Which velocity pattern would you expect to see across a truly occluded vessel?

• A. Normal triphasic flow
• B. No color and no Doppler signals
• C. Bidirectional flow
• D. Pulsatile flow with high velocity

Answer: (B)

The main idea is that a truly occluded vessel has no blood flow through that segment. Because Doppler detects moving red blood cells, a completely blocked artery at that site will yield no Doppler signal and no color fill on color Doppler. In other words, there’s silence on both color and spectral Doppler at the occlusion itself.

This differs from a normal artery, which shows triphasic flow with characteristic velocity and direction changes; from a partially occluded or stenotic segment, where you’d see a high-velocity jet and often spectral changes; and from veins or certain pathologies where bidirectional flow or pulsatile patterns might appear. So the absence of color and Doppler signal at the site points to a true occlusion.