Sj. Wu et al., IN-SITU MEASUREMENTS OF DOPPLER POWER VS. FLOW TURBULENCE INTENSITY IN RED-CELL SUSPENSIONS, Ultrasound in medicine & biology, 24(7), 1998, pp. 1009-1021
Citations number
29
Categorie Soggetti
Radiology,Nuclear Medicine & Medical Imaging",Acoustics
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.