What technique measures changes in echo frequency to evaluate movement?

The technique that measures changes in echo frequency to evaluate movement is Doppler Ultrasonography. This method utilizes the Doppler effect, which is the change in frequency of sound waves emitted by or reflected from a moving object. In the context of vascular imaging, this effect is used to assess blood flow direction and velocity by examining the frequency shifts that occur as ultrasound waves interact with moving blood cells. As the frequency of the reflected sound waves changes in response to the movement of red blood cells, Doppler Ultrasonography provides valuable information regarding the hemodynamics within blood vessels.

Other imaging modalities, such as Magnetic Resonance Imaging, CT Scan, and Magnetic Resonance Angiography, do not employ this specific approach to detect movement. They utilize different principles and technologies. For instance, Magnetic Resonance Imaging relies on the alignment of hydrogen nuclei in a magnetic field, while CT Scan involves cross-sectional imaging using X-rays. Magnetic Resonance Angiography uses magnetic resonance techniques to visualize blood vessels, but it does not focus on the Doppler effect for measuring movement.