Aspects of the volume effect in the linear-quadratic and cubic model.

The volume dependence of the linear quadratic survival function SLQ = exp (-(alpha D + beta D2)) and the cubic survival function Scub = exp (-(alpha D + beta D2 + delta D3)), which represent different stages of a useful approximation of the general dose-response relationship S = exp (-alpha 1D-alpha 2D2-alpha 3D3-......-alpha nDn (terms of higher order)), has been regarded with respect to the tolerance doses of skin, spinal cord and brain, and the corresponding isoeffects have been compared with the results of a modified Ellis-formula Dt = (NSD)Vo T0.11 N0.24 (V/Vo)-0.158. In a second part, some theoretical models on the volume effect and the empirical power relation of the field size have been investigated by a formulation of the multi target theory by the aid of correlation functions.