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IEEE Trans Med Imaging. 2019 Jan 25. doi: 10.1109/TMI.2019.2893369. [Epub ahead of print]

Fast Robust Dejitter and Interslice Discontinuity Removal in MRI Phase Acquisitions: Application to Magnetic Resonance Elastography.

Abstract

MRI phase contrast imaging methods that assemble slice-wise acquisitions into volumes can contain interslice phase discontinuities (IPDs) over the course of the scan from sources including unavoidable physiological activity. In magnetic resonance elastography (MRE) this can alter wavelength and tissue stiffness estimates, invalidating the analysis. We first model this behavior as jitter along the z-axis of the phase of 3D complex-valued wave volumes. A two-step image processing pipeline is then proposed that removes IPDs. First, constant slicewise phase shift is removed with a novel, non-convex dejittering algorithm. Then, regional physiological noise artifacts are removed with novel filtering of 3D wavelet coefficients. Calibration of two pipeline coefficients, the dejitter parameter α and the wavelet band highpass coefficient ωc, were first performed on a Finite Element Method brain phantom. A comparative investigation was then performed, on a cohort of 48 brain acquisitions, of four approaches to IPDs: (1) the proposed method (2) a "control" condition of neglect of IPDs (3) an anisotropic wavelet-based method (4) a method of in-plane (2D) processing. The present method showed medians of |G*| = 1873Pa for a multifrequency wave inversion centered at 40Hz which was within 6produced |G*| estimates a mean of 17method reduced the value range of the cohort against methods (3) and (4) by 29variance enhances the ability of brain MRE to predict subtler physiological changes. Our theoretical approach further enables more powerful applications of fundamental findings in noise and denoising to MRE.

PMID:
30703013
DOI:
10.1109/TMI.2019.2893369

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