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Automatic gradient preemphasis adjustment: A 15‐minute journey to improved diffusion‐weighted echo‐planar imaging
Author(s) -
Schmithorst Vincent J.,
Dardzinski Bernard J.
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.10022
Subject(s) - echo planar imaging , diffusion mri , distortion (music) , diffusion , anisotropy , nuclear magnetic resonance , anisotropic diffusion , eddy current , computation , physics , effective diffusion coefficient , tensor (intrinsic definition) , gradient echo , image resolution , planar , materials science , optics , mathematics , computer science , magnetic resonance imaging , algorithm , geometry , medicine , radiology , amplifier , optoelectronics , computer graphics (images) , cmos , quantum mechanics , thermodynamics
Image distortion caused by gradient eddy currents is a major problem in the use of diffusion tensor imaging (DTI), as using the uncorrected images for calculation of apparent diffusion coefficient (ADC) and diffusion anisotropy will result in areas of artificially increased anisotropy and ADC at the edge of the images, as well as decreased spatial resolution and accuracy in ADC computations overall. This distortion may be substantially reduced by careful adjustment of the gradient preemphasis unit. A completely automatic method of adjusting the preemphasis unit is proposed which finds the optimal settings for all three gradient directions in approximately 15 min by estimating the magnitudes of the eddy currents at various delay times after a test gradient. The pixel shifts in a 64 × 128 echo‐planar diffusion‐weighted image with a diffusion gradient strength of 30 mT/m were reduced to less than 0.2. Magn Reson Med 47:208–212, 2002. © 2002 Wiley‐Liss, Inc.