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Medical exposure in radiology:
Scope and responsibilities
Module VIII.1 - Part 1 : General principles
Introduction
• We will introduce briefly in this lecture
•
the main modalities using ionizing
radiation in a Medical Imaging
Department
And who are the “actors” using these
imaging modalities ?
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Topics
1. What IS radiology ? And the different
modalities.
2. The team of professionals
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Overview
• In this presentation we will present the
•
scope of medical imaging, the
terminology used, the variety of
modalities (from plain radiography to CT),
and the complementarity with other
imaging techniques
The medical physicist as expert plays an
important roel in radiation protection
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Topic 1: what is radiology?
An Introduction to Radiology: purpose,
sub-modalities and basic terminology
Topic 1: content
• What is radiology and who performs it
• Some basic terminology and equipment
• Different modalities overview
• Plain radiography
• Fluoroscopy
• Angiography
• Digital subtraction angiography (DSA)
• Computed tomography (CT)
• Complementarity of methods:
• CT and MRI
• Isotopes: Nuclear Medicine
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What IS Radiology ?
(from EUR16260)
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Radiology is…
• Study of images of the human body
• Start: use of X Rays and photographic
•
film
Additional: use of X Rays in therapy
• Now: separate specialty and department
• Today variety of tools for imaging
• Creating images computer assisted: CT
• Some using no ionizing radiation: US, MRI
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“Radiology” in this course series…
• Restricted to the use of X Rays (Ionizing
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•
•
•
•
radiation)
Plain radiography: static
Fluoroscopy: dynamic
Angiography: use of contrast material
Computed tomography
Specific applications:
• Mammography: breast cancer detection
• Pediatric radiology: from newborn to grown-up
• Aid to other specialties: Interventional radiology
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Plain radiography
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Plain Radiography
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Obtained by exposing patient to X Rays
Image is basically a shadow of parts of patient
absorbing or blocking X Rays
Image is collected on
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•
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Photosensitive film
A digital imaging plate
A fluoroscopic system
with cassette holder
Image is a “photographic negative”
•
Darker regions have less absorbed X Rays
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Plain radiography: example of equipment
Movable patient
“couch”
Tube housing
And diaphragm
High voltage
generator
Film cassette
holder
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Fluoroscopy
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Fluoroscopy
One image of a “life”
sequence
Colon
White areas:
Barium,
contrast medium
Black areas: air
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Fluoroscopy
• X Ray transmitted trough patient
• Out-beam strikes fluorescent screen
• Part of an Image Intensifier system
• Coupled to a television camera
• Radiologist can watch the images “live” on TV-
•
monitor; images can be recorded
Fluoroscopy often used to observe digestive
tract
• Upper GI series, Barium Swallow
• Lower GI series Barium Enema
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The Image Intensifier:
basic element of the fluoroscopy equipment
Output
window
Input
fluorescent
screen
In vacuum electronic amplification system
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Fluoroscopy room equipment
I I and TV camera under
patient’s table
Typical Fluoroscopy equipment, with “over-coach” tube,
viewed from above (Philips)
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C-arm equipment
• Ability to maneuver
•
c-arm around patient
without moving him
Often used as
“mobile” unit
• Critical care units
• In room examination
• Modern units allow
fluo + radiography
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Mobile unit
Parking
conditions
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Angiography
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Angiography images
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What is angiography
• Invasive procedure
• Injection into patient of radio-opaque
substance (“Dye” or “Contrast Agent”)
• Injection by small tube into vein or artery
• The radio-opaque material
• Blocks X Rays
• Gives shadow of injected vessels
• Reveals shape of artery/vein
• Diagnosis of obstruction, narrowing
(Stenosis)
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Digital Subtraction Angiography or DSA
Digital: allows subtraction, image manipulation
Two images with different calculation algorithms
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What is DSA?
• Subtraction: removes non-essential
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•
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structures in the image
Combining mathematically pre- and postcontrast images
Noisier, but improves visibility of
important structures
DSA was first full digital based
fluoroscopic imaging procedure: high
spatial resolution not necessary
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Computed Tomography
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Computed Tomography
• CT- Scan:
• Computer tomography
or
• CAT-scan:
• Computer axial
tomography
• Gives sectional, in
•
depth or 3-D
information
CT supersedes
“linear tomography”
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What is CT ?
• Spinning X Ray source and detectors around
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patient
Attenuation data collected from multiple angles
Computer processes these data
A reconstructed image is presented on screen
These images: “cuts”, “slices”, “sections”
Newer generation: helical/spiral scan, 3-D data
Problem of overlap of shadows is solved
CT can be performed “plain” or after injection
of “contrast agent”
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Complementarity with other modalities
Magnetic Resonance Imaging
(MR or MRI)
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Magnetic Resonance Imaging
Two images obtained with (different) MRI techniques, compared to CT-slice
(DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR)
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Magnetic Resonance Imaging
• No use of X Rays or other type of Ion. Radiation
• Magnetic field “lines-up” protons
• Coils with high frequency pulse knocks the out
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•
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of alignment
Radiofrequency antennas “listen” to the
emitted resonance signals
Resonance signals are treated by computer,
creates 3-d information
“Cuts” or “slices” presented similar to CT, but
information collected different/complementary
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Historical pictures
Original EMI CT head scanner
an 80 x 80-matrix head CT
image obtained with it (1973)
An X Ray examination
room (Mayo Clinic circa
1925)
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Historical Pictures: radiology and… risks
Radiograph of the hand
of Mrs. Roentgen
1903: first radiation risk reports
[From R F Mould, A Century of X-Rays…]
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Summary of Topic 1
• Radiology serve the diagnosis of patients
• Uses different modalities, mainly
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•
•
involving ionizing radiation: X Rays
Plain radiography gives static projection
image
Fluoroscopy gives dynamic images
Contrast agents improve visibility, used
e.g. in angiography
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Summary of Topic 1
(cont.)
• Digital systems allow subtraction of
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•
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images, enhancing visibility (DSA)
CT techniques allow 3-d reconstruction
Nuclear medicine and MRI images are
complementary to X Ray images
From early beginnings radiology included
radiation risks
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Topic 2: the professionals
The team…
• Medical practitioner: the Radiologist
• M.D. with training interpretation of medical images
• Interprets the images to establish diagnosis
• Radiographer (radiological technologist)
•
Staff member trained in positioning patient and
optimal use of equipment for image quality and
radiation protection
• Radiodiagnostic Physicist as qualified expert
• Dose optimization
• Optimizing of imaging protocols
• Link with “outside” of department
• The referring M. D.
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BSS Requirement
As per BSS II.2, registrants and
licensees should ensure that for
diagnostic uses of radiation, the
imaging and quality assurance
requirements of the Standards be
fulfilled with the advise of a qualified
expert in radiodiagnostic physics
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Clinical responsibility
• Responsibility regarding individual medical
exposures attributed to a practitioner
• This includes:
• justification;
• optimization;
• clinical evaluation of the outcome;
• cooperation with other specialists and the staff, as
appropriate
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Clinical responsibility
(2)
• Practical aspects:
• obtaining information of previous
examinations;
• providing existing radiological information
and/or records to other practitioners and/or
prescribers;
• giving information on the risk of ionizing
radiation to patients and other individuals
involved
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The Roles, Responsibilities and Status of
the Radiodiagnostic Physicist
•
•
Two categories
One category : of physicists working as teachers and
scientists in universities, as researchers in industrial
laboratories, in governmental research institutions
The second category: physicists working in a clinical
environment, in the hospital
•
Names: "medical physicist", "clinical physicist", "hospital
physicist“ are used in different countries
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Radiodiagnostic Physicist: definition
• Has or might have an influence on the
diagnosis and/or treatment and safety of
patients, or their decisions might have
consequences for the performance of
diagnostic, treatment and safety
procedures in hospital care.
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Radiodiagnostic physicist: responsibilities
• The main responsibility of the
Radiodiagnostic physicist is to provide a
high standard of service in the hospital.… He is
a member of a team of personnel responsible
for diagnosis and treatment of patients. The
physicist wil have an influence on the
diagnosis, treatment and safety procedures for
the patient and thus his decisions will have
consequences for the patient. As his decisions
are based on his competence, a competence
not found elsewhere he should be fully
responsible for his work
[ from EFOMP]
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More Responsibilities of the
Radiodiagnostic Physicist
• High standard of service
• Standardisation and calibration of medical
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physical equipment
Safety of physical methods used in routine
clinical applications (with medical staff)
Research and in the development
Providing education and training in applied
physics for doctors, nurses, medical technical
assistants
Recognised by the national health authorities
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Ionizing radiation: Radiodiagnostic
Physicist as the qualified expert
• Man-made contribution to the radiation
•
•
exposure of human beings primarily due
to the use of Ionizing Radiation and
radioactive substances in medicine.
Radiodiagnostic Physicist will act as the
“Qualified Expert in Radiation physics”
Responsible for radiation protection of
the patient and the staff in radiological
department
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The Role of the Qualified Expert in
Radiodiagnostic Physics
• Dosimetry of the equipment beams
• Lay down and supervise the Quality Assurance
•
programme
Surveillance with respect to radioprotection
• Public, staff, …
• Reduce dose to patients, keeping in mind the
•
•
required image quality
Choose equipment for radiation protection
Give advice on purchase of diagnostic
equipment with respect to image quality and
radiation protection
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What we learned
• To become familiar with the multiple
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•
imaging modalities in a radiological
department
Each modality requires specific
equipment
In radiation protection (patient or staff)
the medical physicist as a qualified
expert plays a central role
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Where to get more information?
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The Physics of Diagnostic Imaging, David J. Dowsett, Patrick A.
Kenny and R. Eugene Johnston, Chapman & Hall Medical, ISBN 0412-40170-1
International Basic Safety Standards for Protection Against
Ionizing Radiation and for the Safety of Radiation Sources. 115,
Safety Standards. IAEA, February 1996.
ICRP 73. Radiological Protection and Safety in Medicine. Annals of
the ICRP, 26(2), 1996.
Qualified Expert in Radiophysics,The European Federation of
Organisations for Medical Physics, Policy Statement 3
Role and Responsibilities of Medical Physicists in Radiological
Protection of Patients, Azam Niroomand-Rad, Ph D; See: IOMP
Website
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