Comparison of 11C-Methionine PET and 18F-FDG PET in Patients with Primary Central Nervous System Lymphoma

Abstract

2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) positron emission tomography (PET) has been used as a promising tool to diagnose primary central nervous system (CNS) lymphoma because the tumor shows very high FDG accumulation. Although (11)C-methionine (MET) PET has been reported to be useful for evaluating various brain tumors, the role of MET PET in CNS lymphoma is unclear. We compared the uptake of MET and FDG in patients with CNS lymphoma. Thirteen immunocompetent patients with CNS lymphoma were examined. All patients underwent PET with MET (15 min p.i.) and FDG (60 min p.i.). PET results were evaluated by visual and semi-quantitative analysis. For semi-quantitative analysis, the standardized uptake value (SUV) and tumor to contralateral normal brain tissue (T/N) ratio were determined by region-of-interest analysis. For detection of CNS lymphoma, sensitivity of PET using both MET and FDG was 100%. The mean (±SD) value of SUV in the contralateral normal brain tissue using MET (1.43 ± 0.21) was significantly lower than that using FDG (5.58 ± 1.79; p < 0.002). The mean (±SD) value of SUV in the CNS lymphoma using MET (4.27 ± 1.91) was significantly lower than that of FDG (13.94 ± 5.65; p < 0.002). There were no significant differences between mean (±SD) T/N ratios using MET PET (3.00 ± 1.26) and FDG PET (2.74 ± 1.25). There was no significant difference between T/N ratios using MET PET and FDG PET, although uptake of MET in CNS lymphoma was significantly lower than that of FDG. MET PET showed as high a sensitivity as FDG PET for the detection of primary lesions in patients with CNS lymphoma.