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Overdiscrete echo‐planar spectroscopic imaging with correlated higher‐order phase correction
Author(s) -
Coello Eduardo,
Hafalir Fatih S.,
Noeske Ralph,
Menzel Marion,
Haase Axel,
Menze Bjoern,
Schulte Rolf F.
Publication year - 2020
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.28105
Subject(s) - imaging phantom , computer science , phase (matter) , artifact (error) , iterative reconstruction , temporal resolution , algorithm , artificial intelligence , physics , optics , quantum mechanics
Purpose To introduce a robust methodology for fast 1 H MRSI of the brain at 3T with improved SNR and reduced phase‐related artifacts. Method An accelerated acquisition scheme using echo‐planar spectroscopic imaging (EPSI) was combined with the overdiscrete reconstruction framework. This approach enables the interleaved acquisition of a water reference scan at each phase encoding step, maximizing its correlation with the water‐suppressed measurement. Moreover, a generalized high‐order phase correction was incorporated into the reconstruction pipeline. The spatial–temporal phase correction term was estimated from the reference scan and interpolated to high resolution using a polynomial basis. The method was implemented at 3T and validated with phantom and in vivo experiments. Results The methodology showed the elimination of spectral artifacts generated by phase disturbances and achieved mean SNR gains in vivo of 3.18 and 1.19 compared to standard reconstructions with corrections performed at nominal and high resolution, respectively. EPSI scans with interleaved water acquisition showed to be robust to system instabilities and potentially to patient motion. Moreover, phase distortions were effectively corrected in a single step, avoiding additional reference measurements and post‐processing steps. Conclusion The overdiscrete reconstruction framework with high‐order phase correction allowed to effectively correct for distortions, related to B 0 inhomogeneities, B 0 drift, eddy currents, and system vibrations. Furthermore, the presented reconstruction method, combined with EPSI acquisitions, demonstrated improved measurement stability, substantial SNR enhancement, better spectral linewidth, and effective artifact removal.

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