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Accelerator‐based boron neutron capture therapy
Author(s) -
Howard William Bruce
Publication year - 1998
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598286
Subject(s) - neutron capture , neutron , neutron temperature , materials science , particle therapy , beam (structure) , neutron source , proton , proton therapy , radiochemistry , nuclear physics , nuclear medicine , physics , chemistry , medicine , optics
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 with10 B and subsequent irradiation of the tumor with thermal neutrons. The reaction10 B ( n , α ) 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,7 Li ( p , n )E p =2.5 MeV,9 Be ( p , n )E p =3.0–4.0 MeV, and9 Be ( d , n ) E d =2.6 MeV were investigated. Complete data for the9 Be ( p , n ) 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. Using7 Li ( p , n ) and9 Be ( p , n ) , 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, and10 B ( n , α ) ] which are estimated by using energy‐dependent fluence‐to‐kerma conversion factors. Using9 Be ( p , n ) 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. Using9 Be ( d , n ) resulted in lower dose rates. Facility shielding is presented.