Comparison of techniques for estimating shear-wave velocity in arterial wall using shear-wave elastography - FEM and phantom study

Shear-wave elastography (SWE) enables noninvasive and quantitative evaluation of the mechanical properties of human soft tissue. Generally, shear wave velocity (C-S) can be estimated using the time-of-flight method (TM). Young's modulus is then calculated directly from the estimated C-S. However, because shear waves in thin-layered media (e.g., arterial walls) propagate as guided waves, C-S cannot be accurately estimated using the general TM. To overcome this problem, the Lamb-theory-based method (LM) was recently proposed. In this study, we performed both experimental and finite-element (FE) analyses to evaluate the advantage of LM over TM. In FE analysis, we investigated why the general TM is ineffective for thin-layered media. In phantom experiments, C-S results estimated using the two methods were compared for 1.5% and 2% agar plate and tube phantoms. The results indicated good agreement between LM (plate phantoms 5.0m/s for 1.5% agar and 7.2m/s for 2% agar; tube phantoms 5.3m/s for 1.5% agar and 7.3m/s for 2% agar) and SWE measurements (bulk phantoms 5.3m/s +/- 0.27 for 1.5% agar and 7.3m/s +/- 0.54 for 2% agar).