Doppler-shifted ultrasound is a technique used to measure the change in frequency of sound waves due to the motion of an object, such as blood flow in vessels. It utilizes the Doppler effect to provide information about the speed and direction of moving objects.
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Doppler-shifted ultrasound is based on the Doppler effect, which describes how the frequency of a wave changes relative to an observer when the source of the wave is moving.
In medical imaging, Doppler ultrasound is often used to assess blood flow and detect abnormalities in circulation.
The frequency shift observed in Doppler ultrasound can be used to calculate the velocity of blood flow using the formula $v = \frac{\Delta f \cdot c}{2f_0 \cdot \cos(\theta)}$, where $v$ is velocity, $\Delta f$ is frequency shift, $c$ is speed of sound in tissue, $f_0$ is original frequency, and $\theta$ is angle between sound beam and direction of flow.
Color Doppler imaging provides visual representation of blood flow velocities with different colors indicating different directions and speeds.
Continuous-wave (CW) Doppler and pulsed-wave (PW) Doppler are two types of Doppler ultrasound techniques; CW allows for high-velocity measurements but lacks depth resolution, while PW provides depth-specific information but has limitations on maximum detectable velocity.
Review Questions
What principle does Doppler-shifted ultrasound rely on?
How can you calculate blood flow velocity using Doppler ultrasound data?
What are the differences between continuous-wave and pulsed-wave Doppler techniques?
Related terms
Doppler Effect: The change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.
Pulsed-Wave (PW) Doppler: A type of Doppler ultrasound that uses short bursts (pulses) of sound waves to measure velocities at specific depths.
Continuous-Wave (CW) Doppler: A type of Doppler ultrasound that continuously emits sound waves and measures high velocities without depth specificity.