title: The separation of Gln and Glu in STEAM: a comparison study using short and long TEs/TMs at 3 and 7 T.
abstract: OBJECTIVE
  This study aimed to determine the optimal echo time (TE) and mixing time (TM) for in vivo glutamine (Gln) and glutamate (Glu) separation in stimulated-echo acquisition mode at 3 and 7 T. We applied a short TE/TM (20/10 ms) for a high signal-to-noise-ratio and a field-specific long TE/TM (3 T: 72/6 ms; 7 T: 74/68 ms) for optimal Gln and Glu separation of the Carbon-4 proton resonances.
  
  
  METHODS
  Corresponding Gln and Glu spectra were simulated using VeSPA software, and measured in a phantom and human brains at 3 and 7 T.
  
  
  RESULTS
  Higher spectral separation for Gln and Glu was achieved at 7 than 3 T. At 7 T, short TE/TM provided comparable spectral separation and in vitro Gln and Glu quantification compared to long TE/TM. Moreover, it showed greater reliability in in vivo Gln and Glu detection and separation than long TE/TM, with significantly lower Cramer-Rao lower bounds (Gln: 14.9 vs. 75.8; Glu: 3.8 vs. 6.5) and correlation between Gln and Glu (p = 0.004).
  
  
  CONCLUSIONS
  Based on the optimal separation for Gln and Glu, a short TE/TM at 7 T is proposed for future in vivo Gln and Glu acquisition.
authors.affiliation: Faculty for Natural Sciences, Biomedical Magnetic Resonance, Otto-von-Guericke University, ZENIT Building, Leipziger Str. 44, 39120, Magdeburg, Germany, douweiqiang@gmail.com.
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Dou
authors.forename: Jörn
authors.initials: J
authors.lastname: Kaufmann
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.forename: Kai
authors.initials: K
authors.lastname: Zhong
authors.forename: Martin
authors.initials: M
authors.lastname: Walter
authors.forename: Oliver
authors.initials: O
authors.lastname: Speck
mesh_terms: D000328:Adult; D001923:Brain Chemistry; D018698:Glutamic Acid / Q000737:chemistry*; D005973:Glutamine / Q000737:chemistry*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D012984:Software
chemical_list: D005973:Glutamine; D018698:Glutamic Acid