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Dynamic 2D self‐phase‐map Nyquist ghost correction for simultaneous multi‐slice echo planar imaging
Author(s) -
Yarach Uten,
Tung YiHang,
Setsompop Kawin,
In MyungHo,
Chatnuntawech Itthi,
Yakupov Renat,
Godenschweger Frank,
Speck Oliver
Publication year - 2018
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.27123
Subject(s) - ghosting , smoothing , computer science , multislice , regularization (linguistics) , iterative reconstruction , undersampling , algorithm , reconstruction algorithm , artificial intelligence , physics , computer vision , nuclear magnetic resonance , mathematics
Purpose To develop a reconstruction pipeline that intrinsically accounts for both simultaneous multislice echo planar imaging (SMS‐EPI) reconstruction and dynamic slice‐specific Nyquist ghosting correction in time‐series data. Methods After 1D slice‐group average phase correction, the separate polarity (i.e., even and odd echoes) SMS‐EPI data were unaliased by slice GeneRalized Autocalibrating Partial Parallel Acquisition. Both the slice‐unaliased even and odd echoes were jointly reconstructed using a model‐based framework, extended for SMS‐EPI reconstruction that estimates a 2D self‐phase map, corrects dynamic slice‐specific phase errors, and combines data from all coils and echoes to obtain the final images. Results The percentage ghost‐to‐signal ratios (%GSRs) and its temporal variations for MB3R y 2 with a field of view/4 shift in a human brain obtained by the proposed dynamic 2D and standard 1D phase corrections were 1.37 ± 0.11 and 2.66 ± 0.16, respectively. Even with a large regularization parameter λ applied in the proposed reconstruction, the smoothing effect in fMRI activation maps was comparable to a very small Gaussian kernel size 1 × 1 × 1 mm 3 . Conclusion The proposed reconstruction pipeline reduced slice‐specific phase errors in SMS‐EPI, resulting in reduction of GSR. It is applicable for functional MRI studies because the smoothing effect caused by the regularization parameter selection can be minimal in a blood‐oxygen‐level–dependent activation map.