title: Retrospective correction of frequency drift in spectral editing: The GABA editing example.
abstract: GABA levels can be measured using proton MRS with a two-step editing sequence. However due to the low concentration of GABA, long acquisition time is usually needed to achieve sufficient SNR to detect small differences in many psychiatric disorders. During this long scan time the frequency offset of the measured voxel can change because of magnetic field drift and patient movement. This drift will change the frequency of the editing pulse relative to that of metabolites, leading to errors in quantification. In this article we describe a retrospective method to correct for frequency drift in spectral editing. A series of reference signals for each metabolite was generated for a range of frequency offsets and then averaged together based on the history of frequency changes over the scan. These customized basis sets were used to fit the in vivo data. Our results demonstrate the effectiveness of the correction method and the remarkable robustness of a GABA editing technique with a top hat editing profile in the presence of frequency drift.
authors.affiliation: Magnetic Resonance Spectroscopy Core Facility, NIMH-Intramural Research Program (IRP), National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: van der Veen
authors.affiliation: Clinical and Translational Neuroscience Branch, NIMH-Intramural Research Program (IRP), National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Marenco
authors.affiliation: Clinical and Translational Neuroscience Branch, NIMH-Intramural Research Program (IRP), National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Karen F
authors.initials: KF
authors.lastname: Berman
authors.affiliation: Magnetic Resonance Spectroscopy Core Facility, NIMH-Intramural Research Program (IRP), National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA.|Molecular Imaging Branch, NIMH-Intramural Research Program (IRP), National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Shen
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D003401:Creatine / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D055442:Metabolome; D012189:Retrospective Studies; D066127:White Matter / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C000179:N-acetylaspartate; D003401:Creatine
keywords: GABA editing; drift; magnetic resonance spectroscopy; retrospective correction