Sub-millimeter T2 weighted fMRI at 7 T: Comparison of 3D-GRASE and 2D SE-EPI

Valentin G. Kemper, Federico De Martino, An T Vu, Benedikt A. Poser, David A. Feinberg, Rainer Goebel, Essa Yacoub

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39 Scopus citations

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 T2* 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, functional specificity, and functional sensitivity at sub-millimeter resolution. Simulations and measurements of the imaging point-spread function 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. 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 T2* 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.

Original languageEnglish (US)
Article number163
JournalFrontiers in Neuroscience
Volume9
Issue numberAPR
DOIs
StatePublished - 2015

Bibliographical note

Publisher Copyright:
© 2015 Kemper, De_martino, Vu, Poser, Feinberg, Goebel and Yacoub.

Keywords

  • 3D-GRASE
  • High-resolution BOLD fMRI
  • Point-spread function
  • Spin-echo EPI
  • T2
  • T2*

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