Doses and risks in common medical examinations—impact of age and sex

The 2007 Recommendations of ICRP set out a system of radiological protection that is scientifically based, prudent in its assumptions, and practicable in its application. The system is designed to be straightforward in its use around the world, enabling the control of doses and risks arising from differing exposure situations, but it is not directed at specific individual circumstances. Effective dose is a fundamental concept in the ICRP system. It is a measure of dose that relates to risks of stochastic health effects in the context of a globally averaged population but is often applied, without sufficient thought, to particular exposures experienced by particular individuals. However, using the methodology used to derive risk coefficients for the ICRP 2007 Recommendations, an effective dose can be associated with a risk estimate that results from appropriate adjustments for sex, age-at-exposure, and (broadly speaking) population group. This process is illustrated by considering the risks associated with effective doses for a range of medical diagnostic procedures. In comparison with the aggregated detriment to health set out in the 2007 Recommendations for a population of all ages, enhancement factors of 2-3 are appropriate for exposure of a young boy and of 3-4 for a young girl. The aggregated detriment applies without enhancement to men aged in their mid-20s and women in their mid-30s but steadily reduces for increasing age-at-exposure, reaching a factor of 0.5 for men in their early-50s and women in their early-60s, and so on. It is debatable whether anything beyond such broad-brush adjustments of stochastic risk per effective dose is required for routine protection purposes, but this remains a central question for ICRP as the evolution of the system is considered. It is a question that will be explored by ICRP Task Group 128.