In color Doppler imaging, ensemble length is equivalent to which of the following?

In color Doppler imaging, ensemble length is equivalent to which of the following?

• A. Packet size
• B. Persistence
• C. Pulse repetition frequency
• D. Color threshold

Answer: (A)

Ensemble length is the number of successive transmissions used to calculate a single color Doppler velocity for each sample. This is the same idea as packet size: you’re grouping a certain number of pulses (data points) to form one velocity estimate. Using more pulses in the ensemble improves the signal-to-noise ratio and makes the velocity estimate more stable, but it also lowers frame rate because each color sample requires more pulses. Persistence is about how long color is displayed over time, not how many pulses are combined for one estimate. Pulse repetition frequency is the rate at which pulses are sent, affecting range and maximum measurable velocity, not the ensemble length. Color threshold is a display gate, separate from how many samples are averaged.

Ensemble length is the number of successive transmissions used to calculate a single color Doppler velocity for each sample. This is the same idea as packet size: you’re grouping a certain number of pulses (data points) to form one velocity estimate. Using more pulses in the ensemble improves the signal-to-noise ratio and makes the velocity estimate more stable, but it also lowers frame rate because each color sample requires more pulses. Persistence is about how long color is displayed over time, not how many pulses are combined for one estimate. Pulse repetition frequency is the rate at which pulses are sent, affecting range and maximum measurable velocity, not the ensemble length. Color threshold is a display gate, separate from how many samples are averaged.