Multi-Resolution Imaging for Total-body PET

Based on the two-meter-long total-body PET scanner, the multi-resolution reconstruction algorithm aims to reconstruct multiple ROI images with different parameters (voxel size, iteration number and post-filter strength, etc.) simultaneously. The proposed algorithm is an extension of the conventional LOR-OSEM algorithm. Instead of representing the whole image with only one image matrix, the proposed method uses a set of intermediate matrixes to store the whole image. Each matrix is for one part of the whole image. One LOR may pass through multiple matrixes, and the contributions of voxels in each matrix are calculated individually during the forward and backward projection process. Furthermore, parallel ray-tracing algorithm is developed for efficient GPU implementation. The proposed algorithm was validated using a 2D digit phantom and real data collected from a commercial PET/CT scanner with the axial field of view 300mm.