PEDIATRIC RADIOGRAPHY

 

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The Role of The Radiographer in Dose Reduction for Paediatrics

Cynthia Cowling ACR, B.Sc. M.EdDirector of Education ISRRTDevelopment Leader, Radiation Sciences Central Queensland University, Australia

 

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Outline

• Traditional role and techniques• Role in CT Dose Reduction• Implications for Interventional• Dose implications in the move from

Analog to digital• Some specialized activities

The pediatric patient always presents with unique problems for the radiographer

• Keeping still

• Use of restraining devices

• Response to verbal direction

• Use of shielding

• Role of the family

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Use immobilization devices judiciously

Capture the attention of the child

Other Devices

• Tape (be careful not to hurt skin)• Sheets, towels• Sandbags• Radiolucient sponges• Compression bands• Stockinettes• Ace bandages

Radiation Protection

• ALARA

• Proper immobilization

• Short exposure time

• Limited views

• Close collimation

• Lead aprons and half shields

Differences children and adults• 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

 

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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

• 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

Dose Optimization in CT• kVp – decrease kVp, decrease dose,

increase image noise, non-linear

– Ex. 140 kVp 80 kVp dose by 78% (Siegel M et al, 2004)

• 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 protocol1. IV injection of contrast2. 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 in-house equipment

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

 

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Other Areas attempting dose reduction

Scoliosis series

EOS

1- Takes two simultaneous digital planar radiographs in the standing position with very low dose : 2D

•

22DD

33DD

EOS

sterEOS 2- Creates a three dimensional bone envelope weight bearing image : 3D

Collimated X Ray beamCollimated detector

linear detecto

r

scanning

No vertical divergence of X rays No scatter detect SNR increased Allows for lower dose ++

No vertical divergence of X rays No scatter detect SNR increased Allows for lower dose ++

Linear scanning of a fan-shaped collimated X ray beamfrom 5 cm to 180 cm (whole body)

Linear scanning of a fan-shaped collimated X ray beamfrom 5 cm to 180 cm (whole body)

Scanning process

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Dose & Image quality

– 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

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.

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

EOSEOS

• Dose reduction x9……With improved or equivalent image quality (97%)

• High dynamic of image (16 bits, > 30 0000 Levels of Gray).

• Digital images, DICOM format• Single exposure for multiple exams• Pixel size 254µm

Low dose & High Image Quality

Non Non EOSEOS/Dose /Dose x10x10

Fuji

EOS

EOS requires less dose (Montreal study on spine)

100%

11%

EOS lowers dose by over 89%

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!

Why Low Dose?

 

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Analog to Digital, Dose implications• Requires changes to radiographer’s knowledge base• Radiographers ｗ ork 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 Gentlywww.imagegently.org

 

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ＴＷＯ KEY POINTS

TEAMWORK

TEAMWORK TRAINING

 

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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