Impact of [¹¹C]methionine PET with Bayesian penalized likelihood reconstruction on glioma grades based on new WHO 2021 classification

Objective The uptake of [C-11]methionine in positron emission tomography (PET) imaging overlapped in earlier images of tumors. Bayesian penalized likelihood (BPL) reconstruction increases the quantitative values of tumors compared with conventional ordered subset-expectation maximization (OSEM). The present study aimed to grade glioma malignancy based on the new WHO 2021 classification using [C-11]methionine PET images reconstructed using BPL. Methods We categorized 32 gliomas in 28 patients as grades 2/3 (n = 15) and 4 (n = 17) based on the WHO 2021 classification. All [C-11]methionine images were reconstructed using OSEM + time-of-flight (TOF) and BPL + TOF (beta = 200). Maximum standardized uptake value (SUVmax) and tumor-to-normal tissue ratio (T/N-max) were measured at each lesion. Results The mean SUVmax was 4.65 and 4.93 in grade 2/3 and 6.38 and 7.11 in grade 4, and the mean T/N-max was 7.08 and 7.22 in grade 2/3 and 9.30 and 10.19 in grade 4 for OSEM and BPL, respectively. The BPL significantly increased these values in grade 4 gliomas. The area under the receiver operator characteristic (ROC) curve (AUC) for SUVmax was the highest (0.792) using BPL. Conclusions The BPL increased mean SUVmax and mean T/N-max in lesions with higher contrast such as grade 4 glioma. The discrimination power between grades 2/3 and 4 in SUVmax was also increased using [C-11]methionine PET images reconstructed with BPL.