10188-NI-4 Correlation between 11C-Methionine PET and the glymphatic system in gliomas

Abstract Background The aim of this study was to analyze the correlation between 11C-Methionine (MET)-PET and glymphatic system (GS) in glioma. [Methods] Between April 2023 and February 2025, 22 primary preoperative adult glioma patients (mean age 51.5±18. 7years, 12 men; 11 glioblastoma, isocitrate dehydrogenase (IDH)-wildtype (G), 6 astrocytoma, IDH-mutant (A), 5 oligodendroglioma, IDH-mutant and 1p/19q-codeleted (O)) performed by MRI and MET-PET at the Chubu Medical Care Center who could be measured the ipsilateral analysis along the perivascular space (ALPS) index were retrospectively included. The ALPS index was calculated by manually setting a region of interest at the level of the lateral ventricle body, where projection and association fibers are clearly identified, using fractional anisotropy (FA) map. The tumor-normal brain standardized uptake value (SUV) ratio (T/N ratio) was calculated from MET-PET. Results There was a significant inverse correlation between T/N ratio and the ALPS index (r=-0.56, p = 0.0073), but only glioblastoma showed (G: r=-0.61, p = 0.0047; A: r = 0.19, p = 0.704; O: r = 0.50, p = 0.382). IDH-wildtype (1.447±0.184) was significantly lower than IDH-mutant (1.787±0.205) (p = 0.0013). No significant correlation was showed between accumulation volume with T/N ratio ≥ 1.5, contrast volume, and edema volume, but there was a moderate inverse correlation for accumulation volume (r=-0.51, p = 0.112) and contrast volume (r=-0.44, p = 0.171). Discussion The inverse correlation between T/N ratio and the ALPS index was showed only in glioblastoma. This may indicate particularly highly invasive compared to astrocytoma and oligodendroglioma, and relationship to physical pressure due to high cell density and structural destruction of the perivascular space.