This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
The intensity of colour in Doppler is determined by: 
Select and explain. 
A. Direction flow, B. Velocity of flow, C. Strength of returning echo, D. None of the above
B: Velocity of flow
Answer: B: Velocity of flow 
Explanation: In a Colour Doppler: Colours are used to represent direction of flow towards & away from the transducer; usually blue is towards & red is away from transducer Shades (intensity of colour) represent v elocity of flow; the paler shades representing higher velocity * Power Doppler: Is good for showing areas of flowing blood, paicularly when it is moving slowly or in small vessels; but at the expense of losing directional & velocity information.