PEDIATRIC RADIOGRAPHY - ISRRT

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Nov 15, 2013 (3 years and 10 months ago)

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PEDIATRIC
RADIOGRAPHY




2

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




3

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

5

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




9

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




10

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





11

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




12

Interventional Procedures


Increased because of immediate risk
benefit for child (not undergoing surgery)


However, not much consideration given
to long term stochastic effects




13

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 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
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






18

Other Areas attempting dose
reduction



Scoliosis series

EOS



1
-

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




2
D

3
D

EOS

ster
EOS

2
-

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


Collimated X Ray beam

Collimated detector

linear
detector

scanning


No vertical divergence of X rays


No
scatter

detect


SNR
increased


Allows

for
lower

dose ++

Linear

scanning of a fan
-
shaped

collimated

X ray
beam

from

5 cm to 180 cm (
whole

body)

Scanning
process

21

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

EOS




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
EOS
/Dose x10



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?




24

Analog to Digital, Dose
implications


Requires changes to radiographer’s knowledge base


Radiographers

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




25

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




26

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




27

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




28

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




29

Enhancing Radiation
Protection in Computed
Tomography for
Children

Module two


Image Gently

www.imagegently.org




30

TWO

KEY

POINTS

T
E
A
M
W
O
R
K

TEAM
WORK

TRAINING




31

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
R
adiographers and
R
adiological
Technologists (ISRRT)


Maria del Rosario Perez, WHO