Practical considerations of the Wiener filtering technique on projection data for PET

Wiener filtering (WF) attempts to recover a blurred object by incorporating the system modulation transfer function (MTF) and its noise characteristics. Although it has been widely studied in SPECT, few studies have been reported in PET. In this investigation, first, the authors discuss some factors in PET which affect the Poisson nature of the noise on data, such as the axial normalization, detector efficiency correction and randoms correction. Then they propose a modified WF which compensates for the above factors. The modified WF provides a more accurate noise estimation method and a simple way to optimize the filter performance. Finally the authors apply the modified WF to projection data of the volumetric UGM PENN-PET 240H scanner in both transaxial and axial directions. A cold-hot sphere phantom and 3D brain phantom are used for evaluation. The modified WF is compared to the conventional WFs. The authors´ results indicate that 1) the conventional WFs may overestimate the noise power spectrum; 2) although the WFs are sensitive to the image statistics their overall performances are still quantitatively much better than without any restoration filtering; 3) in general, filtering in both axial and transaxial directions is better than the transaxial filtering only, but its superiority is more obvious when applied to scans with low image statistics; 4) In general, the Wiener filtering improves the PET image contrast and count recovery