Experimental study on the effect of the cylindrical vessel geometry on arterial shear wave elastography

Shear wave elastography (SWE) is a promising technique for cardiovascular diagnostics including the assessment of arterial stiffness, as it could pick up pressure-induced stiffening of arteries and be sensitive to arterial anisotropy. Previous studies demonstrated the feasibility of SWE in arteries and tissue-mimicking tubular phantoms but all relied on the longitudinal view. Given the circumferential orientation of collagen fibers, investigating arteries in the cross-sectional plane might be more relevant. We therefore investigated and compared SWE in the cross-sectional and longitudinal views using a tissue-mimicking (poly)vinyl alcohol (PVA) tubular phantom. The phantom was pressurized at three different pressure levels of 0mmHg, 30mmHg and 60mmHg to investigate the influence of the changing geometry and curvature on the shear wave propagation. The interaction and comparison between the longitudinally and circumferentially propagating shear wave fronts was studied as well as the influence on shear wave speed (SWS) assessment via a time-of-flight estimation algorithm. SWS as derived from the mechanical assessment of the PVA tissue via pressure-diameter curves and actual SWE measurements gave similar results: 3.8m/s based on the pressure-diameter data versus SWS values ranging from 4.19±0.34m/s to 4.33±0.32m/s in the longitudinal view, and from 4.09±0.65m/s to 5.29±0.52m/s in the cross-sectional view. However, further numerical modeling is necessary to understand the interaction and nature of the circumferential and longitudinal shear waves.