Uptake patterns of Adult-type Non-Enhanced diffuse gliomas on [¹¹C] methionine positron emission tomography :...

To assess the uptake patterns of adult-type non-enhanced gliomas in the pre-angiogenic phase on [¹¹C] methionine (MET) PET.

We included 52 astrocytoma (Group A), 34 oligodendroglioma (Group O), and 21 glioblastoma (Group G) cases. Regions of interest (ROIs) were defined based on T2-weighted images of high-intensity lesions encompassing tumor volume. The maximum tumor-to-brain ratios (TBR_max) were calculated from PET data. ROIs were internally layered at 5-mm intervals from the tumor surface to assess MET uptake distribution. Moderate (TBR_max ≥1.3) and high (TBR_max ≥2.0) uptakes were classified into three patterns based on the extent and distribution.

TBR_max was significantly lower in Group A than in Groups O and G. TBR_max was more frequently observed in the outermost 0-5 mm layer in all groups. Seventy-three cases with TBR_max ≥1.3 exhibited the whole pattern in 13 (17.8%) and partial or spot patterns in 60 (82.2%) cases; partial or spot pattern cases were most frequently identified as surface/outside patterns (60.3%). Twenty-seven cases with TBR_max ≥2.0 exhibited the whole pattern in 5 (18.5%) and partial or spot patterns in 22 (81.5%) cases; partial or spot pattern cases were identified as central or surface/outside patterns, and none of the cases showed surface/inside patterns, indicating a high-uptake area in the deeper part of the brain.

In non-enhanced gliomas, MET accumulation was concentrated at the periphery of the tumor. Although some cases showed MET uptake throughout the tumor, none showed focal high uptake deep in the brain.