The percentage of time that the ultrasound is being transmitted is called what?

• A. Duty factor
• B. Pulse repetition frequency
• C. Depth gain compensation
• D. Echo arrival time

Answer: (A)

Duty factor is the fraction of time the transducer is actively transmitting during one cycle of pulsed ultrasound. It’s calculated as the transmit time divided by the total cycle time (transmit plus receive). Because the beam is pulsed, most of the cycle is spent listening rather than transmitting, so the duty factor is usually a small percentage. This value affects the average power and potential tissue heating: a higher duty factor means more of the cycle is spent sending energy, increasing average intensity. The other terms relate to different aspects: pulse repetition frequency is how many pulses occur each second, depth gain compensation adjusts amplification with depth, and echo arrival time is the time it takes for echoes to return to estimate depth.