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.
Original language | English |
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Article number | 163 |
Number of pages | 14 |
Journal | Frontiers in Neuroscience |
Volume | 9 |
DOIs | |
Publication status | Published - 5 May 2015 |
Keywords
- 3D-GRASE
- Spin-Echo EPI
- T2
- T2*
- point-spread function
- high-resolution BOLD fMRI
- POINT-SPREAD FUNCTION
- SPIN-ECHO FMRI
- 2D-SELECTIVE RF EXCITATIONS
- BOLD FUNCTIONAL MRI
- HIGH MAGNETIC-FIELD
- HUMAN BRAIN
- GRADIENT-ECHO
- HIGH-RESOLUTION
- SIGNAL CHANGES
- OF-VIEW