a, b, Maragoudakis Em b. a IASO hospital, medical physics department;
b
IASO hospital, radiation therapy department
Fig. 2 Natural logarithm of the counts (N) as a function of the mass thickness for
several 133Ba emission energies.
[1] Pollack A., Zaggars G., Starkschall G. et al., “Prostate cancer radiation
dose response: results of the M. D. Anderson phase III randomized trial”,
Int. J. Radiat. Oncol. Biol. Phys. 2002, 53, 1097-1105.
[2] Zelefsky M.J., Fuks Z., Hunt M. et al., “High-dose intensity modulated
radiation therapy for prostate cancer: Early toxicity and biochemical
outcome in 772 patients”, Int. J. Radiat. Oncol. Biol. Phys. 2002, 53, 11111116.
[3] Zelefsky M.J., Cowen D., Fuks Z. et al., “Long term tolerance of high dose
three dimensional conformal radiotherapy in patients with localized
prostate cancer”, Cancer 1999, 85, 2460-2468.
EXPERIMENTAL DOSIMETRY FOR MODEL-BASED
BRACHYTHERAPY TREATMENT PLANNING
192
IR
HDR
A. Moutsatsos, E. Pantelis, E. Pappas, P. Papagiannis. Medical Physics
Laboratory, Medical School, University of Athens, 75 Mikras Asias, 11527
Athens, Greece
Background: Model-based dose calculation algorithms (MBDCA) have
been recently introduced in 192Ir High Dose Rate (HDR) brachytherapy
treatment planning systems (TPS). Relative to the water-based TG43
dosimetry formalism, commissioning and quality assurance (QA) of
MBDCAs is rather demanding, since verification is required for dose distributions calculated in patient-specific scatter and material heterogeneity
conditions. A recently published report (TG186) recommends that both
experimental means and reference dosimetry data obtained using Monte
Carlo (MC) simulation should be used to verify MBDCA-based predictions.
This work aims to establishing an experimental, phantom-based procedure for commissioning and QA management of MBDCA-based TPSs, as
well as for benchmarking MC-calculated reference dose distributions.
Materials and methods: A PMMA phantom incorporating inserts of
different density and material composition was constructed from nonsymmetrical slabs, thus permitting measurements in non-isotropic scatter
conditions. PMMA slabs were properly machined to accommodate TLD
detectors, radiochromic films and a plastic catheter facilitating source
positioning. The phantom was CT-imaged and a treatment plan consisting
of multiple 192Ir source positions was prepared using the Oncentra® Brachy v4.4 TPS. Dose calculations of the Oncentra-ACE MBDCA were DICOMRT exported for further evaluation. Irradiation was delivered using a
microSelectron v.2 source. Reference dosimetry data were obtained using
the MCNP v6.1 MC code. In specific, the treatment plan along with the
phantom CT-images were imported into an in-house developed software
tool (BrachyGuide) used to automatically prepare a MCNP input file. Film
and TLD detector measurements were compared to corresponding MCand MBDCA-calculated results in terms of absolute point dose differences
and 2D relative dose and gamma index distributions.
Results and conclusion: Experimental and MC-calculated dosimetry results were found in agreement within corresponding uncertainties. Comparison of measured and TPS-calculated results showed also a good
agreement which deteriorates at large radial distances due, mainly, to
MBDCA assumptions and optimization settings. The proposed methodology combined with the slab-phantom described herein, provides an efficient experimental means for the quality management of MBDCA-based
TPSs.
Background: The Interstitial brachytherapy is an important tool for the
treatment of sarcomas. The aim is the optimal target coverage of Clinical
Target Volume (CTV) by the desired radiation dose with parallel conditions
not to irradiate healthy tissue and not to overdose important part of the
CTV because of dose distribution of the radioisotope. For this reason
qualitative indices derived from dose - volume histogram (DVH) characterizing the quality of the spatial coverage.
Materials and methods: The practical process begins by surgical implantation - placement of flexible catheters, the three-dimensional treatment planning and implementation of the plan to the patient. A key role is
the assessment of 3D-planning, made with the use of indices such as: dose
heterogeneity index (DNR), coverage index (CI), conformal coverage index
(COIN) and indices based on physical dose histogram - volume (NDVH) as
the quality index (QI) and the natural dose ratio (NDR). Some of the data
used in the calculation of indices are the total volume receiving a dose
equal to 150 % of the dose target volume and CTV receiving a dose equal to
100 % of the target dose. These values are calculated by Oncentra Brachy
v4.3.
Results: Good values considered for the DNR index are values of less than
35 % or 50 %, for CI values greater than 80% or 90 % and for COIN values
greater than 75% or 80 %. Also dose distribution is evaluated with the help
of other indices such as NDR. For NDR ¼ 1 the volume corresponding to the
implant is equal to the target volume and therefore the coverage is satisfactory, while values NDR <1 or> 1 indicate that the implant volume is
larger or smaller respectively than the target volume. The comparison and
optimization of indices in a spreadsheet finally derives an optimal treatment plan.
Discussion: DVH indices for interstitial brachytherapy sarcomas are a
handy tool to optimize coverage of the CTV, as used in real time during the
design of the plan. The results of calculations are also comparable with
values reported in the literature.
ANALYSIS OF ULTRASOUND ELASTOGRAPHY IMAGES FOR TUMOR
GUERIN CARCINOMA DURING MAGNETIC NANOTHERAPY
V.E. Orel a, T. Mitrelias b, c, M. Tselepi b, c, O.B. Dynnyk d, A.V. Romanov a, A.Y.
Rykhalskiy a, N.N. Barnes a, C.b Nikolov a,b, c, d, I.B. Schepotin a. a National
Cancer Institute / 33/43, Lomonosova Str., 03022, Kyiv, Ukraine; b Cavendish
Laboratory, University of Cambridge / JJ Thomson Avenue, Cambridge CB3
0HE, United Kingdom; c Cavendish NanoTherapeutics Ltd / CPC1 Capital
Park, Fulbourn, Cambridge CB21 5XE, United Kingdom; d Bogomoletz
Institute of Physiology / 4 Bogomoletz Str., 01024, Kyiv, Ukraine
The paper presents digital images of transplanted Guerin’s carcinoma in
rats during treatment with magnetic nanotherapy. The animals with
Guerin carcinoma treated by magneto-mechano-chemically synthesized
magnetic nanocomplex (MNC) based on Fe3O4 nanoparticles conjugated
with antitumor anthracycline row antibiotic doxorubicin and followed by
irradiation with local electromagnetic irradiation (EI) by spatially inhomogeneous constant magnetic and electromagnetic fields had a better
outcome than those treated with conventional doxorubicin and MNC
without EI. Color Doppler examination, elastography and dynamic viscosity were performed with the diagnostic ultrasound system “ULTIMA
SE” (Radmir, Ukraine). Previously studies nuclear magnetic resonance
images obtained over time showed that the application of local electromagnetic irradiation does not alter the position of the MNC in the tumor.
B-mode sonography demonstrated that injection of MNC in the tumor and
22
Abstracts / Physica Medica 30S1 (2014)
EI of the animals had echogenicity throughout the tumor, which characterized the increase in blood perfusion. Сolor Doppler ultrasound (US)
image of Guerin’s carcinoma showed that the largest decrease of vessel
area occurred after injection of MNC in the tumor after the application of
local EI. The elastography performed on diagnostic ultrasound system
showed that the injection MNC in tumor increased Young’s modulus for
Guerin’s carcinoma as compared to the group of animal without nanoparticles. These results here suggest that US elastography may provide a
useful method to monitor the effectiveness of treatment of cancer patients
during magnetic nanotherapy.
Кеуwords: Tumor; Magnetic Nanotherapy; Digital Images; Magnetic Nuclear Resonance; Ultrasound; Elastography
EVALUATION OF CO-OCCURRENCE TEXTURE FEATURES ON AM-FM
INSTANTANEOUS AMPLITUDE FOR BREAST DENSITY CLASSIFICATION
Styliani Petroudi a, Ioannis Constantinou a, Marios Pattichis b, Chrysa
Tziakouri c, Constantinos Pattichis a. a Department of Computer Science,
University of Cyprus, Nicosia, Cyprus; b Department of Electrical and
Computer Engineering, University of New Mexico, New Mexico, USA;
c
Nicosia General Hospital, Nicosia, Cyprus
Mammographic breast density has been recognized as an important risk
for developing breast cancer. Depending on her mammographic breast
density a woman may benefit from additional screening, other than
mammography.The American College of Radiology describes mammographic breast density with the Breast Imaging Reporting and Data
System (BI-RADS) 4-class density categorization.Women with dense
breasts are at a 4-6 times higher risk for developing breast cancer.
Different methods are being developed for automatic breast density
classification.
Amplitude-Modulation Frequency-Modulation (AM-FM) methods provide image decompositions that describe non-stationary content and
capture instantaneous variations in amplitude, frequency and phase. The
Instantaneous Amplitude (IA) reflects the local image texture contrast.
This work presents the estimation of texture features on normalized IA
co-occurrence matrices evaluated for different frequency scales using
AM-FM. AM-FM demodulation is used to estimate the IA at different
frequency scales using a Gabor filterbank and multi-scale Dominant
Analysis. Following normalized co-occurrence matrices are evaluated for
different cell distances on the IA estimates for each scale, for the
segmented breast region. They are used to capture the relative variations
in the breast tissue characteristic to the different breast density classes.
The co-occurrence matrices are evaluated for a number of different distances as the IA is slow-varying. Then, different second-order statistical
and other features such as contrast, correlation, entropy, etc. are evaluated on the IA co-occurrence matrices for each AM-FM frequencies scale.
These values are used to characterize the mammographic breast density.
Classification of a new mammogram into one of the density categories is
achieved using the k-nearest neighbor method and the Euclidean distance metric.
The method is evaluated using the BI-RADS mammographic density
categorization on the Medical Image Analysis Society mammographic
database and the classification accuracy of over 82% is most favorably
compared to other methods in the literature.
AM-FM provides the IA from a very very low frequency scale to a very high
frequency scale and thus encapsulates differences in mammographic
appearance e.g homogeneity vs heterogeneity that characterize different
mammographic density variations. Additionally, the multi-scale texture
analysis methodology captures both structural and statisticalinformation
for the different scales and uses a compact set of features that effectively
quantify mammographic parenchyma characteristics; leading to high
classification accuracy.
Keywords: Medical Image Analysis, Texture, Classification, Mammography, Amplitude-Modulation Frequency-Modulation
Acknowledgements: This work is supported by the Cyprus Research
Promotion Foundation's Grant ΤPЕ/ΟРІΖΟ/311(ВІЕ)/29 and is co-funded
by the Republic of Cyprus and the European Regional Development
Fund.
A PATTERN RECOGNITION SYSTEM FOR COLORECTAL CANCER
CHARACTERIZATION, BASED ON AIB STAINED HISTOPATHOLOGICAL
IMAGES
Angeliki Theodosi a, Spiros Kostopoulos b, Dimitris Glotsos b, Vassiliki
Panagiota
Ravazoula c,
Dionisis
Cavouras b,
George
Tzelepi c,
Sakellaropoulos a. a Department of Medical Physics, School of Medicine,
University of Patras, 26500 Rion, Greece; b Medical Image and Signal
Processing
Laboratory,
Department
of
Biomedical
Engineering,
Technological Educational Institute of Athens, Egaleo, Athens, Greece;
c
Department of Pathology, School of Medicine, University of Patras, Rion,
Greece
Background: Colorectal cancer is the third most common malignancy and
early detection is vital in patient treatment. Routine clinical diagnosis and
histological tumour grade assessment is based on qualitative features
observed under the microscope on biopsy material, stained with
Нaematoxylin and Eosin (H&E). The nuclear coactivator 3 (NCOA3 or AIB)
has been previously shown to be an important prognostic factor regarding
various pathological regions, other than colorectal cancer. The purpose of
the present study is to develop an image analysis methodology for
discriminating between low and high grade colon cancer lesions, employing
microscopy images of biopsy material, stained for AIB protein expression.
Materials and methods: Clinical material comprised thirty eight biopsies of
colon carcinomas that were H&E stained, for histological tumour grade
assessment, and immunohistochemically (IHC) stained, for AIB protein
expression. Clinical diagnosis was performed by two experienced histopathologists in collaboration with the Department of Pathology, University
Hospital of Patras. Nine cases were characterized as of high grade and
twenty nine as of low grade. Each case was represented by four gray-scale
microscopy images, digitized from regions indicated by the physicians. Images were digitized using a light microscope. A set of 40 textural features
were calculated from the images, based on first and second order statistics. A
pattern recognition system (PR-system) was developed, that takes as input
textural features extracted from AIB expressed regions and characterizes the
images into low and high grade malignancies. Three different classifiers
(kNN, PNN, and SVM) were employed and were evaluated by means of the
leave one out (LOO) method. The PR-system was also tested for ‘unseen’
cases by means of External Cross Validation (ECV) method.
Results: In discriminating low from high grade colorectal cancer images,
the PR-system achieved 85% accuracy. Optimal number of features
employed in the design of the PR-system carried useful and distinct
textural information regarding differences in texture homogeneity between grades that could be of value to the physicians.
Conclusion: Preliminary results show that textural features, based on AIB
staining of biopsy material, may contain important information for the
characterization of colorectal cancer and that employing pattern recognition methods may be of assistance to pathologists, as a second opinion
diagnostic tool.
ULTRASOUND ELASTOGRAPHY IMAGE PROCESSING FOR THE
DIAGNOSTIC APPROACH OF CHRONIC HEPATITIS AND LIVER CIRRHOSIS
P.S.
Zoumpoulis a,
I.
Mathioudakis a,b, c, d, e,
O.
I.
Theotokas a,
Karapanagiotou e, E. Gatos a, E. Manessis b, M. Shina c, I. Vafeiadi d, E.
a
I.
Mastorakou e,
G.
Mousoulis c.
Diagnostic
Panteleakou a,
Echotomography S.A., 317C Kifissias Ave., GR 14561, Kifissia, Greece;
b
Euroclinic Athens, 9 Athanasiadou Str. & D. Soutsou Str., GR 11521, Athens,
Greece; c Evagelismos Hospital, 45-47 Ipsilantou Str, GR 10676, Athens,
Greece; d Laiko General Athens Hospital, 17 Ag. Thoma Str., GR 11527,
Athens, Greece; e Onassis Cardiac Surgery Center, 356 Sygrou Ave., GR
17674, Kallithea, Greece
Background: This study compares two methods of liver elasticity determination, Shear Wave Elasticity (SWE) and Trancient Elastography (VCTEFibroscan). Images will be provided by a group of patients with chronic
parechymal liver diseases which will be compared against histological
liver biopsy findings of the same patients.
Materials and methods: 55 consecutive patients with chronic liver disease with liver biopsy and histology examination were included in the
Abstracts / Physica Medica 30S1 (2014)
study. Findings were compared with elastography measurements from 50
normal subjects. А B-Mode and Color/Power Doppler examination is
performed on each patient for examining liver morphology and hemodynamic study of the portal vein.
1. SWE: All SWE measurements were performed in the right lobe of the
liver using an appropriate intercostal space.
Every patient is examined by two different examiners, using the same
examination protocol and the same acoustic window, in order to estimate
the Inter Observer variability.
Each examiner performs two different measurements on each patient
using the same examination protocol and the same acoustic window, in
order to estimate the Intra Observer variability.
2. VCTE: All VTCE measurements were performed in the right lobe of the
liver using the same intercostal space.
Anthropometric measurements at the time of SWE and TE should include
information from patient’s record about the type of liver disease and histological evaluation of liver biopsies.
Results: There was a statistically significant difference (p<0.01) between
the elastography values of normal and diseased subjects with both VCTE
and SWE methods. There was a good correlation when the values of the
two methods were compared between each other and each one with the
liver biopsy, where available. In addition, intra- and inter-observer variability was low with both methods, if the adequate strict protocol of study
was applied.
VCTE showed 82.3% sensitivity and 68.2% specificity in diagnosing liver
cirrhosis at a cut-off value of 11,9 kPa.
SWE showed 88.5% sensitivity and 74.2% specificity in diagnosing liver
cirrhosis at a cut-off value of 12,8 kPa.
Discussion: Although the number of patients included in this prospective
study is small, it was clearly shown that VCTE and SWE can definitely
differentiate normal from fibrotic liver tissue. There is also differentiation
with SWE between F1-F2 stages of fibrosis and F3-F4 appearing more
evident comparing with discrimination offered by VCTE (Fibroscan). Larger
number of patients is needed in order to investigate whether VCTE and
SWE are able to differentiate between various stages (F1, F2, F3, F4) of
fibrotic liver disease.
THE IMPORTANCE OF MR MULTIPARAMETRIC DIFFERENTIAL
DIAGNOSIS. FASMA. A CLINICAL DECISION SUPPORT SYSTEM
Ioannis Tsougos a, Evangelia Tsolaki a, Patricia Svolos a, Evanthia
Eftychia
Kapsalaki b,
Ioannis
Fezoulidis b,
Kostas
Kousi a,
Fountas c, Constantine Kappas a, Kyriaki Theodorou a. a Medical Physics
Department, Medical School, University of Thessaly, 41110, Biopolis, Larissa,
Greece; b Department of Radiology, Medical School, University of Thessaly,
41110, Biopolis, Larissa, Greece; c Department of Neurosurgery, Medical
School, University of Thessaly, 41110, Biopolis, Larissa, Greece
Background: Accurate brain tumor diagnosis plays a crucial role in the
selection of the optimum treatment strategy and overall improves the
therapeutic outcome. A clinical decision support system (CDSS) for brain
tumor classification can be used to assist in the diagnosis and grading of
brain tumors. A Fast Spectroscopic Multiple Analysis (FASMA) system that
uses combinations of multiparametric MRI data sets was developed as a
CDSS for brain tumor classification.
Materials and methods: MRI metabolic ratios and spectra, from long and
short TE respectively, as well as diffusion and perfusion data were acquired
from the intratumoral and peritumoral area of 126 patients with untreated
intracranial tumors. These data were categorized based on the pathology,
and different machine learning methods were evaluated regarding their
classification performance for glioma grading and differentiation of infiltrating vs. non-infiltrating lesions. Additional databases were embedded to
the system, including updated literature values of the related MR parameters and typical tumor characteristics (imaging and histological), for
further comparisons. Custom Graphical User Interface (GUI) layouts were
developed to facilitate classification of the unknown cases based on the
user's available MR data.
Results: The highest classification performance was achieved with a
support vector machine (SVM) using the combination of all MR features.
FASMA correctly classified 89% and 79% in the intratumoral and peritumoral area respectively for cases from an independent test set. FASMA
23
produced the correct diagnosis, even in the misclassified cases, since
discrimination between infiltrative vs. non-infiltrative cases was
possible.
Discussion: FASMA is a prototype CDSS, which integrates complex quantitative MR data for brain tumor characterization. FASMA was developed as
a diagnostic assistant that provides fast analysis, representation and
classification for a set of MR parameters. This software may serve as a
teaching tool on advanced MRI techniques, as it incorporates additional
information regarding typical tumor characteristics derived from the literature.
CORRELATION BETWEEN HIP MUSCLES MRI TEXTURE PARAMETERS
AND FEMORAL NECK BONEAREAL BONE MINERAL DENSITY (ABMD)
IN DIFFERENT ATHLETES GROUPS
Gabriel Nketiah a, Harri Sievanen b, Hannu Eskola a. a Department of
Electronics and Communications Engineering, Tampere University of
Technology, Tampere, Finland; b The UKK Institute for Health Promotion
Research, Tampere, Finland
Background: Both skeletal muscles and bones are known to adapt to
specific long-term loadings to which they are subjected [1, 2]. A number of
studies have been conducted on the relationship between muscle and
bone traits in different athletegroups[3-5], but no study has employedtexture analysis (TA) method especially in the hip region.TA describes
thetextural propertiesofa digital image by examining the gray-level spatial
distribution within an image, and quantifying these propertiesusing
textural features (mathematical parameters).We therefore exploredMRI
TA as a potential means to study how hip muscles and femoral neck
boneare correlated in terms of specific exercise-loadings.
Materials and methods: The study comprised ofninety-oneelite female
athletes representing five distinct exercise-loading groups: high-impact
(triple- andhigh-jumpers), odd-impact (soccer and squash players), highmagnitude (power-lifters) low-impact (endurance runners)and nonimpact (swimmers) [7].Axial 3D T1-weighted FLASH sequence images of
the proximal femur, and femoral neck areal bone mineral density (aBMD)
were acquiredfrom the dominant hip region of each subject using a 1.5T
MRI and dual energy X-ray absorptiometry respectively.
Four selected 2Dco-occurrence matrix-basedtexture parameters were
computed [8] from the MRI images of four hip muscles (gluteus maximus,
gluteus medius, iliopsoas and obturator internus), and femoral neck
trabecular bone. Correlation (Spearman) betweenfemoral neck aBMD
andhip muscle MRItexture parameterswere studied in the athlete groups.
Results: Generally, the correlation between hip muscle MRItexture parameters andfemoral neckaBMD were low (Table 1). However, some
moderateand significant correlations (both positive and negative)were
also observed, especially in the gluteus maximus and gluteus mediusmuscles of the high-impact and high-magnitude exercise-loading
athlete groups.
Table 1 Correlation between DXA-measured areal Bone Mineral Density
(aBMD) at the femoral neck andhip muscle MRI texture parametersin five
different athletes groups.
Athlete
Group
High-impact
Odd-impact
Angular second
moment
Entropy
N
Muscle
S(4,0)
S(4,4)
S(4,0)
S(4,4)
19
Gluteus maximus
Gluteus medius
Iliopsoas
Obturator
internus
-0.567*
-0.437
-0.335
0.020
-0.249
-0.422
-0.094
0.054
0.567*
0.496*
0.343
0.020
0.230
0.460
0.073
-0.054
Gluteus
maximusmaximus
Gluteus medius
Iliopsoas
Obturator internus
-0.301
0.307
0.301
-0.333
0.218
-0.042
-0.197
0.286
0.096
0.440
-0.218
0.040
0.197
-0.218
-0.089
-0.437
19
(continued on next page)
24
Abstracts / Physica Medica 30S1 (2014)
MR COMPATIBLE ENDOSCOPE FOR ASSESSING THE SPATIAL
DISTRIBUTION OF CO-REGISTERED OPTICAL AND 1H SIGNALS
(continued )
Athlete
Group
Highmagnitude
Low-impact
Non-impact
Angular second
moment
Entropy
N
Muscle
S(4,0)
S(4,4)
S(4,0)
S(4,4)
-0.493
-0.565*
0.508*
0.567*
17
Gluteus
maximusmaximus
Gluteus medius
Iliopsoas
0.681**
-0.330
-0.108
0.200
-0.711**
0.276
0.209
-0.200
Obturator internus
0.541*
0.341
-0.541*
-0.341
Gluteus maximus
Gluteus medius
Iliopsoas
Obturator internus
0.102
-0.049
-0.106
0.158
0.115
0.044
-0.174
-0.228
-0.161
0.042
0.166
-0.146
-0.115
-0.050
0.143
0.223
Gluteus maximus
Gluteus medius
Iliopsoas
Obturator internus
-0.032
-0.270
-0.410
-0.386
0.032
0.270
0.337
0.276
-0.488*
-0.282
-0.381
-0.064
0.488*
0.282
0.386
0.064
18
18
*
p < 0.05; **p < 0.01; N: number of subjects.
Co-occurrence matrix-based texture parameters (Angular second moment
(AngScM) and Entropy (Entr)) [9]were computedfrom each region of interest (10 x 10 pixels) for four directions (q ¼ 0 , 45 , 90 , 135 ) and at 1-4
distances (d ¼ 1, 2, 3, 4 pixels) resulting in a total of 32 parameters. Angular
second moment and entropychosen because they have been shown to
correlate well with trabecular bone structural indices [10].
To determine the most relevant parameters, a correlation between the
trabecular bone MRI texture parameters and DXA-measured aBMD was
tested. Parameters computed in 0 and 90 and at a distance of 4 pixels (i.e.
s(4,0)AngScM, s(4,4)AngScM; s(4,0)Entr, s(4,4)Entr) showed higher and
consistent correlation, and were therefore selected for further analysis.
Discussion: Skeletal muscles and boneswork in synchrony to support the
body in motion, hence knowledge about how these two correlate during
loading would be important in understanding and preventing certain
musculoskeletal problems(e.g. fracture, osteoarthritis). In this study we
found correlation between the textureof gluteus maximus and gluteus
medius muscles and femoral neck bone mineral density for high-impact
and high-magnitude exercise. To explain these results, more specific
studies are needed.
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[5] Nordstro
altered relationships between bone mass, muscle strength, and body
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[7] Nikander R, Kannus P, Dastidar P, Hannula M, Harrison L, Cervinka T,
Narra NG, Aktour R, Arola T, Eskola H, Soimakallio S, Heinonen A, Hyttinen
€nen H. Targeted exercise against hip fragility. Osteoporos Int 2009:
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ski PM, Strzelecki M, Materka A, Klepaczko A. MaZda e a
[8] Szczypin
software package for image texture analysis. Comput Methods Programs
Biomed 2009: 94: 66e76.
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classification. IEEE Trans Syst Man Cybern 1973: 3: 610e621.
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Junmo
An a,
Andrew
Webb b,
Ioannis
Seimenis c,
Eftychios
Christoforou d, Nikolaos V. Tsekos a. a Medical Robotics Laboratory,
University of Houston, Houston, TX, USA; b C.J. Gorter Center for High Field
MRI, Leiden University Medical Center, Leiden, Netherlands; c Medical
Physics Lab, Medical School, Democritus University of Thrace,
Alexandroupolis, Greece; d Department of Electrical and Computer
Engineering, University of Cyprus, Cyprus
Background: We describe an MR compatible endoscope that combines an
optical sensor for light-induced fluorescent (LIF) and a micro-MRI coil for
loco-regional biosensing of tissue that (I) co-registers MR image, LIF and
MR 1H spectra, and (II) mechanically scans to assess the spatial distribution of fluorophores (LIF) and metabolites (MRS).
Methods: The optical/MR probe composes of: (1) a 1.25mm 7-fiber optical sensor (6 fibers emit light from a 450nm LED and 1 for reception),
(2) a 2.3mm RF coil and (3) a mechanical scanner using a PiezoWalk
motor. This probe was tested on a three-compartment phantom with
characteristic optical (Fig. 1(a)) and 1H (Fig. 1(b)) signals: (I) comp-1
water-based gelatin (1H at 4.9 ppm) and fluorescein for LIF, (II) comp-2:
oil-based gelatin (1H peak at 1.4 ppm) and no fluorophore and (III) comp3: water-based gelatin with choline (1H at 3.3 ppm) and fluorescein/
rhodamine-B for LIF..
Results: The presence and operation of the probe and manipulator had
no effect on the SNR of acquired GRE images and 1H spectra. Figure 1
shows spectro-spatial contour plots for both modalities clearly demonstrating the two boundaries between the three compartments. LIF
spectra (Fig. 1(a)) show fluorescein in comp-1, Rhodamine-B/fluorescein
in comp-3, and lack of any signal in comp-2. MRS spectra (Fig. 1(b))
exhibit identical patterns: comp-1 has only water signal(not shown),
comp-2 has oil signal (peak at 1.4 ppm), and comp-3 has choline (peak at
3.3 ppm). Spatial matching was within the LIF/MRS mechanical resolution of 0.5 mm: the boundaries from MRI were calculated at -9.2 and +3.3
mm, from LIF spectro-spatial plot at -8.8 and +3.6 mm and from MRS at
-8.2 and +3.7 mm.
Discussion: A forward looking MR compatible optical/MR probe for
assessing the spatial distribution of co-registered optical and 1H signal
sources using a pull mechanical scan is described and tested. The use of MR
and optical sensors can have impact in improving diagnosis in situ, as well
as in performing basic research in vivo. For instance, it may enhance the
detection of tumor margins and even used to guide biopsies.
HIGH RESOLUTION MR EYE PROTOCOL OPTIMIZATION: COMPARISON
BETWEEN 3D-CISS, 3D-PSIF AND 3D-VIBE SEQUENCES
Irene Tsiapa a, d, Miltiadis K. Tsilimbaris c, Penelope Bouziotis d, Apostolos
H. Karantanas b, Ioannis G. Pallikaris c, Thomas G. Maris a. a Department of
Medical Physics, University of Crete, Heraklion, Crete, Greece; b Department
of Radiology, University of Crete, Heraklion, Crete, Greece; c Department of
Ophthalmology, University Hospital of Crete, Heraklion, Greece; d Institute
for Nuclear and Radiological Sciences, Technology, Energy and Safety,
National Center of Scientific Research “Demokritos”, Aghia ParaskeviAthens, Greece
Background: The purpose of this study was to compare selected pulse
sequences for Magnetic Resonance Imaging (MRI) of the eye and to evaluate their potential for the depiction of specific anatomic regions of the
eye.
Materials and methods: A High-Resolution (100x100x600 mm) MRI protocol was developed on a 1.5-T clinical system and applied in the left eye of
an albino rabbit. Experiments were performed using T1w, T2w and postGd T1w sequences utilizing both a head or body coil and a small surface
coil. The comprehensive MR imaging protocol consisted of two 3D T2w
sequences: (reverse fast imaging with steady state precession (3D-PSIF),
constructive interference in steady state (3D-CISS)) and one 3D T1w
sequence: (volumetric interpolated breathhold examination (3D-VIBE)).
The T1w 3D-VIBE sequence was acquired, before and after intravenous
injection of 0.2 mmol/kgr gadolinium-DTPA. MR image artifacts presence
was rated subjectively utilizing a 5 point scale. Signal-to-Noise Ratios
Abstracts / Physica Medica 30S1 (2014)
(SNR) and Contrast-to-Noise Ratios (CNR) amongst specific eye anatomical
areas were calculated for each sequence.
Results: 3D-PSIF and 3D-CISS provide better delineation and visualization
of the eye as compared with 3D-VIBE sequences. 3D-PSIF provides better
visualization of the eye segments with better CNR between aqueous and
vitreous humor but lower visibility and discrimination for the eye surrounding tissues. In contrast, 3D-CISS had better SNR and provided the
best CNR amongst aqueous or vitreous humor and the eye surrounding
tissues. Severe H0 artifacts were present in eye tissues with higher T2
values (aqueous and vitreous humor). In post-contrast imaging, the T1w
3D-VIBE sequence provided the best SNR and CNR amongst the anatomic
layers of the eye which were clearly visualized by the specific sequence
and were not visible in any other T2w sequences.
Discussion: MRI offers unique advantages over existing retinal imaging
techniques, including the ability to image multiple layers without depth
limitation and to provide multiple clinically relevant data in a single
setting. The 3D-PSIF and 3D-CISS sequences can provide good anatomic
depiction of the eye segments on T2w-like images and could be combined
with T1w 3D-VIBE sequences, in post-contrast MR imaging, for a
comprehensive MRI protocol in high resolution MR eye imaging.
25
features in the future and is free for utilization upon request (dimglo@
teiath.gr).
Discussion: The proposed web-based platform may be used to automatically combine information from both radiological and microscopic findings for reducing potential sources of misinterpretations in breast cancer
diagnosis.
INNOVATIVE WEB-BASED DECISION SUPPORT SYSTEM FOR COMBINING
MAMMOGRAPHIC, HISTOLOGICAL AND CYTOLOGICAL IMAGE DATA IN
BREAST CANCER DIAGNOSIS
Spiros
Kostopoulos a,
Dimitris
George
Xenogiannopoulos a,
Glotsos a, Ioannis Kalatzis 1, Pantelis Asvestas a, Kostas Sidiropoulos b, Eirini Konstantina Nikolatou c, Panagiota Ravazoula d, Nikos
Dimitropoulos e, George Sakellaropoulos f, George Nikiforidis f, Dionisis
Cavouras a. a Department of Biomedical Engineering, Technological
Education Institute of Athens, Greece; b School of Engineering and Design,
Brunel University West London, Uxbridge, Middlesex, United Kingdom;
c
Department of Economic Sciences, University of Patras, Patras, Greece;
d
Department of Pathology, University Hospital of Patras, Greece; e Delta
Digital Diagnostic Center, Semitelou 6, Athens, Greece; f Department of
Medical Physics, School of Medicine, University of Patras, Patras, Greece
Background: Diagnostic mammography is the most important and reliable screening method for confirming the location, extent, and other
important clinical features of breast tumours. However, in early stage
cancer, the subtle differences between normal and abnormal tissues have
been proven challenging for viewing even by experienced physicians: up
to 30% of breast lesions are missed during routine diagnosis. In the presence of suspected lesion(s), pathologists are called to reach the final
diagnostic conclusion on the basis of visual evaluation of histological and/
or cytological material under the microscope. Although microscopic examination is a critical process for treatment planning, the potential of
diagnostic errors still remains substantially high; even the most experienced pathologist’s diagnosis is sometimes a biased opinion. Recent
literature has highlighted that diagnostic, prognostic, and predictive misinterpretations in breast cancer management can be reduced by
combining information from both radiological and microscopy findings.
Material and methods: This paper introduces a web-based decision support tool (Figure 1) that was designed to combine information from
radiological and histological images of breast cancer from the same patient
in order to be used as a second opinion tool by expert physicians. The beta
version of the platform is accessible upon request (http://medisp.bme.
teiath.gr:9090) and in its current form can be used to automatically
separate low from high grade breast cancer cases. The platform requires a/
the user’s estimation regarding the mammographic appearance of potential findings, such as breast density, microcalcifications etc, b/ a the
user’s estimation regarding the histological appearance of biopsy material,
such as necrosis, vascularity, mitoses, cellularity etc, c/ at least one microscopy image at 40x magnification stained with Haematoxylin and Eosin
and d/ optionally the mammographic image. The beta version incorporates
a series of automated image processing steps involving enhancement and
segmentation (Laplacian of Gaussian filter, Canny edge detection,
morphological opening and closing), image analysis (morphological
feature extraction) and classification (Probabilistic Neural Network classifier). The user automatically receives the classification result in text
format. The platform will expand to accommodate more user-friendly
Fig. 1 Web-based decision support system for diagnosis of breast cancer.Ă
Keywords: Breast cancer, Mammography, Histology, Cytology, Microscopy,
Decision support system
Acknowledgements: This research has been co-funded by the European
Union (European Social Fund) and Greek national resources under the
framework of the “Archimedes III: Funding of Research Groups in TEI of
Athens” project of the “Education & Lifelong Learning” Operational
Programme.
Ă
OBJECTIVE NOISE EVALUATION IN DIGITAL MAMMOGRAPHY, TOWARDS
IMAGE QUALITY TRACKING OF CLINICAL IMAGES
A. Ivory a, C. Walsh b, S. Cournane b. a School of Medicine, Trinity College
Dublin, Ireland; b Department of Medical Physics & Bioengineering, St
James's Hospital, Dublin 8, Ireland
Background: European guidelines for assessing image quality of Full Field
Digital Mammography (FFDM) systems recommend measurements taken
using unprocessed images of non-anthropomorphic test objects on an
annual basis.[1] These tests are preformed on raw unprocessed images and
do not assess the clinically relevant image processing algorithms of clinical
images and, due to the frequency of testing, for a period of time a reduction
26
Abstracts / Physica Medica 30S1 (2014)
in image quality may go unnoticed. To date no objective image quality
analysis techniques for ongoing assessment of clinical mammography images have been suggested in the literature. The purpose of this study is to
identify and assess potential noise measures for continuous objective image
quality evaluation of clinical images in digital mammography.
Methods: A number approaches were investigated to measure the noise
present in mammography images. A percentage noise method, based on a
noise threshold established using wavelet coefficients, similar to that used
by Luo et al. [2], was employed. Variance of parameters from a power law
fit of the NPS, as proposed by Cockmartin et al. [3], was also examined.
Initial investigations were carried out on both raw and processed images of
uniform physics phantoms and anatomical test objects by varying imaging
parameters and computationally incorporating noise.
Results: In preliminary tests, both methods investigated indicated
computationally simulated noise levels in images. On investigation of
processed images for physics phantoms and anatomical test objects, the
wavelet threshold method showed little variation in percentage noise. The
NPS beta fit parameter displayed variation similar to standard noise
measurements currently preformed on raw images.
Discussion: Application of the NPS method retrospectively to clinical images in normal operation and in the weeks preceding a detector failure will
be investigated and the method adapted to develop an objective metric
applicable to clinical images on a continuous basis in a remote setting.
Conclusion: This work investigates a novel application of noise power
spectrum evaluation for the purpose of monitoring changes in noise in
clinical images, if successful this method could be incorporated into a
remote image quality monitoring system in the future.
Key references
[1] European Guidelines for Quality Assurance in breast cancer screening
and diagnosis, Fourth Addition, Health and Consumer Protection, Directorate General
[2] Luo et al., Journal of Remote Sensing, 2006, 27(22):5003-5025
[3] Cockmartin et al, Medical Physics, 2013, 40,081920
AVERAGE
GLANDULAR
DOSE
IN
DIGITAL
MAMMOGRAPHY:
COMPARISON OF REAL TIME CALCULATIONS WITH RETROSPECTIVE
CALCULATIONS USING THE DICOM HEADER DATA
I.A. Tsalafoutas PhD, S. Kanellopoulou MSc. Medical Physics Department,
General Anticancer Oncology Hospital of Athens ‘Agios Savvas’, 171
Alexandras Avenue, 115 22, Athens, Greece
Objective: To investigate the accuracy of entrance surface air kerma (ESAK)
and average glandular dose (AGD) values calculated in real time by the
dosimetric software of digital mammography units.
Methods: 1241 mammograms performed in three identical digital
mammography units (Essential, General Electric Medical Systems) were
studied. Using appropriate software (DICOM Info Extractor), all patient
dose related parameters were extracted from DICOM headers into three
Microsoft Excel files (one for each unit). These files contained embedded
equations and algorithms to allow the retrospective calculation of ESAK
and AGD values automatically, using the DICOM header info and tabulated
values of ESAK to AGD conversion coefficients reported in relevant publications of Wu et al (1991, 1994), Dance et al (1990, 2000) and Boone et al
(1999, 2002).
Results: Real time calculated ESAK values agreed within ±10% with the
retrospectively calculated ESAK values for the whole sample studied. The
same was valid for the vast majority of real time calculated AGD values
when compared to those retrospectively calculated using Wu’s method,
since this is the method used by the mammography unit. The Boone’s and
Dance’s method resulted in slightly larger AGD values when the glandularity values given in the DICOM headers were used. However, when
typical glandularity values were used, much larger differences (up to about
50%) were observed for individual breasts, as a result of the large differences observed among the glandularity values given in the DICOM headers
and the Dance’s method typical glandularity values.
Conclusion: The accuracy of real time calculations of ESAK and AGD values
was considered satisfactory for all three units studied. However, it was
understood that comparisons among studies or mammography units with
respect to the AGDs should be made with caution, since different AGD
calculation methods are used. Some of them are based in real time estimated glandularity, some on typical glandularity values and others on the
assumption of 50%-50% breast composition. The estimation of the actual
breast glandularity remains a challenge for digital mammography unit
manufacturers.
CT OPTIMIZATION AND PERFORMANCE CHARACTERIZATION AFTER
THE INSTALLATION OF AN ITERATIVE RECONSTRUCTION ALGORITHM
Sofia D. Kordolaimi MSc a, Agapi Ploussi MSc a, Nektarios Kalyvas
PhD b, George Sthathis MD a, Athanasios Athanasakos MD a, Ioannis
Saradeas a, Stylianos Argentos MD a, Efstathios P. Efstathopoulos
PhD a. a 2nd Department of Radiology, Medical School, University of Athens,
Greece; b Technological educational institute of Athens, Department of
Biomedical Engineering, Greece
Background: In recent years, the rapid introduction of new imaging
technology in clinical practice has improved the role of diagnostic radiology in early diagnosis. The introduction of iterative algorithms (IR) in
clinical practice necessitates an initial optimization of CT exposure parameters with respect to diagnostic image quality prior to patient
examinations.
Purpose: The presentation of a methodology for the adjustment of the
exposure settings to the new requirements of an IR algorithm and the
evaluation of its performance.
Materials and methods: For that purpose, a CT quality assurance phantom
was multiply scanned for various settings and acquired images were
reconstructed with all available levels of the IR algorithm. For the evaluation and optimization of the system the parameters assessed were: CT
number accuracy, image noise (standard deviation measurements and
Noise Power Spectrum- NPS calculations), high contrast (by visual inspection and by Modulation Transfer Function- MTF calculations), low
contrast (by visual inspection and CNR calculations) and a Figure of Merit
(FOM) index. CTDIvol as displayed in the console was recorded, as well. For
the system optimization, a “useful” tube current- time product (mAs)
area,for each tube voltage, where the system functions according to the
manufacturer’s specifications, was determined. High mAs values that did
not further improve the image quality indices were excluded from this
area, as well.
Results: The “useful” mAs ranges were 300-600 mAs, for 80 kVp, 50-200
mAs for 120 kVp and 30-100 mAs for 140 kVp. FOM results indicated that
the optimum mAs-kVp settings were 300mAs-80kVp, 100mAs-120kVp,
and 90mAs-140kVp using the highest level of iterations corresponding to
CTDIvol of 5.7mGy, 6.5mGy and 8.7mGy, respectively. Concerning the IR
algorithm’s performance, noise was decreased with the increase of the IR
level however, noise texture did not change. High and low contrast resolution did not exhibit any variations from the use of IR algorithm.
Discussion: Authors developed an optimization/ performance characterization methodology for the integration of a new technology aspect in
clinical routine. The widespread availability of the phantom along with the
easily applicable methodology will facilitate that process.
3 YEARS’ EXPERIENCE WITH THE AUSTRALIAN NATIONAL MULTIDETECTOR COMPUTED TOMOGRAPHY DIAGNOSTIC REFERENCE LEVEL
SERVICE (NDRLS)
P. Johnston, A. Wallace, P. Marks, P. Thomas, T. Beveridge, A.
Hayton. Australian Radiation Protection and Nuclear Safety Agency,
Yallambie, Victoria, Australia
ARPANSA, in collaboration with various stakeholders have developed a
web based survey for individual imaging practices to log patient scanning
data for the construction of diagnostic reference levels for MDCT
(ARPANSA, 2014). The ARPANSA national adult DRL is the 75th percentile
(third quartile) of the spread of the median practice doses for common
MDCT protocols from a national survey of imaging practices. A local facility
reference level (FRL) is defined as the median value of the spread of doses
for common protocols surveyed at the local radiology practice for 20 patients. The MDCT DRLs have been derived from a nationwide survey of
local PRLs which, it is assumed, have produced images of acceptable
diagnostic quality as defined by the reporting specialist.
Abstracts / Physica Medica 30S1 (2014)
27
The Australian NDRLS has been acquiring MDCT DRL survey data since
August 2011. It is estimated that nationally there are 1000 scanners
distributed across 850 facilities. At the end of 2013, 217 facilities have
voluntarily registered with the NDRLS and approximately, of the 2400
surveys started, 1600 where completed. Each survey was categorized by
facility, scanner, patient age, scanned habitus (head, neck, chest, abdomenpelvis, chest-abdomen-pelvis, lumbar spine). A complete survey requires
20 patients and any number greater than 10 can be submitted. Patient
metrics include CTDIvol, DLP, weight, age and sex per acquisition. Participants are also required to record and log primary acquisition parameters
for use in future optimization strategies.
The current MDCT DRLs are shown in Table 1. Adult habitus DLP DRLs over
the 3 year period shows little variation at the 95% confidence interval as
demonstrated in figure 1. In early 2013 the NDRLS requested information
on the use of iterative reconstruction for protocols. Limited data across all
habituses supports the application of this technology, with a significant
dose reduction delivered per protocol see figure 2.
The NDRLS has shown that Australian MDCT doses are;
1. in the mid-range of international DRLs for similar scans,
2. relatively invariant over the past 3 years, and
3. reduced by the introduction of iterative reconstruction techniques.
Table 1
Australian MDCT DRLs.
MDCT Adult DRL
Protocol
Head
Neck
Chest
Abdomen-Pelvis
Chest-Abdomen-Pelvis
Lumbar Spine
MDCT Child (5-14 years) DRL
Head
Chest
Abdomen
MDCT Baby (0-4 years) DRL
Head
Chest
Abdomen
Fig. 1 Adult DLP DRL Variation.Ă
DLP (mGy.cm)
1000
600
450
700
1200
900
CTDIvol (mGy)
60
30
15
15
30*
40
600
110
390
35
5
10
470
60
170
30
2
7
Fig. 2 DLP (mGy.cm) reduction using iterative reconstruction for single phase acquisitions.
References:
ARPANSA. 2014. National Diagnostic Reference Level Service [Online]. Yallambie: ARPANSA. Available: http://www.arpansa.gov.au/services/ndrl/
index.cfm.
STUDY OF PAEDIATRIC EXPOSURE TO RADIATION
MICTURATING CYSTOURETHROGRAPHY PROCEDURES
DURING
Abdelmoneim Sulieman a, Esameldeen Babikir b, Khalid Alzimami b, Nada
Alrihaima c, Kiki Theodorou d. a Radiology and Medical Imaging
Department, College of Applied Medical Sciences, Salman bin Abdulaziz
University. P.O.Box 422, Alkharj11943, Kindom of Saudi Arabia;
b
Radiological Sciences Department, College of Applied Sciences, King Saud
University, P. O.Box 10219, Riyadh 11433, Saudi Arabia; c Sudan Atomic
Energy Commission, P.O.Box 55, Khartoum, Sudan; d Medical Physics
Department, University Hospital of Larissa, PO Box 1425, Larissa 41110,
Greece
Background: Paediatrics and children have been documented that
they have a higher risk of developing carcinogenic effect from the
irradiation than adults. Paediatric fluoroscopic procedures expose the
patients to a considerable radiation dose. Micturating cystourethrography (MCU) is one of the most radiographic procedures that performed
in paediatric patients. This study aims to measure the entrance surface
air kerma dose (ESAK) and effective doses for pediatric patients undergoing MCU.
Materials and methods: The study was carried out in five hospitals in
Khartoum. The ESAK dose was determined by using calibrated thermoluminescent dosimeters (TLDs- GR 200 A) for 167 children. Furthermore, the
surface dose was evaluated for the comforters. Patient's demographic data
and imaging parameters were recorded. Ethics and research committee
approved the study and informed consent was obtained from the parent
prior the procedure.
Results: The mean ESAK± sd and range (mGy) resulting from
MCU procedure has been estimated to be 2.2±0.5 (0.5-4.5) for the
total paediatric patient population. The mean effective dose was
0.45±0.1 per procedure. The mean the range of films and screening
time were 5.6 (4-7) and 1.1 ( 0.6-3.2) min at the same order per single
procedure.
Discussion: The radiation dose to the patients is well within established
safety limits in five hospitals, in the light of the current practice. All the
X ray machines have low X ray filtration compared to the European
guidelines. Pediatric patients exposed to unnecessary radiation as a
results of long fluoroscopic imaging, large number of films an inadequate training in pediatric procedures. A written protocol is required to
harmonize the practice for adoption a local dose reference level for dose
optimization.
28
Abstracts / Physica Medica 30S1 (2014)
CT RADIATION DOSE IN CHILDREN: A SURVEY TO ESTABLISH
AGE-BASED DIAGNOSTIC REFERENCE LEVELS IN MITERA HOSPITAL
(A PRIVATE MEDITERRANEAN HOSPITAL)
Tagkalakis Panayiotis, Zabelis Ioannis, Trimis Panayiotis, Tsatsaronis
Konstantinos,
Papaioannou
Georgia,
Paraskevopoulou
Chryssa.
Department of Imaging, Mitera Hospital, Athens, Greece
The aim of this study is to assess the doses delivered in Mitera Hospital -a
large private Mediterranean hospital- (Athens, Greece) to pediatric patients during computed tomography examinations of the brain, chest and
facial bones and to establish diagnostic reference levels (DRL) for different
age groups. All CT examinations are performed with a SIEMENS Somatom
Sensation 64 CT with Automatic Exposure Control System.
146 pediatric patients were divided in into four age groups (less than 1
year old, 1-5 years old, 5 to 10 years old and 10 to 15 years old). For each
examination, CT acquisition parameters including number of series, use of
contrast medium, tube kV, tube current and rotation time, slice thickness,
the displayed CT dose index (CTDIvol) and the Dose Length Product (DLP)
were reported.
The most common value of CTDIvol and DLP for each type of examination and
each age group was determined. Our results were compared to the pediatric
DRLs of Switzerland (2008), UK (2003) and Germany (2006) and were found
significantly lower. These values are used as our hospital’s Dose Reference
Levels (DRL) until a more extensive -detailed study- survey is organized in
Greece for the establishment of -the- country’s pediatric reference levels.
SHOULD THE JUSTIFICATION OF MEDICAL EXPOSURES TAKE ACCOUNT
OF RADIATION RISKS FROM PREVIOUS EXAMINATIONS?1
Walsh C a, Murphy D b. a St James’s Hospital, Dublin, Ireland;
Children’s Hospital, Dublin, Ireland
b
Our Ladys
With the growing availability of dose histories for patients, the question of
whether previous diagnostic radiation exposures should affect decisions
on future examinations is coming into sharper focus. In the case of higher
dose diagnostic exams such as CT or PET/CT, where patients may receive
several scans as part of their treatment, the question of how cumulative
dose should be treated is of particular interest. In this presentation we
discuss ways in which cumulative dose information may affect our
thinking in justifying exposures1.
Part of the difficulty relates to the complexities of interpreting and
communicating statistically modelled risk. Based on a common tendency
to see a connection between past and future events even where we know
them to be independentdthe gambler’s fallacydwe may find ourselves
treating past risks as if they contribute to the present risk. We take the
example of two patients scheduled for CT scans, one with no previous
diagnostic radiation exposures, whereas the other with a history of previous CT scans, to show that the risks, and justification process, are
equivalent in both cases. For the patient with a history of diagnostic exposures, there are only two possibilities: either harm has been caused or
there has been no effect. If previous CT examinations have not caused
harm, then as past risks, they are irrelevant. The patient is in precisely the
same position with regard to risk as a patient with no dose history. If harm
has been caused, avoiding further diagnostic exposures does not change
this outcome; again in this case, a justified radiation examination should
proceed. We argue that bringing dose history into the decision process for
justifying examinations is contrary to our understanding of stochastic risk
and, rather than improving patient safety, would unnecessarily restrict
access to radiation-based diagnostic examinations.
1 Walsh C, Murphy D, Should the justification of medical exposures take
account of radiation risks from previous examinations? BJR, 2014
EFFICIENCY OF LEAD GLASSES FOR FLUOROSCOPICALLY-GUIDED
PROCEDURES: A SYSTEMATIC MONTE CARLO STUDY OF EYE LENS DOSES
L. Struelens a, C. Koukorava b, c, J. Farah c, d. a Belgian Nuclear Research Centre
(SCKCEN), Mol, Belgium; b Greek Atomic Energy Commission (GAEC), Athens,
Greece; c Department of Medical Physics, University of Athens, Greece;
d
Institut de Radioprotection et de Sûret
e Nucl
eaire (IRSN), Fontenay-auxRoses, France
Background: Previous measurements of eye lens dose performed on
interventionalists have shown that the new recommended annual limit of
20 mSv can be exceeded. This increases the need for systematic and
appropriate use of protective equipment in standard clinical conditions. In
this study, a very comprehensive Monte Carlo study is performed to
evaluate the protection efficiency of different designs of lead glasses,
considering all different working practices during interventional
procedures.
Materials and methods: Two models of lead glasses were considered: one
“wrap-around” type (L1) and one with rectangular front lenses and side
protection (L2), similar to those commercially available. Several modifications to these models were operated with respect to lead thickness,
shape and position on the head. For each design and different working
conditions, the MCNP-X code was used to determine the protection efficiency of the glasses for both eyes.
Results: The L1 type reduces the dose to the left and right eye on average
by 87% and 23% respectively, while the L2 type reduces on average the
dose by 45% (left) and 33% (right). In case of L2 type glasses, a much larger
proportion of the dose to the left eye is coming from the air gaps beneath
the lead glasses. The protection efficiency for the right eye is particular
low for the L1 type glasses. For all tested projections, the right eye is
exposed by photons crossing the gaps beneath the glasses (around 50%)
and the gap between the glasses (16%). When the gap beneath the glasses
is increased by 1 cm for L1, the efficiency of the glasses is reduced by
almost 20%; while for the L2 type an increase by only 0.35 cm increased
the dose by 25%. The simulations showed that there was minimal effect
of the lead thickness.
Discussion: Simulations showed that the glasses shape, the operator’s
position and the beam orientation play an important role in the protection
efficiency of the eye. It is clear from the study that wearing any kind of lead
glasses will not protect the operator in the same way. It is strongly advised
to wear glasses with the minimum possible gaps between the face and the
eyewear.
EYE-LENS EXPOSURE TO MEDICAL STAFF DURING ERCP
A. Zagorska a, b, K. Romanova c, J. Hristova-Popova a, J. Vassileva a. a National
Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria; b Medical
University, Sofia, Bulgaria; c Military Medical Academy, Sofia, Bulgaria
Background: ICRP recommend in its Statement on Tissue Reactions on
2011 an equivalent dose limit for the lens of the eye of 20 mSv in year.
The aim of this study is to report doses to eye lens of medical staff working
in gastroenterology during Endoscopic retrograde cholangiopancreatography (ERCP) procedures.
Materials and methods: Data of ERCP procedures performed in a Department of Gastroenterology during a period of 2 months was recorded. Patient
doses were measured with Dose-Area Product (DAP) meterintegrated in the
C-arm fluoroscopy system.Eye-dose was measured with EDD 30 e Unfors at
the level of the left eye of the main operator, which is closest to the X-Ray
tube side. For each procedure dose equivalent to the eye Hp(0.07), exposure
time, dose rate, DAP and fluoroscopy time were recorded.
Results: The mean dose to the eye-lens per procedure was 26.2 mSv,
minimum measured value was 2.6 mSv and maximum e 111.5 mSv. The
mean estimated annual eye-lens dose is 11 mSv with minimum - 2.29 mSv
and maximum - 45 mSv.The estimated mean annual value does not exceed
the existinglimit but the real doses could be higher presuming that ERCP is
not the single procedure in this department.
Discussion: Taking into consideration the workload of physicians and the
lack of additional shields we recommend that lead glassesto be used to
decrease radiation exposure on the lens of the eye.
CYTOGENETIC TECHNIQUES FOR DOSE EVALUATION AFTER AN ACCIDENT
WHEN ACCURATE, FAST AND RELIABLE RESPONSE IS NEEDED
D. Zafiropoulos a, E. Facco b, L. Sarchiapone a. a Laboratori Nazionali di
Legnaro, IstitutoNazionale di FisicaNucleare,Legnaro, Italy; b Istituto
Oncologico Veneto, Padova,, Italy
Background: The SPES (Selective Production of Exotic Species) project at
the LNL aims to produce radioactive ion beams using a proton beam on a
Abstracts / Physica Medica 30S1 (2014)
uranium carbide target.In case of an accident, where workers are involved,
the dose can reach tens of cGy. In the absence of physical dosimeters or in
the case we need to confirm such exposures, biological methods are
necessary to be adopted.
Biological dosimetry based on the analysis of dicentrics and rings in human peripheral blood lymphocytes after theGiemsa staining of a metaphase is a well-established method. In this work is shown that applying
the fluorescence in situ hybridization (FISH) technique, using telomeric/
centromericpeptide nucleic acid (PNA) probes, in metaphase chromosomes for radiation dosimetrycould become a fast and accurate method for
biological dosimetry in radiation emergency exposures.
Both the methods described above need at least three days to get results, a
time considered too long to support adequately the triage and treatment of
the radiation exposed individuals.
Using premature chromosome condensation (PCC),irradiated human peripheral blood lymphocyteswere fused with mitotic CHO cells and the
yield of dicentrics and rings seen under PCC conditions, using FISH and
PNA probes for centromere and telomere detection, were determined by
image analysis in less than 24 hours.
Materials and methods: Standard Giemsa staining method was used for
the construction of calibration curve. This calibration curve is compared
with that using the same donors and fluorescence in situ hybridization
(FISH) techniqueusing PNA probes. The methodology of cell fusion mediated premature chromosome condensation was used combined with the
FISH analysis using telomere/centromere PNA probes reducing dramatically the time of detecting and scoring of unstable chromosome aberrations for dose evaluation.
Results: Dose response calibration curves with 95% confidence limits used
to estimate uncertainties on dose have been constructed for conventional
metaphase analysis and FISH. Comparison with the dose-response curve
constructed after scoring of dicentrics and rings using PCC combined with
FISH and PNA probes is also presented.
Discussion: The various methods used will be illustrated and the FISH
analysis using PNA probes for centromers and telomersin PCC metaphases
for radiation dosimetry purposes will be presented as a fast, accurate, and
useful method for radiation dosimetry in emergency and incidental situations, a method that can be considered the “gold-standard” of biological
dosimetry.
29
REVISITING AN OLD CHALLENGING ISSUE: DO PATERNAL AND
MATERNAL OCCUPATIONAL EXPOSURES TO IONIZING RADIATION
AFFECT THE GENDER OF THE OFFSPRING?
S.M.J. Mortazavi a, b, S. Aghajari b, S. Taeb c, M. Haghani b, L.
Sannipour c. a The Center for Research on Protection against Ionizing and
Non-ionizing Radiation, School of Paramedical Sciences, Shiraz
University of Medical Sciences, Shiraz, Iran; b Medical Physics
Department, School of Medicine, Shiraz University of Medical Sciences,
Shiraz, Iran; c Vice Chancellery for Health , Shiraz University of Medical
Sciences, Shiraz, Iran
Background: Numerous studies have been performed globally to investigate whether exposure of the parents to occupational and environmental
factors such as ionizing and non-ionizing radiation affect the sex ratio of
the offspring. Currently, there is a limited evidence for a reduced proportion of male offspring due to paternal exposures. On the other hand,
alteration of sex ratio due to maternal exposures is more complicated and
controversial.
Aims: This study aimed at answering the question whether paternal and
maternal occupational exposures to ionizing radiation affect the gender of
the offspring.
Materials and methods: A total of 402 medical radiation workers (202
males and 200 females) comprising diagnostic radiology, radiotherapy and
nuclear medicine technologists were studied. Dosimetric records of the
whole-body doses (measured by film badge dosimetry technique) of these
radiation workers were studied.
Results: Among male radiation workers, 16.9% reported at least one record
of the above the background dose. This proportion in female radiation
workers was 14.1%. The sex ratio among children of male radiation workers
was 1.22, significantly higher than that among children of female radiation
workers which was 1.09.
Conclusion: Male radiation workers fathered a greater proportion of boys
than would be expected for general population. These findings are in
contrast with the reports indicating a reduced proportion of male offspring
due to paternal exposures.
Physica Medica 30S1 (2014)
Contents lists available at ScienceDirect
Physica Medica
journal homepage: http://www.physicamedica.com
e-Posters with presentation
DOSIMETRIC EVALUATION TO MEDICAL WORKERS OPERATING IN A
PET/CT DEPARTMENT AFTER THE USE OF DYNAMIC TECHNIQUES
K. Dalianis, A. Nikaki, R. Efhtymiadou, J. Andreou, V. Prassopoulos. PET/CT
Department Hygeia SA, Athens, Greece
Aim: Positron Emission Tomography is considered to be one of the most
relevant diagnostic imaging techniques having peculiar characteristic to
provide both functional and morphological information for the patient.
Due to the high-energy tracers emitting 511 KeV used in PET/CT departments and considering the risks associated to ionizing radiation that
have been derived from previous studies, special attention is needed when
dealing with radiation protection aspects in a PET/CT modality . Since new
radiopharmaceuticals such us [18F]-fluorothymidine and 18F fluoromethylcholine are used, new imaging dynamic techniques are performed and new measurements concerning the doses to medical staff are
needed.
The aim of this study was to measure the effective wholebody dose of the
personnel in comparison with measurements that have been made in the past.
Method: The estimation of equivalent dose from external dosimetry for all
seven members of the staff was monitored with the use of TLDs badges and
electronic dosimeters worn at the upper pocket of their overall. The
average workload of the department is 6-8 patients per day. In 2013, 983
patients were examined. In our department 18F-FDG, 18F-FCT, 18F-FCH is
available in multi dose vials. Data were collected day-to-day concerning
the interaction of the staff during PET/CT procedures.
Results: We compared the first six months of 2013 a period in which no
FLT or FCH procedures were performed, with the second semester in which
96 FLT and 66 FCH examinations were performed. The average number of
FDG patients was the same for every day, and all patients received 330-390
MBq dose each.
Regarding the whole body doses no changes were observed concerning
medical physicist. The measurements for the nurses show increased
wholebody dose of about 7-12% and that is due to the longer time spent near
the patient. Concerning the technologist doses, an increase of about 15-21%
was measured because they are near to patient at the time of the injection.
Conclusions: Regulations exist to ensure safety of the medical workers
according to ALARA principles. From our results we can observe that
although there is an increase of the doses for technologists and nurses the
numbers are significantly lower than the recommended annual dose limit
by Euratrom 97/43.
MEDICAL PHYSICS TRAINING AND AUDITING IN THE NETHERLANDS
Marion Essers, Marloes Damen, Wim van Damme, Marcel Greuter, Stan
Heukelom, Jochen van Osch, Dyon Scheyen, Christoph Schneider, Esther
van Schrojenstein, Ad Snik, Christiaan van Swol, Pieter Wijn;. on behalf
of the Dutch Medical Physicist Training Foundation
Background and introduction: In the Netherlands, the ‘Dutch Medical
Physicist Training Foundation’ (OKF) organizes the education of medical
physics experts (MPE). Approximately 90 MPE-residents are in training, in
groups of 2-4 per trainer. They are trained in one of the areas of expertise:
radiotherapy, radiology, nuclear medicine, audiology/videology or general
medical physics. In this presentation, the Dutch Curriculum for MPEs will
be discussed, and compared with European guidelines (the EFOMP Policy
Statement 12.1, and the ESTRO/EFOMP Core Curriculum for Medical
Physicists in Radiotherapy) with respect to knowledge, skills and competences (KSC). In addition, the training program, assessment methods,
minimum training institute requirements, and training auditing will be
presented.
Design: OKF is responsible for the Curriculum and the accreditation of institutions, trainers and trainees. Access to the MPE program is restricted to
students with an MSc in physics or an equivalent academic education. The
Curriculum consists of a general part (similar for all areas of expertise) of two
years and a two year specialisation part. A complete revision of the Curriculum during 2011-2014 was based on ESTROs European CC for medical
physicists in radiotherapy, the Dutch medical residency programs, and the
CANMEDs system of competences. Based on this Curriculum, each resident
writes an individualized training program covering the two general years and
two specialisation years (not necessarily in consecutive order), which has to
be approved by the review board of OKF. During their training, the development of the MPE residents with respect to KSC is assessed using progress
reports twice a year and several feedback methods. Quality aspects of individual trainers and requirements and educational settings of the training
institutes are reviewed and accredited every five years by the review board.
Discussion: In the Netherlands the Curriculum for medical physicists in
training has recently been fully revised, and most of the recommendations
on Medical Physics Education and Training in Europe 2014 (EFOMP Policy
Statement 12.1) are implemented.
Still, we would like to discuss our Curriculum and approach in order to
further improve the quality and uniformity of Medical Physics Education
and Training in the Netherlands and Europe.
MAGNETOENCEPHALOGRAPHY AND TASTE
A. Adamopoulos, T. Gemousakakis, P. Anninos, I. Seimenis, A. Kotini. Lab of
Medical Physics, Medical School, Democritus University of Thrace,
Alexandroupolis, Greece
Magnetoencephalography (MEG) recordings were evaluated in five different
states: normal condition, sweet, bitter, sour, and salty taste. We report two
study protocols. The first protocol included 28 healthy volunteers, 14 male and
14 female (12 - 50 years old). Fourier spectral analysis of the MEG showed that,
in the normal condition, as well as in the sweet and bitter taste, the male
volunteers exhibited a higher count of low (2 Hz) than high frequencies (7 Hz)
compared to the female ones; in the case of the sour taste, there was no clear
differentiation between the genders; with the salt taste, the female volunteers
exhibited a higher count of low frequencies (2 Hz) whereas there was no clear
differentiation in the number of high frequencies (7 Hz) between the gender.
The second protocol included 25 healthy female volunteers. They were divided
in two groups according to age: group A (10e19 years old) and group B (20e30
years old). There was a higher count of low (2 Hz) and a lower count of high
frequencies (7 Hz) with increasing age, in all studied states. We compared each
state for the frequencies of 2 Hz and 7 Hz between the two groups. Statistically
significant differences were found in the normal and sweet states for the
frequencies of 2 Hz and 7 Hz and in the salty taste for the frequency of 7 Hz. We
also intra-compared the five states in group A and the five states in group B for
the 2 Hz and 7 Hz frequencies. The results were not statistically significant. A
differentiation in the distribution of frequencies may provide novel insights
into the gender-related taste sensation and the age-dependence of taste
quality brain centers.
2
Abstracts / Physica Medica 30S1 (2014)
THE DOSIMETRY OF NON-IONIZING RADIATION IN THE EDUCATION
PROGRAMME FOR MEDICAL PHYSICS STUDENTS AT THE AGH
UNIVERSITY OF SCIENCE AND TECHNOLOGY (AGH UST)
Zenon Matuszak, Marta Wasilewska-Radwanska. AGH University of Science
and Technology, Faculty of Physics and Applied Computer Science,
Department of Medical Physics and Biophysics, Al. Mickiewicza 30, PL-30059, Krakow, Poland
After introducing the three level (cycle) system of education in Poland (socalled Bologna System), the Medical Physics studies in AGH-UST are
accomplished as a separate branch of education. Medical Physics studies
encompasses 1st cycle (7 semesters) and 2nd cycle (3 semesters) which lead
to awarding bachelor’s and master’s degree, respectively. These circumstances and the progress in using of non-ionizing radiation in medical
diagnostic and therapy, which occurred in last 15 years caused the need for
change in position of the Dosimetry of Non-ionizing Radiation (DNR) in the
general scheme of education of the Medical Physics students. Now, the
DNR course is part of 2nd cycle of education (Master’s degree programme).
The DNR course is obligatory for students of both specialization Dosimetry
and Electronics in Medicine and Imaging and Biometry. The content of the
DNR course is under continuous modification taking into account the
current trends in applications of non-ionizing radiation in medical physics
practice and research.
At present, the basic DNR course encompasses the following didactic units:
lectures (30 h), laboratory (30 h), student’s projects (15 h); the total scoring
5 ECTS points.
Lectures content: static electric and magnetic fields, radiofrequency, microwave and terahertz radiation, optical radiation (infrared and UV-VIS),
acoustic and ultrasonic waves, photoacoustics. The purpose is to give the
students knowledge about the physics of non-ionizing radiation; sources,
methods of measurements, interaction of non-ionizing radiation with
biological matter, some legislation problems and safety regulations are
also discussed.
Laboratory - the laboratory exercises contain following units: electrode
measurements, measurements of environmental electromagnetic fields,
thermal effects of strong microwave fields, UV-VIS optical spectroscopy
(both absorption and reflectance), fluorescence spectroscopy, photosensitizers and chemical actinometry, investigation of magnetostriction ultrasonic generator, measurement of speed of ultrasonic waves in water and
biologically important solutions.
Student’s projects: the topics cover all areas of non-ionizing radiation;
from proposed themes the students choose the topics which are connected
to their area of interest.
EFFECT OF COMBINATION OF ACUTE EXPOSURE TO (50 HZ, 1MT)
ELECTROMAGNETIC FIELDS AND CALCIUM CHANNEL BLOCKERS ON
MICE’S MOTOR COORDINATION
Lama Sakhnini a, Afnan Freije b, Habib A. Nabi Habib c, Mohammed
Naiser c, Mohamed Hameed Alrahim c, Ahmmed Adel Almubarak c, Amer
Kamal c. a Department of Physics, College of Science, University of Bahrain,
PO Box 32038, Kingdom of Bahrain; b Department of Biology, College of
Science, University of Bahrain, PO Box 32038, Kingdom of Bahrain;
c
Physiology Department, College of Medicine, Arabian Gulf University,
Manama, Kingdom of Bahrain
Behavioral studies on animals provide a useful indicator of the possible
cognitive effects on human. Extremely low frequency electromagnetic field
ELF-EMF was found to be directly, enhances the expression of voltagegated Ca2+ channels on plasma membrane of the exposed brain cells,
leading to abnormal accumulation intracellular calcium. This is thought to
affect different neurobehavioral functions in animals, including motor
coordination. Therefore the possibility that calcium channel blockers CCB
might exert neuroprotective effects in exposed animals has been of interest. In this study, the possible effects of ELF-EMFs on the motor performance in adult mice was investigated, using rotarod experiments. The
effect of rotation speed (45,50,55,60 rpm) of the rotating rod was also
tested on a 5-day course. Moreover the role of calcium channel blockers as
neuroprotector against the ELF-EMFs was evaluated. Exposed mice to
(1mT, 50Hz) EMF for 5 days (2 hours/day), showed an enhancement in
their motor coordination abilities but a deficit in their learning abilities.
Another group of ELF-EMF exposed mice were treated with a therapeutic
dose of CCB (amlodipine 3mg/kg/day) for 23 days prior to their exposure
and for 5 days during their exposure. Treatment with CCB improved
learning abilities but did not alter the enhancement of motor coordination,
compared with the performance of the exposed untreated mice. When a
group of mice were exposed to EMF but left to rest for two weeks with no
electromagnetic field exposure, an improvement of learning abilities were
noticed but no improvement of motor coordination. Hence, learning
abilities effects were improved by a therapeutic dose treatment of calcium
channel blockers, and by stopping the ELF-EMFs exposure for two weeks,
which indicates that these deficits are transient and reversible. However
enchantment in motor coordination performance induced by ELF-EMF
exposure were irreversible by CCB treatment or by time.
NEUTRON FLUENCE MEASUREMENTS IN THE TREATMENT ROOM AND
LABYRINTH OF A HIGH ENERGY MEDICAL ACCELERATOR USING
ACTIVATION DETECTORS
P. Georgolopoulou a, T. Vasilopoulou b, I.E. Stamatelatos b. a Department of
Medical Physics, General Anticancer-Oncologic Hospital of Athens‘Saint
Savvas', Greece; b Institute of Nuclear & Radiological Sciences, Technology,
Energy & Safety, National Centre for Scientific Research 'Demokritos' Aghia
Paraskevi, Greece
Neutrons are produced in medical accelerators operating at energies above
the threshold of photonuclear reactions. Treatment room shielding in such
installations is usually adequate to also attenuate neutrons. However,
neutron streaming along the accelerator maze may result in a significant
dose at the bunker door. Monte Carlo and analytical approximation
methods have been used for estimating photo-neutron doses at the maze
entrance and hence optimize the linac shielding design. Nevertheless,
measured and calculated neutron fluence may show significant discrepancies, often attributed to uncertainties in the neutron source term used as
input in the simulations.
In this work, activation detectors were used to determine the neutron
fluence of a 23 MV linac at the “Saint Savvas” Anticancer-Oncologic Athens
Hospital. Bare and cadmium covered gold, indium, manganese and copper
foils were irradiated in mid-air and within polyethylene moderator assemblies. Sets of foils were positioned in-beam, in the treatment room and
along the accelerator maze. The foils were counted using a germanium
based gamma spectrometry system at the NCSR “Demokritos”. Neutron
fluence evaluation was based on the analysis of the 198Au, 64Cu, 56Mn and
116
In peaks at 411 keV, 511 keV, 847 keV and 1294 keV, respectively.
The results of this study provide experimental data for the neutron source
term and the spatial distribution of the neutron fluence in the treatment
room and along the maze of a high energy medical accelerator. These data
will be used for assessing the capability of Monte Carlo and analytical
methods to correctly predict neutron transport in the complex shielding
geometry characterizing the accelerator bunker.
QUANTITATIVE ANALYSIS ON PEDIATRIC RENAL SCANS USING 99M-TCMAG3
V. Letsas a, H. Delis a, D. Apostolopoulos b, T. Skouras c, G.
Panayiotakis a. a Department of Medical Physics, School of Medicine,
University of Patras, 265 00 Patras, Greece; b Department of Nuclear
Medicine, University Hospital of Patras, 265 00 Patras, Greece;
c
Department of Medical Radiation Physics, University Hospital of Patras,
265 00 Patras, Greece
Objective: Radioisotope 99m-Tc-MAG3 is mainly used for the diagnosis of
renal disorders in children. As this group of patients is highly radio-sensitive, the need for non-invasive person-specific dosimetry arises, by
quantification of the images acquired during the dynamic renogram.
Method: The study was realized on a single headed gamma camera. Initial
experimental phantom studies were conducted to quantify self-absorption
of the source organs, containing 99m-Tc-MAG3, and define the attenuation
correction under different conditions.
Results: Counts in designated ROIs were measured and applying proper
correction factors the activity in each source organ was calculated as a
Abstracts / Physica Medica 30S1 (2014)
function of time. Utilizing the MIRD schema and a theoretical model for
the spherical expanding urinary bladder, major organ and effective dose
values were initially derived for ten patients with ages varying from 2,5
months old to 10 years old. The results of the proposed model under/
overestimate the patient dose, compared to the ICRP published values for
MAG3. The detailed quantification during the whole renogram duration,
combined with appropriate assumptions regarding the time after the
study, allow for evaluation of further interesting parameters, such as the
excretion percentage of 99m-Tc per voiding interval.
Conclusion: The proposed model for person-specific dosimetry of MAG3
pediatric examinations in nuclear medicine, can be utilized, with a sufficient degree of accuracy, as a reliable non-invasive, non-time consuming
method for quantitative analysis.
Keywords: MAG3, Renal scan, Radiation dosimetry, Quantitative analysis
DESIGNING AND ESTABLISHING AN INTERNATIONAL DOUBLE DEGREE
MASTER’S PROGRAM IN MEDICAL PHYSICS e THE INTERNATIONAL
MASTER “CLINICAL MEDICAL PHYSICS” (CMP) AT PONTIFICIA
UNIVERSIDAD CATOLICA DE CHILE (PUC) AND HEIDELBERG
UNIVERSITY, GERMANY (UHD)
€ tzel a, O. Ja
€kel a, b, B.
€fer a, S. Barthold-Beß a, J. Debus b, L. Gebauer-Ho
M. Scha
Sanchez c, W. Schlegel a. a Department of Medical Physics in Radiation
Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany;
b
Department of Radiation Oncology, University Hospital Heidelberg,
lica de
Heidelberg, Germany; c Instituto de Física, Pontificia Universidad Cato
Chile, Chile
Purpose: In 2008 both universities initiated a project to establish an international Double Degree Master’s program in Medical Physics e the International Master “Clinical Medical Physics” (CMP) e in order to meet the
special needs of young professionals in the respective field in Latin
America. Funded by the German Academic Exchange Service (DAAD) the
program is part of the “Center of Excellence in Investigation and Teaching”
at Heidelberg University, Germany (UHD) which is supported by the
German Federal Foreign Office. In 2012 the first study group joined the
program and will be awarded with the Master of Science degree (MSc) in
summer 2014.
Material and methods: CMP is designed for graduates in physics or engineering from Latin America. During the first two semesters students
participate in on-site courses at the Pontificia Universidad Catolica de
Chile (PUC), mainly covering the basics of Medical Physics such as e.g.
anatomy, physics of radiation, dosimetry and radiobiology. The third semester concentrates on modern treatment techniques (IMRT and IGRT)
and covers dosimetry methods needed for these new modalities. It is held
online at UHD supplemented by practical sessions at PUC. The fourth
semester is dedicated to writing the final master thesis either at PUC or
UHD. Finally, each successful student exits with a MSc degree from both
universities.
Results: To establish a Double Degree program at two universities from
two continents is a challenge. Program regulations have to be approved by
both universities. Furthermore, the curriculum needs to be coordinated by
both partners over a distance of more than thousand kilometers. Consequently, the whole process requires both time and staff to ensure a
continuous supervision. But ultimately, the program represents a good
combination of on-site and online teaching approaches for students
coming from Latin America as it fits in their individual situation of being
newcomers to both Medical Physics and online learning.
Conclusion: The program requires further modification and adaptation to
the situation in Latin America to best prepare students for their professional careers. However, apart from the continuous personnel and financial support, from the students’ perspective and the students’ feedback
these efforts are worth to continue.
Literature:
Kerres, Michael: Mediendidaktik. Konzeption und Entwicklung mediengestützter Lernangebote. 3. Aufl. München 2012.
Nolda, Sigrid: Einführung in die Theorie der Erwachsenenbildung. 2. Aufl.
Darmstadt 2012.
Reich, Kersten: Konstruktivistische Didaktik. Das Lehr- und Studienbuch
mit Online-Methodenpool. 5. Aufl. Weinheim, Basel 2012.
3
OPTIMIZATION
OF
IMAGE-BASED
DOSIMETRY
IN
Y90
RADIOEMBOLIZATION: A MONTE CARLO APPROACH USING THE GATE
SIMULATION TOOLKIT.
K. Mountris a, A. Autret c, P. Papadimitroulas a, G. Loudos b, D. Visvikis c, G.
Nikiforidis a. a Department of Medical Physics, School of Medicine, University
of Patras, Rion, GR 265 04; b Department of Medical Instruments Technology,
Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo
GR 122 10, Athens, Greece; c LaTIM, UMR 1101 INSERM, CHRU Brest, Brest,
France
Purpose: The ability of Monte Carlo simulation for PET acquisition of
Y90 radioembolization and the correlation of image-based dosimetric
results derived from the simulated data with respective results
derived from the MC simulation of the treatment planning surrogates
Tc99m-MAA (macroaggregated albumin) and Ga68-MAA were
investigated.
Methods: We used the XCAT phantom, using GATE MC platform, since this
combination can provide ground truth data. The tiny branch of Y90 internal
pair production was modeled (32 ppm) for a 30 minutes PET acquisition.
We assumed homogeneous distribution of a 2.5GBq activity in the liver
tissue and the tumor with a TNR 3:1 to compare our results with the
partition model. The Tc99m-MAA SPECT acquisition simulated assuming
homogeneous distribution of 200MBq Tc99m-MAA for 10 min with 64
frames (20s/frame). For pretreatment dosimetry optimization we simulated a Ga68-MAA PET acquisition for the same activity and acquisition
time as in the Tc99m-MAA protocol. Comparison was applied between the
dosimetric results of Y90-surrogates and the Y90 protocol.
We generated 3D dose maps using a kernel-convolution method on the
reconstructed images with an onsite generated Y90 kernel. Furthermore
the total doses of tumor and normal liver parenchyma were calculated for
all the scenarios creating 1D histograms.
Results: For the Y90 scenario the liver dose was 62.94Gy, 15.5% higher
than the dose calculated with the partition model (54.50Gy) and the
tumor dose was 147.28Gy, 9.9% lower than the partition model
(163.50Gy).
For the Ga68 scenario the liver dose was 65.62Gy and the tumor dose
143.44Gy. For the Tc99m scenario the liver and tumor doses were 70.98Gy
and 149.60Gy respectively. In all cases the tumor dose was underestimated
relating to the partition model while the normal liver dose was overestimated. The difference between Ga68 derived doses over Y90 was +4.29%
for the liver dose and -2.64% for the tumor dose while for the Tc99m
acquisition the difference was +12.8% and +1.6% respectively.
Conclusion: The Ga68-MAA showed significantly lower dosimetric differences with Y90 than Tc99m-MAA in liver dose calculation. As liver dose
estimation is a key limiting factor in the treatment planning, the better
correlation of Ga68-MAA can improve the therapeutic results of the
treatment. Further investigation in the usage of Ga68-MAA in radioembolization must be done.
Keywords: Yttrium-90, Radioembolization, Image-based dosimetry,
Tc99m-MAA, Ga68-MAA
A PROTOTYPE WHOLE BODY COUNTER WITH “INVARIANt” RESPONSE
TO BODY HABITIUS AND RADIONUCLIDE DISTRIBUTION
Stratos Valakis, John Kalef-Ezra. Medical Physics Department, University of
Ioannina, Ioannina 451.10, Greece
Background: A prototype shadow-shield moving bed whole body counter
equipped with 16 NaI(Tl) detectors is operated at the University of Ioannina for clinical studies and the detection and measurement of radioactive
contamination in workers, patients and the general public. The counter
design aimed to provide high sensitivity and detection efficiency, eff,
coupled with minimal influence on eff of the body shape, body composition and radionuclide biodistribution.
Methods and materials: A Monte Carlo counter model was developed to
study the influence of a number of parameters on eff of photons 0.1 to 1.8
MeV in energy. The simulation predictions were validated by measurements carried out on a number of phantoms loaded uniformly or nonuniformly with radionuclides of known activity.
4
Abstracts / Physica Medica 30S1 (2014)
Results: Body mass and body height of the 15 modeled homogeneous
phantoms (30 to 113 kg in mass and 138 to 193 cm in height) were the
only body habitus parameters with substantial impact on eff. For
example, the maximum calculated differences in the 662 and 1461 keV
eff values between the simulated homogenous phantoms, +26% and
+19%, respectively, were found between phantoms of the 35 kg / 138 cm
and 91 kg /162 cm. Density changes in the entire body (mainly due to
variations in fat content), or only in the thoracic region had marginal, if
any, impact on the eff values of 140 to 1461 photons. The detection
efficiency of 362 keV photons originating in the thyroid did not differ
from that in the case of uniform source biodistribution. On the other
hand, the eff of 140 to 1461 keV photon emitters located in the upper
trunk or in the pelvic region was lower than that in the case of uniform
source distribution in the entire body by about 10% and 15%,
respectively.
Conclusions: The high measurement precision of the counter coupled
with the small influence of body habitus and source biodistribution on eff
allow for accurate activity measurements.
REVIEW AND REVISION OF THE NATIONAL REGULATORY FRAMEWORK
FOR THE MEDICAL EXPOSURES ON THE OCCASION OF THE
TRANSPOSITION OF THE NEW EC DIRECTIVE 59/2013
V. Kamenopoulou, C. Hourdakis, P. Dimitriou. Greek Atomic Energy
Commission (GAEC), P. Grigoriou & Neapoleos, Ag. Paraskevi, 15310 Athens,
Greece
Greek Atomic Energy Commission (GAEC) is the regulatory body for
radiological and nuclear safety and as such establishes and monitors the
implementation of the respective regulatory framework.
The publication of the new EC BSS Directive is the trigger for the revision
and review of the legal framework governing the radiation protection and
radiological safety of the country.
In this respect, GAEC has initiated the preparation of the pieces of legislation needed. In practice, the current “Radiation Protection Regulations 2001”, (RPR), that transposed the EC Directives 29/96 and 43/97, will be
thoroughly revised and reviewed.
Apart from the EC Directive 2013/59, basis for this revision, and specifically the Medical Exposures part is: (a) the IAEA BSS, (b) the new scientific findings and recommendations, (c) the Policy, Strategy and Goals
of GAEC, (d) the Recommendations given during the IAEA Integrated
Regulatory Review Mission in Greece in 2012, and (e) the operational
experience gained from the implementation of the current regulatory
framework.
Due consideration will be given to issues like (a) the need for clarification
of competence, roles and responsibilities of professionals involved in the
practical aspects of the exposure, (b) the need for clarification of competence, roles and responsibilities of experts involved in the radiation protection aspects (e.g. MPE, RPE), (c) the increase denoted in the exposure of
patients due to technological and scientific developments (justification),
(d) the promotion of Quality Management Systems, (e) the need for quality
assurance programmes, and (f) the need for a different approach to cope
with the “medico-legal” exposures.
The major lesson learned from the operational experience of the RPR
indicated the need to implement the “graded approach” in the legislative
scheme and in the regulatory requirements.
The priorities, concerns as well as the main current legislative initiatives
taken for the Directive’s transposition will be presented and discussed,
focusing in the field of Medical Exposures.
RADIOPHARMACEUTICALS: TRANSPORTATION,
PURCHASE PRICES IN GREECE
DISTRIBUTION AND
A.
Tsamadou,
E.
Kounadi,
P.
Valsamos,
M.
Rekkas,
Sampatakakis. Ministry of Health in Greece, SEYYP, Athens Greece
S.
Background: The transportation, distribution and the purchase prices of
radiopharmaceuticals at the Greek Health System have been investigated
after a complaint that was submitted to our service through the General
Secretary of Transparency and Human Rights. The complaint was that
radiopharmaceuticals prices are much higher in comparison to those at
other EU countries.
Radiopharmaceuticals are radioactive medicinal products (drugs) which,
when ready for use, contain one or more radionuclide (radioactive isotopes) included for a medicinal purpose (Directive 2001/83/EC Article 1).
They are used in nuclear medicine procedures to diagnose or treat various
diseases.
Materials and methods: Data were collected from the Ministry of
Health, the National Drug Organization, the Greek Atomic Energy
Commission, the National Center for Scientific Research “Democritos”,
and the Health Supplier Commission as well as from five import companies or manufacturers of radiopharmaceuticals and specific health
care radiopharmaceutical users (Data from Departments of Nuclear
Medicine, Pharmacies and Departments of Administration from various
hospitals of National Health System). The used tools were structured
questionnaires for the examination of facts, legal framework, work
cooperative practices etc. An extensive data processing and analysis was
followed.
Results: There is confusion about the radiopharmaceutical pricing. According to the law, the Ministry of Health and the National Drug Organization are in charge for the license of circulation and the purchase price of
radiopharmaceuticals. There aren’t official comparative data between
purchase prices in Greece and other EC countries. In Greece there are
different purchase prices for the same radiopharmaceutical regardless the
size of the medical department, the distance of the delivery, the extent of
the order.
Discussion: The cost analysis according the data provided from manufactures and importers suggests that profit margins can be lowered.
Enhancement of the Health Procurment Commission services will help
substantially to the price control. The minimization of cost differences in
radiopharmaceuticals can be achieved by pricing from the government.
SCREENING STUDY OF THE EFFICIENCY OF COMMON SUNGLASSES IN
BLOCKING ULTRAVIOLET RADIATION AND VISIBLE LIGHT BY A NOVEL
SIMPLE METHOD
S.M.J. Mortazavi a, b, M. Hashemi a, M. Haghani a, S. Namavar c, S.
Masoumi b, M. Eghlidospour b, H. Daneshmandi d. a The Center for
Research on Protection against Ionizing and Non-ionizing Radiation, School
of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran;
b
Medical Physics Department, School of Medicine, Shiraz University of
Medical Sciences, Shiraz, Iran; c Ophtalmology Resident, School of Medicine,
Shiraz University of Medical Sciences, Shiraz, Iran; d Department of
Ergonomics, School of Health, Shiraz University of Medical Sciences, Shiraz,
Iran
Background: Overexposure to ultraviolet (UV) radiation has been linked
to eye damages such as cataract, macular degeneration, pingueculae,
pterygia and photokeratitis. Sunglasses can protect the eyes and the delicate skin around the eyes. Ideal sunglasses are expected to block 99-100%
of UVA and UVB radiation. Although it was previously believed that sunglasses should allow the unrestricted transmission of longer wavelengths
of visible light, new findings indicate high energy visible (HEV) light (blue
region of the visible spectrum) can also increase the risk of macular
degeneration.
Aims: This study aimed at introducing a simple method for screening
studies of the efficiency of common sunglasses in blocking ultraviolet radiation and visible light. This study also aimed at answering this question
whether the brand and the price of sunglasses guarantees efficient protection against ultraviolet radiation.
Materials and methods: One hundred twenty pairs of common sunglasses (26 different brands) were tested. In this simple screening study, a
UV meter (Lutron UV-340A, Band pass 290 nm to 390 nm) that is designed
to measure UVA and UVB was used for intensity measurements. Considering this fact that dark sunglasses make the pupil dilate and allow more
light reach the retina, when the sunglasses have poor UV protection, the
eyes can be severely damaged, we also used a Lutron LX-101 lux meter
(range 0-50000 lux) for measuring the decreased luminance by
sunglasses.
Abstracts / Physica Medica 30S1 (2014)
Results: Although all of the 120 sunglasses tested in this study were
effective in reducing the intensity of visible light, nearly none of the
sunglasses could offer efficient protection against UV radiation. The UVA
and UVB transmittance of the sunglasses were in the range of 0.31% (price
category of more than 150$) and 72.2% (price category of 30-90$).
Conclusion: The majority of sunglasses tested in this study strongly
decreased the visible light intensity but couldn’t block all UV radiation.
According to the ANSI Z80.3-2001 (U.S. standard) the lens should have a
UVB (280 to 315 nm) transmittance of no more than 1%. These findings
lead us to this conclusion that these sunglasses can endanger the vision
due to dilation of the pupil and overexposure of the lens to UV radiation.
MEDICAL PHYSICS TRAINING FOR RADIATION ONCOLOGY RESIDENTS
IN GREECE
S.
Nikoletopoulos b,
P.
Georgolopoulou c,
D.
G.
Pissakas a,
Kardamakis a. a Hellenic Society of Radiation Oncology, Greece; b Hellenic
Association of Medical Physicists, Greece; c Medical Physics Department,
G.Anticancer Athens Hospital “Saint Savvas”, Greece
Purpose: Medical physics is an essential part of recommended curricula
for residents in radiation oncology (RO). With no official training programs
in place, medical physics training is often incidental and incomplete for RO
residents in Greece. The aim of this work is to measure the effectiveness of
an educational session on medical physics offered to RO trainees of the
country.
Method: The Hellenic Society of Radiation Oncology (EEAO) hosts quarterly educational meetings for RO residents of all levels. On April 2013 a
physics-dedicated meeting was planned for a body of 52 residents. Topics
ranged from basic radiation physics, physics of radiotherapy, brachytherapy, 3DCRT, IMRT to physics of specialized treatment modalities. Attendance compared favourably to 30 previous EEAO meetings focusing on
clinical issues. Assimilation of material was measured by completion of a
test at the end of the meeting focused on main Learning Objectives (LO).
Results: Test questions covered all sessions of the meeting with equal
weights. Main Bloom’s taxonomy categories were represented. Top 3% of
grades achieved corresponded to residents whose home institutes put a
substantial effort in training. Students responded better to sessions of an
interactive nature with higher grades on respective LO’s but indicated their
enthusiasm over sessions on cutting edge technology. Given the lack of
adequately equipped training institutes in the country, this suggests the
need for rotation of residents, as recommended by international guidelines
on RO training programs (IAEA, ESTRO, ASTRO).
Conclusions: Educational meetings for RO residents focused in medical
physics are quite effective in bringing together the physics background
needed in their clinical practice. The need remains for implementing
official training programs throughout the country and for rotation of residents in different institutes during their training.
PORTUGUESE PATHWAY TO THE IMPLEMENTATION OF THE NEW
EUROPEAN GUIDELINES ON MEDICAL PHYSICS EXPERT
Ana Rita Figueira a, b, Esmeralda Poli a, c, Jorge Isidoro a, d, Maria do Carmo
Lopes a, e. a Professional Matters and Education and Training Technical
Commissions of the Medical Physics Division of the Portuguese Physics
~o Joa
~o, EPE e Porto - Portugal;
Society (DFM-SPF); b Centro Hospitalar Sa
c
Centro Hospitalar Lisboa Norte, EPE e Lisboa - Portugal; d Centro
rio de Coimbra, EPE e Coimbra e Portugal; e Instituto
Hospitalar Universita
Portugu^
es de Oncologia de Coimbra de Francisco Gentil, EPE e Coimbra e
Portugal
Background: The new European Guidelines on Medical Physics Expert
(MPE)[1] define this health professional as a medical physicist who,
through planned advanced clinical training and continuous professional
development, achieves the highest level in education and training (i.e.,
European Qualifications Level 8) in her/his specialty. Given the degree of
responsibility of the MPE and the impact they have on patient safety, it is
urgent that the Membres States take the necessary steps towards
harmonization in Europe.
5
Materials and methods: Given the lack of a proper education and training
framework in Portugal, the portuguese pathway to a full accomplishment of
the European recommendations will be hard and all stakeholders, universities, hospitals, health authorities and scientific and professional organizations, should be involved. Following the establishment of a structured
qualification framework that accomplishes the European Guidelines in
terms of Knowledge, Skills and Competences (KSC), and in order to reach
harmonization and to allow free mobility of the MPE between the Member
States, a process of recognition of the MPE should be put in place.
Results/discussion: The current Portuguese situation and the steps
needed to level up to the new Euratom Basic Safety Standards Directive[2]
and European Guidelines on MPE[1] will be described.
The Medical Physics Division of the Portuguese Physics Society (DFM-DPF),
as the Portuguese national member organization in EFOMP, can and should
have a role in this process and be closely involved in all subjects related to
the medical physics area, including the release of new legislation and the
definition of professional roles and responsibilities of the MPE.
[1] RADIATION PROTECTION No. 174 - EUROPEAN GUIDELINES ON MEDICAL PHYSICS EXPERT, European Commisssion, 2014
[2] Council of the European Union. (2013). Council Directive 2013/59/
Euratom. Official Journal L-13 of 17.01.2014.
ADVERSE HEALTH EFFECTS IN MRI WORKERS
S.M.J. Mortazavi a, b, L. Saanipour a, M. Haghani a, S. Taeb a. a Ionizing and
Non-ionizing Radiation Protection Research Center (INIRPRC), School of
Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran;
b
Medical Physics Department, School of Medicine, Shiraz University of
Medical Sciences, Shiraz, Iran
Background: Magnetic Resonance Imaging (MRI) is a widely used
important diagnostic imaging method. MRI workers are exposed to a static
magnetic field during the whole working hours. As the static magnetic
field of an MRI scanner is always on, MRI personnel moving around the
scanner will be exposed to a time-varying extremely low frequency
magnetic fields which induce electric fields and currents in their bodies.
On the other hand, MRI personnel are occupationally exposed to radiofrequency radiation and the switched gradient fields used for image
encoding only during patients’ examinations.
Aims: The main goal of this study was to investigate the adverse health
effects in MRI workers.
Materials and methods: A questionnaire was designed to collect information from MRI personnel from seven teaching hospitals affiliated to
Shiraz University of Medical Sciences. The collection of data about the
adverse health effects was based on self-reporting by the participants (120
personnel including technologists and nurses).
Results: A statistically significant difference was found between the frequency of individuals who reported headache in MRI workers and the
control group (P¼0.037). On the other hand, a statistically significant difference was found between the frequency of individuals who reported
sleep problems in MRI workers and the control group (P<0.001).
Furthermore, frequencies of myalgia, palpitation, fatigue, concentration
problem, attention problem, nervousness and backpain were significantly
affected in MRI personnel compared to those of the control group.
Conclusion: Altogether our results showed increased frequencies of
adverse health effects in MRI workers. These findings are in line with
several studies reported temporary and dose-correlated vertigo and
nausea in workers and patients exposed to static magnetic fields. Further
studies are needed to explore theses bioeffects as well as their magnitudes
and possible mechanisms.
THE MEDICAL PHYSICS SPECIALIZATION SYSTEM IN POLAND
W. Bulski, P. Kukołowicz. Department of Medical Physics, M. SkłodowskaCurie Memorial Cancer Center and Institute of Oncology, Warsaw, Poland
This paper presents the situation of the profession of medical physicists in
Poland. The official recognition of the profession of medical physicist in
Polish legislation was done in 2002. In recent years, more and more Universities which have Physics Faculties introduce the medical physics
6
Abstracts / Physica Medica 30S1 (2014)
specialty. At present there are about 15 Universities which offer such
programs in medical physics. These Universities can graduate about 150
medical physicists per year. In 2002, the Ministry of Health introduced a
program of postgraduate specialization in medical physics along the same
rules used in specialization of physicians in various branches of medicine.
Seven institutions, mostly large oncology centres, were selected as
teaching institutions, based on their experience, quality of the medical
physics professionals, staffing levels, equipment availability, lecture halls,
etc. The first cycle of specialization programme started in 2005 and the
first candidates completed their training at the end of 2008 and passed
their official state exams in May 2009. As of 2014, there are 112 specialized
medical physicists in Poland. Another 120 medical physicists are undergoing the specialization at 9 accredited institutions.
The system of formation medical physics professionals in Poland is
well established. The principles of postgraduate training and specialization
are well defined and the curriculum of the training is very demanding. The
program of specialization was revised in 2011 and is in accordance with EC
and EFOMP recommendations. However, the system of specialization
should be strengthened and supported financially to meet the requirements established by the Ministry of Health.
EVALUATION OF RADIATION
TOMOGRAPHY PROCEDURES
RISKS
IN
ADULTS
COMPUTED
Abdelmoneim Sulieman a, Esameldeen Babikir b, Alhadi Alarabi c, Khalid
Alzimami b, Kiki Theodorou d. a Radiology and Medical Imaging Department,
College of Applied Medical Sciences, Salman bin Abdulaziz University. P.O.Box
422, Alkharj11943, Kingdom of Saudi Arabia; b Radiological Sciences
Department, College of Applied Sciences, King Saud University, P. O.Box
10219, Riyadh 11433, Saudi Arabia; c Sudan Atomic Energy Commission,
P.O.Box 55, Khartoum, Sudan; d Medical Physics Department, University
Hospital of Larissa, PO Box 1425, Larissa 41110, Greece
Background: The use of CT in medical diagnosis delivers radiation doses to
patients that are higher than those from other radiological procedures. It
has been estimated that CT examinations make up approximately 11% of
the number of radiologic procedures and that radiation from CT delivers
approximately 70% of the medically related radiation dose. The purpose of
this study was to evaluate the patient radiation dose in three different
modalities of CT scanners (64 slices, 16 slices and 2 slices for routine CT
investigations.
Materials and methods: A total of 108 patients were examined in this study
in three different hospitals in Khartoum state. The data was collected from
the following examinations: brain, chest, abdomen and pelvis. Data were
collected to study the effects of patient-related parameters, exposure-related
parameters. The organ dose conversion factor f (organ, z) was obtained from
the NRPB datasets (NRPB-SR279) based on the Monte Carlo simulations.
Results: The mean dose values for CT brain for 16 slices was 670±380
mGy.cm, the average dose value for 2 slices was 331.1±161mGy.cm, while
the average dose for was 1160.8±435.7 mGy.cm. For CT abdomen the
averaged dose value in hospital B was 270.6±100 mGy.cm, the average
dose value in hospital C was 164±56 mGy.cm, while in hospital A the
average dose values was 1444±954 mGy.cm. For CT chest the averaged
dose values in the hospital B was 209.6±83.3mGy.cm, the average dose
values were in hospital C was 238.8±116.2mGy.cm, while the average dose
value in hospital A was 1121.2±872 mGy.cm.
Discussion: Dual slice scanner delivered the least radiation dose while 16
and 64 slice scanners delivered the highest radiation dose. The dose values of
this study were comparable to the international reference levels CT examination. CT dose optimisation protocol is not implemented in all hospitals
MRI DIFFUSION MEASUREMENTS ON PHANTOMS: COMPARISON
BETWEEN EPI AND HASTE SEQUENCES UTILIZING TWO FITTING
METHODS
IN
APPARENT
DIFFUSION
COEFFICIENT
(ADC)
MEASUREMENTS
T. Boursianis a, G. Kalaitzakis a, S. Veneti a, E. Pappas b, J. Damilakis a, T.G.
Maris a. a Department of Medical Physics, University of Crete, Heraklion,
Crete, Greece; b Department of Medical Radiological Technologists,
Technological Educational Institute of Athens, Athens, Greece
Purpose: The aim of this study is to compare Apparent Diffusion Coefficient (ADC) measurements on a specific MRI diffusion phantom utilizing
an EPI and a HASTE sequence and two different fitting algorithms for the
ADC calculation
Materials and methods: Twenty three (23) test tubes with different
Polyacrylamide gel and sucrose solution concentrations, simulating ADC
values of different organs/lesions, embedded inside a plastic water tank
served as a Diffusion Weighting Imaging (DWI) MRI phantom for ADC
measurements. This phantom was repeatedly scanned on a clinical MRI
system (1.5T) for over a six month period with: (a) a 2D multislice single
shot SE Echo Planar Imaging (EPI) DWI sequence and 10 b values (0 to
1000) and (b) a 2D multislice Half fourrier Acquisition Single shot Turbo
Spin Echo (HASTE) DWI sequence and 10 b values (0 to 1000). ADC maps
were constructed using: (a) a Weighted Linear (WL) and (b) a Non Linear
(NL) fitting algorithm. ADC value precision figures (ADC-ROI-CV) and long
term time (LTT-CV) reproducibility figures expressed by coefficients of
variation (CV %) were obtained. Measurements were performed on each
test tube with the two different sequences (EPI and HASTE) for each fitting
model. Total Scan Times (TSC), Geometric Distortions (GD), Ghost Ratios
(GR), Signal to Noise Ratios (SNR) and Contrast to Noise Ratios (CNR)
amongst selected test tubes were estimated using EPI and HASTE sequences for the resultant ADC maps.
Results: ADC values of all sucrose test tubes were in agreement with
nominal values using both sequences and both fitting algorithms. ADC
measurements performed with (NL) fitting algorithms on both EPI and
HASTE sequences showed better precision (mean ADC-ROI-CV < 3 %) and
LTT-CV (2.5%) as compared to the (WL) fitting algorithms. TSCs were
better in the EPI sequences. HASTE sequences showed better GD and GR.
SNR and CNR measurements were comparable when using either EPI or
HASTE sequences. HASTE sequences were capable to quantify higher ADC
values.
Conclusion: Both EPI and HASTE sequences enforced with the NL fitting
algorithms for the ADC calculations proved to be an excellent means for
precise measurement of the ADC.
“IN SILICO” EVALUATION OF SYNCHROTRON RADIATION BREAST
IMAGING
Niki T. Fitousi a, Harry Delis a, George Panayiotakis a. a Department of
Medical Physics, Faculty of Medicine, University of Patras, 26504 Patras,
Greece
Background: X-ray mammography dominates in the field of breast imaging for decades. However, as the demands for more accurate and safe
techniques increase, scientific research has turned to evolved technologies,
such as Synchrotron Radiation. Synchrotron Radiation (SR), being the
brightest artificial X-ray source, has the theoretical advantages that could
highlight it as a novel suitable tool for a new era in breast imaging. Due to
the fact that there is a limited number of SR facilities worldwide, an ”in
silico” approach based on Monte Carlo techniques is considered important
for the evaluation of SR systems for breast imaging. The model, simulating
the complete irradiation procedure, including the attenuation effects
taking place inside the breast, was designed and validated in terms of both
image quality and dose indices. The validated tool was utilized for SR
evaluation experiments.
Materials and methods: A mathematical phantom of increasing glandularity was designed and inserted in the model. In particular, the imaging
task concerned the irradiation of a 5-cm thick step wedge phantom made
of adipose tissue with increasing glandularity in the range of 0-75% and
with a 100-um inhomogeneity of Calcium Oxalate in each step. Due to the
increased thickness of the phantom and the poor performance of low
energies in this demanding task, the energies used were in the range 19-25
keV. The energy on the detector was kept constant, to simulate the
Automatic Exposure Control, and equal to 7 mGy.
Results: The derived images were evaluated in terms of a selected Figure of
Merit containing contrast-to-noise ratio and entrance surface air kerma.
The energies that performed best were 24 and 25 keV, due to the significant difference in entrance surface air kerma comparing to the lower energies. Differences in FOM mostly appear as glandularity increases above
50%.
Abstracts / Physica Medica 30S1 (2014)
Discussion: Even though more studies need to be performed, SR is gaining
ground in the field of diagnostic radiology and particular breast imaging.
The developed Monte Carlo-based SR model can contribute to the complete study of the feasibility of using SR as an additional tool for
mammography with increased accuracy and flexibility.
MONITORING NUCLEAR MEDICINE OPERATION AT NATIONAL LEVEL
S. Vogiatzi, G. Drikos, A. Liossis, M. Lamprinakou, C.J. Hourdakis, V.
Kamenopoulou. Greek Atomic Energy Commission, P.O. Box 60092, 153 10
Agia Paraskevi, Greece
Background: Nuclear Medicine (NM) is one of the fields where, interdisciplinary collaboration is essential for the development of the rapidly
increasing molecular imaging. At the same time, NM is governed by a
multidimensional set of radiation safety requirements, in terms of human and
environmental aspect. Competent Authorities (CAs) for radiological safety
have a significant role in monitoring the delivery of NM diagnostic procedures
and treatments. The Greek Atomic Energy Commission (GAEC), regulatory
body and CA for radiological and nuclear safety in Greece, implements a
standard operating procedure (SOP) for monitoring NM departments’
smooth operation and compliance with radiation safety provisions.
Materials and methods: Data such as NM annual frequencies, calendar data
and administered activities (AAs) for delivered therapeutic treatments and
records for delay tank systems’ management are reported to GAEC by the
end-users, annually. AAs data for diagnostic NM procedures are collected
during onsite inspections performed by GAEC. Additionally, radiopharmaceuticals transport data are reported by the carriers, to the national database
maintained by GAEC, prior to each shipment, in terms of approval. The
approval criteria are set as activity limits and operation license expiry date.
The afore-mentioned sets of data, concern the totality (100%) of the NM
departments and radiopharmaceutical shipments in the country.
Results: The combined evaluation of therapeutic AAs, patients’ residence
times in therapy wards and patient excreta storage time in delay tanks
provides a useful tool for monitoring hospital waste, confirming at the
same time that radiation safety requirements are met. Radiopharmaceuticals supply data reported by the carriers in correlation with annual frequencies and calendar data, offer a national overview for the evaluation
and among others, the potential improvement in the efficient use of
existing infrastructure.
Public exposure can also be monitored by reviewing the implementation
of patient release criteria.
Discussion: GAEC’s SOP for monitoring NM operation in the country has
been applied for several years and has proven useful for ensuring
compliance with public, occupational and environmental radiation safety
requirements.
TRACKING OF MR COMPATIBLE INTERVENTIONAL ROBOTS BY
CONTROLLING THE MRI VISIBILITY OF OPTICALLY DETUNABLE MR
MARKERS
Andrew
Webb b,
Ioannis
Seimenis c,
Eftychios
Junmo
An a,
Christoforou d, Nikolaos V. Tsekos a. a Medical Robotics Laboratory,
University of Houston, Houston, TX, USA; b C.J. Gorter Center for High Field
MRI, Leiden University Medical Center, Leiden, Netherlands; c Medical
Physics Lab, Medical School, Democritus University of Thrace,
Alexandroupolis, Greece; d Department of Electrical and Computer
Engineering, University of Cyprus, Cyprus
Background: Inductively coupled RF coils comprise a type of MRI-visible
markers for tracking devices and tools in MRI guided interventions.
We present a technique that utilizes the control of an MR compatible
interventional robot to select in real-time which markers need to
be visible to track the motion of the robot. With a lower number of
markers active, a fewer MRI acquisitions are needed, thus speeding up
tracking.
Methods: Figure 1 shows the arrangement of the optically detunable MR
markers onto the joints of a custom-built MR compatible manipulator.
Based on which degrees-of-freedom (DoF) are actuated, the robot control
code selects which subset of markers needs to be visible to track this
7
motion. This subset is sent to the marker’s microcontroller that loops
through the list of markers turning ON only one marker of the selected
subset. The microcontroller triggers the MRI scanner to collect data and
receives a TTL after imaging to proceed with the next selected marker. The
solenoid coils are 3-mm in diameter??? with a photoresistor in their
tuning circuit and optical fiber connecting them to a LED activated by a
microcontroller linked to the robot.
Results: Figure 2 shows results of controlling the MRI visibility of the
markers from the robot control imaged at 1.5T with a GRE sequence (TE/
TR/angle¼1.75ms/227.72ms/1, matrix size¼192x140, FOV¼192x140mm,
slice ¼ 8mm). Figures 2(a) and 2(b) were collected when all markers were
detuned or tuned, respectively. Figures 2(c) to 2(f) were collected when the
operator requested a motion of all DoF. The robot control module sent to
the micro-controller the coils (J¼1) ¼ {1111} (i.e. all coils). This resulted in
the sequential collection of images, witheach image having only one of the
four coils ON.
Discussion: Selecting which markers are visible based on the motion of
the robot allows speeding up of MRI tracking (since only certain markers
need to be visible). Also, by tuning only one marker per acquisition repetition, the location of this particular point of the robot is unambiguously
identified, simplifying data acquisition and processing.
DEVELOPMENT OF INDIGENOUS COST EFFECTIVE PEDIATRIC HEAD
AND BODY COMPUTED TOMOGRAPHY DOSE INDEX (CTDI) PHANTOM
FOR PEDIATRIC CT DOSE MEASUREMENT
A. Saravanakumar, K. Vaideki, K.N. Govindarajan, S. Jayakumar.
Department of Applied Science, PSG College of Technology, Coimbatore 641
004, India
Computed Tomography scanner plays a prominent role in diagnosing
diseases, injuries and other abnormalities in pediatric patients. For an individual child, the risks of CT are small and the benefit always outweighs
the risks when used appropriately. CT system manufacturers have recently
implemented a dose display Weighted CT Dose Index on their system’s
operating consoles in accordance with IEC Standard 60601-2-44. This dose
display feature provides a reference dose to CTDI head and body phantoms
for any selected head or body scan protocol. However, the displayed CTDIw
reference dose always underestimates the actual dose delivered to infants
and young children up to about the age of one year. In order to quantify this
underestimation. In the current study we developed indigenous pediatric
CTDI head, body phantom to suit our average Indian infant size at
comparably a low cost. The dimension of the head and body phantom were
10 cm and 16 cm respectively. This simulates the X-ray attenuation of an
infant head or body. CT Dose measurements on this phantom were carried
out using a calibrated 150mm CT dose profiler with dose profile analyzer
software, from RTI Electronics, Sweden. The profiler was calibrated to read
the dose in phantom directly. Dose received in the head, body phantom at
the centre and periphery was measured by five point method. Using these
values weighed computed tomography dose index 29.78 mGy, 15.32 mGy,
and 15.32 mGy, for head, chest, and abdomen respectively were calculated.
The results of the study have been compared with the estimated console
value and are well within the acceptable level approved by Atomic Energy
Regulatory Board, India.
A SIMPLE AND EFFICIENT STEREOLOGICAL APPROACH FOR ESTIMATING
SPLENIC VOLUME ON MDCT IMAGES
Michalis Mazonakis a, John Stratakis a, John Damilakis a. a Department of
Medical Physics, Faculty of Medicine, University of Crete, 71003 Heraklion,
Crete, Greece
Purpose: The determination of splenic size is of value in the clinical
management of several hematopoietic diseases and immunological disorders. The aim of this study was to introduce a new stereological
approach for estimating splenic volume on multidetector computed tomography (MDCT) images.
Methods: Abdominal MDCT was performed in nineteen consecutive patients with no history of splenic diseases. The volume of the spleen was
estimated using the stereological method that involved overlying each
8
Abstracts / Physica Medica 30S1 (2014)
image with a regular grid of test points. The orientation of the computergenerated grid was always random. The user selected all points falling
within the spleen and the software automatically provided the organ
volume. The splenic volume was estimated through the systematic image
sampling procedure. Stereological assessments were obtained by using
sampling intensities of 1/2 and 1/3 that provided samples with every
second and third image depicting the spleen, respectively. The repeatability of stereology was evaluated. Stereological estimations were
compared with those derived by the reference method of planimetry
based on the manual delineation of splenic borders on each image.
Results: The use of a sampling intensity of 1/3 led to splenic volume assessments with an unacceptable mean coefficient of error (CE) of 10.7±2.2
%. Precise volumetric estimations with a low mean CE of 5.0±0.9 % were
obtained by using samples of 4-7 MDCT images generated from the 1/2
systematic sampling scheme. This stereological approach provided splenic
volume in less than 3 minutes and presented a quite good repeatability
with a coefficient of variability of 3.2 %. The 95% limits of agreement between the reference method of planimetry and stereology as applied in
samples with every second image were clinically acceptable and equal to
12.4 cm3 and -20.5 cm3. No statistically significant difference was found
between the two volumetric methods (P>0.05).
Conclusions: The application of the proposed stereological approach in
samples of abdominal MDCT images arising from the 1/2 systematic sampling scheme may result in quick, accurate and reproducible splenic volume
estimations with a known precision.
DIFFUSION TENSOR IMAGING IN BRAIN TUMORS: A STUDY ON GLIOMAS
AND METASTASES
T.S. Papageorgiou a, D. Chourmouzi b, A. Drevelegas b, K. Kouskouras c, A.
Siountas a. a Department of Medical Physics, School of Medicine, Aristotle
University of Thessaloniki, 54124, GREECE,; b D.Chourmouzi, Department of
Radiology, Interbalkan Medical Center, GREECE 57001 Thessaloniki, Greece;
c
Department of Radiology, Aristotle University Medical School, AHEPA
University Hospital, Thessaloniki, 54124, GREECE
Purpose: To explore the role of Diffusion Tensor Imaging in preoperative
glioma grading, as well as in differentiation between gliomas and metastatic brain tumors. Diffusion tensor variables of enhancing and edema
regions were compared between the different subject groups.
Materials and methods: We performed DTI in 42 patients (9 Low Grade
Gliomas, 24 High Grade Gliomas, 9 Single Metastatic brain tumors). We
measured FA, l1, l2, l3, ADC, Cl, Cp, Cs, RA, and VR in enhancing portions
of tumors and edematous regions. Ratios of enhancement to edema values
were created for each variable.
Results: In peritumoral edema, FA, Cl, RA and VR were proven to be
significantly different between the three groups, in addition to several
variables in enhancement regions. numerous other variables were successful in pair-wise comparisons.
Conclusion: Diffusion tensor indices could be used for the differentiation
between low and high grade gliomas, as well as for the distinction between
gliomas and metastases.
QUALITY CONTROL FOR DIGITAL RADIOGRAPHY AND FLUROSCOPY
EQUIPMENT IN A LARGE UNIVERSITY HOSPITAL IN OMAN:
IMPLEMENTATION OF EUROPEAN ACCEPTABILITY CRITERIA
I.I. Suliman a,*, Hilal AL-Zeheimi a, Amaal Al Rasbi a, Amna Al Jabri a, Naema
Al-Miamani a, Ibtesaam Al-Maskary a, Haddia Bererhi b, Per Rude b, Ahmed
Al Shuhaimi b, Humoud Al Dhuhli b, Faisal Al Azri b. a Department of
Radiology and Molecular Imaging, Medical Physics Section, College of Medicine
& Health Sciences, Sultan Qaboos University; P.O 35; Post code 123; Al-Khod,
Sultanate of Oman; b Department of Radiology and Molecular Imaging, Sultan
Qaboos University Hospital ; P.O 38; Post code 123; Al-Khod, Sultanate of Oman
This paper reports the results of acceptanceand routine quality Control
(QC) measurements performed on 12digital radiography and Fluoroscopy
equipmentat Sultan Qaboos University Hospital, Oman. QC is a part of
quality assurance (QA) program and included acceptance and annual
routine QC tests.
Main X-ray generator /tube parameters remain the same as previously
used in screen-film radiography. For DR , CR and fluoroscopy, image
quality was assessed using TOR [CDR] and TOR [18FG], TOR [18FG]+M1+
N3 Leeds test tools, respectively. Threshold contrast-detail detectability
(TCDD) wasassessed using Leeds TO.20, TO. 16 and TO. 10; respectively.
Automatic exposure control (AEC) was assessed by measuring the exit
dose of varying copper thicknesses. In fluoroscopy, emphasis was placed
on testing performance parameters (HVL, kV and Dose) under AEC control. Measurements results are compared with European acceptability
criteria [1].
HVL in radiography was 2.5-3.0 mm Al ranged, limiting resolution was
(2.4-3.6) lp/mm ranged, and contrast resolution was better than 4%.AEC
was found to fairly control the patient exit dose but its effect on detector
dose index (DDI) was not consistent. Fluoroscopy parameters tested under
AEC were within the acceptable limit. Comparative evaluation of equipment performance isdone based on dose, image quality and the TCDD.
Fault results were mainly due to errors inkV indication and/or beam
alignment emphasising the importance of more frequent QC. New technologies continuously present a superiorimage quality, which might suggest a need for revised acceptability criteria.
References
[1]. Zoetelief J., van Sold R.T.M., Suliman I.I., et al. Quality control of
equipment used in digital and interventional radiology. Rad. Prot. Dosim.
117(1-3): 277-82 (2005).
[2]. EC (2012). Criteria for acceptability of Medical Radiological equipment.
European Commission Radiation Protection Report No. 162.
MODERN 256-SLICE CT PULMONARY ANGIOGRAPHY OR LUNG
PERFUSION SCINTIGRAPHY IN PREGNANT PATIENTS SUSPECTED FOR
PULMONARY EMBOLISM? A COMPARISON OF ASSOCIATED RADIATION
RISKS
K. Perisinakis a, I. Seimenis b, A. Tzedakis c, J. Damilakis a. a University of
Crete, Medical School, Medical Physics Department; b University of Thrace,
Faculty of Medicine, Medical Physics Department; c University Hospital of
Heraklion, Medical Physics Department
Aim: To a) determine normalized data for maternal radiosensitive organs
and embryo/fetus absorbed radiation doses from 256-slice CT pulmonary
angiography (CTPA) performed in pregnant patients suspected for pulmonary embolism and b) provide and compare reliable maternal and fetal
dose data and associated radiation cancer risk estimates from 256-slice
CTPA and lung perfusion scintigraphy (LPS).
Methods: Mathematical anthropomorphic phantoms were generated to
simulate the average female at early pregnancy and at 3rd, 6th and 9th
month of gestation. In each phantom 0-3 additional 1.5 cm-thick fat tissue
layers were added to derive 4 phantoms representing pregnant females
with different body-sizes. Monte Carlo methods were used to simulate
low-dose 256-slice CTPA exposures on each of the 16 generated phantoms.
Normalized organ and embryo/fetus dose data were derived for exposures
at 80, 100 and 120kV. Maternal effective dose and embryo/fetus dose from
256-slice CTPA and associated life attributable risks of radiation cancer
were determined for different body sizes and gestational stages, and
compared to corresponding data from lung perfusion scintigraphy.
Results: For an average-size pregnant patient, the 256-slice CTPA exposure
was found to result in a maternal effective dose of 1 mSv and an embryo/
fetus dose of <0.05 mGy. However, maternal effective dose was found to
considerably increase with body size, while embryo/fetus dose was
increased with both body size and gestational stage. Compared to LPS, lowdose CTPA to an average-sized pregnant patient was found to result in 15%
higher maternal effective dose, but 3.4-6 times lower embryo/fetus dose.
Nevertheless, LPS was found to be associated with less aggregated radiation risk for an average size pregnant patient with the difference from
CTPA to be further increased for larger patients.
Conclusion: Compared to CTPA performed with a modern wide-area CT
scanner, LPS remains comparatively more dose efficient and should be
definitely maintained as the preferable next step of imaging for pregnant
patients suspected for pulmonary embolism who have a normal chest Xray radiograph and require further investigation.
Abstracts / Physica Medica 30S1 (2014)
THE ACDS PILOT: SUMMARY OF OUTCOMES FROM A BESPOKE
NATIONAL AUDITING SERVICE
Williams Ivan a, f, Lye Jessica a, f, Lehmann Joerg b, f, Kenny John a, c, f, Dunn
Leon a, f, Alves Andrew a, f, Cole Andrew a, f, Johnston Peter d, f, Kron
Tomas e, f. a Australian Clinical Dosimetry Service, 619 Lower Plenty Rd,
Yallambie, Australia, 3085. [Presenter]; b Institute of Medical Physics, School
of Physics, University of Sydney, Australia, 2006; c Radiation Oncology
Queensland, Toowoomba, Australia, 4350; d Olivia Newton-John Cancer and
Wellness Centre, Heidelburg, Australia, 3084; e Australian Radiation and
Nuclear Safety Agency, 619 Lower Plenty Rd, Yallambie, Australia, 3085;
f
Peter MacCallum Cancer Centre, East Melbourne, Australia, 8006
Background: The Australian pilot of a national dosimetry audit program
has completed the originally contracted three years of operation. The
Australian Clinical Dosimetry Service, (ACDS) was a pilot program to
enable the Australian Government to determine whether the bespoke
design was suitable for an on-going Australian service. The outcomes from
the three years of operations will be presented and discussed with an
analysis of whether the pilot requirements were met and why.
Materials and methods: Designed over 2010/11 by experts drawn from
the three professions in consultation with the national Department of
Health, a list of outcomes required over a three year time frame was
formulated. These outcomes were central to a Memorandum of Understanding, (MoU) between Health and the Australian Radiation Protection
and Nuclear Safety Agency (ARPANSA) which hosted the ACDS. The MoU
defined the operational and reporting requirements for the ACDS and the
need for external advisors drawn from the hospitals: the Clinical Advisory
Group, (CAG).
Results: The ACDS has achieved all the MoU requirements. The staff within
the ACDS engaged with the professional clinical workforce and provided a
successful and functioning audit service. External review of the ACDS
during its third year of operation identified strengths and weaknesses
within the MoU and the ACDS structure and how the ACDS resolved a
number of conflicting issues. The report identified the successes within the
ACDS and how these were achieved.
Analysis of the ACDS design and operation will provide assistance and
advise those seeking to design or modify national or regional auditing
programs. Finally the paper reviews the potential future for the ACDS.
Discussion: The raw number of audits and outcomes indicate that the
ACDS has met the MoU auditing requirements. The reasons for the ACDS’
success are highly dependent on: attracting quality staff who can respond
with agility to changing situations, a high level of communication with the
professional community, and a high level of engagement by the
community.
The Australian Clinical Dosimetry Service is a joint initiative between the
Department of Health and Ageing and the Australian Radiation Protection
and Nuclear Safety Agency.
THE EFFECT OF PATIENT BODY HABITUS AND MODULATION STRENGTH
ON RADIATION DOSE AND IMAGE QUALITY IN CT EXAMINATIONS
USING AUTOMATIC TUBE CURRENT MODULATION
Antonios E. Papadakis a, Kostas Perisinakis b, John Damilakis b. a University
Hospital of Heraklion, Medical Physics Department, Heraklion, Crete, Greece;
b
University of Crete, Medical School, Medical Physics Department, Heraklion,
Crete, Greece
Background: The aim of this study was to investigate the effect of patient
body habitus and modulation strength on radiation dose and image
quality in CT examinations using automatic tube current modulation
(ATCM).
Materials and methods: Ten physical anthropomorphic phantoms that
simulate the average individual as neonate, 1-, 5-, and 10-year-old and
adult were employed. The 10-year-old and adult anthropomorphic phantoms were appropriately devised using custom made bolus material to
simulate overweight and obese patients. Head, neck, thorax, and
abdomen/pelvis helical acquisitions were performed in all phantoms using
the standard pediatric and adult examination protocols specified for each
9
anatomical region. Acquisitions were performed using a sixteen-slice CT
scanner, which was equipped with an angular and z-axis ATCM system. CT
acquisitions were performed at fixed tube current and with the ATCM
system activated at three different modulation strength settings i.e. weak,
average, and strong. Image noise was measured as the average standard
deviation of the Hounsfield unit across regions of interest, which were
drawn over uniform tissue equivalent areas.
Results: The modulated mAs recorded for neonate compared to 10-yearold increased by 30%, 14%, 6%, and 53% for head, neck, thorax and
abdomen/pelvis, respectively, (P<0.05). Fixed tube current and ATCMactivated acquisitions provided images of similar noise at a significant
reduction of the modulated mAs with the exception of the 10-year-old
phantom. In pediatric and adult phantoms, the modulated mAs ranged
from 44 and 53 for weak to 117 and 93 for strong modulation strength,
respectively. At the same exposure parameters image noise increased with
body size (P<0.05).
Discussion: The ATCM system investigated herein can effectively reduce
patient radiation dose in adult individuals regardless their body habitus.
However, ATCM may increase patient radiation dose in trunk CT examinations of children older than 5-year-old. Care should be taken when
implementing ATCM protocols to ensure that image quality is maintained.
AUTOMATIC QUANTIFICATION OF CONTRAST ENHANCED ULTRASOUND
LIVER IMAGING
Elias Gatos a, Stavros Tsantis a,b, Aikaterini Skouroliakou c, Ioannis
Theotokas d, Pavlos S. Zoumpoulis d, George C. Kagadis a. a Department of
Medical Physics, School of Medicine, University of Patras, GR 26504, Rion;
b
Department of Biomedical Engineering, Technological Educational Institute
of Athens, GR 12210, Egaleo; c Department of Energy Technology
Engineering, Technological Educational Institute of Athens, GR 12210,
Egaleo; d Diagnostic Echotomography SA, 317C Kifissias Ave., GR 14561,
Kifissia
Background: Ultrasound contrast agent imaging (CEUS) has overcome the
major limitation of classic Liver B-Mode and Doppler Ultrasound, and
provided the ability to depict the parenchyma microvasculature. The
enhancement pattern of Focal Liver lesions (FLLs) can be studied and
evaluated in real time throughout all vascular phases (arterial, portal
venous, late and postvascular phases). FLL characterization is currently
performed either by means of visual inspection or by built-in software
packages that provide low quality time-intensity curves without quantitative assessment. A new automatic method is proposed that initially detects an FLL and then provides time-intensity curves towards its
characterization.
Materials and methods: Twelve (12) CEUS image series of 12 patients
with FLLs disease have been subjected for quantification into the proposed
algorithm. A specifically designed detection algorithm was implemented
to detect the FLL across frames and extract its contour. This particular
lesion region represents the region of interest on CEUS images, from which
the enhancement pattern and its type can be derived. The algorithm is
based on unsupervised segmentation, utilizing the Markov Random Field
model (MRF) and Continuous Wavelet Transform (CWT) employing the
‘Mexican Hat’ wavelet filter. The proposed algorithm employs textural and
multi-scale wavelet coefficient information provided by CWT analysis.
Wavelet analysis produces the initial clusters into the MRF procedure to
minimize the number of iteration steps and to enhance the clustering
speed.
Results: Compared with manual segmentation by an expert physician, the
lesion detected had an average overlap value of 0.92±0.02 for all CEUS
videos included in the study. Following the lesion detection procedure
time-intensity curves are computed and plotted from lesion and reference
areas (Figure). In addition, several parameters are computed such as Area
Under the Curve, Mean Transit Time, Perfusion Index, Rise Time and Time
to Peak to strengthen the evaluation procedure.
Discussion: A new promising tool has been implemented towards FLL
detection and time Intensity curves analysis in CEUS data. After lesion
detection, the degree and phase of lesion enhancement relative to the
parenchyma is computed and visualized to evaluate the lesion character.
10
Abstracts / Physica Medica 30S1 (2014)
Its main characteristics are robustness, fast and automatic execution that
could be easily adapted to a user friendly interface.
Figure:(a) User Initialization of Lesion and Parenchyma area. (b)Lesion detection at
t¼5 sec(c) Lesion detection at t¼8 sec, (d) Lesion detection at t¼12 sec, (e) Lesion
detection at t¼15 sec, (f) Time curve ananysis for lesion characterization.
IAEA ACTIVITIES IN IMAGING MEDICAL PHYSICS
H. Delis, G.L. Poli, A. Meghzifene. Dosimetry and Medical Radiation Physics
Section, Division of Human Health, Department of Nuclear Sciences and
Applications, International Atomic Energy Agency
The International Atomic Energy Agency (IAEA) has been working on
strengthening the medical physics capacity throughout the world since the
early sixties. Taking into account the acute need for medical physics support in radiotherapy in the past, the IAEA has focussed its support to that
field.
In diagnostic imaging, the role of the medical physicist has been long
limited to quality control and radiation safety. This has changed
significantly in the past year, especially in some well-developed
health care systems, and the clinically qualified medical physicist
(CQMP) is a member of the multidisciplinary health care team
working towards the best outcome of the patient diagnosis or
treatment.
The definition of the medical physicist working in a clinical environment is
clearly stated in the International Basic Safety Standards [1], and the roles
and responsibilities of the CQMP are explicitly described [2]. However,
worldwide harmonization is far from being achieved and the IAEA has
been working towards this direction. Additional guidelines aim to further
promote this harmonization in the education and training requirements of
the CQMP [3-6].
The IAEA represents one of the main resources for the medical
physicists, and often, especially in developing countries the only one.
For this reason, additional work is done in producing guidelines to
support the CQMP in the clinical environment. Specifically for Nuclear
Medicine and Diagnostic Radiology, several publications have been
produced to support the CQMP with quality assurance and dosimetry
tasks [7].
Furthermore, more targeted training activities are implemented under the
support of the Department of Technical Cooperation, in the form of fellowships and national or regional training courses. These activities aim to
train medical physicists not only to work in a clinical environment, but also
to act as future trainers. This train-the-trainers mechanism has been
recently enriched with the doctoral coordinated research project (CRP) [8]
on “Advances in medical imaging techniques”. In the framework of this
CRP, medical physicists are involved in advanced research at the PhD level,
gaining the knowledge and competence to support advanced imaging
modalities at their institution, or other institutions at a national or regional
level.
References
[1] INTERNATIONAL ATOMIC ENERGY AGENCY, Radiation Protection and
Safety of Radiation Sources: International Basic Safety Standards d Interim
Edition, IAEA Safety Standards Series No. GSR Part 3 (Interim), IAEA,
Vienna (2011).
[2] INTERNATIONAL ATOMIC ENERGY AGENCY, Roles and Responsibilities, and Education and Training Requirements for Clinically Qualified
Medical Physicists, Human Health Series No. 25, IAEA, Vienna (2013).
[3] INTERNATIONAL ATOMIC ENERGY AGENCY, Clinical Training of Medical
Physicists Specializing in Radiation Oncology, Training Course Series No.
37, IAEA, Vienna (2010).
[4] INTERNATIONAL ATOMIC ENERGY AGENCY, Clinical Training of Medical
Physicists Specializing in Diagnostic Radiology, Training Course Series No.
47, IAEA, Vienna (2011).
[5] INTERNATIONAL ATOMIC ENERGY AGENCY, Clinical Training of Medical
Physicists Specializing in Nuclear Medicine, Training Course Series No. 50,
IAEA, Vienna (2011).
[6] INTERNATIONAL ATOMIC ENERGY AGENCY, Postgraduate Medical
Physics Academic Programmes, Training Course Series No. 56, IAEA,
Vienna (2014).
[7] INTERNATIONAL ATOMIC ENERGY AGENCY, Human Health Campus,
Medical Radiation Physics, http://nucleus.iaea.org/HHW/MedicalPhysics/
index.html
[8] INTERNATIONAL ATOMIC ENERGY AGENCY, Coordinated Research Activities, http://cra.iaea.org/cra/index.html
PRACTICAL WAY FOR AWARENESS OF PATIENT DOSE
CONVERSION OF CTDI-DLP TO EFFECTIVE DOSE ESTIMATION
IN
CT:
Gokce Kaan Atac a, Tolga Oncu b, Tolga Inal c, Aydın Parmaksiz b, Figen
Bulgurcu b, Emine Bulur b. a Ufuk University, Medical School, Dept. of
€y
Radiology, Konya Road No:86-88 Balgat, 06570, Ankara, Turkey; b Sarayko
Nuclear Research and Training Center, 27 Atom Street, 06983 Kazan, Ankara,
Turkey; c Ankara University, Physics Engineering Department, Ankara, Turkey
Background: Computed Tomography has the biggest part of contribution to
radiation from medical sources. By developing a practical tool; to estimate
patient effective doses (ED) in Computed Tomography (CT) examinations
through a new developed software which uses age and sex specific dose
conversion coefficients and CT specific dose data, to enable medical exposure
more understandable by comparing with the regional background radiation.
Materials and methods: Effective dose calculation software for CT examinations was developed based on Excel structure. EDs of 100 patients underwent
chest and abdomen-pelvis CT examinations were retrospectively calculated by
using software and ImPACT CT Scan software to evaluate the performance.
Results: Mean ED for chest and abdominal examinations was calculated as
5,7 mSv and 13,8 mSv for female patients and 5,8 mSv and 16,4 mSv for
male patients respectively with new method. The results of dose calculations performed with the developed software were found to be quite close
to the results of ImPACT CT scan software for abdomen and chest examinations of female patients but male patients. The ratio between average
effective dose and local background radiation were between 1 to 22 for
chest and 3 to 63 for abdominal examinations.
Discussion: The new software helped to calculate the EDs with some deviations comparing to the standard method. Comparison to the local background radiation show very large range of ratios between different cities. A
practical tool for calculating EDs for CT examinations was developed which
helps especially physicians to calculate EDs simply. It is observed that even for
similar exposure protocols, EDs may show difference between anatomical
regions.
IMPACT OF BREAST TOMOSYNTHESIS AND FULL FIELD DIGITAL
MAMMOGRAPHY ON HOSPITAL PERSONNEL, MAMMOGRAPHY
WORKFLOW, AND IMAGING INFRASTRUCTURE
A. Gkolfinopoulou, A. Gkremos, Ch. Preppa, M. Kallergi. Department of
Biomedical Engineering, Technological Educational Institute of Athens, Greece
Background: Digital breast tomosynthesis (DBT) and full field digital
mammography (FFDM) are the state-of-the-art in breast imaging. The
purpose of this study was to evaluate the impact of DBT and FFDM on
personnel, workflow, and data management infrastructure.
Materials & methods: A breast imaging center of a major hospital was
reviewed for 6 months. The center operated a DBT and FFDM system
(Selenia Dimensions, Hologic Inc., USA). Representative FFDM and DBT
images of patients were recorded and analyzed. Personnel were
Abstracts / Physica Medica 30S1 (2014)
interviewed and workflow monitored. Existing digital data management
infrastructure was reviewed and assessed relative to the needs of DBT and
FFDM. Data analysis included descriptive statistics and qualitative evaluation of (a) image display, (b) image transfer, (c) image storage, (d)
personnel training, (e) mammography workflow including radiologists’
reading times, and (f) PACS system. All image analysis was done with the
Fiji processing package.
Results: A standard DBT examination of a 5 cm compressed breast generates 80 images and, on average, 136 MB of data. In contrast, a screening
4-view FFDM examination yields only 22 MB. Image display requires
dedicated workstations and user interfaces to facilitate the radiologists’
workflow that is burdened by a 20-fold increase in the number of images
due to DBT with significantly slower reading times (2-3 times slower than
FFDM). The DBT data can be handled best (stored and transferred in both
Secondary Capture Tomo Object (SCTO) and DICOM formats) by the latest
generation of PACS systems that could raise the implementation cost
significantly. Technologists and radiologists are required to undergo initial
training so that they can competently and efficiently operate in both
modes. Ongoing training, per international standards, is necessary for
operating at full functionality.
Discussion: The transition from film to fully digital mammography was a
difficult process but it was adopted due to the latter’s benefits on diagnosis
and workflow. DBT adds to the clinical benefits of FFDM but challenges
further the people involved in its implementation and the informatics
infrastructure. However, there are solutions, costly as they may be, that
could create an optimum clinical environment with significant short and
long-term benefits to all.
PERFORMANCE EVALUATION AND DOSIMETRY OF AN ANGIOGRAPHY
SYSTEM USING A NEW MULTISENSOR MEASUREMENT SYSTEM
Borr
as Caridad a, Castellanos Esperanza b. a Radiological Physics and Health
Services, Washington DC, United States; b Hospital Universitario San Ignacio,
, Colombia
Universidad Javeriana, Bogota
Background: The purpose of this investigation was to evaluate the usefulness and limitations of a new commercial instrument that uses both
ionization chambers and solid-state sensors for diagnostic radiology
equipment performance evaluation and dosimetry measurements on an
angiography system equipped with a flat-panel image receptor.
Materials and methods: The measurements were carried out on an Allura
XPer FD Philips of a hospital in Bogota, Colombia. Prior to their application,
the ion chambers and solid-state multisensors were checked for reproducibility, accuracy and linearity. Results of tube potential, examination
duration, pulse count and pulse width, as well as the calculated air-kerma
at the interventional reference point, were compared with the values
displayed by the Allura monitors for various clinical protocols using fluoro
and cine modes at several phantom thicknesses and found to agree within
manufacturer’s specifications.
Results: Reproducibility, accuracy and linearity of detectors were found to
be within tolerances adequate for diagnostic radiology. The automatic
exposure control of the angio system, tested by measuring variables such
as tube potential, filtration, tube current and pulse width vs. phantom
thickness for various clinical protocols and patient habitus, was found to be
excellent. The small size of the multisensors made the measurement task
easy. Air-kerma and/or air-kerma rate values at the patient entrance with
their corresponding half-value-layers for the most common angiographic
procedures, together with an assessment of image quality using a contrastdetail test tool, were determined, and typical patient doses were estimated. Highlights of the results for both adult and pediatric patients will
be presented. Maximum patient air-kerma rates did not exceed the limits
established by the Colombian Radiation Protection Regulations.
Discussion: The new measuring instrument was found to be an excellent tool
for patient radiation protection optimization and quality control tests. It can
acquire in very short times clinically relevant dosimetry information on sophisticated angiography systems that have many variables. This is mainly due
to the fact that several sensors can be used simultaneously and that data can
be acquired using pre-defined templates and exported to Excel files for trend
analysis. Of particular interest is the possibility of analyzing the waveforms
under different conditions. Examples will be shown and discussed.
11
SHOULD WE BE CONCERNED ABOUT THE POPULATION DOSE FROM
COMPUTED TOMOGRAPHY SCANS IN SHIRAZ, IRAN?
S.M.J. Mortazavi a, b, M. Nouri b, M. Haghani b, A. Bahador c, A. HashemiAsl c. a The Center for Research on Protection against Ionizing and Nonionizing Radiation, School of Paramedical Sciences, Shiraz University of
Medical Sciences, Shiraz, Iran; b Medical Physics Department, School of
Medicine, Shiraz University of Medical Sciences, Shiraz, Iran; c Vice
Chancellery for Health , Shiraz University of Medical Sciences, Shiraz, Iran
Background: Recent explosion in the use of high dose diagnostic radiological procedures such as CT scans and nuclear imaging tests has raised
concerns about the increased cancer risk associated with the use of these
technologies. Therefore, now there is a debate over the balance between
the benefits of early diagnosis of cancer and the risk of induced malignancies. In the United States it has been reported that the average radiation
dose from medical imaging has been increased more than six times but
there is no published data on such an increase in Iran. Despite the very
small risk of radiation induced malignancy from CT scans, the widespread
use of this diagnostic technology may lead to a significant risk at the
population level.
Aims: As in developing countries the uses and risks of computed tomography scans have not been adequately characterized, this study aimed at
answering the question whether we should be concerned about the population dose from computed tomography Scans in Shiraz, Iran?
Materials and methods: Information about the number of CT scans, scan
types and radiation doses was obtained from Namazi, Chamran and
Faghihi hospitals as the three largest hospitals in Shiraz city. Furthermore,
data about radiation doses from CT scans as well as scanning parameters
were collected for each hospital.
Results: In 2006, 48505 CT scans were performed in these three largest
hospitals. In 2011, 2012 and 2013 the number of CT scans were 86494,
84899 and 72337, respectively. Although in Chamran hospital, the number
of CT scans has grown from 7629 in 2006 to 27136 in 2012 (356% increase),
the overall growth rate is about 150%.
Conclusion: In spite of a 20-fold increase in the number of CT scans performed in the US (1980-2006) and a 12-fold increase in the UK, this
number has increased 1.5 times over the past 8 years in 3 largest hospitals
of Shiraz, Iran. As most of the increased medical exposures in the industrialized countries are due to CT scans and nuclear imaging, similar studies
should be performed on nuclear medicine tests and the proportion of total
radiation exposures which comes from these tests.
A MANUALLY-ACTUATED MRI COMPATIBLE ROBOTIC MANIPULATOR
FOR IMAGE-GUIDED INTERVENTIONS
Christoforos
Keroglou b,
Andrew
Eftychios
G.
Christoforou a,
Webb c, Nikolaos V. Tsekos d, Ioannis Seimenis e. a KIOS Research Center
for Intelligent Systems and Networks, University of Cyprus, Cyprus;
b
Department of Electrical and Computer Engineering, University of Cyprus,
Cyprus; c C.J. Gorter Center for High Field MRI, Leiden University Medical
Center, Leiden, Netherlands; d Medical Robotics Laboratory, University of
Houston, Houston, TX, USA; e Med. Physics Lab, Medical School, Democritus
University of Thrace, Alexandroupolis, Greece
Background: Performance of image-guided interventions under direct
MRI guidance is highly desirable, but a main obstacle has been the limited
accessibility to the patient inside the scanner’s gantry. The employment of
robotic manipulators has been proposed to overcome this limitation. Such
manipulators are required to be MRI compatible considering construction
materials, actuation and sensing. Moreover, they are required to have an
appropriate kinematic structure and be able to operate in a confined space
inside the scanner.
Methods: A novel MRI compatible manipulation system which is manually
actuated has been designed and developed. It is endowed with five degrees-of-freedom and was constructed of plastic materials. It is a generalpurpose manipulator, i.e., not scanner, anatomy, or application specific.
The kinematic structure and the dimensions were selected based on a
12
Abstracts / Physica Medica 30S1 (2014)
systematic space analysis. Different end-tools can be attached to the
manipulator to allow performing a variety of diagnostic and therapeutic
interventions, including image-guided biopsies, aspirations and drug delivery. Appropriate preoperative planning tools have been developed to
facilitate needle-targeting tasks. Guidance using intraoperative images is
facilitated by MRI visible markers attached to the end-tool.
Results: Systematic MRI compatibility testing inside a 3T scanner has
shown that the presence and operation of the manipulator had no effect on
the SNR of GRE images. Accuracy testing using appropriate phantoms
revealed a needle-targeting accuracy of 5mm. Experimental phantom
studies were carried out simulating various clinical applications including
MRI-guided biopsy and drug delivery. The system was also shown highly
effective while involved in MRI-guided arthrography which was simulated
using an appropriate ex vivo phantom.
Discussion: The developed MRI compatible manipulator could be suitable for various clinical interventions inside closed-type cylindrical
scanners. Compared to other proposed manipulators, it is manuallyactuated resulting in simplicity and lower cost. It also features a distinct
kinematic structure and an intuitive operation. By employing different
end-tools, the manipulator is expected to facilitate various clinical applications through the effective combination of direct MR imaging and
robotic manipulation.
Acknowledgements: This study was supported by the European Regional
Development
Fund and the Republic of Cyprus through the Research Promotion Foundation (Grant No. TEXNOLOGIA/MHX/0308(BIE)/05).
THE DEVELOPMENT OF AN EASILY ADOPTED HEAD AND ABDOMEN DWI
QUALITY CONTROL PHANTOM AND TEST DIFFERENT REGRESSION
ALGORITHMS FOR PRECISE APPARENT DIFFUSION COEFFICIENT (ADC)
MEASUREMENTS
T.G. Maris a, T. Boursianis a, G. Kalaitzakis a, E. Pappas b, G. Manikis c, K.
Marias c, A. Karantanas d. a Department of Medical Physics, University of
Crete, Heraklion, Crete, Greece; b Department of Medical Radiological
Technologists, Technological Educational Institute of Athens, Athens, Greece;
c
Institute of Computer Science, Foundation for Research and
TechnologyeHellas (FORTH), Heraklion, Crete, Greece; d Department of
Radiology, University of Crete, Heraklion, Crete, Greece
Purpose: The aim of this study is to develop an easily adopted head and
abdomen DWI quality control phantom and test different regression algorithms for precise Apparent Diffusion Coefficient (ADC) measurements.
Materials and methods: Twelve test tubes with different sucrose solution concentrations, simulating ADC values obtained from different
head and abdominal organs/lesions, embedded in a plastic water tank
served as a diffusion phantom. This was repeatedly scanned for over a 1
year period with a multislice single shot SE EPI DWI sequence and 10 b
values (0 to 1500). ADC maps were constructed using : (a) a Vendor
Specific (VS), (b) a Conventional Linear (CL), (c) a weighted linear (WL)
and (d) a Non Linear (NL) regression fitting models utilizing three sets of
b values with 2, 4 and 10 points respectively. ADC value precision figures
(ADC-ROI-CV) and long term time (LTT-CV) reproducibility figures
expressed by coefficient of variation (CV %) measurements were performed on each test tube with each fitting model. The diffusion phantom
was scanned with clinical DWI sequences for oncologic head and
abdominal imaging, namely SE EPI and Inversion Recovery (IR) EPI
sequences.
Results: ADC values of all test tube contents were in agreement with nominal
values. ADC measurements performed with 10 point method showed better
precision (mean ADC-ROI-CV ¼ 2 %) and LTT-CV (4.2%) as compared to 2- and
4 point methods. Post-hoc pairwise comparisons showed better discrimination when algorithms WL an NL were used (p<0.01), mean ADC-ROICV¼3.6 %. SE EPI DWI sequence performed excellently while IR EPI showed
big discrepancies and was rendered inadequate for quantitative analysis.
Conclusion: Phantom imaged with WL and NL algorithms enforced with
the 10-point method proved to be an excellent means for precise measurement of head and abdominal ADC values and allowed testing reliability of clinical DWI sequences.
Keywords: Diffusion Weighted Imaging, Apparent Diffusion Coefficient
CLASSIFICATION OF CERVICAL INTRAEPITHELIAL NEOPLASIA BASED ON
HISTOPATHOLOGICAL IMAGE ANALYSIS AND PATTERN RECOGNITION
METHODS
Christos D. Konstandinou a, Glotsos Dimitris b, Kostopoulos Spiros b, Pappa
Eleftherios
Lavdas d,
Dionisis
Cavouras b,
George
C.
Dimitra c,
Sakellaropoulos e. a Department of Medical Physics, School of Medicine,
University of Patras, Greece; b Medical Image and Signal Processing Laboratory,
Department of Biomedical Engineering, Technological Educational Institute of
Athens, 12210, Egaleo, Athens, Greece; c Pathology Laboratory, Iaso Thessalias
Hospital, Larisa, Greece; d Department of Radiology, Technological Educational
Institute of Athens, 12210, Egaleo, Athens, Greece; e Medical Physics
Department, School of Medicine, University of Patras, Greece
Background: Computer Science (B.Sc.), Bioinformatics (M.Sc.), PhD Student (Medical Informatics)
Cervical dysplasia is a precancerous condition, where the cells of the
cervical surface grow abnormally. If not treated cervical dysplasia could
lead to cervical cancer that is among the most common malignancy in
women. The Human Papilloma Virus (HPV) is the most frequent sexually
transmitted virus worldwide and has been recognized as one of the
most important causative factors for developing of Cervical Intraepithelial Neoplasia (CIN). The aim of the present study is the development of a pattern recognition system (PRS) for the discrimination
between mild dysplasia (CIN I) and moderate and severe dysplasia (CIN
II & CIN III). The clinical material comprised biopsies of patients diagnosed with stage I, stage II and stage III CIN. Images were digitized from
the original material using a Leica DM2500 digital light microscopy
imaging system. Textural features, multi-resolution (based on wavelet
analysis) and fractals-based features were computed for each one of the
digitized images in order to constitute the input data of the PRS, which
was designed and implemented for predicting the stage of CIN. The PR
system was structured using a variety of classifiers such as the Probabilistic Neural Network (PNN), the Support Vector Machine and the
Nearest Neighbor (NN) classifier. The PRS was trained using the leave
one out method and the exhaustive search for combinations up to four
features. The PNN accomplished the best accuracy with 88.23% using
four features combination (kurtosis-is a first order statistic which measures distribution’s asymmetry by indicating the degree of flatness near
its center, the maximum value of Horizontal detail coefficients of
wavelet analysis, the mean value of vertical detail coefficients of wavelet
analysis and the standard deviation (shows the values’ variation from
average) of diagonal detail coefficients of wavelet analysis). Preliminary
results are quite promising implying that image analysis features may be
utilized as a valuable descriptor for computer-assisted diagnosis in
staging of CIN.
Keywords: Cervical Intraepithelial Neoplasia (CIN), Cervical cancer,
Pattern recognition
LOW BIRTH WEIGHT IN BABIES BORN TO MOTHERS FROM HIGH LEVEL
NATURAL RADIATION AREAS OF RAMSAR, IRAN
S. Taeb a, S.M.J. Mortazavi b, c, H. Mozdarani d, S.A.R. Mortazavi e, A.
Soleymani f, M. Haghani c, A. Soofi e. a Master Student of Radiobiology,
Radiology Department, School of Paramedical Sciences, Shiraz University of
Medical Sciences, Shiraz, Iran; b Professor of Medical Physics, Medical
Physics Department, School of Medicine, Shiraz University of Medical
Sciences; c Ionizing and Non-ionizing Radiation Protection Research Center
(INIRPRC), Shiraz University of Medical Sciences; d Professor of Medical
Genetics, School of Medical Sciences, Tarbiat Modares University, Tehran,
Iran; e Medical Student, School of Medical Sciences, Shiraz University of
Medical Sciences Shiraz, Iran; f PhD Student of Epidemiology, Shiraz
University of Medical Sciences, Shiraz, Iran
Background: Human beings live in an environment laden with different
types of stressors such as ionizing and non-ionizing radiation. Ramsar, a
city in northern Iran, has some areas where some of the highest levels of
natural radiation, as compared to other inhabited areas, are recorded all
over the world. In some areas of Ramsar, residents receive an annual radiation dose from background radiation that is about 13 times higher than
Abstracts / Physica Medica 30S1 (2014)
the 20 mSv/y as a dose limit for radiation workers. It has been previously
indicated that the risk of low birth weight (LBW) is enhanced due to
maternal medical exposures during pregnancy
Objectives: The main aim of this study was to find out whether there is a
relationship between long term exposure to background radiation levels
above the normal amount and the risk of low birth weight.
Materials and methods: A cross-sectional study was conducted in high
background radiation areas (HBRAs) of Ramsar and neighboring areas with
normal levels of background radiation (NBRAs). An interview was conducted using a questionnaire administered to 320 women from HBRAs and
280 women from NBRAs by an expert radiation biologist. Screening and
stratified random sampling were used for selection of the subjects (vaginal
or caesarian).
Results: The mean birth weight of the newborns to mothers from HBRAs
was 2820.3 ± 654.2 g. and that of the newborns to the mothers from NBRAs
was 2925.2 ± 543.2 g. The difference between the mean weight of the
newborns of the mothers from HBRAs and NBRAs was statistically significant (P¼0.034).
Conclusions: In this study, it was revealed that the birth weight may be
associated with the level of background radiation in the mothers’ living
area before and during pregnancy. However, the results of the present
study question the reports given by previous studies revealing that pregnant mothers exposure to ionizing radiation enhanced the occurrence of
low birth weight.
Keywords: Ionizing radiation, Non-ionizing radiation, Pregnancy, Low
birth weight, Term labor
RADIATION
DOSE
IN
ENDOSCOPIC
RETROGRADE
CHOLANGIOPANCREATOGRAPHY: DOES THE OPERATOR EXPERIENCE
REALLY MATTER?
V. Tsapaki a, K. Paraskeva a, A. Giannakopoulos a, S. Papasavvas a, N.
Mathou a, P. Aggelogiannopoulou a, S. Triantopoulou a, H. Al Malki a, I.
Tsalafoutas b, Ch. Triantopoulou a, J.A. Karagiannis a. a Konstantopoulio
General Hospital of Nea Ionia, Athens, Greece; b “Agios Savvas” General
Hospital, Athens, Greece
Background: Endoscopic retrograde cholangiopancreatography (ERCP)
is the gold standard technique for treating the disorders of the billiary
and pancreatic ducts . During ERCP, a side viewing endoscope passes
through the mouth, esophagus and stomach into the duodenum and
the papilla of Vater is cannulated using fluoroscopy as a guidance.
During fluoroscopic guidance, the position of the endoscope and its
relationship within the duodenum is .verified in real time. Therefore,
extensive use of X-ray fluoroscopy and a large number of radiographs
are possible. It is also a highly technical and complex technique that
greatly depends on the endoscopist’s experience. The quality and success of ERCP as well as limitation of various clinical complications
depend on the training of the endoscopist. The aim of the study was to
compare patient’s radiation exposure during ERCP, in relation to the
endoscopist’s experience.
Materials and methods: All ERCPs were performed using a conventional
radiology X-ray machine (Philips Essenta) with a Kerma Area Product
(KAP) meter installed in the X-ray tube.. The meter was calibrated according to the method summarized in the ‘national protocol for patient
dose measurements in diagnostic radiology’ developed by the National
Radiological Protection Board (NRPB). In each ERCP, KAP in Gycm2, fluoroscopy time (FT) in min and total number of X-ray films (F) were recorded
. All ERCP procedures were done under sedation and with a fixed set-up for
the patient. The X-ray system was controlled by the radiographer according to endoscopist’s instructions. The ERCPs were performed by a high
volume endoscopist ( HVE) (more than 200 ERCP/year for 10 years) and a
low volume endoscopist (LVE) in its first year after finishing basic ERCP
training
Results: A total number of 239 patients were included in the study, 56 of
which were performed by LVE and 183 by HVE. Median KAP was
significantly lower for the patients done by the HVE ( 11,42 Gy.cm2
(range: 0,81-175,93 Gy.cm2) vs 23,14 Gy.cm2 (range: 1,20-198,02
Gy.cm2).
13
Similarly, FT was shorter for the HVE (Median T: 3,5 min) versus LVE
(Median T: 2,3 min). For both operators, radiation dose was correlated with
number of films taken (f), (LVE): 0,59 and HVE: 0,64.
Conclusion: Our study shows that ERCP patient radiation dose is significantly higher for a low volume cases endoscopist. It is therefore essential
to draw the attention of the ERCP practitioners, especially the beginners, to
the radiation their patients receive compared to high volume endoscopists.
COMPARISON OF ENTRANCE SURFACE DOSE OF FOUR ROUTINE CT
EXAMINATIONS: HELICAL SCAN VERSUS WIDE VOLUME SCAN MODES
Ying-Lan Liao a, Yan-Shi Chen b, Hui-Yu Tsai b, c, d. a Department of Biomedical
Engineering and Environmental Sciences, National Tsing Hua University,
Hsinchu 300, Taiwan; b Department of Medical Imaging and Radiological
Sciences, College of Medicine, Chang Gung University, Taoyuan 333,
Taiwan; c Institute for Radiological Research, Chang Gung University /
Chang Gung Memorial Hospital, Taoyuan 333, Taiwan; d Healthy Aging
Research Center, Chang Gung University, Taoyuan 333, Taiwan
Background: Computed tomography (CT) plays an important role in
diagnostic radiology for radiologists because of excellent image quality
within a very short acquisition time. A 320-detector row CT scanner has a
collimation width up to 160 mm and a specific scan mode called wide
volume scan mode based on axial scan mode was developed. The total
scan length of a patient is adjusted automatically into several scan ranges
equally. Then the patient will be scanned like a step and shoot procedure
to acquire the imaging data. However, the mechanism of the wide volume scan mode together with the automatic tube current modulation
(ATCM) technique remains unclear. The purpose of our study was to
assess the surface dose distribution during wide volume scan mode of
four adult CT examinations and compare it with those of helical scan
modes.
Materials and methods: An averaged-sized anthropomorphic phantom
was scanned with four adult CT examinations (head, chest, abdomen, and
chest-abdomen-pelvis (CAP)) of a 320 detector-row CT scanner (Aquilion
ONE, Toshiba, Japan) (Table 1). The ATCM technique (SureExposure 3D,
Toshiba, Japan) was used during the wide volume scan mode and helical
scan mode. The radiochromic film strips (Gafchromic XR-QA2, ISP, USA)
were used to measure the entrance surface dose. The values of effective
tube current time product (Eff. mAs) of each z-axis position were
recorded.
Results: The Eff. mAs of wide volume scan mode is lower than that of
helical scan but the surface dose from over-lapping between volumes
ranges from 20% to 65% higher than other region. The contribution of overlapping dose is proportional to the number of volumes of the wide volume
scan mode.
Discussion: We have assessed the radiation dose distribution of four
adult routine protocols with wide volume scan mode in a 320 detectorrow CT scanner and compared it with those of helical scan mode. The
over-lapping dose that locates in radiosensitive organ region such as
thyroid, breast, or gonads will increase the radiation risk burden to a
patient.
Figure 1-14: (a) Anterior-to-posterior (AP) and (b) lateral (LAT) surface doses
comparison between helical scan and wide volume scan modes of (1) head, (2)
chest, (3) abdomen, and (4) chest-abdomen-pelvis (CAP) CT examinations.
14
Abstracts / Physica Medica 30S1 (2014)
Table 1
Scan parameters of adult routine CT examinations
Head
Scan mode
Helical
NT (mm)2
Volume number
Tube voltage (kVp)
Tube rotation time (s)
SureExposure3D
Min-Max mA
Effective mAs
AIDR3D3
Pitch
320.5
–
120
0.75
Off
DFOV4
kernel
Scan range (mm)
Slice (mm)
Interval (mm)
CTDIvol (mGy)5
DLP (mGy cm)5
1
2
3
4
5
232
On
HP 27
PF 0.844
220 (S)
FC68
170
5.0
5.0
50.5
946.6
Chest
Wide volume
Helical
2
120
0.75
Off
800.5
–
120
0.5
HQ
232
On
–
220 (S)
FC68
192
5.0
5.0
49.6
1070.6
–
On
HP65
PF 0.813
320 (M)
FC18
385
5.0
5.0
22.7
983.6
CAP1
Abdomen
Wide volume
Helical
4
120
0.5
HQ
800.5
–
120
0.5
HQ
–
On
–
320 (M)
FC08
424
5.0
5.0
10.78
514.8
–
On
HP65
PF 0.813
320 (M)
FC18
460
5.0
5.0
11.2
576.3
Wide volume
Helical
Wide volume
5
120
0.5
HQ
800.5
–
120
0.5
HQ
8
120
0.5
HQ
–
On
–
320 (M)
FC08
460
5.0
5.0
13.55
713.5
–
On
HP65
PF 0.813
320 (M)
FC18
680
5.0
5.0
11.6
839.2
–
On
–
320 (M)
FC08
736
5.0
5.0
14.35
1150.1
Chest to Pelvis
Number of detector, T: detector thickness
Adaptive Iterative Dose Reduction in Three-Dimensional
Display Field of View
Volume Computed Tomography Dose Index and Dose-Length Product displayed on the console
CUMULATIVE RADIOGENIC CANCER RISKS ASSOCIATED WITH A LUNG
CANCER SCREENING PROGRAM EMPLOYING LOW-DOSE 256-SLICE CT
constitutes only a minute fraction of the intrinsic high cancer risk associated with such a population.
Ioannis Seimenis a, b, Kostas Perisinakis c, Antonis Tzedakis d, John
Damilakis c. a Med. Physics Lab, Medical School, Democritus University of
Thrace, Alexandroupolis, Greece; b Medical Diagnostic Center ‘Ayios
Therissos’, Nicosia, Cyprus; c Department of Medical Physics, Medical
School, University of Crete, Heraklion, Greece; d Department of Medical
Physics, University Hospital of Heraklion, Heraklion, Greece
EFFECTIVE DOSE ESTIMATE AND IMPLEMENTATION OF THE SIZESPECIFIC DOSE ESTIMATE INDEX IN MULTIPLE MYELOMA PATIENTS
EXAMINED BY LOW DOSE MDCT PROTOCOL
Background: Lung cancer screening (LCS) with annual chest low-dose CT
(LDCT) has been recently recommended for individuals aged 55-80 years
at high risk of lung cancer. This study aims at determining the radiation
burden and the lifetime attributable risk (LAR) of radiation-induced cancer
in individuals undergoing 256-slice LDTC for LCS purposes.
Methods: Chest 256-slice LDCT exposures were simulated on mathematical anthropomorphic phantoms of varying body mass index (BMI)
using Monte Carlo methods. Normalized and absolute organ doses, as
well as effective doses (ED), were estimated. Organ-specific and total
cancer LARs were estimated using published age- and sex-specific risk
factors. Cumulative LARs from repeated annual LDCT studies were estimated. Total LARs were compared to corresponding nominal lifetime
intrinsic risks of cancer (LIRs). Lung cancer LAR was benchmarked
against the intrinsic lung cancer risk associated with the screening
population.
Results: Lung and breast (females) are the organs receiving the highest
doses from chest LDCT. Organ-based ED estimates were 0.76mSv and
0.53mSv for females and males of normal BMI, respectively. Absorbed
organ doses and ED decrease considerably with BMI. A single chest LDCT
exposure at 55 years is associated with 2.0 and 4.8 new cancer incidents
per 105 average-sized males and females, respectively. The cumulative LAR
of radiogenic cancer from repeated annual LDCT studies between the ages
of 55 and 80 years was estimated to incur a relative increase in the LIR of
being diagnosed with cancer by less than 0.3% and 0.1% in females and
males, respectively. For average-sized males and females, repeated annual
LDCT exposures lead to 25 and 59, respectively, new lung cancer cases per
105 LCS program participants.
Discussion: Estimated radiation burden and theoretical radiogenic cancer
risks associated with repeated annual 256-slice LDCT chest exposures may
alleviate radiation-related concerns regarding the implementation of a LCS
program. Provided a modern technology scanner and a carefully considered low-dose protocol are employed, total radiation-induced cancer risk
seems to minimally aggravate the lifetime intrinsic cancer risk for the
screening population. Furthermore, the radiogenic lung cancer risk
M. Michalitsi a, A. Boultadaki b, J. Floros a, M. Rouchota a, M. Argyrou a, A.
Valassi a, I. Baka a, B. Letsas a, S. Synefia a, M. Andreou a, c, B.
Koutoulides b, M. Lyra a. a Radiation Physics Unit, 1st Radiology Dep.,
University of Athens, Athens, Greece; b Computed Tomography Unit, 1st
Radiology Dep., University of Athens, Athens, Greece; c Medical Physics
Department, University of Athens, Athens, Greece
BKG: Low-dose whole-body MDCT protocol in the diagnosis of Multiple
Myeloma (MM) has been established as an alternative to conventional Xray imaging. CT diagnostic examination for suspected Multiple Myeloma is
usually performed by using a whole body protocol.
Size-Specific Dose Estimate (SSDE) is a recently proposed dose index to
quantify the dose received by a patient during a scan, by also taking into
account the patient’s size.
To estimate the patient dose from Low Dose MDCT protocol, Effective Dose
(ED) and SSDE index were calculated.
Materials and methods: CT scans were performed on a Philips CT Brilliance
16 scanner, using a helical whole body low dose protocol.
Two different methods for evaluating the dose delivered during the CT scan, in
a group of 60 patients examined for Multiple-Myeloma (MM), are considered.
The first method is based on the DLP, which is converted to ED. The conversion
is based on the data published by Huda et al (2008). The second method is by
calculating the SSDE index, determined by multiplying the Volume CT Index
(CTDIvol) of the scanner for a reference phantom of 16 or 32 cm and the size
dependent conversion factors introduced by the AAPM Report 204.
A correction factor was applied both to the ED and the SSDE values to take
into account the differentiation in dose due to irradiating both head and
trunk with a whole body CT protocol.
Results: Data were collected in Evorad RIS-PACS Workstation 2.1 and
transferred in SPSS-19 software for statistical evaluation.
The patient dose received during a CT scan in MM examinations was
evaluated for a wide range of effective body diameters. It was found that
the SSDEs present a decreasing trend in relation to patient body weight,
whereas EDs do not correlate to patient body size. A comparison of ED and
SSDE values, with values using Sadruddin’s web calculators (based on
Huda W&He W,2012) gave same order results.
Abstracts / Physica Medica 30S1 (2014)
Discussion: ED provides a reliable estimate of radiation amount delivered
but does not take into account the patient’s size. SSDE provides a dose index
based on the CTDIvol and also takes into account the patient’s size and
provide a specific dose estimate for each patient.
References:
Huda et al, Converting DLP to Effective Dose at CT, Radiology: Vol. 248:
No3, pp995-1003.
Huda W,He W. Estimating cancer risks to adults undergoing body CT examinations. RPD 2012; 150:168-79
QUANTITATIVE PERFORMANCE EVALUATION
SCHEMES IN FOLLOW-UP LUNG MDCT
OF
REGISTRATION
Georgios Vlachopoulos, Spyros Skiadopoulos, Anna Karahaliou, Lena
Costaridou. Department of Medical Physics, School of Medicine, University
of Patras, Patras, Greece
Background: Multi-Detector Computed Tomography is the modality of
choice for quantification and follow-up monitoring of Interstitial Lung
Disease (ILD). ILD monitoring and response to therapy quantification involves comparison of quantified disease extent between scans obtained at
different time instances (follow-up scans). A critical image analysis step,
prior to disease extent quantification, is lung field registration due to alterations in lung field radiological appearance (i.e. disease progression), as
well as elastic nature of lung tissue. This study investigates the effect of
registration components (i.e. transform, optimizer and cost function) on
registration accuracy of ILD affected lung fields.
Materials and Methods: A set of 48 registration schemes was generated
using 3 transforms (rigid, affine and 3rd order B-Spline), 4 optimizers
(Standard Gradient Decent, Random Step Gradient Decent, Finite Difference Gradient Decent and Adaptive Stochastic Gradient Decent) and 4 cost
functions (Sum of Square Differences, Mutual Information, Normalized
Mutual Information and Normalized Correlation Coefficient). In order to
avoid intrinsic variations caused by disease progression, the approach of
artificially generating follow-up data, based on 5 clinical follow-up ILD
affected volumes, was adopted. The above registration schemes were
applied on this follow-up data set. Performance evaluation of the registration schemes was achieved by means of the Euclidean distance metric
between corresponding points of original and registered data in (a) ILD
affected volumes (dILD) and (b) normal lung parenchyma (dnormal), and by
means of Lung Volume Overlap Error (LVOE). A non-parametric statistical
test was performed (Wilcoxon signed-ranks test) to investigate existence
of statistically significant differences among registration schemes’
performance.
Results: Registration schemes including the Adaptive Stochastic Gradient
Decent optimizer yielded statistically significant higher performance (pvalue<0.05) as compared to all registration schemes considered, in terms
of dILD (0.23±0.06), dnormal (0.21±0.05) and LVOE (10.95%±2.50%). There was
no statistically significant difference (p>0.05) in registration schemes’
performance with respect to transform and cost function components.
Discussion: Results have demonstrated that the optimizer accounts for a
crucial component, affecting significantly registration performance.
Registration schemes including the Adaptive Stochastic Gradient Decent
optimizer suggest an increased potential in accurate lung fields registration and ILD quantification.
A METHOD FOR QUANTIFYING METAL ARTIFACTS IN MRI
Ioannis Vrachnis a, George Vlachopoulos a, Anna Karahaliou a, Thomas
Marris b, Lena Costaridou a. a Department of Medical Physics, School of
Medicine, University of Patras, Patras, Greece; b Department of Medical
Physics, Faculty of Medicine, University of Crete, Iraklion, Crete, Greece
Background: Metal implants are a common source of artifacts in MRI, due
to susceptibility effects, resulting in local distortions of the magnetic field.
Previously proposed methods for quantification of MRI artifacts, employ
observer-depended methods. The current study proposes an algorithmic
approach for artifact quantification in MRI, tested in a phantom-based
study.
15
Materials and Methods: A stainless steel head, used in total hip arthroplasty, was embedded in water and imaged at 1.5 Tesla with turbo spin
echo pulse sequences at three bandwidths (210, 295 and 405 Hz/pixel).
The proposed method was applied on selected coronal slices at the vicinity
of the implant. The method is based on the fact that distortions responsible
for signal voids and pile ups, are both manifested as abrupt alterations of
image gradient. Prior to image gradient calculation, a denoising step is
considered to eliminate spurious noise effect introduced in high bandwidth acquisitions. Image gradient magnitude is then calculated, followed
by an automatic cross entropy thresholding method. Finally, the artifact
extent is quantified in terms of image area percentage. A non-parametric
statistical test was performed (Kruskal Wallis Test) to investigate existence
of statistically significant differences among artifact extent in three
different bandwidth acquisitions.
Results: Statistical analysis confirmed that high bandwidth acquisitions
yielded statistically significant lower artifacts as compared to medium and
low bandwidth acquisitions (p-value¼0.032<0.05).
Discussion: The proposed artifact quantification method is based on the
physics of artifact generation, assuming that image gradients capture the
distortions of the magnetic field. Results have demonstrated that the
proposed method accounts for a promising technique for identification
and quantification of MRI artifacts introduced by metal implants. This
method is observer independent and thus repeatable, and could be used as
a part of a standardization procedure.
STEREOTACTIC
RADIOSURGERY/RADIOTHERAPY
PRE-TREATMENT
PLAN VERIFICATION USING CALIBRATION-FREE GAFCHROMIC EBT2
FILMS
Pappas Evangelos. Technological Educational Institute of Athens, Athens,
Greece
Purpose: Stereotactic Radiosurgery/Radiotherapy (SRS/SRT) Quality
Assurance (QA) and Plan-Verification is a challengin task. EBT2 Gafchromic
films have been proved to be a useful tool for this purpose. However, their
dose-response is depended on a number of parameters such as scanning
mode, ambient light effect, post-irradiation coloration, orientation of
scanning and film storage temperature. The aim of this work is to investigate the validity and accuracy of the use of calibration-free EBT2 films for
SRS QA and plan verification purposes overcoming the above mentioned
problems that affect the films calibration curve and therefore the filmcalibration-based 2D dose measurements.
Materials and Methods: The following experimental and data-analysis
steps were followed:
1 e EBT2 films irradiation and scanning for calibration purposes. The
studied dose-range was up to 1200 cGy. The film calibration curve and the
dose-region wherein the films exhibit a linear dose-response were
derived.
2 e EBT2 films irradiation using a selected SRS plan. The delivered doses
were within the linear dose-response region
3 e Use of the film calibration data and the SRS-irradiated-film in order to
derive 2D relative dose distribution.
4 e Derivation of 2D relative dose distribution without the use of film
calibration data. The linearity of dose-response was used for this purpose.
5 e Comparison of the 2D relative dose distributions derived from the
steps 3 and 4 against the corresponding Treatment Planning System (TPS)
calculated 2D dose distribution.
Results: A EBT2-film linear dose-response was observed in the dose-range
of 0-400 cGy. Within this dose range the relative changes of the net-signal
from film scanning equals to the relative change of dose. The 2D relative
dose distributions derived using the steps 3, 4 and TPS were practically
identical. A gamma-index analysis (2 mm,2%) revealed a satisfying
agreement between each couple of these 2D data-sets (gamma<1 for ~96%
of the pixels).
Conclusions: EBT2 films used following the presented calibration-free
methododoly, can become a very useful tool for a valid and easy SRS QA
and plan verification process overcoming the problems related with the
film-response sensitivity to a number of well-known factors that affect the
film-calibration curve.
16
Abstracts / Physica Medica 30S1 (2014)
A SEMI-EMPIRICAL MODEL OF IN-FIELD AND OUT-OF-FIELD
BREMSSTRAHLUNG DOSE DISTRIBUTION IN HIGH ENERGY ELECTRONS
BEAMS USED IN EXTERNAL RADIOTHERAPY
M. Mohamad Alabdoaburas a, b, c, D. Lefkopoulos b, J.Vu Bezin a, b, c, J.P.
Mege b, A. Veres d, F. De Vathaire a, b,c, I. Diallo a, b, c. a Inserm, CESP Centre
for research in epidemiology and population health, U1018, radiation
epidemiology team, Villejuif, 94807, France; b Institut Gustave Roussy,
e Paris-Sud, Orsay, 91405, France;
Villejuif, 94805, France; c Universit
d
Equal-Estro Laboratory, Villejuif, 94805, France
Introduction: A better understanding of the dose distribution effects in
normal tissues becomes essential to know how best to exploit modern
technologies in radiotherapy. Bremsstrahlung dose component became
important when scattering dual-foils and scrapers applicator are used
compared to scanned electron beam and cone applicator. Several works
have been reported for analyzing bremmstrahlung dose component inside
the irradiation field. The aim of this work to develop a semi-empirical
model for estimating the bremsstrahlung dose distribution at any point in
the patient in-field and out-of-field.
Materials and methods: The bremsstrahlung dose component in electrons beams arises from four main sources: scattering dual-foils, jaws,
applicator’s scrapers and insert of cerrobend, we neglected bremsstrahlung generating in the patient. Our model consists in two main parts: in
the first part, we calculated the angular energetic fluence distribution for
every bremsstrahlung photon source, by using an existing model based on
multi-scattering theorem. In the second part, we calculated the relative
number of irradiated pixel by primary electrons beam in every bremsstrahlung photon source. All programmings were executed by Matlab. All
detailed information about the geometry, material composition, and dimensions of each component have been provided by manufacturer. The
most of data about the electrons interactions with matters based on ICRU1984 data. Measurements of bremsstrahlung dose component are achieved via thermoluminescent dosimeters powder TLD-700, from 0cm to
70cm from the beam central axis, at depth of 10cm in water phantom for
Varian 2300C/D operated at 6,12,9 and18MeV.
Results: We evidenced that out-of-field bremsstrahlung dose issuing
essentially from applicator’s scrapers, while out-of-field bremsstrahlung
dose generating in scattering dual-foils is neglected. In-field bremsstrahlung dose comes essentially from scattering dual-foils which represents
70%-80% of total in-field bremsstrahlung dose. Our modelling results have
shown very good agreement between calculated and measured values infield and out-of-field. The average difference between calculated and
measured values is less than 10%, which stills small in absolute term.
Conclusion/perspective: Our approach can be used to provide good representation of bremsstrahlung dose distributions in all healthy tissues for
any applicator size and type and for any electron beam energy used in
high-energy electron beam therapy. The calculating time is relatively
short. To take account total peripheral dose out-of-field, an additional
model is under developing to estimate out-of-field scattered electrons
dose component.
Key words: Electron beam-therapy; Out-of-field dose; Bremsstrahlung
component.
disease. Reference points for measurements were predetermined on the
first CT scan indicating positions of neck region and enlarged nodes. Surface dose was then measured by TLD and Mosfet at the specified points
during treatment sessions. The measurements were repeated twice
weekly for each patient and normalized to that of week one.
Results The consecutive CT scans revealed continuous reduction in volume
of CTV1 which reduced by 15.7±6% by the end of treatment (figure 1). The
significant change in CTV1 volume was in week 2, 3 and 4 in comparison of
each week with the preceding week (34.5cm3, 8.7cm3,14.7cm3 respectively) (p¼0.002, 0.01, 0.02 respectively) (Table1). The TLD and MOSFET
measurements revealed average increase in surface dose up to 123.5±10%
and 130.5±5% respectively (figure2). A significant correlation was found
between CTV1 reduction in volume and increase in surface dose (Pearson
correlation coefficient ¼ -0.913, p¼0.015).
Conclusion Significant reduction in volume of CTV1 reflects the
shrinkage of the neck region. Surface dose in the neck region was highly
influenced by the noticed shrinkage. These increments in dose can be
explained due to the resulting air gap between patient skin and the
thermoplastic mask and also the increased probability of tangential
segments/subfields in the IMRT treatment. Adaptive protocols and
defining superficial regions as OAR during optimization process can
minimize surface dose increase.
Keywords: Surface dose, IMRT, weight loss, Anatomical variation.
Figure 1. Clinical target volume relative changes normalized to initial volume of
week0 over treatment weeks among patients with head-and-neck cancer (Pn).
INVESTIGATION OF SURFACE DOSE VARIATION DUE TO NECK
SHRINKAGE IN IMRT TREATMENT FOR HEAD AND NECK CANCER
PATIENTS
M. Abd Al Moez a, H. Al Zawam b. a Department of Medical Physics, Cairo
University Hospital, Cairo, Egypt; b Department of Clinical Oncology, Cairo
University Hospital, Cairo, Egypt
Purpose IMRT plans are generated using data obtained from a single CT
scan which don’t reflect the tissue changes during the treatment course.
This in turn could alter the dose in the surface and superficial regions
which becomes more important when using the inverse planning algorithm for IMRT. Thus the aim of this study was quantifying the magnitude
of neck shrinkage and the corresponding dosimetric variations in the superficial region during IMRT treatment weeks.
Method A single observer performed all the delineation procedures for
fifteen patients of H&N cancer. For all patients CT scans were acquired by
the end of week 2, 3, 4 and5 of treatment following the planning CT. on
each CT scan CTV1 was defined as neck regions at high risk for microscopic
Figure 2. Neck surface dose variation during treatment weeks normalized to week one.Ă
Abstracts / Physica Medica 30S1 (2014)
Table 1
Absolute and relative mean volume changes and statistical parameters CTV1
throughout the treatment course.
weekly
comparison
mean absolute
difference±S.D*
(cm3)
maximum
difference
(cm3)
minimum
difference
(cm3)
Percent
reduction
(%)
p- value**
week 0 and
week 2
week 2 and
week 3
week 3 and
week 4
week 4 and
week 5
34.5±30
128.00
3.00
8.2
0.002
8.7±4.7
18.80
2.00
2.7
0.01
14.7±10
33.00
1.20
4.2
0.02
8.6±6.9
25.40
1.20
2.4
0.12
* S.D ¼ standard deviation. ** Results is significant if p<0.05
DEVELOPMENT OF A WATER CALORIMETER AS THE ABSORBED DOSETO-WATER PRIMARY STANDARD FOR CHINA
K. Wang a, S. Jin a, X. Yang a, J. Zhang a, M. McEwen b, C. Cojocaru b, C.
Ross b. a National Institute of Metrology (NIM), China; b National Research
Council of Canada (NRC), Canada
In collaboration with the National Research Council Canada (NRC), the
National Institute of Metrology, China (NIM) is developing a new primary
standard for absorbed dose to water at radiotherapy dose levels. The
standard is based on a water calorimeter and is designed to operate in Co60 and megavoltage photon beams from a linear accelerator. The main
features of the calorimeter are as follows:
i) operation at 4 ºC to eliminate the problems associated with convection in
water phantoms at room temperature;
ii) a low-noise temperature measurement circuit able to resolve temperature differences at the mK level;
iii) capability to investigate different water purities and determine the heat
defect due to dissolved gases;
iv) potential extension to determination of absorbed dose in high-energy
electron beams and HDR brachytherapy;
v) determination of absorbed dose to water with a standard uncertainty of
better than 0.4 %.
Commissioning of the calorimeter involved a comparison with the present
NIM standard of absorbed dose and a comparison with the NRC primary
standard water calorimeter. Other investigations carried out included: the
effect of environmental changes on the temperature control; repeatability
of the system over the course of several weeks; stability of thermistor
calibrations to determine the radiation-induced temperature rise; capability of the linac to deliver consistent doses (suitable for primary standards measurements) over the course of a day and determination of
correction factors for beam uniformity for a range of detector geometries.
A full uncertainty analysis indicates that the target uncertainty specification can be achieved. This new standard will significantly reduce the uncertainty of ion chamber calibrations for Chinese radiotherapy centres and
open up new areas of research for the NIM.
ADVANCED RADIATION TECHNIQUES: STEREOTACTIC BODY RADIATION
THERAPY (SBRT) IN EARLY STAGE INOPERABLE LUNG CANCER DISEASE
D. Katsochi, S. Kosmidis, A. Fotopoulou, G. Kollias, C. Paraskevopoulou, P.
Kosmidis. Radiation Therapy Center of Diagnostic and Therapeutic Center
of Athens, HYGEIA
Purpose/Objectives: To present stereotactic body radiation therapy as a
highly conformal treatment, in compare to conventional radiation therapy,
that allows dose escalation and reduced treatment volumes, as a non
invasive alternative to operation in early lung cancer disease. Preliminary
data of Clinical experience in Radiation Oncology Department of DTCA
HYGEIA.
Materials/Methods: Between May 2009 and March 2014, 15 patients with
pulmonary tumors, medically inoperable, were treated with SBRT using
daily image guidance (cone beam CT) for patient positioning and target
localization. Computed tomography (CT scan) and PET computed tomography (FDG/PET) were used for target delineation and planning. Median
17
prescription dose was 36 Gy in 3 fractions in 9 pts or 30Gy in 5 fractions for
3 pts with poor pulmonary function.
Results:All patients completed treatment. Median follow up was 13
months (range 3-20). All patients achieved tumor local control, 12pts with
complete tumor regression and 3pts with minimal residual tumor in witch
remains stable at follow up. None patient presented blood toxicity or
pulmonary toxicity (pneumonitis) except for two patients who were
treated with corticosteroids.
Conclusions:Image guided SBRT in selected patients is a feasible, safe, and
effective treatment for medically inoperable early stage lung cancer.
EARLY AND SAVE TUMOR RESPONSE USING
CONCOMITANT BOOST RADIOTHERAPY TECHNIQUE
IMAGE
GUIDED
D. Katsochi, C. Paraskevopoulou, S. Kosmidis, A. Fotopoulou, G. Kollias, P.
Kosmidis. Radiation Therapy Center of Diagnostic and Therapeutic Center
of Athens, Hygeia
Purpose/Objectives: Local control of disease is often one of the main objectives in patients with advanced unresectable head and neck, lung, cervical and brain tumors. The introduction of image guided radiotherapy
offers the opportunity to safely apply a supplementary dose to the
macroscopic disease. This accelerated radiotherapy course, known as
concomitant boost, has the advantage of increasing the total dose delivered and tumor response without increasing the number of fractions.
Materials/Methods: From May 2009 to March 2014, 127 patients were
treated with concomitant boost technique. The distribution of primary
tumors was 73 patients with lung cancer, 35 patients with head and neck
cancer,11 patients with brain tumours and 6 patients with cervical cancer.
patients received chemotherapy during radiation therapy. Patients were
treated using the conformal or VMAT technique. Planning target volume
(PTV) was treated daily with 1.8 Gy for 5 to 6 weeks to a total dose of 45-54
Gy, while the dose to the Gross Tumor Volume (GTV) was boosted up to 5565 Gy depending on the anatomic region. Organs at risk were irradiated to
safe limits. In 74% of the patients we readapted the treatment plan due to
local tumor regression using image guidance data (CBCT).
Results: All patients completed the treatment plan with no major toxicity.
Follow up was scheduled at the end of the treatment, three and nine months
after. All patients achieved local tumor control, 78 patients with complete
tumor response, 39 patients with partial response and 10 with stable disease.
Conclusions: Concomitant boost in combination Image Guided Radiotherapy is a feasible, safe and effective treatment for patients with unresectable carcinomas. Results are encouraging and promising regarding
early locoregional disease control.
THE POTENTIAL IMPACT OF DATAMINING AND RAPID LEARNING IN
RADIOTHERAPY: A LUNG CANCER SURVIVAL DECISION SUPPORT
SYSTEM IN ROUTINE CLINICAL PRACTICE
D.I. Thwaites a, A. Dekker b, L. Holloway c, S. Vinod c, G. Delaney c, G.
Goozee c, M. Bailey d, A. Miller d. a Institute of Medical Physics, School of
Physics, University of Sydney, Australia; b Radiation Oncology, Maastricht
University Medical Centre, Maastricht, The Netherlands; c Radiation
Oncology, Liverpool Cancer Therapy Centre, Liverpool (Sydney), NSW,
Australia; d Radiation Oncology, Illawarra Cancer Care Centre, Wollongong,
NSW, Australia
Large amounts of data are collected on radiotherapy (RT) patients and
treatments. This resource could provide clinical evidence to help future
decisions. A collaborative project has begun between Australian RT centres
and MAASTRO to evaluate the feasibility and impact of datamining of
routine clinical RT data and the use of rapid learning tools in routine
practice. The initial pilot was for non-small cell lung cancer (NSCLC) patients in the Liverpool Hospital Cancer Centre.
An open-source rapid learning system was installed. From local data
sources, various parameters were extracted for all lung cancer patients,
without quality review: histology, gender, age, ECOG status, lung function
(FEV1), lymph node status, tumour volume, dose and survival. Missing
data were imputed using Bayesian methods. The DSS was applied to predict two-year overall survival (S2Y) in stage I-IIIB NSCLC patients treated
with curative (>45Gy) or palliative RT.
18
Abstracts / Physica Medica 30S1 (2014)
Of the 3919 patient datasets identified, 225 were eligible for inclusion in the
curative, and 238 in the palliative, cohort. Exclusions were due to ineligible
histology or stage or missing dose, tumour volume or survival data. The DSS
successfully predicted a good prognosis group in the curative cohort with
significantly higher survival than a medium/poor prognosis group (S2Y, 69%
vs. 27/30%, p<0.001). No survival difference was found for palliatively
treated patients (S2Y good/medium/poor prognosis group: 18%/16%/16%).
Stage was less discriminatory in identifying prognostic groups (S2Y 47% for
Stage I-II; 36% for Stage IIIA-IIIB, p¼0.061) with most good prognosis patients having higher stage disease. In the good prognosis group S2Y was 65%
in curatively and 18% in palliatively treated patients.
The rapid learning system was feasible to deploy in a routine clinical
environment and the quality of routinely collected clinical data (without
specific quality review) was sufficient to validate a DSS. Using patient and
tumour information, the DSS can identify prognostic groups, providing an
evidence-based potential to change clinical decisions. The approach is
extendable to other treatment sites (eg head-and-neck) and to more cancer
centres as the collaboration expands. The model predictions can be prospectively tested. The methods could potentially inform decisions between
treatment technologies and support ‘personalised medicine’ approaches.
CALCULATION OF BEAM QUALITY CORRECTION FACTORS FOR EBT3
RADIOCHROMIC FILM
M. La
rraga-Gutie
rrez a, b. a Departamento de Física, Univerisidad
Jose
noma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco 186, Col.
Auto
Vicentina, Iztapalapa, C.P. 09340, M
exico, D.F., M
exico; b Laboratorio de
Física M
edica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes
sur 3877, Col. La Fama, Tlalpan, C.P. 14269, M
exico, D.F., M
exico
The new proposed formalism for the dosimetry of small and non-standard
fields (Alfonso et.al, 2008). requires the accurate Monte Carlo calculation of
beam quality correction factors (kQ) for a specific combination of radiation
detector and radiation source. The direct measurement of these correction
factors demands the use of a detector whose response is independent of the
radiation energy. The EBT radiochromic film family is a good candidate to
determine experimentally kQ values, because its components are tissue
equivalence (carbon, hydrogen, oxygen, etc.). However, a Monte Carlo analysis is required before establishing a methodology to measure kQ by using this
type of radiochromic film. The purpose of this work is to calculate kQ values
for the EBT3 radiochromic film by using Monte Carlo simulations. For that
purpose, a Monte Carlo model of a Novalis (BrainLab, Germany) linear
accelerator was carefully validated with measurements performed with
stereotactic diode (SFD, IBA-Dosimetry, Germany). The EBT3 radiochromic
film was modeled according with the manufacturer specifications (ISP Corp.,
USA). The absorbed dose to water and to the film active layer were calculated
by using the user code DOSRZnrc. The kQ values were determined for the
following square field sizes at 1.5 cm depth in water: 0.5, 1.0, 1.5, 2.0, 3.0 and
10.0 cm. It was found that the calculated kQ values lie between 0.991 and
1.007 with an overall statistical uncertainty of 1.3%. Comparing these results
with kQ of silicon diode and diamond detectors, it can be observed that the
response of the EBT3 film is energy independent within its statistical uncertainties for the field sizes and radiation source studied in this work. The
next step is to improve the uncertainties associated to radiochromic film
measurements and to validate this results experimentally. This work was
funded by the grant CONACYT-SALUD-2012-01-181822.
delivery. One important benefit of the introduction of IGRT in the clinic has
been the transition to Stereotactic Ablative radiotherapy (SABR-SBRT).
Typically, the coverage of the IGRT/SABR has been for a single-technology
and comparison between various single vendor technologies, for example,
MVCBCT by Siemens, against kVCBCT by Elekta and Varian or MVCT by
Tomotherapy. The clinical reality many times is far from single-vendor
technology. Many medium and small size clinics upgrade their delivery
systems (linacs) for IGRT and SABR by add-ons coming from multiple
vendors1. As an example, a Siemens linac with Brainlab Exactrac IG system
and third party treatment planning system, all put together to provide
IGRT and SABR programs within the clinical environment. Users find
themselves in that case up against issues that are not necessarily
addressed by a didactic or training course like those offered by a closed
single-vendor IGRT/SBRT systems, common examples being: a Novalis TX
with i-plan or Tomotherapy or Cyberknife.
This presentation will outline the main issues and give a step-by-step
method for clinical implementation of all the components in order to
achieve the final goal.
1 http://vimeo.com/75802709
2 D. Mihailidis, J. Mallah, M. Plants, G. Kagadis. “Influence of MLC Width on
Intensity Modulated Plans” Med. Phys. 38, (2011) 3805.
IMPROVEMENT OF THE PENUMBRA FOR SMALL RADIOSURGICAL
FIELDS USING FLATTENING FILTER FREE LOW MEGAVOLTAGE BEAMS
Mehran Yarahmadi a, Hassan A. Nedaie b, Otto A. Sauer c. a Kurdistan
University of Medical Sciences, Sanandaj, Iran; b Tehran University of Medical
Sciences, Tehran, Iran; c Klinik und Poliklinik für Strahlentherapie, University
of Würzburg, Josef-Schneider-Straße 11, 97080 Würzburg, Germany
Background: In stereotactic radiosurgery, sharp beam edges have clear
advantages to spare normal tissues. In general, the dose gradient is a
limiting factor in minimizing dose to nearby critical structures for clinical
cases. Therefore the penumbral width should be diminished.
Methods: A Varian Clinac 2100 linear accelerator equipped with in-house
designed radiosurgical collimator was modeled using the EGSnrc/
BEAMnrc Monte Carlo code and compared with the measurements. The
0.015 cm3 PinPoint chamber was used to measure the 6 MV photon beam
characteristics and to validate Monte Carlo calculations. Additional to the
standard (STD) linac, a flattening filter free (FFF) linac was simulated.
Percent depth doses, beam profiles and output factors were calculated for
small field sizes with diameter of 5, 10, 20 and 30mm with DOSXYZnrc. The
mean energy and photon fluence at the water surface were calculated
withBEAMDPfor both FFF linac and STD linacs.
Results: The penumbra width (80%-20%) was decreased by 0.5, 0.3, 0.2 and
0.2mm for field sizes of 5, 10, 20 and 30mm respectively when removing the
FF. The fluence of photons at the surface increased up to 3.6 times and the
mean energy decreased by a factor of 0.69 when removing the FF. The
penumbra width (80%-20%) decreased by 17% when a 2MeVmonoenergetic
electron pencil beam incident on the target is used instead of 6.2 MeV.
Conclusions: It was found that the penumbra of small field sizes is decreased
by removing the FF. Likewise using low megavoltage photons reduced the
beam penumbra maintaining adequate penetration and skin sparing.
BENCHMARK EXPERIMENT TO VERIFY RADIATION TRANSPORT
CALCULATIONS FOR DOSIMETRY IN RADIATION THERAPY
CLINICAL DEVELOPMENT OF STEREOTACTIC ABLATIVE BODY
RADIOTHERAPY (SABR-SBRT) WITH NON-DEDICATED MULTIVENDOR
TECHNOLOGIES
F. Renner a, R.-P. Kapsch a, A. Schüller a, Ch. Makowski a.
Technische Bundesanstalt Braunschweig, Bundesallee
Braunschweig, Germany
Dimitris Mihailidis, Michael Harmon, Lewis Whaley, Lloyd Farinash, Brian
Plants, Prem Raja. Charleston Radiation Therapy and West Virginia University,
USA
Radiation transport calculations based on the Monte Carlo (MC) method are
regarded as the most accurate technique for solving complex problems of
radiation transport. Therefore, they have great potential to realise more exact
dose calculations for treatment planning in radiation therapy. However, there
is a lack of information on how correct the results of MC calculations are on an
absolute basis. A practical verification of the calculations can be performed by
direct comparison with a benchmark experiment also considering the related
uncertainties. At the national metrology institute of Germany, the Physikalisch-Technische Bundesanstalt (PTB), such a benchmark experiment was
performed. This experiment had parallels to clinical radiation therapy, among
Image guided stereotactic radiotherapy (IGRT) is a treatment modality that
combines a variety of new technologies from imaging, to treatment
planning and treatment delivery. It has been the primary method of
treatment for several cranial and extra cranial tumors, where accurate
patient immobilization and setup, tumor delineation, complex treatment
planning and pre-treatment imaging, are necessary for accurate treatment
a
Physikalisch100, 38116
Abstracts / Physica Medica 30S1 (2014)
19
IMPACT TO TOTAL SCATTER FACTORS OF THE DOSIMETER ON THE
CALCULATED DOSE DISTRIBUTION IN STEREOTACTIC RADIOSURGERY
Materials and Methods: PSM are derivative-free optimization algorithms
that require few function evaluations to progress and converge and have
the ability to better avoid local entrapment making them a suitable
approach for the resolution of the noncoplanar BAO problem. Locally
advanced head and neck clinical cases were selected to test this approach.
The planning target volumes included the primary tumor, the high and low
risk lymphnodes. Organs-at-risk included the parotids, the brainstem, and
the spinal cord. For each case, a setup with five equidistant beams was
chosen and the resulting treatment plan using a multicriteria optimization
approach was then compared with the coplanar and noncoplanar plans
using the optimal beam setup obtained by PSM.
Results: For the clinical cases retrospectively tested, the use of noncoplanar directions in our tailored approach showed a positive influence on
the quality of the solution found. For the same target coverage, the
noncoplanar treatment plans obtained an average reduction of the parotid's mean dose irradiation in 4.2 Gy compared to the equidistant
treatment plans while the coplanar treatment plans only obtained a 2.7 Gy
average decrease.
Conclusions: PSM has shown ability to avoid local entrapment and efficiency on the number of function evaluations even using noncoplanar
directions, which is a major advantage compared to other global heuristics
where the continuous solution space is confined to a discrete subset, often
only considering coplanar irradiation angles to achieve clinically acceptable computation times.
rraga-Gutie
rrez a. a Laboratorio de Física
~ o a, J.M. La
O.A. García-Gardun
Medica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur
3877, C.P. 14269, M
exico, D.F., M
exico
DOSIMETRIC ANALYSIS OF PATIENTS WITH IMPLANTED CARDIAC
DEVICES UNDERGOING RADIOTHERAPY. ADDITIONAL PROPOSED
PRECAUTIONS TO THE LAST UPDATED GUIDELINES
Physical and technical challenges exist in the dosimetry of small-fields
which are wide highlighted in the literature. However, the literature did
not report the impact of the dosimeter in the calculated dose distribution.
The goal of this work was to assess the impact of relative measurements of:
off axis ratios, tissue maximum ratios and especially total scatter factor
(TSF) on the calculated dose distribution. Six detectors were employed to
characterize circular collimated beams generated with a dedicated linear
accelerator: three diodes, one ionization chamber and two radiochromic
films. The relative measurements were incorporated in the treatment
planning system (TPS) in order to compare and analyze the calculated dose
distributions (DD). The major discrepancies were in the TSF that showed
that all the radiation detectors had a good agreement within their statistical uncertainties with the exception of the CC01 and EBT2 film. The
calculated DD were normalized with respect to the TSF and analyzed by
gamma index test by using a different calculation grid size. The DD did not
show any important difference when a gamma criteria of 3/3% was used.
According with the results presented in this work, we consider that all
detectors were excellent for the relative dosimetry of small photon beams
for plan evaluation. But it is necessary to consider the TSF, because the later
is involved in the calculation of the monitor units which is not reflected on
the calculated dose distribution by TPS and may impact the delivered dose
to the patient.
pez
Guadalupe Martín Martín a, Rocío Bermudez Luna a, Alfonso Lo
sar Rodríguez Rodríguez a, Mª Victoria de Torres
ndez a, Ce
Ferna
Olombrada b. a Medical Physics Department. Radiation Therapy Service.
Hospital Universitario de Fuenlabrada, Madrid (Spain); b Radiation
Oncology Department. . Radiation Therapy Service. Hospital Universitario
de Fuenlabrada, Madrid (Spain)
other things, with respect to the radiation applied, the materials used and the
manner of dose detection. The result of the experiment was a mean absorbed
dose per incident particle which could be compared to the result of an MC
calculation on an absolute basis. A special radiation source is necessary to
evaluate the mean absorbed dose per incident particle in an experiment,
since the number of source particles is usually not known for radiation
sources. An accurate characterisation of the source is also important to define
a realistic radiation source for the calculation. A radiation source which meets
these requirements is operated by PTB. The experimental part of the beamline at PTB‘s research linear accelerator is equipped with several devices for
the characterisation of the electron beam. There are beam current monitors
to evaluate the number of electrons, a magnetic spectrometer to obtain information on the spectral fluence of the electron beam and beam profile
monitors to measure geometric characteristics of the beam.
The benchmark experiment was modelled in a widely used MC software
tool for radiation transport calculations, too. A good agreement was found
for the result of the benchmark experiment and the corresponding result
of the MC calculation. The related uncertainties were less than 1 % in both
cases. The results of the work exemplify evidence of the absolute correctness of dosimetric quantities calculated with the MC method in the
application field of radiation therapy.
NONCOPLANAR BEAM ANGLE OPTIMIZATION IN IMRT TREATMENT
PLANNING USING DERIVATIVE-FREE ALGORITHMS
H. Rocha a, J. Dias b, B. Ferreira c, M.C. Lopes d. a INESC-Coimbra, Coimbra,
Portugal; b FEUC, Coimbra, Portugal; c I3N, Aveiro, Portugal;; d IPOC-FG EPE,
Coimbra, Portugal
Purpose/Objective: The planning of radiation therapy treatments requires
decisions regarding the angles used for radiation incidence. The beam
angle optimization (BAO) problem consists in finding the optimal number
and incidence directions of the irradiation beams. The selection of
appropriate radiation incidence directions is important for the quality of
the treatment. However, the possibility of improving the quality of treatment plans by an optimized selection of the beam incidences is seldom
done in clinical practice. Adding the possibility for noncoplanar incidences
is even more rarely used. Nevertheless, the advantage of noncoplanar
beams is well known. We present the benefits of using pattern search
methods (PSM) for the optimization of the highly non-convex noncoplanar
BAO problem.
Aims: There is few literature available regarding radiotherapy in patients
with Cardiac Implantable Electronic Devices (CIEDs). Official guidelines
have not been updated since 1994 and CIEDs manufacturing technology, as
well as radiotherapy techniques, have considerably changed since then. An
updated practical guideline was developed in The Netherlands to take
these changes and the patient’s perspective into account (1). The aims of
this work are to describe the implementation of this new protocol in our
Institution, and to propose additional precautions regarding some imaging
techniques not described in detail within this guideline.
Materials and methods: Between 2013 and 2014, fifteen patients with
CIEDs of different primary sites were treated in our institution. A treatment
plan optimally covering the target area and maximally sparing the CIED
was generated for all patients. Dose to the CIED was assessed and patients
were classified according to their risk as recommended by the Dutch
guideline. Patients were evaluated before, during and after radiotherapy
by a cardiologist.
Results: Our patient focus group consisted of 7, 7 and 1 patients categorised into low, medium and high risk groups, respectively. The median
age was 71 (range 54-91) years. There were five men with head and neck
primaries, three men with lung primaries, 5 men with pelvic primaries and
two women with breast primaries. The prescribed dose ranged from 20 to
78 Gy with a daily dose ranging from 1.8 to 4 Gy. The maximum doses to
the CEIDs were 179.1 cGy, 751 cGy and 1270 cGy, for the low, medium and
high risk groups, respectively. Radiation therapy was safely delivered in all
patients, but in two of them we experienced a CIED malfunction (without
any untoward effects for the patients' health), while Cone-Beam acquisition previous to the treatment was taking place.
Conclusion: Radiotherapy was safely delivered in a series of fifteen patients
with CIEDs following the recommendations of the Netherlands task group.
However, we included some additional precautions related to 3D imaging
acquisition techniques which are not described in detail in their guideline.
References
(1) Management of radiation oncology patients with a pacemaker or ICD: a
new comprehensive practical guideline in The Netherlands. Dutch Society
of Radiotherapy and Oncology (NVRO). Radiat Oncol. 2012 Nov 24;7:198.
20
Abstracts / Physica Medica 30S1 (2014)
IN VIVO DOSE VERIFICATION OF 3D CONFORMAL TREATMENTS WITH
THE USE OF AN A-SI EPID
ENERGY DEPENDENCE OF PTW MICRODIAMOND DETECTOR IN
RADIOTHERAPY PHOTON AND ELECTRON BEAMS
P. Mandourari, C. Antypas, C. Armpilia, J. Floros, P. Sandilos. Medical Physics
Unit, 1st Department of Radiology, Aretaieion Hospital, University of
Athens,Vas. Sophias 76, 115 27 Athens, Greece
M. Pimpinella a, A. Stravato a, A.S. Guerra a, V. De Coste a, M. Marinelli b, G.
Verona-Rinati b, M.D. Falco c. a ENEA-INMRI, Istituto Nazionale di Metrologia
di Roma Tor
delle Radiazioni Ionizzanti, Roma, Italy; b INFN - Universita
Vergata, Dipartimento di Ingegneria Industriale, Roma, Italy; c Tor Vergata
University General Hospital, Department of Diagnostic Imaging Molecular
Imaging Interventional Radiology and Radiotherapy, Roma, Italy
Background: The aim of this work is to propose an easily applicable in vivo
verification method using an a-Si flat panel.
Materials and Methods: The dosimetric characteristics of the EPID
were determined. The methodology to calculate the dose along the
central axis of the photon beam in a homogeneous phantom or a
patient is described. The method was validated with point dose
measurements in a homogeneous solid water phantom of various
thicknesses using an ionization chamber. Once the method was
validated in the phantom, it was applied on ten prostate patients
with 3D conformal treatment plans. The EPID in vivo reconstructed
doses were compared to the doses given by the treatment planning
system (TPS).
Results: The phantom validation measurements revealed very good
agreement between EPID reconstructed mid-plane doses and ionization
chamber measured mid-plane doses (mean error¼-1.7%, min¼-2.9%,
max¼1.1%). In vivo measurements in prostate patients revealed very good
agreement between EPID reconstructed mid-plane doses and treatment
planning calculated mid-plane doses (mean error¼0.85%, min¼-3.66%,
max¼6.59%).
Discussion: All the results are less than 5% which is the tolerance level in
classic in vivo dosimetry. Therefore, the presented EPID dosimetry method
is accurate. It can be applied easily to all types of flat panels without the
use of any sophisticated software. Furthermore, it is contactless and the
EPID images are in disposition immediately after patient irradiation. The
proposed method use of EPID dosimetry is intended to be used in more
complex treatment techniques.
IN VIVO DOSE VERIFICATION OF 3D CONFORMAL TREATMENTS WITH
THE USE OF RADIOCHROMIC EBT2 FILMS
P. Mandourari, C. Antypas, C. Armpilia, J. Floros, M. Rouchota, P.
Sandilos. Medical Physics Unit, 1st Department of Radiology, Aretaieion
Hospital, University of Athens Vas. Sophias 76, 115 27 Athens, Greece
Background: The aim of this work is to propose an easily applicable in vivo
verification method using radiochromic EBT2 films.
Materials and Methods: Radiochromic EBT2 films were evaluated for in
vivo dosimetry of 3D conformal treatments. The EBT2 film calibration was
determined in the dose range of 20cGy e 500cGy. The ESTRO recommendations for in vivo dosimetry were used to calculate the midplane
dose inside a phantom or a patient. The method was validated in a homogeneous solid water phantom of various thicknesses along the central
axis of the photon beam at the midplane depth using an ionization
chamber. After validation, the method was applied on ten prostate patients treated with 3D conformal plans. In vivo EBT2 reconstructed doses
were compared to the doses calculated by the treatment planning system
(TPS).
Results: The phantom validation measurements revealed very good
agreement between EBT2 reconstructed mid-plane doses and ionization
chamber measured mid-plane doses (mean error¼-3.8%, min¼-4.8%,
max¼-2.1%). In vivo measurements in prostate patients revealed very good
agreement between EBT2 reconstructed mid-plane doses and treatment
planning calculated mid-plane doses (mean error¼-0.16%, min¼-1.67%,
max¼2.32%).
Discussion: All the results are less than 5% which is the tolerance level in
classic in vivo dosimetry. EBT2 radiochromic films can be accurately used
for in vivo dosimetry of prostate patients with 3D conformal plans. The
presented in vivo dosimetry with EBT2 radiochromic films is intended to
be used for validation of other dosimetry techniques in more complex
treatments.
Aim of this work is to investigate, by Monte Carlo simulations and by
experiment, the energy dependence of the new synthetic diamond detector, microDiamond type 60019 (PTW, Freiburg, Germany), in megavoltage photon and electron radiotherapy beams.
Monte Carlo simulations are performed using the EGSnrc software package. The microDiamond is modelled in detail according to the geometrical
and material data provided by the manufacturer. The detector irradiation
at the reference depth in a water phantom is simulated and the response in
terms of absorbed dose to water is determined as a function of beam
quality. The detector response is calculated as the ratio of absorbed dose in
the detector sensitive volume (about 0.004 mm3) to absorbed dose in the
same volume of water by means of the egs_chamber user-code included in
the EGSnrc package. Photon beams in the range from 6 MV to 15 MV
(TPR20,10 from 0.67 to 0.76) and electron beams from 6 MeV to 18 MeV (R50
from 2.6 to 8 g/cm2) are considered.
Measurements are performed in clinical photon and electron beams produced by an Elekta Precise linear accelerator. The accelerator output is
determined following the IAEA TRS 398 dosimetry protocol and using a
Farmer-type ionization chamber in photon beams and a PTW Roos® planeparallel chamber in electron beams. Both ionization chambers are calibrated in terms of absorbed dose to water in a reference 60Co beam. The
ratios of diamond detector signal to the delivered absorbed dose to water
obtained in reference conditions are analysed to evaluate the microDiamond energy dependence.
Measurement results show that the diamond detector response per unit of
absorbed dose to water slightly increases (up to about 2%) from 60Co to
clinical beam qualities. Both Monte Carlo and experimental results indicate
that variations in the microDiamond response are within ±1% over the
beam quality range of accelerator beams considered in this work.
OUT-OF-FIELD DOSE MEASUREMENTS FOR RADIOTHERAPY OF BRAIN
TUMOURS IN PAEDIATRIC PATIENTS
L. Stolarczyk a, M. Majer b, N. Adamek c, E. Gora d, D. Kabat d, Z.
c b, R. Harrison e. a Institute of
Kne
zevi
c b, M. Liszka a, P. Olko a, S. Miljani
Nuclear Physics PAN, Radzikowskiego 152, 31-342 Krakow, Poland; b RuCer
Boskovic Institute, Bijenicka c. 54, 10 000 Zagreb, Croatia; c Faculty of
Physics and Applied Computer Science AGH, Krakow, Poland; d Maria
Sklodowska-Curie Memorial Institute of Oncology, Garncarska 11, 31 115
Krakow, Poland; e University of Newcastle upon Tyne, Newcastle, UK
It has been known for many years that out-of-field radiation doses to
normal tissues may be associated with an increased risk of secondary
cancers. Paediatric patients are of particular concern due to their possible
longer life expectancy and higher organ radiosensitivities compared with
adult patients and higher organ doses because of their smaller body size.
The motivation of EURADOS Working group 9 (WG 9) is to assess unwanted, non-target patient doses in radiotherapy.
The purpose of this phantom study was to measure out-of-field organ
doses using 5 and 10 year-old anthropomorphic phantoms for modern
techniques of radiotherapy. The treatment of a spherical brain tumor with
a diameter of 6 cm was simulated with 6 MV photon beams for Intensity
Modulated Radiotherapy (IMRT) and 3D Conformal Radiotherapy (3D
CRT). Radiophotoluminescent (RPL) and thermoluminescent (TL) dosimeters placed in 20 organs were used for dose measurements. For both
techniques organ doses decreased with distance from the target volume. 5
year-old phantom doses were on average 30% and 60% higher than doses
for the 10 year-old phantom for IMRT and 3D CRT respectively. For
example, for IMRT, doses measured with RPL dosimeters (Figure 1) ranged
Abstracts / Physica Medica 30S1 (2014)
from approximately 32% of the given tumor dose for eyes and dropped
rapidly to 0.3% for thyroid and to 0.02% for testes in the case of 10 year-old
phantom. For the 5 year-old phantom, doses ranged from approximately
43% of the given tumor dose for eyes and 0.4% for thyroid to 0.035% for
testes.
Radiation risks of cancer incidence for seven organs (thyroid, lung, breast,
liver, stomach, bladder and prostate) in the form of the lifetime attributable risk (LAR) were estimated using BEIR VII model. For IMRT, the highest
risk per single fraction (2 Gy in tumour) was estimated for 5 year-old girls
(50 and 34 cancers per 105 patients for breast and thyroid respectively).
The highest organ risk in the case of boys was for lungs (11 cancers per 105
5 year old patients).
21
The following dosimeters were used: thermoluminescent (TLD-700, MTS7, MTS-6 and MTS-N), radiophotoluminescent (GD-352M and GD302-M)
and CR-39 track detectors.
The results obtained within the irradiated volume show good agreement
between prescribed and measured dose with RPLs (94.6Gy ± 2.4%). In
Figure 1 preliminary results for TLDs and RPLs are shown for measurements outside the radiation field (beyond the range of proton beam). For
photons, doses decrease from 22 mGy and 18 mGy at distance aproximately 13 cm from the inner surface of phantom, to 1 mGy and 0.5 mGy at
distance aproximately 56 cm for MTS-7 and GD-352M respectively. Higher
doses for TLDs compared with RPLs are observed due to higher sensitivity
of TLDs to secondary neutrons in comparison to RPLs. A systematic
decrease of the geequivalent neutron dose (Dn) with distance is observed.
Dn is defined as the TL signal induced by neutrons in MTS-6 expressed in
terms of the g-ray dose producing an identical TL signal. Dn varied from
130 mGy at 13 cm from the inner surface of the phantom to 2 mGy at 56
cm. The detailed analysis of results combined with future Monte Carlo
calculations will give valuable information about doses from scattered
radiation distant from the target volume.
Figure 1. Organ doses (per 2 Gy in target volume) for IMRT measured with RPLsĂ
COMPARISON OF PASSIVE DOSIMETERS FOR SECONDARY RADIATION
MEASUREMENTS IN SCANNING PROTON RADIOTHERAPY
Kne
zevi
c b, N. Adamek c, C. Algranati d, I. Ambrozova e, C.
L. Stolarczyk a, Z.
Domingo f, V. Dufek g, J. Farah h, F. Fellin d, M. Klodowska a, J. Kubancak e, M.
c b, O. Ploc e, M. RomeroLiszka a, M. Majer b, V. Mares i, S. Miljani
sito f, K. Schinner i, M. Schwarz d, S. Trinkl i, F. Trompier h, M.
Expo
Wielunski i, R. Harrison j, P. Olko a. a Institute of Nuclear Physics PAN,
Radzikowskiego 152, 31-342 Krakow, Poland; b RuCer Boskovic Institute,
Bijenicka c. 54, 10000 Zagreb, Croatia; c Faculty of Physics and Applied
Computer Science AGH, Krakow, Poland; d Medical Physics Department,
Trento Proton Therapy Center, Via Al Desert 14, 38123 Trento, Italy;
e
Department of Radiation Dosimetry, Nuclear Physics Institute, CZ-250 68
z, Czech Republic; f Departament de Física, Universitat Auto
noma de
Re
Barcelona, E-08193 Bellaterra, Spain; g National Radiation Protection
Institute, Bartoskova 28, 140 00 Prague, Czech Republic; h Institute for
Radiological Protection and Nuclear Safety, Human Health Division, BP17,
92260 Fontenay-aux-Roses; France; i Helmholtz Zentrum München,
€dter Landstraße 1, 85764
Institute of Radiation Protection, Ingolsta
Neuherberg, Germany; j University of Newcastle upon Tyne, Tyne and Wear
NE1 7RU, Newcastle upon Tyne, United Kingdom
Proton therapy is used increasingly in cancer treatment because of the
possibility of sparing healthy tissue close to the target volume. However,
the interactions of protons with matter result in the production of secondary radiation comprised mostly of neutrons and gamma radiation.
Unwanted doses, deposited distantly from the target volume, may lead to
an increasing probability of late effects of radiotherapy including the
generation of secondary cancers.
The EURADOS WG9 measurement campaign is designed to investigate the
secondary radiation generated by a scanning proton beam. Experiments
were carried out in the IBA (230 MeV) active-scanning proton beam
therapy facility in Trento, Italy. A volume of 10 x 10 x 10 cm3 inside the
water phantom (60 x 30 x 30 cm3) was irradiated uniformly to a dose of
100 Gy. Depth dose distributions along the beam axis and profiles at
various depths were measured.
Fig 1. The decrease of secondary radiation doses with lateral distance from the field
edge (at 18.5 cm from the inner surface of the phantom) measured with different
passive dosimeters in water phantom.
A COMPARISON OF DOSIMETRIC PROPERTIES OF THREE SOLID STATE
DOSIMETRY SYSTEMS FOR DOSIMETRY AUDIT IN RADIOTHERAPY
P. Grochowska a, J. Izewska a, H. Mizuno a, J.F. Aguirre b, G. Azangwe a, P.
Bera a, A. Meghzifene a. a International Atomic Energy Agency, Dosimetry
and Medical Radiation Physics Section, Vienna, Austria; b U.T.M.D. Anderson
Cancer Center, Radiation Physics, Houston, USA
Background: The purpose of this study is to investigate and compare
characteristics of three solid state dosimetry systems in order to determine
working parameters and corrections needed for remote dosimetry audits
of high energy photon and electron beams. The following systems were
investigated: a thermo luminescent dosimetry (TLD) system (TLD-100,
PCL3 reader), an optically stimulated luminescent dosimetry (OSLD) system (nanoDots, microStar reader) and a radiophoto luminescent dosimetry
(RPLD) system (GD 302M, FGD-1000 reader).
Materials and Methods: Prior to performing tests, the read-out procedure
for each dosimetry system was optimized to achieve the best reproducibility of the measured signal. For OSLDs and RPLDs corrections for
sensitivity of individual dosimeters were determined. Numerous tests
were performed in order to describe the dosimetric characteristics:
reproducibility, signal depletion (RPLD, OSLD), dose response non-linearity, fading effect and energy dependence.
Results: All three systems tested show adequate reproducibility of about
1% for a group of dosimeters irradiated and read several times. Signal loss
for OSLDs and RPLDs during repeatable read-out is minimal and can be
neglected during the standard reading procedure. Correction for dose
response non-linearity is needed in 1.5 e 2.5 Gy range for OSLDs and TLDs,
22
Abstracts / Physica Medica 30S1 (2014)
whereas for RPLDs the response is linear with dose. Fading effect was
checked and results show that for TLDs and OSLDs signal stabilizes in
around 10 and 2 days after irradiation, respectively. For RPLDs, when the
preheating treatment is applied, the signal stabilizes and there is no
further change. Energy corrections for a range of photon beams (6 - 18 MV)
and electron beams (6 - 20 MeV) relative to a Co-60 beam, are of the order
of 3- 5% for all three detectors for highest beam energies.
Discussion: All three systems, especially TLD and RPLD systems need very
careful handling procedures in order to achieve good reproducibility. The
advantage of RPLDs and OSLDs is that the reading process can be repeated
if necessary. RPLD does not need a non-linearity and fading corrections.
Assuming that all corrections are properly applied, all three systems can be
used for dosimetry audit in radiotherapy.
DOSE CALCULATION ACCURACY AT PRESENCE OF DENTAL IMPLANTS ON
UNCORRECTED AND METAL ARTIFACT REDUCED COMPUTED
TOMOGRAPHY DATA
Manuel Maerz, Pia Mittermair, Oliver Koelbl, Barbara Dobler. Department
of Radiotherapy, RegensburgUniversity Medical Center, Germany
Background: Dose calculation in modern treatment planning is based on
Computed Tomography (CT) data of the patient. Metallic dental implants
cause severe streaking artifacts, which inhibit the correct representation of
shape and density of the metal and the surrounding tissue.We will present
the influence of dental implants, metal artifacts and the benefit of the
metal artifact reduction algorithm IFS (iterative frequency split) on dose
calculation accuracy depending on treatment technique and dose calculation algorithm.
Materials and Methods: The study is conducted on cylindrical phantoms
consisting of water equivalent material surrounding dental implant materialand other heterogeneities (e.g. air, muscle) in various geometric arrangements. Computed Tomography images of the phantoms are generated
and corrected using the IFS algorithm. Several plans are irradiated to the
phantoms equipped with Gafchromic EBT 3 films: five beams IMRT (Intensity Modulated Radiation Therapy), nine beams IMRT und dual arc VMAT
(Volumetric Modulated Arc Therapy). The measured dose distributions are
compared to calculations on corrected and uncorrected CT data using the
dose calculation algorithms Pencil Beam and Collapsed Cone, implemented
in Oncentra External Beam v.4.3 and the Monte Carlo simulation XVMC. The
Pencil Beam and XVMC algorithms report dose to water, whereas Collapsed
Cone reports dose to media. To compare film measurements to Collapsed
Cone calculations the film measurements which are calibrated to dose to
water are rescaled to dose to media. Inaccuracies caused by artifacts or not
adequately corrected CT images and inaccuracies caused by incorrect
modeled transmission of radiation through metal implants are separated.
Results: Depending on the dose calculation algorithm and the treatment
technique artifacts lead to inaccuracies in dose calculation that can be
reduced by application of the IFS algorithms. The accuracy of the calculation on the IFS corrected data and the improvement with respect to the
uncorrected data depends on the dose calculation algorithm and the
composition of material in the phantom.
Conclusion: Metal artifact reduction leads to an improvement in accuracy
of dose calculations. The application of a metal artifact reduction algorithm
is recommended to reduce dose uncertainties.
Acknowledgments:The work was supported by the Wilhelm Sander
Foundation.
TEST, VALIDATION AND UPGRADE OF THE MD ANDERSON ANALYTICAL
MODEL PREDICTING SECONDARY NEUTRON RADIATION IN PROTON
THERAPY FACILITIES
rault c, F.
J. Farah a, A. Bonfrate a, A. De Oliveira b, S. Delacroix b, J. He
Martinetti a, S. Piau d, F. Trompier a, I. Vabre d, I. Clairand a. a Institute for
Radiological Protection and Nuclear Safety (IRSN), Human Health Division,
31 ave de la Division Leclerc, 92260 Fontenay-aux-Roses; France; b Institut
Curie e Centre de Protonth
erapie d’Orsay (ICPO), Campus universitaire
^timent 101, 91898 Orsay, France; c Centre Antoine Lacassagne (CAL) ba
Cyclotron biom
edical, 227 avenue de la Lanterne, 06200 Nice, France;
d
Institut de Physique Nucl
eaire d’Orsay (IPNO), Service de dosim
etrie,
^timent 104, 91406 Orsay, France
Campus universitaire ba
Purpose: This study follows the MD Anderson approach* to build an
analytical model predicting leakage neutrons within the local 75 MeV
ocular proton therapy facility. Its main goal is to test, validate and upgrade
the model to clinically relevant configurations.
Methods: Using Monte Carlo (MC) calculations, neutron ambient dose
equivalents, H*(10), were simulated at different positions inside the
treatment room while considering a closed final collimator and pristine
Bragg peak delivery as per the MD Anderson method. Using this data, a
facility specific analytical model was developed and tested. Starting from
H*(10) values at isocentre, this model attempts to reproduce the neutron
decrease with axial and lateral distance to isocentre while separately accounting for the contribution of intranuclear cascade, evaporation, epithermal and thermal neutrons. To validate the model, simulated H*(10)
values were considered as well as experimental measurements previously
unavailable at MD Anderson. The model was also expended in the vertical
direction to enable a full 3D mapping of H*(10) inside the treatment room.
Results: The work first proved that it is possible to build ones’ own
analytical model following the MD Anderson approach which however
requires a MC model of the local proton therapy facility. Validation showed
that the analytical model efficiently reproduced simulated H*(10) values
with a maximum difference below 10%. In addition, it succeeded in predicting measured H*(10) values with differences <40%. The highest differences were found at the closest and farthest positions from isocenter
where the analytical model failed to faithfully reproduce the high variations in neutron fluence and energy. The differences remain however
acceptable when taking into account the non negligible measurement/
simulation uncertainties and considering the end use of this model, i.e.
radiation protection. Finally, the model was successfully extended to predict neutrons in the vertical direction with respect to the beam line as
patients are in the upright seated position during ocular treatments (differences <20% on simulations and <45% on measurements).
Conclusion: Analytical models represent a promising solution that substitutes for time-consuming MC calculations. Further studies remain
necessary to upgrade the model and account for beam modulation, collimation and patient-induced neutron fluctuations.
rez-Andújar A, Zhang R and Newhauser W. Monte Carlo and analytical
*Pe
model predictions of leakage neutron exposures from passively scattered
proton therapy. Med. Phys. 40, 1714-25 (2013)
DOSE PERTURBATION CLOSE TO HIGH Z MATERIALS IN MV FIELDS
John Kalef-Ezra, Konstantina Karava. Medical
University of Ioannina, Ioannina 45110, Greece
Physics
Department,
Background: Inhomegeneities in the human body result in electron
disequilibrium close to the interfaces. The purpose of this study was the
assessment of the dose perturbation in tissues of low atomic number, Z,
before an interface with a high Z / high density medium during irradiations
with MV beams.
Methods and Materials: Dose measurements in PMMA were carried out
using H810 and MD-55 radiochromic films close to aluminum, copper and
lead interfaces irradiated with either 60Co gamma rays or 6 MV X-rays.
Results: The dose enhancement in PMMA due to the presence of the high Z
inhomogeneity increases with increasing Z of the inhomogeneity (~Z1/2)
and its thickness up to an energy-dependent saturation thickness and
decreases with increasing distance from the interface. For example 17%,
37% and 109% dose increases were found at 4 mm distance from adequately
thick Al, Cu and Pb layers irradiated with 6 MV X-rays, dropping to about
5%, 6% and 7% at 7 mm distance, respectively. Higher dose increases were
found at the 4 mm distance from the interfaces of the three media irradiated with 60Co beams, 23%, 56% and 138%, respectively, dropping to 2%, 5%
and 9% at 2.3 mm distance from the interface. On the other hand, the dose
enhancement decreases with increasing irradiation angle. Both the field
size and the depth of the inhomogeneity (studied only at depths larger
than the one that corresponds to the maximum build-up) have marginal
effect on the dose perturbation in radiation fields of large size. Empirical
equations were derived, which correlate with the irradiation conditions
the dose perturbation in soft tissues at short distances from high Z inhomogeneities, such as cortical bone, implanted devices and contrast
media.
Abstracts / Physica Medica 30S1 (2014)
Conclusions: The empirically obtained equations could improve dose
assessment in low Z tissues close to high Z media present in the patient’s
body.
TOTAL SKIN ELECTRON BEAM IRRADIATION IN GREECE: IN-VIVO
DOSIMETRY
Patatoukas George a, Dilvoi Maria a, Diamantopoulos Stefanos b, Platoni
Kalliopi a, Kouloulias Vassilios c, Georgakopoulos Ioannis c, Tsioumas
Ioannis c, Efstathopoulos Efstathios a. a Medical Physics Unit, 2nd
Department of Radiology, Medical School, University of Athens, Greece;
b
Medical Physics Department, Radiation Oncology Division, ‘Metropolitan’
Hospital, Neo Faliro, Piraeus, Greece; c Radiation Therapy Unit, 2nd
Department of Radiology, Medical School, University of Athens, Greece
Background: Total Skin Electron Beam (TSEB) irradiation is considered as
the treatment of choice for cutaneous T-cell lymphoma internationally, for
either curative purposes or palliative care. The application of this external
radiation therapy technique in Greece takes place at the Radiation Therapy
Unit of the 2nd Department of Radiology of University of Athens at University General Hospital ”Attikon”, from 2011. So far, nine patients have
received therapy, using the ”Six-dual-field” technique adopted by our
department. In this work we present and analyze the first set of the in-vivo
dosimetric results.
Materials and Methods: TSEB therapy was developed on a linear accelerator VARIAN Clinac 2100C, to create a uniform and sufficiently large field
(z200 cm 80 cm) at SSD¼380 cm, two symmetrical 6 MeV electron
beams are combined with 17.5 tilts concerning the horizontal direction.
An immobilization system was constructed to support patient during
treatment and to modulate the composite electron field. Irradiation procedure demands a standing patient that takes, in total, six treatment positions. In accordance to our protocol procedure, for each patient a number
of TLDs were positioned at various points on the patient’s skin by the
medical physics team, in order to measure, calculate and verify the
absorbed dose at specifically selected points which appear to be relevant
with the overall dose distribution. Mean, maximum and minimum patient
skin dose was calculated and recorded for each patient
Results: Patient dosimetry showed a very good agreement eon averagewith the expected mean dose of 2 Gy as mean patient dose. Furthermore,
minimum and maximum values were at the level of 1.4 and 3.3 Gy. Spatial
variations of the dose distribution can provide essential insights on the
patient irradiation conditions and can assist vitally in the dosimetric
optimization of the applied clinical protocol.
Discussion: The above results lead us to conclude that TSEB treatment
using ”Six-dual-field” technique has been implement with safety and
successfully in our department’s clinical therapeutic protocol.
COMPARISON OF TANGENTIAL FIELDS WITH AND WITHOUT WEDGE IN
WHOLE BREAST 3D CONFORMAL RADIOTHERAPY
M. Chatzimarkou a, A. Makridou a, I. Grigoriadis a, E. Kamperis b, K.
Mponiou b, M. Kotzasarlidou a, M. Charalambidou b. a Medical Physics
Department, Theagenio Cancer Hospital, Greece; b Radiation Oncology
Department, Theagenio Cancer Hospital, Greece
Background: To compare two distinct treatment planning methods in
breast cancer patients in the context of 3D conformal radiotherapy. The
competing methods consisted of two 6MV tangential fields with or
without wedges (max wedge factor: 0.3), supplanted in both cases by one
to three 15MV fields-in-a-field (FIFs).
Materials and methods: In total, 60 radiotherapy plans were designed, two
for each of the 30 patients. Dose distribution calculation was performed
with the analytical anisotropic algorithm (version 8917) in Eclipse TPS.
Dose was adjusted so that both plans shared the same maximum which
did not exceed 107% of the prescribed dose. The dosimetric constraints to
surrounding organs at risk were consistently respected. The optimization
of each plan was left to medical physicist’s discretion. Treatment was
performed in an Elekta SL15 equipped with MLC with a 60o universal
wedge and a nominal dose rate 400MU/min. Statistical analysis was done
with SPSS 20. A general linear model was utilized to analyze the variance
23
between the different techniques. Mean dose(%), minimum dose(%),
duration of treatment session and count of MUs comprised the measure
factors, while age, cancer site (right-left), T stage in TNM staging system
and CTV were covariates in our model.
Results: Analysis revealed a statistically significant difference across all
measured factors between the two groups, except for minimum dose. In
non-wedged plans mean dose was increased by 0.57% (0.38-0.76%,
p<0.001), duration of treatment was reduced by 45 seconds (42-48,
p<0.001) and MUs by 143 (131-154, p<0.001) corresponding to 22 seconds
reduction of beam-on time. There was a trend (p¼0.07) towards less
pronounced differences between the two methods with increasing CTV.
Discussion: The use of FIFs instead of wedges in breast 3D-CRT plans was
marginally better in terms of mean dose, while significantly reduced
treatment time and MUs in our case (Elekta SL15, universal wedge).
Considering the ramifications in radiation protection, such as less radiation
leakage, less beam-on time, less overall treatment time, along with the
reduced machine load and stress on replaceable components of the linear
accelerator (e.g., electron gun, magnetron, klystron, dose monitors), the
use of FIFs is a viable alternative to the current standard.
Keywords: Breast cancer, Radiotherapy, Linear accelerator, Radiation
protection.
QUALITY METRICS IN ELECTRONIC PORTAL IMAGING DEVICES
M. Tzomakas a, A. Episkopakis b, c, N. Kalyvas b, I. Kandarakis b, G.
Panayiotakis a. a Department of Medical Physics, School of Medicine,
University of Patras, Patras 26500, Greece; b Department of Biomedical
Engineering, Technological Educational Institution of Athens, Agiou
Spyridonos, 122 10, Egaleo, Athens, Greece; c ELEKTA, Agiou Konstantinou
17 , P.C. 15124 Amarousio, Attikis
Background: Earlier investigations on EPID image quality evaluation have
published data on quality metrics such as MTF, DQE , CNR and SNR.
However in these studies the effect of different energy was not systematically estimated.
Objective: In this work various image quality metrics were experimentally
estimated in order to assess the quality of images obtained in Electronic
Portal Imaging Devices (EPID) at different energies, and various values of
monitor units(MU) and dose rates.
Materials & Methods: A large number of images of the QC3 test phantom
were obtained and evaluated for different LINAC (Elekta iViewGT) energies, MUs and dose rates in order to calculate and extract graphs, using
MATLAB programming, of Modulation Transfer Function (MTF), Noise
Power Spectrum (NPS), Normalised Noise Power Spectrum (NNPS), Detective Quantum Efficiency (DQE), Contrast to Noise Ratio (CNR) and Signal
to Noise Ratio (SNR). MTF estimation was based on the Square Wave
method using the corresponding region of the phantom.
Results: MTF curves were found to be only slightly affected by energy and
dose rate, being slightly better at higher dose rates and higher energy. Both
NNPS and NPS graphs were found with irregular shape at low MUs and
energies and smoother at higher both MUs and energies. The DQE graphs
had little differences among the two energies and MUs. On the other hand
both CNR and SNR curves were clearly higher at 6 MV and lower at 18 MV.
Conclusion: It was found that the spatial frequency dependent metrics
(MTF, DQE), which are related to detector performance, showed a tendency
to increase when the energy, the dose rate and MUs were increased.
However, the contrast to noise ratio was found considerably lower at high
energy.
EVALUATION OF A NOVEL SYNTHETIC SINGLE CRYSTAL DIAMOND
DEVICE FOR IN-VIVO DOSIMETRY
Marco Marinelli a, F. Pompili a, G. Prestopino a, G. Verona-Rinati a, M.D.
Falco b, M. Pimpinella c. a INFNeDipartimento di Ingegneria Industriale,
di Roma ‘Tor Vergata’, Italy; b Tor Vergata University General
Universita
Hospital, Viale Oxford 81, 00133 Rome, Italy; c ENEA-INMRI, Istituto
Nazionale di Metrologia delle Radiazioni Ionizzanti, Roma, Italy
Background: In-vivo dosimetry (IVD) has been widely recognized as an
essential quality assurance (QA) instrument to be promoted in all
24
Abstracts / Physica Medica 30S1 (2014)
radiotherapy departments to detect errors in dose delivery and to provide
an overall check of the whole dosimetry procedure and patient setup.
Moreover, in several European countries IVD has become mandatory. A
variety of detectors, including thermoluminescent dosimeters (TLD), silicon diodes and metal oxide silicon field-effect transistors (MOSFETs) are
currently available for in-vivo dosimetry. These dosimeters are affected by
serious drawbacks, such as long readout time and signal fading (TLDs),
strong temperature, angular, dose and dose rate dependence, lack of radiation hardness, energy dependence (diodes and MOSFETs).
Materials and Methods: A novel detector based on a synthetic single
crystal diamond was evaluated for in-vivo dosimetry application. The
device prototype was designed as a cable-free portable dosimeter to be
operated offline. A basic dosimetric characterization was performed under
irradiation with a Co-60 reference gamma beam and a 6 MV clinical
photon beam from an Elekta Precise linear accelerator. The main features
relevant to IVD application were investigated: preirradiation procedure
and repeatability, linearity with dose (0.2 to 7 Gy), dose rate dependence
(1 to 5 Gy/min), angular (0 to 360 ) and temperature dependence (20 to
40 C).
Results: A negligible preirradiation procedure was found, with a
maximum deviation form average reading below 1%. Deviations below
0.5% were found for linearity with dose and dose rate dependence analysis.
Fading effect was negligible, with a decrease of diamond detector response
below 3% for delays separating irradiation and readout up to 30 minutes. A
deviation of 4% of diamond response, measured in the Co-60 beam, between 0 and ±180 irradiation direction was found. Finally, a temperature
dependence of about 5% was measured in the investigated temperature
range.
Discussion: The tested diamond prototype showed good dosimetric features for off-line IVD applications. Such results, together with the high
radiation hardness of diamond and its tissue-equivalence, are very
promising for the realization of an energy independent high performance
diamond based in-vivo dosimeter.
A QA PROCEDURE FOR BRACHYTHERAPY TPS EMPLOYING MODEL
BASED DOSE CALCULATIONS, BASED ON MONTE CARLO SIMULATION
AND END USER ORIENTED TOOLS
V. Peppa, E. Pappas, E. Pantelis, P. Papagiannis. Medical Physics Laboratory,
Medical School, University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
Background: Model-based dose calculation algorithms (MBDCA) have
been recently introduced as an option besides TG43 in 192Ir HDR brachytherapy treatment planning systems (TPS). The complexity of these algorithms challenges quality assurance (QA) programs requiring verification
of dose delivery in patient-specific conditions. The aim of this study is to
develop a user oriented QA procedure for TPS employing MBDCAs.
Materials-Methods: Mathematical phantoms resembling patient geometries, as well as a computational model of a water sphere were constructed.
These virtual phantoms were converted to DICOM-CT image series to facilitate their import to two commercially available systems(BrachyVision
v.10.0.33 and OncentraBrachy v.4.4). HDR 192Ir sources were selected from
the TPS source libraries to perform treatment plans. A catheter with a single
source dwell position was located at the center of the water sphere, as well as
5 and 10 cm eccentrically. Two plans were created for patient phantoms, one
with a multiple source dwell configuration and one where this was replaced
by one dwell position at the centroid of the source distribution. In all cases,
dosimetric calculations were performed using the model based dose calculation algorithm of the TPS.
Monte Carlo (MC) simulation was performed to obtain reference dose
distributions using BrachyGuide, a brachytherapy dedicated software tool
prepared in-house for the automatic preparation of MCNP input files from
treatment plans exported in DICOM-RT format. A dedicated custom software suite was also used for the comparison of reference MC data and
corresponding TPS results in terms of colormap representation of percentage differences, Dose Volume Histograms and plan quality indices.
Results: Comparisons of MC and TPS results showed a good agreement in
the majority of points. Considerable differences were also observed and
explained by MBDCA assumptions and optimization settings. These results
have to be taken into account in MBDCA commissioning procedures.
Discussion: The QA procedure and software tools presented herein may
serve as a basis for developing future standards toward providing a quality
management of MBDCA-based treatment planning systems.
Acknowledgement: Research co-financed by the EU ESF and Greek national funds.NSRF operational Program “Education and Lifelong Learning
Investing in knowledge society”, Aristeia I
STEREOTACTIC FRAME INDUCED GEOMETRIC DISTORTIONS IN MR
IMAGES EMPLOYED IN GAMMA KNIFE RADIOSURGERY APPLICATIONS
E. Pappas a, A. Moutsatsos a, P. Karaiskos a, b, E. Pantelis a, E. Georgiou a, M.
Torrens b, I. Seimenis c. a Medical Physics Laboratory, Medical School,
University of Athens, 75 Mikras Asias, 11527 Athens, Greece; b Gamma Knife
Department, Hygeia Hospital, Kifisias Avenue and 4 Erythrou Stavrou,
Marousi, 15123 Athens, Greece; c Medical Physics Laboratory, Medical
School, Democritus University of Thrace, 2nd building of Preclinical Section,
University Campus, 68100 Alexandroupolis, Greece
Purpose: To asses geometric uncertainties present in MR images necessitated for target localization and delineation in Gamma Knife radiosurgery. Specifically, this work focuses on the geometric distortions
induced by eddy currents associated with the Ti-based Leksell stereotactic
frame used for patient immobilization.
Materials and Methods: A plexiglass phantom -recently developed by our
group- was utilized. It encompasses 947 3mm-diameter holes interspersed in
the 3D space which serve as control points for distortion detection and evaluation. Control point distribution pattern ensures that the entire stereotactic
space is monitored. The phantom accurately fits the Leksell localization box
and stereotactic frame, but can also be fixed without the latter. The reversed
read gradient technique, along with a reference CT scan, were employed to
evaluate geometric distortions in the phantom imaged at 1.5T with clinicallyused gradient echo pulse sequences (axial 3D-T1w and coronal balancedT2w). An in-house, semi-automatic MATLAB software was developed to assist
control point localization and distortion evaluation. Derived 2D distortion
maps were compared with corresponding ones deduced without the frame.
Results: MRI-related distortions without the presence of the frame were
limited to 1mm. Contrarily, severe frame-induced distortion was detected in
regions neighboring the frame base. In T1w images, this distortion exceeded
5mm in a 20mm radial distance from the frame. Distortion decreased rapidly
with the distance from the frame and obliterated at about 70mm. The control
point disposition was always directed towards the frame center and did not
change sign relatively to the read gradient polarity. Slightly larger distortion
was detected with the frequency encoding direction being perpendicular to
the most proximal side of the frame base. In coronal balanced-T2w images,
the frame evidently distorted the nearside fiducials.
Conclusion: Geometric inaccuracies induced by the Leksell stereotactic
frame should be considered in GK radiosurgery applications with targets
lying in the vicinity of the frame base. Total distortion inherent in MR
images might reach inacceptable levels in extracranial cases, such as cervical spine, head and neck tumours (applicable in Perfexion model), where
the target is close to the frame base.
SYNTHETIC SINGLE CRYSTAL DIAMOND DIODE INCLINICAL DOSIMETRY
OF HIGH DOSE PER PULSE ELECTRON BEAMS FOR INTRAOPERATIVE
RADIATION THERAPY (IORT)
Marco Marinelli a, G. Verona-Rinati a, M.D. Falco b, M. Pimpinella c, S. De
Stefano d, A. Ciccotelli d, G. Felici d, F. Marangoni d. a INFNeDepartment of
Industrial Engineering, University of Rome “Tor Vergata”, Italy; b Tor
Vergata University General Hospital, Roma, Italy; c ENEA-INMRI, Istituto
Nazionale di Metrologia delle Radiazioni Ionizzanti, Roma, Italy; d S.I.T. Sordina IORT Technologies spa, Italy
Background: Accurate clinical dosimetry of electron beams produced by
special linear accelerators dedicated to intraoperative radiation therapy (IORT)
is challenging due to the presence of very high dose per pulse (1-10 cGy per
pulse) with respect to conventional accelerators (<0.1 cGy per pulse). This high
dose rate can affect the dose determination by means of dosimeters currently
used for absolute and relative dosimetry (e.g. ionization chambers). In addition, due to the high dose gradients of electron beams, small volume dosimeters are needed. Recently, the PTW microDiamond type 60019 has been
Abstracts / Physica Medica 30S1 (2014)
proven to be a suitable device for a very wide radiation quality range such as
photons, electrons and protons both for small and large irradiation fields.
Materials and methods: In this work,a dosimetric characterization of a
microDiamond prototype was performed under irradiation by electron
beams produced by a Novac IORT accelerator (S.I.T. - Sordina IORT Technologies) in the 4 e 9 MeV energy range with dose rate from 1 to 8 cGy per
pulse. The device performances were analysed in terms of linearity of the
dose response, dose-per-pulse dependency, energy dependence, spatial
resolution and capability to measure output factors (OFs).
Results: A linear dose response, independent of dose per pulse was found.
Percentage depth dose curves were in agreement with the ones obtained
with a plane-parallel ionization chamber (PTW Advanced Markus chamber
34045) previously characterized for measurements in high dose per pulse
electron beams. From beam profile measurements, a spatial resolution
comparable to the one of a PTW silicon diode (Diode E 60017), was
observed. The tested device has shown negligible energy dependence and
good capability for accurate OFs determination.
Conclusions: The performed dosimetric tests evidenced that the synthetic
single crystal diamond diode is suitable for accurate relative dosimetry in
high dose per pulse IORT electron beams.
PLAN EVALUATION USING DOSE-VOLUME
TREATMENT OF LOCALLY ADVANCED NSCLC
METRICS
FOR
THE
A. Miliadou a, G. Koukourakis a, P. Georgolopoulou b, C. Tripolitis a,b, K.
Kourinou a,b, S. Betsou b. a Radiation Oncology Department, Greece; b Medical
Physics Department, “St. Savvas” G. Anticancer Hospital of Athens, Greece
Purpose: A major component of plan evaluation is the inspection of dosevolume metrics so that clinical parameters, including burden of organs at
risk (OAR) and fractionation scheme, can be determined. Sources of uncertainty for the dose-volume metrics calculated by the planning software
have been identified and determined to be software and user dependent.
In this work we investigate the magnitude of such uncertainties and their
clinical implications for the hypofractionated treatment of locally
advanced non small cell lung cancer (NSCLC).
Method: Using the dose-volume-histogram (DVH) calculation tool in the
department’s treatment planning system we examined the dose-volume
metrics in 3D treatment plans of 20 consecutive lung cancer patients.
Parameters influencing the uncertainty of metrics such as D 95% for PTV
coverage, Dmax for the spinal cord, V20 and V5 for lung, V60 and V55 for
the esophagus and V40 for the heart, were examined for the specific
treatment plans. The effect on spinal cord, heart, lungs and esophagus
was quantified.
Results: Delineation variability, dose algorithm and the dose grid used in
the calculation of the metrics have the largest effect on DVH uncertainty.
Uncertainties become more important with decreasing structure volume.
Isodose selection for prescription determination needs to take into account
the effect on OARs given the corresponding individual uncertainty of the
organ’s metrics. Intending for hypofractionated treatments, plan evaluation lead to determination of a fractional dose in the range 2 - 2.75 Gy.
Conclusions: Variations in structure delineation and dose calculation
parameters are major factors of DVH uncertainty and hence of dose-volume metrics used to evaluate, approve and prescribe a given treatment
plan. Including dose-volume metrics in plan evaluation is an essential step
for the safe implementation of hypofractionated radiotherapy in NSCLC.
EVALUATING THE ACCURACY OF VOLUMETRIC MODULATED ARC
THERAPY (VMAT) TREATMENTS DELIVERY
A. Scaggion, A. Negri, M. Paiusco, A. Roggio, M.A. Rossato, F.
Simonato. Medical Physics Department Istituto Oncologico Veneto IOV via
Gattamelata n.64 35128, Padova, Italy
Background: The delivery of a Volumetric Modulated Arc Therapy (VMAT)
is affected by both random and sistematic errors arising from the multileaf
collimator (MLC) system motion, the gantry rotation and dose delivery
unit operation. In this study accuracy and reproducibility of VMAT
25
treatments delivery are extensively investigated through the analysis of
both clinical cases and accademic tests.
Materials and methods: A large collection of Log files generated by a
Varian Unique Linac equipped with a 120-leaf (MLC) allowed to obtain an
accurate representation of the machine delivery and to perform a detailed
characterization of errors affecting it. Approximately 60 different clinical
plans, relative to different oncological disease, were chosen to represent
the working domain of the Linac. The relation between Linac delivery
conditions and delivery errors was explored using different complexity
metrics and defining a delivery error score.
Results: The Linac was found to be generally accurate with errors bounded
to 3-4% within the clinical domain of operation. The dose delivery unit was
found to err randomly, whereas the gantry rotation errors and the leaves
movement errors increase respectively with gantry acceleration and leaves
speed. The overall delivery error was estimated combining into a unique
percentage score, VMAT Delivery Error Score (VDES), the errors coming
from all the possible sources of error. The VDES is related to the complexity
degree of the planned VMAT treatments and changes with the region to be
treated. A list of academic test was performed to strongly stress the machine so to allow the investigation of the link between plan complexity and
delivery error. Only when the machine closely approaches its mechanical
limits errors may become so large to affect the accuracy of the treatment.
Discussion: A large set of VMAT treatment plan deliveries are investigated
and compared to verify the accuracy of a Unique Linac. Within the clinical
operational domain, Unique operations are shown to be highly reproducible and generally accurate. Attention must be posed when the machine approaches its mechanical limits, in those cases the delivery errors
may become significant.
FETAL DOSE MEASUREMENT ON A PREGNANT PATIENT UNDERGOING
SINGLE FRACTION CYBERKNIFE RADIOSURGERY
Christos Antypas a, Evaggelos Pantelis a, Liana Sideri a, Katerina
Leonidas
Lekas a,
Pantaleo
Romanelli b,
Argyris
Salvara a,
Tzouras a, Nikolaos Salvaras a. a Medical Physics Department, CyberKnife
and Tomotherapy Clinic, Iatropolis, Chalandri, Athens, Greece; b CyberKnife
Center, CDI, Milano, Italy
Background: Pregnancy during stereotactic radiosurgery treatments is
extremely rare in clinical practice. We present fetal dose measurements on
a pregnant patient during single fraction CyberKnife radiosurgery for a
grade III anaplastic glioma.
Materials and methods: A 26 year’s old woman in the 5th month of
pregnancy diagnosed with a grade III anaplastic glioma was presented in
our clinic for treatment operation. Taking into account the clinical situation
of the case (stage of pregnancy, tumor progression and time required for
conventional radiotherapy) it was decided the patient to be treated with
single fraction CyberKnife radiosurgery. The position of the embryo was
determined with ultrasound prior treatment. CT and MR images of the
patient were acquired and a treatment plan was created in the Multiplan
treatment planning system. Two fixed collimators were used (10mm,
15mm) to irradiate the tumor with 226 beams (151/10mm, 75/15mm) and
18086MUs (12085MU/10mm, 6001MU/15mm). A dose of 14Gy was prescribed at the 80% isodose line covering the 95% of the tumor (14859mm3).
Before delivery, the treatment was simulated in an anthropomorphic
phantom. Radiation dose to the embryo was estimated using EBT3 radiochromic films and a Farmer ionization chamber. Dose measurements were
made at a distance of 60cm from the tumor center and 3 different depths
below the phantom surface.
Results: EBT3 film measurements revealed fetal dose to be 4.4cGy at 4.5cm
depth, 2.8cGy at 10cm depth and 4.0cGy at 14cm depth. Point dose measurement with Farmer chamber at 4.5cm depth agreed very well with the
EBT3 measurement, measuring 4.4cGy at 4.5cm depth.
Discussion: It was concluded that the dose to be delivered to the
unshielded embryo during the single fraction radiosurgery treatment with
CyberKnife was less than 5cGy. According to our results, there was no risk
for any deterministic effect to the embryo while the radiogenic cancer risk
to the live-born embryo was less than 5% compared to the normal incidence. The treatment was finally delivered successfully and few moths
later the patient gave birth to a healthy child.
26
Abstracts / Physica Medica 30S1 (2014)
EVALUATION OF A PHANTOM RELATED GAMMA INDEX THRESHOLD
FOR VMAT QA
, M.
A. Negri, A. Scaggion, M.A. Rossato, D. Canonico, R. Zandona
Paiusco. Veneto Institute of Oncology IOV-IRCCS, Medical Physics
Department, Via Gattamelata 64, 35128 Padova, Italy
Background: VMAT pre-treatment QA are usually performed comparing
measured and calculated dose distribution in phantom by means of
gamma index (GI) metric. This procedure is based on the assumption that
the differences between measured and calculated dose distribution in any
phantom reflect those in patient. The aim of this study was to assess the
relation between gamma index passing rate (GP%) evaluated for different
phantoms geometry and patients. A phantom related GP% acceptance level
is established based on a new strategy that takes into account the acceptance level defined for patients
Materials and methods: 30 H&N cancer patient were selected. The data
contained in the MLC and the gantry log files provided by the Varian Linac
were used to create RTPLAN DICOM files simulating the delivered plan.
Mathematical phantoms were created reproducing geometries of the widely
available QA systems such as planar systems, cylindrical surface systems and
a3D cylindrical measurement systems. Both planned and delivered plans
dose distribution were calculated in patients and in phantoms. Mean GI and
GP% correlations between phantoms as well as between phantoms and
patients were investigated. ROC analysis was applied to define the GP%
thresholds for different phantoms based on the patients acceptance level.
Results: The study shows that the results of the gamma analysis strongly
depends on the geometry of the dosimeter used for the pre-treatment
verification. In case of planar geometries the inaccuracies detected with the
phantom do not absolutely reflect those occurring in patients. Moreover the
GI map changes with the measurements depth. Conversely, in volumetric
and cylindrical 2D geometry, the above mentioned correlations are fully
confirmed. Finally the ROC analysis showed that the GP% on different
phantom have a different meaning in term of dose differences on patient.
Discussion: The analysis strengthens that planar dosimetric system is not
adequately representative of dose differences in patient. Our finding
clearly shows that the choice of the phantom deeply influences the GI
values. A general criterion for the acceptance of a treatment plan, as
usually done, can not be used. Our study supplies a method to get the
optimal geometry related GI threshold.
FIRST RESULTS OF PERFORMING 3D EPID-BASED IN-VIVO DOSIMETRY
FOR PROSTATE TREATED BY RAPIDARC
E. Villaggi, A.U.S.L. Piacenza
Purpose. To investigate the feasibility of using electronic portal imaging
device (EPID) transit dosimetry and to analyze 3D in-vivo dose-volume
histograms (DVHs) in prostate cases treated by volumetric modulated arc
techniques (VMAT).
Methods and materials: Eleven patients were prospectively enorolled on a
in-vivo quality assurance protocol in which dosimetric EPID images were
acquired during first VMAT treatment fraction.
Portal Dose Images were acquired on a Varian aSi1000 EPID attached to a
Varian ClinacCD linear. Treatments were delivered using the linear accelerator’s 6 MV x-ray beam and a Varian 120 Dynamic MultiLeaf Collimator.
The Varian Eclipse treatment planning system was used to planning
RapidArc prostate treatments in a single arc delivery. Transit dosimetry
calculations were performed using Dosimetry Check software (Math Resolutions LLC).
Pretreatment patient-specific quality assurance was previously performed
using local 3% 3 mm gamma criterion to detect technical sources of systematic error.
2D and 3D dose distributions, point doses, gamma distributions (with 5%
3mm criterion) and DVH statistics were compared.
Results: Absolute differences of Reference Point doses between in vivo
dosimetry and Eclipse calculation averaged 2,6%. Volume and area in
sagittal, axial and coronal plane through the isocenter with gamma < 1 are
reported in table 1, where statistics is relative to ten patients. Planned DVH
parameters were compared with in-vivo results: median dose (D50), near-
maximum dose (D2) and near-minimum dose (D98) in PTV, as recommended in ICRU Report 83. OAR significant values were also compared.
One case was excluded from statistics because very poor match was
observed between prediction and measurement during the transit
dosimetry session. Further investigation attributed this to internal
anatomic changes and a replanning was constructed.
Conclusion: EPID-based in vivo dosimetry could play an important role in
the total chain of verification procedures in a radiotherapy department,
through clinical parameters given by 3DVH in terms of PTV coverage and
OAR overdoses[1].
More research is needed to assess optimal values for alert criteria for 3D
verification of VMAT treatments of various treatment sites[2].
References:
[1] Sean L. Berry et al, Initial Clinical Experience Performing Patient
Treatment Verification With an Electronic Portal Imaging Device Transit
Dosimeter, Int J Radiation Oncol Biol Phys, Vol. 88, No 1, pp. 204-209, 2014
[2] Ben Mijnheer et al, In vivo dosimetry in external beam radiotherapy,
Medical Physics 40 (7), 2013
Table 1
Summary of EPID transit dosimetry results.
Gamma-distribution
Isocenter Point
Dose (Difference)
PTV Doses(Measured
minus Calculated)
Rectum Doses(Measured
minus Calculated)
Bladder(Measured
minus Calculated)
VolumeGamma
< 1 Threshold 10%
VolumeGamma
< 1No threshold
1-percentile
AreaGamma
< 1 transversal plane
AreaGamma
< 1coronal plane
AreaGamma
< 1sagittal plane
Mean Dose
DnearMIN (D2)
DnearMAX(D98)
Median Dose (D50)
Mean Dose
V75Gy
V70Gy
V60Gy
MeanDose
Average
(range)%
Standard
Dviation
82.9(75.7 - 89.2)
3.6%
96.4(94.4 - 98.1)
1.2%
1.6(1.3 - 2.3)
89.1(74.2 - 98.7)
0.3
6.8%
96.6(89.0 - 100)
3.8%
96.6(92.8 - 99.9)
2.2%
2.6(-1.5 - +5.8)
2.4%
2.3(-1.1 - +4.8)
3.9(0.4 - +5 .6)
-2.2(-9.2 - +3.8)
2.8(-0.9 - +4.8)
2.3(-2.6 - +7.3)
2.3(-0.3 - +10.1)
1.3(0.0 - +6.8)
2.3(-0.2 - +6.3)
-6.3(-8.4 - -3.2)
1.7%
1.7%
3.4%
1.7%
3.1%
3.0%
2.0%
1.8%
2.0%
MLC POSITIONAL ACCURACY EVALUATION THROUGH THE PICKET
FENCE TEST ON EBT2 FILMS AND A 3D DOSIMETRIC PHANTOM
Maritina Rouchota, Ioannis Floros, Christina Armpilia, Maria Lyra, Christos
Antypas. 1st Department of Radiology, Medical Physics Unit, Aretaieion
Hospital, University of Athens, Greece
Background: The accuracy of MLC positions during radiotherapy is substantial as even small positional deviations can translate in considerable
dose delivery errors. This becomes crucial when radiosensitive organs are
located near the treated volume and especially during IMRT, where dose
gradients can become steep. A test commonly conducted to measure the
positional accuracy of the MLCs is the picket fence test.
Materials and Methods: Two alterations of the picket test fence test were
performed for the MLC positional inspection. The first alteration was
performed on a radiochromic film, consisting of a series of step-and-shoot
measurements, creating narrow bands at specified intervals. The width of
the narrow bands in the resulting image is checked for discrepancies. The
second alteration was performed on the Delta4 diode array phantom, according to a DICOM RT plan created in the Delta4 software. Leaves make a
series of major stops, at each stop three measurements are considered
around the diodes. The gap width and the MLC dispositions are calculated
through the software and compared to the actual values. Gravity effects
that cause sag and backlash in the MLC carriage and support assemblies
Abstracts / Physica Medica 30S1 (2014)
were also investigated with the Delta4PT phantom by performing the test
in oblique gantry angles.
Results: Results obtained through the two methods showed very good
agreement as far as significant dispositions are concerned. For slight
inaccuracies Delta4PT provided accurate numerical results. As far as gravity
effects are concerned a very slight diversification was observed for an
oblique gantry setup.
Discussion: EBT2 films provide a relatively fast, qualitative visual inspection of the significant leaf dispositions. When slight inaccuracies need
to be revealed or precise numerical results for each leaf position are
needed, Delta4PT provides the desired accuracy. In treatment modalities
where a higher accuracy is required in the delivered dose distribution,
such as in IMRT, a 3D dosimetric phantom is recommended for the MLC
positional inspection.
VERIFICATION OF THE SIEMENS VIRTUAL WEDGE BASED ON g INDEX
Ioannis Floros, Maritina Rouchota, Christina Armpilia, Maria Fakinou, Zoi
Kostakopoulou, Raphaela Avgousti, Maria Lyra, Christos Antypas. 1st
Department of Radiology, Medical Physics Unit, Aretaieion Hospital,
University of Athens, Greece
Background: Virtual Wedges are used in radiotherapy treatment to create
wedge-shaped dose distributions by gradually opening the collimator jaw and
either varying the dose rate or the collimator jaw speed. The common methods
to evaluate their clinical application are based either on point measurements
with an ionization chamber or on two dimensional (2D) measurements with
films or diode arrays. We present a novel method to assess their application
through the g-index calculation of the 3D dose distribution.
Materials and Methods: The measurements were carried out on a 6 MV
Siemens Oncor linear accelerator. Oncentra Treatment Planning System
(TPS) was used for the beam configuration, which was applied on a 3D
array phantom (Delta4PT, Scandidos). All measurements were performed
in isocentric conditions with the isocenter positioned at the center of
the phantom and a gantry angle of zero degrees. The dose distribution
for wedge angles of 15, 30, 45 and 60 degrees, as well as for different
field sizes, generated through the TPS, was compared to the distribution
measured with the phantom through the g-index. The average g-index
for the two wedge orientations was considered for each wedge angle.
The stability of the g-index with increasing levels of monitor units (MU)
was also investigated for all wedge angles.
Results: The verification of the wedged dose distribution for all tested
wedge angles and field sizes provided results of g-index values greater
than 97%. As far as increasing levels of monitor units are concerned, no
specific trend was observed for the g-index values.
Discussion: The Delta4PT provides an accurate alternative method to
evaluate the implementation of the virtual wedges by verifying the dose
distribution through g-index. Through the assessment of the g-index for
increasing level of MUs the ability of the linac to deliver accurate beam
doses was also evaluated.
27
introduced by each implementation step during the whole procedure [1].
The aim of this study is to assess the impact of the anoxic and atmospheric
manufacturing conditions on the dosimetric characteristics of normoxic Nvinylpyrrolidone polymer gels.
Materials and Methods: Two batches of 200mL N-vinylpyrrolidone polymer
gels were produced, containing 5% w/v gelatin, 8% w/v N-vinylpyrrolidone,
4% w/v N,N’-methylenebisacrylamide and 5 mM THPC [2,3]. The first one,
VIPARN2V was produced inside an Argon glove box and the second one,
VIPET2V inside a laminar flow hood (atmospheric conditions). The dosimeters
were irradiated one day after their manufacture with doses ranging from 0.5
up to 60 Gy. All polymer gels were repeatedly scanned utilizing a 1.5T whole
body MR Imager one day, one week, two weeks and one month post-irradiation. A 2D multi-slice- multi echo spin echo sequence was utilized for the
acquisition of the base MR imaging data. Quantitative MRI techniques
revealed the calculated T2 and the dose maps were produced.
Results: Both batches of gels exhibited a linear R2-dose response in the
range of 1 up to 30 Gy. A linear fit (R2 (D) ¼aD+R20) was applied to R2-dose
data for the estimation of the dose sensitivity (a) and of the offset value
(R20) for the time period of one month post-irradiation (Figure 1, 2). It was
revealed that the dose sensitivity of VIPARN2V remained greater for this
period. Also, the offset (R20) values of VIPET2V were constantly increased
rapidly as compared to VIPARN2V offset values.
Conclusion: The impact of the manufacturing conditions on the dosimetric characteristics of VIPARN2V and VIPET2V gels was revealed
through their differences on the dose sensitivity and the offset values
for the time period of one month post-irradiation. It has been proven
that the minimization of oxygen contamination during manufacturing,
improved the dosimetric characteristics of the same composition
polymer gels.
Figure 1. Ă
A PRELIMINARY STUDY: THE IMPACT OF MANUFACTURING CONDITIONS
ON THE DOSIMETRIC CHARACTERISTICS OF N-VINYLPYRROLIDONE
BASED POLYMER GELS
M.-V. Papoutsaki a, b, E. Pappas c, A.E. Papadakis d, C. Varveris e, J.
Damilakis b, T.G. Maris b. a CRUK and EPSRC Cancer Imaging Centre,
Division of Radiotherapy and Imaging, Institute of Cancer Research, 15
Cotswold Road, Sutton, Surrey, SM2 5NG, UK; b Department of Medical
Physics, University of Crete, Medical School, Stavrakia 71110, Crete, Greece;
c
Department of Medical Radiological Technologists, Technological
Educational Institute of Athens, Egaleo, 12210, Athens, Greece;
d
Department of Medical Physics, University Hospital of Heraklion,
Stavrakia, 71110, Crete, Greece; e Department of Radiation Therapy,
University of Crete, Medical School, Stavrakia, 71110, Crete, Greece
Background: The unique characteristics of the polymer gel dosimeters are
essentially their 3D recording ability of the irradiation dose and their tissue
equivalence. However, their use in clinical practice is limited. This is
related to their complexity in manufacture as well as the errors, which are
Figure 2. Ă
28
Abstracts / Physica Medica 30S1 (2014)
CHARACTERIZATION OF SECONDARY RADIATION IN ION BEAM
THERAPY USING SYNCHRONIZED TIMEPIX DETECTORS WITH A
MIXED PIXEL OPERATION MASK
mez c, B. Hartmann b, M. Martisikova b, S.
I. Caicedo a, C. Granja a, B. Go
Pospisil a. a Institute of Experimental and Applied Physics, Czech Technical
University in Prague, Horska 3a/22, CZ 12800 Prague 2, Czech Republic;
b
DKFZ, German Cancer Research Center. Im NeuenheimerFeld 280, 69121
Heidelberg, Germany; c Departamento de Física, Universidad de Los Andes,
, D.C., Colombia
Carrera 1 # 18A-12, Bogota
Ion beam therapy is a highly precise and selective radiotherapy technique
where energetic beams of heavy charged particles (e.g. protons andcarbon ions,
with energies of hundreds of MeV per nucleon) are used to treat malignant
tumors in oncology patients. The interaction of radiotherapeutic ion beams
with matter produces energeticsecondary particles which affect theircharacteristic highly localized energy deposition [1] [2]. A complete characterization of these processes, including visualization of theirspatial distribution is
highly desired to validate and improve the quality of the treatment.
This work is part of an effort to characterize and visualize primary and
secondary radiation in Hadron Therapy procedures with high energy and
spatial (micrometric) resolution, a wide dynamic range, precise tracking
and enhanced particle resolving power made possible by the hybrid silicon
pixelated detector Timepix [3]. Ahodoscope of four synchronizedebut
independent- Timepixdeviceswith different orientations (Figure 1) was
built. Such device allowed to measure the energy deposition of secondary
particles and to determine their origin along the beam path usingtracks
generated by them in each sensor (analog to those seen when using a
nuclear emulsion, as shown in Figure 2). All experiments were carried out
at the Heidelberg Ion Therapy Center, in Germany [4].
These measurements were done simultaneouslyusing a mixed operation
mask: one out of every nine pixels was measuring each particle’s time of
arrival,while the other eight were measuring its energy deposition. The
performance of the mixed operation mask for particle tracking was
compared to results from detectors measuring only the time of arrival to
evaluate its limitations. Secondary fragments were tracked in each sensor
and characterized using pattern recognition algorithms (Figure 3). Afterwards, these tracks were correlated with coincident events in other detectors as a proof-of-principle for synchronized and multi-layered energy
deposition measurements (Figure 4).
The results from this study provide insight on the capabilities of synchronized Timepix detectors for futurearrays of multiple secondary radiation monitors in ion beam therapy.
[1] D. Schulz-Ertner, et al, Semin Radiation Oncology, no.16, pp. 249e259, 2006.
[2] K. Gunzert-Marx, H. Iwase, D. Schardt, and R. Simon, New Journal of
Physics, no. 10, p. 075003, 2008.
[3] X. Llopart, et al., Nuclear Instruments and Methods A, Vol. 581, 2007.
http://dx.doi.org/10.1016/j.nima.2007.08.079.
[4] T. Haberer, J. Debus, H. Eickhoff, O. Jakel, D. Schulz-Ertner, and U. Weber,
“The HeidelbergIon Therapy Center,” Radiotherapy and Oncology, Suppl. 2,
no. 73, pp. S186eS190,2004.
Figure 2. Example of tracks generated by secondary particles in each detection layer of
the hodoscope. First and second detectors were perpendicular to the incident radiation, third and fourth were tilted 60 and 80 degrees, respectively.
Figure 3. Characterization of particles arriving to a single detector based on the
geometric properties of their tracks and deposited energy. (Right) Size and energy
distribution of correlated events in two of the hodoscope detection layers.
Figure 1. (A): A Timepix detector. (B): Layout of a Timepix-based hodoscope of four
synchronized layers with different tilts (0, 60 and 80 degrees), reference numbers
identify the sensor. (C): Setup of the hodoscope to identify secondary particles
emerging from the interaction of a carbon beam with two small PMMA cubes.
Abstracts / Physica Medica 30S1 (2014)
Figure 4. Cluster size (Number of pixels from each particle hit) vs. energy distribution
of correlated events in two of the hodoscope detection layers.
ELECTRON BEAM DOSE DISTRIBUTION ANALYSIS FOR IRREGULAR
FIELDS IN TREATMENT OF SUPERFICIAL TUMORS: A MONTE CARLO
STUDY
M.B. Tavakoli, P. Shokrani, K. Bamneshin. Department of Medical Physics
and Medical Engineering, School of Medicine, Isfahan University of Medical
Sciences, Isfahan, Iran
Introduction: In superficial treatments with electron beam, irregular
fields are usually produced by using lead shields which are placed either at
the end of the applicator or on the surface of the patient body. For these
fields the amount of scatter and therefore the dosimetric parameters such
as PDD, profiles and output factor may change with respect to the regular
fields. The objective of this research was to investigate the effect of
shielding on electron field using Monte-Carlo method.
Materials and methods: DOSXYZnrc code were used for simulating
Nepton 10PC linac head and BEAMnrc code for simulating irregular
fields obtained from 1515cm2, 2020cm2, 2525cm2 to calculate
dosimetric parameters of percentage depth dose (PDD), dose profiles
and output factors for different field configurations. A total number of
60 irregular fields were investigated. The calculated results were
compared with equivalent field methods. To evaluate the accuracy of
calculation, the calculated results of PDD were compared with the
measured results obtained with a Scanditronix p-type silicon diode in a
phantom.
Results and conclusion: The study, showed that maximum changes for
90% depth dose of 6MeV electron is 2.2mm. Maximum change in output
factor for the mentioned energy when maximum shielding was applied is
6.3%. The results also showed that using equivalent square field method is
not an appropriated method for dose calculation when irregular field is
used especially when PDD is considered. The percentage of error increases
with increasing percentage of the shielding.
Keywords: Dosimetry, irregular fields, Linear accelerator, percentage depth
dose,
FEASIBILITY AND DOSIMETRIC CHARACTERIZATION
CONVERGENT BEAM TELETHERAPY DEVICE
OF
SINGLE
Rodolfo G. Figueroa a, Mauro Valente b. a Physics Department, Universidad
de La Frontera, Temuco Chile; b CONYCET, Fa.M.A.F. Universidad Nacional de
rdoba, Co
rdoba, Argentina
Co
Background: Currently X-photons teletherapy utilizes divergent beams,
which implies a non-negligible irradiation of healthy tissues. A convergent
beam would allow a greater radiation focalization. This work aimed to
determine feasibility and characteristics of a new type of radiation therapy
based on the application of a convergent beam of photons, using a device
capable of generating a convergent X-ray beam of energies. We named this
technique RTHC.
29
Materials and Methods: An analytical method was developed to determine dosimetric characteristics of an ideal convergent X photon beam in a
hypothetical water phantom. Then, using Monte Carlo (MC) code,
PENELOPE, an ideal convergent beam was applied to a water phantom
using a specially adapted geometry; results were compared with those of
the analytical method. MC simulations were performed in a vacuum, using
a more realistic geometry. These simulations were performed for a largesize thin spherical anodic target (30 cm radius). Thus, the electrons
perpendicularly impact upon various points of the cap (RTHC condition,
convergent beam radiotherapy), mainly at the focal point in the water
phantom center. The X radiation (bremsstrahlung) is generated toward the
focus. A spherical collimator coaxial to the cap, with many holes, allows a
clean convergent X-ray beam output. On the other hand, magnitudes of the
electric / magnetic fields necessary for a clinical use electron beam (0.1 to
20 MeV) are determined using electromagnetism equations with relativistic corrections.
Results: In-depth dose peaks similar in shape to hadron therapy were
shown. This remarks that in-depth dose peaks are generated at the
focus point/isocenter. The electric and magnetic fields needed to control
the deflection of the electron beams in the RTHC geometry were
calculated.
Discussion: Results are consistent with those obtained with PENELOPE
code. Peak-focus is independent of the X photon beam energy, though its
intensity is not. Aperture angle at each impact point depends on the energy beam, the atomic Z number and the target thickness. Electric and
magnetic fields necessary to control the X-ray beam are highly feasible by
means of a specially designed electric/magnetic device. Electric fields are
much more difficult to achieve than magnetic ones, especially at high
energies. In conclusion, is possible to generate a device with the abovementioned characteristics (Pat.Pending-CoverayTM)
POLIMER GAFCHROMIC EBT3 FILM FOR ELECTRON DOSIMETRY OF
BETATRON BEAM
Evgeniia Sukhikh a, b, Leonid Sukhikh b, Evgeniy Malikov b. a Research
Institute for Oncology, Kooperativnyy st., 5, Tomsk, 634050, Russia;
b
National Research Tomsk Polytechnic University, Lenin ave., 30, Tomsk,
634050, Russia
Keywords: radiation therapy, Gafchromic EBT3 polymer films, cylindrical
and plane-parallel ionization chamber, a linear accelerator, betatron, X-ray
tube
Background: Intraoperative radiotherapy is a treatment modality for a
locally advanced tumor of the abdomen, pelvis and breast, which involves
the use of large single dose of radiation delivered to the tumor or bed of
tumor and areas of potential regional spread during the surgical operation.
The modality is based on electron beams of MeV energies due to particular
dose distribution in the tissue-equivalent environment [1,2].
Nowadays, most of the clinics worldwide carry on the IORT procedure
using the electron sources based on the compact linear accelerators.
However, in Russia historically several clinics have been using the sources
based on betatrons. The main advantages of the betatrons are the possibility to change the beam energy in a wide range with small steps (e.g. 2-6
MeV with spacing 0.5 MeV), low energy spread of the beam and the
relatively low cost of a device (typically $ 200 000). These days our team
develops new generation of betatrons with extracted electron beam for
IORT and skin cancer treatment.
Materials and Methods: The investigation of 3D dose distributions
generated by new prototype of IORT source based on betatron was carried
out in the energy range 2-6 MeV with 500 keV steps. The dose distributions were measured using plane-parallel and cylindrical ionization
chambers and Unidose-E electrometer [3-5] and radiochromic films Gafchromic EBT-3 [6-9]. The films were calibrated using 10 MeV electron
beam of Electa Axcess accelerator and 2 MeV beam of our betatron. . All
measurements were performed in tissue-equivalent phantom with zero
air gap.
Results: The results of radiochromic film calibration are shown in Fig.1.
The calibration was carried out for both red and green channels of the film.
Basing on obtained calibration the measurements of absolute dose distributions were carried out. Fig. 2 shows the 2D distribution of the absolute
30
Abstracts / Physica Medica 30S1 (2014)
absorbed dose in the phantom obtained for 2 MeV electron energy of
betatron.
Discussion: The results obtained show that the betatron with extracted
electron beam could be considered as a suitable source for development of
IORT complex. However more efforts should be invested in the development of appropriate system of the radiation field formation.
Figure. 1. Calibration dependencies for the electron beam. White diamonds stays for
the red channel and 10 MeV beam, black diamonds e red channel, 2 MeV beam, white
hexes e green channel, 10 MeV beam, gray hexes e green channel, 2 MeV
Figure. 2. The depth distribution of absorbed dose on the betatron beam 2 MeVĂ
1. L. I. Musabaeva, E. L. Choyzonov, “Intraoperative electron and
gamma distance - therapy of malignant tumors”, NTL, Tomsk
(in Russian) 2006.
2. C. Ronsivalle, L. Picardi, A. Vignati, A. Tata and M. Benassi,
“Accelerators development for intraoperative radiation therapy”, Proceedings of the 2001 Particle Accelerator Conference. Chicago, 2001. - Р. 24-94
3. B. J. Gerbi, J. A. Antolak, F. Ch. Deibel, and et al., “Recommendations for clinical electron beam dosimetry: Supplement to
the recommendations of Task Group 25”. Med. Phys. vol. 36, No.
7, pp. 3239-3279, 2009.
4. Khan F.M., Doppke K.P., Hogstrom K.R. and et al., “Clinical
electron-beam dosimetry: Report of AAPM Radiation Therapy
Committee Task Group No. 25”, Med. Phys, vol. 18, No. l, pp. 73109, 1991
5. Peter R. A., Peter J. B., Coursey B. M., W. F. Hanson M., “AAPM’s
TG-51 protocol for clinical reference dosimetry of high e energy photon and electron beams”, Medical Physics, vol. 26, No.
9 - pp. 1847-1870, 1999.
6. Azam N., Charles R. B., Bert M. and et al., “Radiochromic film
dosimetry: Recommendations of AAPM Radiation Therapy
Committee Task Group 55”, Medical Physics. vol. 25, No. 11, pp.
2093-2115, 1998
7. Slobodan D., Nada T., Zhiyu P., Jan S., and et al., “Absorption
spectroscopy of EBT model gafchromic™ film”, Medical Physics, vol. 34, No. 1, pp. 112 - 118, 2007
8. Gafchromic EBT3 radiochromicdosimetry film - electronic
resource
http://www.gotopeo.com/en/extra/529-peopresenteert-de-nieuwe-generatie-isp-gafchromic-ebt3
9. E.S. Sukhikh, P.V. Filatov, E.L. Malikov, “Calibration of polymer
film Gafchromic EBT3 using electron and photon beams”,
MedicinskayaFizika, vol. 2, No. 58, pp. 50-60, 2013, in Russian.
Physica Medica 30S1 (2014)
Contents lists available at ScienceDirect
Physica Medica
journal homepage: http://www.physicamedica.com
e-Posters
IN VIVO DOSIMETRY AS A PART OF QUALITY ASSURANCE PROGRAM
FOR BREAST CANCER IRRADIATION
Laza Rutonjski, Borislava Petrovi
c, Milutin Baucal, Milan Teodorovi
c, Ozren
Cudi
c, Borko Basaric. Institute of oncology of Vojvodina, Sremska Kamenica,
Serbia
Purpose: The study was aimed to check treatment accuracy and definition
of action levels during implementation of in vivo dosimetry as a part of
quality assurance program. Treatment accuracy was quantified as the ratio
of the measured dose at accelerator and the expected dose from the
treatment planning system (TPS). The study sampled 3D conformal breast
patients with two isocentric tangential half-field technique with at least
two fields. Action levels in breast irradiation with and without bolus were
also defined and checked.
Materials and methods: Irradiation of breast patients in 3D conformal
therapy involved 6 MV energy, and at least two tangential fields. Fractionation scheme of five sessions per week of 2 or 2.67 Gy per fraction up
to a total dose of 50 or 40Gy, respectively. All correction factors as per
ESTRO booklet 5 recommendation were determined. The entrance dose
was measured at offaxis distance of 3 to 5cm from isocenter at medial
tangential field during first treatment. During initial implementation,
action level was set to be 5% for all breasts treatment, with or without
bolus.
Results: In this study, 167 patients with tangential half-fields were irradiated over a 10-month period. The total number of patient set-up procedures analyzed was 183, with second measurement included, giving a
distribution of treatment accuracy with mean deviation from expected
entrance dose of 1.43% and a standard deviation of 2.83%(1SD), for all
patients. Standard deviation from expected entrance dose for patients
without bolus was 1.18% and a standard deviation of 2.81%(1SD), and for
patients with bolus, 1.33% and 3.04%(1SD), respectively. 8.3% of all measurements exceeded the 5% tolerance with 3% exceeding a 7% level. The
causes of these errors were identified and appropriate action taken where
necessary.
Conclusions: In our experience, systematic in vivo dosimetry proved to be
a vary useful tool for quality assurance of a patient plan and treatment,
both in detecting systematic errors and for estimating the accuracy of
treatment delivery. Action levels in breast irradiation with tangential field
technique was accordingly lowered to 3.5% (30% lower than initial 5%) for
all treatment, with or without bolus. Larger standard deviation was
noticed for bolused patients due to more difficult diode positioning and
measurement.
References
€o
€ f, H. Nystro
€ m, C.
1. D.P. Huyskens, R. Bogaerts, J. Verstraete, M. Lo
Fiorino, S. Broggi, N. Jornet, M. Ribas, D.I. Thwaites. Practical guidelines
for the implementation of in vivo dosimetry with diodes in external
radiotherapy with photon beams (entrance dose). ESTRO BOOKLET
No. 5
2. J. Van Dam and G. Marinello METHODS FOR IN VIVO DOSIMETRY IN
EXTERNAL RADIOTHERAPY. ESTRO BOOKLET No. 1
3. Luca Cozzi, Antonella Fogliata-Cozzi. Quality assurance in radiation
oncology. A study of feasibility and impact on action levels of an in vivo
dosimetry program during breast cancer irradiation. Radiotherapy and
Oncology 47 (1998) 29e36
4. S. Heukelom, J. H. Lanson, G. van Tienhoven and B. J. Mijnheer. In vivo
dosimetry during tangential breast treatment. Radiotherapy and Oncology,
22 (1991) 269-279
5. J C Millwater, A C Macleod, D I Thwaites. In vivo semiconductor
dosimetry as a part of routine quality assurance. The British Journal of
Radiology, 71 (1998), 61-668
6. R.Appleyard, K. Ball, F.E. Hughes,W. Kilby, S. Lassen, R. Nicholls,V. Rabett,
J. Sage, M. Smith, E.Thomson. Systematic in vivo dosimetry for quality
assurance using diodes. Part 1: Experiences and results of the implementation of entrance dose measurements. Journal of Radiotherapy in
Practice 2003, 3, 185e196
7. R.Appleyard, K. Ball, F.E. Hughes,W. Kilby, S. Lassen, R. Nicholls,V. Rabett,
J. Sage, M. Smith, E.Thomson. Systematic in vivo dosimetry for quality
assurance using diodes 2:Assessing radiotherapy techniques and developing an appropriate action protocol. Journal of Radiotherapy in Practice
2005, 4, 143-154
DOSE CONSTRAINTS OPTIMIZATION AND ESTIMATION IN DIAGNOSTIC
MEDICAL DEPARTMENTS USING IONIZING RADIATION
Hanna Piwowarska-Bilska a, Monika Nowak b, Maria H. Listewnik a, Piotr
Zorga a, Jacek Iwanowski a, Anna Walecka b, Bozena Birkenfeld a. a Department
of Nuclear Medicine, Pomeranian Medical University, Szczecin, Poland;
b
Department of Diagnostic Imaging and Interventional Radiology, Pomeranian
Medical University, Szczecin, Poland
Introduction: The concept of dose constraints is one that has been discussed extensively during the development of ICRP Publication 103, and
continues to elicit concern.
The practical use and implementation of dose constraints in radiological
protection in the medical profession is difficult because of a lack of recommendations of specific levels of constraints for different occupational
groups. This study aims to estimate local dose constraints for workers in
conventional nuclear medicine and radiology departments.
Materials and methods: The dose constraints for staff in conventional
nuclear medicine and radiology departments were estimated on the
basis of doses received in the last 3 to 4 years by different groups of
workers. Overall, 127 annual doses of the employees of the Department
of Nuclear Medicine and Department of Diagnostic Imaging and Interventional Radiology, registered in periods 2008-2011 and 2009-2011,
respectively, were analyzed statistically. Doses records were grouped
according to the occupational category (nuclear medicine and radiology) and the occupational group (medical doctors, technicians,
nurses). For estimation of dose constraints values per occupational
group, the dose level below which the 75% of annual doses were
respectively included (upper third quartile), as well as the average doses
and dominant values achieved by each group during the periods under
consideration, was calculated.
Results: For the determination of dose constraints, annual doses below the
method detection limit have been excluded from the analysis: 14 (~19%)
for nuclear medicine and 23 (~26%) for radiology. During the analyzed
periods, there was no incidence of a dose exceeding the annual dose limit
of 20 mSv in both departments. The highest exposure was observed for
nuclear medicine nurses and technicians. For both these groups the dose
constraint was estimated at 2.5 mSv/year. The dose constraint was set at 1
2
Abstracts / Physica Medica 30S1 (2014)
mSv/year for nuclear medicine physicians as well as all workers of the
radiology department.
Conclusions: 1. Local dose constraints can be estimated on the basis of
workers’ dose records for the last 3-4 years using simple statistical analysis. 2. The level of dose constraints should be adjusted to the local conditions of radiation protection of workplaces and tasks performed by
various professional groups.
THERMOLUMINESCENCE AND ELECTRONIC DOSIMETRY FOR 511 KEV
PHOTONS
effect on the output factor. A nominal field of 1x1 cm2 has an output factor
5.7% lower than the 1.1x1.1cm2 and 10.5% than the 1.2X1.2cm2 radiological
field.
We conclude that special care must be taken for small fields. An adequate
algorithm modelling the beam source should be used. The source parameters should be fine-tuned for accurate dose calculations. Furthermore,
careful quality control of the Linac’s mechanical components should be
carried out.
Keywords: Small fields, Dosimetry, External radiotherapy
K. Dalianis, K. Gogos, R. Efthimiadou, I. Andreou, V. Prassopoulos. Hygeia
S.A. PET/CT Department, Athens, Greece
INVESTIGATING COLUMNAR SCINTILLATORS THROUGH ANALYTICAL
MODELING. A SEMIEMPIRICAL APPROACH
Aim: The most commonly used radio nuclide in PET/CT departments is
18F-FDG. The 18 F-FDG PET/CT applications have been continuously
increasing for diagnostic procedures. Although such an increase is a
positive trend for the benefit of patients, the associated risk of radiation
exposure of staff needs to be properly evaluated. Our aim is to compare
the estimated doses from TLDs dosimeters with the electronic dosimeters regarding 511 kev annihilation photons following the ALARA
principle.
Method: In order to estimate the doses from external exposure, all 7
members of the staff (2 nurses, 2 medical physicists, 2 technologists, 1
secretary) had TLD badges worn at the upper pocket of their overall and
digital dosimeters at their upper side pocket.
Results: The dose estimated from the TLDs is evaluated monthly and is
compared with the dose assessed by the electronic dosimeter. The results reveal a difference between the electronic dosimeters and the TLDs
from 0,2% to 1,3%, with the dose being overestimated when assessed by
TLDs. The main reason for the differences is that the dosimeters have
been used for different time periods. When both TLD and electronic
dosimeters have been correctly measured then the TLD is considered to
show the correct value of the absorbed dose and the dose is overestimated only by a small percentage of 0.37% when measured with
TLDs.
Conclusion: TLDs are considered to be trustworthy in assessing the
absorbed dose. However the use of electronic dosimeters cannot be
ignored in the daily practice as they measure radiation exposure on a real
time basis and provide immediate dose rate readings.
N. Kalyvas, C. Michail, G. Fountos, I. Valais, I. Kandarakis, D. Cavouras.
Department of Biomedical Engineering, Technological Educational Institute
of Athens, Greece
ADJUSTING SOURCE MODELLING PARAMETERS FOR ACCURATE DOSE
CALCULATIONS WITH THE ONCENTRA MASTERPLAN TREATMENT
PLANNING SYSTEM FOR SMALL FIELDS WITH DIMENSIONS OF LESS
THAN 5X5CM2
Malatar Georgia a, S. Papatheodorou a, V. Anastasis b. a University Hospital
Patras, Greece; b University of Patras, Greece
The dosimetry of small fields in photon radiotherapy is a challenging issue.
The goal of this work is to establish a reliable method to measure the
absolute dose in small fields and to verify the TPS calculations, such as
output factors, PDDs and profiles for small fields less than 5X5cm2.
The output factors for collimator settings from 5x5cm2 down to 1X1cm2
were measured in a water tank at the reference depth of 10cm, at
SSD¼100cm, with the PinPoint chamber and a calibrated MOSFET
dosimeter. Output factors and dose profiles have been measured on an
Elekta Synergy Linac with a 6MV photon beam. They have also been
calculated using the Oncentra Masterplan version 4.3.
We have found out that it is not easy to determine source-size parameters,
for the TPS, which yield acceptable results for the entire range of field sizes
(from 40x40 cm2 to 2x2cm2). Therefore, we have created a new “virtual”
Linac in the TPS beam library dedicated to small field clinical applications.
For this Linac the source-size parameters have been fine-tuned such that
the calculated profiles match the measured data for small fields only. With
this approach the discrepancies between measured and calculated doses
have been diminished considerably. The comparisons between measured
and calculated PDDs and dose profiles have been evaluated using the
methodology of the g-composite criterion.
For fields less than 2X2cm2 the output factor drops rapidly with field size.
Small errors in the filed size due to jaw misplacements have a dominant
X-ray digital imaging systems often employ scintillator materials as part
of the radiation detector (indirect detection). Recently CsI:Tl columnar
phosphor is used extensively as an X-ray converter due to its higher
spatial resolution compared to granular phosphors like Gd2O2S:Tb. The
efficiency and the imaging performance of CsI:Tl has been already studied
either experimentally or by Monte Carlo simulation. The aim of this work
is to provide a semi empirical analytical model for determining CsI:Tl
optical photon propagation related parameters like photon attenuation
per elementary thickness and spread to the output. Hence the calculation
of Detective Quantum Efficiency (DQE) of CsI:Tl for different column
thicknesses (50mm up to 300mm) was achieved. The developed model
considers the absorption of X-rays in the scintillator, the production of
optical photons, the propagation and the reflections of the optical photons to the input and output interfaces. Finally it acknowledges the
spread of the optical photons to the output. The optical photon propagation is studied by considering that the fraction of the optical photons
passing through an elementary screen layer is constant. The optical
spread to the output is assumed to result in a Gaussian shaped LSF.
Published Monte Carlo data for 85 mm, 100 mm and 300 mm CsI:Tl columns were used to fit the analytical model equations. The optical photon
fraction transmitted through each layer was found approximately 98.6%.
The LSF shape was found to be depended by column thickness. Higher
DQE at 0 lp/mm exhibited the 300mm column thickness CsI:Tl, while at
10lp/mm the 50mm column thickness CsI:Tl. It was interesting to notice
that at approximately 4lp/mm the DQE curves of all thicknesses were
comparable.
Keywords: Columnar phosphors, MTF, DQE
Acknowledgement: This research has been co-funded by the European
Union (European Social Fund) and Greek national resources under the
framework of the “ARISTEIA” project MISCIRLU code 1476 of the “Education & Lifelong Learning” Operational Programme.
NEW CHALLENGES IN OPTIMIZATION OF RADIATION-DOSE IN INFANTS
HIP-EXAMINATIONS X-RAY PROCEDURES
€ stur Finbogasson MD, PhD, Britt-Marie
Shahla Mobini MSc, Thro
€
OstlundRadiologic
Nurse, Theo Chouliaras MSc, Angela Karambatsakidou
€ m MSc licentiate. Department of Medical Physics,
MSc, Jan Lindstro
Karolinska University Hospital, S-171 76 Stockholm Sweden; Department of
Pediatric Radiology Astrid Lindgrens at Karolinska University Hospital, S171 76 Stockholm, Sweden
The risk of radiation effect is age dependent according to International
Commission on Radiological Protection ICRP (2007). Since children have a
longer life expectancy than adults, it follows a higher probability of late
effects. The variation in sensitivity of different organs and tissue also differ
from that of adults (BEIR V 1990). Optimization of radiation dose for pediatric patients is therefore of high priority. A dose survey was performed
with the aim to establish the Local Dose Reference level (DRL) for various
examination types.
The result showed that there is room for further optimization in hipexaminations and the corresponding anatomic specific programs. A
Abstracts / Physica Medica 30S1 (2014)
policy in the Medical Physicist community and recommendations from
the European Guidelines on Quality criteria in Diagnostic Radiographic
images in Pediatrics (EUR 16261 EN), state that Automatic Exposure
Control (AEC) is of limited value for smaller patients. Instead, exposure
charts are recommended for pediatric patients. While this statement is
still broadly true, there is a need to systematically confirm the limitation
levels of modern X-ray equipment due to the continuous technical
development.
In practical terms, as the AEC resides fixed in the examination table, the
combination of removable detector and AEC is as easy to use as a standalone removable image detector. However, mispositioning the patient was
more common for the standalone detector thus resulting in retakes. The
AEC exams were assessed by one pediatric radiologist and all exams were
found to have good diagnostic quality.
Based on the study, we have suggested a novel categorization of patients
for a better optimization i) newborn ii) 0-1y iii) 1-5y, iv) 5-10y and v) 1015y. Other influencing parameters as gender based differences are also
investigated. This work also contains risk estimations of different techniques while discussions on age banding compared to weight categorization also are included. The results of the current study showed that using
AEC on children from 6 months to 1 year of age, corresponding Kerma Area
Product (KAP) was reduced by about 60% compared to examinations based
solely on exposure charts.
3
evaluation concerning the monitoring of the patient radiation protection in diagnostic radiology and interventional radiology was initiated
in 2006.
All providers of radiology and medical imaging examinations have to record patient data and relevant information for assessment of doses
received by patients from medical exposures to ionizing radiation.
Ministry of Health through the National Institute of Public Health Regional Centre for Public Health, centralizes the data of medical
exposure to ionizing radiation reported by providers of radiology and
medical imaging examinations and elaborates an annual report.
The forms for reporting the centralized data contain the exam type,
procedure code, total number per exam type and its distributions on
age groups and gender groups. Dose information is available in terms of
DAP-meter values or entrance surface dose for conventional X-ray
procedures and DLP indication for CT procedures. For estimation,
we assume that, in one year, the total number of reported procedures
per number of reporting units is proportional with the total number of
estimated procedures per total number of units in the whole country.
In our study, the frequency of X-ray examinations for 2010-2012
years (including the conventional radiology, interventional radiology,
computed tomography and dental radiology) and mean effective doze
per procedure were estimated. Summary of the mean effective dose
(mSv) for X-ray procedure types performed at the national level for Top
20 (defined by RP 154) and for all X-ray based radiology is presented in
Table 1.
COMPARATIVE STUDY OF IMAGE QUALITY AND ENTRANCE SURFACE
DOSE IN TWO RADIOGRAPHIC UNITS: FLAT PANEL DETECTOR VERSUS
COMPUTED RADIOGRAPHY SYSTEM
Ioannis Antonakos, Zoi Thrapsanioti, Sophie Ioannidou, Efstathios
Efstathopoulos. University of Athens, 2nd Department of Radiology,
University General Hospital ‘Attikon’, Rimini 1, 124 62 Athens, Greece
Aim: The aim of this study is to present a method to assess two radiographic units with different capture technology, in terms of Entrance
Surface Dose (ESD) and Image Quality.
Materials and methods: Measurements were conducted at the University
Hospital “ATTIKON”. Philips Optimus with flat panel detector (FPD) Canon
and G.E MPH equipped with a CR Agfa system were compared. A solid state
€ lndal, Sweden) was
detector R100B (Barracuda, RTI Electronics AB, Mo
placed over PMMA plates of various thicknesses (2-20 cm) in order to
measure ESD. Leeds TOR 18FG test object was placed in the middle of the
plates to assess image quality. The measurements simulated conditions of
standard protocols of chest PA, abdomen AP, cervical and pelvis AP protocols. In both units, Mean Pixel Values (MPV) were measured at certain
Regions of Interest (ROI's) to calculate Signal-to-Noise Ratio (SNR). A Figure
of Merit (FOM) was utilized to evaluate image quality and ESD at the same
time.
Results: SNR was found to be 60-80% higher in the CR than in the FPD
system, depending on the protocols tested. Regarding ESD, it appeared to
be 65%-85% higher in the CR system. Respectively, in pediatric protocols
SNR was 55%-70% higher in the CR system and ESD was almost 80% higher
in the CR than in the FPD system. FOM for all the pediatric and adult
protocols tested, apart from pelvis and abdomen protocols, seemed to be
higher in the CR than in the FPD system.
Conclusions: SNR was found to be higher in CR than in FPD system,
indicating better image quality but higher ESD. FOM seems to be a useful
objective tool for assessment of image quality and entrance dose simultaneously. Taking the FOM into account, the use of the CR unit is recommended for all the examined protocols except for pelvis and abdomen, in
which FPD may be preferred. Clinical evaluation of our results is warranted
to precisely determine the role of FOM on optimization of the radiographic
technique.
THE PATIENT DOSE ESTIMATION FROM MEDICAL EXPOSURE FOR 20102012 YEARS
Olga Girjoaba, Alexandra Cucu. National Institute of Public Health, Romania
In order to reduce the risk associated with diagnostic medical exposure
by optimizing the quality of radiological imaging, a nation-wide
Table 1 The mean effective dose (mSv) for X-ray procedures performed in 20102012 years
Main results
Mean effective
dose (mSv)
in 2010
Mean effective
dose (mSv)
in 2011
Mean effective
dose (mSv)
in 2012
Plain radiography Top 20
Fluoroscopy Top 20
Cardiac angiography
CT Examinations Top 20
All Angiography and
Interventional radiology
SUM all X-ray based
radiology ex. Dental
Dental
SUM all X-ray based
radiology
0.33
9.60
4.83
3.20
3.00
0.56
5.23
8.11
8.41
7.42
0.23
1.72
6.91
9.58
9.97
0.49
1.16
0.93
0.28
0.46
0.09
1.04
0.02
0.81
For some X-ray procedure types, we remark significant differences between 20102012 years, concerning the mean effective doze per modality, without important
changes in radiological practices in that period. We suspect that the data regarding
the dose received by the patients are incomplete and/or incorrectly registered and
reported from different causes. Taking into account the new Council Directive 2013/
59/EURATOM provisions concerning the medical exposure, it is very important to
find the best modalities for improvement of patient doses registering and reporting
system.
EVALUATION OF A SIPM ARRAY COUPLED TO A GD3AL2GA3O12:CE
(GAGG:CE) DISCRETE SCINTILLATOR
S. David a, M. Georgiou a, b, E. Fysikopoulos a, c, G. Loudos a. a Department of
Biomedical Engineering, Technological Educational Institute of Athens,
Athens, Greece; b Department of Medical School, University of Thessaly,
Larissa, Greece; c School of Electrical and Computer Engineering, National
Technical University of Athens, Athens, Greece
Aim: Silicon Photomultipliers (SiPMs) are relatively insensitive to magnetic fields and thus are good candidates for MR combined applications [12]. In this study, we present the results of the SensL ArraySL-4 (4x4
element array of 3x3mm2 SiPMs) photo-detector coupled to a 6x6
GAGG:Ce scintillator array, with 2x2x5mm3 crystal size elements and pitch
equal to 2.1mm. Experimental evaluation was carried out with 22Na and
137
Cs radioactive sources in terms of energy resolution and peak to valley
ratio.
4
Abstracts / Physica Medica 30S1 (2014)
Methods and Materials: ArraySL-4 is a commercially available, solid-state,
4x4 array detector covering an active area of 13.4mm2. Each pixel has 4774
square microcells connected in parallel, with individual cell side equal to
35um. GAGG:Ce scintillator array used in this study were purchased by
Furukawa Co Ltd [3]. The reflector material used in the array is BaSO4 with
0.1mm thickness. GAGG:Ce scintillator is non hygroscopic, has good light
yield (46000 ph/MeV) with peak emission at 530nm. Moreover, GAGG:Ce
does not contain natural radioactivity, since it does not uses Lu. The density
of GAGG:Ce is 6.63 g/cm3, with effective atomic number equal to 54.4 [4-6].
A symmetric resistive voltage division matrix was applied, which reduces
the 16 outputs of the array to 4 position signals [6-7]. A Field Programmable Gate Array (FPGA) Spartan 6 LX150T was used for triggering and
signal processing of the signal pulses acquired using a free running sampling technique [8].
Results: A raw image and the horizontal profile of one raw of the 6x6
GAGG:Ce scintillator array produced under 511keV excitation are shown in
figure 1. The mean peak to valleys ratio is 40 (std¼8.2).
Fig. 1. Raw image of the 6x6 GAGG:Ce scintillator array and a horizontal profile of
the central scintillator elements produced under 511keV excitation. Scintillator
array is coupled with optical grease (BC-630).
Energy spectra obtained with two different radioactive sources from a
single 3x3x5mm3 GAGG:Ce scintillator element (red square on raw image)
are shown in figure 2. The mean energy resolution for the GAGG:Ce array
was calculated equal to 10.5% (std¼0.44) and 9% (std¼0.63) under 511keV
and 662keV irradiation using Gaussian fit within a +/-10% energy window
centered around the photopeak.
could be an interesting application using the aforementioned GAGG/
SIPM array detector. In such a dual SPECT/PET detector module, proper
mechanical insert of the collimator, as well as the adjustment of the
SiPMs array bias voltage and the gain amplification of the position
signals have to be properly controlled to allow transition from PET to
SPECT mode.
Acknowledgment: This research has been co-funded by the European
Union (European Social Fund) and Greek national resources under the
framework of the “Archimedes III: Funding of Research Groups in TEI of
Athens” project of the “Education & Lifelong Learning” Operational
Program.
References:
C. Piemonte et al. ”Recent developments on silicon photomultipliers
produced at FBK-irst ,” IEEE Nucl. Sci. Symp. Conf. Rec: pp. 2089e2092,
2007.
H. S. Yoon et. al. ”Initial results of simultaneous PET/MRI experiments with
an MRI-compatible silicon photomultiplier PET scanner,” J.N.M, vol. 53, pp.
608, 2012 Available online at: http://www.furukawakk.co.jp/e_index.htm
J. Iwanowska et al. ”Performance of cerium-doped Gd3Al2Ga3O12
(GAGG:Ce) scintillator,” Nucl. Instr. and Meth. Phys. Res. A, vol. 712, pp. 3440, 2013.
S. Yamamoto et al. ”Development of an ultrahigh-resolution Si-PM-based
dual-head GAGG coincidence imaging system,” Nucl. Instr. and Meth. Phys.
Res. A, vol. 703, pp.183-189, 2013.
S. David et al. ”Comparison of three Resistor Network Division Circuits for
the readout of 4x4 Pixel SiPM Arrays,” Nucl. Instr. Meth. Phys. Res. A, vol.
702, pp. 121e125, 2013.
V. Popov et al. ”A novel readout concept for multianode photomultiplier
tubes with pad matrix anode layout,” Nucl. Instrum. Meth. A, vol 567, pp.
319, 2006.
M. Streun, G. Brandenburg, H. Larue, E. Zimmermann, K. Ziemons and H.
Halling, ”Pulse Recording by Free-Running Sampling,” IEEE Trans. Nucl. Sci.
vol.48, pp. 524, 2001.
M. Georgiou, S. David, E. Fysikopoulos and G. Loudos ”Development of a
SIPM based gamma-ray imager using a Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillator array,” IEEE Nucl. Sci. Symp.& Med. Imag conf. M21-48, Oct 27- Nov 2,
Seoul, Korea, 2013.
CANCER RADIATION THERAPY: QUO VADIS?
Мersini Мakropoulou. Physics Department, School of Applied Mathematical
and Physical Sciences, National Technical University of Athens, Greece
Fig. 2. Energy spectra of a central scintillator element of the GAGG:Ce array under
22
Na and 137Cs irradiation.
Discussion e Conclusion: The acquired raw image of the GAGG:Ce
crystal array under 511keV excitation shows a clear visualization of
all (6x6) discrete scintillator elements with a mean peak to valley
ratio equal to 40. The mean energy resolution was measured equal to
10.5% and 9% respectively under 511keV and 662keV irradiation.
Taking into account the results conducted in a previous study of our
group [9] under low energy isotopes i.e. 57Co and 99mTc (for SPECT applications) using the same detector module materials, (mean energy
resolution equal to 16.1±0.52% at 140keV and 18.1±0.64% at 122.1keV
with high peak to valley ratio above to17) a SPECT/PET hybrid detector
In oncology, treating cancer with a beam of photons is a well established
therapeutic technique, developed over 100 years, and today over 50%
of cancer patients will undergo traditional X-ray radiotherapy. However,
ionizing radiation therapy is not the only option, as the highenergy photons releasing their energy into cancerous tumor can lead
to significant damage to healthy tissues surrounding the tumor.
Therefore, in nowadays, advances in ionizing radiation therapy are
competitive to non-ionizing ones. For example, photodynamic therapy
(PDT) is another type of cancer treatment that uses laser light to destroy
tumors. Apart of PDT, laser light can be used to remove cancer or
precancerous tumors or to relieve symptoms of cancer, such as bleeding
or obstruction. In PDT, a photosensitizer is injected into a patient and
distributed all over the patient’s body. After a couple of days,
the photosensitizer is accumulated selectively in cancer cells. Laser light
is then used to activate the agent and destroy cancer cells, in the
presence of cellular oxygen. PDT is a non-invasive or minimally invasive
therapeutic procedure (through flexible endoscopes). The use of minimally invasive techniques in the management of patients represents a
very interesting treatment option. Moreover, as the major breakthrough
in cancer management is the individualized patient treatment, new
biophotonic techniques, e.g. photo-activated drug carriers, help
the improvement of treatment efficacy and/or normal tissue toxicity.
Additionally, recent studies support that lasers could ameliorate
cancer proton therapy. It is reported that laser-driven proton acceleration offers a significantly cheaper and relatively convenient approach
to generate a beam of protons and experiments in this direction
indicate that protons in laser proton therapy (LPT) kill cancer cells as
effectively as those from accelerators. Although the biophysical
Abstracts / Physica Medica 30S1 (2014)
studies for laser-driven ion acceleration are still in their infancy, very
promising radiobiological processes are reported, since protons and
photons have a parallel destructive effect on the DNA of the targeted
tumor cells.
In this work we will present the laser-based future objectives for
cancer radiation therapy, aiming to address the relevant advances in
the ionizing and non-ionizing radiation therapy, i.e. protons and heavy
ions therapy, as well as photodynamic targeted and molecular therapies.
THE CONTRIBUTION OF DIFFUSION TENSOR IMAGING AND MAGNETIC
RESONANCE SPECTROSCOPY FOR THE DIFFERENTIATION OF BREAST
LESIONS AT 3T
Ioannis Tsougos a, Patricia Svolos a, Evanthia Kousi e, Evangelos
Athanassiou b, Kiriaki Theodorou a, Dimitrios Arvanitis d, Ioannis
Fezoulidis c, Katerina Vassiou c,d. a Department of Medical Physics, Medical
School, University of Thessaly, Biopolis, Larissa, Greece; b Department of
Surgery, Medical School, University of Thessaly, Biopolis, Larissa, Greece;
c
Department of Diagnostic Radiology, Medical School, University of
Thessaly, Biopolis, Larissa, Greece; d Department of Anatomy-HistologyEmbryology, University of Thessaly Medical School, Larissa, Greece; e CR-UK
and EPSRC Cancer Imaging Centre, Royal Marsden Hospital, Sutton, Surrey,
United Kingdom
Background: Conventional breast magnetic resonance imaging (c-MRI)
combined with dynamic contrast-enhanced MR mammography (DCEMRM), constitute a powerful diagnostic strategy for screening breast lesions. Nevertheless, the high sensitivity of c-MRI and DCE-MRM comes
with low specificity that may lead to ambiguous diagnosis and unnecessary biopsies [1,2].
Molecular MR imaging, such as proton MR spectroscopy (1H-MRS) or
diffusion-weighted imaging (DWI)/diffusion tensor imaging (DTI), has
shown promise as a complementary tool to improve MR specificity and
explore the underlying biological characteristic of tumors, going a step
further from c-MRI.
Purpose: The purpose of the current study was to investigate whether the
combination of 1H-MRS and DTI metrics further contribute to the determination of breast lesion’s aggressiveness.
Materials and methods: Fifty-one women with known breast abnormalities from conventional imaging were examined on a 3T MR scanner. DTI
was performed during breast MRI, and fractional anisotropy (FA) and
apparent diffusion coefficient (ADC) were measured in the breast lesions
and the contralateral normal breast. FA and ADC were compared between
malignant lesions, benign lesions, and normal tissue. 1H-MRS was performed after gadolinium administration and choline peak was qualitatively evaluated.
Results: In the present study 1H-MRS showed a sensitivity of 93.5%,
specificity 80%, and accuracy 88.2%. Choline detection dependence on tumor size was observed.
FA was significantly higher in breast carcinomas compared to benign
lesions (0.24±0.05 and 0.21±0.04, respectively). Mean ADC value was
lower for malignant tumors, however no significant difference was
observed.
The combination of Cho presence and FA achieved higher levels of accuracy (90.3%) and specificity (84%) in discriminating malignant from benign
lesions over Cho presence or FA alone. This correlation between Cho and
FA may be explained based on two factors: (a) Cho is associated with active
cell proliferation and (b) tumor growth, results in higher cell density,
which might cause water molecules to diffuse with a higher degree of
directionality, in contrast to benign lesions.
Conclusion: In conclusion, applying DTI and 1H-MRS together, adds incremental diagnostic value in the characterization of breast lesions and
may sufficiently improve the low specificity of conventional breast MRI.
References:
1. Orel SG et al. MR imaging of the breast for the detection, diagnosis, and
staging of breast cancer. Radiology 2001; 220: 13e30.
2. Yen Y et al. Dynamic breast MRI with spiral trajectories: 3D versus 2D. J
Magn Reson Imaging 2000; 11: 351-9.
5
CHARACTERIZATION OF OCCUPATIONAL EMF EXPOSURE TO MRI
SYSTEMS
E. Karabetsos a, N. Skamnakis a, G. Gourzoulidis b, P. Sandylos c, Chryssa
Paraskevopoulou c, T.G. Maris d, A. Xristodoulou e. a Greek Atomic Energy
Commission, Non-Ionizing Radiation Office, Greece; b Physical Agents
Determination Department, ΚYАЕ (COHS), Ministry of Labor, Greece; c Ygeia
Hospital; d Assistant Professor of Medical Physics, Medical Department,
University of Crete, Greece; e General Director of Health & Safety at
Workplace, Ministry of Labor, Greece
European legislation concerning the protection of workers from exposure to EMF was recently completed by directive 2013/35/ЕU (26.6.2013),
the transposition of which to the national legislations should have been
concluded by July 2016. This directive is a specific one of the framework
directive 89/391/EEC and is part of the overall legislation for Health and
Safety of Workers (HSW). MRI systems have played a key role, both to
the postponement of the former 2004/40 EMF directive and to the formation of the latest ICNIRP guidelines adopted by the new directive. On
the other hand, MRI systems are associated with the exposure of
personnel to various frequencies and modulations, arousing peculiar
safety issues.
It is important to stress out that directive 2013/35/EU excludes, under a
prescribed scheme, MRI systems from the application of the exposure
limits values (ELVs). In the framework of this derogation, increased
surveillance is applied, meaning that the basic issues of HSW are of
key importance. In order for this increased surveillance to apply to
workers and as part of the risk assessment procedure, the knowledge
of the exact occupational exposure levels and scenarios is highly
important. Normally the MRI operator does not enter the examination
room during the MRI scan, but in some cases this is possible. Measurements of the magnetic and electromagnetic fields were performed
during the MRI scans, next to the examination bed and at the operation
console.
Different MRI systems (1,5 and 3T) have been chosen for measurements in
order to access occupational exposure compared to the limit values given
by the directive and to the main principles of HSW. Low frequency exposures resulting from the function of the gradients of the MRI system
(rectangular pulses at the kHz region), as well as high frequency exposures
due to the application of the main RF frequency (pulses in sinx/x envelope
at the MHz region), were measured. One of the most important aspects of
this work, was associated with the post-processing of the measured EMF
signals in order to be comparable to the action level (AL) values of the
directive.
Keywords: electromagnetic fields, MRI occupational exposure, risk
assessment, Health and Safety of Workers.
IMPROVEMENT OF DOSE DISTRIBUTION WITH IRREGULAR SURFACE
COMPENSATOR IN WHOLE BRAIN RADIOTHERAPY
Hideki
Fujita,
Nao
Kuwahata,
Hiroyuki
Hattori,
Hiroshi
Kinoshita, Haruyuki Fukuda. Department of Radiation Oncology, Osaka
Saiseikai Nakatsu Hospital, Osaka, Japan
The aim of this study was to evaluate the dosimetries of whole brain
radiotherapy (WBRT) using irregular surface compensator (ISC) compare
with conventional radiotherapy. The ISC involves modulation of the
beam with the multileaf collimator (MLC), and increases the dose homogeneity to the target volume while decrease the absorbed dose in irradiated tissues outside the targeted tissue. Treatment plans were produced
for 10 patients. All treatments were carried out with 10 MV photon energy
from a Clinac iX with 120 MLC (Varian Medical Systems, Palo Alto, CA,
USA). The prescription dose was 30 Gy in 10 fractions at the isocenter. With
Eclipse treatment planning system (Varian Medical Systems), the anisotropic analytical algorithm was used for the dose calculation. The tissue
heterogeneity correction was used in all the treatment plans. For ISC,
the skin flash tool application was used to extend the optimal fluence.
These two treatment plans were compared in terms of does in the planning target volume (PTV), the dose homogeneity index (DHI), the
maximum doses, eye and lens doses and the monitor unit (MU) counts
6
Abstracts / Physica Medica 30S1 (2014)
required for treatment. Average values were evaluated using the Wilcoxon
signed rank test. Compared with the conventional WBRT, the ISC significantly reduced the DHI, the maximum dose, the volumes received at 105%
of the prescription dose, as well as reducing both eye and lens doses (p <
0.01 for all comparisons). By contrast, the monitor unit counts were
increased for ISC technique compared to the conventional WBRT (819 vs.
327, p < 0.01). The ISC technique for WBRT enables significantly better dose
distribution in the PTV. As patients who receive WBRT have improved
survival, the long-term side effects of radiotherapy become of increasing
important. It is expected that with this technique, the risk of late radiotherapy-associated complication will be reduced. The ISC technique has
been used in select patients with a long life expectancy at our institution.
Key words: Whole brain radiotherapy, Irregular surface compensator,
Dose homogeneity index
CORRELATION BETWEEN EYE LENS AND THYROID STAFF DOSES IN A
CARDIOLOGY CENTRE
N. Kollaros a, Z. Thrapsanioti b, I. Mastorakou a, T. Syrigou a, T. Bagiatis a, E.
Carinou c. a Onassis Cardiac Surgery Center, Syngrou 356 17674 Kallithea
Athens, Greece; b 2nd Department of Radiology, Attikon University Hospital,
Greece; c Greek Atomic Energy Commission (GAEC), P. Grigoriou &
Neapoleos, Ag. Paraskevi, 15310 Athens, Greece
An increased interest has been recently reported on eye lens doses
received by the medical personnel of interventional radiology/cardiology suites. According to ICRP recommendations and the new EU
Directive, for occupational exposure in planned exposure situations, an
equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50
mSv is recommended. In the medical field, interventional radiologists
and cardiologists are among the most highly exposed personnel,
since they stay close to the patient, source of scattered radiation, while
performing complicated fluoroscopically guided interventional
procedures.
The present study aims at examining methodologies for better assessing
eye lens doses of the medical staff involved in all kinds of interventional
cardiology procedures in a cardiology centre. Hp(3) values were assessed
using a specially designed eye lens dosemeter. The results were compared
with the respective values received from dosemeters attached on the
thyroid collar and near the eye region that were both calibrated in terms of
Hp(0.07).
Measurements in more than 170 procedures were performed and 7 operators were monitored. The monitored procedures were: coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA),
pacemaker implantation (PM), radiofrequency ablation (RFA), and paediatric interventions (PI).
High-sensitive MCP-N (LiF:Mg,Cu,P) TL pellets, were used in the present
study. The pellets were placed in plastic bags on thyroid collar of the
physician and the eye region. The eye-lens dosemeter (EYE-D) was also
used with an MCP-N pellet and was worn near the left or right eye of the
physician (depending on the position of the X-ray tube), attached to a
support around the head.
As it was expected a good correlation was observed between the
Hp(0.07) values at the eye region and the respective Hp(3) ones
(R2¼0.952). Moreover, a good correlation was also observed between
Hp(0.07) values at the thyroid with the respective Hp(3) ones
(R2¼0.665).This result can be a very powerful tool for the RPO in order to
assess with a quick and easy way, without disturbing the operator, the
eye lens doses by using the indications of the dosemeters attached on
the thyroid collar.
A survey of soils, collected across Greece, from depths up to 25 cm using
a soil corer, was carried out to determine the environmental gamma
background radiation levels. The materials and the standards were
analyzed using high resolution gamma spectroscopy. A germanium
detector of high purity was used to measure the activity concentrations
of 226Ra, 232Th, the primordial 40K and the artificial radionuclide 137Cs.
The samples were stored for one month, thus equilibrium of 226Ra and
its products was achived. The concentrations of measured radionuclides
showed significant variations. The 226Ra/232Th and the 226Ra/40K concentration rations were also been estimated. The corresponding absorbed dose rates in air from all those radionuclides were been evaluated
too. The mean value did not differ from the average dose rates that past
studies have reported and did not exceed the world wide average
values. All measured values were comparable with other global radioactivity measurements and were found to be safe for public and
environment.
Acknowledgements
This work has been carried with the financial support of the European
Social Fund and national resources through the Public Investment
Program, Research Project ARCHIMEDES III, subproject ΟPS 383572
”Monitoring mycotoxins and radioactivity level in cereal products of
Greece”
EXPOSURE TO NON-IONIZING RADIATION OF THE POPULATION OF
NEAPOLI-SYKIES AREA
Ch. Κoulouris, Ch. Аthanasopoulou, St. Chantzi, Е. МolyvdaАthanasopoulou, А. Siountas. Medical Physics Lab, Medical School, AUTH,
Greece
Introduction: The aim of this paper was to measure the intensity of
electromagnetic fields at the frequency zone of 30 MHz e 3 GHz in the
Neapoli-Sykies municipality.
Method: An isotropic aerial was put on a wooden tripod and fastened
on the roof of a car, whose roof was covered with echo reflecting
pyramids for the absorption of the reflected waves. The aerial was
connected to the spectrum analyser FSH4, R&S, which was inside
the car. Each measurement lasted two minutes while the car was
still. The exact position was acquired using a GPS device. The positions
of measurements were chosen so that they represent the whole area of
the municipality, and having selected places of greater interest, (nurseries, schools) and around mobile phones base stations. During the
measurements special care was taken to stay at a distance of metal
surfaces, cars and buildings so that the maximum intensity was
measured.
The resulting data and measurement values were entered in a geographic
information system and raster data in the region was obtained. Namely,
the Google maps api technology was used, provided by Google Map spatial
server.
Results: In two months, 1.109 measurements of the intensity of electromagnetic fields were acquired at a distance of two meters above ground.
ENVIRONMENTAL RADIOACTIVITY MEASUREMENTS OF GREEK SOILS
N.G. Servitzoglou a, S. Stoulos b, A. Siountas a. a Medical Physics Labatory,
Department of Medicine, School of Health Sciences, Aristotle University of
Thessaloniki, Thessaloniki 54124, Greece; b Nuclear Physics Labatory,
Department of Physics, School of Sciences, Aristotle University of
Thessaloniki, Thessaloniki 54124, Greece
Ă
Abstracts / Physica Medica 30S1 (2014)
The results showed that the intensity was lower than the proposed levels.
The comparison was done using the stricter coefficient of 60 % of the European figures, as the Greek legislation proposes. As the measurements
covered the frequency zone of 30 MHz e 3 GHz, they were compared with
the lowest limit of 21,7 V/m.
A 3-dimensional map was generated from the measured values using the
geographic longitude and latitude. A map overlay, referred to measurements points, was added on top of the Google map. Info Windows displays
information about a particular point of interest and is typically opened just
above a marker.
http://medresearch1.med.auth.gr/emr/
DESIGN AND CLINICAL IMPLEMENTATION OF A 99MTC-HYNICTOCBASED DOSIMETRIC PROTOCOL IN PRRT OF NETS WITH 90Y-DOTATOC
M.T. Chalkia a, A.P. Stefanoyiannis a, A. Prentakis a, S.N. Chatziioannou a, T.
Liotsou a, X. Geronikola-Trapali a, I. Armeniakos a, E.P. Efstathopoulos a, G.C.
Nikiforidis b. a University General Hospital of Athens “Attikon”, Athens,
Greece; b Department of Medical Physics, School of Medicine, University of
Patras, Rion, Greece
Introduction: NeuroEndocrine Tumors (NETs) overexpress somatostatin
receptors’ subtypes sst1-5. The therapeutic effect of Peptide Receptor
Radionuclide Therapy (PRRT) of NETs with 90Y-DOTATOC is based on the
binding of radiolabeled somatostatin analog peptide with these receptors. In pretherapeutic PRRT treatment planning, reliable patientspecific dosimetry is essential to achieve an optimized therapeutic
outcome. In the scope of this study, the NETs’ imaging radiopharmaceutical 99mTc-HYNICTOC was utilized in order to implement a 2dimensional image-based dosimetric protocol for subsequent PRRT with
90
Y-DOTATOC.
Materials & Methods: 725-920 MBq of 99mTc-HYNICTOC were administered at three patients with metastatic NETs. Patient imaging was
based on the conjugate view method. Anterior and posterior wholebody scans were acquired at 0, 2, 4, 5, 24 and 27 h p.i. using a singlehead gamma camera. A SPECT scan was additionally obtained at 4 h p.i.
for depth estimation. After calibration of the gamma camera system,
additional correction factors for attenuation, self-attenuation, scatter
and background activity were determined in order to convert the
regional count rate values to the corresponding activity values. Dosimetric analysis was based on the Medical Internal Radiation Dosimetry
(MIRD) committee schema. The dosimetric protocol was further
enhanced by the introduction of actual organ volumes and by preliminary phantom-based validation of activity and volume estimated
values. The organs’ and NETs’ absorbed doses obtained from 99mTcHYNICTOC imaging were finally converted to 90Y-DOTATOC therapeutic
doses.
Results: Implementation of the presented dosimetric protocol led to the
estimation of NETs and organs of interest absorbed doses for 90Y-DOTATOC. The results are presented in Table 1.
Table 1. Absorbed dose estimates for PRRT with
# Patient
1
2
3
90
Y-DOTATOC.
Mean absorbed doses (mGy/MBq)
LIVER
KIDNEYS
SPLEEN
BLADDER
NETs
1.78
0.37
0.53
1.72
0.54
0.71
4.96
0.60
3.15
1.57
0.47
0.14
d
0.69-1.67
0.17-1.95
Conclusions: The patient-specific dosimetric protocol proposed in this
study can be relatively easily adopted in clinical routine. The dosimetric
results are in agreement with previously published data, demonstrating
the efficiency of the applied protocol. Taking into consideration the significant interpatient dose variations, patient-specific dosimetry seems to
be an essential tool for individual therapy planning.
7
PRELIMINARY INVESTIGATIONS ON EMF EXPOSURES AND PULSE
SEQUENCES AT 3T
Luca Moro a, Francesco Frigerio b, Irene Carne a, Antonio Coppola c. a
Medical Physics Unit, Italy; b Centre for Environmental Reasearch, Salvatore
Maugeri Foundation, Pavia, Italy; c AlphaStudio Lab, Pavia, Italy
Directive 2013/35/EU of the European Parliament and of the Council of 26
June 2013, grants, to MRI, a derogation from the established exposure limit
values of workers to electromagnetic fields, provided that a risk assessment is carried out in accordance with the Directive and, inter alia, the
employer demonstrates that workers are still protected against adverse
health effects and against safety risks.
Accordingly, it must be taken into account the possible instantaneous
stimulation effects at frequencies below 100 kHz, due to gradient
switching, as well as heating due to the absorption of radio frequency.
Different imaging techniques involve different distribution of radiofrequency and application of gradients throughout the examination; in this
work, a first comparison is reported between theoretical considerations,
literature data and measurements on a GE Healthcare Discovery MR750 3.0T.
Indication will be given about the exposure scenarios worth to be
considered from the EMF safety point of view in our clinical experience.
In some sequences as diffusion imaging and 3D angiography, due to the
intensive use of saturation, greater RF exposure is expected; however,
during the prescan, electric field strength of about 43 V/m and magnetic
field of 0.12 A/m, at 3.5 m from the magnet bore have been measured.
These values are in accordance with the far field relation even if the wave
length of the central radiofrequency is 2,34 m and in literature is reported
that only magnetic field should propagate outside the bore.
In pre-scanning greatest exposure to low frequency gradient field can be
detected as the scanner must tune power and frequency.
The claim for faster and increasingly high resolved images drives to the use
of steeper gradients and radiofrequency delivered at higher rates; in order
to devise fast and easy to apply measurements protocols for safety operation of MRI further research on relevant exposure conditions is needed.
ASSESSMENT OF DOSE CONSTRAINTS OF THE ORGANS AT RISK ON HDR
BRACHYTHERAPY OF CERVICAL CANCER BASED ON 3D-CT IMAGES:
DOSE PRESCRIPTION TO THE TARGET VOLUME VERSUS THE POINT A
PLANNING METHOD
~o a,b.
C. Souto a, F. Santos a, M. Fortunato a, G. Fernandez a, M. Rolda
Radiotherapy Department, Portuguese Institute of Oncology of Lisbon
Francisco Gentil, Portugal; b Faculty of Medical Sciences, New University of
Lisbon, Portugal
a
Objective: To compare the dose on organs at risk (OAR), with the dose
prescription to the target volume versus dose prescription to point A, in
the treatment of cervical cancer with high-dose rate 3D images-based
brachytherapy.
Method: The data were obtained by performing dosimetric distributions
(7 Gy per fraction: 3 fractions in the total) to the target volume (CTV),
volume of visible uterus, delineated by Radioncologist using CT images
and also prescribing to the point A, in 57 patients with cervical carcinoma,
with previous external beam therapy to the whole pelvis (50.4 Gy in 28
fractions).The underlying assumptions are: full dose of external beam
therapy in the target volume, identical location during fractionated
brachytherapy and identical method of delineation of the volumes of
interest. In relation to the organs at risk (rectum, bladder, intestines and
sigmoid), CT is a good imaging system, allowing a good view, and so a
good definition of the volumes at risk delineated by Radioncologist. For
these organs the outer contour were delineated. We used the Treatment
Planning System Oncentra Master Plan version 3.3 of Elekta. The linearquadratic radiobiological model-equivalent dose (EQD2) is applied for
brachytherapy and is also used for calculating dose from external
beam therapy. Specific dosimetric parameters are evaluated for OARs
volumes 0.1cc, 1cc and 2cc: D0.1cc, D1cc and D2cc (group of Gynaecology
of ESTRO - GEC-ESTRO-recommendations) and the minimum dose is
recommended.
8
Abstracts / Physica Medica 30S1 (2014)
Results: With the dose prescription at point A there was a dose increase in
about 30% in OARs.
Conclusion: With the dose prescribed to the 3D image-based CT we have
good target coverage (we found that the isodoses at points A include the
volume of visible cervix) and sparing of OARs can be significantly
improved taking into account dose volume constraints for the OARs.
Despite the delineation of volumes of OARS, we continue to report the
recommended points of the rectum and bladder.
etc.) have been created from the retrieved data.
Conclusion: The results of this ongoing project, co-funded by the EU and
Greek National resources, under the framework of the “Archimedes-III”
ELL-Operational Programme, reveal some innovative and promising improvements, in the currently available Pancreas-related Imaging and
Radiotherapy Technology.
IMPROVING THE QUALITY MANAGEMENT SYSTEM OF A PET/CT FACILITY
FOLLOWING THE INNOVATION TENDENCIES RELATED TO PANCREAS
MEDICAL IMAGING AND RADIOTHERAPY AS DEPICTED IN PUBLISHED
INDUSTRIAL PROPERTY DOCUMENTS
E. Markou a, B. Spyropoulos a, M. Kallergi a, b. a Biomedical Engineering
Department, Technological Educational Institute of Athens, Athens, Greece;
b
Biomedical Research Foundation (BRFAA) of the Academy of Athens,
Athens, Greece
Aim: Imaging of the pancreas is critical for diagnostic decision-making and
improved patient outcome. More accurate and faster diagnostic procedures
in the last twenty years have led to slight declines in pancreatic cancerrelated mortality. Despite this and the benefits of adjuvant radiotherapy,
progress in pancreatic cancer diagnosis and treatment has remained
exceedingly slow. It is the purpose of this project to identify the strengths
and weaknesses in pancreatic cancer research by reviewing and presenting
the technical innovation trends related to Pancreatic Medical Imaging and
Radiotherapy, as depicted in published Industrial Property (IP) documents.
Material & Methods: Numerous IP-documents, published during the last
20 years, have been retrieved and evaluated, using the European Patent
Office (EPO) and the US Patent and Trademark Office (USPTO) search-engines. Several specific fields have been searched related to imaging and
therapeutic techniques.
Results: The up-to-date results are synopsized in Table I. Several Patentmappings (publication-year-dependence, Assignee-country, Companies
C. Mantzavinos a, G. Manousaridis a, b, M. Metaxas c, B. Spyropoulos a, S.
Chatziioannou c, d, M. Kallergi a, c. a Biomedical Engineering Department,
Technological Educational Institute of Athens, Athens, Greece; b Greek
Atomic Energy Commission, Athens, Greece; c Biomedical Research
Foundation (BRFAA) of the Academy of Athens, Athens, Greece;
d
Medical School of Athens, National and Kapodistrian University of
Athens
Aim: Positron emission tomography (PET) is now a well established diagnostic modality that is extensively used in oncology, cardiology, neurology,
etc, particularly in combination with computed tomography (CT). The
refinement of standardized performance measurements for PET-CT scanners is an ongoing process. The purpose of this study is the evaluation and
improvement of the Quality Management System (QMS) of a clinicalresearch PET/CT facility in an effort to ensure patient and personnel safety
and optimum performance.
Material & Methods: The starting-point for the QMS is the IAEAguidelines for “Quality Assurance (QA) for PET and PET/CT Systems”.
Additional experimental data have been and are still being acquired,
evaluated and, by employing the developed software-tools, properly
documented.
Results: An overview of the components of the QMS under development is
synopsized in Table I:
Table I. Overview of indicative numbers of processed IP-documents concerning Pancreatic Imaging and Radiotherapy.
Imaging related IP-docs
IP-docs appraised
Radiotherapy (RT) related IP-docs
IP-docs appraised
Multi-detector Computed Tomography (MDCT)
Four-dimensional Computed Tomography (4D-CT)
CT Angiography (CTA)
Endoscopic Retrograde Cholangio-Pancreatography (ERCP)
Endoscopic Ultrasound (EUS)
Radionuclide Imaging (RNI)
Positron Emission Tomography Imaging (PET)
Magnetic Resonance Spectroscopy (MRS)
Magnetic Resonance Angiography (MRA)
Magnetic Resonance Imaging of Pancreas
Endoscopic Retrograde Cholangio-Pancreatography (ERCP)
Optical Coherence Tomography (OCT) (Pancreatic-Biliar)
98
23
91
6
101
201
156
232
109
10
27
3
3D Conformal Radiation Therapy (CRT)
Intensity-modulated RT (IMRT)
Robotic Patient Positioning (RPP)
Volumetric-modulated Arc Therapy (VMAT)
Image-guided Radiation Therapy (IGRT)
Stereotactic body radiation therapy (SBRT)
90
Y Radiotherapy
Radiosensitization
Radiolabeled Antibodies for Therapy
Intra-operative Radiation Therapy (IORT)
Proton Therapy (PT)
Intensity Modulated Proton Therapy (IMPT)
85
107
46
8
43
7
23
46
17
16
197
7
Table I. Overview of the Quality Management System under development
Quality Assurance procedures and components
of the Quality Manual
Definition of responsibilities for QA
Acceptance testing and routine periodic
Quality Control Data and Documentation
PET and CT acceptance testing.
Additional Safety monitoring of Locations, Patients and
Staff
Patients and Staff Dosimetry (''Solidose'' RTI-Electronics ,
TLD-Reader Victoreen)
X-ray/g Energy Spectra (''XR-100T” CdTe Spectral
Analyzer,
AMPTEK)
Experimental verification of the Radiation Protection Xray/gcalculations
E/M-field Compliance measurements (SMC-REMF)
Documentation about Imaging equipment,
test-objects, phantoms, sources etc.
Quality Control of each of the PET and the CT
components and their combinantion
Tests modalities and procedures in the case of
abnormal results
Accuracy of PET/CT image registration Visual
display and hard copy printing
Records of all tests, calibrations and corrective
actions performed
Staff-training documentation (equipment,
Quality Control (QC) procedures etc)
Adverse events Documentation and Reporting
to the competent Authorities
Setting Quality Objectives (QO) and (QI) Quality Indicators Software for QMS technical-managerial data handling
in a PET-CT facility
and documentation
Abstracts / Physica Medica 30S1 (2014)
Conclusion: This ongoing project, co-funded by the EU and Greek National
resources, under the framework of the “Archimedes-III” ELL-Operational
Programme, provides for the means and the methodology to facilitate an
IAEA-compliant and efficient operation of a PET/CT facility.
RADIONUCLIDE THERAPIES (RNTS): WHICH IS THE RADIATION BURDEN
FOR THE CAREGIVERS?
A.P. Stefanoyiannis a, I. Gerogiannis b, S.P. Ioannidou a, W.H. Round c, E.
Carinou d, T. Liotsou a, X. Geronikola-Trapali a, I. Armeniakos a, S.N.
Chatziioannou a. a Nuclear Medicine Unit, University General Hospital of
Athens '' Attikon'', 1 Rimini St, Athens 12462, Greece; b Nicosia General Hospital,
Nicosia, Cyprus; c School of Engineering, University of Waikato, Hillcrest Road,
Hamilton 3240, New Zealand; d Department of Dosimetry, Greek Atomic
Energy Commission, Ag. Paraskevi, Attiki 15310, Greece
Introduction: The contribution of radionuclide therapies (RNTs) to effective patient treatment is widely appreciated. RNTs are beneficial with
respect to tumor response and in improving patients’ quality of life. The
administration of high-level doses has necessitated investigating the potential radiation hazard of corresponding caregivers. The aim of this study
is to systematically review the literature pertaining to radiation exposure
of caregivers of patients undergoing RNTs.
Materials and methods: The study included papers published from 1999
to 2013. Papers with dose measurements of caregivers for various types of
RNTs were included. In these papers, measurements were performed by
utilizing various types of dosimeters. Papers with either outpatient administrations or procedures that require post treatment hospitalization
were included. Papers with results that were not explicit in terms of statistical measures such as mean value or median value and standard deviation or range of caregivers' doses were excluded. Data were classified
according to the applied RNT protocol. Protocol parameters included the
type of RNT, the radionuclide used, the applied protocol of dose measurement, the level of administered radioactivity, the type of dosimeter,
the duration of the study, the study sample and the radiation protection
instructions.
Results: Fifteen papers in total were included in the study. Among them 6
concerned thyroid cancer, 4 В-cell lymphoma, 3 thyrotoxicosis (hyperthyroidism), 1 both thyroid cancer and thyrotoxicosis, and 1 pediatric
neuroblastoma. In the examined papers, the average recorded doses of
caregivers were found to be much lower than the corresponding dose
constraint.
Discussion: It can be concluded that when adequate radiation protection instructions are provided under the supervision and guidance of
experts, the dose to the caregivers can be maintained at very low levels.
Dose measurements were not differentiated according to the type of
dosimeter utilized. Therefore, dosimeter choice depends on protocol
structure and availability issues. With regard to specifying the length of
hospitalization, it is recommended that new criteria, in addition to accounting for the level of residual activity, should be adopted. For situations where the radiation exposure to caregivers is negligible,
outpatient treatments based on specific cost-effectiveness criteria could
be established.
PEPTIDE RECEPTOR RADIONUCLIDE THERAPIES (PRRTS): WHICH ARE
THE DOSIMETRIC DATA FOR THE PATIENTS?
A.P. Stefanoyiannis a, M.T. Chalkia a, I. Gerogiannis b, W.H. Round c, T.
Liotsou a, X. Geronikola-Trapali a, I. Armeniakos a, S.N. Chatziioannou a, E.P.
Efstathopoulos a, G.C. Nikiforidis d. a Nuclear Medicine Unit, University
General Hospital of Athens '' Attikon'', 1 Rimini St, Athens 12462, Greece;
b
Nicosia General Hospital, Nicosia, Cyprus; c School of Engineering, University
of Waikato, Hillcrest Road, Hamilton 3240, New Zealand; d Department of
Medical Physics, School of Medicine, University of Patras, Rion, Greece
Introduction: NeuroEndocrine Tumours (NETs) belong to a relatively rare
class of neoplasms. Nonetheless, their prevalence has increased significantly during the last decades. Peptide Receptor Radionuclide Therapy
9
(PRRT) therapeutic effect is based on the binding of radiolabelled somatostatin analogue peptides with NETs’ somatostatin receptors, resulting
in internal irradiation of tumours. Pre-therapeutic patient-specific
dosimetry is essential for a treatment course with high levels of safety and
efficacy. This study reviews the methods and dosimetric results of PRRT
dosimetry presented in the literature. Focus is given on data concerning
the therapeutic somatostatin analogue radiopeptides 111In-[DTPA0,DPhe1]-octreotide (111In-DTPA-octreotide), 90Y-[DOTA0,Tyr3]-octreotide
177
and
Lu-[DOTA0,Tyr3,Thr8]-octreotide
(177Lu(90Y-DOTATOC)
DOTATATE).
Materials and methods: This study included papers that have performed
dosimetry in adult patients for the therapeutic radiopharmaceuticals 111InDTPA-octreotide, 90Y-DOTATOC and 177Lu-DOTATATE. Furthermore, papers
presented herein were published during the last 15 years (1999 e 2013),
with 177Lu-DOTATATE studies being published during the last 4 years (2010
e 2013). Additionally, selection was limited to papers providing dosimetric
data for at least two regions of interest.
Results: Dosimetric results are provided for tumors, kidneys, red marrow,
liver and spleen, Following Medical Internal Radiation Dose (MIRD) committee formalism, dosimetric analysis demonstrates large interpatient
variability in tumour and organ uptake, with kidneys and bone marrow
being the critical organs. Results are dependent on the image acquisition
and processing protocol, as well as the dosimetric imaging
radiopharmaceutical.
Discussion: The large interpatient variability in tumour and organ uptake stresses the need for personalized therapy planning. Patient-specific
dosimetry in PRRT is therefore needed, in order for the fixed dose regimens to be replaced with patient-tailored therapy planning. Kidney
absorbed doses are higher in PRRT with 90Y-DOTATOC, allowing for
higher 177Lu activities to be administered in 177Lu- DOTATATE therapies.
In order for such dosimetric techniques to be systematically implemented in a busy clinical environment, dosimetry software programmes
may provide an essential tool, as they help in making the procedures less
time-intensive.
QUANTIFICATION STUDY OF IODINE CONCENTRATION AND IMAGE
QUALITY INDEXES IN DUAL ENERGY CONTRAST-ENHANCED DIGITAL
MAMMOGRAPHY
Yi-Shuan Hwang a, Yu-Ying Lin b, Yun-Chung Cheung c, Hui-Yu
Tsai b. a Department of Medical Imaging and Intervention, Chang Gung
Memorial Hospital at Linkou, Taoyuan, Taiwan; b Department of Medical
Imaging and Radiological Sciences, Chang Gung University, Taoyuan,
Taiwan; c Department of Medical Imaging and Intervention, Chang Gung
Memorial Hospital at Taoyuan, Taoyuan, Taiwan
The purpose of this study is to develop calibration method with phantom
to quantify the image quality indexes with dual-energy (DE) contrastenhanced digital mammography (CEDM) techniques as a function of
iodine concentration. Custom-made phantom as illustrated in Fig. 1
composed of 24304 cm acrylic plate with a smaller insert of 9 by 9 cm
contained matrix of four times four holes of 8 mm deep with a diameter of
15 mm where the contrast agent injected was used for the investigations.
Contrast agent containing area density of 0.1, 0.25, 0.5, 0.75, 1, 1.5 ,2, 2.5 and
3 mg iodine per cm2 were included in the study. All the image acquisitions
will be performed on a full-field digital mammography system (Senographe Essential, GE) with dual energy acquisitions. The imaging parameters were Rh/Rh /29 kV/70 mAs for low energy (LE) images, and Rh/Cu /45
kV/176 mAs for high energy (HE) images, respectively. Mean pixel value
(MPV) ratio, contrast, and contrast-to-noise ratio (CNR) were used as image indexes for further evaluating the quantification relationships between the iodine concentration. As we can see in the Fig. 2, MPV ratios
defined as the MPV in the iodine contained area normalized to the MPV in
background went downward as the contrast concentration increased in
the both LE and HE acquisitions through the raw image analyzing. When
evaluating the DE images, MPV ratios increased as the contrast concentration increased. For evaluating contrast and CNR performance, both were
shown as linear functions of iodine area density for LE, HE and DE subtraction images as demonstrated in Fig. 3 and Fig. 4 (R2¼0.70, 0.85 and 0.92
10
Abstracts / Physica Medica 30S1 (2014)
for LE, HE and DE images, respectively for both contrast and CNR). The
calibration results may further serving as a reference for analyzing contrast
enhancement for patient participating the dual energy CEDM procedures.
Fig 4. CNR as a function of iodine area density for LE , HE and DE images.Ă
Fig 1. Custom-made phantom.Ă
A NOVEL NON-INVASIVE METHOD SUBSTITUTING BREAST CANCER
BIOPSIES
N. Martini a, V. Koukou a, P. Sotiropoulou a, C. Michail b, I. Kandarakis b, G.
Nikiforidis a, G. Fountos b. a Department of Medical Physics, Medical School,
University of Patras, 265 00 Patras, Greece; b Department of Biomedical
Engineering, Technological Educational Institution of Athens, Egaleo, 122 10
Athens, Greece
Fig 2. MPV ratios for the LE , HE and DE images.Ă
Dual-energy digital mammography (DEDM), where low- and high energy images are acquired and synthesized in order to cancel out the
tissue structures, may improve the ability of enhancing the visibility of
certain elements (calcifications) in the subtracted X-ray image. According to former researches, microcalcifications are mainly composed
of calcite (CaCO3), calcium oxalate (CaC2O4), and apatite (a calciumphosphate mineral form). It has also been considered that any pathologic alteration (carcinogenesis) of the breast may produce apatite. A
method using a quantitative parameter which characterizes the calcification, such as Calcium/Phosphorus (Ca/P) mass ratio, is of interest.
This method will be able to sufficiently discriminate between malignant
and benign lesions, reducing the need for invasive methods, such as
biopsies. A simulation study, using dual energy method, was accomplished for the determination of Ca/P mass ratio in calcifications in order to distinguish between malignant and non-malignant lesions. In this
study, the Ca/P mass ratio of calcifications larger than 300mm was
calculated. The simulation was performed for hydroxyapatite calcifications, indicating malignancy, and compared with calcite calcifications.
The Ca/P mass ratio appeared to be at least 20% higher in case of hydroxyapatite, indicating that this method can be used in breast cancer
diagnosis.
Acknowledgement
This research has been co-funded by the European Union (European Social
Fund) and Greek national resources under the framework of the “Archimedes III: Funding of Research Groups in TEI of Athens” project of the
“Education & Lifelong Learning” Operational Programme.
USE OF GAFCHROMIC EBT3 FOR CHARACTERIZATION OF DOSE
DISTRIBUTIONS IN INTRAOPERATIVE ELECTRON RADIOTHERAPY
(IOERT)
Fig 3. Contrast as a function of iodine area density for LE, HE and DE images.Ă
es de Oncologia do
Filipa Costa a, Sandra Sarmento a, b. a Instituto Portugu^
~o, Rua Dr. Anto
nio
Porto, Francisco Gentil, EPE, Centro de Investigaça
Bernardino de Almeida, 4200-072 Porto;
b
Instituto Portugu^
es de Oncologia do Porto, Francisco Gentil, EPE, Serviço de
nio Bernardino de Almeida, 4200-072 Porto
Física Medica, Rua Dr. Anto
Abstracts / Physica Medica 30S1 (2014)
IntraOperative Electron Radiation Therapy (IOERT) consists of delivering
a single high radiation dose directly to the malignant tissue, after
the removal of a neoplastic mass, with minimal exposure of the surrounding healthy tissues. Unlike conventional external beam radiotherapy, the dosimetric determinations in IOERT are not based on a
Treatment Planning System (TPS). Treatment planning for IOERT is
limited to manual calculations. The volume to be irradiated is visually
estimated at the operating theatre, and the electron energy is chosen
considering the depth of tissue to be treated and the isodose curves
measured in reference conditions. Software is used to generate isodoses
curves, by interpolation, from the dose profiles measured in a water
phantom. This process is time consuming and does not provide
much detail, especially near the surface. Film dosimetry is generally a
good alternative to obtain 2D dose distributions, when compared with
point dose detector as ion chambers, diodes and others, even though
the use of solid phantoms for electron dosimetry is generally not
recommended.
In this work, we have investigated the possibility of using Gafchromic
EBT3 film and a solid water phantom to obtain complete 2D dose distributions parallel to the beam. This is usually a challenge due to the
effect of air gaps which may easily cause artefacts in the dose distribution. The setup is crucial to obtain good results, particularly near the
surface where the air gap effect is more evident. We studied several
setups and optimized a practical and easy methodology for irradiation
of films parallel to the beam in a solid water phantom. The irradiated
films were digitized and the resultant image processed to obtain
detailed and uninterrupted dose distributions, to be used during a
surgery by the radio-oncologist, for a better visual estimation of the
irradiated volume. Good agreement was observed between the dose
distributions obtained with gafchromic film in a solid water phantom
and with a diode in the water tank phantom, between 1mm below the
surface and 60% isodose, for 9MeV.
THEORETICAL MODELING OF THE DETECTOR OPTICAL GAIN (DOG) AND
THE ANGULAR DISTRIBUTION OF COLUMNAR PHOSPHORS USED IN
MEDICAL X e RAY IMAGING. AN ANALYTICAL METHOD AND THE
APPLICATION TO CSI:TL
11
SYSTEMATIC INVESTIGATION OF THE DOSIMETRIC EFFECT OF BEAM
ANGLES IN IMRT OF THE PROSTATE
Spiridon V. Spirou PhD, George Loudos PhD. Dept. of Biomedical
Engineering, TEI Athens, Greece
Purpose: To systematically investigate how the choice of beam angles in
IMRT of the prostate affects the dosimetry of the PTV and each OAR, as well
as how the dosimetry of each structure is correlated with that of other
structures.
Methods and Materials: Five prostate patients, previously treated with a
5-beam IMRT plan to 86.4 Gy, were selected for this study. Candidate
beams were defined in a 360 arc around the isocenter. Treatment
plans were generated for each set of 5 beams taken out from the set of
the candidate beams. First, all the optimization constraints, as well as
all other algorithmic parameters, were kept fixed as in the clinical
plan. Subsequently, additional constraints were placed on the rectum
and bladder, in order to bring forth any differences between the beam
sets.
Preliminary Results: The methodology described previously has been
manually applied to a single prostate patient for 9 candidate beams,
equally spaced every 40 . Altogether 252 (126 x 2) plans were generated
for this patient. All plans were normalized so that the maximum dose to
the rectal wall is 99%. The envelope DVHs describe all the DVHs obtained
from the 126 plans (Fig. 1). The clinical DVHs may or may not lie within the
envelope because the clinical beam arrangement was not among the 126
examined.
The envelope DVHs for the PTV is fairly narrow, indicating that coverage
was not an issue for this patient, regardless of the beam arrangement used.
However, the envelope DVHs for the rectum, bladder and, especially, the
large bowel are much wider, suggesting that the choice of beam directions
may have a significant impact on the treatment plan. The use of additional
constraints improves the range of DVHs for the rectum, bladder and,
especially, the large bowel.
Conclusion: The choice of beam directions may have a significant impact
on the dosimetry of the rectum, bladder and, especially, large bowel.
Furthermore, the use of additional constraints has the potential to improve
current treatment plans. These may, in turn, affect the patient’s quality of
life and post-treatment disease management.
K. Psichis a, N. Kalyvas b, H. Delis a, I. Kandarakis b, G. Panayiotakis a. a Department
of Medical Physics, School of Medicine, University of Patras, Patras 26500, Greece;
b
Department of Biomedical Engineering, Technological Educational Institution of
Athens, Agiou Spyridonos, 122 10, Egaleo, Athens, Greece
Phosphor screens have been used extensively in medical imaging either in
the form of powdered phosphors or in the form of columnar phosphors. In
digital medical imaging, the broad use of columnar phosphors has lead to
the development of many theoretical models for the propagation of light
inside these phosphors.
A two dimensional model for light propagation inside columnar phosphors has been developed and was used for the prediction of the Detector Optical Gain (DOG) and the angular distribution of these crystals.
DOG is defined as the ratio of the total number of optical photons that
exit the crystal to the total number of x-ray photons that enter the
crystal.
The model for light propagation is based on optical photon propagation
physical and geometrical principles and takes into account the attenuation of x-rays inside the crystal bulk, the conversion of x-ray energy to
optical photon beams, the propagation of these light photon beams
inside the crystal where the multiple reflections on the sides of the
crystal column, the infinite forward and backward reflections as well as
the attenuation of photon beams during these reflections are taken into
account.
This theoretical model was applied to CsI:Tl columnar crystals, it was
compared to results found in literature and good correlation with them
was observed.
It was found that DOG is affected by the length of the columns of the
crystal as well as the incident x-ray energy spectrum. The results of the
angular distribution are in accordance with the theory that the longer
crystal columns have more directional light distribution.
Fig. 1. Envelope DVHs for the PTV (cyan), rectum (pink), bladder (orange) and large
bowel (green). Top row: the optimization constraints are the ones used in the
clinical plan. Bottom row: additional constraints are placed on the rectum and
bladder. The solid black lines are the DVHs obtained using the clinical beam
directions.
12
Abstracts / Physica Medica 30S1 (2014)
ICTP/UNITS: A MEDICAL PHYSICS TRAINING OPPORTUNITY FOR
PHYSICISTS FROM THE DEVELOPING WORLD IN EUROPE
William Ona Rodriguez a, Luciano Bertocchi b, Renata Longo c, Renato
Padovani b. a Presenting author e student at ICTP- Abdus Salam
International Centre for Theoretical Physics and Trieste University, Trieste,
Italy; b ICTP- Abdus Salam International Centre for Theoretical Physics,
Trieste, Italy; c Dept. of Physics & INFN, Trieste University, Trieste, Italy
The Abdus Salam International Centre for Theoretical Physics - ICTP, a
UNESCO educational institution with training initiatives in the area of
medical physics like the well known bi-annual College in Medical Physics
and several ICTP/IAEA training courses, has developed the Master on
Medical Physics programme according to the recommendations of IOMP
and IAEA for the education and the clinical training. IOMP and IAEA are
seeing this initiative as an answer to the growing demand of Medical
Physicists in developing Countries.
The ICTP with the University of Trieste have initiated the Master on
Medical Physics (www.ictp.it/programmes/mmp.aspx), a two-years
training programme in Medical Physics, co-sponsored by the Academy of
Sciences for the Developing World (TWAS).
The Master Programme is designated to provide young promising graduates in physics, mainly from developing countries, with a post-graduated
theoretical and clinical training suitable to be recognized as Clinical
Medical Physicist in their countries. In this first course 13 participants from
Africa, South America, Asia, Europe and Midle East have been selected
among more than 250 applicants.
The Master Programme in Medical Physics consists of basic and
advanced courses and practical and clinical training given by experts in
these fields. In the first year 330 hours of lectures and 230 hours of
guided exercises are devoted to: Anatomy and Physiology as applied to
Medical Physics, Radiobiology, Radiation Physics, Radiation Dosimetry,
Medical Physics Imaging fundamentals, Imaging Detectors, Physics of
Nuclear Medicine, Physics of diagnostic and Interventional Radiology (X
rays, US, MRI, Hybrid systems), Physics of Radiation Oncology, Radiation
Protection and, Information Technology in Medical Physics. There will
be an examination at the end of each course. The second year will be
spent in a medical physics department of the hospitals’ network for a
full time clinical training in radiotherapy, diagnostic and interventional
radiology, nuclear medicine and radiation protection. The clinical
training will be informed by the IAEA recommendations (TCS37, TCS47
and TCS50).
After all courses, the practical and clinical training participants are
required to work on a dissertation to be submitted and defended during
the last month of the programme.
ELABORATION OF PATIENT DRL IN CBCT IN DENTAL PRACTICE
D. Petrov, J. Vassileva. National Centre of Radiobiology and Radiation
Protection, Sofia, Bulgaria
The aim of present study is to perform a national patient dose survey
and to elaborate a DRL in Cone beam CT used for dental purposes. The
patient dose was measured with calibrated KAP dosemeter Diamentor
E2 (PTW Freiburg) with a standart head CT phantom. Also the size of the
radiation field was measured with Gafchromic film. The pilot measurements was performed on two CBCT: NewTomVG and ILUMA e
Imtec 3M. The result data was widely distributed, because of the
different FOV and time of exposure. Complete set of ongoing measurements and analysis will be presented, as well as findings and conclusions.
RADIATION DOSE AND IMAGE QUALITY IN DENTAL CONE BEAM
COMPUTED TOMOGRAPHY
Olivera Ciraj-Bjelac a, b, Danijela Arandjic a, b, Predrag Bozovic a,b, Jelena
Stankovic a, b, Sandra Ceklic a, b. a University of Belgrade, School of Electrical
Engineering, Serbia; b University of Belgrade, Vinca Institute of Nuclear
Sciences, Serbia
Radiation protection, monitoring and dose reduction
Dental examinations are the most frequent type of radiological procedure and account for 21% of the total on a global scale. Individual doses
are small but collective doses cannot be ignored due to the high volume
of procedures. Dental cone beam computed tomography (CBCT) is
increasingly performed for imaging of the dentomaxillofacial region.
The proliferation of this imaging modality involving new system geometries, radiation dose profiles, and image quality characteristics requires methodology both for radiation dose and image quality
assessment. The objective of this work is to evaluate patient dose and
image quality in CBCT and particular model of CBCT Scanora 3Dx
Soredex.
Patent dose were measured using cylindrical 16 cm diameter phantom
for all available clinical protocol using a calibrated dose-area product
(DAP) meter. Collected information on the exposure parameters and
DAP were used to estimate effective dose. Similar methodology as
applied for dose assessment in total 60 patients enrolled. Although a
range of image quality indicators can be measured, one must have in
mind that dental imaging has a few specific requirements as hard tissue
visualisation and excellent spatial resolution, so image quality was
assessed in terms of contrast-to-noise ratio (CNR) using relevant
anatomical detail in clinical images, namely regions with dominate
bone, soft tissue and air.
Depending on the clinical protocol, obtained DAP values for phantom were
in the range 393-2544 mGy$cm2 while corresponding effective doses were
5-391 mSv. For patients, dose levels were 1462±456 (393-2544) mGy$cm2
and 219±58 (73-316) mSv. CNR levels were 14±6 (3-33) and 10±5 (2-29) for
the bone-air and bone-soft tissue, respectively.
The CBCT scanner provides contrast resolution suitable to visualization of
high-contrast morphology in dentomaxillofacial imaging applications at
relatively low dose levels. Important part of this survey is development
and application of methodology for image quality and patient dose
assessment, that can be used in the future optimisation studies as some
examination protocols require higher and some of them lower image
quality. Further activities should be focused on attempts to optimise
exposure factors for CBCT unit and clinical protocols in terms of patient
dose and image quality.
A SIMPLE METHOD FOR THE TRANSFORMATION OF PHYSICAL DVHS TO
RADIOBIOLOGICALLY EQUIVALENT ONES IN HYPOFRACTIONATED
RADIOTHERAPY: DOSIMETRIC AND CLINICAL CORRELATIONS
Zoi Thrapsanioti a, Eirini Karanasiou b, Kalliopi Platoni a, Efstathios
Efstathopoulos a, George Matsopoulos b, Maria Dilvoi a, George
Patatoukas a, Demetrios Chaldeopoulos a, Nikolaos Kelekis a, Vassilis
Kouloulias a, b. a 2nd Department of Radiology, Radiotherapy Unit, ATTIKON
University Hospital, Athens, Greece; b Microwave Laboratory, Computer and
Electrical Engineering, National Technical University of Athens, Greece
Purpose: The purpose of this study was to transform physical DVHs to
radiobiologically equivalent ones and additionally to assess their reliability by correlations of dosimetric and clinical parameters. For this
purpose 50 patients with prostate cancer and 50 patients with breast
cancer, who were submitted to Hypofractionated Radiotherapy, were
examined.
Methods and Materials: All 100 patients were submitted to Radiotherapy at the “ATTIKON” University Hospital. The method used in this
study was based on the use of a Java software. The physical DVH data
were exported from the Eclipse TPS of Varian Medical System and then
were imported in the Java software for the transformation to their
corresponding radiobiologically equivalent. To achieve the transformation, we used mathematical models such as the Linear-Quadratic
Model (LQ-Model) and the Niemierko Model. Then the radiobiological
DVHs were evaluated and their outcome was correlated with acute
toxicity score according to EORTC/RTOG criteria.
Results: The procedure mentioned above was applied to all the 100 patients of this study, by means of 100 radiobiological equivalent DVHs
derived from the transformation. From all 100 DVHs important dosimetric
parameters were exported and correlated with EORTC/RTOG acute toxicity
criteria. As far as concern the prostate radiotherapy, a significant
Abstracts / Physica Medica 30S1 (2014)
correlation between RTOG acute rectal toxicity and dosimetric parameters
such as D50 (P<0.001) and V60 (P¼0.001) was found, for a/b¼10Gy.
Moreover, as far as concern the breast radiotherapy, RTOG acute skin
toxicity and dosimetric parameter V60 were significantly correlated,
calculated for a/b¼10Gy (P<0.001).
Conclusions: Our results suggest that the transformation of physical DVHs
to radiobiologically equivalent ones can constitute a useful tool for the
clinicians, in terms of important dosimetric and clinical parameters. The
tool seems also to be effective and reliable, as far as concern the significant
correlation of dosimetric values with radiation induced acute toxicity.
However, more patients are needed to extract safer conclusions and to
further evaluate the reliability of the suggested tool.
TRACT e BASED SPATIAL STATISTICS IN PATIENTS WITH SMALL CELL
LUNG CANCER
S.E. Benezi a, b, E. Karavasilis c, I.S. Karanasiou a, G. Matsopoulos a, E.
Ventouras d, N. Ouzounoglou a, V. Kouloulias e, M. Papathanasiou e, A.
Foteineas e, Th Soldatos c, Ch Iosif c, E. Efstathopoulos e, N. Kelekis e, D.
Kelekis c. a National Technical University of Athens School of Electrical &
Computer Engineering Microwave & Fiber Optics Laboratory (Room 21.31)
9,Iroon Polytechneiou str., 157 73 Zografou Campus, Athens, Greece;
b
School of Medicine, University of Patras; c Research Centre of Radiology
and Imaging, “Evgenidion” General Hospital, Papadiamantopoulou Street
20, 11528 Athens, Greece; d Department of Medical Instrumentation
Technology, Technological Educational Institution of Athens; e National and
Kapodistrian University of Athens, Division of Radiology-Radiotherapy II
Introduction: The aim of this study was to determine microstructural
differences in cerebral white matter between healthy volunteers and patients with small cell lung cancer (SCLC) before the completion of prophylactic cranial irradiation (PCI).
PCI has become a standard of care for selected patients with limited and
extensive stage SCLC who have shown benefit with systemic treatment.
However, with recent increases in mean overall survival and an increased
number of longer-term survivors, the potential contribution of PCI to the
development of neurocognitive deficits is becoming more clearly
defined. Small cell lung cancer may, even in the absence of
overt intracranial metastatic involvement, adversely affect cognitive
function by mechanisms that are not clearly understood, possibly
paraneoplastic.
Diffusion tensor imaging (DTI) is used to study the structure of ordered
biological tissue. DTI depends on the Brownian motion of water molecules,
which is restricted within the brain by structural barriers including macromolecules and cell membranes. The preferential direction of water
diffusion within cerebral white matter occurs along the axons allowing DTI
to identify the location and direction of white matter tracts.
Material and methods: DTI was performed on 8 patients before PCI
and 9 healthy participants. We evaluated 3-Tesla DTI for white matter
injury employing voxelwise statistics approach. Fractional anisotropy
(FA) maps were calculated for every participant. Tract- based spatial
statistics (TBSS) was used to compare FA maps. TBSS projects the FA
data into a common space through the use of an initial approximate
non-linear registration followed by projection onto an alignment
invariant tract representation (mean FA skeleton). Initial results may
present differences on FA maps of frontal lobe between healthy and
patient group.
Conclusion: It is very important not only to continue research regarding
the cognitive side-effects of PCI on different age groups and at various
stages of disease and treatment but also investigate possible ways to reveal
underlying mechanisms that result in these effects possibly even before
their clinical manifestations; this research direction constitutes one of the
main objectives of the present study.
Acknowledgment
This research has been co-financed by the European Union (European
Social Fund e ESF) and Greek national funds through the Operational
Program “Education and Lifelong Learning” of the National Strategic
Reference Framework (NSRF)- Research Funding Program: THALIS e
NTUA, “Study and Analysis of Medical Data using structural and functional
Magnetic Resonance Imaging procedures (MRI/DTI/fMRI): Assessment of
changes induced by Brain Radiotherapy” (MIS 380151).
13
COMPARISON OF PRACTICE AND PATIENT DOSES IN INTERVENTIONAL
RADIOLOGY AND CARDIOLOGY PROCEDURES PERFORMED IN TWO
UNIVERSITY HOSPITALS
D. Kostova-Lefterova a, b, I. Dyakov a. a National Centre of Radiobiology and
Radiation Protection, Sofia, Bulgaria; b National Cardiology Hospital, Sofia,
Bulgaria
Background: The purpose of this study is to estimate typical patient doses
in angiography rooms in two university hospitals in Sofia, and to compare
them with the established national diagnostic reference levels (DRL) and
published data.
Materials and methods: Prospective patient study was performed for five
X-ray units of four different manufacturers. Four most common procedures
were included: coronary angiography (CA), percutaneous coronary intervention (PCI), lower limb arteriography (LLA) and stent placement in iliac/
femoral artery. Totally 285 procedures were recorded, and for each the
following information was collected: sex, age, weight, and height of patient, frame rate, fluoroscopy time (FT), total number of series/images, and
total dose area product (DAP). DAP in cine mode and cumulative doses
were recorded for two of the systems. In addition, entrance surface air
kerma (ESAK) rates in fluoroscopy and acquisition mode were measured
with a PMMA phantom. Image quality was assessed using DICOM images
by calculation of signal-to-noise ratio (SNR) and contrast-to-noise ratio
(CNR).
Results: Large variations were observed in procedure protocols, resulting
in variations in patient dose: DAP ranges were 5.9-172, 31-498, 2.7-78 and
12-326 Gy.cm2 for CA, PCI, LLA and iliac/femoral artery stent placement
respectively. The mean DAP values varied by a factor of 2 for CA and a factor
of 3 for PCI. Two times difference in mean value of cumulative dose was
found due to the 3.6 fold ESAK rate difference.
Discussion: The mean values of DAP were higher than national DRL (40
Gy.cm2 for CA and 140 Gy.cm2 for PCI) in three of the rooms and lower
for only one room. The mean DAP values of 34 Gy.cm2 for LLA and 65
Gy.cm2 for stent placement were lower compared to the national
and published DRLs. The mean FT was higher than the auxiliary reference intervals for only one system. A possible explanation of the higher
doses is the higher number of acquired images. Image quality was better
for the system with higher doses but sufficient for all systems. Patient
dose recording, establishment of typical doses and comparison with
national DRL demonstrated to be good tool to find potential for optimization.
ESTIMATION OF SECOND CANCER RISK AFTER SPLENIC IRRADIATION
FOR HODGKIN’S LYMPHOMA
K. Kourinou a, M. Mazonakis a, A. Fasoulaki b, J. Damilakis a. a Department of
Medical Physics, Faculty of Medicine, University of Crete, P.O. Box 2208,
Heraklion 71003, Crete, Greece; b Department of Radiotherapy and
Oncology, Heraklion University Hospital, Heraklion 71110, Crete, Greece
Purpose: The second cancer risk estimation after lymphoma irradiation is
important due to the long-term survival of these patients. This study was
conducted to estimate the risk for developing a secondary malignancy
following splenic irradiation for Hodgkin’s disease.
Materials and methods: Twelve patients with Hodgkin’s lymphoma in
the spleen region were examined. Computed tomography images of
patients were transferred to an advanced computerized system
(XiO 4.3.1, CMS, Saint Louis, MO, USA) for three-dimensional radiotherapy planning. All treatments were performed isocentrically with 18
MV photon beams. The organ equivalent dose (OED) for liver, lung,
pancreas and stomach, that were partly included within the treatment
volume, was calculated using differential dose-volume histograms
(DVH). Lifetime attributable risk (LAR) for cancer induction was
assessed using organ, sex and age specific risk factors provided by the
BEIR VII report.
Results: For a typical target dose of 6 Gy, the mean OED to stomach, liver,
pancreas and lung was found to be 1.90±0.41 Gy, 0.23±0.01 Gy, 1.01±0.42
Gy and 0.64±0.08 Gy, respectively. The stomach cancer risk varied from 70
14
Abstracts / Physica Medica 30S1 (2014)
to 443 cases per 105 persons, depending upon the organ dose, patient’s age
at the time of exposure and gender. The corresponding ranges for liver,
pancreas and lung cancer risk were (9-37)x10-5, (202-1276)x10-5 and (2311448)x10-5 respectively.
Conclusion: Splenic irradiation for Hodgkin’s lymphoma always leads to a
relatively increased risk for pancreas and lung cancer induction of more
than one case per 1000 irradiated patients. The risk for developing other
secondary malignancies was found to be much lower.
FAST HISTOGRAM-BASED BRAIN SEGMENTATION FROM T1-WEIGHTED
MR IMAGES USING MORPHOLOGICAL PROCESSING AND GEOMETRIC
CRITERIA
S. Hadjidimitriou a, V. Charisis a, G. Sergiadis a, L. Hadjileontiadis a, V.
Kouloulias b, M. Papathanasiou b, N. Kelekis b, D. Kelekis b. a Department of
Electrical and Computer Engineering, Aristotle University of Thessaloniki,
Greece; bSecond Department of Radiology, University of Athens, Greece
Background-approach: Segmentation of brain from three-dimensional
magnetic resonance (MR) head images has always attracted significant
research and clinical interest. Current MR-based brain segmentation
techniques, although accurate, are complex and time-consuming for
certain applications. This work proposes a fast, automated and accurate
technique for whole-brain segmentation from T1-weighted MR images
towards brain volume measurement for potential identification of statistically significant differences between healthy individuals and
patients.
Method: The proposed approach is based on histogram thresholding
and simple morphological operations and extends the work of Shan et
al. (2002). More specifically, the algorithm consists of three steps. The
first step is to remove the low intensity background noise by applying
Wiener filtering and to perform background thresholding for separating foreground head tissue information. The intensity threshold
value is calculated dynamically and is based on a Rayleigh distribution
approximation. The second step aims to disconnect brain from skull
and other non-brain tissues and is grounded on the assumption that
brain is the largest connected component in the image with similar
voxel intensity levels. In this vein, intensity threshold filtering takes
place followed by morphological erosion for disconnecting brain from
non-brain regions. The majority of non-brain regions are rejected using
geometric criteria that determine the acceptable Euclidean distance
between the centroids of the largest connected component (brain) and
other regions. At last, morphological dilation is applied to recover the
brain area. The third step is to remove the fragments of sinus, cerebrospinal fluid and other non-brain tissues that still remain. Initially,
the voxels are divided into four groups, i.e., G1/G4-low/very high intensity voxels corresponding to non-brain regions, G2/3-medium/high
intensity voxels corresponding to gray/white matter. To remove G1/G4
voxels, two intensity thresholds (low and high) are calculated by
employing the parameters of three Gaussian distributions fitting the
image histogram. Finally, the aforementioned procedure of erosiongeometric criterion-dilation is applied and the final brain region is
extracted.
Results-conclusion: Application of the algorithm on real medical images
exhibited potent results mainly for axial but also for coronal and sagittal
views paving the way for its use towards fast, practical brain volume
estimation and research on significant volume changes.
Shan, Z. Y., Yue, G. H., & Liu, J. Z., (2002). Automated histogram-based
segmentation of T1-weighted three-dimensional magnetic resonance
head images. Neuroimage, 17(3), 1587-1598.
Acknowledgment
This research has been co-financed by the European Union (European
Social Fund e ESF) and Greek national funds through the Operational
Program “Education and Lifelong Learning” of the National Strategic
Reference Framework (NSRF) - Research Funding Program: THALIS e
NTUA, “Study and Analysis of Medical Data using structural and functional
Magnetic Resonance Imaging procedures (MRI/DTI/fMRI): Assessment of
changes induced by Brain Radiotherapy” (MIS 380151).
REALISTIC MC SIMULATED MYOCARDIUM PROTOCOL, INCORPORATING
MOTION IN THE XCAT ANTHROPOMORPHIC MODEL. PRELIMINARY
QUANTIFICATION STUDY.
Paraskevi Liakou a, Panagiotis Papadimitroulas a, George Loudos b, George
C. Kagadis a. a Department of Medical Physics, School of Medicine,
University of Patras, GR 26504, Rion; b Department of Biomedical
Engineering, Technological Educational Institute of Athens, GR 12210, Egaleo
Background: The purpose of this study is to assess the use of Monte Carlo
simulations and computer anthropomorphic phantoms, as a tool to
quantify the degrading effects of organ motion (respiratory and myocardial
contraction) in SPECT myocardium imaging.
Methods and Materials: The GATE Monte Carlo simulation toolkit was
used in this study (v. 6.2), along with the 3D XCAT computational
anthropomorphic phantom of a 75 kg male. The phantom consisted of 510
slices, each of which was divided into 128 128 voxels, with a voxel size of
3.54 mm3. The phantom was filled with a realistic biodistribution of 99mTc
N-DBODC. Two simulations were performed: (a) without organ motion
(static), and (b) with organ motion. For the latter simulation the duration
of the cardiac cycle was set to 1 sec, subdivided into 10 frames. Thirty-six
projections were obtained, spanning a full 360 arc. Image reconstruction
was performed using the MLEM algorithm, with 15 iterations.
Results: As shown in Figure 1, the introduction of motion may significantly
affect the reconstructions. Qualitatively, it blurs the size and extent of the
myocardium, possibly leading to a misdiagnosis of a cardiac defect (Figs 1a
and 1b). Quantitatively, the effect may not always be of the same magnitude and in the same direction. Referring to Fig 1c, the first peak (at a
distance of 12 pixels) occurs in the same location for both simulations, and
the magnitude of the static simulation is higher than that of the motionincluding simulation. In contrast, the location of the second peak (at a
distance of 30 pixels) is different for the two simulations, and the
magnitude of the static simulation is lower than that of the motionincluding simulation. This may present particular difficulties for automated feature extraction and image segmentation algorithms.
Discussion: Image reconstruction varies significantly with organ motion,
necessitating the use of motion correction algorithms. The use of XCAT
phantom and GATE simulations provides an accurate and robust tool to
further study and quantify the motion effects in order to optimize imaging
protocols in SPECT.
Figure 1. Reconstruction of a slice through the myocardium: (a) with motion and
(b) without motion (c) Line profiles along the yellow lines in the reconstructed
images a and b.
Abstracts / Physica Medica 30S1 (2014)
15
IMPACT OF AUTOMATIC TUBE CURRENT MODULATION ON CT DOSE
AND IMAGE QUALITY FROM A VIEW OF NATIONWIDE SURVEY
MEASUREMENT OF EXTRA LOW FREQUENCY ELF ELECTROMAGNETIC
FIELDS IN INDOOR WORKING AREAS
Hui-Yu Tsai a, Yi-Shuan Hwang b, Ho-Ling Liu a. a Department of Medical
Imaging and Radiological Science, Chang Gung University, Taoyuan,
Taiwan; b Department of Diagnostic Radiology and Intervention, Chang
Gung Memorial Hospital at Linkou, Taoyuan, Taiwan
A. Skouroliakou a, P. Kontaxis a, S. Anagnostakis a, S. Triantopoulos a, S.
Tsantis b. a Department of Energy Technology Engineering, Technological
Educational Institute of Athens; b Department of Medical Physics, School of
Medicine, University of Patras
Background: This study aims to survey and investigate the impact of using
the current use of automatic tube current modulation (ATCM) in clinical
applications on image quality and radiation dose.
Materials and methods: CT scanners which used clinical adult
abdominal scanning protocols were surveyed nationwide. If ATCM was
clinically used, the mAs of an average-weight patient's mid-liver image
was recorded to calculate the appropriate volumetric computed tomography dose index (CTDIvol). If ATCM was not applied, CTDIvol were
recorded directly. The CTDIvol for abdominal scanning represented the
average clinical adult abdominal dose in Taiwan. Additionally, a custom
ATCM phantom was designed to survey the radiation dose and image
quality for CT scanners using ATCM. After CT scanning, the recorded
CTDIvol and dose-length product (DLP) values, and investigated image
quality, were compared for turning-on and turning-off ATCM in the
same CT scanner.
Results: Analyses of survey data showed a significant dose decrease for
diagnostic CT scanners between with using ATCM (12±4 mGy) and without
using ATCM (15±5 mGy). Evaluations of the custom phantom showed no
significant difference of CTDIvol, DLP, noise between turning-on and
turning-off ATCM.
Discussion: The use of ATCM effectively reduces dose for diagnostic CT
scanners from a nationwide view. The custom ATCM phantom was suitable
for testing ATCM functions.
Background: Extra low frequency (ELF) electromagnetic fields are
emitted by electrical appliances and domestic electrical wiring installations located in indoor areas. The need for updated measurements
and estimations of ELF-fields levels has been accepted by all National
organizations, towards compliance with international standards and
acquirement of dosimetric data for epidemiological studies. Since
numerous individuals spend 8 hours per day in their office, measurement and evaluation of ELF-fields levels within working environment is
considered of importance.
Material & Methods: The presented study involves the measurement of
ELF-field strength in 50 working areas (i.e. offices of administrative
staff in which more than 80% of its working hour is spent). The electric
equipment located in the aforementioned areas was recorded along
with several characteristics concerning category, type and operational
average time in daily basis. All measurements were performed
with NARDA EFA 300 spectral field meter which is appropriate for
frequency range between 0-100kHz. ELF rms and max values of magnetic field strength were obtained from maximum spots, specific distances from the equipment and employee locations during working
hours, with electrical equipment in both stand by and functioning
modes. Each measurement’s duration was 6 minutes and it was
repeated twice.
Results: Magnetic field strength was dominated from 50Hz fields (Greek
frequency of the electric supply system). Peak values were measured close
to photocopy electric equipment while it was functioning, with magnetic
field strength values up to 0,8mΤ when it was actually operating. On the
other hand, magnetic field strength dropped with when the distance from
the equipment was increased. High values of magnetic field strength were
also measured close to the electrical sub panels but in most cases these
were installed in low occupancy areas. ELF fields from pc central processing units and monitors were in most cases less than 0,1mT at operating
position.
Discussion: Results are generally in accordance with corresponding
measurements performed by other groups. In cases where the values are
high simple reduction methods should be suggested. As maximum and
rms values had considerable differences, it might be advisable to
consider both at dosimetric extrapolations and electric appliance’s
standards.
Figure 1A. custom ATCM phantom was designed and shown as the parts of pelvis
(a), abdomen (b), chest (c), and combined together (d).
MEASUREMENT OF IODINE (I125) RADIOACTIVE SOLID WASTE
DERIVED FROM RADIO IMMUNE ANALYSIS (RIA-IRMA) PERFORMED
ANNUALLY IN ”THEAGENIO” NUCLEAR MEDICINE DEPARTMENT
Kotzassarlidou Maria a, Mone Ioanna b, Giannopulou Katerina a, Kirilidou
Pipintakou
Ageliki a,
Chatzimarkou
Michali a,
Sidiradi
Olga a,
Aikaterini a. a ”THEAGENEIO” Cancer Hospital, Thessaloniki, Greece;
b
Aristotelio University of Thessaloniki, Greece
Figure 2. Noise distribution for chest (a), abdomen (b) , and pelvis as ATCM was
turn on.
Figure 3. Noise distribution for chest (a), abdomen (b) , and pelvis as ATCM was
turn off.
Introduction: I-125 is the preferred radioisotope for tagging antibodies in
radioimmunoassay procedures(RIA-IRMA), resulting in significant volume
of contaminated solid waste, mainly tubes and absorbent paper. I-125 solid
waste management is nuclear medicine physicists’ corcern, which must be
in accordance with Geek Legislation.
Objective: This study aims to present real practice data of I-125 activityconcentation in solid waste derived from radioimmunoassay testsperformedin the Nuclear Medicine Department of ”THEAGENEIO”
Cancer Hospital throughout one year.Brief description of management
program for the above mentioned waste, applied in our department is
given.
Materials and methods: Calibration factor(CF), converting true count rate
to I-125 activity was defined, using a standard source, I-129(equivalent to
16
Abstracts / Physica Medica 30S1 (2014)
46300dpm or 733Bq I-125). Reporting wasbased on data from all assays
performed throughout 2013.Tube count rates, due to I-125 activity measurement, were summed and converted to I-125 activity by use ofCF. Total
number and weight of tubes included in solid waste were reported.Proper
time for decay-in-storage was determined, meeting Greek regulations,
which allow daily solid waste disposal containing I-125, when activity
concentration is below 10Bq/g.
Results: During 2013, 47127 tubes were assayed in ”THEAGENEIO”Nuclear
Medicine Dept. 472 kits (100 tubes each) of RIA-IRMAtests were
consumed, mean valueof I-125traceractivity400kBq/kit. Various hormones
and tumor markers were assayed:FT3,FT4,ICTP,TPA,TAG-72,TRAK,FREE
PSA,IPTH,HTG,FSH,LH,ACTH,DHEA'S,GH,E2,PROL,AFP,B-CG, PSA,NSE,CA199,TESTOSTERONE,TM-AB,TSH,CA15-3,CgA, CA125,CEA,TG-AB, P4 (PROG),ALDOSTERONE,ІNSULIN,CePEPTIDE,RENIN,17ΟНpPROGESTERONE,
CALCITONINE.
Calibration factor (CF) was 45 cpm/Bq.Each tube’s weight is 1.5g, therefore
total weight of solid waste (including bottles containing tracer in the kit)
derived equal to73 kg.Total count rate was 2082932567cpm,leading to a
total activity of I-125 46.5MBq/year and an average value of 982Bq/tube.
According to lab’s practice, wastes of RIA- IRMA tubes are collected every 2
weeks. 24waste packages, 4 kg each, are stored in a dedicated fridge every
year.
Considering Greek Radiation Protection Regulation, (FЕΚ 1014(FΟR)94
216/06.03.2001), each waste package must be kept in storage for 363
days.
Conclusion: Storage of tubes, contaminated with I-125,for one year is
needed before removing them from hospital. Therefore, special storage
space, safe for staff, should be provided in each lab. Waste packages used
must be plastic. Each one must be assigned an I.D. number, initial storing
date, weight, contained activity of I-125, projected date of removal from
storage.
Before disposal each bag is monitored for activity presence. All persons
engaged in this work are trained, ensuring compliance with the department’s procedures.
RADIATION EXPOSURE AND IMAGE QUALITY EVALUATION USING THE
IDOSE4 HYBRID ITERATIVE RECONSTRUCTION ALGORITHM IN
PEDIATRIC CHEST HRCT
Magdalini Smarda a, Efthimia Alexopoulou a, Argyro Mazioti a, Sofia
Kordolaimi a, Agapi Ploussi a, Konstantinos Priftis b, Efstathios P.
Efstathopoulos a. a 2nd Department of Radiology, Medical School, National
and Kapodistrian University of Athens; b Department of Pediatrics, Medical
School, National and Kapodistrian University of Athens
Background: Computed Tomography (CT) radiation exposure has raised
concern, especially in pediatric patients who are more radiosensitive and
have longer life expectancy than adults. Therefore, the use of the recently
developed Iterative Reconstruction (IR) algorithms is particularly significant for dose reduction.
The aim of the study is to compare radiation exposure and image quality
between filtered back projection (FBP) and an IR algorithm (iDose4,
Philips) in pediatric chest High Resolution Computed Tomography
(HRCT).
Materials and methods: A total number of 45 pediatric chest HRCT
examinations were performed on our Department’s 64-detector row CT
scanner before and after the installation of IR algorithm. 21 patients
were scanned using the FBP protocol (FBP group) while 24 patients
were scanned using iDose4 protocol (iDose4 group). The images of
iDose4 group were reconstructed using FBP and all levels of iDose4 algorithm. The tube current-time product (mAs) was reduced for the
iDose4 group while the rest exposure settings (kVp, filtration, pitch)
were kept constant for both protocols. Radiation exposure quantities
(CTDIvol, DLP, ED, SSDE) were evaluated. Image noise was objectively
calculated. Subjective image quality was evaluated by 2 experienced
radiologists in a 5-point scale.. Unpaired t-tests were used for data
statistical analysis. All results were compared on the basis of weight
category (higher of lower than 30kg).
Results: For the low-weight category (<30kg), iDose4 application allowed
an effective dose reduction of about 80%, whereas in the high-weight
category (>30kg) the corresponding reduction was 40%. Comparable results concerning overall subjective image quality between the 2 groups
were achieved with iDose4 level 4 for the >30kg subcategory and with
iDose4 level 6 for the <30kg subcategory of pediatric patients. The corresponding results concerning objective image noise were noticed between
FBP and iDose4 images of levels 3 and 6 for the >30kg and <30kg category
respectively.
Conclusion: The use of the iDose4 iterative reconstruction algorithm in
pediatric chest HRCT enables substantial radiation exposure reduction,
without compromising image quality and diagnostic confidence. Further
evaluation with lower mAs settings is needed in order to draw more
precise conclusions, especially in the high-weighted subcategory of
patients.
QUALITY AUDITS OF SMALL FIELD OUTPUT FACTORS: A MULTI-CENTRE
PILOT STUDY
G. Azangwe, P. Grochowska, J. Izewska. International Atomic Energy Agency,
Vienna, Austria
Background: A new co-ordinated research project (CRP) was launched by
the IAEA for the national audit networks for radiotherapy with the purpose
of developing the methodology for remotely auditing IMRT related QA. The
programme involves three audit steps: (1) remote verification of TPS
calculation of small field output factors relevant for IMRT and audit of MLC
positional performance, (2) audit of single clinical IMRT field dose delivery
and (3) ‘end-to-end’ audit (imaging, planning, dose delivery) for multiple
field IMRT techniques. New procedures and phantoms are being developed
and examined through multi-centre pilot studies involving CRP
participants.
Materials and methods: The CRP has attracted research groups from 14
countries across the world. The first study was conducted for the audit of
beam output of high energy photon beams for five selected field sizes of
22 cm2 to 1010 cm2, defined by an MLC and corresponding to representative segment sizes used for IMRT treatment planning. The beam
outputs calculated by participants’ TPSs were compiled by the IAEA and
compared to the datasets published in literature [1].
Results: The results are available for 29 beam/TPS combinations. The
agreement within 1%-2% between the TPS calculated output and the
literature data was obtained for field sizes > 44 cm2, whereas for field
sizes 33 cm2, the TPS doses were overestimated by 3%-4% as compared
to the literature data.
Discussion: Challenges in TPS commissioning for small fields were highlighted by this study; it may be necessary to correct deviations in the TPS
calculation for small segment sizes in the delivery of IMRT once such deviations are confirmed by careful measurements.
Acknowledgments
D. Followill, S. Kry, D. Thwaites, J. Povall, D. Georg, W. Lechner, M. Tenhunen,
M. Tomsej, A. Carlsson Tedgren, M. Arib, W. Bulski, K. Chelminski, S. Luo,
V. Alves, J. Samper, D. Ekendahl, R. B. Devu, S. Sirimanoroth, S. P. Vinatha.
References:
[1] Followill D.S. et al., The Radiological Physics Center’s standard datatset
for small field size output factors, J. Appl. Clin. Med. Phys., vol. 13, Nr 5,
2012, p. 282-289 (erratum vol. 15, Nr 2, 2014, p. 356-357).
MULTIVARIATE STATISTICAL ANALYSIS OF FACTORS RELATED TO MEAN
ANNUAL INDOOR RADON CONCENTRATIONS OF GREEK DWELLINGS
Dimitrios Nikolopoulos a, Sofia Kottou b, Ermioni Petraki a,c, Efstratios
Vogiannis d, Christos Michail e, Anna Louizi b, Yiannis Chaldeos a, Panayiotis
H. Yannakopoulos a. a TEI of Piraeus, Department of Electronic Computer
Systems Engineering, Petrou Ralli & Thivon 250, 12244, Aigaleo, Greece;
b
University of Athens, Medical School, Department of Medical Physics,
Mikras Asias 75, 11527, Athens, Greece; c Brunel University, Department of
Engineering and Design, Kingston Lane, Uxbridge, Middlesex UB8 3PH,
London, UK; d Evangeliki Model School of Smyrna, Lesvou 4, 17123, Nea
Abstracts / Physica Medica 30S1 (2014)
Smyrni, Greece; e TEI of Athens, Department of Biomedical Engineering,
A.Spyridonos, 12210, Aigaleo, Greece
Url:http://env-hum-comp-res.teipir.gr/
Between 1994 and 2000 a large scale radon survey was implemented
in Greece with calibrated radon dosimeters based on CR-39 polymers.
The dosimeters were exposed for a period of twelve-months.
From the measured dwelling sample, 963 apartments were accompanied with fully filled questionnaires. The questionnaires were
designed according to the international standards so as to account for
factors that would potentially affect mean annual indoor radon
concentrations.
The available questionnaires were rechecked recently during 2012-14
with multivariate statistics in order to quantify possible inter-connections. Important factors were the following: i) area, ii) building levelfloor, iii) ground type, iv) basement, v) building type, vi) construction
year, vii) building walls contact, viii) wall materials, ix) floor materials.
Several multivariate methods were employed in the analysis, namely
(i) Linear Regression Analysis, (ii) One way or multiway ANOVA, (iii)
General MANOVA, (iv) Stepwise Regression Analysis and (v) Principal
Components Analysis. As most significant, it was found that approximately
0.1% of the examined dwellings were associated with outlier radon
concentrations.
Significant were the statistical correlations between indoor measured
mean annual indoor radon concentrations and ”building level-floor” factor,
as well as ”wall materials” factor. The findings of this work provided weak
evidence regarding potential association of the factors ”building type”,
”construction year” and “floor materials” with mean annual radon concentration. Minor was the link with ”building walls contact” factor. It is
important to note, that the employed statistical methods provided significant different results for the relative efficiency of the investigated
factors.
MODELING OF RADON AND PROGENY CONCENTRATION PEAKS IN
THERMAL SPAS: RESULTS FROM THE SEMI-EMPIRICAL APPROACH
FROM SEVERAL SPAS IN GREECE
Dimitrios Nikolopoulos a, Efstratios Vogiannis b, Sofia Kottou c, Yiannis
Chaldeos d, Ermioni Petraki a, e, Panayiotis H. Yannakopoulos a. a TEI of
Piraeus, Department of Electronic Computer Systems Engineering, Petrou
Ralli & Thivon 250, 12244, Aigaleo, Greece; b Evangeliki Model School of
Smyrna, Lesvou 4, 17123, Nea Smyrni, Greece; c University of Athens,
Medical School, Department of Medical Physics, Mikras Asias 75, 11527,
Athens, Greece; d IEEE Student, TEI of Piraeus, Department of Electronic
Computer Systems Engineering, Petrou Ralli & Thivon 250, 12244, Aigaleo,
Greece; e Department of Engineering and Design, Brunel University,
Kingston Lane, Uxbridge, Middlesex UB8 3PH, London, UK
Url:http://env-hum-comp-res.teipir.gr/
Radon and its short progeny (218Po, 214Pb, 214Bi and 214Po) are important
radioactive indoor air pollutants that are well recognised for their impact
on humans. Thermal spas are indoor environments which are identified
as significant sources of human radiation burden due to bathing and
working. Especially the transient radon and progeny concentration peaks
have gained scientific attention because these were associated with
short-term impact in patients and personnel. Between 2007 and 2013,
novel first-order modelling was achieved for the transient concentration
peaks of both radon and progeny. This type of modelling is based on a
dynamical set of first-order differential equations describing radon
generation and decay. These equations are combined with measurements and several reference values constituting a so-called semiempirical approach. Real-data are used as model inputs. These are utilised through numerical modelling and the use of the Levenberg-Marquard method in estimating progeny concentrations in non-measured
time moments. Through these, several exposure and dosimetric quantities are calculated.
In this work, the model will be presented along with several verifications
derived from the spas of Ikaria, Loutraki, and Lesvos Island (Greece). It
worth to note that through this type of modelling several non-easily
17
measured parameters -such as the attachment rate and deposition rate
constants- are retrieved. Attachment rate constants ranged between 0.2
and 55 h-1. Deposition rate constants were found different between the
short-lived radon decay, namely between 0.2 and 8 h-1 for attached nuclei
and 0.4 and 64 h-1 for unattached nuclei. Mean annual effective doses
range between 0.001 mSv and 0.6 mSv for patients and 0.001 mSv and 19
mSv for personnel. Differentiations were observed between the various
spa centers depending on the radon potential of the thermal waters, the
water entrance techniques, the building characteristics and other parameters.
RADON ENTRANCE AND ITS DAILY MOVEMENT INTO A CLOSED
DETACHED OF THREE LEVEL HOUSE
Efstratios Vogiannis a, Dimitrios Nikolopoulos b, Maria Koukou c, d, Sofia
Kottou e, Michail Vrachopoulos c, d. a Evangeliki Model School of Smyrna,
Lesvou 4, 17123, Nea Smyrni, Greece; b TEI of Piraeus, Department of
Electronic Computer Systems Engineering, Petrou Ralli & Thivon 250,
12244, Aigaleo, Greece; c University of Applied Sciences, Mechanical
Engineering Department, Energy and Environmental Research Laboratory,
Central Greece 34400, Psachna, Evia, Greece; d Department of Mechanical
Engineering, TEI of Halkis, 34400, Psachna, Evia, Greece; e Medical Physics
Department, Medical School, University of Athens, Mikras Asias 75, 11527,
Athens, Greece
Url:http://env-hum-comp-res.teipir.gr/
An old house of three levels (ground floor, 1st and 2nd floor connected with
internal stairs) was selected for the investigation of radon entrance and its
daily movement among house levels. An Alpha Guard radon monitor was
situated in the middle of each level. Continuous measurements were taken
for a week period in 10 min intervals. Simultaneous measurements were
taken for pressure, humidity and temperature, and also differences on
pressure and temperature between house floors. Weather data also
recorded during survey period.
Measurement results were investigated for the purpose to discover the
factors that affect radon entrance and movement through house levels.
Main radon entrance indoors is the basement floor and secondary the
building materials. This was due to the type of house selected, constructed
from radon free materials, especially the upper floor. House remained
closed during measurements to eliminate every other factor that affects
radon movement. In the other hand the closed house ensured fixed air
exchange rate which is the major factor that affects radon indoor concentration. Air driven forces due to differences in pressure and temperature were analysed in relation to outdoor air conditions. Weather
conditions strongly affect radon entrance from basement. Indoor air
gradually heated produces an upper stream known as chimney effect,
drives radon from the floor working as vacuum. Movement from down to
upper floor due to chimney effect was found not so strongly depended and
it was probably due to high radon molecular weight.
Radon concentrations in ground floor show a daily variation standard
module. Peaks appeared when the previous described mechanism as
vacuum amplifies the driven forces.
PRELIMINARY STUDY OF DISTRIBUTION OF INDOOR EMR IN GREEK
DWELLINGS
Sofia Kottou PhD Associate Professor a, Dimitrios Nikolopoulos PhD
Associate Professor b, Dionysios Koulougliotis Professor c, Konstantinos
Pouliezos MSc c, Efstratios Vogiannis PhD Director d, Nikolaos Gorgolis TEI
Student b, Roxanne Suzzet Lorilla TEI Student c, Georgios Kefalas TEI
Student c, Sotiria Potozi TEI Student c, Yiannis Chaldeos TEI
Student b, Theodore Sevvos TEI Student b, Ermioni Petraki MSc, PhD
candidate b, Christos Michail MSc, PhD d, Panayiotis Moustanis Assis.
Professor e, Anastasios Kalimeris Assis. Professor c, Panayiotis H.
Yannakopoulos PhD Professor b. a Medical Physics Department, Medical
School, University of Athens, Mikras Asias 75, 11527, Athens, Greece;
18
Abstracts / Physica Medica 30S1 (2014)
b
Department of Computer Electronic Engineering, TEI of Piraeus, Greece,
Petrou Ralli & Thivon 250, 12244, Athens, Greece; c Department of
Environmental Technology, Technological Educational Institute (TEI) of
Ionian Islands, Neo Ktirio Panagoula, 29100, Zakynthos, Greece; d Evangeliki
Model School of Smyrna, Lesvou 4, 17123, Nea Smirni, Greece; e Textiles
Department, TEI of Piraeus, Greece, Petrou Ralli & Thivon 250, 12244,
Athens, Greece
Purpose: The International Agency for Research on Cancer (IARC) recently
published two monographs in which evaluates ‘extremely low-frequency
magnetic fields’ and ‘radiofrequency electromagnetic fields’ as “possibly
carcinogenic to humans (Group 2B)”. In the frame of an air quality study
this work hopes to contribute with outdoor and indoor electromagnetic
field strength measurements.
Material and method: Different electromagnetic sources were investigated in a variety of environmental locations, namely houses and workplaces in urban, suburban and rural areas. Based on the suggestions of IARC
and WHO International EMF Project’s RF Research Agenda, measurement
surveys are conducted to characterize population exposures from all radio
frequency (RF) sources. Emphasis was placed on new wireless technologies, mobile telecommunications and DECT telephony. Up-to-date 80 indoor locations are accessed, performing measurements with a personal
exposure meter (Antennessa, EME SPY 120, Satimo, France) and an Aaronia
spectrum analyser (HF & NF). Focused research has been carried out to
further identify places of interest and to standardize the protocol of
measurements.
Results: Maximal electric field values were below 5 V/m in most cases,
however increased values of up to 3 kV/m were addressed near high
voltage power transmission lines. Wi-Fi frequencies were identified as
the main electromagnetic radiation source indoors, followed by mobile
phone and DECT frequencies whenever the later were ON. Rural areas
presented significantly lower electric field values: approximately 3-5
times lower than those of urban areas. Magnetic field values were in most
cases below 2 mT. Increased values of up to 6 mT were occasionally
observed.
Conclusion: The results of the above study show that people inside a
house are exposed to electromagnetic radiation mainly from the Wi-Fi
modem and the mobile phone and DECT facilities when in use, although,
the intensity depends greatly on the distance.
EMR BACKGROUND MEASUREMENTS IN A SMALL TOWN
Efstratios Vogiannis PhD Director a, Dimitrios Nikolopoulos PhD Associate
Professor b, Sofia Kottou PhD Associate Professor c, Panayiotis H.
Yannakopoulos PhD Professor b. a Evangeliki Model School of Smyrna,
Lesvou 4, 17123, Nea Smirni, Greece; b Department of Computer Electronic
Engineering, TEI of Piraeus, Greece, Petrou Ralli & Thivon 250, 12244,
Athens, Greece; c Medical Physics Department, Medical School, University of
Athens, Mikras Asias 75, 11527, Athens, Greece
url: http://env-hum-comp-res.teipir.gr/
Background Electro-Magnetic Radiation (EMR) measurements were carried out in the urban region of Mytilene town sited on the east side of
Lesvos Island, Greece. More than 50 measurement points were recorded in
accordance to a pre-defined measurement plan based on a GIS. All possible
sources of background EMR were investigated, namely in the frequency
area between 9 KHz e 1.5 GHz.
Point values were organised as measurement network-points on a
generated digital map of the surveyed area. Network point values were
also used to produce a digital map of background EMR in the town using
GIS software. EMR measurements are time-depended according to the
operation scheme of nearby existing base stations. To avoid severe timebias, several repeated measurements were carried out in every
point from which the average value was finally employed. The produced
digital map could be considered more-or-less adequate of the
actual background electromagnetic field in units of electric field strength
(V/m).
Since the distribution of EM base stations varies progressively due
to new installations, power-density changes and other technical
causes, maps delineate profiles adequate only for restricted periods
near the measurements. Due to this fact, different scenarios were
introduced accounting for potential differentiations in the existing EM
base stations network, as for example regarding their power and site.
Putting their new characteristics on existing map GIS software, alternative background map were reconstructed according to the new
conditions.
This work is very useful for policy makers because it offers a scientific basis
after an initial EMR background record, then every new installation could
be checked out from the developed software. This could be a significant
tool for over monitoring taking into account the promulgated rules and
limits for EMR.
Demonstrated map shows points and neighborhoods of high electric field
values up to several V/m. Measurement points were selected, if it is
possible (regarding free area from high constructions) near schools, kindergartens and playgrounds. Findings were impressive for such a small
town and alarming for new installations.
HURST EXPONENT OF RADON PROFILES INDOORS IN ATHENS, GREECE
Temenos Nikos a, Filtisakos Spyridon a, Chaldeos Yiannis a, Nikolopoulos
Dimitrios b, Yannakopoulos Panayiotis b, Petraki Ermioni c, Kottou
Sofia d. a IEEE Student, TEI of Piraeus, Department of Electronic Computer
Systems Engineering, Petrou Ralli & Thivon 250, 12244, Aigaleo, Greece;
b
TEI of Piraeus, Department of Electronic Computer Systems Engineering,
Petrou Ralli & Thivon 250, 12244, Aigaleo, Greece; c Brunel University,
Department of Engineering and Design, Kingston Lane, Uxbridge, Middlesex
UB8 3PH, London, UK; d University of Athens, Medical School, Department
of Medical Physics, Mikras Asias 75, 11527, Athens, Greece
Url: http://env-hum-comp-res.teipir.gr/
Radon and progeny (218Po, 214Pb, 214Bi and 214Po) are important radioactive indoor air pollutants of impact to humans. Radon enters buildings
through gaps around pipes or cables and through cracks in floors. Human exposure depends on building characteristics, local geology and
other parameters. All progeny nuclei may attach to aerosols, dust and
water droplets creating hence radioactive mixtures which enter human
lungs.
This work focused on estimation of Hurst exponents (H) in daily radon
signals collected in dwellings with Alpha Guard. H ranges between 0 < H
< 1 and characterises the persistence properties of the recorded fluctuations. For H ¼ 0.5 there is no correlation between the process increments. As it is well-known, in random walk which models classical
Brownian diffusion the walker follows a random path driven by nonmemory dynamics. Whenever the range is 0.5 < H < 1 it is identified,
then that persistence of the signal (super-diffusion), i.e. if the amplitude
of fluctuations increases in one time interval and it is likely to continue
increasing in the period immediately following. The accumulation of
fluctuations is faster than in classical Brownian motion. On the contrary
the range 0 < H < 0.5 suggests anti-persistence or clustering (subdiffusion), i.e. if the fluctuations increase in one period, it is likely to
continue decreasing during the period immediately following, and vice
versa. Finally at the limit H ¼ 0 it does not grow at all and the signal is
stationary.
Hurst exponents were calculated by the R/S method in order to identify
whether radon dynamics are governed by persistent, anti-persistent behaviour or if they are uncorrelated. We considered also whether the R/S method
verified the values of the H exponent estimated by fractal spectral analysis.
During years 2012-2013, 145 dwellings were accessed and their radon
concentrations were measured. By employing sliding window R/S analysis
of window length eight, Hurst exponents were found to be between the
range of 0.5 < H < 1 in the majority of the situations. The latter finding
indicates persistency.
Abstracts / Physica Medica 30S1 (2014)
IMAGING PERFORMANCE OF A GD2O2S:PR,CE,F SCINTILLATOR COATED
CMOS IMAGING SENSOR
C. Michail a, I. Seferis a, b, I. Valais a, V. Koukou c, N. Kalyvas a, A. Bakas d, G.
Fountos a, I. Kandarakis a. a Department of Biomedical Engineering,
Technological Educational Institute of Athens,122 10 Athens, Greece;
b
Faculty of Chemistry, Wroclaw University, 14F Joliot-Curie Street, 50-383
Wroclaw, Poland; c Department of Medical Physics, School of Medicine,
University of Patras, Rion GR 26504, Greece; d Medical Radiological
Technology, Faculty of Health and Caring Professions / Technological
Educational Institution of Athens, Athens, Greece
Aim: The aim of the present study was to investigate the imaging performance of gadolinium oxysulfide powder scintillators, doped with praseodymium, cerium and fluorine (Gd2O2S:Pr,Ce,F) coupled to a high
resolution active pixel CMOS imaging sensor.
Methods: Gd2O2S:Pr,Ce,F is a non-hygroscopic material, emitting green
light with short decay time. For the purposes of this study, a scintillating
screen with coating thickness of 35.7 mg/cm2, was prepared in
our laboratory from powder (Phosphor Technology, Ltd) by sedimentation
on silica substrates. The CMOS sensor was coupled to the Gd2O2S:Pr,Ce,F
scintillator screen. Imaging performance was obtained by means of
experimentally determined parameters such as the signal transfer properties (STP), the modulation transfer function (MTF) and the normalized
noise power spectrum (NNPS). Measurements were performed using the
standard IEC-RQA5 radiation beam quality (70 kVp).
Results: It was found that the detector response function was linear for
the exposure range under investigation. At 70 kVp, under the RQA 5
conditions, the Gd2O2S:Pr,Ce,F/CMOS combination can resolve 6.88 cycles/mm, at MTF10% and the noise levels were found to decrease from
6.42X10-6 mm2, at 1.38 cycles/mm to less than 2.23X10-6 mm2 at 5.2 cycles/mm.
Conclusion: MTF and NNPS values of the Gd2O2S:Pr,Ce,F/CMOS combination were found with high values suggesting an acceptable imaging
performance showing potential interest for non-CT medical imaging (i.e.
dental radiology) or industrial digital radiography.
Acknowledgement: This research has been co-funded by the European
Union (European Social Fund) and Greek national resources under the
framework of the “ARISTEIA” project MISCIRLU code 1476 of the “Education & Lifelong Learning” Operational Programme.
APPLICATION OF TUMOR BED BOOST BY TWO DIFFERENT METHODS
Zygogianni Anna M.D,Ph.D a, Kouloulias Vassilios M.Sc., M.D,
Ph.D b, Kyrgias George M.D,Ph.D c, Armpilia Christina M.Sc a, Antypas
Christos M.Sc., Ph.D a, Theodorou Kiki M.Sc., Ph.D c, Kouvaris John
M.D,Ph.D a. a Kapodistrian University of Athens, Medical School, 1st
Radiology Department, Aretaieion Hospital, Greece; b Kapodistrian
University of Athens, Medical School, 2st Radiology Department, Attikon
Hospital, Greece; c University of Thessalia, Medical School, Radiotherapy
Department of Larissa, Greece
Aim: We evaluate acute and late radiation toxicity, and the
effectiveness of the radiation therapy of the two radiotherapeutic
hypofractionated schedules using two different planning techniques of
delivering radiation boost using 3D conformal radiation therapy
(3DCRT).
Method: Eight one patients were studied, between May 2004 and
December 2010. The patients were retrospectively selected regarding with
either concomitant (group A) or sequential (group B) boost for tumor bed
in two groups. In the first group, 27 patients received 2.3 Gy up to 46 Gy in
the whole breast tissue and it was added a concomitant boost covering
tumor bed as a second daily fraction of 0.4 Gy, so that the total tumor bed
boost was 54 Gy. In the second group, 54 patients received radiotherapy
with a total prescription dose of 53Gy by 2.65Gy per fraction, in 20
fractions, over 25 days. The last four fractions were delivered as a
19
sequential tumor boost. Using the linear quadratic model, BED has been
calculated for the whole breast dose and total boost dose volumes. These
values in the first radiotherapy regimen used were 72.5 Gy4 and 90.5 Gy4 ,
respectively. In the second one they were 70.5 Gy4 and 88.1 Gy4,
respectively.
Results: The statistical analysis of the comparison between the two
methods, showed that cosmetic results, in terms of skin toxicity score, was
significantly worse in integrated boost group, for time ranging from the
completion of radiotherapy until 12th months thereafter. After the first
year post irradiation the toxicity was reduced to minimum in both groups,
while the Kruskal-Wallis H Test showed a significant (P<0.05) superiority
of group B in skin toxicity in terms of overall follow-up. With a median
follow up of 24 months, no patient showed local or regional disease
recurrence.
Conclusions: There were significant differences in the scoring of erythema, in patients receiving an incorporated boost compared with patients
treated by sequential boost. The higher skin reactions were observed in the
group with the concomitant boost and especially identified in the application area of the intergraded boost. This can be avoided by the application
of IMRT technique whereas the dose distribution is more smooth and
homogeneous
SOFT-TISSUE MATCHING METHODS FOR LUNG CANCER RADIOTHERAPY
- BENEFITS, LIMITATIONS AND MARGIN DETERMINATION
Fatma Rahma a, b, Wiviann Ottosson a,c, Claus F. Behrens a, David
€ stro
€ m a, Patrik Sibolt a. a Department of Oncology, Radiotherapy Research
Sjo
Unit, HerlevHospital, University of Copenhagen, DK-2730 Herlev, Denmark;
b
Department of Medical Radiation Physics, Clinical Sciences, Lund
University, Sweden; c Center for Nuclear Technologies, TechnicalUniversity
of Denmark, DTU Risø Campus, DK-4000 Roskilde, Denmark
Background: The purpose of this study was to evaluate five different CBCT
semi-automatic soft-tissue match methods for lung cancer patients and to
calculate the corresponding CTV to PTV margins, both for primary tumor
and lymphnodes.
Material and methods: For 23 lung cancer patients (16 NSCLC, 7 SCLC)
treated with radiotherapy, 135 weekly CBCT set-up images were retrospectively matched to the planning CTs byfive different match methods
using the registration software Offline Review, version 10.0 (Varian
Medical Systems). Four match methods utilized the volume of interest
(VOI) of the 4DCT defined GTV, including the internal motion (GTV-T/
IM), plus a 2, 5, 10 or 20 mmsymmetrical margin, respectively. The fifth
match method used a square VOI enclosing the GTV-T with a 10 mm
symmetrical margin. An intensity range of [-150;150] HU was used for
automatic soft-tissue matches. Residual GTV-T/IM set-up deviations in
all directions were studied for each match and PTV-T margins were
calculated. Additionally, stable surrogates close to GTV-N was used for
the residual GTV-N set-up deviation measurements and PTV-N margin
calculations.
Results: All match methods gave similarresidual GTV-T/IM set-up deviations, ranging between [0;3] mm (62 % within 0-1 mm, 34 % within 1-2
mm, and 4% within 2-3 mm), resulting in [5.2;5.8] mm PTV-T margins.
Match methods utilizing larger VOIs were more stable compared to match
methods using smaller VOIs. Auto match on small targets (<3 cm3) was
problematic, and not possible for match method 5. For 77 % of the patients
with lymph nodes, the main bronchi area was a suitable stable surrogate.
For the remaining lateral GVT-Ns the aortic arch and the main pulmonary
artery were suitable as surrogates. Residual GTV-N set-up deviations
ranged between [-8;10] mm resulting in PTV-N margins between [6;9.8]
mm.
Discussion: Forsemi-automatic soft-tissuematch on the primary tumor,match within GTV-T/IM witha 10 or 20 mmmargin extensionused as
matching VOIs were most appropriate. For small tumors (<3 cm3),
matching manually on GTV-T/IM itself is advisable. The main bronchi
area is a suitable surrogate primarily for centrally positionedmediastinal
GTV-N.
20
Abstracts / Physica Medica 30S1 (2014)
Results: The results derived by the simulations with GATE, were then
compared to the experimental data obtained by the NEMA NU-2-2001
protocol. Scatter fraction, count loses and randoms were the main points of
interest.
Discussion: Good agreement was observed between the results of the
experimental data and GATE simulated results.
ASSESSMENT OF DOSE ADMINISTRATION CONSISTENCY IN PET/CT
N. Sgouros a, T. Stroubinis a, A. Samartzis a, P. Rondogianni a, I.
Datseris a. a Department of Nuclear Medicine, Evangelismos General
Hospital, Athens , Greece
Background: In this work we assess the consistency of the dose administration process of 18F-FDG in the PET/CT establishment of Evangelismos
General Hospital. In detail, we retrospectively assess the dose administration accuracy for a three year period and evaluate the dose consistency
over two shifts. Both shifts utilized an ANZAI medical semi-automated
dispenser. In the first shift trainees are supervised by experienced medical
physicists while in the second shift dose administration was performed by
experienced professionals.
Materials and methods: The data utilized in this study were collected
from 2011 through the end of 2013 and were properly anonymized by
removing patients’ demographic details. The resulting sample after
removing invalid entries contains 4038 records.
In order to robustly assess the administration accuracy the initially prepared (PD ) and syringe residual doses (RD ) were measured and the
nominal dose (ND ) for each patient was calculated. In order to provide a
robust and simple measure we utilized ratio r calculated by Eq. 1 and
already proposed by the authors.
r¼
Figure 1. GTV-T/IM residual deviation after 3DOF soft-tissue match (utilizing GTV-T/
IM plus a 2, 5, 10 and 20 mm symmetrical margin, and square VOI enclosing the
GTV-T with a 10 mm symmetrical margin).
PD RD
ND
(1)
Results: In order to examine the accuracy of dose administration the
Shapiro e Wilk test is us ed for testing normality of the r values distributions prior to using the t-test. The mean values, standard deviations and
the p-values for the Shapiro - Wilk test and the t-test are summarized in
Table 1.
Table 1. Calculated Statistics
MODELLING BIOGRAPH 2 PET/CT SCANNER WITH GATE
D. Nikolopoulos a, I. Valais b, C. Michail b, S. Kottou c, N. Chatzisavvas a, P.
Yannakopoulos a, V. Malaxianakis b. a Department of Computer Electronic
Engineering, Technological Education Institute of Piraeus, Greece, Petrou
Ralli & Thivon 250, 122 44, Aigaleo, Athens, Greece; b Department of
Biomedical Engineering, Technological Educational Institute of of Athens,
Agiou Spiridonos, 12210, Aigaleo, Greece; c Medical Physics Department,
Medical School, University of Athens, Greece
Background: A commercial PET scanner (Siemens, Biograph 2) previously
tested through experiments according to the NEMA NU-2-2001 protocol,
was simulated, using the GATE v.6.1 open source software.
Materials and methods: The study aimed: (a) to port previously
developed and validated GATE codes to the more stable version of
GATE v.6.1; (b) to evaluate the overall applicability and validity of the
model and to investigate potential sources of bias (c) to examine
possible alterations in the results caused by different employed sources,
i.e. F-18 (Fluorine-18), O-15 (Oxygen-15) and C-11 (Carbon-11). All
modules of the Biograph 2 scanner were described in GATE, namely
the detector ring, crystal blocks, PMTs, shielding, electronics etc. In
addition, the energy and spatial resolution of the employed detectors
and their contribution to the overall system’s efficiency were taken into
account.
Groups
Mean value
Standard
Deviation
p-values
Shapiro - Wilk
t-test
Trainees
Professionals
0.9849
0.9882
0.054
0.043
0.2538
0.3102
0.8539
As shown in Table 1 both group samples follow the normal distribution
(p>0.05) and have mean values very close to unity which is in line with
the design of quantity r . Furthermore, comparison of the standard deviations qualifies both samples for the t-test. The t-test shows (p>0.05)
that the two populations have normal distributions with equal mean
values.
Discussion: The results show that there is no significant difference in dose
administration distributions between trainees and professionals. This fact
is attributed in part to the semi-automated dispenser used in the process
and in part to the standardization of the process and supervision of the
medical physicists during the shift where trainees administer the doses.
Hence consistent and homogeneous dose administration is achieved
throughout both shifts assuring proper dose delivery to the patients of the
PET/CT setup.
Abstracts / Physica Medica 30S1 (2014)
ENERGY AND ANGULAR DEPENDENCE OF THERMOLUMINESCENT
DETECTORS IN THE DENTAL CBCT ENERGY RANGE.
a
a
b
Andreas
Stratis ,
Reinhilde
Jacobs ,
Ria
Bogaerts ,
Hilde
Bosmans b. a Katholieke Universiteit Leuven, Department of Imaging and
Pathology, OMFS-IMPATH Research Group, Campus St. Raphael,
Kapucijnenvoer 33, Leuven 3000, Belgium; b University Hospitals of Leuven,
Herestraat 49, Leuven 3000, Belgium
Background: This work is part of a research study on the validation of
a Monte Carlo dosimetry tool dedicated for patient specific dosimetry
in dental Cone Beam CT. An investigation towards the angular and
energy dependence of TLDs, intended to be used for in vivo skin
dosimetry in dental CBCT and validate the framework, was carried out
to examine their response at different angles of exposure and kV
settings.
Material and methods: The HVLs of two CBCT units (3D Accuitomo
170, Soredex Scanora 3D) were measured and their spectra were
simulated by adding Al filters to the window of a general radiology xray tube (Philips SRO 2550). An in house built experimental set up
was used to mount the TLDs and rotate them from 0 up to 80 in 20
steps, at 85 and at 90 (Figure1). Twenty four field TLD-100
dosimeters, calibrated with a Sr-90/Y-90 source resulting in Element
Correction Coefficients ranging from 0.85 to 1.1, were used in the
experiment and the readout was performed by a Harshaw 6600-plus
reader. Six pairs of TLDs were exposed in air at 80kV up to 100kV (in
5kV steps) and at 110kV with a tube current of 200mA and
exposure time of 500msec at each angular step. The mean dose
reading of each pair was then compared to the air kerma measured
with an ionization chamber (Farmer FC65-G, IBA Dosimetry) at the
same location.
Results: Conversion factors were produced for each kV and angle of
exposure (Table 1, Figures 2.1-2.4). The Pearson’s parametric test was
applied to examine any correlation in the response of TLDs with the
exposure angle and the beam energy. The statistical analysis showed that
there is neither energy dependency at each angular step (-0.16<r<0.2 for
Accuitomo, -0.19<r<0.19 for Scanora), nor angular dependency at each
energy step up to 80 (-0.19<r<0.2 for Accuitomo, -0.15<r<0.19 for
Scanora).
Discussion: Based on the resulting independency, there is no need to apply
correction factors as the tube rotates around the patient. However, for
higher angles up to 90 a gradual decrease in the response of TLDs is
observed which may occasionally necessitate the introduction of specific
conversion factors.
21
(continued )
Conversion factors - 3D Accuitomo 170
kV
Anglew
0
95
1.048
100
1.059
110
1.026
Conversion factors
kV
Angle
0
80
1.037
85
1.055
90
1.101
95
1.059
100
1.092
10
1.014
20
1.023
1.017
1.040
- Soredex
20
0.997
1.012
1.060
1.018
1.031
1.014
40
60
1.056
1.023
1.058
1.051
1.081
1.046
Scanora 3D
40
1.050
1.050
1.095
1.085
1.030
1.053
60
1.000
1.020
1.071
1.045
1.012
1.022
80
85
90
1.039
1.044
1.032
1.238
1.241
1.297
1.576
1.538
1.623
80
1.024
1.041
1.090
1.046
1.091
1.011
85
1.190
1.253
1.316
1.222
1.303
1.193
90
1.604
1.537
1.330
1.654
1.446
1.500
Figures 2.1-2.4. Energy and angular dependence of TLDsĂ
BIOLOGICAL VERSUS PHYSICAL BASED OPTIMIZATION FOR VMAT AND
IMRT TREATMENT OF PROSTATE AND HEAD-AND-NECK CANCER
Maria Andreou a, Sofia Kordolaimi a, Efi Koutsouveli b, Panagiotis
Sandilos b, Constantinos Dardoufas c, Evangelos Georgiou a, Pantelis
Karaiskos a, b. a Medical Physics Laboratory, Medical School, University of
Athens; b Medical Physics Department, Hygeia Hospital, Athens, Greece;
c
Department of Radiation Oncology, Hygeia Hospital, Athens, Greece
Figure 1. Experimental set upĂ
Table 1. Conversion factors
Conversion factors - 3D Accuitomo 170
kV
80
85
90
Anglew
0
20
40
60
80
85
90
1.026
1.007
1.084
1.082
0.961
1.027
1.094
1.024
1.072
1.035
0.998
1.100
1.068
0.999
1.061
1.354
1.214
1.264
1.645
1.465
1.748
(continued on next page)
Keywords: VMAT, IMRT, head and neck, physical optimization, biological
optimization, Monaco
Volumetric modulated arc therapy (VMAT) is a novel form of Intensity
Modulated Radiation Therapy (IMRT) that allows more degrees of
freedom such as variation of dose rate, gantry speed and collimator
angle in addition to dynamically changing field shape. The purpose of
this study was to compare two different optimization approaches used
for IMRT and VMAT treatment for two cancer types: prostate and headand-neck cancer. Ten prostate and ten head-and-neck patients were
studied respectively. Different plans were created for every patient,
using two different optimization approaches: a) biological cost
functions and b) Dose-Volume-Histograms (DVH) functions using a
commercially available treatment planning system (Monaco, Elekta).
22
Abstracts / Physica Medica 30S1 (2014)
Plan comparison was performed in terms of delivery efficiency, target
coverage and critical organ protection by utilizing physical (DVH values,
conformity index-CI, target dose inhomogeneity- TDI, gradient index- GI)
and radiobiological indices (tumor control probability- TCP, normal tissue
complication probability- NTCP). Results of the different plans were
compared using the two-sided Wilcoxon matched-pair signed rank test
with a threshold of p ¼0.05 for statistical significance. Overall, high quality
plans in terms of target coverage and critical organ protection were provided by the two different optimization approaches although differences
between the compared plan approaches exist, respectively for each case.
All plans had comparable target dose coverage, conformity and gradient
indexes, with VMAT plans presenting increased delivery efficiency
compared to the IMRT ones. Concerning organs at risk (OARs) the optimization approach based on the biological cost functions was found superior to the conventional one using DVH functions for both prostate and
head and neck cases. In conclusion, biological optimization can generate
superior plans in terms of OARS sparing using either IMRT or VMAT
technique.
RADIATION EXPOSURE OF CAREGIVERS OF PATIENTS UNDERGOING PRRT
WITH 177LU-DOTATATE FOR THE TREATMENT OF NEUROENDOCRINE
TUMORS
S.P. Ioannidou a, A.P. Stefanoyiannis a, E. Carinou b, S.N. Chatziioannou a, T.
Liotsou a, A. Prentakis a, E.P. Efstathopoulos a. a Department of Nuclear
Medicine, University General Hospital of Athens'' Attikon'', 1 Rimini St,
Athens 12462, Greece; b Greek Atomic Energy Commission, Ag. Paraskevi,
Attiki PO Box 60092, 15310, Greece
Background: The potential radiation hazards of caregivers of patients
undergoing Radionuclide Therapies (RNTs) has been investigated in
several clinical trials. However, the respective literature regarding measurements in Peptide Receptor Radionuclide Therapies (PRRTs) is scarce.
Aim: We sought to assess the radiation exposure of caregivers of patients
undergoing PRRTs with 177Lu-DOTATATE for the treatment of Neuroendocrine Tumors (NETs), as well as to compare theoretically calculated and
real recorded doses.
Materials and methods: The radiation exposure of 11 caregivers of patients undergoing PRRT between November 2013 and March 2014 in
''Attikon'' university hospital was assessed. The personal doses were
measured for 7 consecutive days after treatment using thin layer thermoluminescent dosemeters (MCP-Ns TLDs). The administered dose was
around 7400MBq. Exposure rate for specific distances and time intervals
was used to calculate the theoretically expected doses to caregivers and
the effective half life time (Teff). The mean daily consumption of liquids by
the patients was compared to the caregivers' doses.
Results: The mean total recorded dose of caregivers was 0.1 mSv (range:
0.00-0.29 mSv); around 70% of which was recorded at the first 3 days after
treatment. The mean expected dose was 0.78 mSv (range: 0.16-1.59 mSv).
The mean daily consumption of liquids by the patients at the same time
interval was 2.1 lt (range: 1.0-3.5 lt). The mean Teff was 19 h (range: 9-30 h).
Conclusions: The recorded doses to caregivers were considerably lower
than the established dose constraints for people assisting patients, when
radiation protection instructions are followed by both patients and their
caregivers. The theoretically calculated doses were found to be slightly
higher than the recorded, but still at very low levels. A 3 or 4-day period of
implementation of radiation protection instructions appears sufficient to
ensure low radiation exposure to the caregivers. In addition, daily consumption of 2 liters of liquids was associated with the observed very low
radiation exposure of caregivers. Effective half life time varies among patients, indicating the necessity for individualized radiation protection instructions. Further studies with larger samples are warranted to confirm
our results.
X-RAY LUMINESCENCE EFFICIENCY AND DETECTOR QUANTUM GAIN OF
LUPO4:EU NANOPHOSPHOR
I.E. Seferis a, C.M. Michail b, J. Zeler a, I.G. Valais b, T. Sideras b, P.F.
Liaparinos b, N.I. Kalyvas a, G.P. Fountos b, A. Bakas c, I.S. Kandarakis b, E.
Zych a. a Faculty of Chemistry, Wroclaw University, 14F Joliot-Curie Street,
50-383 Wroclaw, Poland; b Department of Biomedical engineering,
Technological Educational Institute of Athens, 12210 Athens, Greece;
c
Department of Medical Radiological Technology, Technological Educational
Institute of Athens, 12210 Athens, Greece
Background: Recently lanthanide orthophosphates (LnPO4) have been
considered as good hosts for rear earth doping to produce phosphors.
Lutetium orthophosphate (LuPO4) has attract the attention because of the
high density (9.4 gr/cm3) and the high atomic number of Lu (Z¼71) which
imparts LuPO4 with high stopping power for ionizing radiation. The purpose of the present study was to experimentally evaluate parameters
related to the light emission efficiency of a 32.4 mg/cm2 powder nanophosphor screen of europium doped LuPO4 (LuPO4:Eu), under radiographic imaging conditions. Parameters such as the X-ray Luminescence
Efficiency-XLE (Light energy flux over incident X-ray energy flux), Detector
Quantum Gain-DQG (optical quanta emitted per incident X-ray quantum)
were evaluated.
Materials and methods: The hydrothermal synthesis of LuPO4:5%Eu was
performed using water solution of Lu(NO3)3 and (NH)4HPO4 in pH¼2. The
process was executed at 230 C for 10 hours. The raw powder was
separated from the solution, washed and dried. Finally, post-fabrication
heating was completed at 1350C in air. Despite the high-temperature
treatment a submicron size of grains was maintained with average
diameter of about 500 nm. The experimental setup used for the evaluation of XLE and DQG comprised a light integration sphere (Oriel 70451)
coupled to a photomultiplier (EMI 9798 B) with an extended sensitivity
S-20 photocathode, enclosed within a bronze light tight chamber. The
detailed experimental procedure is described in previous work of our
group [1].
Results: DQG and XLE were found to decrease as the X-ray tube voltage
was increased. This behavior is affected by the X-ray energy, since the
absorption properties of X-rays, are reduced as a function of energy for the
exposure conditions under consideration. The increasing part of those
graphs from 70 to 80 kVp is attributed to the K- absorption edge of the
LuPO4:Eu scintillator.
Discussion: LuPO4:Eu appears to be a very interesting material for X-ray
medical imaging. Although the screen is not optimized for use under
radiographic conditions the results are very promising and certainly
indicate broader and more thorough research on this material.
References
I. Seferis, C. Michail, I. Valais, J. Zeler, P. Liaparinos, G. Fountos, N. Kalyvas, S.
David, F. Stromatia, E. Zych, I. Kandarakis, G. Panayiotakis, “Light emission
efficiency and imaging performance of Lu2O3:Eu nanophosphor under Xray radiography conditions: Comparison with Gd2O2S:Eu,” Journal of
Luminescence 151, 229-234, (2014).
Acknowledgement
This research has been supported by the Marie Curie Initial Training Networks (ITN) action under the LUMINET project, grant agreement no. 316906.
A NEW APPROACH IN DUAL ENERGY MAMMOGRAPHY USING AN
ACTIVE PIXEL CMOS DETECTOR
V. Koukou a, N. Martini a, P. Sotiropoulou a, C. Michail b, I. Kandarakis b, A.
Bakas c, E. Kounadi d, G. Nikiforidis a, G. Fountos b. a Department of
Medical Physics, Medical School, University of Patras, 265 00 Patras,
Greece; b Department of Biomedical Engineering, Technological Educational
Institution of Athens, Egaleo, 122 10 Athens, Greece; c Medical Radiological
Technology, Faculty of Health and Caring Professions Technological
Educational Institution of Athens, Athens, Greece; d Health Ministry, SEYYP,
Pireos 205 str, 11853, Athens, Greece
Background: Dual energy X-ray mammography can suppress the contrast
between adipose and glandular tissues and improve the detectability of
microcalcifications (mCs). Two digital images that have been obtained with
two different X-ray spectra, for the low- and high- energy, are used.
Weighted subtraction of the logarithmic transform of these images is then
performed to obtain a hybrid image that enhances microcalcifications. In
this study, contrast-to-noise ratio (CNR) is calculated and evaluated in the
subtracted images of mCs in breast tissue.
Materials and methods: A breast tissue equivalent phantom was constructed with Plexiglas slabs (total thickness 4cm) and a mixture of
Abstracts / Physica Medica 30S1 (2014)
hydroxyapatite (36.7%) and epoxy resin (63.3%) representing microcalcifications, ranging from 29 to 50mm. The phantom was doubly exposed to
a prototype digital radiographic unit using a CMOS based imaging detector.
The CMOS scintillator screen was Gd2O2S:Tb with surface density of 33.91
mg/cm2, placed in direct contact with the sensor. The pixel size of the sensor
was 22.5mm. The total entrance surface dose was kept below 1mGy. The CNR
of the subtracted images, obtained with the dual-energy algorithm (CNRDE),
was compared with the CNR of the corresponding low energy image.
Results: The results showed that a combination of 40 kVp and 70 kVp radiographs, for the low- and high- energy respectively, provides the best compromise between CNR and dose in the subtracted image. Furthermore, the CNRDE
values were 3 to 4 times higher than the CNR values of the low energy image.
Discussion: These results indicate that the proposed dual energy method
is feasible and worthy of further study.
Acknowledgement
This research has been co-funded by the European Union (European Social
Fund) and Greek national resources under the framework of the “Archimedes III: Funding of Research Groups in TEI of Athens” project of the
“Education & Lifelong Learning” Operational Programme.
DEVELOPMENT OF A TIMING CONTROL SYSTEM FOR LASER INDUCED
FLUORESCENCE (LIF) IN MEDICAL APPLICATIONS
Ioannis Karachalios a, Dimitrios Mathes a, Ioannis Valais a, Ioannis
Vamvakas b, Ioannis Sianoudis c. a Department of Biomedical Engineering,
Technological Educational Institute (T.Е.I.) of Athens, 122 10 Athens,
Greece,; b Department of Energy Technology Engineering, Technological
Educational Institute (T.Е.І.) of Athens, 122 10 Athens, Greece; c Department
of Optics & Optometry, Technological Educational Institute (T.Е.I.) of
Athens, 122 10 Athens, Greece
Background: Laser Induced Fluorescence (LIF) as a spectroscopic method
is successfully used as optical complementary techniques in medicine, in
order to characterize chemical, physical and optical properties in skin
tissue and to investigate changes for diagnostic purposes.
Materials and methods: The present study relates to the development of a
timing control system addapted on a pulsed Laser and optical spectrometer setup, used for fluorescence measurement applications. By controlling
the timing between the laser output pulse sequence and the reading of the
induced fluorescence pulse, useful information on the material quality and
its state can be acquired. Moreover this method can be applied on the
characterization of human tissue samples for potential malignancies or
skin cancer. The timing control circuitry is based on a microcontroller (RISC
technology), programmed to accurately trigger a sequence of emissions
and readouts between the pulsed laser and the spectrometer.
Results: The timing control circuitry could accurately control the sequence
of emissions and readouts between the pulsed laser and the spectrometer.
Fluorescence measurements of UV-laser excited phosphor screens were
performed and the fluorescence spectral response was acquired
Conclusions: The current system offers a low-cost and versatile tool for
application of LIF spectroscopy in studying biological samples with fluorescent properties.
23
Background: We have previously reported that adaptive responses
induced by chronic exposure to higher than on-earth levels of radiation
can greatly decrease radiation susceptibility of astronauts and help them
better cope with the detrimental effects of the exposure to unpredictable
sudden solar flares and coronal mass ejections which cause dramatic increase in radiation flux (1-3). We have also previously shown that traditional radioprotectors cannot be considered as efficient tools for reducing
the risk of space radiation due to some basic limitations such as the very
short time window for application of these agents and their considerable
toxicity (4). Furthermore, we previously hypothesized that finding
appropriate radiation mitigators with a post-exposure time window
longer than 24 hours will be a cardinal goal in planning future manned
space missions (5).
Aims: The aim of the present study was to investigate the potential radiation mitigation effect of vitamin C that is known as an effective antioxidant and free radical scavenger.
Materials and methods: One hundred twenty male Wistar albino
rats weighing 250-300 g were randomized into the following study
groups: I, control; II, Only exposure to gamma-radiation (LD 50/30);
treated with a single dose of vitamin C, III, 1h before irradiation, IV, V
and VI, 1h, 12h and 24 h after irradiation. Measurement of cell viability
and proliferation was also performed by using MTT cell proliferation
assay.
Results: The survival rate in animals received vitamin C 1h, 12h and 24h
after irradiation were 55 %, 60 %, and 80 %, respectively. On the other hand,
the viability of cells in animals received vitamin C 1h, 12h and 24h after
irradiation were 94.9 %, 99.0 %, and 100 %, respectively. The viability of the
cells in animals only exposed to gamma rays was 50.1%.
Conclusion: These findings clearly lead us to this conclusion that vitamin C
can potentially be used up to 24 hours after exposure to high levels of
ionizing radiation in cases such as the occurrence of currently unpredictable solar particle events. In this light, astronauts will have the critical
opportunity of evaluating their radiation exposure, before choosing any
therapeutic intervention. This long time window even allow them to
consult expert scientists on the Earth to make sure if they should use any
radiation mitigator.
References
1. Mortazavi SMJ, Cameron JR, Niroomand-rad A. Adaptive response
studies may help choose astronauts for long-term space travel. Advances
in Space Research. 2003;31(6):1543-51.
2. Mortazavi S, Cameron J, Niroomand-Rad A. The life saving role of radioadaptive responses in long-term interplanetary space journeys. International Congress Series. 2005;1276:266-7.
3. Mortazavi SMJ, Cameron JR, Niroomand-rad A. Is the Adaptive Response
an Efficient Protection Against the Detrimental Effects of Space Radiation.
International Cosmic Ray Conference2003. p. 4299.
4. Mortazavi SMJ. Space radiobiology and the new era of induced radioresistance: Should traditional concepts be moved to science history museums? Technology and Health Care. 2013.
5. Mortazavi SMJ, Mozdarani H. Deep space missions and the issue of
overcoming the problem of space radiation. International Journal of Radiation Research. 2013;11(3):199-202.
PATIENT AND OCCUPATIONAL RADIATION DOSES FROM AORTIC
ANEURYSM ENDOVASCULAR REPAIR
FUTURE ROLE OF VITAMIN C IN RADIATION MITIGATION AND ITS
POSSIBLE APPLICATIONS IN MANNED DEEP SPACE MISSIONS:
SURVIVAL STUDY AND THE MEASUREMENT OF CELL VIABILITY
S.M.J. Mortazavi a, b, S. Sharif-Zadeh c, H. Mozdarani d, M. Foadi e, M.
Haghani a, E. Sabet f. a The Center for Research on Protection against
Ionizing and Non-ionizing Radiation, School of Paramedical Sciences, Shiraz
University of Medical Sciences, Shiraz, Iran; b Medical Physics Department,
School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran;
c
Diagnostic Laboratory Science and Technology Research Center, School of
Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran;
d
Department of Medical Genetics, School of Medicine, TarbiatModares
University, Tehran, Iran; e Student Research Committee, School of
Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran;
f
Radiology Department, School of Paramedical Sciences, Yasouj University
of Medical Sciences, Yasouj, Iran
P. Raptou a, I. Pantos b, G. Voulalas c, C. Maltezos c, K. Kokkinis a, E.
Efstathopoulos b. a Department of Radiology, KAT General Hospital, Athens,
Greece; b 2nd Department of Radiology, General University Hospital Attikon,
Athens, Greece; c Department of Vascular Surgery, KAT General Hospital,
Athens, Greece
Aim: Aortic aneurysm endovascular repair (EVAR) requires extended
exposure to ionizing radiation. The aim of this study was to quantify the
associated radiological risks to patients and operators.
Methods: We performed a retrospective analysis of the maintained
database on patients with aortic aneurysm undergoing EVAR. Measurements of procedural dose area product (DAP) and fluoroscopic time (FT)
were obtained from the mobile C-arm unit and analyzed. We used previously published conversion factors to calculate the peak skin patient dose
and operators’ effective dose during these procedures.
24
Abstracts / Physica Medica 30S1 (2014)
Results: Between April 2012 and July 2013, 104 procedures with complete
data were available which regarded abdominal aortic aneurysm repairs
performed using sequential digital subtraction angiographic shots and
vessel reconstruction. The C-arm was positioned anterior-posteriorly and in
the cases of acute angled branch vessels that should be preserved, an
oblique view was also mandatory. The respective average DAP and FT were
5698±4093 cGy$cm2 and 19.93±13.60 min. The calculated average patient
peak skin dose was 0.2Gy which is 10 fold lower than the threshold for
induction of skin erythema (2Gy) and the maximal calculated peak skin
dose was 0.92Gy. The calculated average effective dose under the protective
apron was 13mSv per procedure which corresponds to an annual effective
dose of 1.35mSv for the primary operator due to EVAR procedures.
Conclusion: The risk associated with radiation exposure during EVAR is
relatively low for both the patient and the operator however measures to
minimize intra-operative exposure should always be considered.
RADIATION DOSE CALCULATIONS DURING PEDIATRIC BARIUM MEAL
EXAMINATIONS USING MCNP5 AND PCXMC 2.0 MONTE CARLO CODES
Аnastasios
Dimitriadis a,
Elsa
Emmanouel
Yakoumakis a,
Tzamicha a, Triantafillia Makri b, Efstratios Karavasilis a, Evangelos
Georgiou a. a Medical Physics Department, Medical School, University of
Athens, 75 Mikras Asias Str. Goudi 11527, Athens, Greece; b Radiological
Imaging Department, Ag. Sofia Hospital, Levadias and Thivon, Goudi 11527,
Athens, Greece
Key words: Pediatric radiology, Radiation dose, Monte carlo simulation,
DAP dosimetry
Radiation protection and estimation of the radiological risk in pediatric
radiology is essential due to children significant radiosensitivity and their
greater health detriment. The purpose of this study is to estimate the organ
and effective doses of pediatric patients undergoing Barium Meal (BM)
examinations.
During the (BM) studies, fluoroscopy and multiple radiographs are
involved. Since direct measurements of the dose in each organ are very
difficult if possible at all, clinical measurements of Dose Area Products
(DAPs) and two different Monte Carlo codes, MCNP5 and PCXMC2.0, were
involved. In clinical measurements, (DAPs) were assessed during examination of 51 patients undergoing (BM) examinations, separated almost
equally in 3 age categories, neonatal, 1 and 5 year old.
Organs receiving the highest amounts of radiation during BM examinations
were: the stomach (10.4-9.8, 10.2-10.0, 11.1-11.5 mGy), the gall bladder (7.17.2, 5.8-5.8, 5.2-3.1 mGy) and the spleen (7.5-6.9, 8.2-7.5, 4.3-4.7 mGy). The
three values in the brackets correspond to neonatal, 1 and 5-year old patients respectively. The first value of each age group is calculated with
PCXMC2.0 Monte Carlo code, while the second with MCNP5 simulation.
For all ages, the main contributors to the total organ and effective doses are
the fluoroscopy projections. There is a reasonable good coincidence between the PCXMC2.0 and MCNP5 calculations for the majority of the
studied organs. In some special cases there is a systematic disagreement of
organ doses (bones, gonads and oesophagus).
EXPOSURE RANGE LIMITS OF THREE INTRAORAL IMAGE RECEPTORS
FOR VARIOUS TUBE POTENTIAL, TUBE CURRENT AND EXPOSURE TIME
SETTINGS
E. Katsoni c, I. Tsalafoutas b, P. Gritzalis c, E. Stefanou c, E. Georgiou a, E.
Yakoumakis a. a Department of Medical Physics, Medical School, University
of Athens, Athens, Greece; b Medical Physics Department, Agios Savvas
Hospital, Athens, Greece; c Department of Oral Diagnosis and Radiology,
Dental School, University of Athens, Athens, Greece;
Purpose: To comparatively evaluate, in a systematic inter-equipment
manner, the useful exposure range of three intraoral image receptors
which are representative of the currently available technologies,
when exposed to different X-ray beam spectra, dose and dose rate
levels.
Materials-Method: A modern dental X-ray unit (Prostyle Intra DC, Planmeca Oy, Helsinki, Finland) offering a wide range of tube potential, tube
current and exposure time settings was used to expose A dental quality
control phantom. The receptors that were used to capture the radiographic
images of the phantom were: the Kodak Insight, the Kodak RVG-6000 and
the Duerr Vistascan system. The images that were produced over a wide
range of exposure factor settings were evaluated in terms of diagnostic
quality by three experienced radiologists.
Results: The number of images with acceptable diagnostic quality was in
total 1257; 310 with Insight, 331 with RVG 6000 and 616 with Vistascan. At
60 kV, diagnosable images were produced with doses ranging from 0.44 1.56 mGy for the Insight film 0.44 - 2.82 mGy for the RVG 6000 and 0.22 4.93 mGy for the Vistascan system. At 70 kV, the respective ranges were
0.39 - 1.28 mGy for the Insight film 0.31 - 2.55 mGy for the RVG6000 and
0.30 - 3.46 mGy for the Vistascan system.
Conclusions: The Vistascan exhibited the widest useful exposure range
and required the least exposure to produce a diagnosable image at almost
all tube potential settings. The RVG 6000 exhibited a slightly wider useful
exposure range than the Insight film, with almost the same dose requirements especially in higher Kv settings.
MEDICAL RADIATION PROTECTION EDUCATION AND TRAINING
PROVIDED BY A UNIVERSITY MEDICAL PHYSICS DEPARTMENT
E. Yakoumakis, P. Karaiskos, P. Papagiannis, P. Dimitriou, E.
Georgiou. Medical Physics Department, Faculty of Medicine, University of
Athens, 75 Mikras Asias Street, 11527, Greece
In the light of the publication of the new EU BSS and the importance
given to the E&T issues concerning radiation protection in medical
exposures this work presents the activities of the Medical Physics
Laboratory (MPL) of the University of Athens (UoA) concerning the
provision of Education and Training (E&T) in Medical Radiation Protection (MRP).
Several University Departments in Greece offer E&T in MRP. The MPL of the
Faculty of Medicine of the UoA is one of the main Academic E&T providers
in MRP at both pre- and post-graduate level. At pre-graduate level, MRP
forms an integral part of obligatory courses in Medical Physics included in
the curricula of the Medical, Dentistry and Nursery Schools of the University. In example, Medical Physics is offered in the first two semesters of
the Medical School and E&T in MRP is encouraged by the regulatory authority according to Article 7 of the previous 97/43 MED EURATOM
Directive. The syllabus includes Radiation Physics, Dosimetry, Instrumentation, Biological effects, and Radiation Protection (legislative framework,
medical, occupational and public exposures including emergency exposures). In addition, elements of MRP are incorporated in various elective
courses with learning objectives relevant to the applications of radiation in
medicine.
At post-graduate level an intereUniversity Post-Graduate Program in
Medical Radiation Physics (PGPMRP) is conducted since 1993. The
PGPMRP is running under the administration and co-ordination of the
Medical Physics Department of the UoA, in collaboration with the Physics
and Biology Departments of the UOA and the Medical Physics Departments
of the Universities of Ioannina, Thessaloniki, Crete and Thrace, as well as,
the National Centre for Science Research (NCSR) “Demokritos”, and the
Greek Atomic Energy Commission (GAEC). An extensive part of the syllabus is dedicated to MRP. The PGPMRP leads to an MSc degree in Medical
Physics and, optionally, to a PhD.
Continuing, lifelong education and training on radiation protection is also
provided by the Medical Physics Department to the medical and paramedical staff of medical radiation facilities in collaboration with medical
societies and professional bodies.
PATIENT RADIATION DOSE DURING EXTRACORPOREAL SHOCKWAVE
LITHOTRIPSY
J. Hristova-Popova, D. Taseva, I. Diyakov, J. Vassileva. National Center of
Radiobiology and Radiation Protection, Sofia, Bulgaria
Background: The purpose of this work is to present the first results from a
survey of patient radiation doses during Extracorporeal Shockwave Lithotripsy (ESWL) and to compare results.
Abstracts / Physica Medica 30S1 (2014)
Materials and methods: Two C-arm fluoroscopy systems and a total of 105
patients were included in the study. The following information was
recorded: complexity of the procedure and operator’s experience, patient
demographics, fluoroscopy time (FT, min) and patient radiation dose in
total kerma-area product (KAP, cGy.cm2). KAP was directly recorded from
the X-ray unit reading in the first department and measured with externally mounted KAP meter in the second department. Full characterization
of X-ray systems was performed using a PMMA phantom, where entrance
surface kerma rates were measured with a reference dosimeter at different
modes and field sizes.
Results: From the collected data the min, max, average and median values
were calculated. Results show that mean value of KAP at second unit was
more than 10 times higher: 2478 cGy.cm2 versus 230 cGy.cm2 at first unit.
Big variations were found between FT for procedures performed with the
first unit, but the mean values for both systems were commensurable: 3.4
min and 3.0 min, respectively, which cannot explain the large difference in
patient doses. The reasonable cause is different modes and settings of the
X-ray system, mostly the use of continuous fluoroscopy with the first
system.
Discussion: This comparison revealed a great potential for patient dose
reduction in clinical practice, such as the use of ultrasound localization as a
first option for restricting the use of fluoroscopy, also the practical skills
and radiation protection awareness of clinicians should be increased. A
good example of well-known and optimally used operator modes by
medical staff is the second X-ray system, where pulsed fluoroscopy with
low rates was used. Further studies in other departments are planned
aiming to propose national diagnostic reference levels for ESWL.
ITERATIVE RECONSTRUCTION AND FILTER BACK PROJECTION
ALGORITHMS IN CHEST-ABDOMEN-PELVIS CT: A COMPARISON FOR
THE SAME GROUP OF PATIENTS
Agapi Ploussi MSc a, Efthymia Alexopoulou MD, PhD a, Nikolaos
Economopoulos MD a, Stylianos I. Argentos MD a, Sofia Kordolaimi
MSc a, Ioannis Arapakis MD a, Vasiliki Tsitsia BSc a, b, Ioannis Seimenis
PhD b, Efstathios P. Efstathopoulos PhD a. a 2nd Dept. of Radiology, Medical
School, National and Kapodistrian University of Athens; b Medical Physics
Laboratory, Department of Medicine, Democritus University of Thrace,
Dragana Campus, Alexandroupolis, 68100 Greece
Background: Chest-Abdomen-Pelvis (CAP) Computed Tomography (CT)
delivers effective doses ranging from 6.7 to 28 mSv and have the biggest
contribution to collective dose in relationship with common CT exams.
Due to the high radiation dose, there is a raised concern about patient
exposure. Iterative Reconstruction (IR) algorithms are a promising tool in
order to achieve dose reduction without degrading the diagnostic
outcome.
Aim: To directly compare radiation dose and image quality between IR
(iDose4, Philips) and Filter Back Projection (FBP) algorithms in CAP CT for
the same patient population.
Materials and methods: A cohort of 17 follow-up patients who underwent
CAP CT examinations on a 64 multidetector CT with iDose4 Level 4 and
Level 6 was retrospectively included in our study. All patients had previously undergone a CAP CT exam on the same scanner with the standard
FBP protocol.
Volume CT dose index (CTDIvol) and dose length product (DLP) were
recorded, while effective dose was calculated from DLP measurements.
In order to take into account the patient size, Size-Specific Dose Estimate (SSDE) was also estimated. Objective image noise, Signal-to-Noise
Ratio (SNR) and Contrast-to-Noise Ratio (CNR) were calculated.
Two radiologists evaluated subjective image noise, sharpness,
contrast, diagnostic confidence and artifacts in chest and abdomenpelvis region.
Results: Compared with the standard FBP protocol there was a 45.4% and
46.2% decrease (P<0.001) in effective dose and SSDE respectively, using
iDose4. Objective image quality in terms of noise, SNR and CNR was superior in iDose4 as compared with FBP images (P<0.001). Subjective image
noise, sharpness, contrast and overall image quality were significantly
better in all regions with iDose4 technique (P<0.007). Diagnostic
25
confidence was comparable for the two algorithms in chest region while in
abdomenepelvis region was significantly better for iDose4 images
(P<0.001). Minor artifacts were observed in FBP and iDose4 image series
while a mild pixelated texture was noted in iDose4 Level 6 images. Superior
objective and subjective image quality was also observed using iDose4
Level 6 than with iDose4 Level 4.
Discussion: iDose4 allows significant radiation dose reduction while
improving image quality in CAP CT examinations for the same group of
patients.
EVALUATION OF THE DOSE, IMAGE QUALITY AND OPTIMIZTION OF CT
PEDIATRIC CRANIAL PROTOCOLS
Diego Rada, Luis Gonçalves, Carlos de Almeida. Laboratory of Radiological
Sciences e Universidade do Estado do Rio de Janeiro, Av. Sao Francisco
Xavier, 524. 20550900, Rio de Janeiro, Brazil.
Background:
Universidad de Carabobo, Valencia Venezuela. Bachelor in Physic
Universidade do Estado do Rio de Janeiro. Master in Biosciences
Computed tomography is a powerful tool for diagnostic imaging of various
diseases, but the high exposure to ionizing radiation in pediatric patients
in studies of cranial CT may develop complications in more radiosensitive
tissues, so it is very important to have a balance between radiation dose
and image quality.
In this work is tested the hypothesis that the quality parameter of image
Noise and the radiation dose can vary as a function of the Ray X tube
voltage in the protocols for pediatric cranial and can get this done is a way
to reduce the risks of exposure to ionizing radiation in pediatric cranial
tomography practices, with out altering the minimum quality required by
health authorities.
Material and methods: Using pediatric cranial CT protocols, and using
the phantom image quality MODEL ACCREDITATION PHANTOM 464 ACR
CT, and the AAPM PHANTOM, was determined QC parameters and the
number of CT for different reference materials. It was also determined
the noise variation and the dose variation as a function of voltage x-ray
tube.
Also, was created a system of evaluation in pediatric cranial tomography,
considering basic parameters of quality image, determining accordance
indexes with the minimal quality image in this parameters at eight CT
Scanners of Radiology services institutions in Rio de Janeiro-Brasil.
Results: Was observed in eight CT scanners in Rio de Janeiro state e
Brasil that the image noise in a reference material ( water) and the Dose
for pediatric cranial protocols was a quadratic function of the of the
Ray X tube voltage, leveraging these two properties was possible to
find a value of the voltage at which the image noise and the Dose are
minimal, ensuring optimization of protocols reducing the dose up to 69%
and respecting the Reference Dose levels set by the bodies under
regulators.
In turn, the evaluation system implemented in this work showed that five
of the eight CT Scanners studied are at different quality levels of
nonconformity for diagnostic use, urging the authorities to take corrective
action.
Discusions: It was possible to reduce the dose of radiation and increase
image quality in cranial pediatric protocols modulating voltage X-ray tube.
EFFECT OF RECOMBINANT HUMAN TSH (RHTSH) ON WHOLE BODY
RESIDENCE TIME OF 131I BASED ON OUR CLINICAL EXPERIENCE.
P. Exadaktilou b, E. Giannoula a,b, K. Giannopoulou a,b, M. Kotzassarlidou a,
T. Kalathas b, V. Chatzipavlidou b. a Medical Physics Dept, “Theagenion”
Cancer Hospital, Greece; b Nuclear Medicine Dept, “Theagenion” Cancer
Hospital, Greece
Recombinant human TSH (rhTSH) has been used in clinical practice by
nuclear medicine physicians and endocrinologists in “THEAGENION”
Cancer Hospital since 2012, while treating patients with differentiated
thyroid cancer (DTC), who could not tolerate hypothyroidism.
26
Abstracts / Physica Medica 30S1 (2014)
Aim: The aim of this study is to estimate the impact of rhTSH on total body
residence time, ttb , after 131I treatment.
Materials and methods: 48 DTC patients, who were referred to our centre
for their first ablation and/or follow up dose since 2012, were enrolled in
this study and divided in 2 groups. Group A included 19 pts received 131I
therapy, once with rhTSH stimulus and more than once after thyroid
hormone withdrawal. Group B included 29 pts treated only once with
rhTSH stimulus. Ablation and follow up dosage were 100 and 200 mCi
respectively. Total body dose rate measurements, during the seven days
after administration, performed by Inovision 451P survey meter were
recorded and converted to activity. Total body residence time was calculated by data analysis software Origin8, whereas statistical analysis of the
results was performed by SPSS 13.0.
Results: Applying paired samples statistics of Group A patients, mean
whole body residence time, ttb, was 28.2±10.6h when treated with rhTSH
stimulus and 33.8±11h in the case of no rhTSH stimulus. There was no
statistically significant difference between the derived values. In addition,
statistical analysis of all therapies from groups A and B, with and without
rhTSH stimulus, ended up to the same result.
Conclusions: These data suggest that, during 131I treatment, whole body
residence time of 131I does not alter significantly, with the method of patient preparation (rhTSH stimulus vs thyroid hormone withdrawal). It will
be of great importance to investigate rhTSH effect on blood residence time
of 131I, tblood , since they both have a great impact on blood dosimetry
according to the guidelines of EANM Dosimetry Committee.
IMPACT OF CENTRALIZED RADIO PHARMACY SERVICES AMONG
FOUR HOSPITALS IN THE 4TH REGIONAL HEALTH AUTHORITY OF
MACEDONIA AND THRACE
The purpose of this work is to estimate patient doses from the most
commonly performed procedures in a digital radiology department, to
compare them with the national DRLs established in the country and to
look for a potential of optimization.
Materials and methods: The X-ray systems in the imaging department
are: digital radiography (DR) system, C-arm fluoroscopy system, 16 slices
computed tomography (CT) system, and DR mammography system, all of
them manufactured by GE. The most common procedures are chest X-ray
performed with the DR system, hysterosalpingography with the fluoroscopy system, and abdomen, chest, head and lumbar spine scans on the CT.
Data necessary for dose estimations were extracted from the DICOM
header of the patient examination files. Tube output measurements were
made on the DR system and kerma area product (KAP) from the DICOM
header was compared with the calculated data from the measurements.
Entrance surface air kerma (ESAK) rate was measured on the C-arm for all
modes. Computed tomography kerma index (CTKI) in phantom was
measured and compared with data from the CT display. Tube output and
half value layer were measured on the mammography system and incident
air kerma and mean glandular dose were calculated for phantom and
patients.
Results: Not very good agreement was found between the measured and
extracted data for DR (up to 28 % for some KAP values) and bigger difference for CTKI (16 % for abdomen and 37 % for head examinations). Estimated local typical patient doses were found to be lower than the national
DRLs.
Discussion: The current national DRLs were established 5 years ago and a
lot of new digital systems were installed afterwards. They provide big
potential for reduction of patient doses compared to old analogue systems.
New DRLs are planned to be established during next two years and
probably lower values will be set.
Maria Kotzassarlidou. Medical Physics Dept., “Theagenion” Cancer Hospital,
Thessaloniki, Greece
The aim of this study is to examine and evaluate a realistic case of establishing a shared radiopharmacy program for the Nuclear Medicine Departments of four hospitals in the 4th Regional Health Authority of
Macedonia and Thrace (4thRHA), located in the same area of Thessaloniki.
The hospitals involved in this study are: University General Hospital of
Thessaloniki “AHEPA”, General Hospital “IPPOKRATIO”, First General
Hospital “ST.PAUL’S”, Cancer Hospital “THEAGENIO”.
Data were taken from the international and greek literature, the above
mentioned hospitals and 4thRHA. Principles of the study were adopted by
the Operational Restructuring Plan for Greek Hospitals, prepared by the
National University of Athens , for the Ministry of Health.
Current situation of the above mentioned Nuclear Medicine Departments
was presented, regarding equipment, personnel, type and number of tests,
budget for consumption of radiopharmaceuticals. Cost and manpower
savings were estimated for the case of establishing centralized radiopharmacy services among these departments.
According to the results, a shared radiopharmacy program is expected to
cause a reduction in annual spending of 92900 V by all the participating
hospitals. Patients’ waiting time may be reduced whereas patient welfare
may be increased. In addition, more efficient human resource management can be achieved, improving and upgrading the practice of nuclear
medicine and patient care in the participating hospitals.
ESTIMATION OF TYPICAL PATIENT DOSES IN DIGITAL RADIOLOGY
DEPARTMENT
S. Avramova-Cholakova a,b, N. Nenova-Balatsenko b. aNational Centre of
Radiobiology and Radiation Protection; bHospital for Women’s Health
“Nadezhda”
Background: Bulgarian legislation introduced in 2005 requirement for
elaboration of Diagnostic Reference Levels (DRL) and estimation of local
typical doses in every department. There is still little experience in the
country with the estimation and use of typical doses, which is not
routinely performed yet.
BEAM SPECIFIC CALCULATION CHECKS FOR TREATMENT PLANNING
SYSTEM COMMISSIONING
Patatoukas George, Dilvoi Maria, Platoni Kalliopi, Papadogiannis
Panagiotis, Chalkia Marina, Efstathopoulos Efstathios. Medical Physics
Unit, 2nd Department of Radiology, Medical School, University of Athens,
Greece
Background: Commissioning is one of the most important parts of the
entire QA programme for both the TPS and the planning process. Beam
specific calculation checks can be used to detect the differences between
measured and calculated doses. These checks relate to single beam irradiations of water phantom under the conditions close to those used for the
clinical commissioning tests and are designed in such manner that the user
should be able to compare the results for selected points with the calculated dose values. We present a (portion of the) series of dose-related
measurements that took place in our department in order to prepare the
Varian AAA dose calculation algorithm for use in our department’s
everyday clinical practice.
Materials and methods: The medical physics team of our radiotherapy
department followed all procedures described by AAPM TG 51, IAEA
report 430 as well as IAEA TEC-DOC-1583 for the AAA beam
data commissioning following a software update that took place in
the department. We compared point doses in a number of fields and
depths for two Varian Linear Accelerators (LINACs).The format of the
beam specific calculation checks includes the check of output factors,
field width and penumbra size for a range of field sizes for open and
wedged fields used in clinical commissioning and also a check of the
doses in different parts of the water phantom for open and wedged
beams.
Results: Dose calculation checks were performed for three open fields
(4cm x 4cm, 10cm x 10cm, 25cm x 25cm) and for one wedged (10cm x
10cm) at four measurement depths (dmax, 5cm, 10cm and 20cm).
Dose to points on the central axis and off-axis point(s) was measured.
Dose calculation checks for high-energy x-ray beams (6 and 15MV)
were expressed in dose units (cGy). The difference between these
calculated data and the corresponding measured data can be calculated
Abstracts / Physica Medica 30S1 (2014)
and analyzed in the same way as proposed in the aforementioned
protocols.
Discussion: Model-based point doses calculated with the AA algorithm in
both 6 and 15 MV were in excellent agreement with the ‘true’ dose
measured in the treatment room.
IN-VIVO DOSIMETRY IN 3D CONFORMAL RADIOTHERAPY OF BREAST
AND HEAD AND NECK CANCER
Dilvoi Maria a, Thalassinou Stella b, Patatoukas George a, Platoni
Kouloulias
Vassilios c,
Kypraiou
Efrosini c,
Darakis
Kalliopi a,
Georgios c, Efstathopoulos Efstathios a. a Medical Physics Unit, 2nd
Department of Radiology, Medical School, University of Athens, Greece;
b
Papapostolou LTD, Athens, Greece; cRadiation Therapy Unit, 2nd
Department of Radiology, Medical School, University of Athens, Greece
Background: We present a study carried out at our department in order to
investigate the accuracy of dose distribution at the junction region for 3Dconformal radiotherapy treatments that were accomplished following our
adopted clinical protocol for breast and head and neck cases.
Materials and methods: “In vivo” dosimetry has been performed using
thermo-luminescence dosimeters (TLD) in 10 head and neck cancer patients and 10 breast cancer patients) irradiated with a 6 MV photon beam.
Entrance dose measurements were performed in the field junction regions. A comparison between the measured (in-vivo) and expected (TPS)
values was carried out and possible sources of discrepancy were studied
and analysed.
Results: The mean deviation between measured and expected dose in the
region of junction was significantly higher in breast compared to head and
neck irradiation (-2.8 ± 15.4 % and 0.2 ± 8.2 % respectively, Mann-Whitney
test: 푃 ¼ 0.002).
Discussion: The results indicate the superiority of mono-isocentric technique compared to the rotating couch technique in terms of dose delivery
accuracy for treatments with field junctioning planning techniques. “In
vivo” dosimetry remains a reliable method in order to check the actual
dose that is finally delivered to a patient and can provide vital insight into
the irradiation conditions in the treatment room, which can help in the
optimization of the treatment delivery technique(s).
DUAL-ENERGY CONTRAST-ENHANCED DIGITAL MAMMOGRAPHY:
GLANDULAR DOSE ESTIMATION USING MONTE CARLO CODE AND
VOXEL PHANTOM
E. Yakoumakis a, E. Tzamicha a, A. Dimitriadis a, E. Georgiou a, V.
Tsapaki c, A. Chalazonitis b. a Medical Physics Dpt, University of Athens,
Germany; b Radiology Dpt, Alexandra General Hospital National, Germany;
c
Radiology Dpt, Agia Olga General Hospital National, Germany
Purpose: Clinical results of Contrast Enhanced Digital Mammography
(CEDM) are promising. The purpose of this study is to evaluate glandular
dose during a CEDM study by using Monte Carlo method and voxel
phantom.
Materials and methods: Dual-energy CEDM performed by acquiring a
pair of low and high-energy images. This is achieved in a single breast
compression, using Mo or Rh filter at 26 to 31 kVp values, for low energy images and double-layer filter (0,3mm Cu ± 0,3mm Al) at 45 to 49
kVp, for high energy images. EGSnrc Monte Carlo code and female voxel
phantom was used to simulate the interaction of photons with matter
and estimate the glandular dose (Dg) to the breast. One million X-ray
photons were input to breast geometry of phantom with a 2 to 8 cm
thickness range and a breast glandular composition of 1%, 25%, 50%, 75%
and 100%.
Breast was simulated in both the Cranio-Caudal (CC) and the Medio-Lateral
oblique (MLO) views. Air Kerma measurements for various settings of tube
current-exposure time product were performed with a Radical (model
2026c with ionization chamber) dosimeter.
Results: For a breast with compressed thickness of 5.0 cm and a glandular
fraction from 1% to 100%, glandular dose values for CC view were ranged
between 0.547 e 2.593 mGy for low and high-energy images, which is less
than the European Diagnostic Reference Level.
27
Conclusions: The dose contribution analysis of each projection for all
voxel phantom thicknesses and breast compositions from 1% to 100%
glandular, indicates that low dose part mammography is the main
contributor to total glandular breast dose.
CORRELATION OF ADVANCED MAGNETIC RESONANCE IMAGING AND
BRAIN SPECT FOR THE PRE-SURGICAL EVALUATION OF CEREBRAL
TUMOUR PATIENTS
I. Tsougos a, V. Tsitsia a, V. Valotassiou b, I. Siasios c, K. Fountas c, E.
Kapsalaki d, K. Theodorou a, I. Fezoulidis d, P. Georgoulias b. a Medical
Physics Department, University of Thessaly, Panepistimiou 3, Biopolis, 41110
Larissa, Greece; b Nuclear Medicine Department, University Hospital of
Larissa, Biopolis, 41110 Larissa, Greece; c Department of Neurosurgery,
University Hospital of Larissa, Biopolis, 41110 Larissa, Greece; d Department
of Radiology, University Hospital of Larissa, Biopolis, 41110 Larissa, Greece
Background: In order to obtain a more objective and realistic diagnostic
pre e surgical approach, data combination of neuro-imaging procedures
seems to be the key to success. Under this perspective, a protocol of presurgical brain tumour evaluation is applied in collaboration of the Medical
Physics/Radiology/Neurosurgery departments of the University of Thessaly, which aims to correlate Brain SPECT and advanced MR techniques for
the optimization of differential diagnosis.
Image fusion of advanced MR techniques and brain SPECT using Tc-99,
introduce new possibilities and set high expectations regarding differential diagnosis of cerebral tumors.
Materials and methods: The study was performed on a 3-Tesla MRI whole
body scanner (GE, Healthcare, Signa® HDx) using a standard birdcage
phased-array head coil and on a Functional Imaging Scanner (GE, Infinia II
gamma-camera).
The MRI protocol included a standardized series of brain sequences as
well as 1H-MRS, DWI, DTI and PWI. The Brain SPECT was obtained
20e30min after iv injection of 925MBq (25mCi) tracer activity. The
radiopharmaceutical was prepared using Myoview™, (General Electric
Healthcare Ltd) that was reconstituted with technetium-99m pertechnetate (99mTcO4) sterile solution in the Department of Nuclear Medicine. The imaging data were then analyzed and fused in the Xeleris
Workstation (GE Healthcare).
Results: Our preliminary results show that there is a positive correlation of
the Spectroscopy and MRI Perfusion findings with Brain SPECT results,
especially regarding difficult differential diagnostic problems, such as GBM
vs Metastasis and typical vs atypical Meningioma.
Discussion: Pre-surgical brain tumour imaging that combines SPECT and
advanced MR techniques may be able to optimize patient treatment.
ASSESSMENT OF MEAN GLANDULAR DOSE (MGD) IN ROUTINE
MAMMOGRAPHY IN ASKLEPIEIO VOULAS GENERAL HOSPITAL
Despina Papadopoulou PhD, Eleni Likaki MD,PhD, Fotini Soureti, Ioannis
Gavriilidis MD, Panagiotis Vitoratos MD, Kassos Ilias MD, Ioannis
Kaskarelis MD, PhD.. Department of Radiology, “Asklepieio Voulas” General
Hospital, Vasileos Pavlou 1, Voula, Greece
Background: Nowadays mammography is the basic examination used for
early detection of breast cancer. However, since ionizing radiation is used
at a radiosensitive organ, it is very important to estimate patient’s radiation dose and investigate all possible factors minimizing radiation exposure. The aim of this study was to estimate mean Glandular dose (MGD) for
Craniocaudal (CC) and Mediolateral oblique (MLO) views and the total
MGD per breast. Moreover, all factors affecting MGD were investigated for
the optimization of the procedure.
Materials and methods: Mean Glandular dose was estimated for 200
women who underwent mammography, with the Siemens Mammomat
300 Nova mammography unit, at the Radiation Department of Asklepieio
Voulas General Hospital. Records were kept for each patient concerning
mammography technique used (kVp, mAs, Anode/ Filter), Compressed
Breast Thickness (CBT), and Breast Glandular Fraction according to BIRADS. The MGD was calculated based on measurements of normalized
entrance skin dose (ESD) in air, Half Value Layer (HVL) and conversion
28
Abstracts / Physica Medica 30S1 (2014)
factors, according to the method described in details at IAEA Technical
Reports Series 457.
Results: Mean Glandular dose was estimated for 200 women, who underwent routine mammography at Asklepieio Voulas General Hospital. MGD for
CC projection view ranged between 0,597-2,120 mGy (mean¼1,141mGy)
and for MLO view from 0,697-3,355mGy (mean¼1,308mGy). Total MGD per
breast ranged between 1,321- 5,338 mGy (median 2,348mGy). Basic factors
affecting MGD were the projection view and the compressed breast thickness, since they affect exposure values. CBT valued between 17mm to 78mm
for the CC view and 21mm to 89mm for the MLO view.
Discussion: 100% of CC projections and 94,6% of MLO projections, had doses
less than 3.0 mGy, as recommended by the American College of Radiology
recommendations. MGD values are similar to those published in other
studies. However, further investigation and record of MGD values in our
hospital, may contribute to the establishment of national diagnostic reference
levels in mammography, in order to optimize patient radiation protection.
Keywords: Radiation dose, mammography, Mean Glandular Dose
BREAST TREATMENT PLANNING OPTIMIZATION: FIELD-IN-A-FIELD
(FIF) VS. HIGHER PHOTON ENERGIES
I. Grigoriadis a, E. Kamperis b, A. Makridou a, M. Chatzimarkou a, P.
Pantelis b, L. Zoglopitou a, K. Theodorou c, M. Charalambidou b. a Medical
Physics Department, Theagenio Cancer Hospital, Greece; b Radiation
Oncology Department, Theagenio Cancer Hospital, Greece; c Medical Physics
Department, University of Thessaly, Greece
Background: The aim of this study is to compare four breast treatment
planning techniques in the setting of 3D conformal radiotherapy (3DCRT). These techniques were two 6MV tangential fields, two 15MV
tangential fields, two 6MV tangential fields plus one 15MV FIF and plus
two 15MV FIFs. These were compared in order to show the most efficient
technique.
Materials and methods: In total, 120 radiotherapy plans were made, four
for each of the 30 patients. Treatment planning was performed with
Eclipse TPS and dose was calculated using the analytical anisotropic algorithm (version 8917). The dose distribution was “fine-tuned” so that all
plans shared the same maximum. The entire PTV was covered with the
95% isodose and the point maximum dose did not exceed 107% according
to the ICRU guidelines. The dose received by adjacent normal organs was
well within tolerance limits. The plan optimization was made by a medical
physicist. Statistical analysis was done with SPSS 20. GLM repeated measures procedure was employed to study the variance among the different
treatment planning techniques. Mean dose(%) and minimum dose(%)
comprised the measure factors, while age, cancer site (righteleft), T stage
in TNM staging system (T1eT2) and clinical tumor volume (CTV) were
used as covariates in our model.
Results: Analysis showed a statistically significant difference among all
different planning techniques regarding mean dose (p<0.001) which, for
each plan was 96.63±0.29, 98.89±0.18, 100.46±0.24 and 101.76±0.2,
respectively (95% CI, p<0.001). There was an interaction between CTV size
and mean dose, notably for large breasted patients (CTV>750cc). In this
particular clinical scenario two 6MV tangential fields with 2 FIFs consistently outperformed the others. Minimum dose was also statistically
different among all groups (p<0.05) except for the two FIF-less tangential
fields with 6 and 15 MV. Interestingly, minimum dose(%) lacked a
dependence on volume size.
Discussion: The use of two FIFs together with two tangential fields in patients with breast cancer achieved high mean and minimum dose that were
also seen in large CTVs. For smaller CTVs (<400cc), all methods converge in
terms of efficiency and, therefore, a less involved plan could be adopted.
Keywords: breast cancer, radiotherapy, planning optimization
ACCURACY ASSESSMENT OF PENCIL BEAM AND MONTE CARLO DOSE
CALCULATION ALGORITHMS DURING IMRT AND VMAT DELIVERY
N. Yakoumakis a, b, A. Episkopakis c, E. Koutsouveli a, G. Kollias a, C.
Paraskevopoulou a, P. Sandilos a, b, P. Karaiskos a, c. a Radiotherapy
Department, Hygeia Hospital, Kifisias Avenue and 4 Erythrou Stavrou,
Marousi, 15123, Athens, Greece; b 1st Department of Radiology, Aretaieion
University Hospital, Medical School, Athens, Greece. Vas. Sofias Avenue 76,
Athens 11528, Greece; c Medical Physics Laboratory, Medical School,
University of Athens, 75 Mikras Asias, 11527 Athens, Greece
Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are techniques that have been widely used
over the last years for treating cancer due to better target coverage and
the lower dose to the critical organs. This study assesses the accuracy of
the Pencil Beam (PB) and the Monte Carlo (MC) calculation algorithms
commonly used to determine the dose distribution in such applications.
IMRT and VMAT plans were created for ten prostate patients using a
commercially available treatment planning system (Monaco, Elekta Inc.).
All plans were optimized to be clinically acceptable and the final dose
calculation was performed using a) the PB and b) the MC calculation
algorithm. The plans were evaluated in the central coronal plane using
the I'mRT Matrixx (IBA Dosimetry GmbH) 2D-array placed in a solid
water phantom a) by setting all control points to zero gantry degree and
b) by leaving the beam orientation as planned. Evaluation was performed
with OmniPro-I'mRT software using the gamma index method with
acceptance criteria of 3% dose difference and 3 mm distance to agreement taking into account all points with dose values greater than the 10%
of the maximum dose. Results show that PB calculation algorithm can
accurately determine the dose distribution applied to the I'mRT Matrixx
2D array when all control points were set to zero gantry degree for both
IMRT and VMAT plans (average passing rates of 96.6 and 94.7% of the
points passed the 3%/3 mm acceptance criteria, for IMRT and VMAT, were
observed, respectively). On the other hand, considerable differences
between the different calculation algorithms were observed when the
actual (i.e. the planned) beam orientation was used for the plan verification. In this case, the PB algorithm was found adequate for dose
determination only for the IMRT plan verification (an average passing
rate of 91% was observed). For the VMAT plans, MC was found significant
superior compared to the PB dose calculation algorithm (average passing
rates of 73.5 and 93% for the PB and the MC algorithms, were observed,
respectively).
THERMOGRAPHIC BLOOD FLOW VARIATION RELATIVE TO LOWER LIMP
POSITION
A. Skouroliakou a, I. Seferis b, C. Michail b, I. Sianoudis c, D. Mathes b, I.
Valais b. a Department of Energy Technology Engineering, Technological
Educational Institute (T.Е.І.) of Athens, 122 10 Athens, Greece; b Department
of Biomedical Engineering, Technological Educational Institute (T.Е.І.) of
Athens, 122 10 Athens, Greece; c Department of Optics & Optometry,
Technological Educational Institute (T.Е.І.) of Athens, 122 10 Athens, Greece
Background: Quantitative infrared thermography is an established method
for the study of skin temperature distribution. Dynamic infrared thermography records skin temperature following the application of a transient local
thermal excitation. The method aims at the elucidation of the thermomechanical behavior of the skin and the role of blood flow on heat diffusion
Methods: An infrared camera was used to record temperature variations
on the skin of human feet of three volunteers, depending on feet position.
A cooled cylindrical aluminum bar was placed on the skin. The bar was in
contact with the skin for 1 minute. After its removal the temperature on
the cooled skin area was recorded with an infrared camera. Time for the
temperature to return to its initial value was measured for the foot in
horizontal and vertical position.
Results: A thermogram was obtained every approximately 10 seconds.
Temperature was measured on the recorded thermograms on 6 spots: three
in the cooled and three in the neighboring area. Return to thermal balance
followed roughly the same pattern for all spots, although the heating rate
was faster for the horizontal position of the foot. Thermal balance was
achieved faster at the spots that were positioned on a vein passage.
Discussion: Our results confirm the influence of blood flow on the thermal
regulation of the skin. Spots located over veins exhibit different thermal
behavior due to thermal convection through blood flow. Changing the
position of the foot from vertical to horizontal, effectively influence blood
Abstracts / Physica Medica 30S1 (2014)
perfusion as in the vertical position blood flow is opposite to gravity. Our
findings contribute to the experimental validation of thermal models that
characterize the human skin.
CHEST e ABDOMEN e PELVIS CT EXAMINATIONS USING ITERATIVE
RECONSTRUCTION TECHNIQUE: EVALUATION OF RADIATION DOSE
AND IMAGE QUALITY
Arapakis Ioannis a, Alexopoulou Efthymia a, Seimenis Ioannis a, Tsitsia
Vasiliki a, b, Kordolaimi Sofia a, Economopoulos Nikolaos a, Argentos
Stylianos a, Ploussi Agapi a, Efstathopoulos P. Efstathios a. a 2nd Dept. of
Radiology, Medical School, National and Kapodistrian University of Athens;
b
Medical Physics Laboratory, Department of Medicine, Democritus
University of Thrace, Dragana Campus, Alexandroupolis, 68100, Greece
Background: Chest-Abdomen-Pelvis (CAP) Computed Tomography (CT)
examination is the second most common CT examination after CT head
and is used to investigate manifestations of systemic diseases, infections,
neoplasms or generally is used for diseases that indicate chest and upper
and lower abdomen abdormalities. Due to the high radiation exposure and
the frequency of CAP CT studies there is a raised concern about patient risk
that recommends optimization and reduction of the radiation dose.
Purpose: To evaluate how iDose4 hybrid iterative reconstruction algorithm
(iDose4, Philips) effects on radiation dose and image quality in Chest Abdomen - Pelvis CT examinations.
Materials and methods: 99 patients who took part, underwent CAP CT
examinations with the use of “FBP protocol” (the ”old standard”), performing filtered back projection reconstruction algorithm and 84 with the
use of “iDose4 protocol” using the Iterative Reconstruction (IR) algorithm
iDose4 (Philips Healthcare) on a Brilliance 64 multidetector CT. There were
three groups of patients according to their weight. (Group 1, 41 e 60 kg:
Group 2, 61 e 90 kg: Group 3, >90kg). Volume CT dose index and dose
length product (DLP) were recorded, while effective dose was calculated
from DLP measurements. Objective image characteristics in terms of image
noise, signal to noise ratio (SNR) and contrast to noise ratio (CNR) were
calculated. In addition, the images were subjectively reviewed by two
radiologists on a 5-point scale.
Results: There was an overall 46.5% reduction of the effective dose with
the use of iDose4 protocol compared with the FBP protocol. Objective
image quality was better in iDose4 images than in FBP images. Subjective
image noise, contrast, sharpness and diagnostic confidence scores tended
to be better for iDose4 protocol. Minor artifacts were observed for both
protocols.
Discussion: According to our results, using the iterative reconstruction
algorithm high radiation exposure reduction is achieved, while maintaining or improving image quality in adults’ CAP CT examinations.
29
treatment included superficial x-rays, 60Co, and electron-beam irradiation. The total tumor doses ranged from 6 to 40 Gy. A complete response
occurred in all lesions receiving >20 Gy. Various treatment techniques
have been used since the introduction of TSEB therapy in the early 1950s.
More recent techniques have used stationary two-, four-, six-, and eightfield positions, as well as rotational techniques. In general, the uniformity
of dose distribution improves as the number of fields increases, but at the
expense of complexity and increased machine time for the treatment of
each patient. The optimal technique with reasonable uniformity of dose
appears to be a sixedual-field technique refined by Page et al. The electron
beam with an effective central axis energy of 3 to 6 MeV and, rarely, 9 MeV
is used to treat three anterior and three posterior stationary treatment
fields. The patient is placed in front of the beam in six positions during
treatment. The entire wide-field skin surface receives 1.5 to 2 Gy each 2day cycle. Irradiation usually is administered on a 4-day/week dose
schedule; the total dose depends on the intent (curative versus palliative).
The percentage of photon contamination for a single dual-field cycle
should not exceed 0.3%. Verification of delivered doses should be performed routinely using thermoluminescent dosimeters placed on skin
surfaces.
Areas not directly exposed to the path of the electron beam (soles of feet,
perineum, medial upper thighs, axillae, posterior auricular areas, inframammary regions, vertex of scalp, and areas under the skin folds) are
treated with separate electron beam.
Materials and methods: Mycosis Fungoides treatment at Instituto
Nacional de Cancerologia (Mexico city) technique use 4 stationary fields
with an effective energy of 4 MeV. Because of the field size needed to
achieve a one field irradiation, patient must be treated in stand up position
using gantry angles near to 90º. This situation lead us to make personalized
dosimetries per patient, which involves changes in the known field parameters (known at isocenter) like field size, field shape and flatness. This
measurements are usually performed with TLD dosimeters according to
AAPM recommendations. However, dosimetry with TLD could be an
expensive procedure for the hospital, till the necessary equipment is not
available. Instead, we use PTR dosimetry as well as EDR dosimetry to
perform this measurements. The measure procedure involves a water
phantom of 180 cm length and 20 cm depth. We set up the phantom at a
distance from the according to the patients area needed to be irradiated.
This distance are measured with the patient (as a simulation) as well as
gantry, collimator and field size needed.
With the measured dose with the film we estimate a dose rate at 300 cm
from source and calculate the number of monitor units needed to achieve 1
Gy to the whole field.
DOSE DETERMINATION FOR A MYCOSIS FUNGOIDES DISEASE
TREATMENT USING EDR FILM DOSIMETRY FOR A TSEI TECHNIQUE
F. Herrera-Martinez, M. Rodriguez-Ponce, D. Toledano-Cuevas. Instituto
Nacional de Cancerología, Mexico City, Mexico
Background: Cutaneous T-cell lymphoma (CTCL) refers to a spectrum of
closely related malignant T-cell lymphoproliferative disorders in which the
predominant clinical manifestations involve the skin. There are two major
zary’s
subgroups within the CTCL spectrum: mycosis fungoides (MF) and Se
syndrome.
The plaque and tumor phases of classic MF are characterized by clinically
perceptible accumulations of atypical lymphoid cells in the skin to produce
palpable lesions. Individual lesions tend to regress spontaneously in areas
and merge with adjacent lesions to form lesions with irregular shapes. The
magnitude of infiltration varies from lesion to lesion, which, with the
characteristic configurations, produces a virtually diagnostic clinical
appearance. Tumorous lesions may develop gradually from preexisting
plaques or may appear suddenly in an eruptive manner, indicating a biologically more aggressive clone of malignant cells. The modalities for
Figure 1. (left) Measurement set up. The 15 marks visible at the picture are the
points in which we did the dose measurements with PTR. The mark at the center
shows the position at the patient umbilicus. In this case we have 88 gantry degrees,
SSD¼ 300 cm and field size at isocenter ¼ 34x34 cm. Electron energy was 4 MeV.
Since we have 4 different treatment fields, this measurements are repeated four
times for each parameter group. (right) Film calibration and measurements by
field. The film calibration were done at isocenter in a 4 MeV 10x10 electron field. A
PDD measure is taken as well for energy verification purposes.
30
Abstracts / Physica Medica 30S1 (2014)
Clinical results are shown on figure 4.
Figure 2. Patient position. Treatment were performed Mondays and Thursdays for
anterior and posterior planes (above left) and Tuesdays and Fridays for lateral
planes (above right).
Results: The dosimetry results were as follows: This measurements were
compared with measurements performed daily in vivo, in order to estimate obvious changes in geometry because of the anatomy and, if it is the
case, correct the monitor units delivery. Daily dosimetry reported the
average dose measurements shown at tables 2 and 3.
Table 1. Measured dose rates with EDR films for three treatment positions.
Plane
Measured Dose rate (cGy/UM)
UM for 1 Gy delivery
anterior
lateral
posterior
0.077
0.078
0.074
1294
1290
1351
Figure 4. Clinical results after TSEI treatment. Total dose, 30 Gy.Ă
Figure 3. Measured PDD for a 4 MeV electron beam.Ă
Table 2
Mean dose received at anterior posterior planes.
Neck (cGy)
Umbilicus (cGy)
Right leg(cGy)
Left leg (cGy)
79.785
81.005
109.795
106.26
90.63
91.995
90.275
92.945
INVESTIGATION OF CORRELATION BETWEEN GRID PARAMETERS AND
IMAGE QUALITY METRICS AND EVALUATION OF GRID PERFORMANCE
THROUGH IMAGE QUALITY
Table 3
Mean dose received at lateral planes.
Center (cGy) Right leg (cGy) Left leg (cGy) Right arm (cGy) Left arm (cGy)
108.56
103.525
78.18
91.595
83.155
79.04
Conclusions: Since the start of this treatment protocol (April, 2009)
we treated 25 patients with magna fields. None of them presented
acute effects nor scars for overdose areas or recurrences in partial
irradiated areas. In vivo measurements are still performed daily for a
quality assurance protocol, because of the complexity mode.
Electron magna fields has become a reliable treatment option because
of the even radiated areas living option for a second treatment course
in case of advance cases or a partial chemotherapy response. For
further work, we are planning the design of a filter to improve the
beam flatness.
References:
1. AAMP Report. No. 23 total skin electron therapy: dosimetry and
technique.
2. Perez and Brady's Principles and Practice of Radiation Oncology, 5th
Edition Lippincott Williams & Wilkins.
3. Radiochromic film dosimetry: Recomendations of AAPM radiation
therapy committee task group 55.
67.155
107.88
93.2
58.955
Ozlem Birgul a, Umran Onal a, Turan Olgar b, Dogan Bor b. a Ankara
University, Institute of Nuclear Sciences, Department of Medical Physics,
Turkey; b Ankara University, Faculty of Engineering, Department of Physics
Engineering, Turkey
Abstracts / Physica Medica 30S1 (2014)
Background: Anti-scatter grids that are used in x-ray imaging improve the
image contrast by reducing the scatter at a cost of increased patient radiation dose. Ability to manipulate the image contrast in digital imaging
may give the users option to omit the use of grids, especially for pediatric
applications where dose is more critical. In this work, the aim is to
investigate the use of image quality metrics for the evaluation of grid
performance together with the grid parameters used to define the grid
specifications by the grid manufacturers. Image quality metrics can be
calculated more easily and with this approach, a method which is practical
for clinical use and that can simplify decision making process in grid usage
and grid selection is proposed.
Materials and methods: In the first part of this work, bucky factor(BFGP),
grid sensitivity, contrast-improvement-factor(CIF) and signal-to-noiseratio-improvement-factor(SIFGP) were calculated from the measured
values of primary, scattered and total radiations using a methodology
similar to IEC 60627 protocol.
Next, contrast(C), bucky factor(BFIQ), high contrast spatial resolution(HCSR), signal to noise ratio(SNR) and signal-to-noise ratioimprovement-factor(SIFIQ) were calculated using simple image quality
tests for the similar scatter thicknesses and kVp values and the correlations
between image quality and grid performance parameters were
investigated.
Results: Grid parameter measurements were made using a digital fluoroscopic system using six different grids with different ratios and strip
densities. Experiments were repeated for different tube voltages and
scatter thicknesses (5-25cm) to understand the performance variation
between different clinical applications and patient sizes. For the second
part, a subset of four grids were selected. As a result, SIFIQ and SIFGP values
were found close to each other. SIF was found to be less than one for all
grids and tube voltages for scatter thicknesses of 5cm and 10cm. For 15cm,
it was less than one for some grids.
Discussion: Therefore, removal of the grid can be suggested for the infants
(0e12months) and up to the 5 year old child. For 15 cm scatter thickness
(representing 10 year old child), evaluations should be done together with
other image quality metrics and patient doses.
This work is partially supported by TUBITAK 112T965 Research Grant.
RETROSPECTIVE REVIEW OF LOCALLY SET TOLERANCES FOR VMAT
PROSTATE PATIENT SPECIFIC QA USING THE COMPASS® SYSTEM
A. Sdrolia, K. Brownsword, J.E. Marsden, K.T. Alty, A.W. Beavis. Department
of Radiation Physics, Queen’s Centre for Oncology and Haematology, Hull and
East Yorkshire Teaching Hospitals NHS Trust, UK
Purpose: The purpose of this study was to evaluate COMPASS® pretreatment QA results for prostate VMAT. COMPASS® is a commercial 3D
dosimetric QA system which allows calculation of 3D dose distributions
based on planning CT data-sets and measurement adjusted beam
fluences and is now used as the primary patient specific QA system in
our hospital. Initially, all plans were individually reviewed by competent
physicists who determined their clinical suitability before continuing
to treatment. Our institutional QC standard clinical criterion for g-index
assessment (tolerance of 3%/3mm) is failure of less than 3% of
points (Low, D. et al, 1998). The criterion for dose comparisons (for
all dose points) is 3% which is the accuracy used for TPS verification
at commissioning (IAEA TECDOC-1583). This study retrospectively
reviews results in terms of our criteria to determine if these pass
rates/tolerances are appropriate, or if more challenging values could be
used.
Method: 76 clinical prostate RapidArc (one-arc) plans, delivered by four
dosimetrically matched linacs, were measured using a 2D-array sensor
(MatriXX Evolution with gantry angle sensor) and analysed using
COMPASS® (v.2, IBA Dosimetry). The g-index (global) and set dosevolume points were used for quantifying the agreement between TPS
calculations and measurements. For the PTVs the D99%, D50% and D1%
differences were analysed. The percentage volume with g greater than
1, average g and mean dose difference for all the structures were also
investigated.
Results and conclusions: With respect to the PTV mean dose differences,
it was found that the plans all fell within the 3% tolerance and mostly
31
within 2%, although there was a relatively small systematic difference.
The absolute percentage differences of average and median doses suggest a weak linac dependence of the results which could be attributed to
the differences in the dosimetric leaf gap. To confirm this, a sample of
plans should be assessed across the linac fleet. Finally, the correlation
between the g pass rates and the differences in the D99%, D50% and D1%
was found to be weak suggesting that gamma analysis in isolation has
little clinical meaning and should only be used to indicate outliers for
further analysis.
A STUDY OF DOSE DISTRIBUTIONS MEASURED WITH A HELICAL DIODE
ARRAY
Sp Papageorgiou, S. Xenophos, J. Vamvakas, V.
Gialousis. Physics Dept., IASSO Hospital, Athens, Greece
Kostakis,
G.
Background: Treatment verification of complicated techniques, such as
IMRT and VMAT, is often carried out using commercially available QA
systems, based on array detectors (or ionization chambers).
Materials and methods: This work compares the dose distributions from
Oncentra Masterplan TPS (v4.3) to those obtained with a calibrated ARCCHECK system (Sun Nuclear), in connection with an Elekta Synergy Linac.
Ionization measurements were also carried out in water and PMMA, using a
PTW, Unidos Dosimeter, a Farmer (30013) and a Pinpoint chamber (31006).
The following steps were realized: 1/. TPS accuracy was tested in static and
rotational fields, planned on the AC phantom, with its density adjusted, so
that TPS point dose calculations match the doses at equivalent depths in
water. 2/. Scaling factor (SF) and Excess Scatter correction (ESC) of the
PMMA phantoms relative to water were obtained from density measurements of the phantoms and ionization measurements in PMMA and in
water. 3/. The AC system was calibrated in a 10x10 static field, according to
vendors procedure and tested for other F.S. TPS calculations, AC measured
values and corrected ionization chamber measurements at the isocenter in
the AC and at selected points in a flat PMMA phantom were compared. 4/.
Rotational fields with fixed apertures were planned on the AC phantom,
with PTV and OARs, and compared to chamber and AC measurements,
using the AC software (3DVH). 5/. The same procedure was applied for
Patient VMAT/IMRT prostate plans with a 6MV photon beam.
Results: 1/. Oncentra calculations, ionization chamber measurements and
AC compare very well for static and fixed aperture rotational fields
(diffs.within 2%) with g>98% (3%,3mm). 2/. For the vast majority of the
patient cases, g93% (3%,3mm), mean PTV and isocenter dose differences
within 4% and 3% from the TPS and chamber measurements respectively.
DVH differences for other PTVs and ROIs are presented.
Discussion: The influence of plan optimization parameters (e.g grid resolution, gantry angle spacing, dose rate etc.) has not been considered here.
Effects associated with, couch attenuation, accelerator start/stop and
ionization chamber used, are presented. Concerning clinical cases, the
overall g value is a “gross” verification criterion, whereas the PTV/OAR
DVH may be very significant for the final analysis and decision making.
HYPOFRACTIONATED RADIATION THERAPY TREATMENT SCHEMES IN
PROSTATE CANCER PATIENTS EMPLOYING VOLUMETRIC MODULATED
ARC THERAPY; PLAN VERIFICATION USING A CYLINDRICAL DIODE
ARRAY
V. Kostakis a, Sp. Papageorgiou a, G. Gialousis a, I. Vamvakas a, M. Trichas b, I.
Georgakopoulos b. a IASO Hospital, Medical Physics Department, Greece;
b
IASO Hospital, Radiotherapy Department, Greece
Background: VMAT (Volumetric Modulated Arc Therapy) is one of the
latest developments in Radiotherapy, allowing the delivery of high dose
to complex shaped tumors that lie in close vicinity to sensitive structures by continuously varying beam aperture, gantry speed and dose
rate. The aim of this study is to present a hypofractionated treatment
scheme for prostate patients using a Volumetric Modulated Arc Therapy
approach.
Materials and methods: VMAT as a treatment technique has been
introduced in our department in June 2012 with more than 30
32
Abstracts / Physica Medica 30S1 (2014)
patients being treated for prostate cancer. Of these, 10 patients were
treated with a hypofractionated regime which consists of delivering
70Gy in prostate and proximal vesicles (fractional dose: 2.5Gy) and
61.6Gy in distal seminal vesicles (fractional dose: 2.2Gy) in 28 fractions
on daily basis (SIB technique). A dual-arc delivery technique was
adopted with an arc length of 348, a collimator angle of 45 and 6MV
photon beam. Oncentra Masterplan v4.3 was utilized for the treatment
planning process and treatment was performed on a Synergy linear
accelerator (Elekta Ltd, Crawley, UK). All the treatment plans were
verified using a cylindrical diode array (ArcCHECK, Sun Nuclear Corporation, Melbourne, FL).
Results: All treatment plans showed adequate PTV coverage and dose
homogeneity based on the investigation of dose distribution along the
three axes (transverse, sagittal, coronal) and the value of DVH based
metrics, such as D95%, D98%, D2% and mean dose. OAR sparing was
fulfilled for all treatment plans according to the treatment planning
criteria that were set for each organ at risk (V40 < 35% and V60 < 17%
for rectum; V40 < 50% and V60 < 25% bladder; D10% < 50Gy for the
femoral heads; D150cc < 40Gy for bowel; D50% < 50Gy for the penile
bulb).
All the clinical plans delivered passed the gamma analysis (3% / 3mm) with
a pixel pass rate of >95%. Additionally, plan evaluation was performed
using patient DVH-based metrics which are calculated using the 3DVH s/w.
Discussion: Highly conformal dose distributions can be achieved with
VMAT techniques with a considerable shortening of delivery time which in
turn offers advantages in terms of intrafraction movement and patient
throughput. Accuracy of treatment delivery can be verified using ArcCHECK and the 3DVH s/w module.
TREND OF OCCUPATIONAL DOSES OF RADIATION WORKERS IN CATH
LABS IN MINISTRY OF HEALTH HOSPITALS, OMAN: A DOSE ANALYSIS
L.S. Arun Kumar, Rashid Al-Hajri, Saeed Al-Kalbani. Medical Physics and
Radiation Protection Service, DGEA, Ministry of Health, PO Box 393,
Muscat-100, Sultanate of Oman
In Ministry of Health (MOH), Oman, ionizing radiation is widely used in
many areas such as for diagnosis, radiation therapy, bio-medical research
and use of sealed radioisotope(s) for blood irradiation etc. Use of radiation
and particularly the diagnostic use of x-rays in the Sultanate of Oman is
increasing with the proliferation of hospitals and clinics. The great benefits
of increased and improved diagnostic services have improved the quality
of life for those in Oman. The World Health Organisation in 2000
applauded the quality, efficiency and delivery of health care to the population and ranked the Oman's health care system eighth in the world(1).
The increased resources are clear from the statistics: in 1970 there were
only 2 hospitals in Oman, in 2010 the number was 50 and with 172 health
centres(2). One of the balancing consequences of increased x-ray use in
Oman is the increased radiation dose to the population. Medical radiation
accounts for the majority of the manmade radiation dose to populations(3).
Use of radiation must always be according to the ALARP (as low as
reasonably practical) philosophy so as to avoid unnecessary radiation
doses and minimise the doses where required which in turn reduces the
occupational exposure. During 2012, a total of 1,247,016 radiological procedures were performed in Ministry of Health (MOH) institutions. The
corresponding number in 2000 was 799,452. This shows that there is
about 35% increase in radiological examinations for the last 12 year period.
This indicates that the population dose is on the rise as the radiological
facilities are increasing in Oman which in turn increases the occupational
dose of radiation workers.
The occupational exposure of radiation workers of MOH hospitals were
monitored by Thermo Luminescent Dosimeters (TLD's) which are dispatched to each location by post. We have developed a dose management
software e Centralised Dose Recording System (CDRS) in-house for the
management of dose records of Ministry of Health (MOH) radiation
workers which manage TLD serial number allocation, issue to various
hospitals/institutions, collection from respective hospitals/ institutions
after wear period, dose assessment and monitoring, and finally dispatching the dose reports to MOH hospitals/ health centres / institutions. Also,
the same software will handle the individual dose(s) of each worker(s) and
their dose history. Every month we are dispatching more than 1300 plus
badges to 145 hospitals/ institutions of MOH throughout the Sultanate of
Oman after tagging in CDRS. Thus we keep track of the TLD badges of each
worker in every location of MOH on a monthly basis. Some of the above
locations are very remote (few thousand kilometers away from the capital
city- Muscat).
In this study, we have analysed the dose pattern of radiation workers in the
cath labs of Ministry of Health hospitals for the ten year period
2002e2012. The range of effective doses (Hp (10)) of the workers for the
year 2012 is shown below:
Effective dose
Range in mSv
Number of workers wearing Number of workers wearing
WB badges
FH badges
0.0 - 0.5
0.5 - 1.0
1.0 - 2.0
2.0 - 5.0
5.0 - 10
10 - 15
15 - 20
Above 20
681
10
1
2
0
0
0
0
665
25
7
13
0
0
1
0
It has been observed that workers in cardiology receives the highest
effective doses from among all the radiation workers where as those
workers in radiation oncology receive the lowest as expected. Further
details will be discussed during presentation.
References
1. The World Health Report 2000 e Health systems: Improving performance. 2001. Geneva, Switzerland, World Health Organization.
2. Annual Health Report 2012 Published by Ministry of Health, Sultanate of
Oman, 2012.
3. UNSCEAR. Sources and Effects of Ionizing Radiation. 2000. New York,
United Nations.
4. Public Health England (PHE),UK. Technical Specifications of Body Dosimeters and variation of Hp (10) response with photon energy. 2013. PHE,
UK.
INDEPENDENT 3D DOSE CALCULATION SOFTWARE FOR STEREOTACTIC
BRAIN RADIOSURGERY BASED ON IMPLICIT MODELING
T. Kilindris, K. Theodorou, C. Kappas. University of Thessaly, School of
Medicine, Biopolis, 41100 Larissa
Modern treatment planning systems are complex software systems that
provide a robust work frame for everyday routine radiotherapy. Those
systems do not always offer sufficient flexibility to act as general purpose
customizable dose calculation tools. We present a software tool to assist in
independent dose calculations by using user specified dose calculation
model on full patient anatomical data.
The software tool was written in C++ using Kitware's VTK to model
anatomical data extracted from DICOM CTs, dose accumulating spatial
structures and radiotherapy modalities. All surfaces and volumes involved
in dose calculation (patient, irradiation equipment and dose volume) were
modeled as implicit functions. Coordinate systems alignment was done
either visually using reference markers on CT's or manually provided by
user as a transformation matrix. Dose calculation at specific points was
done using Tissue Phantom Ratio (TPR) and correcting factors for field
sizes. For fractionated dose delivery MU calculation was done per fractionated group. DVH are also calculated for any user provided and selected
anatomical structures.
Dose accumulation volume was 250 x 250 x 254 mm (XYZ). For comparison reasons the code was run on Windows XP 32bit Pentium E8500 at 3.16
GHz and on a Windows 7 64bit i7 at 3.4 GHz. On both systems the code was
32 bit compiled. Optimizations were disabled. Dose calculation grid
spacing was selected 1mm, 2mm, and 5mm. Three dimensional dose
matrix of a single beam was calculated in 46, 844 and 6953 ms respectively
on the Windows XP system and in 26, 317, 3992 ms respectively on the
Windows 7 system.
The proposed software tool can be used for fast evaluation and sensitivity
test of a calculated treatment plan. Changes of several parameters of the
radiation delivery setup can be done by altering several modeling parameters like dose calculation grid density, emulating positioning errors
Abstracts / Physica Medica 30S1 (2014)
and delineation uncertainties. The computed 3D dose matrix can be
merged with the CT data and visualized or saved.
AUTOMATIC OPTIMIZATION OF MULTI-ISOCENTER SRT/SRS TREATMENT
PLANNING PROCESS
T. Kilindris, K. Theodorou. University of Thessaly, School of Medicine,
Biopolis, 41100 Larissa
Therapeutic effects of stereotactic brain radiosurgery are highly dependent
on spatial accuracy and adequate dose homogeneity within target volume.
During irradiation delivery, sparing of surrounding healthy or critical tissue is essential. In order to achieve high compliance to the demanding
constrains posed by stereotactic brain radiosurgery several optimization
techniques were studied regarding critical treatment plan decision variables. We present an optimization framework to ease manual selection of
isocenters.
Efficient dose delivery in stereotactic radiosurgery requires proper selection of several critical treatment set up parameters. The spatial energy
pattern delivered to the lesion during multi arc single isocenter therapy is
approximated as a spherical or more general as an elliptical volume
enclosing spherical/elliptical surfaces as isodose surfaces. The approximation of the lesion volume with those spherical volumes maintaining
several dosimetric requirements can be proven a hard optimization
problem. Stereotactic position and morphology of the lesion can lead the
problem infeasible under specific dosimetric constrains. Dose conformity
at the prescribed level on targets boundaries and dose homogeneity
within target volume were the main candidates as objective functions to
be optimized. Mixed integer and nonlinear optimization techniques were
applied.
Several types of lesion that were candidates for stereotactic radiosurgery
were delineated and both contours and surface models were generated of
the CTV and PTV respectively. Constrains in gantry and couch positions
were set up. Design parameters like number of arcs used, number of couch
position used, set of collimators to be used etc were either fixed or set for
optimization during strategy evaluation. An automated model configuration file was created in AMPL along with data supplied by our in house
treatment planning system. The generated configuration file where used
directly to online available solvers. The output of the solver was evaluated
and if acceptable, calculation of the full treatment plan was done for
precise DVH verification.
The optimization of isocenter or shot placement in multi-isocenter SRT/
SRS treatment is a crucial factor for target dose inhomogeneity and
coverage. This work aims to the development of an automatic procedure
that could optimize the number and the location of isocenters in an SRT/
SRS treatment planning process.
33
set of performance indicators. Acceptance results were in accordance with
the main standards of NHSBSP and European protocols [2,3]. Parameters
such as detector response, MTF, SNR and CNR provided performance data
for future comparison against other digital equipments. HVL and radiation
output data were used in the determination of conversion factors for the
ESAK and AGD assesments, and also to validate display exposure values or
convert them into a usable dose metric. The customized set of routine tests
proved to be a simplified and effective method for system performance
consistency evaluation. It was found that after verification of proper
operation during acceptance testing, if the system failed it generally
occurred suddenly rather than through gradual deterioration of performance. Nevertheless, gradual performance decrease ocurred for MTF and
gradual changes ocurred with SNR of the AOP System. SNR of the AOP
(STD) mode stepwiselly increased. The selected routine tests were efficient
in identification of all the situations in which technical intervention was
necessary. Moreover weekly routine quality control test results were
successfull in the identification of system malfunctioning representing
possible diagnostic information compromise sometimes blind to the
experienced eyes of the radiologists.
NHS Cancer Screening Programs (2008) Technical evaluation of GE
Essential full field digital mammography system, NHSBSP Equipment
Report 0803, pp 1e24.
NHS Cancer Screening Programs (2009) Commissioning and routine
testing of full field digital mammography systems, NHSBSP Equipment
Report 0604 version 3, pp 2e43.
European Commission (2006) European guidelines for quality assurance in
breast cancer screening and diagnosis, Official publications of the European Communities, 4rd Edition, Chapter 2b, pp 105e165.
Acquisition System Senographe DS, Quality Control Manual 5133453-41PT, GE Healthcare, pp 10e108.
THE EMPLOYMENT STATUS OF PHD HOLDERS AT THE SECTOR OF
MEDICAL PHYSICS AND ENGINEERING: PROBITAND OAXACA-BLINDER
DECOMPOSITION ANALYSIS
Eirini Konstantina Nikolatou a, Dimitrios Glotsos b, Joan Daouli a. a Department
of Economic Sciences, University of Patras, Patras, Greece; b Department of
Biomedical Engineering, Technological Education Institute of Athens, Greece
Background: The number of PhD graduates in Greece has been growing
continuously throughout the last thirty years. Since 1996 the number of
PhD graduates have increased by almost 5.5 times and it reached to 2500
graduates in 2007, where 60% of them are men and 40% women (figure 1).
Most of the PhD graduates are observed in health sciences and the sciences
of engineering.
LESSONS LEARNED FROM A 5 YEAR PERIOD OF A CUSTOMIZED
QUALITY CONTROL PROGRAM IN DIGITAL MAMMOGRAPHY
A.R. Roda a, M.C. Lopes a, b, M.C. de Sousa a. a Medical Physics Department of
the IPOCFG, EPE, Coimbra, Portugal; b Physics Department of the University of
Aveiro, Aveiro, Portugal
Topics: Full field digital mammography (FFDM), half-value layer (HVL),
entrance surface air kerma (ESAK), detector response, modulation
transfer function (MTF), signal to noise ratio (SNR), contrast to noise
ratio (CNR).
The main role of medical physicist in digital mammography is to implement a quality control program that will ensure consistency and optimal
operation of the X-ray equipment. The first step is to identify the physical
parameters that characterize the system and optimize image quality performance. The second step is to evaluate the system gradual deterioration
-determined limits. This
of performance and the compliance with the pre
study presents the results of a quality control program performed on a GE
Senographe DS full field digital mammography system along a 5 years
period. Acceptance baseline values were established using NHSBSP reports
[1,2] and European Guidelines [3] as reference. Additionally we used the
GE’s templates and the physical parameters recommended by the manufacturer [4] for routine tests and apply them weekly. We improved the set
of routine tests in order to extend monitored parameters to the essential
Fig. 1. Number of PhD graduates in Greece, per academic year.Ă
Source: Statistics of Education, ESYE www.statistics.gr
Regarding their employment status, by sector of industry, most of men and
women PHD holders are employed in the sector of education (42.3% and
47% respectively), as well as in the sector of health care (22.4% and 26.2%
respectively).
Most previous research work is concentrated at the U.K. and U.S. academic
markets and mainly the areas under investigation concern issues at
earnings differential among males and females PhDs holders and issues of
34
Abstracts / Physica Medica 30S1 (2014)
promotion, and / or other issues of discrimination within the academic
sector.
The objective of this paper is to investigate the factors influencing the
probability for a PhD holder in Greece to work in the Medical Physics and
Engineering sector (figure 2) among PhD holders working at the sectors of
Health care, Natural sciences and Computer Engineering, as well as the
probability of existence of gender discrimination e wage gap in this sector
(figure 3).
JEL Classification: J21, J24, J31, J71
Acknowledgements
ĂThis research has been co-financed by the European Union (European
Social Fund e ESF) and Greek national funds through the Operational
Program ”Education and Lifelong Learning” of the National Strategic
Reference Framework (NSRF) e Research Funding Program: Heracleitus II.
Investing in knowledge society through the European Social Fund.
A RETROSPECTIVE DOSIMETRY COMPARISON OF TG43 AND A
COMMERCIALLY AVAILABLE MBDCA ALGORITHM FOR AN APBI
BRACHYTHERAPY PATIENT COHORT
K. Zourari a, V. Peppa a, A. Herein b, T. Major b, P. Papagiannis a. a Medical
Physics Laboratory, Medical School, University of Athens, Greece; b National
Institute of Oncology, Budapest, Hungary
Figure 2. Number of PhD holders in Medical Physics and Engineering in Greece by
gender and age, 1999 - 2012
Source: LFS 1999 e 2012, ESYE www.statistics.gr
Figure 3. median wage of PhD holders in Greece, 1999 e 2012Ă
Source: LFS 1999 e 2012, ESYE www.statistics.gr
Material and methods: In this paper,Probit and Oaxaca model is estimated using Labor Force Survey data of the years 1998 to 2012.
Results: Our results indicate that being young PhD holder and woman,
increases the probability of being employed in the Greek Medical Physics
and Engineering sector, whereas being married decreases the probability.
Also, regarding the employment at the sector of Greek Medical Physics and
Engineering, the results indicate that being a PhD holder having experience and /or working in the private sector, increases the probability of
being employed at this sector of economic activity compared to someone
who has less experience and/or works in health sciences, natural science
or computer engineering.
Our findings also suggest that gender discrimination in wages is being
observed for PhD holders working in the sector of Medical Physics and
Engineering, as well as there is an observed wage gap among the PhD
holders working in Medical Physics and Engineering among the private
and public sector. Men PhD holders gain higher earnings than women in
the sector of Medical Physics and Engineering, as well as, PhD holders
working in the public sector of Medical Physics and Engineering gain
higher earnings than those working in the private sector.
Keywords: scientific human capital, medical engineering labor market,
wage discrimination
Purpose: TG43 based TPS for brachytherapy rely on the superposition of
source specific data pre-calculated in a standard homogeneous water geometry. Model-based Dose Calculation Algorithms (MBDCA) were recently
incorporated in commercially available TPS to account for patient-specific
scatter conditions and heterogeneities. This work reports on the comparison of TG43 and MBDCA in an 192Ir HDR Accelerated Partial Breast Irradiation (APBI) patient cohort, to quantify the potential benefit of MBDCAs
and assess whether protocol changes are required to conform to the accuracy standards these convey.
Materials and methods: A cohort of 38 APBI patients was selected.
Dosimetric calculations for the treatment plans were performed using
both the TG43 and collapsed cone algorithm options of the Oncentra
Brachy v4.4 TPS. Quantitative dosimetry results were obtained in the form
of PTV coverage, dose homogeneity and conformity, as well as dose volume histogram analysis for the breast, lung, heart and skin. The source
position centroid-to-skin/-lung distances were also considered to investigate the impact of target location to the dose distributions. Significance
testing of observed differences was also carried out to assess the importance of target location.
Results: Comparison of MBDCA and TG43 dose distributions and DVHs
shows considerable differences at the skin and the lung for all patients, as
expected. Differences of TG43 and MBDCA plan dosimetric indices are
however relatively small, with a slight overestimation by TG43 except for
the PTV dose homogeneity. On average, percentage differences are less
than 1% for the PTV and the dose homogeneity and conformity indices,
greater for the lung and the heart (on the order of 5% for V5Gy) and
maximum for the skin (on the order of 10% for D10cc), with a strong correlation to target location.
Conclusions: So long as dose optimization and prescription is based on
TG43 in view of the relatively increased computation time of MBDCAs, the
close agreement observed between MBDCA and TG43 results close to the
PTV suggests that there is no need for the amendment of currently used
APBI protocols.
Acknowledgement: Research co-financed by the EU-ESF and Greek funds.
NSRF Operational Program Competitiveness and Entrepreneurship-Joint
Research and Technology Programmes.
AN EGSNRC-BASED MODEL OF THE GAMMA KNIFE PERFEXION UNIT
FOR SMALL FIELD DOSIMETRIC CALCULATIONS
E. Pappas a, A. Moutsatsos a, E. Pantelis a, C. Paraskevopoulou b, E.
Georgiou a, P. Karaiskos a, b. a Medical Physics Laboratory, Medical School,
University of Athens, 75 Mikras Asias, 11527 Athens, Greece; b Gamma Knife
Department, Hygeia Hospital, Kifisias Avenue and 4 Erythrou Stavrou,
Marousi, 15123 Athens, Greece
Abstracts / Physica Medica 30S1 (2014)
Purpose: To present an EGSnrc-based model of the Gamma Knife Perfexion (PFX) radiosurgery unit used for Monte Carlo (MC) dosimetry
calculations. Emphasis is given on the effect of specific model and
scoring parameters on PFX output factor (OF) and relative dose profile
results.
Materials and methods: A detailed model of the PFX system was established using the C++ geometry package of the EGSnrc MC code, based on
relevant drawings provided by the vendor. All 192 Co-60 sources along
with their capsules and bushing were modeled in a single input file per
collimator size (16mm, 8mm and 4mm). Dosimetry calculations were
performed in a spherical, 16cm diameter water phantom using the
“egs_chamber” user code. The angular distribution of the photons emitted
from each source was assumed to be isotropic. The developed PFX model
was benchmarked against off axis relative dose profiles measured with
radiochromic films. Dose was scored in concentric spherical volumes,
centered at UCP, with radii ranging from 0.2mm to 3mm and used to
evaluate volume averaging effects on OF results. Simulations were
repeated for confined angular distributions of the emitted photons to
assess the gained simulation efficiency against dosimetric accuracy. In
specific, the cone half angle, as defined with respect to the source channel
central axis, varied from 5o to 90o.
Results and conclusion: Confinement of the emitted photons angular
distribution resulted in a time efficiency gain factor of up to 210 (for 5o
cone half angle and the 4mm collimator), and had no considerable effect
on relative dose profile data. Contrarily, the gained simulation efficiency
was found to come at the expense of the accuracy of the calculated OF
values, leading to an overestimation of up to 6% and 3.5% for the 4mm and
8mm collimators, respectively, as compared to isotropic photon emission.
Volume averaging was found to impact OF results for sensitive volume
radii greater than 0.5mm and 1.25mm for the 4mm and 8mm collimators,
respectively. The developed PFX model will be used to determine the kQcln
correction factors corresponding to commonly used detectors for PFX OF
measurements.
CONTRIBUTION OF FLT-PET/CT IN METASTATIC BRAIN TUMORS
Alexandra Nikaki a, Roxani Efthymiadou a, Ioannis Tsougos b, Vassilios
Prassopoulos a, Vassiliki Filippi a, Fani Vlachou a, Despina Savvidou a, Theodoros
Pipikos a, Ioannis Andreou a, Panagiotis Georgoulias c. a PET/CT Department,
HYGEIA SA, Greece; b Medical Physics Department, University of Thessaly,
Greece; c Nuclear Medicine Department, University of Thessaly, Greece
Aim: To explore the role of FLT-PET/CT in recurrent metastatic brain
lesions.
Method-material: 13 patients underwent 17 FLT-PET examinations for
evaluation of metastatic brain lesions. The primary tumor site was: breast
cancer in 7 cases, lung cancer in 7, thymoma in 2, and melanoma in 1 case.
All patients had received the appropriate treatment during the course of
disease and all of them had received radiotherapy for metastatic brain
disease, while in 2/17 cases additional surgical excision of the brain lesion
was performed. FLT-PET/CT was performed 55±5min after the iv administration of 18F-FLT at a Siemens Biograph LSO PET/CT device. Findings
were evaluated visually as positive or negative: any finding with FLT uptake clearly above the background activity was characterized as positive.
Semiquantitative assessment was also used, with the calculation of SUVmax and tumor-to-background ratio (T/B: SUVmax of the tumor/ SUVmean
of the background).
Results: FLT-PET/CT was characterized negative in 3 cases and positive in
14 (15 lesions). Average SUVmax and T/B were 2.27±1.3 and 11.62±5.47
respectively. Using paired t-test, T/B values were statistically significant
higher than the SUVmax values (p <0.05).
In 12 cases patients were referred for treatment after FLT-PET examination,
11 of whom had a positive PET examination, while data is missing for 1. In 2
FLT-PET positive cases the patients were referred for biopsy, both of which
were negative: 1 of these patients exhibited progressive disease in the next
follow-up examination. In the other PET-positive/biopsy-negative case, FLT
uptake pattern was diffuse and SUVmax was 1.29. In 2 FLT-PET-negative
cases patients were put under surveillance. In 1 FLT-PET negative case, the
patient was referred for chemotherapy, due to disease lesions other than
brain.
35
Conclusion: Admitting the referral bias and the small and inhomogeneous
sample, our results indicate that 18F-FLT- РЕΤ, by offering additional
functional information, may be a useful tool in evaluation of metastatic
brain lesions. Average SUVmax and T/B values differ substantially, possibly
due to the more constant background activity. Variability noted mostly in
T/B values could be attributed to differences in primary site and treatment
response.
THE USE OF CENTROMERIC/TELOMERIC PNA PROBES IN PREMATURELY
CONDENSED CHROMOSOMES OF PERIPHERAL BLOOD LYMPHOCYTES
FOR ABSORBED DOSE ESTIMATION
I. Karachristou a, D. Zafiropoulos b, M. Karakosta a, V. Hatzi a, G.
Pantelias a, G. Terzoudi a. a Health Physics, Radiobiology & Cytogenetics
laboratory, Institute of Nuclear & Radiological Sciences & Technology,
Energy & Safety, NCSR “Demokritos”, Athens, Greece; b Laboratori Nazionali
di Legnaro, Istituto Nazionale di Fisica Nucleare, Legnaro, Italy
Background: The frequency of dicentric chromosomes in human peripheral blood lymphocytes at metaphase is considered as the “goldstandard” for biological dosimetry and at present is the most widely
used method for dose assessment. This methodology requires
lymphocyte culture and analysis time of more than three days. Such
long time period, is inadequate in radiation emergency medicine since a
rapid and accurate estimation of the dose is considered to be a high
priority. Alternatively, cell fusion mediated premature chromosome
condensation (PCC) enables the observation of radiation-induced cytogenetic damage directly in non-stimulated lymphocytes without the
need of blood culturing. Quantification of an exposure by means of this
method has been limited so far mainly to the analysis of chromosome
fragments and rings. This limitation is due to the fact that staining with
Giemsa of prematurely condensed chromosomes (PCCs) does not allow
visualization of the centromeric regions and, consequently, the identification of dicentrics, centric rings, and acentric fragments. In the present work, we overcome this shortcoming by developing a methodology
enabling us the detection of dicentric chromosomes rapidly and accurately in non-stimulated lymphocyte PCCs.
Materials and methods: The methodology of cell fusion mediated premature chromosome condensation was used and combined with fluorescence in situ hybridization (FISH) technique, using simultaneously
telomere and centromere peptide nucleid acid (PNA) probes. For detecting
of dicentric chromosomes in cultured lymphocytes conventional metaphase analysis was used.
Results: Analysis of dicentrics, centric rings and acentric fragments in nonstimulated lymphocyte PCCs was carried out and dose-response curves for
doses up to 8 Gy have been constructed. For comparison, dose response
curves were also obtained using the conventional metaphase analysis in
stimulated lymphocytes.
Discussion: FISH analysis with centromeric/telomeric PNA probes in G0lymphocyte PCCs is proved to be an effective, sensitive and fast approach
for the estimation of absorbed doses especially in case of radiation
emergency medicine. The advantages of this new approach in comparison
with the conventional method will be discussed.
STUDY OF THE REPLACEMENT-UPDATE OF THE PACS/RIS SYSTEM IN
THE MEDICAL IMAGING DEPARTMENT OF THE IASO GENERAL
HOSPITAL
Ioanna
Tzovara
Foteini
Stromatia
MScMedical
Physicist a,
MDRadiologist b. a Department of Medical physics IASO General Hospital,
Greece; b Department of Medical Imaging IASO General Hospital, Mesogion
264, 15562 Holargos, Greece
Aim: The aim of the study was to update or replace the PACS/RIS system of
the medical imaging departments, of IASO General Hospital, after eight
years of archiving 5341 G-Bytes of medical data, since the installation in
2002, in order to achieve better work flow and faster medical diagnosis.
Materials and methods: The archiving and management of medical imaging data, in our Hospital, were performed using a PACS/RIS system,
36
Abstracts / Physica Medica 30S1 (2014)
interconnecting Radiology, interventional Radiology and Nuclear Medicine
departments. High resolution diagnostic workstations were used for
diagnosis, whereas secondary workstations allowed direct access of the
Intensive Care unit and the Emergency department. In order to update the
installed system, a systematic recording of the specifications of all medical
devices, connected to the PACS system, along with information concerning
the department of installation, the level of their operation and any additional operations, was performed. A corresponding recording was performed for the current diagnostic workstations along with data concerning
modifications. All users were personally interviewed in order to establish
user oriented specifications. The number of images per unit was calculated
by the product of the number of images per examination by the number of
examinations per unit. Furthermore the amount of DICOM information
from every modality was also documented. Finally it was determined that
all exams should be directly accessible for at least five years and archived
for thirty years, according to the regulations for medical imaging archiving.
Results: Total time for diagnosis was reduced due to bidirectional
communication of the diagnostic workstation and the workstation of
every medical device. Radiologists noted 30% faster diagnosis and now
they process special exams in the reading- evaluation facility. Ability for
MPR was given and safer measurements for vessel region. Access to archives was improved, daily workflow also due to corresponding
improvement in the work list.
Conclusions: Replacement e updating of PACS/RIS system has improved
daily workflow. Also has fastened information processing giving additional
capabilities in cases such as comparative assessment for oncological
patients.
DOSE CALCULATION PROGRAM BY MATLAB, FOR MONITORING
RADIOTHERAPY TREATMENT PLANNING SYSTEM COMMISSIONING
I. Vamvakas a, b, S. Synefia a, P. Charalabatou c,a, Ch. Armpillia a, Ch.
Antypas a, M. Lyra a. a Medical Physics Unit, A’ Radiology Department,
National and Kapodistrian University of Athens, Athens, Greece; b Medical
Physics Dep., Iaso Hospital, Athens, Greece; c Radiotherapy Dep., University
Hospital, Rabat, Morocco
Background: In modern radiation therapy with high energy photon
beams produced by linear accelerators, fast and accurate calculation of
the dose distribution in patient’s body is required. Special computer
systems known as treatment planning systems calculate the dose distribution. Medical Physicists use the treatment planning systems for
radiotherapy planning. Every treatment planning system must be
checked for the accuracy of the computed dose compared to measured
dose under several cases, before it can be used clinically. We created an
independent routine in MatLab that calculates dose at any point in the
central axis of a photon beam in water and we used it to check the accuracy of the treatment planning calculation.
Materials and methods: A graphical user interface that calculates point
dose was created in MATLAB language. Percentage depth doses, collimator
scatter factors, phantom scatter factors for several field sizes of Siemens 6
MV linear accelerator were inputted in MatLab and a special code was
generated. A simple form, named VAMLY-plan, has been created and can
be completed to extract dose at any point in the central axis.
The accuracy of the calculations was compared to absolute dose measurements in water with ion chamber.
Point doses for several fields' sizes and several depths in water were
calculated with the Oncentra Masterplan treatment planning system. The
results were compared to the MatLab VAMLY-Plan calculation values
respectively.
Results: The agreement between the Oncentra Masterplan treatment
planning system calculations and the VAMLY-Plan calculation MatLab
routine was better than 2% for any case.
Discussion: Treatment planning systems must be checked thoroughly for
dose calculation accuracy in order to be commissioned for clinical use.
Hand monitor unit calculation is time consuming and often prevents
Medical Physicists from detailed examination of the treatment planning
system. The MatLab calculations routine, VAMLY-Plan, helps Medical
physicists to commission treatment planning systems fast and accurately.
ENERGY RESOLUTION OF THE GAGG:CE SINGLE CRYSTALS WITH
VARIOUS THICKNESS COUPLED TO A SIPM
G. Delimani a, M. Georgiou a,b, P. Papadimitroulas c, P. Papamichalis a, K.
Mikropoulos a, S. David a, G. Loudos a. a Department of Biomedical
Engineering, Technological and Educational Institute of Athens, Athens,
Greece; b Department of Medical School, University of Thessaly, Larissa,
Greece; c Department of Medical Physics, School of Medicine, University of
Patras, Rion, Greece
Aim: Silicon Photomultipliers (SiPMs) are good candidates for the
replacement of common Photomultiplier Tubes (PMTs) because of their
small size, low cost, low operating voltage, robustness, compactness and
they are insensitive to magnetic fields. In this study, the energy resolution,
that have been measured with the SensL's (SPMMicro) photo-detector, is
presented. The SPMMicro is coupled to a new mixed Gd3Al2Ga3O12:Ce or
GAGG:Ce scintillator with seven different crystal size elements (3, 5, 6, 8,
10, 15, 20 mm thickness). All the experimental data have been simulated
with GATE Monte Carlo simulation toolkit which is dedicated for nuclear
imaging applications. The radioactive sources that were used both in the
experiments and the simulations are: 22Na, 137Cs, 57Co, 109Cd. Results
regarding the energy proportionality of the optical detector as well as the
sensitivity achieved were reported.
Methods/materials: GAGG:Ce scintillator is non hygroscopic, with fast
scintillation response and high light yield. The density of GAGG:Ce is 6.63
g/cm3, with effective atomic number equal to 54.4 [1-2]. All GAGG:Ce
scintillator crystals with 3x3mm2 cross section were purchased by Furukawa Co Ltd. The SiPM that was studied is the SPMM-3035 included in
SensL's ScintPack evaluation package. It has an overall area of 3x3mm2,
with cell pitch of 35 mm. We also used a Preamplifier and Power Supply
Module (SPMA4). SPMA4 is comprised of three individual boards: a) a
preamplifier board that interfaces with the detector and provides signal
amplification, b) a power supply board that provides the detector bias
and power for the preamp and c) a shield board between the two to
prevent interference [3]. The applied bias voltage was set equal to +30 V.
The digitization of the pulses was done with the CAEN DT5720 desktop
digitizer. The energy resolution values were calculated applying a
Gaussian fit on the photopeaks with ±10 energy window. The coupling
material used for the optical coupling among the SIPM and the scintillator
crystals was grease (BC-630). All the measurements were conducted in a
black box with stable temperature at +180C controlled by a peltier cooling
system.
Results-Discussion: Experimental and simulated energy resolution values
for seven different GAGG:Ce scintillators under 137Cs irradiation are
summarized in Table 1.
Table 1. Energy resolution for GAGG:Ce with 137Cs. First column shows the
scintillator sizes, the second column shows the simulated results and the third
the experimental results.
GAGG:Ce Scintillator size (mm3 )
GATE Simulation
Experimental values
3x3x3
3x3x5
3x3x6
3x3x8
3x3x10
3x3x15
3x3x20
11.1%
10.1%
10.9%
10.6%
10.8%
11.1%
10.7%
15.8%
13.1%
14.1%
14.4%
11.2%
12.2%
13.6%
The best simulated energy resolution value was computed for the
GAGG:Ce 3x3x5mm3 single crystal equal to10.1%. The best experimental
value measured for GAGG:Ce 3x3x10mm3 equal to 11.2%.
Acknowledgment:
This research has been co-funded by the European Union (European Social
Fund) and Greek national resources under the framework of the “Archimedes III: Funding of Research Groups in TEI of Athens”.
References
[1] J. Iwanowska et al. “Performance of cerium-doped Gd3Al2Ga3O12
(GAGG:Ce) scintillator in gamma-ray spectrometry”, Nucl. Instrum. Meth. A,
vol. 712, pp. 34-40, 2013
Abstracts / Physica Medica 30S1 (2014)
[2] M. Georgiou et al. ”Development of a SIPM based gamma-ray imager
using a Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillator array,” IEEE Nucl. Sci.
Symp.& Med. Imag conf. M21-48, Oct 27- Nov 2, Seoul, Korea, 2013
[3] N. Efthimiou et al. “Initial results on SiPMs performance for use in
medical imaging,” Meas. Sci. Technol. 22 (2011) 114001
COMPARISON OF DIFFERENT DOSIMETRY METHODS FOR 64-ROW
DETECTOR COMPUTED TOMOGRAPHY
M. Gancheva, I. Dyakov, J. Vassileva, D. Kostova-Lefterova, S. AvramovaCholakova. National Centre of Radiobiology and Radiation Protection, Sofia,
Bulgaria
Background: The aim of this work is to study how the CTDI measurement
methods influence results for Multi-Detector Computed Tomography
(MDCT) with beam width less than 40 mm. The current IEC standart
suggests standad dosimetry can be applied for these scanners. Our previous TLD measurements of dose profiles of different MDCT revealed even
for a beam width of 32 mm the integration length of 100 mm in the
definition of CTDI100 is insufficient to evaluate the full dose profile, which
motivated further research.
Materials and methods: The study was performed with Aquilion 64 of
Toshiba. Additionally to the standard dosimetry, four other approaches
were applied. First, suggested by IEC for MDCT with width higher than 40
mm, includes free in air measurements with a standard 100 mm CT
chamber, stepped through the X-ray beam, along the z-axis, at intervals
equal to its sensitive length. Two cases were studied e with integration
length of 100 mm, and of 200 mm. Except measurements with standard
PMMA phantom, secondary approach was implemented with twice-longer
phantom (30 cm length) and two standard chambers positioned and fixed
against each other. Since the inactive area between the two chambers third
and fourth approaches were applied. They comprises measurements with
30 cm long phantom and standard chamber placed in two and in tree
different positions respectively, forming a detection length of 200 mm in
the middle of the phantom and forming a detection length of 300 mm
along the phantom. Phantom measurements of CTDI were made only in
the central hole e CTDIc.
Results: The results indicated that CTDIfree-in-air measured with an integration length of 200 mm for 32 mm wide beam is 13% higher than the
standard method. CTDIc measured in phantom with standard method is
17% lower then CTDIc calculated with IEC method, 32% lower then the
second method, 58% lower then values obtained by the third method and
70% lower then the fourth method.
Discussion: The length of the phantom and the integration length have
strong influence on the result. The study results demonstrated the limitation of the standard method of CTDI measurement for 64-row MDCT.
37
Preliminary Results: Fig. 1 shows the excess dose due to a GNL in 3
different scenarios. In all cases, an increase of dose after the GNL is
observed, which, however, is matched by a corresponding decrease of dose
before the GNL.
The excess dose curves for the GNPs (Fig 2) exhibit significant noise, in
large part due to the much more significant effect of lack of lateral
electronic equilibrium at such small source sizes. After the GNP, the
excess dose for the 100 nm solid and hollow GNPs is similar and extends
to a greater distance than that for the 50 nm GNP. However, the
magnitude of the peak at the location of the GNP is higher for the 50 nm
GNP. Before the GNP, there is clear underdosing for the 50 nm GNP. The
curves for the 100 nm GNPs are more complicated, requiring further
investigation.
Conclusion: Our results indicate that, for GNPs in particular, nanoscale MC
simulations must be carefully designed and implemented, since inherent
perturbations and uncertainties may significantly affect the results.
References
1. Benhalouche, S., D. Visvikis, et al. (2013). “Evaluation of clinical IMRT
treatment planning using the GATE Monte Carlo simulation platform
for absolute and relative dose calculations.” Medical Physics 40(2):
021711.
Fig. 1. Excess dose along the beam central axis due to a 50 nm GNL at: 5 mm depth
in a 20x20x20mm3 water phantom (red), 5 mm depth in a 40x40x40mm3
water phantom (blue), and 15 mm depth in a 40x40x40mm3 water phantom
(green)
DOES THE SETUP OF MONTE CARLO SIMULATIONS INFLUENCE THE
CALCULATED PROPERTIES AND EFFECT OF GOLD NANOPARTICLES?
Dimitris Makris MSc, Spiridon V. Spirou PhD, George Loudos PhD. Dept. of
Biomedical Engineering, TEI Athens, Greece
Background: Gold Nanoparticles (GNPs) are promising radiation therapy
agents due to their cell-killing enhancement effect. Their properties at the
nanoscale level are being investigated using Monte Carlo (MC) simulations,
with little, if any, experimental verification. The purpose of this work is to
investigate whether the setup of the MC simulation itself affects the
results.
Methods and Materials: The GATE MC toolkit (v6.2) was used to simulate
the irradiation of a water phantom containing GNPs and Gold Nanolayers (GNLs). The water phantoms ranged from 1x1x1 to 40x40x40
mm3. GNLs (10, 50 and 100 nm in thickness, length and width same as
those of the phantom), and solid and hollow GNPs (10, 50 and 100 nm in
diameter) were placed at the central axis and at various depths. A realistic 6 MV photon source was placed 2 mm outside the phantom1. The
number of particles generated was 25x106 photons/mm2 for the GNLs
and 108 for the GNPs. The direction of the photons was perpendicular to
the phantom. The source was rectangular and covered the GNL or the
GNP.
Fig. 2. Excess dose along the beam central axis due to a spherical GNP at 5 mm
depth in a 20x20x20mm3 water phantom: 50 nm diameter solid GNP (red), 100 nm
diameter solid GNP (blue), 100 nm outer diameter and 50 nm inner diameter
hollow (shell) GNP (green)
38
Abstracts / Physica Medica 30S1 (2014)
A SURVEY ON AVERAGE GLANDULAR DOSES IN DIGITAL
MAMMOGRAPHY UNITS OF FOUR DIFFERENT MANUFACTURERS
I.A. Tsalafoutas a, Ch. Panaretos b, S. Thalassinou c, I. Georgiou a, A.
Christou d, E. Cassianou e, R. Aggelatou a, E. Yakoumakis f. a Athens General
Anticancer-Oncology Hospital “Agios Savvas”, Athens, Greece; b Diagnostic
Center “Iatriki Merimna”, Petroupoli, Athens, Greece; c N. Papapostolou Ltd,
Psychiko, Athens, Greece; d Diagnostic Center “Christou”, Maroussi, Athens,
Greece; e Diagnostic Center “Ef Frontizein”, Metamorfossi, Athens, Greece;
f
Medical Physics Department, Medical School, University of Athens, Athens,
Greece
Objective: To investigate the average glandular dose (AGD) levels in four
mammographic facilities equipped with digital units of different manufacturers. All units calculate the entrance surface air kerma (ESAK) and
average glandular dose (AGD) values in real time.
Methods: 1899 digital mammograms performed in four units [A: GEEssential (#461), B: Siemens-Mammomat Novation DR (#505), C: HologicLorad Selenia (#526) and D: Fujifilm-Amulet (#407)] were collected. Using
appropriate software (DICOM Info Extractor), all dose related parameters
were extracted from DICOM headers into four Microsoft Excel files (one for
each unit). These files contained embedded equations and algorithms to
allow for the retrospective calculation of ESAK and AGD values automatically, using the DICOM header info.
Results: Mean AGD and CBT values and ranges [values within brackets]
were: A: 1.39 mGy [0.87e2.85] for CBT¼ 5.8 cm [2.7e9.8], B: 1.34 mGy
[0.80e3.1] for CBT¼ 4.7 cm [1.6e8.9], C: 1.06 [0.44e2.11] for CBT¼ 5.6 cm
[2.3e9.3] and D: 2.36 mGy [0.94e4.3] for CBT¼ 5.2 cm [2.1e7.9]. In unit A
the Rh/Rh filer combination was used for the majority of mammograms, in
unit B the W/Rh (exclusively), in unit C the W/Rh, while in unit D the Mo/
Rh. Compared to the EUREF’s acceptable and achievable AGD level curves,
for unit A almost all AGD values were below the achievable level curve
(except ~1% performed with the high dose protocol), for unit B ~3% were
above the acceptable and ~10% above the achievable level curves, for unit C
all AGD values were below the acceptable and only ~2% was above the
achievable level curves. For unit D there was a considerable number of AGD
values above the two curves for two reasons: the high dose protocol was
often used and the CBT value was underestimated by about 1 cm, leading
to low kV selection and considerable AGD overestimation. Comparisons of
real time ESAK and AGD values with retrospective calculations will be
presented.
Conclusion: Dose surveys in digital mammography units should be performed periodically in order to check for conformance with EUREF’s proposed AGD levels and detect possible problems that lead to high patient
doses or false AGD indications.
DOSIMETRIC COMPARISON OF GAMMA ANALYSIS OF BRAIN AND HEAD
AND NECK INTENSITY MODULATED RADIATION THERAPY TREATMENTS
USING GAFCHROMIC EBT3 FILMS AND 2D ION CHAMBER ARRAY
MATRIX
€
Yıldıray c, Tokatli
Alkaya Fadime a, Üzümlü Evren a, Yaray Kadir b, Ozgüven
a
€
_
Füsun a, Aksakal Oznur
. a Medicana International Istanbul
Hospital,
b
_
Erciyes University, Medical
Radiation Oncology Department e ISTANBUL;
_ c Cumhuriyet University,
Faculty, Radiation Oncology Department- KAYSERI;
_
Medical Faculty, Radiation Oncology Department - SIVAS
Background: Patient based quality assurance (QA) procedures for IMRT
patients is a daily routine now to be sure about the agreement of treatment
planning system (TPS) calculated dose and the dose delivered by the lineer
accelerator.
Materials and methods: The comparison of the dose distributions by
using Gafchromic EBT3 film and PTW 2D Array 729 has been done for 15
brain and head and neck IMRT patients (plans with ECLIPSE TPS) treated
with 6 MV photon beams (Varian 2100 DHX Clinac Linac with 120 millenium dMLC). The parameter of the verification method is gamma index
(g-index) method. The acceptance limits for g calculation we have used are
3% for dose agreement and 3mm for distance to agreement parameters.
Results: The qualitative dose distribution comparison was performed using
composite dose distribution in the measurement plane and profiles along
various axes for TPS vs. EBT3 film and TPS vs. PTW 2D Array 729. The
quantitative analysis between the calculated and measured dose distribution was evaluated using g-index. The percentage of pixels matching with
the data set g values for EBT3 films are higher than g values for PTW 2D
Array 729. After measurements it is found that for 2D Array average g values
of head and neck patients are 90,105 and for EBT3 films 95,33; for 2D Array
average g values of brain patients are 95,37 and for EBT3 films 96,73.
Discussion: If your g values are close but under acceptance limits, EBT3
films would be a good method to check your dose distributions. However
due to simplicity and fast evaluation process of array detectors, it can be
routinely used in busy departments without compromising the measurement accuracy.
NEW DISCOVERIES IN g-RAY ATTENUATION MEASUREMENTS FOR
MEDICAL PHYSICS
E. Adamides a, A. Kavadjiklis a, b, S.K. Koutroubas a, N. Moshonas a, c, A.
Tzedakis d. a Department of Physics, Chemistry and Materials Technology
STEF, TEI Piraeus, P. Ralli and Thivon 250, Egaleo, Greece; b School of
Applied Mathematical and Physical Science, National Technical University
of Athens, Athens, Greece; c School of Electrical and Computer Engineering,
National Technical University of Athens, Athens, Greece; d Department of
Medical Physics, University Hospital of Heraklion, Crete, Greece
In the present work we report on a new way to evaluate the buildup factor
in g-ray attenuation which is crucial in determining the correct exposure
dose at the target in Medical Physics.
Based on our detailed g-ray attenuation experiments using 60Co radioactive
source and absorbers of lead and iron we found out that the g rate after
passing an absorber of thickness x in space, i.e. , is a step-wise function of x.
For each mean free path the function can be fitted quite well by a straight line.
From its slope we define, for the first time, the buildup coefficients ki as the
decrease in m. The physical meaning of ki is that they refer to the Compton
scattered radiation through the i-th mean free path. The buildup factor
propagated through the i-th mean free path is given by our model1 as:where
xm is the length of the mean free path. Our model comes much closer to the
physical understanding of the g-ray attenuation process compare to the
previously used mathematical formulae for the buildup function.
80
9
1
< nX
=
1
Bi Eg ; mx ¼ exp @
kj ki xm A þ ki x
:
;
j¼1
A close look into our detailed g-ray attenuation date revealed special
features like a pigmy resonance at the end of the mfp which may mislead
the determination of the parameters used in the previous buildup functions. These weak bumps can become important in the case of a strong
radioactive source in radiation protection.
A comparison of our experimental results with Monte-Carlo calculations
showed systematic deviations which could be explained by the introduction of a new mechanism to the already known interactions of radiation
with matter. On this new mechanism we shall comment.
Our model for determining the buildup factor can be easily applied and
comprehended from the physics point of view in medical physics educational laboratory thus giving to the student a more realistic interpretation
of the g-ray attenuation process in matter.
References
1. E. Adamides, A. Kavadjiklis, S.K. Koutroubas, N. Moshonas, A. Tzedakis and K. Yiasemides. “Reduction of the buildup contribution in
gamma-ray attenuation measurements and a new way to study this
experiment in student laboratory” Phys. Educ. 49(1), 55e60, 2014
IN-VITRO STUDY OF FLOW RELATED CHARACTERISTICS IN GLASS
STENOTIC TUBES USING MAGNETIC RESONANCE ANGIOGRAPHY
Patatoukas George, Argyropoulos George, Kazerou Aspasia, Christopoulos
George, Efstathopoulos Efstathios. Medical Physics Unit, 2nd Department of
Radiology, Medical School, University of Athens, Greece
Abstracts / Physica Medica 30S1 (2014)
Background: Arterial blood flow characteristics can be studied nonedinvasively using Magnetic Resonance Imaging. Magnetic Resonance
angiography provides real-time velocity information. This functional information is of paramount importance in the study of arterial blood flow
characteristics and can lead to the quantification of individual hemodynamic-related parameters in any patient; it can also assist in the development of diagnostic tools to quantify artery disease and it can contribute
to the design of devices that mimic blood flow either for educational
purposes or for developing tools that alter blood flow.
Materials and methods: To simulate blood circulation in stenotic arteries,
a positive displacement pump driven by an electrocardiogram (ECG)
generator was used. Water was considered as the flow medium of choice.
Three different glass tubes, each exhibiting a stenotic geometry were
studied. The percentage of the stenosis was unknown. The glass stenotic
tubes were placed between two gelatin layers to mimic tissue-equivalent
material and to enhance MRI signal acquisition. Imaging was performed
with a Philips Intera 1.5T MRI system using phase contrast sequences.
Results were compared to CT image-based stenosis quantification.
Results: Velocity values were acquired and recorded pre- and poststenotically for each glass tube. Stenosis percentage quantification was
performed using the MRI-velocity information. In addition, Signal To Noise
Ratio (SNR) calculation was performed around the stenotic vicinity (preand post-) and their ratio was noted and related to stenosis percentage.
Furthermore, velocity profiles were acquired, studied and compared to the
theoretical parabolic profile. Finally the MRI flow-based calculated values
for each of the stenosis percentage were compared to those extracted
using CT imaging anatomy.
Discussion: Higher flow velocity values were observed post-stenotically.
The length of the induced jet and the consequent signal loss were related
to the stenosis percentage. Turbulent flow and dispersion of velocity
values is an important factor of signal lose in the stenotic vicinity. CT based
and MR based stenosis quantification exhibited differences. Further steps
need to be done in MR imaging to fully appreciate and quantify each factor
that influences blood flow.
S.E.Y.Y.P INSPECTIONS RELATED WITH RADIOLOGY DEPARTMENTSLABORATORIES FOR THE IMPROVEMENT OF PUBLIC HEALTH IN
GREECE
E. Kounadi, I. Manousopoulou, N. Kallitsantsis, M. Adamopoulou, V.
Panagopoulos, H. Merentitis, P. Sakellariou, M. Rekkas, S. Sampatakakis. Ministry
of Health in Greece, SEYYP, Athens Greece
Background: In Greece, under current legislation the Radiology Departments-Labs (DL) must be equipped with specific ionizing and nonionizing radiation diagnostic systems. Special operating license required
for Radiology DL operation which must be renewed every five years. Also
quality control program for each system is mandatory.
The purpose of this work is to present the results of SEYYP inspections
related with Radiology DL, i.e. the problems identified, and proposals that
can eliminate these problems.
Materials and methods: The SEYYP where its services aiming to improve
the Public Health, during the years 2012-2014, have been carried out inspections related with public and private Radiology DL in urban areas and
in the countryside. In this inspection procedure was checked and implicated, not only the Radiology DL, but also the related public health services.
Inspection subjects, was the licensing of DL and the proper operation of
them. Also issues related to magnetic tomographs (MRI) licensing and
statistical data related to the computed tomography (CT) examinations, in
the country, was explored.
Results: At Radiology DL, where problems with their licensing, was found
after the inspection forced to comply with the current legislation. In some
of them monetary penalties was imposed or they were forced to close
down for some time. Deficiencies in current legislation for the MRIs
licensing was identified and proposals for the improvement was formulated. In the conduction of the CT exams, great variation, in the CT exams
number per 1,000 inhabitants, between public hospitals from different
Local Regions, was found. Also great variation at the number of exams per
CT system, for the year 2013, in Public Hospitals in the country was
identified.
39
Discussion: The recommendations that were performed at checked and
implicated public services and Radiation DL, were aiming to improve the
public health in the country. Thus proposals for a more efficient use of
manpower and medical instrumentation in public Hospitals, taking into
account the economic situation of the country, was performed. Furthermore proposals to reduce the induced demand of the CT exams in the
country were made.
EVALUATION OF THE ACCURACY OF THE ELECTRON TRANSPORT
ALGORITHMS OF THE MCNP6 AND EGSNRC MONTE CARLO CODES
USING THE FANO THEOREM
E. Zoros, E. Pappas, E. Pantelis. Medical Physics Laboratory, Medical School,
University of Athens, 75 Mikras Asias, 11527 Athens, Greece
Background: Monte Carlo (MC) codes are commonly used for simulating
ion chamber response in photon or electron beams. Besides cross section
libraries, accurate modelling of the ion chamber and beam quality, the
accuracy of the obtained results depends also on the electron transport
algorithm (ETA) parameters used by the MC codes. In this study, the accuracy of the ETA of the recently released MCNP6 as well as of the EGSnrc
MC codes is evaluated using the Fano theorem.
Methods: MCNP and EGSnrc simulations were performed for a cylindrical
infinite graphite slab phantom containing a cavity delimited by two parallel planes. The cavity was filled with ‘gas’ of the same composition as
graphite but with mass density of a thousand-fold smaller. Identical cross
sections (including the density effect) were used for both the cavity walls
and the gas. Electrons with initial kinetic energies ranging from 0.05MeV
to 10MeV were generated in the wall and in the gas with a uniform intensity per unit mass. The initial emission direction was either perpendicular or parallel to the gasewall interface motivated by the design of
pancake- and thimble-type chambers. The degree of violation of the Fano
theorem was quantified for the default parameters of the EGSnrc and as a
function of the ESTEP parameter (determining the number of sub-steps per
energy step) for the MCNP codes, respectively. For the MCNP simulations
the new energy indexing method was used. The effect of the ESTEP value
on simulation efficiency was also studied.
Results: Results showed that EGSnrc verifies Fano theorem within 0.1% for
the studied electron energies. Corresponding MCNP results showed that
the default ESTEP value of 3 should be used only for electron kinetic energies of 0.05MeV. As energy increases a greater ESTEP parameter should
be used, taking a value of 30 for 10MeV electron energy, to obtain
dosimetry results with 0.1% accuracy. Increasing ESTEP up to 30 downgrades time efficiency, by a factor of 4 for 1MeV electron energy.
Discussion: This work is intended to help users adopt the optimal parameters of the MCNP and EGSnrc MC codes that guarantee high-accuracy
dosimetry calculations.
PRE-RADIOTHERAPY (RT) TREATMENT PLANNING FACTORS TO TAKE
INTO ACCOUNT IN ONCOLOGIC PATIENTS WITH INFLAMMATORY
BOWEL DISEASES (IBD)
M. Tolia a, A. Zygogianni a, G. Kyrgias b, K. Theodorou b, C. Kappas b, J.
Kouvaris a, V. Kouloulias a. a 1st Department of Radiology, Radiation
Oncology Unit, Aretaieion University Hospital, Vassilissis Sofias 76, 115 28,
Medical School of Athens, Greece; b Radiotherapy Department, Larissa
University Hospital, Medical School of Thessaly, Greece
Background: IBD represents a chronic intestinal inflammation in the
absence of an infectious or dietary cause. IBD can produce many similar
clinical characteristics as RT toxicity and has been considered a relative
contraindication for the delivery of RT. There is a relative scarcity of data
concerning the safety of irradiation for oncologic patients with an IBD
history. We evaluated the optimal treatment factors in order to reduce the
risk of RT bowel toxicity in oncologic IBD patients.
Materials and methods: A review of all published reports was performed
by Medline.
Results: Modern techniques such as image-guided tomotherapy or
volumetric-modulated arc therapy may possibly permit the administration of higher doses with less bowel toxicity. Use of IORT and brachytherapy (vaginal implant, perineal proton boost) in combination of
40
Abstracts / Physica Medica 30S1 (2014)
photon radiotherapy in order to deliver supplemental irradiation.
Brachytherapy in early-stage prostate cancer should be considered. Special positioning (prone or decubitus) and fully distended bladder to
minimize bowel irradiation. Surgical omentoplasty, dexon, vicryl mesh
and tissue expanders to mobilize the bowel away from irradiated area.
Surgical clips placement are useful for precise tumor localization and
delineation of tumor bed. Delivery of only a fraction, not higher than
1.8e2 Gy daily. Reduction of total dose and eventually employment of
scheduled rest periods during RT. Hormonal therapy could shrink the
prostatic gland (downsizing) in prostate cancer patients and thus reduce
the radiation field size. Steroid-induced femoral head osteonecrosis represents an aseptic and ischemic disease developing after chronic
administration of steroids in IBD patients. Keep doses within femoral
head tolerance. Care must also be taken to age associated osteoporosis in
geriatric patients.
Discussion: A special attention should be given to RT dose and technique,
in order to minimize post-RT complications.
NATIONAL PATIENT DOSE SURVEY IN DENTAL CBCT AND ELABORATION
OF NATIONAL DRLS
D. Petrov, J. Vassileva. National centre of radiobiology and radiation
protection, Sofia, Bulgaria
Background: The aim of this study is to present results from the national
patient dose survey in cone beam CT (CBCT) used in dental practice, and to
elaborate national diagnostic reference levels (DRL).
Materials and methods: Patient doses were measured with calibrated
kerma-area product (KAP) dosemeter Diamentor E2 (PTW Freiburg),
installed on the tube housing exit. Patient head was simulated with a
standart CT head phantom. The size of the radiation field was measured
with Gafchromic film placed on the imaging detector. Organ doses and
effective dose E were calculated with PCXMC v.2.0 (STUK) by Monte Carlo
simulation. Pilot measurements were performed on three CBCT: one
NewTomVG (QR-Italy)and two ILUMAeImtec 3M (USA).
Results: CBCT dose varied substantially depending on the device, field of
view (FOV), and selected technique factors. Up to 3 fold differences were
found between KAP for adult patient, with lower values for the system
NewTomVG, working with tube current modulation.
Discussion: Complete set of ongoing measurements and analysis will be
presented, as well as findings and conclusions.
COMPARISON OF 111IN-OCTREOSCAN AND 99MTC-TEKTROTYDE IN
TECHNICAL MATERS [RADIOLABELING, QUALITY CONTROL, INJECTED
DOSES AND PATIENT RADIATION EXPOSURE]
M. Papachristou, І. Xirafi, I. Datseris. Department of Nuclear Medicine e
PET/CT General Hospital of Athens “Evaggelismos”
Introduction: The imaging of positive SSTR's tumours with radiolabeled
analogues of somatostatine has a broad use in oncology. The radiopharmaceutical of choice was 111In-DTPA-D-Phe-Octreotide. The use of 111In is
facing some problems because it depends in cyclotron production which
leads to restricted availability and very high cost.
So to overcome these problems the use of 99mTc was selected as “easy- toget” radionuclide with low cost. The 99mTc-EDDA/HYNIC-Tyr3-Octreotide
can image the tumours with SSTRs.
We report a comparison between the 111In-Octreoscan and 99mTc-Tektrotyde in radiolabeling, quality control, injected doses and patient radiation exposure.
Methods: The radiolabeling procedure of both radiopharmaceuticals were
carried out according to the SPC of the products and the European Pharmacopeia. After the labelling, both drugs undergo quality control which
includes pH measurements, visual control and instant thin layer chromatography (TLC), in order to be released.
One vial 111In-Octreoscan is used for one single patient and one vial of
99m
Tc-Tektrotyde is used for two patients. The dose of the 111In is ~5 mCi
and the dose of 99mTc is ~ 20 mCi in accordance with our Department
protocols.
Results: To label 111In-Octreoscan takes 30 min and to label 99mTc-Tektrotyde takes almost 50 min. The quality control of 111In needs only one TLC
system (~ 20 min) where for the 99mTc needs two TLC systems (~ 40 min).
The patient’s injected with111In have higher radiation exposure than the
patients injected with 99mTc.
The imaging protocol of 111In is a 2-day, one day longer than 99mTc (1-day
protocol).
Conclusions: 111In- Octreoscan is a well standardized and well know
radiopharmaceutical with easy labelling procedure and quality control. Its
cons are the 2-days protocol, the higher radiation exposure, the higher cost
and the short availability.
99m
Tc- Tektrotyde is a new radiopharmaceutical which isn’t well defined.
Its radiolabeling procedure and quality control are long. 99mTc-Tektrotyde
pros are the 1-day protocol, the lower radiation exposure, the lower cost
for two patients and it's broad availability.
Both radiopharmaceuticals have advantages and disadvantages. The choice
depends on the Nuclear Medicine Department’s resources, protocols and
qualification standards.
BLOODLESS MEASUREMENT OF HEMATOCRIT
M. Adamopoulou a, G. Fountos b, E. Kounadi a, M. Rekkas a. a Ministry of
Health in Greece, SEYYP, Athens, Greece; b Department of Biomedical
Engineering, TEI of Athens, Greece
Background: The direct estimation of the hematocrit at surgery without
blood sampling procedures and laboratory analyzes, could yield significant time savings for the clinician, especially when managing
emergencies.
The purpose of this study is the construction of a biotechnology device, in
order to determine the hematocrit value, in a bloodless non invasive
method, that can be used for an immediate diagnosis.
Materials and methods: Using technology similar to that of an “oxymeter”, we are in the process of manufacturing a portable device, which in
contact with a large vase (jugular, femoral or brachial artery etc), will be
able to count the number of red blood cells per cubic millimeter. The red
blood cells are identified by their concave surface, separating them from
the remaining blood cells (white blood cells , platelets, etc), where light
scattering occurs in a different way.
Results: After the completion of the prototype which called «Hemo-detector», measurements of hematocrit will be performed using this device
to patients. The hematocrit values measured will be compared with them
upon laboratory tests (blood draw) to assess the reliability of this novel
non invasive method.
Discussion: The immediate and bloodless measurement of hematocrit is
an important help for the clinician where he will be able to evaluate a
significant number of diseases. Also, pain and stress for the patient can be
avoided. Furthermore, since this will be a low cost method resources for
the patient as well as social health funds can be saved.
THE ROLE OF DOSIMETRIC CALCULATIONS IN OPTIMIZING PEPTIDE
RECEPTOR RADIONUCLIDE THERAPY BY [177LU-DOTA0, TYR3]
OCTREOTATE
Irini Baka a, Maria Argyrou a, Marina Michalitsi a, Alexia Valassi a, Agapi
Ploussi a, Maria Lyra a, b. a Radiation Physics Unit, 1st Department of
Radiology, Aretaieion hospital, University of Athens, Greece; b Nuclear
Medicine Section, 1st Department of Radiology, Aretaieion hospital,
University of Athens, Greece
Aim: Response and toxicity prediction is essential to the implementation
of Peptide Receptor Radionuclide Therapy (PRRT) for neuroendocrine tumors. Radiolabelled somatostatin analogue [177Lu-DOTA0, Tyr3] octreotate
stands as a promising therapy tool. Specific dosimetry is a crucial factor in
patient treatment planning. Dosimetric techniques implemented in our
Institution are presented.
Methods: In our Institution, neuroendocrine tumor treatment, by
radiopeptide infusion via intrahepatic arterial catheterization, is a
well established technique. Kidney protective agents are also included
in our protocol. The individualized patient dosimetry calculations were
based on planar and SPECT scintigraphy images. Counts were
Abstracts / Physica Medica 30S1 (2014)
determined in a region of interest (ROI) around the tumor, liver, kidneys and spleen. In planar technique, the ROIs were drawn in both
anterior and posterior images while in SPECT counts measured per
slice. For counts conversion to activities, system calibration factors
were measured. Planar and SPECT images of cylindrical water - filled
phantom, with five different known amounts of activity, were obtained.
Corrections for scatter attenuation, collimator efficiency and detector
response were obtained. In bone marrow dosimetry, blood based
methods were used as in 177Lu images no significant radiopeptide data
of bone or red plasma activity are displayed. Absorbed doses were
calculated using MIRD formalism and S values were calculated using
the RADAR system.
Results: The calculated absorbed doses to organ per unit administered
activity, for both planar and SPECT techniques, were comparable.
On average, the tumor dose was [4-40] mGy/MBq, the kidney
dose [0.25-1.05]mGy/MBq, the bone marrow dose [0.01-0.13]mGy/MBq,
the spleen dose [0.3-2.1]mGy/MBq and the liver dose [0.05-0.34]mGy/
MBq.
Conclusion: In order to deliver higher dose to tumor and avoid kidneys
and red marrow toxicity, accurate individualized dosimetry is obligatory.
Furthermore, the results quantitatively confirm the therapeutic efficacy of
transhepatic administration and introduce 177Lu labeled peptide as an
ideal for peptide receptor radiotherapy.
IMPLEMENTATION OF THE NEW TG-51 ADDENDUM IN CLINICAL
PRACTICE
S. Papageorgiou a, P. Georgolopoulou b, S. Nikoletopoulos a, b, G.
Laskaratos a, b, S. Xenofos a, b. a Physics Department, IASO Hospital, Athens,
Greece; b Physics Department, “St. SAVVAS” G. Anticancer Hospital, Athens,
Greece
Introduction: Since the original publication by AAPM of the TG-51 protocol for clinical reference dosimetry of high-energy photon beams in
1999, changes have occurred in the dosimetry chain that required revision
of the protocol. In the recently published addendum (2014) more accurate
Kq values are presented for currently available chamber models and
specifications are provided for reference-class dosimetry chambers. This
work evaluates the implementation of the new addendum in the clinical
practice of two institutions.
Method: The set of MV dosimetry chambers available for clinical work was
evaluated in view of the recent recommendations. Chamber characteristics
including settling, polarity dependence, recombination correction and
stability, were measured so as to evaluate compliance with suggested
specifications for a reference dosimeter. Absolute dose was specified using
new Kq values, based on Monte Carlo calculations, for a range of high
energy clinical beams.
Results: Absolute dose determination for the typical range of clinical high
energy beams using the new recommended values for beam quality
correction shows insignificant changes for corrections determined by kQ ¼
A + B $ 10 e 3 $ % dd (10)x + C$10 5 $ (% dd(10)x) 2 with A, B, C ¼ fit parameters and 63 < % dd (10) X < 86. Application of chamber-specific
correction is not required for reference-class dosimeters. Factors contributing to combined uncertainties, as analyzed in the TG-51 addendum, are
addressed.
Conclusions: More accurate, Monte Carlo based, kq values can now
be applied for absolute dosimetry in radiotherapy clinics equipped
with modern design chambers. Selection of a reference dosimeter
can be based in a given chamber’s compliance with specific performance recommendations that exclude small field dosimetry instruments.
EFFECT OF METALLIC SPINAL IMPLANT ON RADIATION THERAPY DOSE
DISTRIBUTION: A CASE STUDY
S. Kanellopoulou a, I. Stamatelatos a, A. Miliadou b, P. Georgolopoulou c, J.
Kalef-Ezra d. a Institute of Nuclear & Radiological Sciences, Technology,
Energy & Safety, National Centre for Scientific Research 'Demokritos' Aghia
Paraskevi, Greece; b Radiation Oncology Department, “Saint Savvas”
41
General Anticancer Hospital of Athens, Greece; c Department of Medical
Physics, “Saint Savvas” General Anticancer Hospital of Athens, Greece;
d
Department of Medical Physics, University Hospital of Ioannina, Ioannina,
Greece
Introduction: Presence of metallic implants in radiotherapy patients affects calculated dose distributions and hence, clinical decisions on the
optimum treatment scheme. Monte Carlo simulations have been shown to
improve calculation accuracy in such cases. In this work Monte Carlo tools
were used to determine the dose distribution in the case of a spinal
implant patient in need of radiotherapy.
Method: A patient was planned for radiotherapy of a primitive neuroectodermal tumor in the vicinity of a metallic spinal implant. Both the
implant and the spinal cord had to be included in the irradiated volume,
raising concern over the accuracy of the treatment dose calculations.
The treatment plan was recalculated using the collapsed cone convolution algorithm and a Monte Carlo model of the patient was developed
using the MCNP code. Dose perturbation due to the implant was
calculated.
Results: The presence of the implant affected significantly the dose
distribution in close vicinity, causing increased backscatter and attenuation. Nevertheless, the dose to target volume and critical organs was
not affected and the results obtained by the collapsed cone convolution
algorithm could still be considered valid for calculating daily and total
dose to the target volume and the spinal cord. Treatment was
completed and the patient was free from disease and side effects at the
2-year follow up.
Conclusion: Although this study was focused on a specific case and results
therefore cannot be generalized, it showed the important role of Monte
Carlo tools in evaluating the accuracy of dose calculations in cases where
metallic implants are involved in the treatment field.
3D SPECT THYROID VOLUME
ALGORITHM IN MATLAB
QUANTIFICATION
BY
THYR-VOL
S. Synefia a, M. Gavrilelli c, A. Valassi a, M. Argyrou a, M. Rouchota a, J.
Floros a, M. Mihalitsi a, I. Baka a, M. Lyra a, b. a Radiation Physics Unit, 1st
Radiology Department, University of Athens, Athens, Greece; b Nuclear
Medicine Section, 1st Radiology Department, University of Athens, Athens,
Greece; c Paediatric Nuclear Medicine Center, Athens, Greece
Purpose: The aim of this work consists of a method of determination of
the thyroid gland’s volume using the SPECT data in order to calculate
the absorbed patient dose from the radioactive substances injected to
the patient during thyroid treatment. Further than thyroid function
diagnosis, thyroid SPECT scintigraphy is used for thyroid volume estimation. In this study, a MatLab algorithm which integrates 3D visualization is used and thus volume estimation of the thyroid gland is
achieved.
Materials and methods: 14 patients completed thyroid SPECT examination by a gamma camera GE SPECT Star Cam4000. SPECT image acquisition
was performed for angles -90 to +90 degrees, in 32 projections. Images of
thyroid gland were reconstructed by the GE Volumetrix software in the GE
Xeleris-2 processing system using Ramp and Hanning filters. Dicom data
was extracted for each patient and an algorithm that integrates 3D visualization has been used for image processing analysis by MatLabR2012b.
We used Thyroid transaxial slices in Dicom format and we created Thyr-Vol
algorithm by Matlab. Ellipse ROIs are created around each thyroid lobe
while rectangular ROIs include both lobes uptake data. Matrices of the
maps of the counted voxels of the slices of the organ were created. Their
total is multiplied by the elementary voxel size in mm to obtain the final
organ volume. The appropriate threshold value was identified by creating
intensity isocontours.
Results: The “Thyr-Vol” MatLab algorithm, we have created, detects
the segmented regions automatically and the outer contour can be
specified. Therefore, the thyroid volume was evaluated and reconstructed as 3D image based on the threshold value. Using this method,
numerical errors are eliminated because the images are filtered and
reconstructed.
42
Abstracts / Physica Medica 30S1 (2014)
Discussion-Conclusion: Thyroid gland volume estimation in 3D
images will give confidence in accurate absorbed patient treatment
dose calculation. We demonstrate a method that determines the thyroid
gland volume by using SPECT gamma camera data. These data are
being processed by a mathematical algorithm “Thyr-Vol” that we
created using MatLab language, in order to calculate thyroid volume
and mass. Volume and mass calculations are very useful in Nuclear
medicine therapy.
A RADIAL GRADIENT-BASED SEGMENTATION
MICROCALCIFICATIONS IN X-RAY MAMMOGRAPHY
METHOD
FOR
Nikolaos Arikidis a, Spyros Skiadopoulos a, Filippos Sakellaropoulos a, Anna
Katerina
Vassiou a,
Alexandra
Kazantzi b,
Lena
Karahaliou a,
a
a
Department of Medical Physics, School of Medicine,
Costaridou .
University of Patras, Patras, Greece; b Medical Diagnostic Center “BDiagnosis”, Patras, Greece
Background: Shape analysis of individual microcalcifications contributes in the diagnosis of microcalcification clusters in X-ray mammography. Precise segmentation is a prerequisite for developing computeraided diagnosis (CAD) schemes for microcalcification clusters.
Challenges in automated microcalcification segmentation concern
variability in microcalcification shape and size, low distinguishability
from surrounding tissue, as well as image noise. This study focuses
on performance evaluation of an automated microcalcification segmentation method with respect to accuracy and time efficiency, fulfilling requirements of a content-based image retrieval (CBIR) CAD
scheme.
Materials and methods: A two-stage segmentation method was
developed. Initially, a circle containing a microcalcification is manually
defined and image gradient is sampled within the circle in polar coordinates (dUi) for 16 orientations, for each grey level iso-contour
curve. The grey level iso-contour curve corresponding to the maximum
image gradient is estimated (dUmax) providing initial contour pixel
estimates, subsequently transformed to Cartesian coordinates. Finally,
the contour is optimized by an active contour model, overcoming
problems concerning microcalcification grey level spatial variations
and image noise (contour leakage). The proposed method was
compared with a single-stage radial gradient-based segmentation
method. Segmentation accuracy was quantitatively evaluated employing the area overlap measure (AOM), by comparing automated
segmentations to expert manual delineations derived by two radiologists in consensus. The sample consists of 120 individual microcalcifications originating from 20 clusters of the DDSM database.
Microcalcifications spanned a wide range of shapes, sizes and background mammographic parenchyma. The segmentation method was
incorporated in a home-developed software. Time performance was
assessed on individual-microcalcification segmentation basis, as well as
on a cluster-basis.
Results: The proposed method achieved AOM of 0.67±0.21, outperforming statistically significantly (p<0.001) the radial gradient-based
method (AOM: 0.45±0.18). Real time segmentation for individual
microcalcifications is achieved, while approximately one minute is
required for segmenting a total of 5 microcalcifications within a
cluster. Time is independent of seed pixel, circle radius, number of
initial contour pixel estimates and shape of microcalcification, while is
slightly dependent on size of microcalcification and active contour
parameters.
Discussion: The proposed segmentation method is accurate and timeefficient in case of microcalcifications of varying shape and size in presence
of dense parenchyma.
QUANTITATIVE DIFFUSION WEIGHTED IMAGING AT 3T FOR BREAST
CANCER DIAGNOSIS: ADC HISTOGRAM ANALYSIS
Anna Karahaliou, Katerina Vassiou, Nikolaos Arikidis, Spyros
Skiadopoulos, Lena Costaridou. Department of Medical Physics, School of
Medicine, University of Patras, Patras, Greece
Background: Diffusion Weighted Imaging (DWI) accounts for a promising
technique for the identification of imaging-based biomarkers for cancer
diagnosis, prognosis and monitoring response to therapy. In lack of standardized approach/scheme for quantitative DWI of the breast, current
state-of-the-art focuses on defining a diagnostic ADC threshold, i.e. mean
value of lesion ADC for differentiating malignant from benign lesions. A
few studies, however, have exploited statistics reflecting lesion ADC heterogeneity. The current study investigates the feasibility of histogram
statistics in capturing ADC lesion heterogeneity and differentiating malignant from benign lesions at 3 T DWI.
Materials and methods: The dataset consists of 89 histologically verified
breast lesions (51 malignant, 38 benign) of patients undergoing DW-MRI
at 3 T (b-values 0, 900 s/mm2). ADC maps were generated for a slice
representative of lesion largest diameter. An expert radiologist manually
delineated lesion contour on ADC map, defining the lesion region of interest to be subjected to histogram analysis. Specifically, feature extraction considered mean, standard deviation, skewness, kurtosis, entropy,
maximum, minimum and range of ADC. The ability of histogram features
in discriminating malignant from benign lesions was investigated by
means of a least squares minimum distance classifier. The area under
Receiver Operating Characteristic curve (Az) was considered for evaluating classification performance. The feasibility of histogram features in
identifying highly aggressive carcinomas is also considered, by investigating correlation to established prognostic indices (histopathological
factors).
Results: Malignant lesions demonstrated statistically significantly lower
average value of feature ADC mean (0.99 x103 mm2/s) as compared to
benign lesions (mean ADC: 1.44x103 mm2/s). Malignant lesions demonstrated increased average value of ADC entropy (5.83) reflecting increased
ADC heterogeneity, as compared to benign ones (5.60). The feature mean
ADC achieved the highest classification performance of Az¼0.87±0.04,
which further increased to Az¼0.91±0.03 when combined with features
ADC entropy and ADC minimum.
Discussion: Quantitative DWI by means of ADC histogram analysis improves differentiation of malignant from benign lesions and may
contribute in breast cancer prognosis.
DEVELOPMENT OF QUALITY CONTROL PROTOCOL IN LINAC-BASED
STEREOTACTIC RADIATION THERAPY
Drossatou Kelly a, Konidari Aikaterini b, Kantemiris Ioannis b, Diamantopoulos
Stefanos b, Zaverdinos Panagiotis c, Dimopoulos JCA d. a MSc in Medical
Physics; b Medical Physics Dpt, Radiation Oncology division, Metropolitan
Hospital, Greece; c Director of Medical Physics Dpt, Radiation Oncology
division, Metropolitan Hospital, Greece; d Director of Radiation Oncology Dpt,
Metropolitan Hospital, Greece
Stereotactic Radiation Therapy (SRT) and Stereotactic Radio Surgery (SRS)
are advanced oncologic treatment modalities, which apply conventional or
hypofractionated doses of radiation. The dose is mainly delivered with
small fields and sometimes with accelerated schedules (1e5 fractions)
within a short time period. Despite the high dose per fraction which is
delivered with SRS, clinical reports using these stereotactic approaches,
showed high local tumor control rates, coupled with low incidence of
serious side effects.
Because of the high dose per fraction which is applied with SRS, the
acceptable margin of error is significantly smaller than that of conventional radiotherapy. Overdosage of adjacent normal tissues, even if this
occurs only in a single fraction, could escalate the risk of serious complications significantly. The low output factors for small fields which require
delivery of a high number of monitor units, are further increasing the
associated risk.
The majority of accidents are attributed to human errors. Therefore, the
implementation of robust Quality Assurance (QA) processes to minimize
these errors is inevitable. There is no established QA protocol for LINAC
based SRS and SRT systems existing in Greece. This report presents a
dedicated Quality Control Protocol which was developed for the Novalistype SRS/SRT system. Essential QA items and dedicated tolerance ranges
were selected in order to develop a proper QA protocol. Subsequently, an
Abstracts / Physica Medica 30S1 (2014)
anatomical phantom was used for execution of selected QA items and the
evaluation of overall QA state. Finally, the measured values served as a
reference.
Although there is a broad range of specific QA processes and procedures
for stereotactic program elements, generally, they can be grouped in two
main categories: Mechanical accuracy QA part and radiation delivery QA
part. The mechanical accuracy QA part is comprised of the radiation
generation machine QA part, the assistive devices QA part and the multileaf collimator QA part. The radiation delivery QA part is divided into the
radiation iso-center accuracy QA part and dosimetric evaluation QA
parts.
Stereotactic quality control programs should include daily, weekly,
monthly and annual equipment QA procedures. This work proposes a
comprehensive Quality Control Protocol which was developed for the
Novalis-type SRS/SRT system.
References
Task Group 142 report: Quality assurance of medical accelerators, Med.
Phys. 36(9): 2009.
Timothy D. Solberg, James M. Balter, Stanley H. Benedict, Benedick A.
Fraass, Brian Kavanagh, Curtis Miyamoto, Todd Pawlicki, Louis Potters,
Yoshiya Yamada. Quality and Safety Considerations in Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy, Practical Radiation
Oncology: 2011
Dong-Joon Lee, Kyung-Nam Lee, Suk Lee, Sang Hoon Lee, Dae-Hong Kim.
Development of Novalis Quality Assurance Protocol for Radiosurgery, Med.
Phys. 21(1): 2010.
43
Conclusion: The applied method has proven to be useful for the analysis
and comparison of cardiac CT image quality. It can be applied for quality
control and optimization tasks.
References:
1. Wang Z, Bovik AC, Sheikh HR, Simoncelli EP. Image quality assessment:
from error visibility to structural similarity. IEEE Trans Image Process.
2004;13:4600e12.
2. Li C, Bovik AC. Content-partitioned structural similarity index for image
quality assessment. Signal Processing: Image Communication.
2010;25:517e26.
3. Chen GH, Yang CL, Xie SL. Gradientebased structural similarity for image
quality assessment. IEEE International Conference on Image Processing;
2006.
IMAGE QUALITY ASSESSMENT METHOD IN CARDIAC CT. FEASIBILITY OF
USE FOR QUALITY CONTROL AND OPTIMIZATION TASKS
D. Garcia-Pinto, A. Calzado. Departamento de Radiología, Universidad
Complutense de Madrid (UCM), Spain
Purpose: The aim of the work was to devise a method to assess image
quality of cardiac CT examinations in a phantom across various protocols
and simulated heart rates.
Materials and methods: Three different CT scanners were used in the
study: a 64-slice scanner (GE Healtcare LightSpeed VCT), a 320-slice
scanner (Toshiba Aquilion One), and a dual source CT (Siemens Somatom
Definition Flash). Coronary CT angiography examinations were performed using a Sim4D Cardio system to mimic 3D cardiac motion synchronized with the ECG signal and inserted into a thorax QRM phantom.
Two different heart rates were simulated (60 and 80 bpm) to study its
effect on image quality. Images of cylindrical inserts simulating arteries
of 1 or 2 mm diameter with nominal attenuation in the range 200e400
HU, were acquired, either with the insert at rest or in motion. Multiplanar reformatted images of the inserts were used for image quality
evaluation by assessing different parameters, such as contrast-to-noise
ratio (CNR) and normalized area under attenuation profiles (AHT). Two
similarity indexes, SSIM and G-SSIM [1,2,3], were also used to assess the
degradation of structural information. Values of the proposed quality
parameters were obtained by comparing insert images in motion and
at rest.
Results: CNR values were in the range 3.0e6.5 for 1mm diameter and
5.0e7.2 for 2 mm diameter; AHT relative ranges were, respectively,
0.14e0.45 and 0.35e0.87. Global SSIM values in the central plane were in
the range 0.4e0.7 for 1 mm diameter, and 0.6e0.9 for 2 mm and 0.3e0.7
for 1 mm and 0.5e0.9 for 2 mm in the case of the G-SSIM index. Details of
the behaviour of both indices for the 3 scanners are given in figs 1e3. The
highest values corresponded systematically to 400 HU stationary images
whereas the lowest were found mainly for 200 HU prospective acquisitions. Image quality is higher in the case of lower heart rates, as expected.
However, SSIM values were similar for 60 and 80 bpm at the 320-slice
scanner.
Fig.1. Mean values of the SSIM index for the two diameters used and different
nominal attenuation values. Images were obtained at the 320-slice scannerusing
two acquisition modes corresponding to 60 and 80 bpm heart rates.
Fig.2. Mean values of the SSIM index for the two diameters used and 400 HU
nominal attenuation. Images were obtained at the dual source CT scanner using
three acquisition modes and 60 bpm heart rate.
44
Abstracts / Physica Medica 30S1 (2014)
Conclusion: For all the radiography procedures the comparison between
the National Diagnostic Reference Levels provided by the GAEC and the
Local Diagnostic Reference Levels of Theageneio Cancer Hospital show that
the measured doses do not exceed the recommended levels.
For all the CT procedures, the measured dosimetric quantities were much
lower than the national recommended values.
To conclude, the hospital's procedures do not exceed the National Diagnostic Reference Levels in any case of diagnostic procedure thus the
Diagnostic Radiology department runs without malpractices.
Keywords: Diagnostic Reference Levels, Reference Values, Guidance
Levels, Quality Assurance
IMRT PROSTATE AND HEAD & NECK TREATMENT PLANNING AND
PRETREATMENT VERIFICATION. THE ARETAIEION UNIVERSITY
HOSPITAL EXPERIENCE
Fig.3. Mean values of the G-SSIM index for the two diameters used and two
different nominal attenuation values. Images were obtained at 64-slice scanner
using three acquisition modes and 60 bpm heart rate.
ESTABLISHMENT OF LOCAL DIAGNOSTIC REFERENCE LEVELS AT
“THEAGENEIO” CANCER HOSPITAL OF THESSALONIKI
S.G. Chanlaridis a, M. Chatzimarkou b, A. Makridou b, N. Servitzoglou b, E.
Soidou b, S. Stoulos a. a Aristotle University of Thessaloniki, Department of
Physics, Section of Nuclear & Elementary Particle Physics, GR-541 24,
Thessaloniki, Greece; b Theageneio Hospital for Cancer Treatment,
Department of Medical Physics, GR-546 39, Thessaloniki, Greece
Motivation: Estimation of doses received by patients undergoing radiological examinations for establishing local diagnostic reference levels
(LDRL) for routine procedures of diagnostic radiology department along
with minimization of patients' radiation exposure. The obtained results
were compared with the national values of DRL provided by the Greek
Atomic Energy Commission (GAEC) for the audit of malpractice in this
department.
Materials and methods: Numerous parameters were measured for a large
sample of patients undergoing radiography exams and CT scans. The mean
value of these parameters was selected for irradiation of patients and
measurement of the delivered dose.
A standard ionization chamber was selected to measure the suitable
dosimetric quantity.
For Radiography exams the dosimetric quantity that was measured was
the air-kerma at a distance of 1 meter from the source. The entrance skin
dose was calculated by multiplying the obtained air-kerma value with
suitable backscatter factors and correcting according to the inverse square
law for the standard patient’s dimensions.
For CT exams the dosimetric quantities that were measured were the
weighted Computerized Tomographic Dose Index (CTDIw) and the Dose
Length Product (DLP) for one acquisition and a complete examination.
Results: For the two operating radiographic units the doses in term of
entrance surface air-kerma are as follows:
Rad. UnitExam
CPI CPM 200DR
MERATE
BMI BRG 200R
MERATE
Chest Radiograph (PA)
Chest Radiograph (LAT)
Lumbar Spine Radiograph (PA)
Lumbar Spine Radiograph
(LAT)
0,297 mGy
1,28 mGy
Not enough data
Not enough data
0,284 mGy
1,259 mGy
4,06 mGy
6,938 mGy
For the CT unit:
Dosimetric quant.Exam
CTDIw
DLP
Cerebrum Seq.
Inner Ear
Visceral
51,05 mGy
29,756 mGy
24,018 mGy
40,84 mGy cm
5,95 mGy cm
7,205 mGy cm
Christos Antypas a, Christina Armpilia a, Ioannis Floros a, Zoi Liakouli b, Anna
Zygogianni b, Vassilios Kouloulias c, John Kouvaris b, Maria Lyra a. a 1st
Department of Radiology, Medical Physics Unit, Aretaieion Hospital,
University of Athens, Greece; b 1st Department of Radiology, Radiotherapy
Unit, Aretaieion Hospital, University of Athens, Greece; c 2nd Department of
Radiology, Radiotherapy Unit, Attikon Hospital, University of Athens, Greece
Background: The main principle of intensity modulated radiation therapy
(IMRT) is the combination of many segmental beams to produce a complex
dose distribution. The nature of IMRT delivery requires pre-treatment
quality assurance (QA) and plan verification. The Aretaieion University
Hospital is the first hospital of the public health sector in Greece that
implements IMRT in clinical practice. We present our preliminary experience on IMRT pre-treatment QA and plan verification.
Materials and methods: 10patients with prostate and head-and-neck
cancer treated with step-andeshoot IMRT in a 6MV Siemens Oncorlinac
are presented.
The IMRT plans were created on the Oncentra v4.3 (Nucletron, Elekta)
treatment planning system. The ICRU 83 and QUANTEC recommendations
for IMRT prescribing and constraining dose to organs at risks were followed. The Delta4 diode array phantom (Scandidos, Sweden) was used for
the plan verification. Measured dose was compensated for linac daily
output. Planned and measured dose were compared by using percentage
dose deviation, average distance to agreement (DTA) and gamma index
(3%/3mm). For all cases, a plan is considered to be successful if more than
90% of the tested diodes pass the gamma test.
Results: Objective sand dose constraints for the target volume and the
respective organs at risk were well satisfied for all cases. Regarding prostate cases, the average gamma index passing rate was measured higher
than 97%. Regarding the head-and-neck cases, the average gamma index
passing rate was measured higher than 90%.
Discussion: The ICRU 83 and QUANTEC recommendations for IMRT prescribing and constraining dose to organs at risks were followed and
satisfied for all studied cases. Our preliminary experience shows that pretreatment plan verification using the Delta4 phantom provides accurate
and reliable results of 3D dose distributions comparisons between the TPS
calculated and the deliverable plan. We expect to increase the IMRT patient workload in our hospital.
MAGNETIC RELAXATION MEASUREMENTS ON TISSUE MIMICKING
PHANTOMS: COMPARISON BETWEEN DIFFERENT FITTING ALGORITHMS
IN MRI T2 CALCULATIONS
G. Kalaitzakis a, L. Kavroulakis a, T. Boursianis a, S. Veneti a, L. Kontopodis b,
K. Marias b, E. Papadaki c, A. Karantanas c, T.G. Maris a. a Department of
Medical Physics, University of Crete, Heraklion, Crete, Greece; b Institute of
Computer Science, Foundation for Research and TechnologyeHellas (FORTH),
Heraklion, Crete, Greece; c Department of Radiology, University of Crete,
Heraklion, Crete, Greece
Purpose: The aim of this study is to compare five different regression
fitting algorithms for precise measurements of T2 relaxation times in tissue mimicking phantoms
Abstracts / Physica Medica 30S1 (2014)
Materials and methods: Twenty one (21) glass test tubes filled with
various materials, which simulate T2 values of different human organs/
lesions, embedded in a plastic holder served as a generic T2 relaxation
phantom. Test tubes were filled with materials which consisted of: (a)
standard EUROSPIN gel test objects, (b) Gd-DTPA hydatic solutions (c)
milk creams with various fat contents and (c) raw eggs with various
relative concentrations of egg-white and egg-yellow parts. The expected
range of T2 values in reference to all materials was from 20 up to 2000
ms. The generic T2 relaxation phantom was repeatedly scanned on a
clinical MRI system (1.5T) for over a 4 month period with a 2D single slice
Multi Echo Spin Echo (MESE) sequence with TR:6000 ms. Three different
sets of 32 symmetrically repeatable echoes were used as TE values: (setA: TE:(8-256)ms, set-B: TE:(20-640)ms and set-C: TE:(40-1280)ms. T2
relaxation parametric maps were calculated utilizing : (a) a Vendor
Specific (VS), (b) a Conventional Linear (CL), (c) a Weighted Linear (WL),
(d) a Non Linear (NL) and (e) a Multi Exponential Non Linear (MENL)
regression fitting model. T2 value precision figures (T2-ROI-CV) and long
term time (LTT-CV) reproducibility figures expressed by coefficient of
variation (CV %) measurements were obtained on each test tube with
each fitting model.
Results: T2 values of all EUROSPIN gel test tubes were in agreement
with their nominal values (accuracy<5%). T2 measurements performed
with the (WL), (NL) and (MENL) methods showed better precision
(mean T2-ROI-CV< 3%) and LTT-CV (5.2%) as compared to the (VS) and
(CL) methods. (MENL) methods were in agreement with the (NL) and
(WL) methods when a material with a single T2 value was measured.
EUROSPIN gel test objects and Gd-DTPA hydatic solutions were characterized by single T2 values. Milk creams and raw eggs were characterized by double T2 values. TE choices of Set-A and Set-B were
adequate for the calculation of the majority of T2 values present in
human organs/lesions.
Conclusion: (WL), (NL) and (MENL) regression fitting algorithms proved to
be an excellent means for precise measurements of T2 values on tissue
mimicking phantoms.
45
Fig 1. (Left) Experimental setup. The measurements were performed with small,
large and without BT filtration. (Right) The normalized air kerma profiles were
calculated by using the real (red lines) and Al-equivalent (blue points) BT filters.The air kerma attenuation by incrementally increasing the thickness of
aluminium was calculated until the ratio of the attenuated to the unattenuated air kerma rate profile was approximately equal to the corresponding measured ratio at each fan angle. These thicknesses of
aluminium represent the Al-equivalent BT filters.
A non-disclosure agreement with the GE Company enabled the use of the
exact information on the shape and components of the BT filters installed in
the CT scanner. A comparison of the calculated attenuated air kerma profiles
by using the real BT filter and the Al-equivalent BT filter validated the results
obtained in the present study. This work found a good agreement between
the attenuated profiles through the real and Al-equivalent BT filters, which
is presented in Fig. (1) (right) as a function of the fan angle.
References
[1] Adam C. Turner et al., Med. Phys., 36 (2009), pp. 2154e2164
[2] Kyle McMillan et al., Med. Phys. 40 (2013), 111907
[3] NORM ISO 4037-1 (1996)
[4] G. Poludniowski et al., Phys. Med. Bio., 54 (2009), N433eN438
QUALITY OF MEDICAL TECHNOLOGY FOR FLEXIBLE ENDOSCOPES AND
DISINFECTSORS
EXPERIMENTAL CHARACTERIZATION AND VALIDATION OF BOW-TIE
FILTERS IN A CT SCANNER
Babak Alikhani, Ludwig Büermann. Physikalisch-Technische Bundesanstalt
(PTB), D-38116 Braunschweig, Germany
M. Franken a, J. Ansems b, B. Damink c. a Medical Physicist, Franciscus
Hospital Roosendaal, The Netherlands; b Medical Physicist, Lievensberg
Hospital Bergen op Zoom, The Netherlands; c Medical Physicist, Franciscus
Hospital Roosendaal, The Netherlands
In recent years dosimetry in computed tomography (CT) based on Monte
Carlo (MC) simulation has significantly increased. A proper description of
scanner parameters is required for an accurate MC simulation. The characterization of bow-tie filters (BT) in the CT scanners is a necessary part of
MC simulations. Up to the present time, methods have been developed and
used in different works to characterize the BT filters of different scanners
[1,2]. The methods were based on a comparison of the calculated and
measured air kerma attenuation profile as a function of the fan angle.
Thereby, an aluminium-equivalent BT filter with an arbitrarily assumed
central ray thickness was determined. The goal of the present work was to
improve these methods by the absolute determination of the central ray
thickness of the BT filter. The scanner used in this work was a GE Optima
660 with two different BT filters. An almost energy-independent
responding ionization chamber (i-chamber) of the type Radcal 10x6-0.6CT
was used to measure the air kerma rate profile along the x-axis of the CT
gantry.
The air kerma response of the i-chamber was measured in narrow beam
radiation qualities [3] (20 kV to 300 kV) using PTB's primary air kerma
standard. A sketch of the experimental setup is shown in Fig. (1) left). In
order to measure the X-ray qualities of the CT scanner, the half-value layer
(HVL) method has been utilized. The measured first and second HVL in the
absence of the BT filters for the X-ray tube high voltage of 120 kV were (6.9
± 0.1) mm Al and (8.9 ± 0.1) mm Al, respectively. Using a program called
“SpekCalc” [4], a photon spectrum with approximately identical HVLs for
aluminium was calculated. The obtained spectrum is a good approach to
the initial spectrum of the X-ray tube with Al-equivalent inherent filtration. For the BT filter determination, first of all the ratio of the measured air
kerma rate profile with and without the BT filter at each fan angle was
calculated.
Background: In 2011 the “Professional Standard Handbook of Flexible
Endoscopes; Cleaning and Disinfection, version 2.1” was introduced. The
Dutch Healthcare Inspectorate regards this handbook as a field standard.
Dutch hospitals have been working on the implementation of a quality
system using this handbook. Here we describe our practical approach to
the introduction of this quality system.
Materials and methods: We started with a multidisciplinary group of
users, technicians and medical physics experts. Based on the life cycle of
medical equipment and the Plan-Do-Check-Act Cycle, two local quality
handbooks were introduced; the first focuses mainly on the users and the
cleaning and disinfection processes. The second handbook focuses on the
technical management of the medical equipment. These documents
include the tasks and responsibilities of the stakeholders, the outcomes of
the risk assessment, and describe the procedures for purchasing new
equipment. Futhermore they contain a validation scheme for the desinfection machines and defines the release of maintained medical equipment from the technician to the user.
Results: The acceptance test of repaired flexible endoscopes is improved
by using a mini-microscope, that can view into the inner canals of the
endoscope. In the Franciscus Hospital, the biomedical engineering technician performs the endocopic-disinfector validations. The medical physicist reviews the validation report. Canal tests are performed 4 times a year,
periodic validation is done at least once a year. These actions have resulted
in an average save of 15 kV per year.
Discussion: By setting up a multidisciplinary team and using the
plan-do-check-act cycle for this technology specific process, the quality
of the management of medical equipment is continuously improved.
We now have better technical support and more knowhow about
the flexible endoscopes and cleaning procedures. In 2014 version 3.0 of
46
Abstracts / Physica Medica 30S1 (2014)
the Standard Handbook of Flexibele Endoscopes will be launched in
English.
MEDICAL PHYSICS INTERNATIONAL JOURNAL e SERVING THE MEDICAL
PHYSICS PROFESSION WORLDWIDE
M. Stoeva a, S. Tabakov b, P. Sprawls c. a Medical Imaging Department,
Medical University e Plovdiv, Plovdiv, Bulgaria; b Department of Medical
Engineering and Physics, King's College London, London, UK; c Emory
University School of Medicine, Atlanta, GA, USA
Background: Medical Physics International (MPI) is the official journal of
the International Organization of Medical Physics (IOMP) and fully representing medical physicists all over the world targeting to increase the
visibility of our profession by publishing articles that contribute to medical
physics education, professional development, activities, heritage and
newest technologies.
Materials and methods: MPI has been established in 2013 as an open
platform for medical physicists to share their knowledge and experience.
Papers published in MPI reach over 20,000 medical physicists in more
than 80 countries around the world. With this large network of readership the journal is one of the most popular and reputable journals in our
profession.
Results: During its existence MPI attracted many readers and established
itself as a valuable reference and resource for the medical physics profession. The Topics covered by the MPI Journal are: The History and Heritage of Medical Physics, IOMP Professional and Educational Activities,
Developments within.
Medical Physics Organizations, Educational Resources, Contributions on
Practical and Applied Medical Physics; Innovations in Technology and
Clinical Methods, Reviews of Signicant Developments, Tutorials, PhD
Dissertation and Thesis Abstracts, and Abstracts of Presentations at
Conferences.
Discussion: MPI is dedicated to provide every medical physicist а platform
to use either as an author or as a reader and contribute to the advancement
of medical physics. Medical Physics International Journal is a valuable and
important source of scientific and professional information for all IOMP
members.
IS THE USE OF SHIELD PAD AN EFFECTIVE TECHNIQUE FOR LOWERING
INTERVENTIONIST RADIATION DOSE?
Ahmed M. Outif, Aida Labriguito. Department of Medical Physics; King
Fahad Medical City; Riyadh; Kingdom of Saudi Arabia
Background: Several manufactures have recently introduced shield pads
to lower interventions radiation doses. This pad is placed outside the
scanning field and is claimed to protect the staff from scattered radiation.
This kind of shield has been used in KFMC. However, no clear study has
been conducted to quantify the effectiveness of such shield pad.
Aim: The aim of this study was to assess the effectiveness of shield pad on
interventionist radiation doses.
Method: Rando phantom was used in this study and was placed on the
scanning table to mimic patient position. Radiation shield pad was placed
at different places on the phantom mimicking the usual clinical placement
of the pad during different cathlab procedures. The x-ray tube was kept
under the chest. The dose at different operator levels (waist, collar, eye, and
knee) was assessed with and without the use of radiation shield pad.
Results: The effect of using shield pad on staff dose was found to be
function of operator position, levels, and x-ray field size.
1) For direct procedure on the heart, the pad reduces operator waist
dose by 89%, the collar by 75%, eye by 53%, and the knee by 0%.
2) For Femoral insertion: the pad reduces operator waist dose by 57%,
the collar by 2%, the eye by 5%, and the knee by 0%.s
3) For Central vein insertion: the pad reduces operator waist dose by
58%, the collar by 48%, eye by 34%, and the knee by 0%.
The use of large field size (20X30) was found to prohibit pad waist level
dose reduction effect dramatically during direct hear (closer to primary
beam), however the dose reduction effect of pad remain valid for collar,
and eye levels. As the operator moved away from the primary beam the
effect of pad on dose reduction remains valid with different field sizes.
Conclusion: The use of shield pad was found to be an effective method of
lowering interventionists radiation dose at most levels, however this effect
may be reduced when large x-ray fields are used. No effect of pad was
found on operator lower limb dose.
COMPARISON OF FLUORESCENT 99MTC-AU-BSA AND CONVENTIONAL
99MTC-BSA SPECT/CT DISTRIBUTION IN VIVO
M. Stalnionis a, b, R. Rotomskis a, b. aLaboratory of Biomedical Physics,
Institute of Oncology, Vilnius University, LT-08406, Vilnius, Lithuania;
b
Laser Research Center, Vilnius University, LT-10223 Vilnius, Lithuania
Combining optical imaging with other imaging modalities has brought
scientific attention, and it could lead to important advances in diagnostics
[1]. Radiolabelled human serum albumin (HSA) products that have been
used clinically for scintigraphical detection can be modified for advanced
optical detection [2]. Bovine serum albumin (BSA) can also be used as a
platform for forming targeted tracers [3]. Moreover, BSA embedded fluorescent gold nanoparticles (Au-BSA) can be one of promising optical imaging tracers [4]. The aim of this study was to investigate a SPECT/
Fluorescence agent 99mTc-Au-BSA for imaging and compare its’ in vivo
characteristics with the conventional 99mTc-BSA.
Au-BSA nanoparticles were radiolabeled by mixing Au-BSA with sodium
pertechnetate (Na99mTcO4). Labeling efficiency and stability studies were
performed by means of thin-layer chromatography (TLC). Biodistribution
imaging of the 99mTc-Au-BSA and 99mTc-Au-BSA tracers in a small animal
model was performed using clinical SPECT/CT gamma camera and compared.
The distribution studies of 99mTc-Au-BSA in vivo revealed that the
behavior of dual-labeled tracer is similar to the behavior of 99mTc labeled
BSA and similar to 99mTc labeled HSA. Shortly after the injection 99mTcAu-BSA and 99mTc-BSA were seen as a bloodpool tracers as is 99mTc-HSA.
The uptake from the blood circulation into the organs of clearance started
rather quickly after the injection. Within the first minute of the study the
most of the 99mTc-Au-BSA and 99mTc-BSA was detected in the lung, liver,
and kidneys as it was presented for 99mTc-HSA [5]. It should be noted that
as high uptake of 99mTc-Au-BSA in the urinary system as of 99mTc-BSA
represents the good excretion of 99mTc-Au-BSA to the bladder, thus,
favorable as a tracer for the diagnostics.
From our results it could be concluded, that gold nanoparticle
formed inside the albumin does not affect the behavior of albumin itself
in vivo. The behavior of 99mTc-Au-BSA is ruled by the BSA. The results of
the distribution in vivo would suggest that 99mTc-Au-BSA kinetic
pathways are through the liver and urinary tract as it was with the
99mTc-BSA.
References:
[1] Azhdarinia A, Ghosh P, Ghosh S, Wilganowski N, Sevick-Muraca EM.
Dual-labeling strategies for nuclear and fluorescence molecular imaging: a review and analysis. Mol Imaging Biol. 2012;14:261e76.
[2] Brouwer OR, Buckle T, Vermeeren L, Klop WM, Balm AJ, van der Poel
HG, et al. Comparing the hybrid fluorescent-radioactive tracer indocyanine green-99mTc-Nanocolloid with 99mTc-Nanocolloid for sentinel
node identification: a validation study using lymphoscintigraphy and
SPECT/CT. J Nucl Med. 2012;53: 1034e40.
[3] Bunschoten A, Buckle T, Kuil J, Luker GD, Luker KE, Nieweg OE, et al.
Targeted non-covalent self-assembled nanoparticles based on human
serum albumin. Biomaterials. 2012; 33:867e75.
[4] Xie J, Zheng Y, Ying JY. Protein-directed synthesis of highly
fluorescent gold nanoclusters. J Am Chem Soc. 2009;131:888e9.
[5] Wang YF, Chuang MH, Chiu JS, Cham TM, Chung MI. On-site preparation of pechnetium-99m labeled human serum albumin for clinical
application. Tohoku J Exp Med. 2007;4:379e85.
Abstracts / Physica Medica 30S1 (2014)
EFFECT OF GAMMA RADIATION ON THE FERRITIN ACTIVITY
V. Kochev a, L. VladimirovaeMihaleva a, At. Papucharov b, G. Gyulchev c, G.
Zlatevac c, N. Atanasova e Gesheva b. a Sofia University “St. Kliment
Ohridski”, Faculty of Physics, 5 James Boucher Blvd. 1164 Sofia, Bulgaria;
b
Specialized hospital for active treatment in oncology, 6 Plovdivsko Pole
Str., Sofia, Bulgaria; c Sofia University “St. Kliment Ohridski”, Faculty of
Medicine, 1407 Sofia, 1 Kozyak Str., Sofia, Bulgaria
Presenting authors: At. Papucharov, G. Gyulchev
Topics: Radiation protection, monitoring and dose reduction
47
The consequences of ferritin exposure to different doses of gamma radiation, typically used in therapy, are disclosed in this paper. Although, the
ferritin is susceptible to UV and visible light, responding with a change in
the redox state of its mineral core, the effect of high energy gamma photons turned out to be more subtle. However, at increased doses there is a
facilitated mobilization of inorganic core Fe3 +, which is reduced to Fe2+ and
released from the protein interior in the presence of ascorbic acid as
exogenous reducing agent. According to a working hypothesis, this is
attributed to the impact of the products of water radiolysis on the architecture of the threefold channels responsible for the transport of iron.
Keywords: ferritin, gamma radiation therapy, potentiometric redox titration, radiolysis of water