RANDOMIZED MULTIHIT MODELS AND THEIR IDENTIFICATION

The multihit-one target model induces a stochastic ordering of cell su rvival with respect to the cell sensitivity characteristics. This prop erty can be used for a description of cell killing effects in heteroge neous populations of cells on the basis of randomized versions of the model. In such versions, either the critical number of lesions or the mean number of hits per unit dose (sensitivity), or both, are assumed to be random. We give some new results specifying conditions under whi ch the randomized multihit models are identifiable, with a focus on th e following cases: (1) the critical number of radiation-induced lesion s, m, is random; (2) the sensitivity parameter, I, is random given In is known or otherwise; (3) x and m form a pair of independent random v ariables.