Which Doppler modality is highly sensitive to low-velocity flow but does not provide velocity information?

Which Doppler modality is highly sensitive to low-velocity flow but does not provide velocity information?

• A. Gray scale imaging
• B. Pulsed Doppler
• C. Power Doppler
• D. Continuous Wave Doppler

Answer: (C)

Power Doppler detects flow by measuring the strength (power) of the Doppler signal rather than its frequency shift. This makes it highly sensitive to very slow or small-volume flow, because any moving blood cells contribute energy to the Doppler signal and get detected even when their velocity is low. It does not compute or display velocity or direction, so the image shows flow presence without a velocity reading. This is why it’s especially useful for picking up slow flow in tiny vessels or in areas where velocity-based methods might miss it. In contrast, grayscale imaging shows anatomy without any flow information, and velocity-based modes (pulsed or continuous wave Doppler) provide speed and direction data, not just presence of flow.

Power Doppler detects flow by measuring the strength (power) of the Doppler signal rather than its frequency shift. This makes it highly sensitive to very slow or small-volume flow, because any moving blood cells contribute energy to the Doppler signal and get detected even when their velocity is low. It does not compute or display velocity or direction, so the image shows flow presence without a velocity reading. This is why it’s especially useful for picking up slow flow in tiny vessels or in areas where velocity-based methods might miss it. In contrast, grayscale imaging shows anatomy without any flow information, and velocity-based modes (pulsed or continuous wave Doppler) provide speed and direction data, not just presence of flow.