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What does Doppler ultrasound do?
- Detects the pressence, velocity, and properties and direction of blood flow.
- Velocity is both speed and direction.
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What is Doppler Effect?
An apparent change in frequency of sound observed if there is relative motion bwn sound source and the receiver of the sound (or listener).
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When Whistler moving toward listener:
- Shorter Wavelength
- Higher Frequency
- Positive Doppler Effect
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When Whistler moving away from listener:
- Longer Wavelength
- Low Frequency
- Negative Doppler Effect
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What is Doppler Shift?
- the difference bwn the received txd frequency and the sent txd frequency.
- Doppler Shift (Hz)= Reflected Frequency - Transmitted Frequency.
- Fd =Fr-Ft
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What is Doppler Equation?
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Range of Doppler shifted frequency
- Between 20Hz and 20000 Hz (20kHz)
- This is audible range.
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Effects of beam angle on Dopple shift:
- Doppler angle and doppler shift are inversely proportional.
- Increase Doppler angle, Decrease Dopple shift
- Increase Doppler angle, Decrease Cosine of angle
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