Neutron beam optimization for boron neutron capture therapy using the D-D and D-T high-energy neutron sources

A monoenergetic neutron beam simulation study is carried out to determine t he most suitable neutron energy for treatment of shallow and deep-seated br ain tumors in the context of boron neutron capture therapy. Two figures-of- merit-the absorbed skin dose and the absorbed tumor dose at a given depth i n the brain-are used to measure the neutron beam quality. Based on the resu lts of this study: moderators, reflectors, and delimiters are designed and optimized to moderate the high-energy neutrons from the fusion reactions H- 2(d,n)He-3 and H-3(d,n)He-4 down to a suitable energy spectrum. Two differe nt computational models (MCNP and BNCT_RTPE) have been used to study the do se distribution in the brain. With the optimal beam-shaping assembly, a 1-A mixed denteron/triton beam of energy 150 keV accelerated onto a titanium t arget leads to a treatment time of 1 h. The dose near the center of the bra in obtained with this configuration is >65% higher than the dose from a typ ical spectrum produced by the Brookhaven Medical Research Reactor and is co mparable to the dose obtained by other accelerator-produced neutron beams.