Monte Carlo Simulation For Biological Dose In Tumor And Normal Tissue Of Patients

The next breakthrough of radiation therapy will be the combination of radiation physics and radiation biology.The future precise radiotherapy will consider more individual biological characteristics,provide individualized radiation dose according to different patient biological features and accurately estimate radiobiological outcome.Based on Monte Carlo simulation we calculated the photon and scattering secondary electron energy spectrum and dose distribution in every irradiated tumor and normal tissue voxel,constructed an estimating model of radiobiological effects in this paper.And we also calculated the cells survival rate of radiation under different single dose based on the radiation biological effect model.The radiobiological effects estimation model based on Monte Carlo simulation can be divided into two parts: Monte Carlo physical process simulation and the cell damage yield and damage repair calculation.At first,apply Monte Carlo simulation and calculate the dose distribution in the patient and the energy spectrum of scattering secondary electrons and photons which enter the surface of all voxels for the first time.Then,use photon and scattering electron energy spectrum to calculate the secondary electrons kinetic energy entering cells surface and the dose deposited in the voxel.In the radiological effects section,use the MCDS model to calculate the DNA damage yield(cDSB,sDSB)of all cells in the interested voxel first.And then use the TLK model to calculate the DNA damage after repaired and survival rate of the cell in the voxel.Based on the radiological effect prediction model,we found that the survival rate of the cell was 54.22% after a treatment dose of 2.0Gy and analyzed the difference of cell survival rate under different single doses.It turned out that the cell survival rate is directly related to the dose.The radiation biological effects of large single dose are greater than effects of conventional fractionated treatment at the same sum dose.This paper provided important information of photon energy spectrum and scattering secondary electron spectrum.The research has some important basic significance.The radiotherapy biological effect estimation model provides a quantitative analysis tool,which has important clinical value.