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A simple low‐SAR technique for chemical‐shift selection with high‐field spin‐echo imaging
Author(s) -
Ivanov Dimo,
Schäfer Andreas,
Streicher Markus N.,
Heidemann Robin M.,
Trampel Robert,
Turner Robert
Publication year - 2010
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.22518
Subject(s) - specific absorption rate , spin echo , excitation , nuclear magnetic resonance , echo (communications protocol) , signal (programming language) , amplitude , artifact (error) , pulse sequence , pulse (music) , planar , materials science , magnetic resonance imaging , optics , chemistry , physics , computer science , medicine , telecommunications , computer network , computer graphics (images) , quantum mechanics , detector , antenna (radio) , computer vision , radiology , programming language
We have discovered a simple and highly robust method for removal of chemical shift artifact in spin‐echo MR images, which simultaneously decreases the radiofrequency power deposition (specific absorption rate). The method is demonstrated in spin‐echo echo‐planar imaging brain images acquired at 7 T, with complete suppression of scalp fat signal. When excitation and refocusing pulses are sufficiently different in duration, and thus also different in the amplitude of their slice‐select gradients, a spatial mismatch is produced between the fat slices excited and refocused, with no overlap. Because no additional radiofrequency pulse is used to suppress fat, the specific absorption rate is significantly reduced compared with conventional approaches. This enables greater volume coverage per unit time, well suited for functional and diffusion studies using spin‐echo echo‐planar imaging. Moreover, the method can be generally applied to any sequence involving slice‐selective excitation and at least one slice‐selective refocusing pulse at high magnetic field strengths. The method is more efficient than gradient reversal methods and more robust against inhomogeneities of the static (polarizing) field (B 0 ). Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.