Quantitative assessment of cavitation during therapeutic ultrasound application

The object of our investigation is the interaction of pulsed high energy ultrasound with biological tissues. The generation of transient cavities seems to be the dominant non thermal mechanism for ultrasound tissue interaction. To detect events of cavitation on line in biological tissues, we constructed two cavitation detection systems, an optical and an acoustical method. By means of the optical system called laser scattering method we were able to monitor bubble dynamics in transparent liquids in a very reliable way. We used this method to verify the interpretation of acoustic echo signals received by means of the transducer. Using the acoustical method called echo analysis we were able to prove the existence of transient cavities in biological tissues, locate the bubbles and quantify their life span