Development of proton beam irradiation system for small animals using FFAG accelerator

To evaluate the biological effect of boron compounds on normal tissues in boron neutron capture therapy, it is necessary to compare the radiation effects of neutron irradiation and gamma ray irradiation on small animals in nonclinical studies. Neutron beams and gamma rays are difficult to collimate; thus, it is impossible to administer a dose on each part of the normal tissues of small animals. Therefore, we have developed a method to compare biological effects by irradiating neutrons and gamma rays after irradiating a proton beam to the point just before the threshold dose at which the biological effects occur. We aim to develop an irradiation field that irradiates proton beams locally using a fixed-field alternating-gradient (FFAG) accelerator and a small ridge filter.