Biological dosimetry of neutron beams for neutron capture therapies

Abstract

Boron neutron capture therapies using the 10B(n,a)7Li reaction have been proposed as treatments for glioblastoma multiforme, metastatic melanoma, rheumatoid arthritis, and other debilitating conditions. This thesis presents the first combined biological and physical dosimetry interbeam comparison data of three neutron beams used in boron neutron capture therapies: the Massachusetts Institute of Technology (MIT) and Brookhaven National Laboratory epithermal neutron beam facilities previously used in Phase I/II human clinical trials of boron neutron capture therapy (BNCT), and the boron neutron capture synovectomy (BNCS) facility at MIT. The biological dosimetry methodology developed included in vitro irradiation of rodent cells at various depths in a water-filled phantom that simulated healthy tissue. These experiments evaluated the biological effectiveness of the neutron and photon components since no boron was present. Cell survival at a given dose was dependent upon the depth in the phantom as a result of moderation and attenuation of the beam components by overlying water. Results were compared with 250 kVp X-ray irradiations to determine relative biological effectiveness (RBE) values of the beams; neutron RBE values were calculated from the beam RBE values.