Which method measures blood flow in vessels using sound waves?

• A. MRI
• B. X-ray Angiography
• C. Sonography
• D. Doppler Ultrasound

Answer: (D)

Measuring blood flow with sound waves relies on the Doppler effect applied to ultrasound. A transducer emits high-frequency sound into the body; moving blood cells shift the frequency of the reflected waves. By detecting this frequency change, the device determines the speed and direction of flow within vessels. This technique can be used in various modes, such as continuous or pulsed Doppler, and is often paired with color Doppler to visualize flow on the image.

MRI and X-ray angiography use magnetic fields or ionizing radiation with contrast, not sound waves, to visualize vessels. General sonography uses ultrasound to create images of anatomy and may include Doppler as a feature, but the specific method described for measuring flow with the Doppler shift is Doppler ultrasound.