A study on the feasibility of using power level for detection of turbulence and vessel differentiation in Doppler power imaging

Power Doppler imaging was used in this study to detect flow turbulence and the effect of flow shear on blood cell aggregation. Porcine RBC saline suspensions of different hematocrits were circulated in a steady flow loop containing a 318" ID tube. A mesh screen, formed by gold-plated needles was installed in the tube to generate now disturbance. It has previously been shown that flow disturbance can increase ultrasonic echogenicity and Doppler power. In this study, images were taken with a power Doppler scanner and analyzed with a digital frame grabber to investigate the influence of the turbulence on Doppler power at different hematocrits, flow speeds and positions relative to the mesh screen. The increase of intensity of the Doppler images indicates increase of Doppler power and can aid in detecting the flow disturbance behind arterial stenosis. A second study, on porcine whole blood was undertaken in a steady flow loop containing 3/16" ID tube with an additional reservoir and shunt in the loop so that the inflow and outflow speed can be varied. Doppler power imaging showed a difference of intensity between inflow and outflow as the flow (or shear) rate was changed This difference could help in discriminating small arteries and veins.