What information does Doppler shift provide?

What information does Doppler shift provide?

• A. Velocity
• B. Flow
• C. Cardiac output
• D. Speed

Answer: (A)

Doppler shift tells you how fast blood is moving along the ultrasound beam, including direction. The frequency difference between transmitted and received waves is proportional to the axial velocity of the moving cells (v cos θ), so you get velocity with a sign that shows whether the flow is toward or away from the transducer. This is why Doppler is used to assess how fast blood is moving in vessels. It doesn’t directly give flow (volume per time) because that would require knowing the cross‑sectional area and the velocity profile across that area. It also isn’t simply speed in the everyday sense, since velocity includes direction and the Doppler shift conveys that directional information.

Doppler shift tells you how fast blood is moving along the ultrasound beam, including direction. The frequency difference between transmitted and received waves is proportional to the axial velocity of the moving cells (v cos θ), so you get velocity with a sign that shows whether the flow is toward or away from the transducer. This is why Doppler is used to assess how fast blood is moving in vessels.

It doesn’t directly give flow (volume per time) because that would require knowing the cross‑sectional area and the velocity profile across that area. It also isn’t simply speed in the everyday sense, since velocity includes direction and the Doppler shift conveys that directional information.