{"title":"Methionine PET Findings in the Diagnosis of Brain Tumors and Non-Tumorous Mass Lesions: A Single-Center Report on 426 Cases.","authors":"Yoshiki Shiba, Kosuke Aoki, Fumiharu Ohka, Shoichi Deguchi, Junya Yamaguchi, Hiroki Shimizu, Sachi Maeda, Yuhei Takido, Ryo Yamamoto, Akihiro Nakamura, Ryuta Saito","doi":"10.3174/ajnr.A8871","DOIUrl":null,"url":null,"abstract":"<p><strong>Background and purpose: </strong>Differentiating between a brain tumor and a non-tumorous lesion remains a significant diagnostic challenge, particularly when conventional imaging modalities such as CT and MRI provide inconclusive results. While MET-PET has shown potential in neuro-oncology, its diagnostic performance across a broad spectrum of brain pathologies has not been comprehensively evaluated. This study therefore assessed the sensitivity, specificity, and uptake patterns of MET-PET in a large cohort of brain lesions.</p><p><strong>Materials and methods: </strong>This single-center retrospective study analyzed 426 consecutive patients with undiagnosed brain lesions who underwent MET-PET imaging between January 2019 and May 2024. TNRs were calculated using a threshold of 1.5 for positive findings. Histological diagnoses were established based on the World Health Organization 2021 criteria, IDH mutation status and 1p/19q-codeletion.</p><p><strong>Results: </strong>Among the cohort, 342 cases (67.8%) were confirmed as having tumorous lesions, 76 (17.8%) as having non-tumorous lesions, and 61 (14.3%) remained undiagnosed. MET-PET exhibited high sensitivity (86.2%) but limited specificity (47.4%) for tumor detection. In multiple sclerosis cases, MET-PET showed a remarkably high positivity rate (n = 10/12) that was significantly higher than for other non-tumorous lesions. In terms of tumors, IDH-wildtype glioblastomas had significantly higher TNRs compared to IDH-mutant gliomas, while oligodendrogliomas had higher TNRs compared to astrocytomas, in which TNR values correlated with tumor grade.</p><p><strong>Conclusions: </strong>MET-PET demonstrated robust sensitivity for brain tumor detection, but was limited by low specificity due to false positives in inflammatory conditions and false negatives for low-grade tumors. These findings imply the importance of integrating MET-PET with other imaging modalities to enhance diagnostic accuracy.</p><p><strong>Abbreviations: </strong>MET-PET＝<sup>11</sup>C-methionine positron emission tomography; TNR＝Tumor/normal region ratio; IDH＝isocitrate dehydrogenase.</p>","PeriodicalId":93863,"journal":{"name":"AJNR. American journal of neuroradiology","volume":" ","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"AJNR. American journal of neuroradiology","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.3174/ajnr.A8871","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
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Abstract
Background and purpose: Differentiating between a brain tumor and a non-tumorous lesion remains a significant diagnostic challenge, particularly when conventional imaging modalities such as CT and MRI provide inconclusive results. While MET-PET has shown potential in neuro-oncology, its diagnostic performance across a broad spectrum of brain pathologies has not been comprehensively evaluated. This study therefore assessed the sensitivity, specificity, and uptake patterns of MET-PET in a large cohort of brain lesions.
Materials and methods: This single-center retrospective study analyzed 426 consecutive patients with undiagnosed brain lesions who underwent MET-PET imaging between January 2019 and May 2024. TNRs were calculated using a threshold of 1.5 for positive findings. Histological diagnoses were established based on the World Health Organization 2021 criteria, IDH mutation status and 1p/19q-codeletion.
Results: Among the cohort, 342 cases (67.8%) were confirmed as having tumorous lesions, 76 (17.8%) as having non-tumorous lesions, and 61 (14.3%) remained undiagnosed. MET-PET exhibited high sensitivity (86.2%) but limited specificity (47.4%) for tumor detection. In multiple sclerosis cases, MET-PET showed a remarkably high positivity rate (n = 10/12) that was significantly higher than for other non-tumorous lesions. In terms of tumors, IDH-wildtype glioblastomas had significantly higher TNRs compared to IDH-mutant gliomas, while oligodendrogliomas had higher TNRs compared to astrocytomas, in which TNR values correlated with tumor grade.
Conclusions: MET-PET demonstrated robust sensitivity for brain tumor detection, but was limited by low specificity due to false positives in inflammatory conditions and false negatives for low-grade tumors. These findings imply the importance of integrating MET-PET with other imaging modalities to enhance diagnostic accuracy.
Abbreviations: MET-PET＝11C-methionine positron emission tomography; TNR＝Tumor/normal region ratio; IDH＝isocitrate dehydrogenase.
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