Doppler
Why does aliasing occur
High velocities exceed the nyquist limit
Laminar flow has layers that travel ..
Parallel to eachother in layers
Variance mode adds information about
Turbulence
A Doppler angle approaches 90°, and the color signal fades despite adequate settings; this is because:
cosine is becoming 0
A vessel has very slow flow but shows no color.
👉 What is the FIRST setting you should decrease
PRF
deeper imaging depth causes
Lower PRF
is velocity increases what happens to Reynold number
It increases
Increasing ensemble length effects PRF in what way
Decreases PRF
Increasing propagation speed will have what effect on Doppler frequency
Decreases Doppler frequency
What may happen is the wall filter is set too high
It may lose low velocities
What Doppler type never exhibits aliasing
Continuous wave
what 3 situations can result in inertial energy loss
1. Stenosis 2. Phasic flow 3. Pulsatile flow
A vessel appears close to the baseline with highly saturated color, indicating what type of velocity
Low velocity
Velocity shown as washed out and pale indicates what about saturation
Low saturation
If angle increases what happens to Doppler shift
Decreases
Vessel demonstrates green and yellow colors. Which mode is being used and which flow is being demonstrated
Variance mode on color doppler
Turbulent flow
When can steady flow occur
when pt holds breath, phasic flow stops temporarily
Decreased PRF increases the risk of
Aliasing
A color map shows black in the center and colors above and below; the black region represents:
No Doppler shift
At stenosis what happens to velocity and pressure
High velocity low pressure
color Doppler measures
Mean velocity
Average velocity in parabolic flow equation
1/2 of maximum velocity
In a rectangular color Doppler image, determining flow direction requires use of the:
Home line
A vessel appears pale in color but is far from the baseline; this indicates that the flow has:
High velocity and low saturation
In variance mode turbulent flow appears on R side or L side
Right side