title: In vivo detection of GABA and glutamate with MEGA-PRESS: reproducibility and gender effects.
abstract: OBJECTIVE
  To evaluate the reproducibility of γ-amino-butyric acid (GABA) and glutamate concentrations derived using three different spectral fitting methods, and to investigate gender-related differences in neurotransmitter levels.
  
  
  METHODS
  Single voxel MEGA-edited PRESS MR spectra were acquired from a 30-mL voxel in the dorso-lateral prefrontal cortex in 14 adult volunteers (7 female) at 3 Tesla (3T). For each participant, four consecutive resting spectra were acquired within the same scanning session. Metabolite concentrations were derived using LCModel, jMRUI, and locally written peak fitting software. The within-session reproducibility for each analysis method was calculated as the average coefficient of variation (CV) of the GABA and Glx (glutamate+glutamine) concentrations. Gender differences in GABA and Glx were evaluated using a two-tailed unpaired t-test.
  
  
  RESULTS
  LCModel provided the best reproducibility for both GABA (CV 7%) and Glx (CV 6%). GABA, Glx, and glutamate concentrations were significantly higher in the male participants, (P = 0.02, P = 0.001, and P < 0.001, respectively).
  
  
  CONCLUSIONS
  GABA and glutamate can be quantified in vivo with high reproducibility (CV 6-7%) using frequency-domain spectral fitting methods like LCModel. However, the GABA and glutamate concentrations vary significantly between men and women, emphasizing the importance of gender-matching for studies investigating differences in neurotransmitter concentrations between mixed-cohort groups.
authors.affiliation: MR Center, University Children's Hospital, Zürich, Switzerland. ruth.ogorman@kispi.uzh.ch
authors.forename: Ruth L
authors.initials: RL
authors.lastname: O'Gorman
authors.forename: Lars
authors.initials: L
authors.lastname: Michels
authors.forename: Richard A
authors.initials: RA
authors.lastname: Edden
authors.forename: James B
authors.initials: JB
authors.lastname: Murdoch
authors.forename: Ernst
authors.initials: E
authors.lastname: Martin
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology; D001931:Brain Mapping / Q000379:methods; D005260:Female; D018698:Glutamic Acid / Q000737:chemistry*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012737:Sex Factors; D005680:gamma-Aminobutyric Acid / Q000737:chemistry*
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid