Guided waves in pre-stressed hyperelastic plates and tubes: Application to the ultrasound elastography of thin-walled soft materials

Abstract

In vivo measurement of the mechanical properties of thin-walled soft tissues (e.g., mitral valve, artery and bladder) and in situ mechanical characterization of thinwalled artificial soft biomaterials in service are of great challenge and difficult to address via commonly used testing methods. Here we investigate the properties of guided waves generated by focused acoustic radiation force in immersed pre-stressed plates and tubes, and show that they can address this challenge. To this end, we carry out both (i) a theoretical analysis based on incremental wave motion in finite deformation theory and (ii) finite element simulations. Our analysis leads to a novel method based on the ultrasound elastography to image the elastic properties of prestressed thin-walled soft tissues and artificial soft materials in a non-destructive and non-invasive manner. To validate the theoretical and numerical solutions and demonstrate the usefulness of the corresponding method in practical measurements, we perform (iii) experiments on polyvinyl alcohol cryogel phantoms immersed in water, using the Verasonics V1 System equipped with a L10-5 transducer. Finally, potential clinical applications of the method have been discussed.

Parasternal Versus Apical View in Cardiac Natural Mechanical Wave Speed Measurements

“…Its resulting phase speed plots are visualized in Fig. 5 and correspond well with the theoretical dispersion curves of the A-and S-modes for an inviscid plate submerged in water as described by Li et al [32]. For the transversal body force [ Fig.…”

“…We will not consider SH modes, as the particle motion of these modes is along the plate surface perpendicular to the propagation direction [31] and is, therefore, probably hard to detect in cardiac parasternal and apical views. The A-and S-mode guided waves are characterized by different dispersion curves, as described in [31], [32], and [36]. S-modes are regularly referred to as longitudinal, and A-modes as transversal SWs because of the dominant particle motion with respect to the propagation direction in the centerline of the medium.…”

“…No bandpass filter was applied to the M-panels before computing the phase speeds. The accuracy and correctness of the numerical phase speed plots were visually verified by comparing them to the theoretical dispersion curves of A 0 -and S 0 -modes in a nonstretched inviscid plate submerged in water as described in [32].…”

“…Different types of forces are used; a TBF, an LBF, and a TCF. Also, theoretical dispersion curves for a nonstretched inviscid plate submerged in water with a shear modulus of 16 kPa, a density of 1050 kg/m 3 and a thickness of 10 mm[32] are depicted in the figure.…”

Acoustoelasticity Analysis of Transient Waves for Non-Invasive In Vivo Assessment of Urinary Bladder

“…Li et al . 21 have recently shown that changes in nonlinearity parameter A can be detected via analysis of transient guided waves in pre-stressed medium. Using a simplistic cumulative stress-strain model, an earlier ex vivo study showed that nonlinear parameter changes drastically in aberrant tissue compared to the intact ones 22 .…”