Which statement describes the duty factor in pulsed ultrasound?

Which statement describes the duty factor in pulsed ultrasound?

• A. Fraction of time the transducer is transmitting
• B. Pulse duration
• C. PRF
• D. Period

Answer: (A)

The duty factor is the fraction of time the transducer is actively emitting during one ultrasound cycle. It’s calculated as the pulse duration divided by the total cycle time (the period). Conceptually, it tells you how much of each cycle is spent sending energy versus being silent. A higher duty factor means more energy is delivered and potential heating increases. For example, if a pulse lasts 5 microseconds and the full cycle lasts 100 microseconds, the duty factor is 5/100 = 0.05 (5%). This is why the description “fraction of time transmitting” best fits: the other terms describe the pulse length (pulse duration), the rate of pulses (PRF), or the full cycle length (period), not the fraction of time used.

The duty factor is the fraction of time the transducer is actively emitting during one ultrasound cycle. It’s calculated as the pulse duration divided by the total cycle time (the period). Conceptually, it tells you how much of each cycle is spent sending energy versus being silent. A higher duty factor means more energy is delivered and potential heating increases.

For example, if a pulse lasts 5 microseconds and the full cycle lasts 100 microseconds, the duty factor is 5/100 = 0.05 (5%).

This is why the description “fraction of time transmitting” best fits: the other terms describe the pulse length (pulse duration), the rate of pulses (PRF), or the full cycle length (period), not the fraction of time used.