The visual assessment showed no significant difference from quantitative assessment of MET-PET with a relevant cut-off value for the differentiation of recurrent brain tumors from radiation-induced necrosis 1).
Mitamura et al., evaluated the uptake of 2-deoxy-18F-Fludeoxyglucose (FDG) and L-[methyl-11C]-methionine (MET) in patients with newly diagnosed intracranial meningiomas and correlated the results with tumor proliferation.
Data from 22 patients with newly diagnosed intracranial meningioma (12 grade I and 10 grade II) who underwent both FDG and MET brain PET/CT studies were retrospectively analyzed. The PET images were evaluated by a qualitative method and semiquantitative analysis using standardized uptake value (SUV) (SUVmax and SUVpeak) and tumor-to-reference tissue ratio (Tmax/N ratio and Tpeak/N ratio). Proliferative activity as indicated by the Ki-67 index was estimated in tissue specimens.
MET PET/CT showed a higher detection rate of meningioma than did FDG PET/CT (100 vs. 46%, respectively). The Tmax/N ratio and Tpeak/N ratio on MET PET/CT were significantly higher than those on FDG PET/CT (p < 0.001 and p < 0.001, respectively). There was a significant difference between grades I and II with respect to FDG SUVmax (p = 0.003), FDG SUVpeak (p = 0.003), FDG Tmax/N ratio (p = 0.02), FDG Tpeak/N ratio (p = 0.006), MET SUVmax (p = 0.002), MET SUVpeak (p = 0.002), MET Tmax/N ratio (p = 0.002), and MET Tpeak/N ratio (p = 0.002). There was a significant correlation between Ki-67 index and FDG PET/CT for SUVmax (p = 0.02), SUVpeak (p = 0.005), and Tpeak/N ratio (p = 0.05) and between Ki-67 index and MET PET/CT for SUVmax (p = 0.004), SUVpeak (p = 0.007), Tmax/N ratio (p = 0.002), and Tpeak/N ratio (p = 0.004).
MET PET/CT showed a high sensitivity compared with FDG PET/CT for detection of newly diagnosed WHO grades I and II intracranial meningiomas. Both FDG and MET uptake were found to be useful for evaluating tumor proliferation in meningiomas 2).
MET-PET is a sensitive technique for diagnosing persistent acromegaly and its coregistration with 3T MRI has demonstrated a better definition of the interface, extension and location of the lesion in the management of active postoperative acromegaly 3).