Detection of Glutamate, Glutamine, and Glutathione by Radiofrequency Suppression and Echo Time Optimization at 7 Tesla

PurposeTo achieve detection of glutamate (Glu), glutamine (Gln), and glutathione (GSH) by minimizing the N-acetyl-aspartate (NAA) multiplet signals at 2.49 ppm using a echo time (TE) -optimized PRESS pulse sequence and a novel J-suppression radiofrequency pulse. MethodsUsing density matrix simulations, a PRESS sequence with (TE1, TE2)=(69, 37) ms and an inserted 90 degrees J-suppression pulse were found to minimize the NAA multiplet at 2.49 ppm. ResultsNAA phantom experiments confirmed the successful suppression of the NAA multiplet at 2.49 ppm. A study of eight healthy volunteers found both Glu and Gln to be significantly higher in gray matter (GM) dominant medial prefrontal cortex voxels than in white matter (WM) dominant right frontal cortex voxels. Time-course H-1 spectra acquired during intravenous [U-C-13(6)]glucose infusion showed gradually changing Glu C4 and Gln C4 proton resonance signals in a spectral pattern predicted by numerical simulations. ConclusionReliable detection of Glu, Gln, and GSH was achieved. Glu and Gln levels were significantly higher in frontal lobe GM than in frontal lobe WM. It is feasible to use the proposed proton MR spectroscopy method to measure the kinetics of C-13 incorporation into Glu and Gln during infusion of C-13 labeled glucose. Magn Reson Med 73:451-458, 2015. (c) 2014 Wiley Periodicals, Inc.