10B Concentration, Phantom Size and Tumor Location Dependent Dose Enhancement and Neutron Spectra in Boron Neutron Capture Therapy

Background: The amount of average dose enhancement in tumor loaded with 10B may vary due to various factors in boron neutron capture therapy. Objective: This study aims to evaluate dose enhancement in tumor loaded with 10B under influence of various factors and investigate the dependence of this dose enhancement on neutron spectra changes. Material and Methods: In this simulation study, using 252Cf as a neutron source, the average in-tumor dose enhancement factor (DEF) and neutron energy spectra were calculated for various 10B concentrations, phantom with different sizes and for different tumor locations, through MCNPX code. Results: Obtained results showed that the values of average DEF rise with increasing 10B concentration, phantom diameter (˂ 30 cm) and tumor distance from the source, but this increment is not linear. Conclusion: It was concluded that inequality in average dose enhancement rates, in tumor loaded with 10B under influence of various factors in boron neutron capture therapy, is due to non-identical changes of both the thermal neutron flux with increasing same number of 10B atoms and same thickness of scattering material, and the thermal to fast neutron flux ratio with increasing equal distances of tumor from the source.