The case for individualisation of radiological protection in medicine

Medical applications make the largest contribution to radiation exposure of the population from artificial sources. Measurable dose quantities do not reflect harm, so effective dose (E) is used to describe doses to patients. Dose management software can evaluate organ doses from computed tomography (CT) scans and calculate E for reference phantoms, but the use of E for individual patients is not appropriate, as risks of stochastic effects vary with age and sex. There is a desire to have a better indicator of radiation risks to individuals in line with moves towards personalised medicine. This paper considers variations in the relation between E and risk resulting from the use of standard phantoms and differences in age and sex. Anatomical phantoms can be matched to individual patients allowing more realistic estimates of organ doses, and these could eventually be derived directly from CT scan images. The best assessments of organ doses could then be combined with age- and sex-specific coefficients to calculate risks. Since software is being developed through which such individualised doses are achievable, it would be timely for ICRP to provide guidance on the development and application of an individualised dose quantity within the overall system of radiological protection, at least for medical patients.