The History and perspective on quality factors proposed by the International Commission on Radiological Protection (ICRP)

佐藤 達彦   

Sato, Tatsuhiko

Proper consideration of the relative biological effectiveness (RBE) is essential for evaluating health risks from cosmic radiation exposure, which spans a wide range of linear energy transfer (LET). The quality factor as a function of LET, , proposed and refined by the International Commission on Radiological Protection (ICRP), remains central to these assessments despite the primary use of radiation weighting factors in terrestrial protection frameworks. This article reviews the historical development of the function and examines the adequacy of its application to cancer risk estimation. To this end, we first confirm its numerical consistency with a more sophisticated quality factor proposed by NASA through a comprehensive literature review. We then evaluate the appropriateness of the maximum value of , using a meta-analysis of RBE data for mouse tumor induction by fission neutrons. Finally, we discuss future perspectives on , emphasizing its strong relevance to measurements not only in space dosimetry but also in medical physics.