期刊
MAGNETIC RESONANCE IN MEDICINE
卷 71, 期 3, 页码 1312-1323出版社
WILEY
DOI: 10.1002/mrm.24773
关键词
diffusion MRI; gradient nonlinearity; ADC systematic bias
资金
- National Institutes of Health (NIH/NCI) [P01-CA85878, SAIC 29XS161, U01-CA166104]
PurposeGradient 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. MethodsAll-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. ResultsSpatial 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. ConclusionsThe 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. (c) 2013 Wiley Periodicals, Inc.
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