title: Reproducibility of brain spectroscopy at 7T using conventional localization and spectral editing techniques.
abstract: OBJECTIVE
  To evaluate the reproducibility of spectroscopic measurements from the anterior cingulate (AC) and the dorsolateral prefrontal cortex (DLPFC) regions at 7T using a 32-channel head coil.
  
  
  METHODS
  Spectra were acquired in four healthy subjects each scanned twice using a stimulated echo acquisition mode (STEAM) sequence, and a MEGA-PRESS-IVS sequence for gamma-aminobutyric acid (GABA) editing. STEAM spectra were quantified using LCModel, whereas MEGA-PRESS-IVS data were analyzed using peak integrals determined using in-house software. Mean coefficient of variation (CV) and mean absolute difference between visits were calculated.
  
  
  RESULTS
  For the AC STEAM dataset, the mean CV between visits was 6.2% for prominent metabolites such as N-acetylaspartate (NAA), total creatine (tCr), and total choline (tCho) and 6.3% for low signal-to-noise ratio (SNR) metabolites such as glutamate (Glu), glutamine (Gln), and GABA. The mean CV between visits for the DLPFC STEAM dataset was 8.5% for prominent metabolites and 21% for lower SNR metabolites. In the AC, the reproducibility measures for GABA were superior for STEAM compared to MEGA-PRESS-IVS (mean CV of 3.5% vs. 13.6%), but the opposite pattern was observed in the DLPFC region (mean CV of 16.2% vs. 13.4%).
  
  
  CONCLUSIONS
  7T MR spectroscopy of the AC and DLPFC using both short TE STEAM and MEGA-PRESS-IVS sequences provide excellent reproducibility of 12 metabolites, including GABA.
authors.affiliation: Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: S Andrea
authors.initials: SA
authors.lastname: Wijtenburg
authors.forename: Laura M
authors.initials: LM
authors.lastname: Rowland
authors.forename: Richard A E
authors.initials: RA
authors.lastname: Edden
authors.forename: Peter B
authors.initials: PB
authors.lastname: Barker
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D002794:Choline / Q000378:metabolism*; D003404:Creatinine / Q000378:metabolism*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D055815:Young Adult
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003404:Creatinine; D002794:Choline
keywords: 7T; GABA; STEAM; magnetic resonance spectroscopy; reproducibility