title: Within- and between-session reproducibility of GABA measurements with MR spectroscopy.
abstract: The reproducibility of the MEGA-PRESS (MEshcher-GArwood Point RESolved Spectroscopy) MR spectroscopy sequence for the measurement of gamma- aminobutyric acid (GABA) is addressed, focusing on optimizing the number of repetitions at two voxel locations in the human brain and associated possibilities in analysis tools.
  
  
  
  Two 20-min MEGA-PRESS acquisitions were run (echo time = 68 ms, repetition time = 1800 ms, repetitions = 328): one from a 21 mL volume in the anterior cingulate cortex (ACC) and one from a 22 mL volume in the left Broca's area in 21 healthy male volunteers (age 32 years ± 6[SD]). Subjects were scanned twice with identical protocols, 1 week apart. Data were acquired on a 3 Tesla GE Discovery 750 scanner using a 32-channel head coil. Spectroscopy data were partitioned into shorter epochs, numerically equivalent to scans of progressively increasing duration, and compared both within and between sessions. Three different analysis schemes were applied: (1) Vendor prototype preprocessor, with quantification by LCModel. (2) Pure Gannet pipeline. (3) Preprocessing with Gannet, and quantification with LCModel. The coefficient of variation (CV) were calculated as a measure of reproducibility.
  
  
  
  Increasing the number of repetitions showed improvements for within- and between-session reproducibility up to around 218 repetitions. (CV ranging from 4 to 14%). Gannet combined with LCModel approach proved the best method. (CV = 4-5%). Measurements from the ACC area had higher CVs than the Broca area. (CV = 6-14% versus 4-7%).
  
  
  
  Measurement in the Broca area yields better reproducibility than the ACC. With appropriate acquisition times and preprocessing tools, measurements from the ACC area are also reliable.
  
  
  
  1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:421-430.
authors.affiliation: Department of Radiology, Haukeland University Hospital, Bergen, Norway.|Department of Clinical Medicine (K1), University of Bergen, Bergen, Norway.
authors.forename: Maiken K
authors.initials: MK
authors.lastname: Brix
authors.affiliation: Department of Clinical Engineering, Haukeland University Hospital, Bergen, Norway.|NORMENT - Norwegian Center for Mental Disorders Research, University of Bergen, Bergen, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Ersland
authors.affiliation: Department of Radiology, Haukeland University Hospital, Bergen, Norway.|NORMENT - Norwegian Center for Mental Disorders Research, University of Bergen, Bergen, Norway.|Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.|Division of Psychiatry, Haukeland University Hospital, Bergen, Norway.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.affiliation: Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.
authors.forename: Gerard E
authors.initials: GE
authors.lastname: Dwyer
authors.affiliation: Department of Radiology, Haukeland University Hospital, Bergen, Norway.|NORMENT - Norwegian Center for Mental Disorders Research, University of Bergen, Bergen, Norway.|Department of Physics and Technology, University of Bergen, Bergen, Norway.
authors.forename: Renate
authors.initials: R
authors.lastname: Grüner
authors.affiliation: MR Applications and Workflow Development, GE Healthcare, Berlin, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Noeske
authors.affiliation: Department of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway.|Department of Life Sciences and Health, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Oslo, Norway.
authors.forename: Mona K
authors.initials: MK
authors.lastname: Beyer
authors.affiliation: NORMENT - Norwegian Center for Mental Disorders Research, University of Bergen, Bergen, Norway.|Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Craven
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging*; D001931:Brain Mapping; D065711:Broca Area / Q000000981:diagnostic imaging*; D018698:Glutamic Acid / Q000737:chemistry; D006179:Gyrus Cinguli / Q000000981:diagnostic imaging; D064368:Healthy Volunteers; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011446:Prospective Studies; D015203:Reproducibility of Results; D012984:Software; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid
keywords: GABA; MEGA-PRESS; MRS; reproducibility