Damage to red blood cells induced by acoustic cavitation.

This experimental study has revealed damage to red blood cells that is quantitatively related to the acoustic pressure during irradiation with 0.75-MHz continuous-wave ultrasound, using a range of intensities comparable to those employed by ultrasonic physiotherapy equipment (0.25 to 7 W cm-2 spatial average temporal average). Damage to the red blood cells was investigated by measuring the extent of haemolysis using a UV/VIS spectrophotometer. There was a clear correlation between the amount of haemoglobin released and the intensity of harmonic emissions recorded from the sample during irradiation. The observed degree of haemolysis could not be produced by temperature rises in the absence of the sound field. This suggests that the damage was a direct result of acoustic cavitation.