Pulsed ultrasound versus continuous ultrasound: which feature distinguishes pulsed mode?

• A. It delivers energy in pulses with lower average intensity.
• B. It delivers energy in pulses with higher average intensity.
• C. It uses continuous wave to maximize heating.
• D. It uses direct current.

Answer: (A)

Pulsed ultrasound is defined by energy being emitted in short bursts with brief off periods, so the duty cycle is less than one. This lowers the average intensity over time, even if the peak intensity within each pulse is similar or high. The off time reduces heating, which is why pulsed mode is used when mechanical effects (like microstreaming and cavitation) are desired without excessive tissue heating. Continuous ultrasound, on the other hand, delivers energy without interruptions, resulting in a higher average intensity and more heating. The idea of using direct current isn’t applicable to ultrasound, which uses alternating current to drive the transducer.