Abstract
PURPOSE: To achieve spectrally resolved in vivo detection of glutamate, glutamine, and glutathione at 3 T. METHODS: Difference editing of N-acetylaspartate CH(2) protons (NAA-CH(2)) combined with a new echo-time (TE) optimization approach is introduced. Difference editing was used to detect NAA-CH(2) independently of NAA-CH(3), thereby eliminating systematic errors arising from constrained fitting of the entire NAA molecule. Numerical optimization of TE and TE(1) 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-(13)C]glucose. RESULTS: 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-(13)C proton MR-spectroscopy spectra clearly demonstrated the dynamic (13)C-labeling of glutamate C4 following oral [U-(13)C]glucose intake. CONCLUSION: This technique enables simultaneous spectral resolution of glutamate, glutamine, and glutathione peaks at 3 T using difference editing of NAA-CH(2) and an optimized TE of 85 ms. Additionally, it demonstrates, for the first time, the feasibility of measuring (13)C turnovers of spectrally resolved glutamate at 3 T with the high sensitivity and spatial resolution of proton MR spectroscopy.