What does continuous ultrasound duty cycle mean?

• A. Pulsed Ultrasound- 20%; 50%; on/off
• B. US is on continuously; 100% duty cycle
• C. Pulsed Ultrasound- 20% or 50%
• D. On/off cycling within pulsed mode

Answer: (B)

Duty cycle for ultrasound therapy is the fraction of time the device is emitting energy during each treatment cycle. When ultrasound is continuous, the transducer stays on without interruptions, so the duty cycle is 100%. That means there is no off time in the cycle. In contrast, pulsed modes deliver energy in bursts with off intervals, such as 20% or 50% duty cycles, where on-time is a portion of the cycle and off-time follows. The more the duty cycle approaches 100%, the more heating occurs in the tissue; lower duty cycles reduce heating and emphasize non-thermal or mechanical effects. So continuous ultrasound means energy is on continuously, i.e., a 100% duty cycle.