Criteria and techniques for analysing cell survival data

Cell survival was studied by analyzing the inactivation probability density function and its fundamental parameters. Mean , varianceσ2 and modeDmode were evaluated and a set of equations relating these parameters to the usual parameters of the multitarget, multihit and linear-quadratic modelsDo andn, α andβ, k andλ are reported. The multihit equation used was an extension of the usual equation, to allow parameterk to assume values that are not necessarily integers. In the multitarget curve, the mode of inactivation probability density function, proved to be the quasi-threshold doseDq =Do ln(n). Relative variance, degree of asymmetry and degree of peakedness can be calculated from the shape parametersn in the multitarget model,k in the multihit model, and in the linear-quadratic model. From an analysis of eight published cell survival sets of data, on C3H10T1/2 cells exposed to low LET radiations, it was found that ,σ, andSF2 are the parameters which exhibit the least variation from experiment to experiment and the least variation in selecting the range of data available for estimation.