Simultaneous in vivo detection of spectrally resolved glutamate, glutamine, and glutathione at 3 T with NAA-aspartyl editing and echo-time optimization.

To achieve spectrally resolved in vivo detection of glutamate, glutamine, and glutathione at 3 T. Difference editing of N-acetylaspartate CH2 protons (NAA-CH2) combined with a new echo-time (TE) optimization approach is introduced. Difference editing was used to detect NAA-CH2 independently of NAA-CH3, thereby eliminating systematic errors arising from constrained fitting of the entire NAA molecule. Numerical optimization of TE and TE1 minimized interference from highly dominant glutamate in glutamine detection in the ON/OFF sum spectrum. In vivo data were acquired from 6 healthy participants, including 2 who underwent oral administration of U-13Cglucose. The NAA-aspartyl-edited, cleaned-up in vivo spectrum showed distinct separation of glutamate, glutamine, and glutathione peaks at 3 T, facilitating spectral quantification and clinical applications. The post-13C proton MR-spectroscopy spectra clearly demonstrated the dynamic 13C-labeling of glutamate C4 following oral U-13Cglucose intake. This technique enables simultaneous spectral resolution of glutamate, glutamine, and glutathione peaks at 3 T using difference editing of NAA-CH2 and an optimized TE of 85 ms. Additionally, it demonstrates, for the first time, the feasibility of measuring 13C turnovers of spectrally resolved glutamate at 3 T with the high sensitivity and spatial resolution of proton MR spectroscopy.