同时实现亚毫米高分辨率和高效率PET探测器方法研究

Preclinical positron emission tomography (PET) plays a very valuable role in biomedical research. Due to the limitation of detector technology, however, the most important performance parameters such as spatial resolution and sensitivity of these systems fall well short of what can theoretically be achieved. In this proposal innovative depth encoding PET detectors will be developed by using dual-ended readout of pixelated LYSO array with the new silicon photomultipliers (SiPM). The aim is to develop PET detectors that simultaneously achieve high resolution (0.5 mm crystals), high sensitivity (20 mm long) and high depth of interaction resolution (<3 mm). In order to reduce the effects of SiPM noise and further improve the capability of detectors to resolve the small crystals, new row-column sum and individual SiPM readout methods plus innovative energy weighted and position weighted iterative flood histogram calculation methods will be proposed and tested. The outcomes of this proposal are optimized LYSO arrays, SiPM readout method and flood histogram calculation method as well as fast and multichannel electronics and PET system design. The preclinical PET scanner using detectors developed in this work can simultaneously achieve high spatial resolution in all field of view and high sensitivity. This will improve the quantitative accuracy of all current applications and open the window on new applications of PET imaging.

小动物PET在生物医学研究中发挥着重大价值，但由于其中核心探测器技术的瓶颈， PET的分辨率和探测效率等核心性能远未达到其物理极限。本课题拟从探测器创新的读出技术入手，研究新型硅光电倍增管（SiPM）阵列双端读出硅酸钇镥（LYSO）晶体阵列来研发深度测量PET探测器，目标是研发同时达到高位置分辨率（晶体大小0.5毫米）、高效率（长度为20毫米）和高深度分辨率（<3毫米）的PET探测器。发展新的行列相加或单独读出技术，结合创新的能量加权与位置加权迭代晶体分辨图算法，降低SiPM阵列噪声的影响来提升探测器的晶体分辨能力。通过比较研究，获得优化的晶体阵列参数、探测器读出方法、晶体分辨图计算算法及PET系统几何设计。使用本项目创新方法的探测器将推动小动物PET成像系统同时达到全视野高空间分辨率和高效率，不仅可提高现有PET应用的定量成像精度，而且有望开创PET成像研究的新领域。

本项目按照原课题申请书的目标，测试比较了三种使用不同晶体间反射膜（ESR，TORAY和硫酸钡）的高分辨率双端读出深度测量PET探测器的性能，最终研发可分辨0.5毫米晶体单元，达到小于2毫米深度分辨率、小于25%能量分辨率和小于1.2纳秒时间分辨率的高性能小动物PET探测器；研发4×4和8×8 SiPM阵列的单独读出、行列读出和电阻网络读出电路；研发支持双端读出PET探测器在线位置和深度计算的PET后端电子学系统；建立基于GATE的小动物PET蒙特卡罗模拟平台，用于小动物PET成像仪器性能的估算和图像重建算法研发的数据的产生；圆满完成项目的预期目标。此外还研发半连续晶体探PET测器和基于晶体间光分享的深度测量PET探测器。本项目在PET探测器和电子学方面取得的研究成果，为今后研发高性能小动物PET成像仪器奠定了基础。