基于三光子软符合的PET双核素同时成像技术研究

常规PET成像无法对两种核素同时显像，制约了PET技术的应用范围。本项目提出一种基于三光子软符合技术的PET成像方法，致力于两种核素（一种纯正电子发射同位素和一种非纯正电子发射同位素）同时显像。纯正电子发射同位素在正电子衰变时会同时发出2个伽马光子，而非纯正电子发射同位素衰变时会同时发出3个伽马光子。本项目利用不同类型同位素发出伽马光子个数上的差异，研究基于软件的伽马光子时间符合的快速处理方案，实现双光子符合事件和三光子符合事件的有效分离。综合利用符合光子个数、瞬发光子能量、核素空间分布特性，研究双核素图像分离的有效方法。为了提高双核素探测效率，采用大立体角PET成像系统进行核素信号采集。为了解决大立体角探测引起的深度信息模糊效应，研究精确描述伽马光子在空间和晶体内传播的数学模型，并开发对应的快速重建算法。本项目将为PET双核素同时显像提供了便捷有效的解决方案，扩展PET应用范围。

Conventional PET imaging systems cannot achieve simultaneous imaging of two radioisotopes, which severely restricts the application of PET technology in clinical and preclinical research. In order to solve this problem, this project proposes a software-based three-photon coincidence technology for the simultaneous imaging of a pure positron emitting radionuclide and a non-pure positron emitting radionuclide. The pure radioisotopes emit two gammas during decay, while the non-pure radioisotopes emit three gammas during decay. This project will make use of the differences in the decay mechanisms of two different types of radioisotopes, and proposes a software-based fast processing scheme for gamma photon coincidences, and comprehensively utilizes the number of photons, the energy of prompt gamma, and the spatial distribution characteristics of radioisotope to separate the information of two radioisotope. In order to improve the efficiency of the photon detection of the two radioisotopes, this project intends to use a large solid angle PET imaging system. Since this large PET system is along with the effect of depth of information blurring, an accurate model photon propagation is studied by using the combination of the analytical method and Monte Carlo method. We also will develop the corresponding fast reconstruction algorithm for dual-isotope PET imaging. Overall, this project will provides a convenient and fast solution for the simultaneous PET imaging of dual radioisotopes, which is helpful to extend the application of PET imaging.