Duty factor is defined as the ratio of what?

Duty factor is defined as the ratio of what?

• A. Pulse duration to pulse repetition period
• B. Pulse duration to total cycle time
• C. Pulse repetition period to pulse duration
• D. Power to energy

Answer: (A)

Duty factor describes how much of each ultrasound cycle the transducer is actually transmitting. It is defined as the pulse duration (the on-time of the pulse) divided by the pulse repetition period (the time from the start of one pulse to the start of the next). So the duty factor equals PD divided by PRP. Since PRP is the reciprocal of PRF, you can also write DF = PD × PRF. This ratio is dimensionless and ranges from 0 to 1; a higher duty factor means more of the cycle is spent emitting, delivering more energy per second and potentially more heating. In practice, diagnostic ultrasound uses relatively small duty factors to keep exposure safe. Note that using total cycle time yields the same ratio because the total cycle time is the interval between the starts of successive pulses.

Duty factor describes how much of each ultrasound cycle the transducer is actually transmitting. It is defined as the pulse duration (the on-time of the pulse) divided by the pulse repetition period (the time from the start of one pulse to the start of the next). So the duty factor equals PD divided by PRP. Since PRP is the reciprocal of PRF, you can also write DF = PD × PRF. This ratio is dimensionless and ranges from 0 to 1; a higher duty factor means more of the cycle is spent emitting, delivering more energy per second and potentially more heating. In practice, diagnostic ultrasound uses relatively small duty factors to keep exposure safe. Note that using total cycle time yields the same ratio because the total cycle time is the interval between the starts of successive pulses.