Estimation of material parameters from slow and fast shear waves in an incompressible, transversely isotropic material

Dennis J. Tweten, Ruth J. Okamoto, John L. Schmidt, Joel R. Garbow, Philip V. Bayly

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

This paper describes a method to estimate mechanical properties of soft, anisotropic materials from measurements of shear waves with specific polarization and propagation directions. This method is applicable to data from magnetic resonance elastography (MRE), which is a method for measuring shear waves in live subjects or in vitro samples. Here, we simulate MRE data using finite element analysis. A nearly incompressible, transversely isotropic (ITI) material model with three parameters (shear modulus, shear anisotropy, and tensile anisotropy) is used, which is appropriate for many fibrous, biological tissues. Both slow and fast shear waves travel concurrently through such a material with speeds that depend on the propagation direction relative to fiber orientation. A three-parameter estimation approach based on directional filtering and isolation of slow and fast shear wave components (directional filter inversion, or DFI) is introduced. Wave speeds of each isolated shear wave component are estimated using local frequency estimation (LFE), and material properties are calculated using weighted least squares. Data from multiple finite element simulations are used to assess the accuracy and reliability of DFI for estimation of anisotropic material parameters.

Original languageEnglish
Pages (from-to)4002-4009
Number of pages8
JournalJournal of Biomechanics
Volume48
Issue number15
DOIs
StatePublished - Nov 26 2015

Keywords

  • Anisotropy
  • Inversion algorithms
  • MR elastography
  • Shear waves
  • Transversely isotropic material

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