Radiobiological Modeling Based On Track Structure

Since the interaction of beams of charged particles with targets in physics is customarily based on beam fluence and interaction cross section we have chosen the same logical structure for our radiobiological model. Proceeding from simple to complex systems we have first constructed and verified a track structure model of observable tracks in nuclear emulsions, then of dry enzymes and viruses, of scintillation counters, of TLD’s, of the Fricke dosimeter as prerequisite to the construction of a valid radiobiological model. For this model we require 1) knowledge of the average radial distribution of local dose about the path of an ion, 2) the size of the target volume, and 3) the response of the detector to gamma rays, measured as a function of dose. Requirements 2 and 3 determine detector parameters: the radius of the target volume ao, the characteristic does E0 at which there is an average of 1 hit per target and C, the hittedness in the sense of the cumulative Poisson distribution, used to approximate the dose-response function after gamma irradiation. Physical detectors are usually 1 hit, though many hit response has been observed for TLD’s, for photoresists and etchable track detectors, and for desensitized nuclear emulsions. Our requirements are in principle experimentally determinable. Thus, for the Fricke dosimeter E0 is determinable from the yield as a function of dose while a0 is from yield a function of Fe++ concentration. Here size is replaced by an effective diffusion length. Hittedness is determinable by comparison of the shape of the dose response curve after gamma irradiation with that of the cumulative Poisson distribution, where the shape can be measured