Fig. 1

The spheres in air (diameters in mm: 10, 10, 6, 6, 12, 4, 10, 3, 8, 4, 4, and 6) scanned on a Siemens Biograph 64 Truepoint PET/CT. Two reconstructions of the same PET data are shown. a Without PSF (Iterative3D, 6 iterations, 21 subsets, 2-mm Gaussian filter, 336 × 336 matrix) and b With PSF (TrueX using same reconstruction parameters including PSF). Note that different intensity scales were used on the two images to allow visualization of all spheres (RCs are higher with PSF). Without PSF, the well-known pattern is seen: the RCs drop monotonically as function of sphere diameter. With PSF, the rank order of RCs is: 8, 10, 12, 6, 4, and 3 mm