Reconstructed spatial resolution and contrast recovery with Bayesian penalized likelihood reconstruction (Q.Clear) for FDG-PET compared to time-of-flight (TOF) with point spread function (PSF)

摘要

Abstract BackgroundBayesian penalized likelihood reconstruction for PET (e.g., GE Q.Clear) aims at improving convergence of lesion activity while ensuring sufficient signal-to-noise ratio (SNR). This study evaluated reconstructed spatial resolution, maximum/peak contrast recovery (CRmax/CRpeak) and SNR of Q.Clear compared to time-of-flight (TOF) OSEM with and without point spread function (PSF) modeling.MethodsThe NEMA IEC Body phantom was scanned five times (3 min scan duration, 30 min between scans, background, 1.5–3.9 kBq/ml F18) with a GE Discovery MI PET/CT (3-ring detector) with spheres filled with 8-, 4-, or 2-fold the background activity concentration (SBR 8:1, 4:1, 2:1). Reconstruction included Q.Clear (beta, 150/300/450), “PSF+TOFsub4/16/sub” (iterations, 4; subsets, 16; in-plane filter, 2.0 mm), “OSEM+TOFsub4/16/sub” (identical parameters), “PSF+TOFsub2/17/sub” (2 it, 17 ss, 2.0 mm filter), “OSEM+TOFsub2/17/sub” (identical), “PSF+TOFsub4/8/sub” (4 it, 8 ss, 6.4 mm), and “OSEM+TOFsub2/8/sub” (2 it, 8 ss, 6.4 mm). Spatial resolution was derived from 3D sphere activity profiles. RC as (sphere activity concentration [AC]/true AC). SNR as (background mean AC/background AC standard deviation).ResultsSpatial resolution of Q.Clearsub150/sub was significantly better than all conventional algorithms at SBR 8:1 and 4:1 (Wilcoxon, each p 0.05). At SBR 4:1 and 2:1, the spatial resolution of Q.Clearsub300/450/sub was similar or inferior to PSF+TOFsub4/16/sub and OSEM+TOFsub4/16/sub. Small sphere CRpeak generally underestimated true AC, and it was similar for Q.Clearsub150/300/450/sub as with PSF+TOFsub4/16/sub or PSF+TOFsub2/17/sub (i.e., relative differences ?10%). Q.Clear provided similar or higher CRpeak as OSEM+TOFsub4/16/sub and OSEM+TOFsub2/17/sub resulting in a consistently better tradeoff between CRpeak and SNR with Q.Clear. Compared to PSF+TOFsub4/8/sub/OSEM+TOFsub2/8/sub, Q.Clearsub150/300/450/sub showed lower SNR but higher CRpeak.ConclusionsQ.Clear consistently improved reconstructed spatial resolution at high and medium SBR compared to PSF+TOF and OSEM+TOF, but only with beta = 150. However, this is at the cost of inferior SNR with Q.Clearsub150/sub compared to Q.Clearsub300/450/sub and PSF+TOFsub4/16/sub/PSF+TOFsub2/17/sub while CRpeak for the small spheres did not improve considerably. This suggests that Q.Clearsub300/450/sub may be advantageous for the 3-ring detector configuration because the tradeoff between CR and SNR with Q.Clearsub300/450/sub was superior to PSF+TOFsub4/16/sub, OSEM+TOFsub4/16/sub, and OSEM+TOFsub2/17/sub. However, it requires validation by systematic evaluation in patients at different activity and acquisition protocols.