Calculation of the inactivation cross section of V79 cells by protons in radiotherapy

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 DNA segment [almost equal to 4 microm[2]]. Such a saturation is also seen in the segma-LET curve. This implies that one DNA segment is at a risk upon the traversal of a single proton