Which explains why the frame rate decreases when color Doppler is activated?

• A. Longer color Doppler pulse length
• B. More focal zones when color is active
• C. The system memory resources are challenged
• D. More pulses are fired on each line of sight

Answer: (D)

Frame rate is limited by how fast each scan line can be acquired. When color Doppler is turned on, the system needs to send multiple pulses along each line to sample velocity information. That adds time per line, so fewer lines can be scanned each second, which lowers the frame rate. In other words, the Doppler data requires extra pulses per line (an ensemble), and more pulses means longer line acquisition and slower overall imaging. The other factors can influence speed, but the essential reason the frame rate drops is the increased number of pulses fired on each line to obtain Doppler information.