title: Prospective frequency correction for macromolecule-suppressed GABA editing at 3T.
abstract: To investigate the effects of B0field offsets and drift on macromolecule (MM)-suppressed GABA-editing experiments, and to implement and test a prospective correction scheme. "Symmetric" editing schemes are proposed to suppress unwanted coedited MM signals in GABA editing.
  
  
  
  Full density-matrix simulations of both conventional (nonsymmetric) and symmetric MM-suppressed editing schemes were performed for the GABA spin system to evaluate their offset-dependence. Phantom and in vivo (15 subjects at 3T) GABA-edited experiments with symmetrical suppression of MM signals were performed to quantify the effects of field offsets on the total GABA+MM signal (designated GABA+). A prospective frequency correction method based on interleaved water referencing (IWR) acquisitions was implemented and its experimental performance evaluated during positive and negative drift.
  
  
  
  Simulations show that the signal from MM-suppressed symmetrical editing schemes is an order of magnitude more susceptible to field offsets than the signal from nonsymmetric editing schemes. The MM-suppressed GABA signal changes by 8.6% per Hz for small field offsets. IWR significantly reduces variance in the field offset and measured GABA levels (both P < 0.001 by F-tests), maintaining symmetric suppression of MM signal.
  
  
  
  Symmetrical editing schemes substantially increase the dependence of measurements on B0field offsets, which can arise due to patient movement and/or scanner instability. It is recommended that symmetrical editing should be used in combination with effective B0stabilization, such as that provided by IWR. J. Magn. Reson. Imaging 2016;44:1474-1482.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Richard A E
authors.identifier: 0000-0002-0671-7374
authors.initials: RA
authors.lastname: Edden
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Georg
authors.initials: G
authors.lastname: Oeltzschner
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|CAIR Program, Alberta Children's Hospital Research Institute, University of Calgary, AB, Canada.|Department of Radiology, University of Calgary, AB, Canada.|Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, AB, Canada.
authors.forename: Ashley D
authors.initials: AD
authors.lastname: Harris
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Nicolaas A J
authors.initials: NA
authors.lastname: Puts
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Chan
authors.affiliation: Hvidovre Hospital, Danish Research Center for Magnetic Resonance, Hvidovre, Denmark.
authors.forename: Vincent O
authors.initials: VO
authors.lastname: Boer
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Schär
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Barker
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D005260:Female; D006801:Humans; D046911:Macromolecular Substances / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D008297:Male; D057054:Molecular Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D066244:Proton Magnetic Resonance Spectroscopy; D012815:Signal Processing, Computer-Assisted; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D005680:gamma-Aminobutyric Acid
keywords: B0 drift; GABA; MM-suppressed; field-frequency lock; instability; symmetrical editing