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Optimal strategies for measuring diffusion in anisotropic systems by magnetic resonance imaging
Author(s) -
Jones D.K.,
Horsfield M.A.,
Simmons A.
Publication year - 1999
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/(sici)1522-2594(199909)42:3<515::aid-mrm14>3.0.co;2-q
Subject(s) - diffusion mri , anisotropy , imaging phantom , scalar (mathematics) , tensor (intrinsic definition) , diffusion , nuclear magnetic resonance , resolution (logic) , anisotropic diffusion , algorithm , physics , mathematics , computer science , mathematical analysis , magnetic resonance imaging , optics , artificial intelligence , geometry , medicine , radiology , thermodynamics
The optimization of acquisition parameters for precise measurement of diffusion in anisotropic systems is described. First, an algorithm is presented that minimizes the bias inherent in making measurements with a fixed set of gradient vector directions by spreading out measurements in 3‐dimensional gradient vector space. Next, it is shown how the set of b —matrices and echo time can be optimized for estimating the diffusion tensor and its scalar invariants. The standard deviation in the estimate of the tensor trace in a water phantom was reduced by more than 40% and the artefactual anisotropy was reduced by more than 60% when using the optimized scheme compared with a more conventional scheme for the same scan time, and marked improvements are demonstrated in the human brain with the optimized sequences. Use of these optimal schemes results in reduced scan times, increased precision, or improved resolution in diffusion tensor images. Magn Reson Med 42:515–525, 1999. © 1999 Wiley‐Liss, Inc.