Improvement in PET/CT image quality in overweight patients with PSF and TOF

Objective The aim of this study was to evaluate the effect of the point spread function (PSF) and time of flight (TOF) on PET/CT images of overweight patients in relation to the iteration number and the acquisition time. Methods This study consisted of a phantom study and a clinical study. The NEMA IEC body phantom and a 40 cm diameter large phantom (LG phantom) simulating an overweight patient were used in this study. Both phantoms were filled with 18 F solution with a sphere to background ratio of 4:1. The PET data were reconstructed with the baseline ordered-subsets expectation maximization (OSEM) algorithm, with the OSEM + PSF model, with the OSEM + TOF model and with the OSEM + PSF + TOF model. The clinical study was a retrospective analysis of 66 patients who underwent 18 F-FDG PET/CT. The image quality was evaluated using the background variability (coefficient of variance, CV phantom and CV liver ) and the contrast (CONT HOT and SNR). Results In phantom study, the CV phantom of the LG phantom was higher than that of the NEMA phantom. The PSF decreased the CV phantom of the LG phantom to the NEMA phantom level. The TOF information accelerated the CV phantom plateau earlier. The best relationship between the CV phantom and the CONT HOT was observed for the OSEM + PSF + TOF. In clinical study, the combination of PSF and TOF decreased the CV liver for overweight patients to that for normal weight patients while it increased the SNR similarly between two patient groups. Conclusion The combination of the PSF and TOF correction improved the image quality of the LG phantom and overweight patients.