Performance Study of a Beam Monitoring System for Proton Therapy

• Main Authors: Shu-Jhen Dai, 戴淑眞
• Other Authors: Willis T. Lin
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/13831110060089681366

碩士 === 國立中央大學 === 物理研究所 === 99 === Proton therapy facilities will be in operation in Taiwan in few years. It is important to have a reliable beam monitoring system for daily operation. A prototype 16-channel strip ionization chamber with custom-design readout electronics and a multi-layer Faraday cup have been developed for this purpose. In this study, three aims are measuring the depth-dose distribution, beam profile and beam energy. The characteristics and performance of the ionization chamber have been studied using the beam at the Institute of Nuclear Energy Research (INER) and the Cyclotron and Radioisotope Center (CYRIC) of Tohoku University. The depth-dose distributions (Bragg curve) of protons in Acrylonitrile Butadiene Styrene (ABS) are obtained and the results agree with the Geant4 simulation well. Beam spread with depth is measured. The quasi 3-D beam profile with 80 MeV proton beam at CYRIC are measured by six ionization chambers arranged in X- and Y-direction alternatively. Beam energy used at CYRIC is measured with the multi-layer Faraday cup (MLFC). A set of beam energy and its spread, by passing the beam through copper block with various thicknesses, is measured with the MLFC. The method of maximum likelihood is used to fit the data with the GEANT4 simulation. The best result obtained is 77.8 ± 0.1 MeV, which agrees well with the NMR probe measurement.