Effective dose evaluation of multidetector CT examinations: influence of the ICRP recommendation in 2007

Abstract

We compared effective doses for recent computed tomography (CT) examinations calculated based on International Commission on Radiological Protection publication number 103 (ICRP 103) with those calculated based on ICRP publication number 60 (ICRP 60), and considered the usefulness of the effective dose in CT dose evaluation. After placing radiophotoluminescence glass dosimeters (RPLDs) inside or outside an anthropomorphic phantom, we examined from the chest to the pelvis, cardiac, and cranial regions of the phantom. The absorbed dose was calculated by multiplying calibrated dose values of RPLD by the mass energy coefficient ratio. The effective dose was calculated as the sum total of the value for each tissue, which was multiplied by the equivalent dose according to the tissue weighting factor recommended in ICRP 103 and ICRP 60. Calculated effective doses based on ICRP 103 were different by –11% to +82% compared with those based on ICRP 60. The values of absorbed doses for selective tissues were relatively higher than the values for the effective dose. The effective dose represents only a mean dose value for an average human. Therefore, assessing the absolute dose of particular individuals in CT examinations based exclusively on the effective dose is not recommended.