Quantitative effects of off-resonance related distortion on brain mechanical property estimation with magnetic resonance elastography
NMR in Biomedicine
Off-resonance related geometric distortion can impact quantitative MRI techniques, such as magnetic resonance elastography (MRE), and result in errors to these otherwise sensitive metrics of brain health. MRE is a phase contrast technique to determine the mechanical properties of tissue by imaging shear wave displacements and estimating tissue stiffness through inverse solution of Navier's equation. In this study, we systematically examined the quantitative effects of distortion and corresponding correction approaches on MRE measurements through a series of simulations, phantom models, and in vivo brain experiments. We studied two different k-space trajectories, echo-planar imaging and spiral, and we determined that readout time, off-resonance gradient strength, and the combination of readout direction and off-resonance gradient direction, impact the estimated mechanical properties. Images were also processed through traditional distortion correction pipelines, and we found that each of the correction mechanisms works well for reducing stiffness errors, but are limited in cases of very large distortion. The ability of MRE to detect subtle changes to neural tissue health relies on accurate, artifact-free imaging, and thus off-resonance related geometric distortion must be considered when designing sequences and protocols by limiting readout time and applying correction where appropriate.
This is the peer reviewed version of the following article: McIlvain, G, McGarry, MDJ, Johnson, CL. Quantitative effects of off-resonance related distortion on brain mechanical property estimation with magnetic resonance elastography. NMR in Biomedicine. 2022; 35( 1):e4616. doi:10.1002/nbm.4616, which has been published in final form at https://doi.org/10.1002/nbm.4616. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.
brain, distortion, magnetic resonance elastography, off-resonance, viscoelasticity
McIlvain, G, McGarry, MDJ, Johnson, CL. Quantitative effects of off-resonance related distortion on brain mechanical property estimation with magnetic resonance elastography. NMR in Biomedicine. 2022; 35( 1):e4616. doi:10.1002/nbm.4616