Prospects of applying microdosimetry in radiobiology

A study of the biological effects of radiation cannot do without biophysical models of the mechanism of damage to living structures. These models must be microdosimetric, i.e., must respect the random character of the interaction of radiation at cellular and sub-cellular levels. The model is discussed of the biological effects of radiation with regard to the inactivation of cells based on the hit theory which culminates in the theory of dual radiation action. The question is discussed of which sensitive structure is damaged by ionizing radiation. The hitherto used models do not quantify biological repair;only models based on the biological modification of primary damage attempt to describe the repair of double-strand breaks of DNA. The contribution is emphasized of microdosimetry which, with the help of models of biological radiation effects, may contribute to establish better values of the quality factor of radiation. (J.P.)