Sampling and reconstruction effects due to motion in diffusion-weighted interleaved echo planar imaging.
MAGN RESON MED
101 - 109.
Subject motion during diffusion-weighted interleaved echo-planar imaging causes k-space offsets which lead to irregular sampling in the phase-encode direction. For each image, the k-space shifts are monitored using 2D navigator echoes, and are shown to lead to a frequent violation of the Nyquist condition when an ungated sequence is used on seven subjects. Combining data from four repeat acquisitions allows the Nyquist condition to be satisfied in all but 1% of images. Reconstruction of the irregularly-sampled data can be performed using a matrix inversion technique, The repeated acquisitions make the inversion more stable and additionally improve the signal-to-noise ratio. The resultant isotropic diffusion-weighted images and average apparent diffusion coefficient (ADC) maps show high resolution and enable clear localization of a stroke lesion, Residual ADC artifacts with a slow spatial variation are observed and assumed to originate from non-rigid pulsatile brain motion. (C) 2000 Wiley-Liss, Inc.
|Title:||Sampling and reconstruction effects due to motion in diffusion-weighted interleaved echo planar imaging|
|Keywords:||irregular sampling, Nyquist, diffusion-weighted imaging, echo planar imaging, motion, GRIDDING ALGORITHM, FOURIER INVERSION, NAVIGATOR ECHOES, IN-DIFFUSION, ACUTE STROKE, BRAIN, MRI, ARTIFACTS, PERFUSION, HUMANS|
|UCL classification:||UCL > School of Life and Medical Sciences
UCL > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Engineering Science
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