Real-time in vivo proton range verification in proton therapy with thallium bromide detectors

总结 使用质子的放射治疗是一个有吸引力的选择，因为它有可能更好地保护健康组织 与光子或电子辐射相比，由于试验结果表明它可以取代手术， 也是根治癌症的方法质子疗法利用有限范围的重带电粒子， 在其路径末端（布拉格峰）出现强度最大值，随后剂量急剧下降。然而，在这方面， 基于计算机断层摄影（CT）扫描预测质子范围具有估计不确定性。为 近端关键器官和有限可及性（头部和颈部）的治疗，高度异质性（肺）， 或显著的呼吸运动（肝脏），这样的不确定性太高，并且在最好的情况下，治疗是有挑战性的，如果 不是不可能需要新的仪器来监测布拉格峰的位置，精度为1-2 mm 在这些具有挑战性的场景中几秒钟内。 我们建议使用新型切伦科夫电荷感应（CCI）溴化铊（TlBr）探测器进行质子探测。 质子治疗中的距离验证（PRV）。CCI TlBr探测器联合收割机结合了切伦科夫光的探测， 利用半导体探测器的常规读出提供了亚纳秒的定时分辨率， 提供出色的能量分辨率和3D分割。此外，TlBr具有较短的衰减长度 比大多数常用的闪烁材料的闪烁伽马高达6.1 MeV。CCI TlBr探测器提供 一个独特的性能，因为他们提供了同时出色的性能，在能源，时间和空间 分辨率，适合质子治疗中PRV的需求。 在这个项目中，我们将测试使用非准直瞬发伽马计时-康普顿相机的可行性 （PGT-CC）照相机，其基于像素CCI TlBr探测器，用于质子治疗中的PRV。我们将1）制造像素 CCI TlBr探测器具有优化的表面处理，可耦合光电探测器， 持久的电极; 2）在台式设置中表征像素CCI TlBr设备的检测器特征， 密封源，包括能量、空间和时间分辨率; 3）评估PGT-CC的性能 用于PRV的照相机，其在具有加速到67.5MeV的质子的束线中由像素CCI TlBr探测器制成;以及 4)比较我们的PGT-CC相机原型的性能与黄金标准技术， 在临床束线处使用加速到>200 MeV的质子的治疗方案。 该项目目标的实现将决定CCI TlBr探测器成为 质子治疗中PRV最具竞争力的器械。成功执行所提出的检测 系统将允许利用质子治疗的好处，在治疗区域，目前非常 具有挑战性，导致患者健康器官中的治疗功效增加和毒性降低。

Summary Radiotherapy using protons is an attractive option as it has the potential to better preserve healthy tissue compared to radiation with photons or electrons, and because trial outcomes indicate it can replace surgery for radical cancer treatments as well. Proton therapy makes use of the finite range of heavy charged particles with an intensity maximum at the end of their path (Bragg peak) followed by a sharp fall-off of the dose. However, predicting the proton range based on computed tomography (CT) scans carries an estimation uncertainty. For treatments with proximal critical organs and limited accessibility (head and neck), high heterogeneities (lung), or significant breath motion (liver) such uncertainty is too high and the therapy is in the best case challenging, if not impossible. New instrumentation is needed to monitor the location of the Bragg peak to 1-2 mm accuracy within several seconds in these challenging scenarios. We propose to use the novel Cerenkov Charge Induction (CCI) thallium bromide (TlBr) detectors for proton range verification (PRV) in proton therapy. CCI TlBr detectors combine the detection of Cerenkov light, which provides sub-nanosecond timing resolution with the conventional readout of semiconductor detectors, which provides excellent energy resolution and 3-D segmentation. Moreover, TlBr has a shorter attenuation length than most commonly used scintillation materials for prompt-gammas up to 6.1 MeV. CCI TlBr detectors provide a unique performance, as they offer simultaneous excellent performance in energy, time, and spatial resolution, that fits the needs of PRV in proton therapy. In this project, we will test the feasibility of using a non-collimated prompt gamma timing – Compton camera (PGT-CC) camera based on pixel CCI TlBr detectors for PRV in proton therapy. We will 1) manufacture pixel CCI TlBr detectors with optimized surface treatment to couple the photodetector and with highly-stable long- lasting electrodes; 2) characterize the detector features of pixel CCI TlBr devices in a benchtop setting using sealed sources, including energy, spatial, and timing resolution; 3) evaluate the performance of a PGT-CC camera for PRV made with pixel CCI TlBr detectors in a beamline with protons accelerated to 67.5 MeV; and 4) compare the performance of our PGT-CC camera prototype with gold standard techniques following realistic treatment protocols at a clinical beamline with protons accelerated to >200 MeV. The accomplishment of the aims of this project will determine the potential of CCI TlBr detectors to become the most competitive devices for PRV in proton therapy. A successful performance of the proposed detection system would allow to exploit the benefits of proton therapy in treatment regions that are currently very challenging, leading to increased treatment efficacy and lower toxicity in the healthy organs of the patients.