Download pediatric radiography

PEDIATRIC
RADIOGRAPHY
The Role of The
Radiographer in Dose
Reduction for
Paediatrics
Cynthia Cowling ACR, B.Sc. M.Ed
Director of Education ISRRT
Development Leader, Radiation Sciences
Central Queensland University, Australia
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Outline
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Traditional role and techniques
Role in CT Dose Reduction
Implications for Interventional
Dose implications in the move from
Analog to digital
• Some specialized activities
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The pediatric patient always presents with
unique problems for the radiographer
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Keeping still
Use of restraining devices
Response to verbal direction
Use of shielding
Role of the family
Use immobilization devices
judiciously
Capture the attention
of the child
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Other Devices
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Tape (be careful not to hurt skin)
Sheets, towels
Sandbags
Radiolucient sponges
Compression bands
Stockinettes
Ace bandages
Radiation Protection
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ALARA
Proper immobilization
Short exposure time
Limited views
Close collimation
Lead aprons and half shields
Differences children and
adults
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Mental development
Chest and abdomen the same circumference in NB
Pelvis - mostly cartilage
Abdominal organs higher in infants than older children
Hard to find ASIS or Iliac Crest in young child, can
center 1 inch above umbilicus (bellybutton)
• Exposure made as baby takes a breath to let out a cry
Dose reduction in CT Use
Radiologists and radiographers must create
an essential partnership
It is the Radiographer who UNDERSTANDS
and OPERATES the equipment
All CT sites should
cooperate;
start reduction and
validate results
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Essential features
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Dose should be age and weight specific
Dose should be customized to pathology
Number of follow ups should be scrutinized
Software features should be used if possible
– Image enhancement
– Modulation of mAs
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Working with the radiologist,
the radiographer…
• Starts with standard protocol and then
reduces to provide acceptable image
• Screens all requests, re protocol and
suitability of request
• Attempts to narrow down area of interest
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Interventional Procedures
• Increased because of immediate risk
benefit for child (not undergoing surgery)
• However, not much consideration given
to long term stochastic effects
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Collaboration makes a
huge difference
• Example from Hospital for Sick Children,
Toronto Canada
• In Angio CT the TEAM was able to
reduce dose from 3 mSev to 0.8 mSev
as standard for typical Angio CT exam
for child
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Dose Optimization in CT
• kVp – decrease kVp, decrease dose,
increase image noise, non-linear
– Ex. 140 kVp
80 kVp
(Siegel M et al, 2004)
dose by 78%
• mAs – decrease mAs, decrease dose,
increase noise, linear
– Ie. Halve mAs, Halve dose
• Pitch, length of scan, gantry cycle time
Cardiac Angiography CT
Protocol
• Weight-based protocol
1. IV injection of contrast
2. Set parameters:
• Tube Voltage: 80 kVp
• Gantry Rotation Time 0.4 s
• Pitch 0.9
3. Variable parameters: Vary mAs According to body weight
• - <5 kg: 70 mAs [Newborn phantom]
• - 5-25 kg: 80 mAs [1-, 5-year old phantom]
• - 25-50 kg: 90 mAs [10-year old phantom]
• - >50 kg: 100 mAs
4. Scan Coverage
• Only area of interest
Conclusions
• New protocol/equipment exposes patients
to less radiation than previous set-up
• Doses are less than 1 mSv across all
phantoms ~75% decrease from previous
protocol
• Images are of diagnostic quality
• Project is a good illustration of the utility we
have at Sick Kids -> Easily determine
radiation risk from various procedures with
Moving Forward
• This study was a general view of the
exam
• Study Clinical assessments to:
– Collect data on what scans are used to
diagnosis for
– Percentage diagnosis yield
– Percentage of cases that would have
benefitted from lower/higher dose
– Can we tighten dose optimization further
Other Areas attempting dose
reduction
Scoliosis series
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EOS
1- Takes two simultaneous digital
EOS
planar radiographs in the standing
position with very low dose : 2D
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2- Creates a three dimensional
sterEOS
bone envelope weight bearing
image : 3D
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Scanning process
Collimated detector
Collimated X Ray beam
linear
detector
Linear scanning of a fan-shaped collimated X ray beam
from 5 cm to 180 cm (whole body)
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No vertical divergence of X rays
No scatter detect
SNR increased
Allows for lower dose ++
scanning
Dose & Image quality
Current practice :
- Scattered radiation accounts for more than 80% of the X-ray flux passing through the patient
- This noise reduces detectability and therefore a higher dose is required to maintain image quality
Clinical impact of dose :
M. Doody et. Al., « Breast Cancer Mortality After Diagnostic Radiography », Spine, Vol. 25, No 16, pp 2052-2063
Retrospective study on mortality due to breast cancer (women followed for scoliosis
using spine X-Rays) :
–5466 women followed between 1912 and 1965. Average of 25 radiographs (~0.11 Gy)
=> Risk of death due to breast cancer is 69% higher than what is encountered in general
population.
– In a linear scanner such as EOS, the detector geometry prevents more than
99.9% of the scattered radiation from entering the detector
– EOS allows for a dose reduction up to 10 times compared to CR
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Low dose & High Image Quality
EOS requires less dose (Montreal study on spine)
EOS
11%
Fuji
100%
EOS lowers dose by over 89%
• Dose reduction x9…
…With improved or equivalent
image quality (97%)
• High dynamic of image
(16 bits, > 30 0000 Levels of
Gray).
EOS
Non EOS/Dose x10
• Digital images, DICOM format
• Single exposure for multiple
exams
• Pixel size 254µm
Why Low Dose?
Slot Scanning Technology
– No scatter detected, Noise suppressed
 Allows for Lower Dose
Charpak Nobel Prize Winning Detector
– Detector amplification : Photon gaz
cascade,
 High gain signal, sensitivity maximized
Automatic internal gain adjustment
– Dynamic range outperform other digital
imaging technology (30,000 gray levels)
– Available for any patient!
Analog to Digital, Dose
implications
• Requires changes to radiographer’s knowledge base
• Radiographers ｗork practice must change to ensure
high quality images
• Must be more aware of dose since automation and
image acquisition does not provide feedback in image
production especially key effects of mAs and kVp
• Radiographer must work as part of Team to ensure
adherence to ALARA
• QC always critical
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Cont..
• Positioning can be more critical, aligning to detectors
• Manual techniques may be required to produce
optimum quality
• Post processing as a method of enhancing image
should be discouraged
• Exposure creep must be avoided (any more than 4%
unacceptable)
ADVANTAGE provides statistical evidence of exposure
factors and dose
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How the profession can
improve dose reduction
• Increase awareness through membership in
initiatives such as Image Gently
• Provide retraining opportunities
• Make use of publications such as ICRP
• Participate in Clinical Audits
• Actively work collaboratively with radiologists
and physicians
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For Example
• In Ontario, Canada, Radiographers are
regulated by the College of Medical
Radiation Technologists of Ontario
(CMRTO) and
• Healing Arts Radiation Protection Act
(HARP) which controls and identifies
who can order and operate x ray
equipment
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Recommendations
• HARP should require that prescribing or
requesting a CT be permitted only by
individuals who have appropriate clinical
knowledge and training in radiation
protection
• All persons operating CT equipment or
devices take a radiation safety course
documented by a certificate of credentials
– 200% increase in CTs in Ontario between 1996-2006
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Enhancing Radiation
Protection in Computed
Tomography for
Children
Module two
Image Gently
www.imagegently.org
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ＴＷＯ KEY POINTS
TEAM
WORK
TRAINING
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M
W
O
R
K
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Many Thanks and
Acknowledgements to
• Image Gently- Alliance for Radiation Safety in Pediatric
Imaging
• American Society of Radiologic Technologists-ASRT
• Ellen Charkot, Director Imaging Services Hospital for Sick
Children, Toronto Canada
• Lori Boyd, Director of Policy College of Medical Radiation
Technologists of Ontario, Canada (CMRTO)
• Marie De La Simone, biospace med, Paris France
• International Society of Radiographers and Radiological
Technologists (ISRRT)
• Maria del Rosario Perez, WHO
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