Optimizing Dual-layer Neutron Moderators for Accelerator-based Boron Neutron Capture Therapy: A Geant4 Simulation Study.

In this study, we used Geant4 Monte Carlo simulations to explore how different two-layer combinations of moderator materials can improve the performance of accelerator-based boron neutron capture therapy (BNCT). We tested 16 pairings of aluminum oxide (Al2O3), titanium(III) fluoride, lithium bromide (LiBr), and lithium carbonate to see how each affected neutron and gamma radiation levels-both at the beam exit and within a simulated tumor. To evaluate their performance, we applied a weighted scoring system that considered both treatment effectiveness and patient safety. Our results showed that a dual-layer configuration of LiBr (Configuration N) delivered the highest thermal neutron dose to the tumor, making it the most effective for treatment. On the other hand, a double layer of Al2O3 (configuration P) excelled in minimizing harmful radiation outside the tumor area. Some setups, like LiBr + Al2O3 (configuration G), struck a good balance between efficacy and safety. These insights can help guide the development of more efficient and safer beam-shaping assemblies for clinical BNCT applications.