Radiation Survival Models, SLD, PLD, and Dose Rate

Abstract

Post-irradiation cell survival as a function of radiation dose can be biophysically modeled in several different ways, using Poisson statistics as the basis for survival equations. The single-hit, multitarget model has parameters D₀, the dose correlating with one hit per cell, and D_q, which is the width of the “shoulder,” and correlates with repair capacity. The linear-quadratic (LQ) model utilizes terms α (single-hit kill) and β (two-hit kill) which correlate with low-dose killing and high-dose killing, respectively. The LQ model can be used to determine biologically equivalent doses between various dose fractionation schemes. The various survival curve parameters can be altered if irradiated cells undergo either sublethal damage repair (which is modeled with split dose experiments), potentially lethal damage repair (which is modeled with plating delay experiments), or if cells are irradiated at low or ultrahigh dose rates. In addition to these two commonly used models, there are multiple other models that have their own strengths and weaknesses.