In colour Doppler ultrasound, the colour coding convention for direction of blood flow is:

• A Blue = arterial (oxygenated), Red = venous
• B Red = fast flow, Blue = slow flow
• C Blue = arterial, Red = turbulent flow
• D Red = flow towards the transducer, Blue = flow away from the transducer ✓

Explanation

In colour Doppler ultrasound, the colour encodes the direction of flow relative to the transducer using the BART convention (Blue Away, Red Towards). It does NOT distinguish arterial from venous blood or oxygenated from deoxygenated blood. The colour hue/brightness may indicate velocity (brighter = faster), but the colour itself (red/blue) only indicates direction. Aliasing occurs when flow velocity exceeds the Nyquist limit.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.