The Effect of Kinetic Properties on Statistical Variations of Ultrasound Signals Backscattered from Flowing Blood

Yet very little is known about the effect of "black hole" (BH) phenomenon on backscattering signal statistics under the laminar flow. To further explore this issue, measurements were performed from the porcine blood (with hematocrits of 20 and 50%) circulating in a mock flow loop under various steady flows at velocities ranged from 15 to 122 mm/s using a 10 MHz ultrasonic transducer. Results showed that the BH was apparent for the 50% blood flowing at a low velocity. The BH tended to be decreased with the increase of flow velocity and that it was hardly observed from the 20% blood. The probability density function of signals backscattered from blood tended to distribute as pre-Rayleigh statistics and the Nakagami parameter was less than 1. The spatial distribution of red cell aggregation in the flow tube is a predominant factor leading to statistical variations of ultrasonic backscattering in the flowing blood.