Quantitative investigation of acoustic streaming in blood

Acoustic streaming was used to distinguish unclotted blood from clotted blood or tissue. The sensitivity of detection depends on the streaming velocity that is determined by the applied acoustic intensity, the attenuation and viscosity of the fluid, the sound speed, and a geometric factor that depends on the local boundaries. The effect of this geometric factor on streaming detection was quantitatively investigated. Streaming was generated in blood with a HIFU transducer in four circular tubes with various diameters. The streaming velocity was measured using real-time color Doppler imaging. The results shows that the streaming velocity increases with increasing tube size, but eventually reaches a constant value, when the tube diameter is approximately 10 times larger than that of the beam.