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Stimulated echo induced misestimates on diffusion tensor indices and its remedy
Author(s) -
Chuang TzuChao,
Wu MingTing,
Huang TengYi,
Lin YiRu,
Tsai ShangYueh,
Chang HingChiu,
Chung HsiaoWen
Publication year - 2010
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.22182
Subject(s) - splenium , corpus callosum , diffusion mri , nuclear magnetic resonance , spin echo , diffusion , echo (communications protocol) , physics , anisotropy , materials science , nuclear medicine , magnetic resonance imaging , optics , medicine , computer science , anatomy , radiology , computer network , thermodynamics
Purpose: To report possible erroneous estimates of diffusion parameters in the twice‐refocused spin‐echo (TRSE) technique, proposed to eliminate eddy‐current‐induced geometric distortions in diffusion‐weighted echo‐planar imaging, when stimulated echo signals are inappropriately included. Materials and Methods: Eleven subjects were included for imaging experiments on two 1.5 Tesla systems using the TRSE sequence. Three versions, two with unbalanced crusher gradients inserted to dephase the stimulated echo from the b = 0 images and one with balanced crusher gradients, were implemented. The apparent diffusion coefficients (ADC) and fractional anisotropy (FA) were derived and compared. Results: The ADCs obtained with unbalanced crusher gradients were closer to values reported in the literature. Stimulated echo led to ADC over‐estimations by 34.2%, 50.4%, 54.0%, 51.5%, 24.0%, and 41.9% in the genu of corpus callosum, splenium of corpus callosum, bilateral corona radiata, internal capsule, mediofrontal gyrus, and the cuneus, respectively ( P < 0.01), with concomitant reduction in FA in highly anisotropic regions. Over‐estimations of diffusion coefficients were found to be roughly equal along all directions. Conclusion: Formation of stimulated echo in the TRSE technique can lead to erroneous estimations of the diffusion parameters, even if no prominent morphological artifacts are seen. J. Magn. Reson. Imaging 2010;31:1522–1529. © 2010 Wiley‐Liss, Inc.