title: Detection of glutamate, glutamine, and glutathione by radiofrequency suppression and echo time optimization at 7 tesla.
abstract: OBJECTIVE
  To 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.
  
  
  METHODS
  Using density matrix simulations, a PRESS sequence with (TE1 , TE2 ) = (69, 37) ms and an inserted 90° J-suppression pulse were found to minimize the NAA multiplet at 2.49 ppm.
  
  
  RESULTS
  NAA 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 (1) H spectra acquired during intravenous [U-(13) C6 ]glucose infusion showed gradually changing Glu C4 and Gln C4 proton resonance signals in a spectral pattern predicted by numerical simulations.
  
  
  CONCLUSIONS
  Reliable 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 (13) C incorporation into Glu and Gln during infusion of (13) C labeled glucose.
authors.affiliation: National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Li
authors.initials: L
authors.lastname: An
authors.forename: Shizhe
authors.initials: S
authors.lastname: Li
authors.forename: James B
authors.initials: JB
authors.lastname: Murdoch
authors.forename: Maria Ferraris
authors.initials: MF
authors.lastname: Araneta
authors.forename: Christopher
authors.initials: C
authors.lastname: Johnson
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D002540:Cerebral Cortex / Q000737:chemistry*; D005260:Female; D018698:Glutamic Acid / Q000032:analysis*; D005973:Glutamine / Q000032:analysis*; D005978:Glutathione / Q000032:analysis*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D005973:Glutamine; D018698:Glutamic Acid; D005978:Glutathione
keywords: J-suppression; TE-optimization; glutamate; glutamine; glutathione