title: Sub-millimeter T2 weighted fMRI at 7 T: comparison of 3D-GRASE and 2D SE-EPI.
abstract: Functional magnetic resonance imaging (fMRI) allows studying human brain function non-invasively up to the spatial resolution of cortical columns and layers. Most fMRI acquisitions rely on the blood oxygenation level dependent (BOLD) contrast employing T(*) 2 weighted 2D multi-slice echo-planar imaging (EPI). At ultra-high magnetic field (i.e., 7 T and above), it has been shown experimentally and by simulation, that T2 weighted acquisitions yield a signal that is spatially more specific to the site of neuronal activity at the cost of functional sensitivity. This study compared two T2 weighted imaging sequences, inner-volume 3D Gradient-and-Spin-Echo (3D-GRASE) and 2D Spin-Echo EPI (SE-EPI), with evaluation of their imaging point-spread function (PSF), functional specificity, and functional sensitivity at sub-millimeter resolution. Simulations and measurements of the imaging PSF revealed that the strongest anisotropic blurring in 3D-GRASE (along the second phase-encoding direction) was about 60% higher than the strongest anisotropic blurring in 2D SE-EPI (along the phase-encoding direction). In a visual paradigm, the BOLD sensitivity of 3D-GRASE was found to be superior due to its higher temporal signal-to-noise ratio (tSNR). High resolution cortical depth profiles suggested that the contrast mechanisms are similar between the two sequences, however, 2D SE-EPI had a higher surface bias owing to the higher T(*) 2 contribution of the longer in-plane EPI echo-train for full field of view compared to the reduced field of view of zoomed 3D-GRASE.
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Department of Cognitive Neuroscience, Maastricht Brain Imaging Center, Maastricht University Maastricht, Netherlands.
authors.forename: Valentin G
authors.initials: VG
authors.lastname: Kemper
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Department of Cognitive Neuroscience, Maastricht Brain Imaging Center, Maastricht University Maastricht, Netherlands ; Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota Medical School Minneapolis, MN, USA.
authors.forename: Federico
authors.initials: F
authors.lastname: De Martino
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota Medical School Minneapolis, MN, USA.
authors.forename: An T
authors.initials: AT
authors.lastname: Vu
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Department of Cognitive Neuroscience, Maastricht Brain Imaging Center, Maastricht University Maastricht, Netherlands.
authors.forename: Benedikt A
authors.initials: BA
authors.lastname: Poser
authors.affiliation: Advanced MRI Technologies Sebastopol, CA, USA ; Brain Imaging Center, Helen Wills Institute for Neuroscience, University of California, Berkeley Berkeley, CA, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Feinberg
authors.affiliation: Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University Maastricht, Netherlands ; Department of Cognitive Neuroscience, Maastricht Brain Imaging Center, Maastricht University Maastricht, Netherlands ; Department of Neuroimaging and Neuromodeling, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences (KNAW) Amsterdam, Netherlands.
authors.forename: Rainer
authors.initials: R
authors.lastname: Goebel
authors.affiliation: Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota Medical School Minneapolis, MN, USA.
authors.forename: Essa
authors.initials: E
authors.lastname: Yacoub
keywords: 3D-GRASE; Spin-Echo EPI; T2; T2*; high-resolution BOLD fMRI; point-spread function