Polygonal pixel grid based PET image reconstruction algorithm: Development, application and performance comparison

System matrix works as an association between image and detected data. Accurate expression of the system matrix is a key component during PET image reconstruction. However, with numerous Line-of-Responses (LORs) detected in modern 3D PET scanner, the huge storage size of a full system matrix increases computational burden. To solve this essential issue, we designed a rotationally symmetric polygonal pixel grid with fan-shaped segments in the image domain to efficiently compress the matrix with geometrical symmetries. This idea mainly came from the polygonal geometry of detector rings in most PET system.