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Referenceless reconstruction of spatiotemporally encoded imaging data: Principles and applications to real‐time MRI
Author(s) -
Seginer Amir,
Schmidt Rita,
Leftin Avigdor,
Solomon Eddy,
Frydman Lucio
Publication year - 2014
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.25084
Subject(s) - undersampling , computer science , encoding (memory) , aliasing , computer vision , echo planar imaging , artificial intelligence , echo (communications protocol) , real time mri , magnetic resonance imaging , medicine , radiology , computer network
Purpose Ultrafast sequences based on “Hybrid” spatiotemporal encoding (SPEN) replace echo‐planar imaging's phase encoding “blips,” while retaining a k‐space readout acquisition. Hardware imperfections during acquisition may lead to ghosts and striped artifacts along the SPEN dimension; akin to echo‐planar imaging's Nyquist ghosts, but weaker. A referenceless method to eliminate these artifacts in Hybrid SPEN is demonstrated. Theory and Methods Owing to its encoding in direct space, rather than reciprocal space, undersampling in SPEN does not generate an echo‐planar‐imaging‐like aliasing, but instead lowers the spatial resolution. Hybrid SPEN data can be split into two undersampled signals: a reference one comprised of the odd‐echos, and an even‐echo set that has to be “corrected” for consistency with the former. A simple way of implementing such a correction that enables a joint high‐resolution reconstruction is proposed. Results The referenceless algorithm is demonstrated with various examples, including oblique scans, large in vivo datasets from real‐time dynamic contrast‐enhanced perfusion experiments, and human brain imaging. Conclusions The referenceless correction enables robust single‐scan imaging under changing conditions—such as patient motion and changes in shimming over time—without the need of ancillary navigators. This opens new options for real‐time MRI and interactive scanning. Magn Reson Med 72:1687–1695, 2014. © 2013 Wiley Periodicals, Inc.