P3B-5 Investigation of Doppler Ultrasound Velocity-Based Indices for Carotid Plaque Ulcerations Using In Vitro Flow Models

Previous studies have shown that the presence of surface irregularities, known as ulcerations, in carotid plaque is an independent risk factor for stroke. Doppler ultrasound (DUS) has not been implemented as a diagnostic tool for carotid plaque ulcerations. We employed carotid bifurcation flow models that differed only with respect to the presence of ulceration to study the sole effect of surface roughness on Doppler-derived flow parameters. A pair of in vitro flow models were fabricated, each based on an idealized carotid bifurcation geometry of 50% eccentric stenosis. For one of these models, a 2-mm diameter hemi-spherical ulcer was incorporated at the level of the apex on the non-flow divider wall. DUS measurements were acquired using a 4-MHz probe and 1.0-mm sample volume, delivering 4-D Doppler velocity data sets with 11.7-ms temporal resolution and 1.3-cm s-1 velocity resolution. Velocity data was analyzed for several indices. Teflon flow phantom facilitated both the direct machining of realistic vessel geometries with varying surface roughness (plusmn 0.05-mm) and compatibility with Doppler ultrasound. The small 2-mm hemi-spherical ulcer did not introduce any significant differences in downstream velocity patterns, as indicated by turbulence intensity, peak velocity, or mean velocity. We have developed a DUS technique to characterize carotid plaque ulceration, and have shown that DUS velocity-based measurements of turbulence intensity are feasible with conventional systems. This approach will allow us to extend our paired comparison studies to other ulcer shapes and sizes