High-Resolution Mapping of Tumor and Peritumoral Glutamate and Glutamine in Gliomas Using 7-T MRSI

Purpose To evaluate glutamate (Glu) and glutamine (Gln) concentrations in patients with glioma using 7-T MR spectroscopic imaging, identify significant differences in metabolic ratios between tumor and peritumoral regions, and assess associations of Glu and Gln with tumor-associated epilepsy and other tumor characteristics. Materials and Methods This retrospective study included data from patients with gliomas who underwent 7-T MR spectroscopic imaging in a single university hospital between September 2018 and April 2021. Median values for nine metabolic ratios were calculated within the visible tumor and peritumoral shell, and Dice similarity coefficients were used to assess the spatial overlap of elevated metabolic regions between these compartments. Statistical significance between regions of interest and between glioma attributes (eg, isocitrate dehydrogenase status) was assessed. Results Thirty-six patients (median age, 52 years [IQR, 23 years]; 22 male, 14 female) were included in the study. The Glu to total creatine (Glu/tCr) median was significantly higher in the peritumoral volume of interest (median, 1.13) compared with the tumor (median, 0.92; P = .00015) and normal-appearing white matter (NAWM; median, 0.87; P < .00011), while the Gln/tCr median was highest in the tumor (median, 0.77; peritumoral: median, 0.44; P < .00011; NAWM: median, 0.33; P < .00011). Glu to total choline was higher in the peritumoral region as well (median, 3.44; tumoral: median, 2.23; P < .00011; NAWM: median, 2.06; P < .00011). Peritumoral Dice similarity coefficients for Glu/tCr and Gln/tCr hotspots were comparable (0.51 to 0.53). Specific metabolic ratios were significantly different between isocitrate dehydrogenase mutant and wild-type gliomas (eg, tumoral Glu/total N-acetylaspartate [tNAA], P = .0054), oligodendroglioma and astrocytoma (eg, tumoral Gln/tNAA, P = .0033), and oligodendroglioma and glioblastoma (eg, tumoral Glu/tNAA, P = .0034). Conclusion The 7-T MR spectroscopic imaging revealed increased Glu and Gln metabolic ratios within the peritumoral region compared with NAWM of patients with glioma distinct from intratumoral changes. Keywords: Glioma, 7 T, MR Spectroscopic Imaging, MRSI, Infiltration, Iisocitrate Dehydrogenase, IDH Supplemental material is available for this article. © The Author(s) 2025. Published by the Radiological Society of North America under a CC BY 4.0 license.