Gamma‐aminobutyric acid edited echo‐planar spectroscopic imaging (EPSI) with MEGA‐sLASER at 7T

Peter O. Magnusson*, Vincent O. Boer, Anouk Marsman, Olaf B. Paulson, Lars G. Hanson, Esben Thade Petersen

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review

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    Abstract

    Purpose: For rapid spatial mapping of gamma‐aminobutyric acid (GABA) at the
    increased sensitivity and spectral separation for ultra‐high magnetic field strength (7
    tesla [T]) an accelerated edited magnetic resonance spectroscopic imaging technique
    was developed and optimized for the human brain at 7 T.
    Methods: A MEGA‐sLASER sequence was used for GABA editing and volume
    selection to maximize editing efficiency and minimize chemical shift displacement
    errors. To accommodate the high bandwidth requirements at 7 T, a single‐shot echo
    planar readout was used for rapid simultaneous encoding of the temporal dimension
    and 1 spatial. B0 and B1 field aspects specific for 7 T were studied together with correction
    procedures, and feasibility of the EPSI MEGA‐sLASER technique was tested
    in vivo in 5 healthy subjects.
    Results: Localized edited spectra could be measured in all subjects giving spatial
    GABA signal distributions over a central brain region, having 45‐ to 50‐Hz spatial
    intervoxel B0 field variations and up to 30% B1 field deviations. MEGA editing was
    found unaffected by the B0 inhomogeneities for the optimized sequence. The correction
    procedures reduced effects of intervoxel B0 inhomogeneities, corrected for spatial
    editing efficiency variations, and compensated for GABA resonance phase and
    frequency shifts from subtle motion and acquisition instabilities. The optimized oscillating
    echo‐planar gradient scheme permitted full spectral acquisition at 7 T and
    exhibited minimal spectral‐spatial ghosting effects for the selected brain region.
    Conclusion: The EPSI MEGA‐sLASER technique was shown to provide time‐efficient
    mapping of regional variations in cerebral GABA in a central volume of interest
    with spatial B1 and B0 field variations typical for 7 T.
    Original languageEnglish
    JournalMagnetic Resonance in Medicine
    Volume81
    Issue number2
    Pages (from-to)773-780
    ISSN0740-3194
    DOIs
    Publication statusPublished - 2018

    Keywords

    • 7T
    • Edited MRSI
    • EPSI
    • GABA

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