Department of Radiation Oncology, Physics Division, Washington University in St. Louis School of Medicine, St. Louis, MO 63108, United States of America.
Emory Proton Therapy Center, Atlanta, GA 30308, United States of America.
Phys Med Biol. 2022 Aug 23;67(17). doi: 10.1088/1361-6560/ac8593.
. Proton pencil beam scanning (PBS) treatment fields needs to be verified before treatment deliveries to ensure patient safety. In current practice, treatment beam quality assurance (QA) is measured at a few selected depths using film or a 2D detector array, which is insensitive and time-consuming. A QA device that can measure all key dosimetric characteristics of treatment beams spot-by-spot within a single beam delivery is highly desired.. We developed a multi-layer strip ionization chamber (MLSIC) prototype device that comprises of two layers of strip ionization chambers (IC) plates for spot position measurement and 64 layers of plate IC for beam energy measurement. The 768-channel strip ion chamber signals are integrated and sampled at a speed of 3.125 kHz. It has a 25.6 cm × 25.6 cm maximum measurement field size and 2 mm spatial resolution for spot position measurement. The depth resolution and maximum depth were 2.91 mm and 18.6 cm for 1.6 mm thick IC plate, respectively. The relative weight of each spot was determined from total charge by all IC detector channels.. The MLSIC is able to measure ionization currents spot-by-spot. The depth dose measurement has a good agreement with the ground truth measured using a water tank and commercial one-dimensional (1D) multi-layer plate chamber. It can verify the spot position, energy, and relative weight of clinical PBS beams and compared with the treatment plans.. The MLSIC is a highly efficient QA device that can measure the key dosimetric characteristics of proton treatment beams spot-by-spot with a single beam delivery. It may improve the quality and efficiency of clinical proton treatments.
. 质子铅笔束扫描（PBS）治疗场在治疗交付前需要进行验证，以确保患者安全。在当前的实践中，使用胶片或二维探测器阵列在几个选定的深度测量治疗束质量保证（QA），这是不敏感和耗时的。非常需要一种能够在单次束递送中逐个测量治疗束所有关键剂量特性的 QA 设备。.. 我们开发了一种多层条带电离室（MLSIC）原型设备，它由两层条带电离室（IC）板组成，用于测量点位置，以及 64 层板 IC 用于测量束能量。768 通道条带电离室信号以 3.125 kHz 的速度进行积分和采样。它具有 25.6 cm × 25.6 cm 的最大测量场尺寸和 2 毫米的点位置测量空间分辨率。对于 1.6 毫米厚的 IC 板，深度分辨率和最大深度分别为 2.91 毫米和 18.6 厘米。每个点的相对权重由所有 IC 探测器通道的总电荷确定。.. MLSIC 能够逐个测量电离电流。深度剂量测量与使用水箱和商业一维（1D）多层板室测量的实际情况非常吻合。它可以验证临床 PBS 束的点位置、能量和相对权重，并与治疗计划进行比较。.. MLSIC 是一种高效的 QA 设备，能够在单次束递送中逐个测量质子治疗束的关键剂量特性。它可以提高临床质子治疗的质量和效率。
