Modeling the NHEJ repair of DNA damage induced by electrons calculated using the MCNPX and Geant4-DNA codes

In radiotherapy, ionizing radiation is used to damage cells. Monte Carlo simulations of radiation interactions with DNA give us good information about the type of damage and their repair process, which can be very useful in treating cancer and protecting against radiation. The ionizing radiation damage includes single- and double-strand breaks as well as base lesions (SSB, DSB, BL). The DNA damage can be repaired through some processes within the cell. DNA damage, especially of DSBs that are mis-repaired or unrepaired, can result in cell death. This process plays a crucial role in killing cancer cells and treating cancer. In this research, first, the dose was calculated in the cell nucleus with the MCNPX code. Then, the possibility of different damage types in DNA was investigated by simulating the physical and chemical processes of low and high-energy electrons with the Geant4-DNA code. Then with the help of the Matlab software and mathematical modeling, we investigated the repair of DSBs for the latter energies. The results show that at ranging energies of 100 to 300 eV, the number of breaks increases, and for higher energies, it decreases due to the electron range in the cell nucleus. The repair reaction rate is also calculated from the NHEJ presynaptic process for ranging energies 100 eV to 1 MeV. In the repair section, the repair time at low energies is longer than the higher energies due to more DSBs.