The time that the sound beam is actually on is defined as which quantity?

The time that the sound beam is actually on is defined as which quantity?

• A. Duty factor
• B. Pulse repetition period
• C. Pulse repetition frequency
• D. Spatial pulse length

Answer: (A)

The key idea is timing of the pulsed ultrasound. The beam is only on during a short interval each cycle—the on-time, or pulse duration—and it’s off for the rest of the cycle. The quantity that captures how much of the cycle the beam spends on is the duty factor. Duty factor is defined as the on-time divided by the total cycle time (the pulse duration over the pulse repetition period). It’s a dimensionless value between 0 and 1, or 0% to 100%. The other terms describe different aspects: the total time for one cycle is the pulse repetition period, the number of cycles per second is the pulse repetition frequency, and spatial pulse length refers to how far the pulse travels during one pulse. So the measure that directly expresses how long the beam is actually on within each cycle is the duty factor.

The key idea is timing of the pulsed ultrasound. The beam is only on during a short interval each cycle—the on-time, or pulse duration—and it’s off for the rest of the cycle. The quantity that captures how much of the cycle the beam spends on is the duty factor. Duty factor is defined as the on-time divided by the total cycle time (the pulse duration over the pulse repetition period). It’s a dimensionless value between 0 and 1, or 0% to 100%. The other terms describe different aspects: the total time for one cycle is the pulse repetition period, the number of cycles per second is the pulse repetition frequency, and spatial pulse length refers to how far the pulse travels during one pulse. So the measure that directly expresses how long the beam is actually on within each cycle is the duty factor.