Relations between cell survival models having different inactivation mechanisms

Two different types of cell survival models are considered. In each model it is assumed that both irreversible and reversible lesions (or prelesions) can be formed by the radiation products from one energy-loss event. In the first model further energy-loss events can produce radiation products that can convert the reversible lesions to irreversible ones. The presence of even one irreversible lesion in the cell leads to reproductive death. In the second model reversible lesions can react by way of second-order kinetics to become irreversible and, as in the first model, the presence of one or more irreversible lesions leads to reproductive death. If the parameters in either model are chosen to have magnitudes that are required in the fitting of cell-survival data, approximate analytical survival probabilities can be found, and these are equivalent to the corresponding prediction of the Roesch model. At all stages approximations are made that are appropriate to low LET radiation. (U.S.)