ONLINE BEAM MONITORING FOR NEUTRON-CAPTURE THERAPY AT THE MIT RESEARCH REACTOR

Neutron capture therapy sets new requirements on the measurement and m onitoring of the radiation fields used in this new form of therapy. Be ams used for neutron capture therapy are comprised of mixed radiation fields which include slow, epithermal, and fast neutrons, as well as g amma rays. A computer-based beam monitoring system for epithermal or t hermal neutron capture therapy is described. This system provides accu rate, sensitive, and rapid on-line readout and recording of the variou s beam components. Readout of fluxes, fluences, and corresponding dose s in the target are provided in color coded graphic analog as well as numerical form on the computer monitors. Variations in neutron spectru m or spatial distribution of the beam can be rapidly diagnosed with th e aid of the monitor readout. Redundancy of fluence measurement is pro vided by an independent system using scalers and timers and by utilizi ng reactor power measuring instruments.