Shear wave elastography for the characterization of arterial wall stiffness: A thin-plate phantom and ex vivo aorta study

Ultrasound shear wave elastography (SWE) is an emerging technique for characterizing local arterial stiffness - a known indicator for vascular health. However, the implications due to vascular anatomy and tissue environment are still relatively under-examined. Using polyvinyl alcohol (PVA) based tissue mimicking phantoms, this study assessed the current signal processing framework in demonstrating the challenges due to the wave dispersion (at the medium thicknesses smaller than the shear wavelength) and wave interference at the interface of different media which cause biased stiffness estimations. Hence, 5% PVA and 10% PVA phantoms of varying thicknesses (from 1 to 10 mm) were imaged when placed in water and in 5% PVA and 10% PVA phantoms. Our results confirmed that shear wave propagation was thickness dependent (315% underestimation in 10% PVA). The shear wave velocity was shown to be influenced by the surrounding media with a 150% overestimation in 5% PVA surrounded by 10% PVA. It also demonstrated a key limitation of arterial SWE in that the current phase velocity estimation does not provide accurate SWV estimation, requiring optimization for addressing wave interference.