Aerobic glycolytic imaging of human gliomas using combined pH-, oxygen-, and perfusion-weighted magnetic resonance imaging

Purpose: To quantify abnormal metabolism of diffuse gliomas using aerobic glycolytic imaging and investigate its biological correlation. Methods: All subjects underwent a pH-weighted amine chemical exchange saturation transfer spin-and-gradient echo echoplanar imaging (CEST-SAGE-EPI) and dynamic susceptibility contrast perfusion MRI. Relative oxygen extraction fraction (rOEF) was estimated as the ratio of reversible transverse relaxation rate R-2' to normalized relative cerebral blood volume. An aerobic glycolytic index (AGI) was derived by the ratio of pH-weighted image contrast (MTRasym at 3.0 ppm) to rOEF. AGI was compared between different tumor types (N = 51, 30 IDH mutant and 21 IDH wild type). Metabolic MR parameters were correlated with F-18-FDG uptake (N = 8, IDH wild type glioblastoma), expression of key glycolytic proteins using immunohistochemistry (N = 38 samples, 21 from IDH mutant and 17 from IDH wild type), and bioenergetics analysis on purified tumor cells (N = 7, IDH wild-type high grade). Results: AGI was significantly lower in IDH mutant than wild-type gliomas (0.48 +/- 0.48 vs. 0.70 +/- 0.48; P = 0.03). AGI was strongly correlated with F-18-FDG uptake both in non-enhancing tumor (Spearman, rho = 0.81; P = 0.01) and enhancing tumor (rho = 0.81; P = 0.01). AGI was significantly correlated with glucose transporter 3 (rho = 0.71; P = 0.004) and hexokinase 2 (rho = 0.73; P = 0.003) in IDH wild-type glioma, and monocarboxylate transporter 1 (rho = 0.59; P = 0.009) in IDH mutant glioma. Additionally, a significant correlation was found between AGI derived from bioenergetics analysis and that estimated from MRI (rho = 0.79; P = 0.04). Conclusion: AGI derived from molecular MRI was correlated with glucose uptake (F-18-FDG and glucose transporter 3/hexokinase 2) and cellular AGI in IDH wild-type gliomas, whereas AGI in IDH mutant gliomas appeared associated with monocarboxylate transporter density.

Automated summary

The study quantified abnormal metabolism of diffuse gliomas using aerobic glycolytic imaging, finding significantly lower aerobic glycolytic index (AGI) in IDH mutant gliomas than wild-type, and strong correlations between AGI and glucose metabolism and key glycolytic protein expression.