Topics and Color Flow Direction Flashcards
What is rouleaux flow?
RBC’s stack up in a column.
Why is rouleaux flow seen in an ultrasound image?
It forms a larger reflector so they can be seen easily in B-mode. It is sludge like in B-mode.
What is a B-flow control?
It is a control on some ultrasound machines that allow you to see flow while not using doppler.
ie. no angles.
What is a flash artifact?
If you move the probe over the skin, you get a lot of color flashing across the skin.
When does flash artifacts ocurr?
It occurs more readily with low scale and high gain.
How should you avoid flash artifact?
Best to move slowly in order to avoid it.
What control has more flash artifact than velocity color?
Power control.
What is the power doppler/color?
Display of the frequency shifted amplitudes (or power)
In power doppler, what isnt displayed?
Velocity and direction.
Power doppler is less affected by what?
angles.
Does aliasing occur with power doppler?
no, because there is no velocity display.
What is power doppler good for?
It is a good way to show course of branches.
Why is the color variance map different from a typical velocity color map?
Because it displays the amount of turbulence in the flow.
What does the color variance map do?
It basically shows laminar vs turbulent areas of slow in a vessel by a color change side to side on a velocity color bar.
What is turbulence?
A big range of velocities.
What does a regular color map show?
It shows the the mean of that range.
In a color variance map image, what does red mean?
It means velocity toward beam.
In a color variance map image, what does blue?
It means velocity is away from the beam.
In a color variance map image, what does yellow mean?
Yellow is huge range of velocities towards the beam.
In a color variance map image, what does aqua mean?
Aqua is a huge range of velocities away.
The color variance map is different from a typical velocity color map because it displays which of the following?
a. Peak frequency shifts
b. Mean velocities only
c. Range of frequency shifts.
d. Amplitude of frequency shifts.
c. Range of frequency shifts.
What kind of angle does flow toward the beam yield?
an acute angel.
What kind of angel does flow away from the beam yield?
An obtuse angel.
What two colors on the image that have black between them show?
It shows two different directions of flow relative to the beam.
what does the two colors on the image that wrap around from the highest color (aqua) to the lowest color (yellow) represent?
Aliasing.
Why does the aliasing artifact occur?
- The peak frequency shifts (peak velocities) are less than 2 times the PRF (Nyquist limit).
- basically, the f shifts are too high for the equipment settings.
What are the equipment reasons for aliasing?
- scale too low.
- baseline too high.
- probe frequency too high.
What are the physiologic reasons for high F shift?
- Stenosis
- AVF
- High flow rate
- Narrowing branch or vessel.
Curvilinear or sector probes have a doppler beam lines that _______?
Fan out.
What is a frozen color image?
It is temporal.
a snapshot in time.
Is color diagnostic?
NO
What does color document?
It documents a moment in time in one slice of a vessel.
How must you confirm a color image?
With doppler information.
What is the difference between doppler waves and a frozen color image?
Doppler waves: gives velocity and direction information over a period of time.
Frozen color image: just a moment in time.
