Chapter 20 Flashcards
What is the cosine of 90 degrees? Will there be a doppler shift at 90 degrees?
0; no
True or False;
For color to appear in the vessel, an angle other than 90 degrees must be created.
True
Will color appear in a vessel when the directions of flow and sound are perpendicular?
never
True or False;
A 90 degree angle between the directions of sound and flow can be created with a slanted vessel.
True
What are the maximum and minimum values of cosine?
max is 1 and minimum is -1
Any time a vessel is colorless what is the first thing you should do?
Check the angle between flow and sound
When color gain is set too high and color appears throughout the color box, is called?
color confetti
True or False;
If the color gain is set to low, all color can disappear from image.
true
The amount of color present on a color flow doppler image can be controlled with what setting?
the color doppler gain
_________ doppler gain settings alter the gray scale content of a spectral display
pulsed
Setting the pulsed doppler gain too ________ can cause gray scale noise to appear, while setting pulsed doppler gain too ______ can cause all gray scale to disappear.
high; low
True or False;
It is very likely to have blood flow in different directions within a single vessel.
false
________ should be considered as possible source of color variation, whenever the color changes directly from red to blue or vice versa within a vessel.
Aliasing
If aliasing occurs on a color doppler image how will it appear?
as flow in the opposite direction
How do you determine if you are looking at flow reversal or aliasing?
check the color map; whether you move through the middle of the map or move around the outside of map
If the colors that touch each other in the image go through the color maps middle, ________ is present.
flow reversal
If the colors that touch each other go around the outside of color map, __________ is present
aliasing
How is aliasing reduced or eliminated on a color doppler image?
increase the velocity scale
Does increasing the velocity scale have any other effect on a color doppler image?
Yes, increasing the scale will decrease the sensitivity to slow folws
The _____ filter selectively eliminates low frequency doppler shifts.
wall
The wall filter _______ the color from slowly moving reflectors such as blood cells and vibrating tissues.
removes
True or false
wall filters eliminate high velocity flows near the baseline of a doppler spectrum.
false
A wall filter will alter _____ velocity flows, while leaving ___ velocity flows unchanged.
low; high
If an artery is ghosting how is it fixed?
increase wall filter
