Track structure analysis of strand break induction and cell survival

The induction single- and double-strand breaks by heavy particles and the killing of cells with exponential survival curves were analysed by using the approach suggested by Butts and Katz. It was found that the theoretical treatment was adequate for single-strand break formation, but failed for double-strand breaks and the cellular endpoints. This was attributed to one co-operative action of electrons within the track of an ion. A quantitative treatment is possible by using proximity functions which may be derived from current beam models. Further analysis shows that for double-strand break formation the interaction distances are of the order of a few nanometres. (author)