Which statement distinguishes Color Doppler from Power Doppler?

• A. Power Doppler encodes velocity and direction; Color Doppler encodes signal strength and is more sensitive to low flow but lacks direction/velocity
• B. Color Doppler encodes velocity and direction; Power Doppler encodes signal strength and is more sensitive to low flow but lacks direction/velocity
• C. Color Doppler has higher frame rate than Power Doppler
• D. Power Doppler provides velocity vectors

Answer: (B)

The main idea is how each Doppler mode represents flow information. Color Doppler uses the Doppler shift to estimate how fast blood is moving along the ultrasound beam and encodes both the speed (velocity) and the direction of flow with color (toward vs away). Power Doppler, on the other hand, measures the overall strength or energy of the Doppler signal from moving blood cells. This makes it more sensitive to detect even slow flow, but it does not provide any information about how fast the flow is or which direction it is moving. So, the statement that Color Doppler encodes velocity and direction while Power Doppler encodes signal strength and lacks direction/velocity best captures the key distinction.