Volume 3, Issue 7 (July 2006)
A Beam-Monitor System for Neutrons and Gamma Rays in the Medical Irradiation Facility of the Kyoto University Research Reactor
The first clinical trial of neutron capture therapy (NCT) using the epithermal neutron beam at the medical irradiation facility of the Kyoto University Reactor was carried out for oral cancer in December 2001. A beam monitor system is required for accurate dose estimation in our present NCT. As the components of thermal, epithermal and fast neutrons and gamma rays must be separately measured, the multichamber method was adopted using a combination of four kinds of ionization chambers. Each chamber has a two-layer wall; the outer wall has a thickness of about 5 m, and the inner wall has a thickness of 10–100 λm. The response can be adjusted by regulating the chamber-gas components. A trial beam-monitor system was made using IC-17M type chambers of Far West Technology, Inc., and its characteristics were experimentally determined.