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Analysis and correction of gradient nonlinearity bias in apparent diffusion coefficient measurements
Author(s) -
Malyarenko Dariya I.,
Ross Brian D.,
Chenevert Thomas L.
Publication year - 2014
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.24773
Subject(s) - diffusion mri , anisotropy , nonlinear system , diffusion , tensor (intrinsic definition) , residual , fractional anisotropy , anisotropic diffusion , mathematics , physics , nuclear magnetic resonance , statistical physics , algorithm , optics , magnetic resonance imaging , medicine , quantum mechanics , pure mathematics , radiology
Purpose Gradient nonlinearity of MRI systems leads to spatially dependent b ‐values and consequently high non‐uniformity errors (10–20%) in apparent diffusion coefficient (ADC) measurements over clinically relevant field‐of‐views. This work seeks practical correction procedure that effectively reduces observed ADC bias for media of arbitrary anisotropy in the fewest measurements. Methods All‐inclusive bias analysis considers spatial and time‐domain cross‐terms for diffusion and imaging gradients. The proposed correction is based on rotation of the gradient nonlinearity tensor into the diffusion gradient frame where spatial bias of b ‐matrix can be approximated by its Euclidean norm. Correction efficiency of the proposed procedure is numerically evaluated for a range of model diffusion tensor anisotropies and orientations. Results Spatial dependence of nonlinearity correction terms accounts for the bulk (75–95%) of ADC bias for FA = 0.3–0.9. Residual ADC non‐uniformity errors are amplified for anisotropic diffusion. This approximation obviates need for full diffusion tensor measurement and diagonalization to derive a corrected ADC. Practical scenarios are outlined for implementation of the correction on clinical MRI systems. Conclusions The proposed simplified correction algorithm appears sufficient to control ADC non‐uniformity errors in clinical studies using three orthogonal diffusion measurements. The most efficient reduction of ADC bias for anisotropic medium is achieved with non‐lab‐based diffusion gradients. Magn Reson Med 71:1312–1323, 2014. © 2013 Wiley Periodicals, Inc.