A color Doppler appearance shows the ICA directed toward the transducer with blue color; what does this indicate about flow?

• A. Reversal flow
• B. Forward flow due to orientation
• C. No flow
• D. Turbulent flow

Answer: (B)

In color Doppler, direction of flow is defined relative to the transducer and the color map being used. The internal carotid artery segment in question runs toward the transducer, so blood moving in that direction is considered forward flow along the vessel. Seeing blue in this setup simply reflects the color mapping for flow toward the transducer on that system, not a sign of reversal or no flow. Therefore this represents forward flow. If the flow were reversing, you’d see the color associated with flow away from the transducer; no flow would produce little to no color signal, and turbulent flow would show a mosaic of colors rather than a uniform hue.