Computing System Matrix for OSEM and MLEM Iterative Image Reconstruction Algorithms

This MATLAB program implements a function Generate_SystemMatrix that computes the system matrix for OSEM (Ordered Subsets Expectation Maximization) and MLEM (Maximum Likelihood Expectation Maximization) iterative image reconstruction algorithms. The function Generate_SystemMatrix(pixel) takes the image dimension (typically 64, 128, or 256) as input parameter - larger pixel values result in slower computation. The diedai-test file demonstrates a basic MLEM reconstruction implementation, which requires loading the SystemMatrix generated by Generate_SystemMatrix(128). Note: when running diedai-test, ensure the generated system matrix is saved as "SystemMatrix" to avoid errors.