Impact of list-mode reconstruction and image-space point spread function correction on PET image contrast and...

We evaluate the effects of list-mode reconstruction and the image-space point spread function (iPSF) on the contrast and quantitative values of positron emission tomography (PET) images using a SiPM-PET/CT system. The evaluation is conducted on an NEMA body phantom and clinical images using a Cartesion Prime SiPM-PET/CT system. The signal-to-background ratio (SBR) of the phantom is set to 2, 4, 6, and 8, and all the PET image data are obtained and reconstructed using 3D-OSEM, time-of-flight, iPSF (-/ +), and a 4-mm Gaussian filter with several iterations. The evaluation criteria include % background variability (N_B,10 mm), % contrast (Q_H,10 mm), iPSF change in Q_H,10 mm (ΔQ_H,10 mm) for edge artifact evaluation, profile curves, visual evaluation of edge artifacts, clinical imaging for the standardized uptake value (SUV) of lung nodules, and SNR_liver. N_B,10 mm demonstrates no significant difference in all SBRs with and without iPSF, whereas Q_H,10 mm is higher based on the SBR with and without iPSF. ΔQ_H,10 mm indicates increased iterations and a larger rate of change (> 5%) for small spheres of < 17 mm. The profile curves portrayed almost real concentrations, except for the 10-mm sphere of SBR2 without iPSF; however, with iPSF, an overshoot was observed in the 13-mm sphere of all SBRs. The degree of overshoot increased with increasing iteration and SBR. Edge artifacts were detected at values ≥ 17-22 mm in SBRs other than SBR2 with iPSF. Irrespective of the nodal size, SUV and SNR_liver improved considerably after iPSF adjustment. Therefore, the effects of list-mode reconstruction and iPSF on PET image contrast were limited, and the overcorrection of the quantitative values was validated using iPSF.