Influence of Reconstruction FOV and Matrix Size on the Quantitative Accuracy of FDG-PET: Comparison between OSEM and Bayesian Penalized Likelihood

Abstract

Field of view (FOV) and matrix size determine the pixel size of positron emission tomography (PET) images; however, the effect of any variation in these parameters on the quantitative accuracy is unclear. The FOV and matrix size of PET images are adjusted as per each clinical objective. Therefore, this study aimed to evaluate the quantitative accuracy of PET images under different FOV and matrix sizes. A National Electrical Manufacturers Association (NEMA) body phantom set was filled with 18F-FDG solution, and imaging data were acquired for 30 min. Images were reconstructed using ordered subset expectation maximization (OSEM) and Bayesian penalized likelihood (BPL), both of which were combined with point spread function (PSF) and time of flight (TOF). In each reconstruction method, the image parameters were set to the following: FOV, 20-70 cm; matrix size, 128×128 to 384×384; and pixel size, 1-3 mm. The images were evaluated by physical assessment of the recovery coefficient (RC) and maximum standardized uptake value ratio (SUVmax ratio). The RC of OSEM images was not affected by changes in FOV, whereas the RC of BPL images decreased in small spheres, when FOV was 20 and 30 cm. The SUVmax ratio of the OSEM images was not affected by the difference in pixel size. However, the SUVmax ratio of BPL images degraded in the 1-mm pixel size; this influence was observed only when the FOV was changed.Conclusion: BPL images reconstructed using a small FOV might degrade the quantitative accuracy of small spheres.