The use of cell-oriented factors and the hit size effectiveness function in radiation protection

It has long been argued that ionizing radiation can be considered to interact with matter in discrete, randomly occurring energy transferring events ("hits") and that the resulting microscopically nonuniform pattern of energy deposition strongly influences the biological effect of a given exposure. Microdosimetric measurements combined with cellular biological response data in the form of a "hit size effectiveness function" (HSEF) suggest a possible cell-oriented alternative method of correlating exposure with effect at low levels of any radiation or mixture of radiations. The instrumentation required, the validity of the approach, and its practical usefulness in radiation protection are examined, and its application to space radiation exposure is proposed as a test case.