Prompt Gamma Rays Detected With a BGO Block Compton Camera Reveal Range Deviations of Therapeutic Proton Beams
Prompt Gamma Rays Detected With a BGO Block Compton Camera Reveal Range Deviations of Therapeutic Proton Beams
复制标题
DOI：
10.1109/tns.2016.2622162
复制
发表时间：
2017-01-01
影响因子：
4.4
通讯作者：
Enghardt, W.
中科院分区：
文献类型：
--
作者：
Hueso-Gonzalez, F.;Pausch, G.;Enghardt, W.
由于质子径迹末端的电离密度增加，质子的剂量沉积分布对于肿瘤治疗是有意义的。然而，对质子停止点的不准确了解限制了治疗的精度。瞬发伽马射线是辐射的副产品，是间接测量粒子射程的候选方法。康普顿相机已被提出用于快速伽马射线成像，但存在高触发率和低重合效率的问题。在临床环境中的可行性还有待证明。在德累斯顿大学的Protonen治疗中心，部署了两个面对面排列的锗酸铋(BGO)块探测器，用于对质子铅笔束照射的均匀目标进行成像测试。进行了靶面移位、靶面厚度增加和束流能量变化实验。在低质子束电流下，每次测量持续约15分钟。分析了1厘米质子射程偏差对反投影图像的影响。估计了有效康普顿事件的数量以及铅笔束扫描的现实治疗计划中预期的触发率。结果支持使用高密度材料，尽管其能量分辨率适中，以最大限度地提高符合效率。然而，它们阻碍了两平面康普顿相机在具有常见束流的临床场景中的适用性。
The dose deposition profile of protons is interesting for tumour treatment due to the increased ionization density at the end of their track. However, the inaccurate knowledge of the proton stopping point limits the precision of the therapy. Prompt gamma rays, a by-product of the irradiation, are candidates for an indirect measurement of the particle range. Compton cameras have been proposed for prompt gamma ray imaging, but struggle with high trigger rates and low coincident efficiency. The feasibility in a clinical environment has yet to be proved. At Universitats Protonen Therapie Dresden, two bismuth germanate (BGO) block detectors arranged face-to-face are deployed for imaging tests with a homogeneous target irradiated by a proton pencil beam. Shifts of the target, increase of its thickness and beam energy variation experiments are conducted. Each measurement lasts about 15 minutes at a low proton beam current. The effect of one centimetre proton range deviations on the backprojected images is analysed. The number of valid Compton events as well as the trigger rate expected in a realistic treatment plan with pencil beam scanning are estimated. The results support the use of a high density material despite its moderate energy resolution, in order to maximize the coincident efficiency. Nevertheless, they discourage the applicability of a two-plane Compton camera in a clinical scenario with usual beam currents.