Niveles de Referencia de Diagnóstico en Radiología Pediátrica

Graciano Paulo
Coimbra Health School
Portugal
The impact of optimization on Diagnostic Reference Levels in Pediatrics
graciano@estescoimbra.pt
Graciano Paulo
ESTESC-Coimbra Health School, Portugal
Head of the WHO collaborative Centre for Radiation Protection
Chair of the Scientific Board of Medical Imaging & Radiotherapy
Department
www.estescoimbra.pt

Graciano Paulo
Portugal
Disclosure
There are no conflicts of interest and nothing to disclose
I have no financial interest/arrangement or affiliation with
any organizations related to commercial products or services
to be discussed this program.

Graciano Paulo
Portugal
Introduction
• The risk of exposure to radiation is a permanent topic on the agenda of
international organisations like the ICRP, UNSCEAR, the IAEA and the
WHO (1).
• Stochastic risks are of special concern in paediatric imaging, since
children are more vulnerable than adults and have a longer life-span to
develop long-term radiation-induced health effects like cancer (2).
• DRL’s are a legal obligation and can be considered a tool to optimise
dose exposure to the patients and the population (3).
www.icrp.org, www.unscear.org, www.iaea.org, www.who.int(1)
(2)
EC 2013/59/EURATOM(3)

Graciano Paulo
Portugal
ABOUT PLAIN RADIOGRAPHY
(Lança,2013)(3)
• Technology development, although
having a high potential for dose
reduction in fact contributed for a dose
increase, due to incorrect use.
• Plain radiography is one of the first examination procedure for diagnostic purposes (1);
(1) Medine LS, et all Evidence-Based Imaging in Pediatrics: Optimizing
Imaging in Pediatrics. Springer. 2010
(2) http://www.imagegently.org
(3) Lança, L et al, Digital Imaging Systems Systems for Plain Radiography.
Springer, 2013

Graciano Paulo
Portugal
PAEDIATRIC CHALLENGES
• Age
• Height
• Weight
• Difficulty on defining a standard patient.
• Lack of consensus regarding the best methodology to group paediatric patients in
order to define a DRL :
 specific ages (0, 5, 10 and 15 years);
 division between new-borns and infants;
 age groups (<1, 1-<5, 5-<10, 10-<16, ≥16);
 To present DRLs as a function of patient projection thickness.

Graciano Paulo
Portugal
PAEDIATRIC CHALLENGES
9 935 patients
Chest
Abdomen
Pelvis

Graciano Paulo
Portugal
Chest X-ray: DR systems
Why?

Graciano Paulo
Portugal
19
16.41
8.29
3.8
0
2
4
6
8
10
12
14
16
18
20
Este Estudo
DR
Fase 1
CR
Fase 2
CR
Fase 3
CR
Exposuretime
(ms)
EU
Guidelines
reference
line
(10ms)
(1) Paulo, G.; Santos, J.; Moreira.; Figueiredo, F. (2011) Radiation protection Dosimetry
(1) (1) (1)

Graciano Paulo
Portugal
Results
Exposure parameters of chest AP/PA :
Tube voltage values used by
each radiographer for chest
radiography 5-<10 y
kV mAs ExT (ms)
mean
(min, max)
mean
(min, max)
mean
(min, max)
68 5.8 11.9
(50-73) (4-13) (6-19)
78 1.8 2.9
(66-96) (1-8) (1-12)
74 2.4 25.0
(59-80) (1-5) (5-232)
70 5.6 11.8
(57-77) (4-6) (6-17)
79 2.7 4.3
(66-90) (1-16) (1-24)
75 3.0 28.1
(55-110) (0.5-8) (2-100)
hosp. A
hosp. B
hosp. C
hosp. A
5-<10 hosp. B
hosp. C
Hosp.Age group
1-<5

Graciano Paulo
Portugal
To achieve this goal, good practice in radiographic technique is needed and therefore
special attention must given, simultaneously, to several aspects of the procedure, such
as:
a) patient positioning and immobilisation;
b) accurate field size and correct X-ray beam limitation;
c) the use of protective shielding, when appropriate;
d) optimisation of radiographic exposure factors.
ABOUT OPTIMISATION

Graciano Paulo
Portugal
ABOUT BEAM COLLIMATION
• Using a correct beam limitation is crucial to avoid unnecessary radiation dose
outside the area of interest, and prejudice the image contrast and resolution by
increasing the scattered radiation.
• Therefore proper collimation of the examined structure is necessary and preferred
over the use of post-processing tools in CR or DR systems, such as imaging crop.
• This post-processing tool can potentially hide an increase in patient dose due to an
unnecessarily overexposed area (ICRP, 2013; Moore et al., 2012).
A B BA

Graciano Paulo
Portugal
The “hidden” problem of
Digital Radiology:
“cropping”
Hermann T. L. et al (2012): recommends that
the best practice in DR is collimating the X-
ray beam to the appropriate anatomical
area.
Bomer J. et al (2013): electronic collimation
hides an overexposure. The patient/area
exposure is normally underestimated.
9%
Own data, 2016

Graciano Paulo
Portugal
ABOUT TECHINICAL FEATURES
Choosing the most adequate exposure factors and making the best effective use of the
technological features available in the X-ray equipment, is crucial for obtaining the best
diagnostic quality image with the lowest possible dose
• The kV should be used at the highest value, within the optimal range, considering the position
and anatomical structure being examined, allowing the lowest quantity of mAs needed to
provide an adequate exposure to the image receptor (Herrmann et al., 2012)
• For chest, abdomen and pelvis exposure, the principle of using a higher kV values should be
followed, since it would result in lower patient attenuation, and therefore lower dose for the
same detector exposure
• The kV should also be increased in each ascending age/size group due to the increases in
tissue thickness, which requires more photon penetration (Knight, 2014)
• The use of additional filtration, which removes the lower energies from the X-ray spectrum
and consequently raises the average beam energy for a constant kV. By removing the low
energies from the spectrum, the ESAK to the patient is reduced (Brosi et al, 2011)

Graciano Paulo
Portugal
The reality of daily practice (chest radiography example)
4 x
ESAK
3 x
KAP
The exposure conditions were the
same for both exposures (same
patient);
KAP and ESAK values were 3 and 4
times lower respectively in chest
radiography B
Reason: A was made with AEC and
central chamber; B was made with
AEC and lateral right chamber
A
B

Graciano Paulo
Portugal
National DRLs by age group: KAP and ESAK values for chest AP/PA
Results

Graciano Paulo
Portugal
General recommendations
• Measure anatomical structure to be exposed;
• Don’t use anti-scatter grid for structures with thickness below 12cm;
• Use lead protection devices;
• Collimate X-ray beam the maximum possible, according to the clinical
indication of the exam;
• Check the exposure parameters according to obtain the best diagnostic image
quality, according to clinical indication
> 12cm
< 12cm

Graciano Paulo
Portugal
To use or not to use gonad shielding?
Do not use lead shielding when performing a pelvis X-ray in female
patients;
Use lead shielding in male patients only if it stays out of the collimation
field.

Graciano Paulo
Portugal
Optimization Model
Phantom
CIRSTM ATOM
model 705
Phantom
Kyoto kagakuTM
model PBU-60
• Highest tube voltage value (Herrmann et al., 2012)
• Increased in each ascending age/size group (Knight, 2014).
• Use antiscatter grid above 10-12cm thickness (www.imagegently.org)
• Use of additional filtration to reduce ESAK (Brosi, 2011).
Exposure parameter manipulation:
Data Collection:
Exposure parameters
Dose values

Graciano Paulo
Portugal
Chest
n=20
Abdomen
n=16 - 85%
- 55%
Abdomen
n=22
- 63%
Pelvis
n=12
- 74%
Chest
n=21
- 83%
Currently used protocol
Proposed protocol
No significant
differences
image noise

Graciano Paulo
Portugal
Age
groups
(years)
Median
weight
(Kg)
Tube
tension
(kV)
Chamber Grid
Additional
filtration
<1 7 70 central no 0.1mm Cu
1-<5 14 80 central no 0.1mm Cu
5-<10 26 90
Lateral right
(right lung)
yes 0.2mm Cu
10-<16 46 100
Lateral right
(right lung)
yes 0.2mm Cu
16-≤18 58 110
Lateral right
(right lung)
yes 0.2mm Cu
Chest
Age
groups
(years)
Median
weight
(Kg)
Tube
tension
(kV)
Chamber Grid Additional filtration
5-<10 26 75 central yes 0.2mm Cu
10-<16 46 80 All yes 0.2mm Cu
16-≤18 58 90 All yes 0.2mm Cu
Abdomen
Age
groups
(years)
Median
weight
(Kg)
Tube
tension
(kV)
Chamber Grid Additional filtration gonads protection
16-≤18 58 90 central yes 0.2mm Cu
only in males if
protection is out of
exposure field
Pelvis

Graciano Paulo
Portugal
4 paediatric
Radiologists
ViewDEXsoftware

Graciano Paulo
Portugal
VGC Results

Graciano Paulo
Portugal
0
20
40
60
80
<1 1-<5 5-<10 10-<16 16-≤18
Age
13 22
35
68 73
9 10 14
41
57
KAP(mGy.cm2)
- 41%
0
500
1000
1500
<1 1-<5 5-<10 10-<16 16-≤18
Age
34 72 250
1267
020 47 76 170 237
KAP(mGy.cm2)
- 58%
0
500
1000
<1 1-<5 5-<10 10-<16 16-≤18
Age
19 30 84
267
876
14 28 51 55 93
KAP(mGy.cm2)
- 48%
Results

Graciano Paulo
Portugal
By age groups
KAP
(mGy.cm2
)
ESAK (mGy)
<1 9 34
1-<5 10 40
5-<10 14 52
10-<16 41 60
16-≤18 57 62
age groups
(years)
P75
KAP
(mGy.cm2
)
ESAK (mGy)
<5 9 26
5-<15 10 35
15-<30 15 46
30-<50 32 58
≥50 57 67
weight
groups (kg)
P75
By weight groups
Note: grouping by weight categories is
the recent recommendation from ICRP
& PiDRL
Post optimisation DRLs
13
19
60
134
94
145
181
209
234
88

Graciano Paulo
Portugal

Graciano Paulo
Portugal
TAKE HOME MESSAGES
• Evidence shows that the impact of the optimisation process has a clear reduction of patient
dose without affecting the image quality.
• Optimisation programmes should be carried out on a regular basis, especially when new X-ray
equipment or post-processing tools are installed.
• The use of electronic cropping in plain imaging results in unnecessary radiation exposure to
the patient. To surpass this problem there is a need to raise awareness amongst
radiographers and to identify new anatomical landmarks for collimation.
• The post optimisation exposure conditions should provide a better “diagnostic” image quality
with a significant dose reduction.
• There should be a continuing programme of assessment to track any changes in equipment
performance.
• Links between the radiographer, the medical physicist and the radiologist, to provide a
greater opportunity for optimisation are essential.

Graciano Paulo
Portugal
Graciano Paulo
ESTESC-Coimbra Health School, Portugal
Head of the WHO collaborative Centre for Radiation Protection
Chair of the Scientific Board of Medical Imaging & Radiotherapy
Department
www.estescoimbra.pt
Obrigado

Niveles de Referencia de Diagnóstico en Radiología Pediátrica

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