title: Functional quantitative susceptibility mapping (fQSM).
abstract: Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is a powerful technique, typically based on the statistical analysis of the magnitude component of the complex time-series. Here, we additionally interrogated the phase data of the fMRI time-series and used quantitative susceptibility mapping (QSM) in order to investigate the potential of functional QSM (fQSM) relative to standard magnitude BOLD fMRI. High spatial resolution data (1mm isotropic) were acquired every 3 seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B0. Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM time-series and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatio-temporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data. Our results present the potential of fQSM as a quantitative method of mapping BOLD changes. We also critically discuss the technical challenges and issues linked to this intriguing new technique.
authors.affiliation: High-Field MR Centre, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany; Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom. Electronic address: david.balla@tuebingen.mpg.de.
authors.forename: Dávid Z
authors.initials: DZ
authors.lastname: Balla
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Sanchez-Panchuelo
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Wharton
authors.affiliation: High-Field MR Centre, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany; Department for Biomedical Magnetic Resonances, University of Tübingen, Tübingen, Germany.
authors.forename: Gisela E
authors.initials: GE
authors.lastname: Hagberg
authors.affiliation: High-Field MR Centre, Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany; Department for Biomedical Magnetic Resonances, University of Tübingen, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Susan T
authors.initials: ST
authors.lastname: Francis
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Bowtell
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology; D014796:Visual Perception / Q000502:physiology
keywords: Functional QSM; MR phase imaging; Quantitative BOLD; Specific brain activation; Susceptibility mapping; fMRI