Radiobiological challenges posed by microdosimetry.

Abstract

The inapplicability of the concept of dose to cellular and subcellular structures is the paradox that has driven the development of radiation biophysics. It remains a central problem which necessitates the use of microdosimetry in radiobiology, radiation protection, and the clinical applications of ionizing radiation. The trend towards microdosimetric measurements in radiation protection practice is contrasted to the recent adoption of radiation protection quantities by ICRP that are not related to microdosimetric parameters, and it is argued that uncertainties in the numerical magnitude of radiation risks must not motivate ambiguity of definitions. In radiobiology there has been a variety of uses of microdosimetric data but an insufficient assessment of their differences and similarities, often compounded by widely different terminology. The use of microdosimetry in radiobiology is, at present, limited by the detail and the reproducibility of biological information, not by lack of microdosimetric data. New techniques of molecular biology are now beginning to permit analyses of the spatial distribution of DNA lesions that can be correlated to the spatial fluctuations of energy deposition by different ionizing radiations.