Boron Neutron Capture Therapy

A new type of beam shaping assembly, named dual-beam port assembly, was designed, which provides high epithermal neutron flux for the accelerator-based boron neutron capture therapy (BNCT). Neutron beams were produced by using a Li-7(p,n)(7) Be reaction, and the neutrons emitted to the solid angle bin of 50 - 150 degrees to the direction of incoming 2.5 MeV protons were targeted to the beam shaping for using the neutron source beam with relatively low mean energy. The solid angle range was determined by the analysis of neutron spectrum and angle distribution generated from the Li-7(p,n)(7) Be reaction. In this study, many sensitivity calculations using MCNPX were carried out to find good moderators and reflectors for developing the therapeutic beams of high epithermal neutron flux. As a result, heavy water and Fluental (TM) were employed as the moderator, and graphite for reflector. Therapeutic neutrons generated from each beam port were compared with IAEA recommendations to evaluate the performance of the dual-beam port assembly. It was realized that the dual-beam port assembly provides high epithermal neutron flux of 1.01 x 10(9) (#/cm(2)-s-mA) at each side beam port as well as satisfies the beam quality standards recommended by IAEA. Hence, it is feasible to apply this dual-beam port assembly design to the accelerator-based BNCT.