A feasibility study on a small electron linear accelerator-based beam shaping assembly for boron neutron capture therapy

We aimed to explore the possibility of realizing a beam shaping assembly (BSA) driven by a 15-kW beam of 33-MeV electrons of an electron linear accelerator (LINAC) when a boronophenylalanine is adopted as a boron carrier. Simulation calculations were performed to design two types of BSAs driven by the small LINAC. The one was an experimental BSA, and the other was a high-performance BSA. Calculations of the RBE dose in a phantom exposed to a beam of the high-performance BSA showed that the therapeutic depth, the advantage depth, and the irradiation time were 5.1 cm, 8.3 cm, and 3421 s, respectively. The experimental BSA was constructed, and neutron measurement experiments were performed to confirm the neutron flux in a phantom irradiated by a beam of the experimental BSA. The experiments confirmed that simulation calculations provide a proper estimate for the axial distribution of a neutron dose in a phantom exposed to a beam of the experimental BSA, and ensured that that the high-performance BSA will deliver effective doses to deep seated lesions in tolerable irradiation times.