Fig. 5

RCs (%) as a function of voxel noise (%) for all sphere sizes for a high and low count frame for the contrast phantom (PET/MR (a), HRRT (b)). The high count frame corresponds to ~ 135 million prompts within the frame, the low count frame to ~ 12 million prompts. Note the difference in x-axis limits. Each point represents an OSEM iteration, and the number of iterations increases from left to right. PET/MR data were reconstructed with TOF + PSF + filter; HRRT data were reconstructed with filter only (standard in-house reconstruction for human data). High count data were analyzed based on a single realization while low count data were based on five replicates. Solid lines represent the hot spheres, dotted lines the cold spheres