Calculation of cellular S values for α particle based on Monte Carlo simulation

In the case of radiation therapy and BNCT, alpha particles transport the energy to human tissue by second electrons. However, in cellular scale alpha sources do not have a uniform distribution. In order to get the target dosimetry discrepancy by different source locations, a computational application to calculate the S value with Monte Carlo toolkit Geant4 was programmed. S values of two dimensions, twelve energies, and three source locations were calculated. Compared with MIRD results, the difference between both is within 1%. Geant4 toolkit to calculate the cell dosimetry was proved to be believable and flexible. A couple of S values of alpha particles produced in BNCT with 1.47 MeV and 1.78 MeV were calculated. To some extent these values can become reference values in clinical therapy.