PET探测器几何结构与系统响应矩阵关系初探

摘要

PET的系统响应矩阵代表了系统对系统视场(Field of View,以下简称FOV)中各点的探测灵敏度.它由PET探测器的几何结构和PET数据采集中的各种物理因素决定.如果忽略物理因素的影响,仅考虑探测器几何结构,此时系统响应矩阵被称为几何灵敏度矩阵,特定的探测器几何结构对应唯一的几何灵敏度矩阵.研究获取了内径相同、晶体数不同的6种环形探测器结构的几何灵敏度矩阵,绘制该矩阵的秩随图像大小变化的曲线,初步探讨几何灵敏度矩阵与不同几何结构探测器采样的关系.该曲线波动特征与系统视场内采样密度变化相一致,且其提供了图像重建可获得唯一解时对应的FOV区域.该结果可以帮助分析重建图像的特征和指导针对不同大小对象成像的探测器选择和设计.%The system response matrix (SRM) of Positron Emission Tomography (PET), which is dependent on geometry of PET scanner and various physical factors in PET data acquisition, represents the sensitivity of each point in Field - Of - View (FOV). SRM is known as the geometric sensitivity matrix if the physical factors are ignored. Specific geometry of a detector corresponds to a unique geometric sensitivity matrix in this case. This study aims to a preliminary investigation of relation between PET geometric and characteristic of geometric sensitivity matrix. We obtain the geometric sensitivity matrices of six ring scanner PET system with the same diameter but different crystal numbers and the variance of the matrices’rank with the image size. The results show that the variation of the matrices’rank is the same with the differences of sensitivity in different location in the FOV and tell the area where it can get exact image reconstruction. The study provides an approach for image analysis and can help to optimize detector design for objects of difference sizes.