Comparison of the acoustic streaming in amniotic fluid and water in medical ultrasonic beams.

AIM

Acoustic streaming in amniotic fluid has been investigated under a variety of conditions relevant to the diagnostic use of ultrasound.

METHOD

An ultrasonic Doppler method has been used for measurement. Streaming velocities have been compared with those generated in water for the same exposure conditions. Beams were generated by laboratory equipment simulating beams from clinical systems. The fluids were insonated IN VITRO using 3.5 MHz, 5 MHz and 7.5 MHz transducers in continuous wave (CW) and pulsed mode.

RESULTS

Acoustic streaming was measured in both amniotic fluid and water at the power levels 50 mW and 140 mW. Enhancement of velocities due to non-linear effects in high amplitude pulses was demonstrated for amniotic fluid as well as for water. The potential and limitations of present numeric methods for the prediction of acoustic streaming were explored.

CONCLUSION

Pulsed ultrasound caused similar streaming velocities in amniotic fluid and water while continuous wave beams induced significantly faster streaming in amniotic fluid than in water.