Feasibility of a Near-Threshold BNCT Neutron Source Based on Phantom Dosimetry

Abstract

Near-threshold boron neutron capture therapy (BNCT) is an accelerator-based concept that produces neutrons from thick lithium targets using proton beam energies only tens of keV above the 7Li(p,n)7Be reaction threshold. Proton energies in this range lead to lower neutron yields than a higher proton energy, such as 2.5MeV, but lower energy neutrons are produced and hence less moderation is required. This allows thinner moderators that place the patient closer to the neutron source. A summary is presented here of calculations and experiments that have been performed that demonstrate the feasibility of near-threshold neutron sources for BNCT. A model for predicting nearthreshold differential neutron yields from thick targets of lithium metal and lithium compounds was developed. Neutron yields from this model were used as neutron sources for Monte Carlo (MCNP) simulations of a head phantom. Calculated dose components were experimentally verified using an acrylic phantom. Initial dose calculations using treatment planning software, which indicate near-threshold neutron sources are competitive with existing reactor BNCT beams, are also presented.