POCUS - Doppler Flashcards
What is the formula for doppler frequency?
F(d) = (2(F(o)v(cos(theta))) / c
Doppler frequency equals two times the transmitted frequency times the velocity of the fluid in transmit multiplied by cosine of the angle of the flow to the transducer divided by the speed of sound.
Note, the cosine of 90 is zero which is why there will be no Doppler perpendicular to flow.
When obtaining Doppler, you will get the best measurements between what angle parameters?
0 - 60 (zero being directly in plane with the flow)
Review Robert Jones’s strobe light analogy for aliasing.
Imagine a person dancing in a strobe light. If the strobe light is slower than their dance moves then they appear to move chaotically. If the strobe light frequency increases then the flow of their movements become apparent.
What are the advantages and disadvantages of power Doppler?
Advantages:
- Very sensitive for flow of any kind
Disadvantages:
- Lots of artifact from increased sensitivity (flash artifact)
True or false: in most power Doppler modes the higher amplitude flow is dark orange.
False
It is light orange. Dark orange is lower amplitude flow.
The color box allows what degree of angle manipulation?
positive to negative 15 degrees
Why should you narrow the color box to the smallest size needed?
The larger the box means slower Doppler sampling rate, and thus poorer Doppler calculations.
What is PRF?
Pulse repetition frequency – the amount of Doppler sampling per second. You can set this higher if you begin to get aliasing
What should you try if you think you should be seeing color flow but you’re not?
Increase the Doppler gain
What does wall filter do?
Increasing the wall filter removes lower velocity flow, so it’s useful if you are scanning something that is low flow, you have Doppler gain turned up, and you are getting artifact.
Pulse-wave Doppler is also called what?
Spectral (think of the waveform)
When using spectral Doppler, make sure you have the gates _____________.
in the center of the vessel (and as narrow as possible)
What does “duplex” mean?
Duplex means using both color Doppler and spectral Doppler
