Absolute quantification of brain deuterium metabolic imaging in healthy volunteers and glioblastoma patients at 7T

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, and apply these 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, validated in phantoms with known deuterated compounds. 2H MRSI was performed in twelve healthy volunteers (two post-[6,6-2H2]-glucose) and five glioblastoma patients (all post-[6,6-2H2]-glucose). Spectra were fitted with OXSA, and Glx/Lac compared between tumor and normal-appearing brain using linear mixed-effects models. Results: Measured B1+ maps were 0.82 +/- 0.19 uT/sqrt(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 umol/L/min, SE = 0.87) compared with normal-appearing regions (1.0 umol/L/min, SE = 0.36; p < 0.01) and healthy brain (0.5 umol/L/min, SE = 0.17; p < 0.01). Glx production was lower in tumors (3.8 umol/L/min, SE = 0.44) relative to normal-appearing regions (6.0 umol/L/min, SE = 0.36; p < 0.001) and healthy brain (9.2 umol/L/min, SE = 0.61; p < 0.001). Conclusion: We demonstrate robust absolute quantification for human 7T DMI. Glioblastomas showed elevated Lac and reduced Glx labeling relative to normal brain, with inter-patient heterogeneity consistent with an existence of different metabolic subtypes.