Radiation Protection (minimising dose in imaging
examinations) in Children
1. Children have higher radiation sensitivity than adults and a longer life
span in which to develop radiation-induced cancer; also as future
parents they are at risk for passing on radiation-induced genetic
defects (1). If the examination on the child involves the use of ionising
radiation, you must ensure justification for the procedure and that the
alternative use of Ultrasound or Magnetic Resonance Imaging (MRI)
has been carefully considered and discounted.
2. Never forget that children are not just small adults:
a. The proportions of a child’s body differ considerably from those
of an adult’s body. If a child’s chest or abdomen is X-rayed its
body shape means that larger areas of the body may lie within
the radiation field (or directly adjacent to it) and are therefore
affected by scattered radiation (1).
b. Infants also have large proportions of haematopoietic (blood
forming) bone marrow in all parts of the body including the
extremities(1).
3. Limit the exposure(s) to what is absolutely necessary for a diagnosis,
So always
a. Use an agreed standard type and number of projections for
specific indications for conventional imaging
b. Follow specific, agreed paediatric protocols for CT imaging,
fluoroscopy and interventional
c. However, in cases of NAI-better that more and good quality
images are taken than to miss a diagnosis of NAI whence more
harm may come to the child
4. Patient positioning:
a. Measure the body part
b. Avoid the use of grids for body parts less than 10-12 cm thick
c. Note that a grid suitable for a child (with a minimum thoracic
thickness from front to back of 15 cm) with a ratio of 8/36 gives a
dose twice as high as when no grid is used
d. You may need to use a grid for some teenagers when a large
body build might be such as to increase scatter (2)
e. Place the child in as close contact with the cassette as is
feasible
5. Exposure time considerations (3):
a. Uncooperative children will need immobilization preferably
provided by specialized devices
b. Remember children have faster heart and respiratory rates
c. Balance the use of a small focal spot size (0.6-1.3mm) with a
short exposure time (short exposure times improve quality
without increasing dose, but only if using powerful generators
and accurate exposure time switches)
6. Other exposure parameters
a. Use of a long (or the recommended) Focus-to-Film distance
b. Use increased KVp (reduced mAs) for greater penetration and
less absorption
c. AECs may be inappropriate for small children although would be
useful when set up correctly for axial skeleton and abdomen
when lead protection is outside primary beam.
7. Collimation (3):
a. All images must be as well collimated as possible-as this
reduces primary and scattered radiation
b. Body parts outside the region of interest should not be in the Xray field
c. Beam-limiting devices automatically adjusting the field size to
the size of the cassette are generally inappropriate for children;
collimation should be to area of interest only.
d. Evidence of collimation should be apparent by clear edges of
unexposed film.
8. Depending on which part of the body is involved you must protect
gonads/eyes/thyroid where appropriate.
a. Shielding devices should be appropriately positioned to be
efficient for protecting the tissues for which they are placed and
to avoid unnecessary repeat examinations(2)
b. Whenever the gonads lie within or close to (nearer than 5 cm)
the primary beam they must be protected without impairing
necessary diagnostic information (2).
c. Consider the use of PA projections to protect eyes in skull
examinations
d. Consider the use of AP projections in young children for
thoracic images as there is more haemopoetic bone marrow (in
the vertebrae, ribs and shoulder) located in the dorsal part of the
body (1).
e. Consider the use of PA projections in older girls for thoracic
spine examinations in order to protect developing breast tissue.
9. In CT studies, the use of age- and indication-adapted protocols can
lower radiation exposure by as much as 95%. Use ‘child size’
guidelines based on individual size / weight parameters(4) Follow the
advice of the Image Gently campaigners who have produced a number
of educational materials in the form of a number of power point
presentations (5). If appropriate also see ‘How to Develop CT
Protocols for Children’ (6).
10. In summary: There are many ways to lower the exposure of children
and adolescents to ionizing radiation without sacrificing diagnostic
reliability. The main factors in lowering exposure are:
a. proper attention to clinical indications,
b. perform only necessary CT examinations,
c. the use of special X-ray protocols,
d. the use of alternative imaging studies without ionizing radiation
wherever possible,
e. the expertise of the radiographer
Don’t forget, the highest quality images (i.e., those that require the
most radiation) are not always required to make diagnoses.
References & Bibliography
(1) Alzen G, Benz-Bohm G: Radiation protection in pediatric radiology.
Dtsch Arztebl Int 2011; 108(24): 407–14. D10.3238/arztebl.2011.0407
(2) IAEA Radiation Protection of Patients –special group children. Visit:
https://rpop.iaea.org/RPOP/RPoP/Content/SpecialGroups/2_Children/
(3) IAEA Radiation Protection in Paediatric Radiology. L03 Radiation
protection in screen-film radiography
https://rpop.iaea.org/RPOP/RPoP/Content/Documents/TrainingPaediat
ricRadiology/Lectures/PAEDIATRIC-L03-radiation-protection-ofchildren-in-screen-film-radiography.ppt
(4) Radiation risks and paediatric CT: a guide for health care providers at:
http://www.cancer.gov/cancertopics/causes/radiation/radiation-riskspediatric-CT
(5) Image gently at:
http://pedrad.org/associations/5364/ig/index.cfm?page=825
(6) How to Develop CT Protocols for Children
http://spr.affiniscape.com/associations/5364/files/Protocols.pdf
(7) DoH 2010 Delivering quality imaging services for children. Visit:
http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/Publicati
onsPolicyAndGuidance/DH_114980