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Simulated phase evolution rewinding (SPHERE): A technique for reducing B 0 inhomogeneity effects in MR images
Author(s) -
Kadah Yasser M.,
Hu Xiaoping
Publication year - 1997
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.1910380416
Subject(s) - k space , spiral (railway) , computer science , phase (matter) , planar , phase space , image (mathematics) , data set , fourier transform , echo planar imaging , physics , image processing , field (mathematics) , artificial intelligence , nuclear magnetic resonance , computer vision , algorithm , magnetic resonance imaging , mathematics , mathematical analysis , computer graphics (images) , quantum mechanics , pure mathematics , thermodynamics , medicine , radiology
A novel method for reducing field inhomogeneity effects in magnetic resonance images is described in this paper. Observing that image degradation arises from B 0 inhomogeneity‐induced phase accrual during data acquisition, the present method numerically rewinds the accumulated phase in the k ‐space data based on an initial estimate of the image and a corresponding field map. The rewinding process generates a corrected k ‐space data set that is subsequently Fourier transformed to produce the final image. In this paper, a theoretical analysis of the method and applications of the technique to magnetic resonance imaging data are presented. The theoretical analysis of the method indicates that it is a general approach applicable to a variety of sequences. Results obtained by applying the method to experimental data acquired with single‐shot echo‐planar imaging, segmented echo‐planar imaging with centric reordering, and spiral sequences demonstrate that it is robust in reducing image degradation induced by B 0 inhomogeneity.