Accelerator‐based boron neutron capture therapy

Abstract

Boron neutron capture therapy (BNCT) is a promising therapy modality for cancer. Clinical trials are under way. BNCT works by a selective loading of tumor cells with and subsequent irradiation of the tumor with thermal neutrons. The reaction is induced which releases 2.3 MeV of energy. In accelerator‐based BNCT, neutrons for this therapy are produced using particle induced reactions. Three reactions, =2.5 MeV, =3.0–4.0 MeV, and =2.6 MeV were investigated. Complete data for the reaction were not previously available. Therefore, 28 thick target neutron spectra were measured, on an absolute basis, using time‐of‐flight techniques. Proton energies of 3.0, 3.4, 3.7, and 4.0 MeV and laboratory angles of 0°–145° were used. The accuracy of the data was confirmed by measuring a different reaction. Monte Carlo techniques were used to design therapy beams. Using and therapy times of 12–25 and 27–60 min, respectively, were predicted (tumor depth 2–6 cm, 15 RBE‐Gy total tumor dose, 10 kW accelerator beam power, 30 ppm boron tumor concentration). The total tumor dose includes four components [fast neutron, thermal neutron, gamma, and which are estimated by using energy‐dependent fluence‐to‐kerma conversion factors. Using and a 1 mA beam current, nearly equivalent therapy beam parameters were predicted with 4.0 and 3.7 MeV protons. For equivalent accelerator beam power, 3.7 MeV protons would produce higher dose rates. Using resulted in lower dose rates. Facility shielding is presented.