What is the term for the formation of gas bubbles in tissue due to pressure changes during ultrasound, which can cause tissue damage?

• A. Cavitation
• B. Refraction
• C. Diffraction
• D. Attenuation

Answer: (A)

Cavitation is the formation of gas-filled bubbles in tissue when the acoustic pressure of the ultrasound wave varies, especially during the negative-pressure phase. Dissolved gases can come out of solution and form microbubbles that may oscillate or violently collapse as the wave cycles. This mechanical activity can damage cells and small vessels if the pressures are high enough, which is why cavitation is the term associated with potential tissue injury from ultrasound.

In contrast, refraction is the bending of a sound beam when it passes into a medium with a different speed. Diffraction is the spreading or bending of waves around obstacles or through apertures. Attenuation is the reduction of wave intensity as it travels due to absorption, scattering, and other losses.