STUDIES OF ACOUSTIC STREAMING IN BIOLOGICAL-FLUIDS WITH AN ULTRASOUNDDOPPLER TECHNIQUE

Acoustic streaming generated by diagnostic ultrasound fields is an imp ortant area for study both for safety reasons and because of its poten tial application as a diagnostic tool. A method of investigating strea ming in biological fluids is reported. A number of fluids were insonat ed using a 3.5 MHz weakly focused single element transducer which was driven in pulsed mode. Streaming was detected in each fluid using an a MHz continuous wave Doppler system. The maximum streaming velocity wa s obtained by spectral analysis of the Doppler signal. Using this syst em longitudinal streaming profiles were measured. At an acoustic power of 150 mW the maximum streaming velocities detected were: 9.3 cm s(-1 ) in water, 6.8 cm s(-1) in 4.5% human serum albumin (HSA) solution an d 4.9 cm s(-1) in blood, when transmission was through a water path of approximately 10 cm into a 3 cm sample of fluid. When measurements we re made in the biological fluids alone, without a water path, the maxi mum streaming velocities were reduced.