Echogenicity of sonographic contrast media at variable shear rates and concentrations

S onogr~phic contrast media are used to increase signal-to-noise ratio in clinicai sonography. Enhanced blood echogenicity is usually achieved by intravenous injection of various solutions with stabilized microbubbles, micropartides, or albumin microspheres [1], although other types of sonographic contrast media also have been developed. The increased echogenicity depends greatly on the concentration of the solution of contrast material. Although the backscatter coefficient is linearly proportional to scatterer concentration at low concentrations [2], it has been shown that above a certain concentration of sonographic contrast medium, the backscattered ultrasonic intensity decreases [3]. It remains unclear whether this is true for variable shear rate and whether variable flow velocity would affect the echogenicity of a bolus of sonographic contrast medium in blood. In this study we investigated the effect of variable shear rates on the echogenicity of sonographic contrast media in blood.