Viscoelastic characterization of elliptical mechanical heterogeneities using a semi-analytical shear-wave scattering model for elastometry measures

Abstract

This paper presents a semi-analytical model of shear wave scattering by a viscoelastic elliptical structure embedded in a viscoelastic medium, and its application in the context of dynamic elastography imaging. The commonly used assumption of mechanical homogeneity in the inversion process is removed introducing a priori geometrical information to model physical interactions of plane shear waves with the confined mechanical heterogeneity. Theoretical results are first validated using the finite element method for various mechanical configurations and incidence angles. Secondly, an inverse problem is formulated to assess viscoelastic parameters of both the elliptic inclusion and its surrounding medium, and applied in vitro to characterize mechanical properties of agar-gelatin phantoms. The robustness of the proposed inversion method is then assessed under various noise conditions, biased geometrical parameters and compared to direct inversion, phase gradient and time-of-flight methods. The proposed elastometry method appears reliable in the context of estimating confined lesion viscoelastic parameters.

Acoustic radiation force induced resonance elastography of coagulating blood: theoretical viscoelasticity modeling andex vivoexperimentation

“…In such cases, it may be possible to adapt ARFIRE to consider ellipsoids. Shear wave scattering by elliptical structures was previously investigated in the case of plane incident shear waves (Montagnon et al 2013). This may constitute a framework to adapt ARFIRE for future works.…”

Ultrasound viscoelasticity assessment using an adaptive torsional shear wave propagation method

“…The maximum amplitude of shear waves was observed between 60 and 150 Hz with a peak at 100 Hz in case of phantom #1, between 100 and 200 Hz with a peak at 150 Hz for phantom #2, and between 150 and 300 Hz with a peak at 200 Hz for phantom #3. benchmark methods; however discrepancies were more significant for loss moduli. This may be explained by the small size of inclusions relative to selected wavelength, 49 which affected the estimation of displacements within mimicking lesions and more importantly the estimation of the loss modulus compared to G ′ , as also noticed in Refs. 25 and 49.…”

Correlation-based full-waveform shear wave elastography

“…Moreover, the push amplitude is not precisely known, which may result in failure of accurate reconstruction. Other global techniques such as semi-analytical approaches ( Hadj-Henni et al 2008 , Montagnon et al 2013 , 2014 , Bernard and Cloutier 2017 ) provide good results with less computational cost, but are limited to simple geometries and cannot provide elasticity maps with arbitrary heterogeneities.…”