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Ghost artifact reduction for echo planar imaging using image phase correction
Author(s) -
Buonocore Michael H.,
Gao Lisheng
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.1910380114
Subject(s) - artifact (error) , echo planar imaging , reduction (mathematics) , phase (matter) , echo (communications protocol) , nuclear magnetic resonance , planar , computer science , artificial intelligence , materials science , computer vision , magnetic resonance imaging , physics , mathematics , medicine , radiology , computer graphics (images) , computer network , geometry , quantum mechanics
An algorithm is described for reducing ghost artifacts in echo planar imaging (EPI) using phase corrections derived from images reconstructed using only even or odd k ‐space lines. The N /2 ghost, that arises principally from time‐reversal of alternate k ‐space lines, was significantly reduced by this algorithm without the need for a calibration scan. In images obtained in eight subjects undergoing EPI for auditory functional MRI (fMRI) experiments, N /2 ghost intensity was reduced from 10.3% – 2.1% (range: 7.9–14.1%) to 4.5% ± 0.2% (range: 4.1–4.9%) of parent image intensity, corresponding to a percent reduction in ghost intensity of 54% ± 9% (range: 43–65%), and the algorithm restored this intensity to the parent image. It provided a significant improvement in image appearance, and increased the correlation coefficients related to neural activation in functional MRI studies. The algorithm provided reduction of artifacts from all polynomial orders of spatial phase errors in both spatial directions. The algorithm did not eliminate N /2 ghost intensity contributed by field inhomogeneities, susceptibility, or chemical shift.