IN-SITU MEASUREMENTS OF DOPPLER POWER VS. FLOW TURBULENCE INTENSITY IN RED-CELL SUSPENSIONS

Whereas previous studies have shown that ultrasonic backscatter and Do ppler power from blood are affected by flow turbulence, turbulence lev el has only been inferred from the dow Reynolds number and not directl y measured. In this study, both ultrasonic Doppler power and flow turb ulence intensity were measured in situ to quantify the relationship be tween Doppler power and flow turbulence. Three grid meshes of differen t geometries were used in a steady-flow mock loop to generate controll ed levels of flow turbulence in porcine red blood cell saline suspensi ons. Doppler power was measured by a 10-MHz PW Doppler flowmeter, and the turbulence intensity by using constant-temperature hot film anemom etry, We showed that Doppler power is affected by turbulence and hemat ocrit in a complex way. At a fixed hematocrit, Doppler power increases nonlinearly with turbulence intensity and, at fixed turbulence intens ity, Doppler power peaks at an optimal hematocrit level that increases with turbulence level. The shape factor, introduced by Lucas and Twer sky (1987) to take into account effects of shape and orientation of th e scatterers in a dense distribution of small and tenuous scatterers, was estimated by fitting the experimental data to the theoretical mode l. The results indicate that shape factor decreases with increasing tu rbulence intensity. (C) 1997 World Federation for Ultrasound in Medici ne & Biology.