Absolute Quantification of Brain Deuterium Metabolic Imaging in Healthy Volunteers and Glioblastoma Patients at 7T.

Abstract

PURPOSE: We present a method for absolute quantification of deuterated metabolites in vivo at 7T. We describe acquisition protocols and an analysis pipeline compatible with 7T Terra MRIs. We apply them using a 2H/1H receive array in healthy volunteers and glioblastoma patients. METHODS: B1 +/B1 - maps from multiple CSI scans in a uniform phantom were used to derive calibrated coil weights for absolute quantification. We validated this in phantoms with known deuterated compounds. 2H MRSI was performed in twelve healthy volunteers (two post-[6,6-2H2]-glucose) and five treatment-naive glioblastoma patients (all post-[6,6-2H2]-glucose). Spectra were fitted with OXSA. We compared Glx/Lac between tumor and normal-appearing brain using linear mixed-effects models. RESULTS: Measured B1 + maps were 0.82 ± 0.19 μT/√W across the whole phantom. Natural abundance deuterium in water was 8.96 ± 0.7 mmol/L. Absolute maps of HDO, Glc, Glx, and Lac were acquired following [6,6-2H2]glucose. Rate maps showed higher Lac production in tumors (2.3 μmol/L/min, SE = 0.87) compared with normal-appearing regions (1.0 μmol/L/min, SE = 0.36; p < 0.01) and healthy brain (0.5 μmol/L/min, SE = 0.17; p < 0.01). Glx production was lower in tumors (3.8 μmol/L/min, SE = 0.44) relative to normal-appearing contralateral regions (6.0 μmol/L/min, SE = 0.36; p < 0.001) and healthy brain (9.2 μmol/L/min, SE = 0.61; p < 0.001). CONCLUSION: We demonstrate robust absolute quantification for human 7T DMI. Glioblastoma tumors showed elevated Lac and reduced Glx labeling relative to normal brain, with inter-patient heterogeneity consistent with an existence of different metabolic subtypes.