Reference : Improved shimming for fMRI specifically optimizing the local BOLD sensitivity
Scientific journals : Article
Life sciences : Anatomy (cytology, histology, embryology...) & physiology
Physical, chemical, mathematical & earth Sciences : Physics
http://hdl.handle.net/2268/101538
Improved shimming for fMRI specifically optimizing the local BOLD sensitivity
English
Balteau, Evelyne mailto [Université de Liège - ULg > > Centre de recherches du cyclotron >]
Hutton, Chloe mailto [University College London - UCL > > Wellcome Trust Centre for Neuroimaging > >]
Weiskopf, Nikolaus mailto [University College London - UCL > > Wellcome Trust Centre for Neuroimaging > >]
2010
NeuroImage
Elsevier Science
49
327-336
Yes (verified by ORBi)
International
1053-8119
1095-9572
Orlando
FL
[en] BOLD sensitivity ; Shimming ; fMRI
[en] In functional MRI, magnetic field inhomogeneities due to air-tissue susceptibility differences may lead to severe signal dropouts and geometric distortions in echo-planar images. Therefore, the inhomogeneities in the field are routinely minimized by shimming prior to imaging. However in fMRI, the Blood Oxygen Level Dependent (BOLD) effect is the measure of interest, so the BOLD sensitivity (BS) should be optimized rather than the magnetic field homogeneity. The analytical expression for an estimate of the BOLD sensitivity has been recently developed, allowing for the computation of BOLD sensitivity maps from echo-planar images and field maps. This report describes a novel shimming procedure that optimizes the local BOLD sensitivity over a region of interest. The method is applied in vivo and compared to a standard global shimming procedure. A breath-holding experiment was carried out and demonstrated that the BS-based shimming significantly improved the detection of activation in a target region of interest, the medial orbitofrontal cortex.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; Wellcome Trust
http://hdl.handle.net/2268/101538

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