ObjectiveThe 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.MethodsThis 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 18F 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 18F-FDG PET/CT. The image quality was evaluated using the background variability (coefficient of variance, CVphantom and CVliver) and the contrast (CONTHOT and SNR).ResultsIn phantom study, the CVphantom of the LG phantom was higher than that of the NEMA phantom. The PSF decreased the CVphantom of the LG phantom to the NEMA phantom level. The TOF information accelerated the CVphantom plateau earlier. The best relationship between the CVphantom and the CONTHOT was observed for the OSEM + PSF + TOF. In clinical study, the combination of PSF and TOF decreased the CVliver for overweight patients to that for normal weight patients while it increased the SNR similarly between two patient groups.ConclusionThe combination of the PSF and TOF correction improved the image quality of the LG phantom and overweight patients.

The edge artifacts in the PET images reconstructed using the PSF algorithm increased with an increasing SBR. In the small spheres, the edge artifact was observed as a sharp peak at the center of spheres and could result in overestimation.

Amplitude gating PET is considered to be more accurate than phase gating PET for examining unstable respiratory motion patterns, such as those involving a variable amplitude or changing baseline.

Respiratory motion affected the results of the CSH and fractal analyses for the evaluation of the heterogeneity of the PET/CT images. The influence of respiratory motion was considered to vary depending on the object size.

Introduction:The aim of this study was to examine the possibility of using the partial volume correction (PVC) to standardize dual time point [18F] 2-Deoxy-2-fluoro-D-glucose (FDG)-positron emission tomography (PET) studies with two PET scanners. Materials and methods: One hundred and thirteen lesions from 96 breast cancer patients were examined. FDG-PET scans were performed at both 60 and 120 minutes after FDG injection using different PET scanners. The maximum standardized uptake values (SUV max s) were measured at both time points (SUV max 1 and SUV max 2) and the percent change in the SUV max (∆%SUV max ) between the two time points was calculated. PVC was performed using a look-up table generated based on the recovery coefficient curves and point spread function of each scanner. Results: The SUV max 1, the SUV max 2, and the ∆%SUV max were 5.67±4.45, 5.15±4.29, and -9.30%±20.54%, respectively. After PVC, all parameters significantly increased to 10.44±5.55, 10.23±5.77, and -1.15%±21.66%, respectively. In addition, the number of lesions with a positive ∆%SUV max increased after PVC, from 26.5% to 40.7%. Conclusion: PVC of the SUV max is considered to be useful for standardizing dual time point FDG-PET studies in patients with breast cancer performed using different PET scanners. This method is also expected to be useful for standardizing multicenter PET studies.