Development and construction of a neutron beam line for accelerator-based boron neutron capture synovectomy

A potential application of the B-10(n,alpha)Li-7 nuclear reaction for the t reatment of rheumatoid arthritis, termed Boron Neutron Capture Synovectomy (BNCS), is under investigation. In an arthritic joint, the synovial lining becomes inflamed and is a source of great pain and discomfort for the affli cted patient. The goal of BNCS is to ablate the synovium, thereby eliminati ng the symptoms of the arthritis. A BNCS treatment would consist of an intr a-articular injection of boron followed by neutron irradiation of the joint . Monte Carlo radiation transport calculations have been used to develop an accelerator-based epithermal neutron beam line for BNCS treatments. The mo del in eludes a moderator/reflector assembly, neutron producing target, tar get cooling system, and arthritic joint phantom. Single and parallel oppose d beam irradiations have been modeled for the human knee, human finger, and rabbit knee joints. Additional reflectors, placed to the side and back of the joint, have been added to the model and have been shown to improve trea tment times and skin doses by about a factor of 2. Several neutron-producin g charged particle reactions have been examined for BNCS, including the Be- 9(p,n) reaction at proton energies of 4 and 3.7 MeV, the Be-9(d,n) reaction at deuteron energies of 1.5 and 2.6 MeV, and the Li-7(p,n) reaction at a p roton energy of 2.5 MeV. For an accelerator beam current of 1 mA and synovi al boron uptake of 1000 ppm, the time to deliver a therapy dose of 10 000 R BE cGy ranges from 3 to 48 min, depending on the treated joint and the neut ron producing charged particle reaction. The whole-body effective dose that a human would incur during a knee treatment has been estimated to be 3.6 r em or 0.75 rem, for 1000 ppm or 19 000 ppm synovial boron uptake, respectiv ely, although the shielding configuration has not yet been optimized. The M onte Carlo design process culminated in the construction, installation, and testing of a dedicated BNCS beam line on the high-current tandem electrost atic accelerator at the Laboratory for Accelerator Beam Applications at the Massachusetts Institute of Technology. (C) 2000 American Association of Ph ysicists in Medicine. [S0094-2405(00)02401-9].