Microdosimetric calculations by simulating monoenergetic electrons in voxel models of human normal individual cells

Abstract This work proposes two kinds of voxel model of human normal individual cells, and the Monte Carlo software GATE is used to describe and analyze the effects of some factors on the microdosimetric quantity--specific energy, such as shape, volume and physical models for interaction. In this paper, “Livermore” and “Penelope”, two of low energy electromagnetic models in the Monte Carlo code Geant4 and adopted in GATE, are used to estimate the specific energies and their distribution of a lung epithelial cell (BEAS-2B), a renal epithelial cell (293T) and their size-like simple ellipsoids (hereinafter referred to as “simple geometry”) respectively. According to the irradiation conditions in radiobiology, four irradiation geometries, the source isotropically irradiated within the cell, the source irradiated axially outside the cell (x-axis positive and z-axis negative) and the cell surface covered with a polypropylene film for external irradiation for monoenergetic electrons beams from 50 keV to 1 MeV are simulated. The results show that the influence of the physical models on the specific energy of the voxel phantom is 27.35% smaller than that of the simple ellipsoid. The BEAS-2B cell shows large differences between phantom and simple geometry in both cytoplasm and nucleus under the condition of external irradiation. For the 293T cell, even if the shape of the cell is relatively regular, there is a deviation between two kinds of geometry under certain conditions, the maximum is 17.78%, while the minimum is 1.19%. These statistical results indicate that shape, volume and position can have a certain impact on the specific energy, and demonstrate that in terms of exploring the mechanism of radiation biological effects, human real cell voxel phantoms may be more practical and valuable than traditional simple models from the aspect of physical modeling. It can be expected that the microdosimetric assessment based on the real cell voxel model and the establishment of relevant databases will play a unique role in predicting the dose of target cell volumes accurately under given conditions in the radiation protection and clinical radiotherapy.