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Single‐shot dual‐z‐shimmed sensitivity‐encoded spiral‐in/out imaging for functional MRI with reduced susceptibility artifacts
Author(s) -
Truong TrongKha,
Song Allen W.
Publication year - 2008
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21473
Subject(s) - shim (computing) , blood oxygenation , spiral (railway) , gradient echo , computer science , functional magnetic resonance imaging , nuclear magnetic resonance , blood oxygen level dependent , temporal resolution , physics , magnetic resonance imaging , image resolution , sensitivity (control systems) , functional imaging , single shot , biological system , biomedical engineering , artificial intelligence , optics , mathematics , electronic engineering , neuroscience , biology , medicine , radiology , mathematical analysis , engineering , erectile dysfunction
Blood oxygenation level‐dependent (BOLD) functional MRI (fMRI) can be severely hampered by signal loss due to susceptibility‐induced static magnetic field ( B 0 ) inhomogeneities near air/tissue interfaces. A single‐shot spiral‐in/out sequence with a z‐shim gradient embedded between the two acquisitions was previously proposed to efficiently recover the signal. However, despite promising results, this technique had several limitations, which are addressed here as follows. First, by adding a second z‐shim gradient before the spiral‐in acquisition and optimizing both z‐shim gradients slice‐by‐slice, a significantly more uniform signal recovery can be achieved. Second, by acquiring a B 0 map, the optimal z‐shim gradients can be directly, efficiently, and accurately determined for each subject. Third, by complementing the z‐shimming approach with sensitivity encoding (SENSE), the in‐plane spatial resolution can be increased and, hence, susceptibility artifacts further reduced, while maintaining a high temporal resolution for fMRI applications. These advantages are demonstrated in human functional studies. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.