In proton therapy, a highly conformal proton dose can be delivered to the tumor by means of the steep distal dose penumbra at the end of the beam range. The proton beam range, however, is highly sensitive to range uncertainty, which makes accurately locating the proton range in the patient difficult. In-vivo range verification is a method to manage range uncertainty, one of the promising techniques being prompt gamma imaging (PGI). In earlier studies, we proposed gamma electron vertex imaging (GEVI), and constructed a proof-of-principle system. The system successfully demonstrated the GEVI imaging principle for therapeutic proton pencil beams without scanning, but showed some limitations under clinical conditions, particularly for pencil beam scanning proton therapy. In the present study, we upgraded the GEVI system in several aspects and tested the performance improvements such as for range-shift verification in the context of line scanning proton treatment. Specifically, the system showed better performance in obtaining accurate prompt gamma (PG) distributions in the clinical environment. Furthermore, high shift-detection sensitivity and accuracy were shown under various range-shift conditions using line scanning proton beams.

在质子治疗中，可以通过射束范围末端的陡峭远端剂量半影向肿瘤输送高度适形的质子剂量。然而，质子束范围对范围不确定性高度敏感，这使得准确定位患者体内的质子范围变得困难。体内距离验证是一种管理距离不确定性的方法，其中一种很有前途的技术是快速伽马成像 (PGI)。在早期的研究中，我们提出了伽马电子顶点成像（GEVI），并构建了一个原理验证系统。该系统成功地展示了 GEVI 成像原理用于治疗性质子笔形束而无需扫描，但在临床条件下显示出一些局限性，特别是笔形束扫描质子治疗。在本研究中，我们在几个方面对 GEVI 系统进行了升级，并测试了性能改进，例如在线扫描质子治疗背景下的距离偏移验证。具体来说，该系统在临床环境中获得准确的即时伽马 (PG) 分布方面表现出更好的性能。此外，