Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75057, United States of America.
Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX 77000, United States of America.
Phys Med Biol. 2024 Jul 17;69(15). doi: 10.1088/1361-6560/ad56f4.
Develop a prototype on-line positron emission tomography (PET) scanner and evaluate its capability of on-line imaging and intra-fractionated proton-induced radioactivity range measurement.Each detector consists of 32 × 32 array of 2 × 2 × 30 mmLutetium-Yttrium Oxyorthosilicate scintillators with single-scintillator-end readout through a 20 × 20 array of 3 × 3 mmSilicon Photomultipliers. The PET can be configurated with a full-ring of 20 detectors for conventional PET imaging or a partial-ring of 18 detectors for on-line imaging and range measurement. All detector-level readout and processing electronics are attached to the backside of the system gantry and their output signals are transferred to a field-programable-gate-array based system electronics and data acquisition that can be placed 2 m away from the gantry. The PET imaging performance and radioactivity range measurement capability were evaluated by both the offline study that placed a radioactive source with known intensity and distribution within a phantom and the online study that irradiated a phantom with proton beams under different radiation and imaging conditions.The PET has 32 cm diameter and 6.5 cm axial length field-of-view (FOV), ∼2.3-5.0 mm spatial resolution within FOV, 3% sensitivity at the FOV center, 18%-30% energy resolution, and ∼9 ns coincidence time resolution. The offline study shows the PET can determine the shift of distal falloff edge position of a known radioactivity distribution with the accuracy of 0.3 ± 0.3 mm even without attenuation and scatter corrections, and online study shows the PET can measure the shift of proton-induced positron radioactive range with the accuracy of 0.6 ± 0.3 mm from the data acquired with a short-acquisition (60 s) and low-dose (5 MU) proton radiation to a human head phantom.This study demonstrated the capability of intra-fractionated PET imaging and radioactivity range measurement and will enable the investigation on the feasibility of intra-fractionated, range-shift compensated adaptive proton therapy.
开发一种在线正电子发射断层扫描 (PET) 扫描仪原型，并评估其在线成像和分次内质子诱导放射性射程测量的能力。每个探测器由 32×32 个 2×2×30mm 的硅酸镥闪烁体阵列组成，通过 20×20 个 3×3mm 的硅光电倍增管阵列进行单个闪烁体端读取。PET 可以配置为 20 个探测器的全环用于常规 PET 成像，或者 18 个探测器的部分环用于在线成像和射程测量。所有探测器级别的读取和处理电子设备都连接到系统龙门架的背面，它们的输出信号被传输到基于现场可编程门阵列的系统电子设备和数据采集设备，该设备可以放置在龙门架 2m 之外。通过在体模内放置具有已知强度和分布的放射性源的离线研究和在不同辐射和成像条件下用质子束辐照体模的在线研究，评估了 PET 的成像性能和放射性射程测量能力。PET 的直径为 32cm，轴向长度为 6.5cm，视野（FOV）内的空间分辨率约为 2.3-5.0mm，FOV 中心的灵敏度为 3%，能量分辨率为 18%-30%，符合时间分辨率约为 9ns。离线研究表明，即使没有衰减和散射校正，PET 也可以以 0.3±0.3mm 的精度确定已知放射性分布的远端下降边缘位置的移动，在线研究表明，PET 可以以 0.6±0.3mm 的精度测量质子诱导正电子放射性射程的移动，从用短采集（60s）和低剂量（5MU）质子辐射获得的数据到人体头部体模。这项研究证明了分次内 PET 成像和放射性射程测量的能力，并将使分次内、射程移动补偿自适应质子治疗的可行性研究成为可能。
