All of the following are true of normal cavitation EXCEPT which statement?

• A. Harmful bioeffects are commonly observed
• B. It is also known as inertial cavitation
• C. Only a 10% increase in pressure is needed to convert to this from table cavitation
• D. Temperatures in the thousands of degrees are created

Answer: (D)

Cavitation under ultrasound comes in two main forms: stable (normal) cavitation, where bubbles oscillate without a violent collapse, and inertial (transient) cavitation, where bubbles collapse violently. The extreme heat and pressures—thousands of degrees and very high pressures within the collapsing bubble—occur during inertial cavitation, not during stable, normal cavitation. So the statement that “temperatures in the thousands of degrees are created” is not a feature of normal cavitation, making it the exception.

In normal cavitation, energy is manifested mainly as mechanical effects like microstreaming and shear around oscillating bubbles, and the process can contribute to biological effects through those mechanical interactions. A small change in ambient pressure can push some bubbles toward collapse, which is why thresholds and transitions between stable and inertial cavitation are described in terms of pressure.