Which term describes the fraction of time the imaging system is transmitting relative to the entire cycle?

Which term describes the fraction of time the imaging system is transmitting relative to the entire cycle?

• A. Pulse duration
• B. Duty factor
• C. PRP
• D. PRF

Answer: (B)

The key idea is the fraction of the cycle during which the system is actively transmitting. In ultrasound, a cycle runs from the start of one transmitted pulse to the start of the next pulse. The only time energy is being sent is the pulse itself, so the fraction of time in transmit mode is the pulse duration divided by the total cycle time, which is the pulse repetition period. This ratio is known as the duty factor. For example, if a pulse lasts 2 microseconds and the interval to the next pulse is 1 millisecond, the duty factor is 2 µs / 1000 µs = 0.002, or 0.2%. This small value reflects that most of the cycle is spent listening for echoes rather than transmitting. The other terms describe different timing aspects: pulse duration is just how long the pulse lasts, the PRP is the full cycle time, and the PRF is how many pulses occur each second.

The key idea is the fraction of the cycle during which the system is actively transmitting. In ultrasound, a cycle runs from the start of one transmitted pulse to the start of the next pulse. The only time energy is being sent is the pulse itself, so the fraction of time in transmit mode is the pulse duration divided by the total cycle time, which is the pulse repetition period. This ratio is known as the duty factor. For example, if a pulse lasts 2 microseconds and the interval to the next pulse is 1 millisecond, the duty factor is 2 µs / 1000 µs = 0.002, or 0.2%. This small value reflects that most of the cycle is spent listening for echoes rather than transmitting. The other terms describe different timing aspects: pulse duration is just how long the pulse lasts, the PRP is the full cycle time, and the PRF is how many pulses occur each second.