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为获得适用于HIRFL装置主动式点扫描束流配送系统配送的碳离子束,利用Monte Carlo(MC)工具SHIELD-HIT12A研究了配送距离和微型脊形过滤器结构周期对治疗室等中心处束斑半高宽(FWHM)和剂量平坦度的影响。模拟研究发现:束流配送距离越短,束斑FWHM越小,但剂量平坦度越差;微型脊形过滤器结构周期是影响剂量平坦度的关键因素,周期越小,剂量平坦度越好。通过模拟研究得出:在HIRFL装置重离子治疗终端将真空窗设置在距等中心距离小于125 cm时,采用结构周期为2 mm微型脊形过滤器可以满足主动式点扫描照射对束斑FWHM和剂量平坦度的要求。
In order to obtain a carbon ion beam suitable for delivery to a HIRFL active point-scan beam delivery system, Monte Carlo (MC) tool SHIELD-HIT12A was used to study the effect of the delivery distance and the microstrip ridge structure period on the beam spot Effect of FWHM and dose flatness. The simulation results show that the shorter the beam delivery distance, the smaller the FWHM of the beam spot, but the worse the dose flatness. The structure period of miniature ridge filter is the key factor affecting the dose flatness. The smaller the period, the better the dose flatness. Through the simulation study, it is concluded that when the vacuum window of the HIRFL device is set at a distance of less than 125 cm from the isocenter at the heavy ion therapy terminal, the microstrip filter with 2 mm structure period can meet the requirements of active spot scanning for FWHM and Dose flatness requirements.