Assessment of effective dose in paediatric CT examinations.

Current concerns focus on the high doses encountered in computed tomography (CT) examinations as they are extending towards younger and more radiosensitive patients. Previous work produced conversion coefficients for effective dose (E) from dose-length product (DLP) for four anatomical body regions applicable to any patient size. This work aims to update the earlier work, incorporating the new ICRP 2007 tissue-weighting factors and testing the methodology on modern scanners. For each age and body region, E was determined relative to DLP. Measurements were carried out on a 64-slice scanner to test this methodology. The conversion coefficients show exponential decrease with patient size. Conversion factors for the pelvis region are lower than before (30-40 %), those for the chest increased (by up to 25 %) whereas those for the head and abdomen remained fairly similar. Application of the coefficients to modern scanners verified the results, so that this methodology can be applied for a wide range of paediatric CT examinations.