应用蒙特卡罗模拟进行正电子发射断层成像仪散射特性分析

Use of Monte Carlo simulations for the scatter events analysis of PET scanners

通过使用基于Geant4的蒙特卡罗模拟代码GATE对全身用全3D正电子发射断层成像仪和含有挡板的2D/3D小动物用正电子发射断层成像仪进行建模,系统地分析了3D采集条件下正电子发射断层成像仪的散射分数、散射分布、多次散射、视野外散射四个主要方面和2D采集条件下挡板对散射分数和散射分布的影响.针对全3D散射校正的难点:多次散射和视野外散射,设计了附加实验,拟合得到了多次散射光子的百分比随体模横截面积变化的关系和不同环的位置受到视野外散射光子的影响;针对2D散射校正,对挡板引入的散射光子进行分离,单独分析,为这部分散射光子的消去或加入重建过程提供了定量的参考.

Monte Carlo simulation is an essential tool to assist in the design of new medical imaging devices for emission tomography. This paper modeled the full 3D whole body PET scanner and 2D animal PET scanner with septa using Monte Carlo simulation code GATE based on Geant4, analyzed the scatter fraction, scatter distribution, multiple scatter events, and scatter events from outside of FOV under 3D acquisition mode and scatter events from the septa under 2D acquisition mode. For the critical problems of 3D scatter correction： multiple scatter events and scatter events from outside of FOV, we designed additional experiments, got the fitted relationship between the percentage of multiple scatter events and the cross sectional area of the phantom, and the effects of the scatter events from outside of FOV at different ring positions ; for the 2D scatter correction, we separated the scatter events from septa for analysis, and provided a quantitative reference for the elimination of these events or introduction into the procedure of reconstruction.