闪烁体探测器在质子重离子治疗质控中的应用

Utilization of a scintillator detection system for quality assurance in carbon-ion and proton therapy

目的采用自制二维闪烁体探测器对主动式点扫描质子重离子加速器放疗系统进行质控检测,为质子重离子束的质量(束斑位置、束斑大小、虚源、深度分布曲线及射程等)提供快速检测方法和参考。方法探测系统由硫氧化钆闪烁体荧光屏、不锈钢板和光学数码相机组成。将质子重离子束垂直入射到闪烁体荧光屏转化为可见光,经不锈钢镜面反射至相机成像仪上形成图像信号,通过对信号分析处理,获取质控参数。结果多丝正比室和闪烁体探测测得量束斑位置偏差<1mm。多丝正比室测得束斑大小与用闪烁体探测系统器测得量值之间差值:质子为(1.40±0.59)mm,碳离子为(0.5±0.08)mm。429.25MeV/u碳离子的x、y轴虚源分别为751.8、805.6cm,与物理距离差值<1%。测得287.5MeV/u碳离子的射程为160mm。结论自制闪烁体探测器可以测量束斑位置、束斑大小、虚源、深度分布曲线及射程等。该探测器可作为一项质子重离子治疗质控的有效工具。

Objective A two-dimensional(2D)in-house-built scintillator detection system(SDS)was utilized for quality assurance of the active spot scanning proton and heavy ion accelerator,aiming to establish a rapid detection method and provide reference for the quality of proton and heavy ion beam(spot position,spot size,virtual source-to-axis distance,profile depth dose distribution and beam range).Methods The SDS consisted of a ceramic gadolinium-sulfoxylate phosphor-scintillating screen,a mirror and a commercial digital camera.The dose distribution image was obtained based on scintillator,mirror reflector and optical signal acquisition device to transform the proton and heavy ion beam into visible light through sulfur gadolinium oxide scintillator and collect visible light information to meet the clinical requirements for the quality of proton and heavy ion beam.Results The deviation of spot position measured by multifilament proportional chamber and the SDS was less than 1mm.The differences of beam spot size measured by multifilament proportional chamber and the SDS were(1.40±0.59)mm for protons,and(0.5±0.08)mm for carbon ions.For 429.25MeV/u carbon,the virtual source-to-axis distance(VSAD)at the x-and y-axes was 751.8cm and 805.6cm.And difference between physical distance and virtual source-to-axis distance was less than 1%.The range of 287.5MeV/u carbon measured by SDS was 160mm.Conclusions The in-house-built scintillator detector can measure beam spot position and size,virtual source,depth distribution curve and range,which can be used as an effective tool for quality assurance control of proton and heavy ion therapy.