Metabolic assessment of intracranial tuberculomas using 11C-methionine and F-FDG PET/CT

BACKGROUND: F-fluorodeoxyglucose ( F-FDG) has limited specificity in the evaluation of intracranial lesions as it is taken up by inflammatory and granulomatous lesions as well. C-methionine is known to have a higher specificity in tumor detection, delineation, and differentiation of benign from malignant lesions. However, its uptake in granulomatous lesions remains unclarified. OBJECTIVE: The aim of this study was to explore the value of C-methionine PET/CT and F-FDG in the evaluation of intracranial tuberculomas. METHODS: C-methionine PET/CT followed by F-FDG PET/CT study was performed on 12 patients with intracranial tuberculomas. The diagnosis was confirmed for all cases on histopathological evaluation and/or follow-up. Quantitative analysis was performed for all cases by measuring the lesion-to-normal gray matter uptake ratio. RESULTS: A high lesion-to-normal gray matter uptake ratio was observed on both C-methionine (1.8±0.38) and F-FDG scans (1.64±0.26) in all newly diagnosed cases. Lesion detection and delineation was superior on C-methionine PET/CT. In addition, C-methionine appeared to be a more sensitive indicator for assessing early therapeutic response and incomplete therapeutic response in intracranial tuberculomas. There was complete concordance in the number and sites of lesions detected on C-methionine PET/CT and radiological imaging modalities (namely, CT and MRI). CONCLUSION: This preliminary study suggests that in newly diagnosed, untreated intracranial tuberculomas, C-methionine, like F-FDG, may have limited specificity in distinguishing it from a neoplastic lesion. However, it may play an important role in assessing the response to antitubercular treatment. Further studies are warranted to explore the potential of C-methionine in this regard. Copyright © Lippincott Williams & Wilkins.