PET/CT findings for tumors in the base of the skull: comparison of 18 F-FDG with 11 C-methionine

Abstract

Background Positron emission tomography/computed tomography (PET/CT) using 18 F-fluorodeoxyglucose (FDG) has been used to characterize various malignancies. There are few reports regarding the use of 11 C-methionine (MET)-PET/CT to characterize tumors in the skull base. Purpose To compare MET-PET/CT with FDG-PET/CT in cases of tumors of the skull base. Material and Methods Both MET-PET/CT and FDG-PET/CT were performed in 27 patients with tumors of the skull base. In all cases, pathology was determined by surgery or biopsy. The images were visually and independently reviewed by two reviewers. For qualitative analysis, the inter-rater agreement between two reviewers was measured. For semi-quantitative evaluation, the tumor-to-normal brain uptake ratios (T/N ratios) were calculated by dividing the maximum of standardized uptake value (SUVmax) for the tumor by the SUVmax of the normal contra-lateral cerebellar hemisphere. Difference in T/N ratios between FDG-PET/CT and MET-PET/CT was analyzed for statistical significance. Results On qualitative evaluation, the inter-rater agreement of MET-PET/CT was superior than that of FDG-PET/CT. MET uptake was interpreted as positive in every tumor by both reviewers. MET-PET/CT had a significantly higher T/N ratio than FDG-PET/CT (2.96 ± 1.25 vs. 1.02 ± 0.54, respectively; P < 0.001). Conclusion MET-PET/CT showed superior inter-rater agreement and had higher uptake for tumors at the skull base than FDG-PET/CT. The present study suggests that MET-PET/CT has superior potential for imaging of tumors of the skull base.