HIGH-FREQUENCY ULTRASONIC BACKSCATTER FROM ERYTHROCYTE SUSPENSION

Previous studies have shown that ultrasonic backscattering from red bl ood cells suspended in saline is proportional to the fourth power of f requency for frequencies below 15 MHz, as predicted by Rayleigh scatte ring theory. Recently, we have extended the measurements up to 30 MHz, because scattering of ultrasound by red blood cells may no longer be negligible at these frequencies and can affect, to a great degree, the operation of intravascular imaging devices. The experimental results show that the fourth power dependence on frequency of the backscatteri ng coefficient for porcine erythrocytes suspended in saline solution a ppears to be valid up to 30 MHz. To confirm this, backscattering cross -section of porcine red cells was computed as a function of frequency using the T-matrix method. Since at higher frequencies the shape of th e scatterers may also play a significant role, its effect was investig ated by treating the red cell as a sphere, a disc, and a biconcave dis c of the same volume. Good agreement was obtained between the experime ntal and theoretical results.