Cavitation is most likely to occur under which condition?

• A. High frequency and low power
• B. High intensity and high frequency
• C. Low intensity and low frequency
• D. Low frequency and high signal amplitude

Answer: (D)

Cavitation happens when the negative pressure during the rarefaction phase is strong enough to form and then violently collapse microbubbles in tissue. This is more likely when the pressure amplitude is high and the frequency is low. Lower frequency means longer cycles, giving bubbles more time to grow during the negative phase, while a high signal amplitude increases the peak rarefaction pressure. The combination of these two factors raises the mechanical index, which is tied to cavitation risk. So, a setting with low frequency and high amplitude creates the conditions most favorable for cavitation. Scenarios with high frequency reduce bubble growth despite high amplitude, and low amplitude reduces bubble nucleation, both making cavitation less likely. Modern ultrasound practice aims to keep the mechanical index low to minimize this risk.