ABSTRACT
For efficient applications of protons in radiotherapy, detailed knowledge of the corresponding radiobiological mechanism is necessary. The inactivation cross section is a useful tool to explore the interaction mechanism. Hence, the inactivation cross section for proton irradiation on V79 cells has been calculated using published survival data. The linear quadratic equation was used to fit the survival curves and the parameter alpha was used to calculate the cross section. The cross section segma is plotted as a function of the mean free path lambda and the linear energy transfer LET. The cross section segma-versus- lambda curve shows a saturation region between lambda >/= 2 nm and lambda