Radiobiological model for calculating the probability of death of mammalian cells exposed to ionizing radiation with different linear energy transfer

One of the fundamental problems of radiobiology is to predict a quantitative relationship between the onset of a specified radiation-induced effect on a biological object and the dose of exposure to ionizing radiation under different conditions (for ionizing radiation of different quality and different time of exposure). The purpose of this article is to solve a particular part of the general problem: the development of a mathematical model for the probability of death of mammalian cells depending on the radiation dose with arbitrarily specified linear energy transfer (LET), with a single irradiation of these cells in vitro. To solve this problem, microdosimetric approaches based on the theory of the dual action of radiation were used. When developing the model, the following assumptions were used: 1) there are sensitive volumes (SVs) in the cell, damage to the volumes can lead to cell death; 2) the probability of cell death depends on the number of damaged SVs; 3) the probability of damage to the SVs depends on the energy absorbed in it; 4) to calculate the energy absorbed in the SVs, a simple model for the interaction of ionizing particles with matter was used: the particles move in a straight line, the LET of the particles coincide with the linear energy absorbed in the matter. The developed mathematical model for estimating relationship of the probability of cell death on the dose explicitly contains LET. Thus, the use of the proposed model makes possible separation of biological parameters responsible for the onset of radiation-induced effect from radiation characteristics of the irradiation conditions., Classical radiobiological data, underlying the IAEA ionizing radiation recommendations for determining the relative biological effectiveness (RBE) of different types present an argument for the model validation. Experimental data on irradiation of human kidney T1 cells present an example. The article demonstrates that the developed model makes it possible to calculate the probability of cell death depending on the dose of ionizing radiation with an arbitrarily set LET for photons, electrons, and -particles with a LET from 0.4 to 200 keV/ µm. It follows from the proposed model that a linear-quadratic dependence can occur not only in DNA damage, but also in other biologically important molecules. The use of this model can be extended to predict other radiation-induced effects, as well as the probability of occurrence of radiation-induced effects under various time exposure regimes.