An Equation for Predicting the Surviving Fraction of Cells Irradiated with Single Pulses Delivered at Ultra-High Dose Rates

Abstract

An equation has been derived that predicts surviving fraction when cells which have been equilibrated with oxygen are exposed to high intensity single pulses of radiation. The equation allows for the quantitative examination of various features of pulse irradiated survival curves. It is found that the spacing between anoxic segments of the survival curves is not a linear function of initial oxygen concentration. A function is added to the equation thereby permitting a fit of the derived equation to experimentally determined survival curves where a shoulder is involved. Fitting the equation to experimental data provides a means for determining the dose required to deplete oxygen in the cells and for determining the constant K in the equation that relates radiosensitivity to oxygen concentration. As a result of the derivation, an experiment at conventional dose rates is suggested.