Reflected shear wave imaging of atherosclerosis

Atherosclerotic risk stratification may be improved by identifying soft lipid-rich or necrotic plaque regions, fibrous caps, calcium deposits, and other plaque components with disparate mechanical impedances. Mechanical impedance interfaces reflect acoustic radiation force (ARF)-induced shear waves. For the purpose of detecting these shear wave reflections, we developed a novel method as an adjunct to conventional ARFI called reflected shear wave imaging (RSWI). RSWI identifies shear wave reflections in tissue as inflections in 1D axial displacement profiles measured in the ARF region of excitation. This technique generates parametric images of shear wave reflections (SWRs) using only conventional 2D ARFI data sets. RSWI was performed on three familial hypercholesterolemic (FH) porcine iliac arteries, two ex vivo and one in vivo. Our results suggest that RSWI improves identification of soft, lipid-rich or necrotic plaque regions near fibrous cap, calcium, and collagen deposits. RSWI supports shear wave velocity (SWV) estimation, which may be useful for quantitative ARF-based imaging.