On the probability of interaction between elementary radiation-induced chromosomal injuries

Within the Theory of Dual Radiation Action, the heuristically useful function, γ(κ{script}), that two energy depositions, a distance κ{script} apart, will result in observable damage can be written in terms of two more fundamental quantities: One, s(κ{script}), describes the structure of the sensitive matrix of the cell. The other, g(κ{script}), describes the probability that two elementary injuries, a distance κ{script} apart, will combine to produce observable damage. A priori, the known enhancement exhibited by y(κ{script}) at nanometer separations could be due to an enhancement of s(κ{script}), g(κ{script}) or both. For the endpoint of chromatid exchanges in Chinese hamster cells, γ(κ{script}) has been evaluated from experimental data and s(κ{script}) from a model system. From these g(κ{script}) has been estimated and is roughly constant below ∼ 1 μm, decreasing rapidly at larger separations. Thus the enhanced short-range effect appears to be a function more of the spatial characteristics of the target rather than the probability of damage interaction. © 1988 Springer-Verlag.