10182- NI-15 ANALYSIS OF THE HIGH UPTAKE PATTERN ON 11C-METHIONINE-PET IN ADULT NON-ENHANCED GLIOMAS

Abstract The uptake pattern of adult non-enhanced gliomas on 11C-methionine (MET) positron emission tomography (PET) was detected in each type of tumor. This study included 52 cases of astrocytoma (A group), 34 cases of oligodendroglioma (O group), and 21 cases of glioblastoma (G group). Region of interest (ROI) was defined based on T2-weighted imaging high intensity lesions, encompassing each tumor volume. Maximum or mean standardized uptake value (SUV) and tumor/normal frontal cortex SUV ratio (TNR) were calculated from PET data. ROIs were layered internally by 5mm intervals from the tumor edge to assess the MET distribution. A high uptake pattern, meaning a TNR of 2.0 or higher, was classified by three observers. TNR, maximum, and mean SUV of the tumor were significantly lower in the A group than in the O and G groups. Although total tumor volume did not differ among groups, there were very strong correlations between increasing TNR and volume with TNR of 1.3 or higher and 2.0 or higher in the A and the O group (r=0.73-0.93); relatively poor relation in the G group (r=0.53-0.70). Maximum SUV was predominantly observed at the outermost layers across all groups, with the O group frequently exhibiting it at the layers of 5-10mm from the tumor edge (40.6%). Among 28 cases with a TNR of 2.0 or higher, the extent of high uptake area was classified into whole patterns in 5 cases and partial or spot patterns in 23 cases. The high MET distributions of the cases with partial or spot patterns were all identified as central or surface/outside patterns, and there were no cases with surface/inside pattern. The characteristic uptake patterns for each tumor subtype may help plan the surgical strategy for gliomas.