2086303 High Frame Rate Ultrasound Can Dynamically Visualize Fast-Changing Vector Flow Fields in The Carotid Bifurcation

Abstract

Our aim is to track spatiotemporal variations in cardiovascular flow fields by using high frame rate ultrasound to derive flow vectors at millisecond time resolution. Achieving such diagnostic capability is practically important because it may foster clinical detection of abnormal vascular conditions. So far, complex flow patterns have not been visualized lucidly using color Doppler imaging due to flaws like Doppler angle ambiguity and limited time resolution. New solutions are needed. We have devised a new technique called vector projectile imaging (VPI) to facilitate flow vector estimation over the entire field of view at fine temporal resolution. First, using a reconfigurable ultrasound scanner (SonixTouch) and a linear array, slow-time sampling was performed using a plane wave firing approach, and it was carried out from three different angles (-10, 0, +10 deg) at kHz-range PRF. This allowed parallel acquisition of Doppler information over all pixel positions. No contrast agent was used in the process. For each pulsing event, three angle steered frames (-10, 0, +10 deg) were beamformed, and these were used to calculate the flow vector at every pixel position in the field of view using multi-angle Doppler analysis principles. Performance analysis was conducted using carotid bifurcation models with well-characterized pulsatile flow conditions. Both healthy and stenotic vasculatures were included in the analysis. Using VPI, we have successfully tracked time-varying vector flow fields inside the carotid arteries. Using a 416 fps frame rate (2.4 ms time resolution), the main transit path of blood flow in a healthy bifurcation was mapped accurately. In a diseased case with 50% eccentric stenosis at the entrance to the internal carotid artery, VPI effectively highlighted the high velocity jet emerging at the stenosis site, curvy transit path downstream from the stenosis, and significant recirculatory flow in the carotid bulb. Corresponding cineloops will be shown at the meeting. Complex flow fields in the cardiovascular system can be mapped through ultrasound imaging innovations. This can help expand ultrasound’s present role in cardiovascular diagnostics.