construct am organ dose-organ respoase curve-~a graded series of cell doses, which in principle permits us to develop a function for the (fractional) number of hit cells that will respond guantally, at each value of cell dose. This function provides the conditional probabilities if hic, and if a dose of a given magnitude respond quantally. is received, a piven cell will Thus this function is the cell analugue of the “organ dose-organ response” curve. cellular end points (3). Such curves have been derived for several We thus have three probabilities to be evaluated, 1) that, with a given amount of exposure, a cell will be hit, 2) that quantally. ,, che given exposure, of it is these probabilities the fraction of that permit the estimation, those exposed cells tor a that will respond quantally. vel of of interest An example will help to clarify the above statements, In Fig. 2 are shown schematically three distributions of cell doses from stochastic one rn LLE at cells hic if - che dose to the cell will be of a given size, and 3) that the cell will respond the cell e maximum ne that, the che short arded @ Nu/Ne quring a will also 4 wills with Area =Ny/Ne FRY of at on total hit, for exposure E ~! Cell dase, z the at is © Fig. 2nersy yn 2 of cell Schematic distributions of cell doses for three levels 2 to a radiation of a given quality or mixture. The smaller distributions in the lower right reglon result from multiplying the larger distributions by the HSEF shown. cell exact vy / Note that only the areas under the distribution and not the shape increase with exposure. of ed 2 of exposure CO ~209- s0129ut