An accurate knowledge of in vivo proton dose distribution is key to fully utilizing the potential advantages of proton therapy. Two representative indirect methods for in vivo range verification, namely, prompt gamma (PG) imaging and positron emission tomography (PET), are available. This study proposes a PG-PET system that combines the advantages of these two methods and presents detector geometry and background reduction techniques optimized for the PG-PET system. The characteristics of the secondary radiations emitted by a water phantom by interaction with a 150 MeV proton beam were analysed using Geant4.10.00, and the 2-D PG distributions were obtained and assessed for different detector geometries. In addition, the energy window (EW), depth-of-interaction (DOI), and time-of-flight (TOF) techniques are proposed as the background reduction techniques. To evaluate the performance of the PG-PET system, the 3-D dose distribution in the water phantom caused by two proton beams of energies 80 MeV and 100 MeV was verified using 16 optimal detectors. The thickness of the parallel-hole tungsten collimator of pitch 8 mm and width 7 mm was determined as 200 mm, and that of the GAGG scintillator was determined as 30 mm, by an optimization study. Further, 3-7 MeV and 2-7 MeV were obtained as the optimal EWs when the DOI and both the DOI and TOF techniques were applied for data processing, respectively; the detector performances were improved by about 38% and 167%, respectively, compared with that when applying only the 3-5 MeV EW. In this study, we confirmed that the PG distribution can be obtained by simply combining the 2-D parallel hole collimator and the PET detector module. In the future, we will develop an accurate 3-D dose evaluation technique using deep learning algorithms based on the image sets of dose, PG, and PET distributions for various proton energies.

中文翻译：

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集成的即时伽马成像和正电子发射断层扫描系统的开发，用于体内3-D剂量验证：蒙特卡洛研究。

准确了解体内质子剂量分布是充分利用质子治疗潜在优势的关键。有两种用于体内范围验证的代表性间接方法，即即时伽玛（PG）成像和正电子发射断层扫描（PET）。这项研究提出了一种PG-PET系统，该系统结合了这两种方法的优点，并提出了针对PG-PET系统优化的检测器几何形状和背景降低技术。使用Geant4.10.00分析了水幻影通过与150 MeV质子束相互作用而发射的二次辐射的特性，获得了二维PG分布并针对不同的探测器几何形状进行了评估。此外，能量窗口（EW），交互深度（DOI），提出了飞行时间（TOF）技术作为背景减少技术。为了评估PG-PET系统的性能，使用16个最佳探测器验证了由两个80 MeV和100 MeV能量的质子束引起的水体模中的3-D剂量分布。通过优化研究，将节距为8 mm，宽为7 mm的平行孔钨准直仪的厚度确定为200 mm，将GAGG闪烁体的厚度确定为30 mm。此外，当DOI和DOI和TOF技术都用于数据处理时，分别获得3-7 MeV和2-7 MeV作为最佳EW。与仅使用3-5 MeV EW时相比，探测器的性能分别提高了约38％和167％。在这个研究中，我们证实，只需将二维平行孔准直仪和PET检测器模块组合即可获得PG分布。将来，我们将基于各种质子能量的剂量，PG和PET分布的图像集，使用深度学习算法开发一种精确的3-D剂量评估技术。