基于SiPM的高性能In-Beam TOF-PET的研究

Heavy-ion cancer therapy becomes a kind of advanced tumor radiotherapy technology, for its high position accuracy, the tumor cells could be effectively killed while the healthy tissue cells might be protected. However, the real-time detection exposure dose for the target area is a difficult problem. At present, the PET scan is adopted in the most area to monitor the exposure dose during the process of heavy-ion cancer therapy. The time of image reconstruction for PET technique lasts dozens of minutes, which couldn't achieve the real-time monitoring. With the introduction of time-of-flight (TOF) information in PET scan, it can reduce the irradiation dose and time, restrain the accidental coincidences, improve the signal to noise ratio in the PET image, shorten the time of image reconstruction and improve image quality. While the TOF time resolution is about 200 ps FWHM, the research data show that the image reconstruction during the charged particle tumor treatment could be accomplished, for the purpose of real-time guiding therapy.With the help of this project, the researches in performance optimizations and designs of dedicated In-beam TOF-PET scan for heavy-ion tumor therapy will be developed, which consists of LaBr3 crystals and fast response SiPM arrays. The factors affecting its performance will be investigated. The imaging spatial resolution is expected to be 1.0mm (FWHM), and the time resolution is about 200-300ns (FWHM). The positron radionuclides (e.g., 11 C) will be produced while the beam of 12C irradiating PMMA. By measuring the gamma photons in the annihilations of positron nuclides, the spatial distribution of 3 D image for the C ions can be reconstructed. With the help of the accurate range of the incident particles, directions of incident beam and dose distribution of the positron nuclides , it will be useful to compare the actual dose with the treatment plan, timely correct the dose when the irradiation deviation, so as to ensure the quality of treatment and patient safety.

重离子治疗肿瘤以其定位精度高、对癌细胞杀伤力大、对健康组织影响小，成为一种先进的放疗技术。但如何实时监测靶区的照射剂量是一个难题。目前，国际上均采用PET技术，一次成像需要十几到几十分钟的时间，无法做到照射剂量的实时监测。在PET中引入TOF信息可以有效抑制偶然符合，提高PET影像信噪比，缩短影像重建时间。研究数据表明：当TOF时间分辨200ps FWHM时，可实现带电粒子肿瘤治疗过程的实时现场监测。本课题拟采用LaBr3晶体、快响应SiPM研制TOF-PET原型样机，研究影响其性能的因素，使位置分辨为1.0mm, 时间分辨达到200-300ps。利用12C粒子辐照PMMA时产生的正电子放射性核素(如11C)，测量其湮灭产生的gamma光子，重建C离子空间分布3D影像，准确给出入射粒子的射程、方位和剂量分布等数据,便于与治疗计划的比较，及时校正辐照时的偏差，从而保证治疗质量和病人安全。

重离子治疗肿瘤以其定位精度高、对癌细胞杀伤力大、对健康组织影响小，成为一种先进的肿瘤放疗技术。但如何实时检测靶区的照射剂量是一个难题。目前，国际上均采用PET技术，一次成像需要几十分钟的时间，无法做到照射剂量的实时监测。本课题拟采用LaBr3晶体阵列、快响应SiPM构建在束TOF-PET原型样机，研制了专用的SIPM读出电路，并研究影响其性能的因素，使位置分辨1.0mm (FWHM)。利用12C粒子辐照PMMA时产生的β＋放射性核素(如11C)，测量其湮灭产生的gamma光子，重建C离子空间分布3D影像，准确给出入射粒子的射程、方位和剂量分布等数据，同时便于与治疗处理计划的比较，及时校正辐照时的偏差，从而保证治疗质量和病人安全。研制的样机为实现带电粒子肿瘤治疗过程的实时现场监测奠定基础。研究结果对重离子肿瘤治疗装置专用In-Beam TOF-PET系统的研制积累经验和技术准备。