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Accelerator‐based epithermal neutron beam design for neutron capture therapy
Author(s) -
Yanch J. C.,
Zhou XL.,
Shefer R. E.,
Klinkowstein R. E.
Publication year - 1992
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 - 10.1118/1.596815
Subject(s) - neutron capture , neutron , neutron temperature , neutron source , proton , beam (structure) , nuclear physics , neutron moderator , materials science , physics , nuclear medicine , neutron cross section , optics , medicine
Recent interest in the production of epithermal neutrons for use in boron neutron capture therapy (BNCT) has prompted an investigation into the feasibility of generating such neutrons with a high current proton accelerator. Energetic protons (2.5 MeV) on a 7 Li target produce a spectrum of neutrons with maximum energy of roughly 800 keV. A number of combinations of D 2 O moderator, lead reflector, 6 Li thermal neutron filtration, and D 2 O/ 6 Li shielding will result in a useful epithermal flux of 1.6×10 8 n/s at the patient position. The neutron beam is capable of delivering 3000 RBE‐cGy to a tumor at a depth of 7.5 cm in a total treatment time of 60–93 min (depending on RBE values used and based on a 24‐cm diameter×19‐cm length D 2 O moderator). Treatment of deeper tumors with therapeutic advantage would also be possible. Maximum advantage depths (RBE weighted) of 8.2–9.2 (again depending on RBE values and precise moderator configuration) are obtained in a right‐circular cylindrical phantom composed of brain‐equivalent material with an advantage ratio of 4.7–6.3. A tandem cascade accelerator (TCA), designed and constructed at Science Research Laboratory (SRL) in Somerville MA, can provide the required proton beam parameters for BNCT of deep‐seated tumors. An optimized configuration of materials required to shift the accelerator neutron spectrum down to therapeutically useful energies has been designed using Monte Carlo simulation in the Whitaker College Biomedical Imaging and Computation Laboratory at MIT. Actual construction of the moderator/reflector assembly is currently underway.