Test Material Flashcards
What happens to the Doppler frequency shift when the beam angle changes relative to the vessel axis? Describe what happens when the angle:
a. increases
b. decreases
c. is perpendicular to the vessel axis
a. decrease
b. increase
c. no Doppler shift
a. What happens to the spectral waveform as the sample volume is moved from wall to wall passing through the center stream?
b. What happens to the spectral waveform as the sample volume size (axial dimension) is increased in a normal cardiac waveform.
a. When it hits the wall the window is filled in and fuzzy and the velocity is lower. Center less filled in window with nice crisp window and the peak will increase will be true peak.
b. Spectral trace more broad, less crisp window, window filled in.
With the spectrum analyzer set to a velocity scale, what will happen to the following when the angle cursor is rotated from 0 degrees and a calculation package is adjusting the velocity?
a. the spectral waveform?
b. to the velocity scale, hence the measurement of peak velocity of the waveform? Why?
a. If angle is guessed correctly the true velocity will be displayed as the calc compensates for angles not at zero. if angle is guessed wring velocity could be falsely large or small.
b.
- Scale adjusts as angle correct is changed
- Linked to calculation package to correct for angle
With the spectrum analyzer set to frequency, what will happen to the following when the angle cursor is rotated and a calculation package is adjusting the velocity?
a. to the spectral waveform
b. to the frequency scale? Why?
a. Nothing
b. Nothing
a. What happens to the spectral waveform if the PRF scale is increased? decreased?
b. At what point does aliasing occur?
c. When is it beneficial to increase PRF scale?
d. In what situation would you decrease the PRF scale?
a. Increased- decreased spectral wave form size
Decreased- increased spectral wave form size
b. Nyquist limit and 1/2 PRF
c. to eliminate aliasing and high velocity
d. 1. Low velocity
2. to increase depth of spectral trace
3. to improve measurement accuracy
a. What happens to the spectral waveform when the wall filter is increased?
b. Why is this important?
c. In what situation would you want to increase the wall filter when doing
echo scanning?
d. What is the normal wall filter setting for doing cardiac scanning?
a. low frequencies above and below baseline disappear
b. to eliminate wall motion- not to delete lwo velocity flow
c. 1. wall motion
2. valve motion
3. turbulence
d. 400 Hz
What happens as you move the focal zone to the spectral trace? To the image?
- Clears window of spectral trace
2. Improves resolution of image
How is the Doppler gain set to an optimal level? How do you know that you are not over or under gaining a signal? Why is setting the Doppler gain important?
To eliminate garbage, go to threshold and then back off. If you see mirror imaging back off. You can lose peak frequency and under calculate if under setting. You can add to peak frequency and over calculate if over setting.
List two things that can be done to alleviate aliasing of the Doppler signal using the controls for you spectral display.
a.
b.
a. Increase velocity range “scale”
b. move baseline
a. What part of the vessel is the most important to see when taking spectral waveforms?
b. What instrument controls might you change to improve the image to see plaque character better, i.e., to have a better gray scale?
a. The center so you need to see valves or two walls
b. dynamic range increase, gain, TGC, Post and Pre processing, focus zone in range
At what angle to the surface of the vessel wall are the normal double lines visualized in a vessel?
.
90 degrees, called pignoli lines
a. What do the lighter shades of color represent in the typical color map?
b. What does the black area represent?
c. What happens to the black area on the color bar if the wall filter increases?
a. high frequency, high velocity
b. color wall filter, no doppler shift
c. expands, becomes larger
If the color bar is in velocity, how are these velocities values calculated? What do they mean?
They are calculated at an angle of 0 degrees, no angle correction is assumed. They measure mean not peak velocities
a. What do the colors truly represent?
b. How does the color information differ from the spectral waveform information?
a. Mean frequency shifts, translated to velocity, direction of flow
b. color mean
spectrum peak
a. What happens to the overall PRF if the zero baseline is shifted?
b. Why would you want to shift the zero baseline?
a. same but more information on one side
b. decrease aliasing
