Ultra-high Dose-rate Carbon-ion Scanning Beam With a Compact Medical Synchrotron Contributing to Further Development of FLASH Irradiation
Masashi Yagi, Shinichi Shimizu, Kazumasa Minami, Noriaki Hamatani, Toshiro Tsubouchi, Masaaki Takashina, Masumi Umezawa, Takuya Nomura, Wataru Mukoyoshi, Teiji Nishio, Masahiko Koizumi, Kazuhiko Ogawa, TATSUAKI KANAI
Abstract
BACKGROUND/AIM: The focus of this report is establishing an irradiation arrangement to realize an ultra-high dose-rate (uHDR; FLASH) of scanned carbon-ion irradiation possible with a compact commonly available medical synchrotron. MATERIALS AND METHODS: carbon ions at 208.3 MeV/u (86 mm in range) per 100 ms. The design takes the utmost care to prevent damage to monitors, particularly in the nozzle, achieved by the uHDR beam not passing through this part of the apparatus. Doses were adjusted by extraction times, using a function generator. After one scan by the carbon-ion beam it became possible to create a field within the extraction time. The Advanced Markus chamber (AMC) and Gafchromic film are then able to measure the absolute dose and field size at a plateau depth, with the operating voltage of the chamber at 400 V at the uHDR for the AMC. RESULTS: corresponding to a dose-rate of 92.3 Gy/s (±1.3%). The dose was ca. 0.7, 1.5, 2.9, and 5.4 Gy depending on dose-rate and field size, with the rate of killed cells increasing with the irradiation dose. CONCLUSION: The compact medical synchrotron achieved FLASH dose-rates of >40 Gy/s at different dose levels and in useful field sizes for research with the apparatus and arrangement developed here.