The goal of this program is to determine the feasibility of synovectomy using the 10B(n,alpha)7 Li nuclear reaction with an external neutron beam for the treatment of rheumatoid arthritis (RA). This therapy has two potential advantages over surgical or radiation synovectomy with beta- emitters for RA: it is non-invasive and it does not require the administration of radioactive materials to the patient. Recent experiments have shown that very high boron concentrations can be achieved in active human synovium in vitro. However, the required neutron beam characteristics for therapy are presently unknown. In Phase I, Monte Carlo simulation techniques will be used to determine the required boron distribution and neutron beam parameters for successful therapy of the human synovial joints most commonly involved in RA. An optimized accelerator-based neutron beam design which minimizes radiation dose to non-target tissues in neutron capture synovectomy will then be developed. This work will lead to the construction of a neutron therapy beamline in Phase II and will provide the quantitative basis for future in vivo studies of synovial tissue ablation using the 10B(n,alpha) reaction. PROPOSED COMMERCIAL APPLICATION: Rheumatoid arthritis affects approximately 1% of the population of the United States. The proposed synovectomy procedure could be performed on an outpatient basis at about one-tenth the cost of a surgical synovectomy. If this technique is shown to be safe and effective, a large market for therapy beams will exist.