Report of a consultation on justification of patient exposures in medical imaging.

Radiation protection in medicine is underpinned by the concepts of justification and optimisation. Over the last 20 y much successful work has been devoted to developing and consolidating approaches to optimisation. A substantial knowledge base and a set of practical approaches have now been created to give effect to it. With respect to justification, less effort has been applied and the efforts applied have not yet been as successful. Authoritative sources suggest that a substantial fraction of radiological examinations may be unnecessary. In addition, a mainstream general medical journal has identified that few of those responsible for prescribing or performing examinations were familiar with the units used to specify the amount of radiation (and risk) received. This report sets out the conclusions of a consultation held in Vienna, by the International Atomic Energy Agency, dealing with the nature of justification and how to give effect to it in practice.