A versatile and experimentally validated finite element model to assess the accuracy of shear wave elastography in a bounded viscoelastic medium

Abstract

The feasibility of shear wave elastography (SWE) in arteries for cardiovascular risk assessment remains to be investigated as the artery's thin wall and intricate material properties induce complex shear wave (SW) propagation phenomena. To better understand the SW physics in bounded media, we proposed an in vitro validated finite element model capable of simulating SW propagation, with full flexibility at the level of the tissue's geometry, material properties, and acoustic radiation force. This computer model was presented in a relatively basic set-up, a homogeneous slab of gelatin-agar material (4.35 mm thick), allowing validation of the numerical settings according to actual SWE measurements. The resulting tissue velocity waveforms and SW propagation speed matched well with the measurement: 4.46 m/s (simulation) versus 4.63 ± 0.07 m/s (experiment). Further, we identified the impact of geometrical and material parameters on the SW propagation characteristics. As expected, phantom thickness was a determining factor of dispersion. Adding viscoelasticity to the model augmented the estimated wave speed to 4.58 m/s, an even better match with the experimental determined value. This study demonstrated that finite element modeling can be a powerful tool to gain insight into SWE mechanics and will in future work be advanced to more clinically relevant settings.

A finite element model to study the effect of tissue anisotropy onex vivoarterial shear wave elastography measurements

“…The body force in Abaqus was imposed in a form of the 2D Gaussian shape functions calculated at each depth throughout the thickness of the model (Caenen et al, 2015).…”

“…This approach allows to have full control over the arterial architecture, mechanical properties and the excited ARF (Lee et al, 2012;Palmeri et al, 2005;Caenen et al, 2015). By varying the fibre orientation and the probe orientation in the numerical model, we will verify whether elasticity variations due to stretch-induced stiffening are indeed picked up most easily when the transducer is (close to) parallel to the fibre orientation, i.e.…”

Effect of Ultrafast Imaging on Shear Wave Visualization and Characterization: An Experimental and Computational Study in a Pediatric Ventricular Model

“…As actual SWE experiments do not provide access to a ground truth for imaged shear wave propagation, a multiphysics modeling approach combining computational solid mechanics (CSM) of the shear wave propagation [20][21][22] with ultrasound (US) modeling of ultrafast imaging was used for this purpose. The resulting wave mechanics from CSM provided the true mechanical shear wave propagation whereas the virtual images represented the imaged shear wave propagation.…”

Assessment of the arterial stiffness in patients with acute ischemic stroke using longitudinal elasticity modulus measurements obtained with Shear Wave Elastography.

“…This high temporal resolution makes it possible to measure the arterial wall stiffness due to the remote palpation carried out by shear waves [7]. SWE has been used to quantify the elasticity modulus of a normal carotid vessel wall through the cardiac cycle [8].…”