NIMG-49. VALIDATION OF SIMULTANEOUS PH- AND O2-WEIGHTED MOLECULAR MRI USING 18F-FDG PET, IMMUNOHISTOCHEMISTRY, AND BIOENERGETICS

Abstract

Abstract This study aimed to investigate the potential of a novel MRI metric related to aerobic glycolysis in patients with diffuse gliomas. All subjects (Study I–III; 7, 26, and 11 subjects, respectively) were scanned on 3-T systems and underwent pH-weighted amine chemical exchange saturation transfer spin-and-gradient-echo echoplanar imaging (CEST-SAGE-EPI) or CEST-EPI, and perfusion imaging. Relative oxygen extraction fraction (rOEF) was calculated by dividing hypoxia-sensitive R2’ by normalized relative cerebral blood volume (nrCBV); a novel metric that characterizes glycolytic status (aerobic glycolytic index, AGI) was calculated by dividing amine CEST contrast by rOEF. Patients in Study I were additionally scanned by 18F-fluorodeoxyglucose (FDG)-PET. Stereotactic image-guided biopsies were performed on patients in Study II and III, and samples were analyzed by immunohistochemistry (IHC) and extracellular flux bioenergetic analysis, respectively. Pairwise correlation between MR metrics and standardized uptake value of 18F-FDG, IHC metrics, or indices of cellular metabolism was calculated using Spearman’s correlation analysis. In Study I, AGI showed very strong significant correlation with 18F-FDG uptake in glioma (correlation coefficient ρ = 0.86, P =0.014). In Study II, AGI was significantly correlated with glucose transporter 3 (ρ = 0.71; P = 0.0041) and hexokinase 2 (ρ = 0.73; P = 0.0029) in IDH wild-type glioma, while it was significantly correlated with monocarboxylate transporter 1 (ρ = 0.59; P = 0.0094) in IDH mutant glioma. This result may reflect the different glycolytic statuses of these gliomas; specifically, the rate-limiting steps in glycolysis. In Study III, a strong significant correlation with cellular AGI derived from the bioenergetic analysis was found for AGI derived from MRI (ρ = 0.79, P = .036). In conclusion, AGI derived from MRI was correlated with FDG, IHC measurements, and cellular AGI. Future studies investigating the clinical utility of AGI in prediction and evaluation of treatment effects are warranted.