Yuanzineng kexue jishu (Sep 2023)
Simulation Study on Energy Spectrum Determination of BNCT Neutron Beam with Multi-foil Activation Method
Abstract
Boron neutron capture therapy (BNCT) is an advanced type of radiotherapy at cellular level, and it has attracted great attention as the next-generation cancer therapy and is booming worldwide in recent years. BNCT uses the short-range (4-10 μm) and high linear energy transfer particles produced from the 10B(n,α)7Li thermal neutron capture reaction on 10B to selectively kill tumor cells while suppressing exposure dose to normal tissues. Since the physical property and biological effect of neutron significantly change with neutron energy, the energy spectrum determination of BNCT neutron beam is of vital importance, and it is directly related to the safety and effectiveness of BNCT. In this paper, the multi-foil activation method was used to determine the energy spectrum of BNCT neutron beam. This method has the advantages of insensitive to γ-rays and little disturbance to the measurement field owing to the small size of activation foils. Considering the activation reaction cross section, resonance absorption energy, half-life, irradiation and radioactivity measurement time, disturbance to the measurement field, cost and other factors, seven materials, that is, InAl, AuAl, LaAl, MnNi, CuAl, W and Sc, were selected as the activation foils in this paper. The 640-group activation reaction cross section of each activation foil was prepared. By comparing the ratios of the simulated activation rate per atom, Rorder, to the ideal activation rate per atom, Rideal, for different arrangements of each activation foil, the optimal arrangement of the activation foils was determined, that is, W, InAl, AuAl, LaAl, MnNi, CuAl and Sc along the incident direction of the BNCT neutron beam. Finally, based on the simulation study of the neutron energy spectrum determination with multi-foil activation method, an effective unfolding method was established in this paper. The energy spectra of four BNCT neutron beams based on accelerators and reactors were determined by using the proposed unfolding method. The selected neutron beams of two accelerator-based BNCT (AB-BNCT) facilities are using p-7Li and D-T reactions, respectively, and the selected reactor-based BNCT neutron beams are produced from two still operating reactors, that is, Tsing Hua Open-pool Reactor (THOR) in Taiwan, China and Kyoto University Reactor (KUR) in Japan, which have been used clinically so far. The results show that the unfolded spectra are in good agreement with the initial spectra of the BNCT neutron beams, which causes the average relative deviations are not larger than 7%, and it meets the requirements of practical applications. The proposed neutron energy spectrum determination method is effective, practical and universal, and it provides a feasible method for determining the energy spectrum of BNCT neutron beam.
