Improved Absolute Quantification using Bayesian Penalized Likelihood Reconstruction on a Digital PET/CT – Towards True Uptake Measurement

Abstract

Background To evaluate the quantification accuracy, we measured the recovery coefficient (RC) and contrast recovery (CR) in a phantom study and used it as a guide in clinical evaluation about digital positron emission tomography -computed tomography (PET/CT). Methods The RC and CR of the PET images reconstructed with 4 different methods [ordered subsets expectation maximazation (OSEM), time of flight(TOF), TOF-point spread function (PSF), bayesian penalized likelihood (BPL)] were measured in the phantom study. And, SUVmax and SUVmean (the maximum and mean of the standardized uptake values, SUVs) of 75 small pulmonary nodules (sub-centimeter group: <10 mm and medium size group: 10 - 25 mm) from 26 patients were measured with those methods. For lesions smaller than 3 times of the spatial resolution, partial-volume-effect correction (PVC) based on RC values was performed. Results BPL enables higher RC and CR values, which can improve quantification accuracy compared with other methods (P < 0.05), except for the RC of 37 mm sphere (P > 0.05). The SUVs of sub-centimeter fludeoxyglucose (FDG)-avid pulmonary nodules with BPL illustrated highly significant difference from those reconstructed with other algorithms (P<0.001). However, reconstruction algorithms had less impact on SUVs measured in medium group (P>0.05). With the PVC, highly significant difference (P<0.001) still existed in the SUVmean measured on BPL compared with those measured on the other 3 algorithms, although PVC had the least effect on BPL. Conclusions BPL on the digital PET/CT demonstrated improved quantification accuracy. For small pulmonary nodules, PVC is important.

Moving the goalposts while scoring―the dilemma posed by new PET technologies

“…• Image noise [75][76][77][78] • Subjective image quality [73,77,[79][80][81][82][83][84] • Prediction of subjective image quality from objectified measures [85] • Lesion SUV [75,86,87] • Conspicuity of pulmonary lesions [69,77,86] • Detection rate in pulmonary lesions [88] • Lesion detectability in pelvic PSMA PET/MRI at low activity [89] • Detection rate of lymph nodes in fluorocholine PET [90] • Normal databases for brain PET in neurodegenerative disease [91,92] • Acquisition time reduction [81,84,89,93] Level 2:…”

Influences on PET Quantification and Interpretation

“…Although this effect can lead to overestimation of the true activity in larger lesions if the SUVmax is used [101], the increase in CR may be especially prominent in microspheres with diameters <10 mm, in which conventional algorithms usually underestimate the true activity substantially [109]. This has been confirmed by increasing lesion SUVmax compared with TOF and PSF reconstruction, particularly in small pulmonary lesions [110,111]. However, this difference is directly dependent on the user-defined penalization factor beta during PL reconstruction, and at beta values of 300 to 600, which have been rated as optimal for visual reading of [ 18 F]FDG-PET images by human readers [107,112,113], inter-method SUV differences may no longer be significant [41,108,111].…”