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ORIGINAL RESEARCH article

Front. Oncol.

Sec. Cancer Imaging and Image-directed Interventions

Volume 15 - 2025 | doi: 10.3389/fonc.2025.1597919

This article is part of the Research TopicAdvances in Image Reconstruction for Nuclear Medicine TomographyView all 5 articles

Comparative Evaluation of Ordered Subset Expectation Maximization and Bayesian Penalized Likelihood Algorithms for PET/CT Image Reconstruction in Various Malignancies Using 18F-FDG and 68Ga-PSMA-11 Tracers

Provisionally accepted
Arvin  NaeimiArvin Naeimi1,2Sara  HarsiniSara Harsini3Ramin  Akbarian AghdamRamin Akbarian Aghdam4Ran  KleinRan Klein5Farzad  ABBASPOUR-RADDAKHELIFarzad ABBASPOUR-RADDAKHELI5,6*
  • 1Department of Radiology, McGill University Health Center, McGill University, montreal, Canada
  • 2Student Research Committee, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran
  • 3BC Cancer Agency, Vancouver, Canada
  • 4Division of Nuclear Medicine, Department of Medicine, The Ottawa Hospital and University of Ottawa, Canada., Ottawa, Canada
  • 5Department of Nuclear Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada
  • 6Division of Nuclear Medicine, Department of Radiology, McGill University Health Center, McGill University, Montreal, Canada

The final, formatted version of the article will be published soon.

Purpose: This study compares the Ordered Subset Expectation Maximization (OSEM) and Bayesian Penalized Likelihood (BPL) algorithms for Positron Emission Tomography/Computed Tomography (PET/CT) image reconstruction using 18F- fluorodeoxyglucose (FDG) and ⁶⁸Ga-labeled Prostate-Specific Membrane Antigen(⁶⁸Ga-PSMA-11) tracers. Methods: A retrospective analysis was conducted on 33 patients with various malignancies, including 25 undergoing 18F-FDG PET/CT scans and 8 undergoing 68Ga-PSMA-11 PET/CT scans. Scans were reconstructed using both OSEM and BPL algorithms, evaluating key metrics such as Standardized Uptake Value (SUV)max, SUVpeak, background SUV, and tumor-to-background ratio (TBR). Results: Thirty-three patients (mean age: 67.53±11.78 years) with 100 lesions (80 FDG, 20 PSMA) were analyzed. In the FDG group, significant differences were observed in lesion SUVpeak, liver SUVpeak, SD of liver SUVmean, bladder SUVmean, SD of bladder SUVmean, and TBR, with BPL generally producing higher values except for liver SUVpeak, SD of liver SUVmean, and SD of bladder SUVmean. In the PSMA group, BPL enhanced most metrics except for the SD of liver SUVmean and the SD of bladder SUVmean. While strong linear correlations between BPL and OSEM metrics were observed (Pearson r>0.85 for most parameters), Bland-Altman analysis revealed wide limits of agreement, particularly for TBR in the PSMA group (-13.00 to 23.89), indicating substantial variability in absolute values between methods. Assessment of the relationship between lesion volume and SUVmax differences(BPL–OSEM) revealed a weak, non-significant negative correlation in the total cohort(r = – 0.14, p = 0.16) and in the FDG subgroup(r= – 0.14, p = 0.24). Conclusion: Both reconstruction methods demonstrate clinical utility, with BPL producing statistically higher values for several quantitative metrics, such as SUVmax and TBR, without markedly improving lesion detectability. While strong correlations were observed between BPL and OSEM values, the wide limits of agreement, particularly for TBR in PSMA imaging, suggest these methods may not be directly interchangeable in longitudinal studies. Harmonization strategies may help reduce inter-method variability and improve scan comparability in longitudinal or multicenter settings. Prospective approaches, such as reconstruction-specific reference ranges or scaling factors, could further support harmonization efforts in clinical trials. For longitudinal monitoring, consistent use of the same reconstruction method is recommended to ensure reliable quantification.

Keywords: Bayesian Penalized Likelihood, BPL, ordered subset expectation maximization, OsEm, image reconstruction, Positron emission tomography-computed tomography, PET/CT

Received: 21 Mar 2025; Accepted: 30 Jul 2025.

Copyright: © 2025 Naeimi, Harsini, Akbarian Aghdam, Klein and ABBASPOUR-RADDAKHELI. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Farzad ABBASPOUR-RADDAKHELI, Division of Nuclear Medicine, Department of Radiology, McGill University Health Center, McGill University, Montreal, Canada

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