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Increased diffusion sensitivity with hyperechos
Author(s) -
Frank Lawrence R.,
Wong Eric C.,
Liu Thomas T.,
Buxton Richard B.
Publication year - 2003
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.10457
Subject(s) - diffusion , nuclear magnetic resonance , pulse sequence , spin echo , sequence (biology) , pulse (music) , physics , signal (programming language) , sensitivity (control systems) , contrast (vision) , diffusion imaging , noise (video) , echo (communications protocol) , signal to noise ratio (imaging) , diffusion mri , chemistry , magnetic resonance imaging , optics , computer science , medicine , artificial intelligence , quantum mechanics , radiology , computer network , biochemistry , electronic engineering , detector , image (mathematics) , programming language , engineering
Abstract It is shown that the introduction of a 180° refocusing pulse into a standard diffusion weighted stimulated echo sequence is equivalent to the simplest hyperecho sequence with identical diffusion weighting but equal or greater signal‐to‐noise (SNR) and thus equal or greater diffusion contrast. For high b ‐value imaging, the hyperecho sequence thus possesses the high diffusion contrast in the presence of small T 1 / T 2 ratios characteristic of stimulated echo sequences but with less than the 50% loss in SNR that is associated with the stimulated echo. For low b ‐value imaging, the hyperecho signal converges to that of the standard spin echo. The advantages of the two‐pulse diffusion weighted hyperecho sequence are demonstrated theoretically. Experimental results are shown in the application to high angular resolution diffusion encoding (HARD) in normal human brain. Magn Reson Med 49:1098–1105, 2003. Published 2003 Wiley‐Liss, Inc.