Enhancement of Radiation Effectiveness in Proton Therapy: Comparison Between Fusion and Fission Methods and Further Approaches

Proton therapy as a promising candidate in cancer treatment has attracted much attentions and many studies have been performed to investigate the new methods to enhance its radiation effectiveness. In this regard, two research groups have suggested that using boron isotopes will lead to a radiation effectiveness enhancement, using boron-11 agent to initiate the proton fusion reaction (P-BFT) and using boron-10 agent to capture the low energy secondary neutrons (NCEPT). Since, these two innovative methods have not been approved clinically, they have been recalculated in this report, discussed and compared between them and also with the traditional proton therapy to evaluate their impacts before the experimental investigations. The calculations in the present study were performed by Geant4 and MCNPX Monte Carlo Simulation Codes were utilized for obtaining more precision in our evaluations of these methods impacts. Despite small deviations in the results from the two MC tools for the NCEPT method, a good agreement was observed regarding the delivered dose rate to the tumor site at different depths while, for P-BFT related calculations, the GEANT4 was in agreement with the analytical calculations by means of the detailed cross-sections of proton-(11)B fusion. Accordingly, both the methods generate excess dose rate to the tumor several orders of magnitude lower than the proton dose rate. Also, it was found that, the P-BFT has more significant enhancement of effectiveness, when compared to the NCEPT, a method with impact strongly depended on the tumor’s depth. On the other hand, the advantage of neutron risk reduction proposed by NCEPT was found to give no considerable changes in the neutron dose absorption by healthy tissues.