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Multiple gradient echo sequence optimized for rapid, single‐scan mapping of R 2 * at high B 0
Author(s) -
Wild Jim M.,
Martin W.R. Wayne,
Allen Peter S.
Publication year - 2002
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.10291
Subject(s) - gradient echo , sequence (biology) , echo (communications protocol) , nuclear magnetic resonance , pulse sequence , physics , chemistry , computer science , magnetic resonance imaging , radiology , medicine , computer network , biochemistry
A multiple‐gradient‐echo sequence is proposed for accurately mapping R 2 *in the presence of in‐slice macroscopic susceptibility gradients. In‐slice signal loss caused by background macroscopic susceptibility gradients is mitigated by combining three successive gradient‐echo images whose slice refocus gradients are successively incremented. The optimum incrementation of slice‐refocusing gradients was determined by numerical simulation. By repeating further cycles of three images in the same sequence, artifact‐compensated data spanning a range of echo times (TEs) was acquired leading to single‐scan, R 2 *maps that are quantitatively reflective of microscopic field inhomogeneities. The performance of the sequence was demonstrated at 3.0T, first with a doped aqueous phantom, and then on the head of a normal volunteer. That performance is compared quantitatively with previously published work. Magn Reson Med 48:867–876, 2002. © 2002 Wiley‐Liss, Inc.