Physics 2 quiz 5
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100 Terms
What Doppler shift does blood moving toward the transducer produce?
Positive
What Doppler shift does blood moving away from the transducer produce?
Negative
How is Doppler shift defined?
Received frequency − Transmitted frequency
What does Doppler measure?
Velocity only
What can Doppler determine except?
Tissue density
Which factor increases Doppler shift?
Higher velocity
What happens to Doppler shift as transducer frequency increases?
It increases.
At what angle is Doppler shift greatest?
0°
Which Doppler angle produces the maximum detectable Doppler shift?
0°
What happens to Doppler shift as the angle approaches 90°?
It decreases.
What is the value of cosine 0°?
1
What is the value of cosine 60°?
0.5
What is the value of cosine 90°?
0
If blood velocity doubles, what happens to Doppler shift?
It doubles.
If transmitted frequency doubles, what happens to Doppler shift?
It doubles.
Which change will decrease Doppler shift?
Larger angle
What does CW Doppler stand for?
Continuous Wave
What does PW Doppler stand for?
Pulsed Wave
Which Doppler mode has range resolution?
PW
Which Doppler mode lacks range resolution?
CW
Which Doppler mode can evaluate flow at a specific depth?
PW
Which Doppler mode measures all depths simultaneously?
CW
Which Doppler mode is limited by the Nyquist limit?
PW
Which Doppler mode is NOT limited by the Nyquist limit?
CW
Which Doppler mode can measure the highest velocities?
CW
What occurs with PW Doppler?
Aliasing.
What is the sample volume also called?
Gate
The sample volume is used with which Doppler?
PW Doppler
Increasing gate size will most likely?
Increase spectral broadening.
A small sample volume results in?
Fewer velocities sampled.
What does spectral Doppler display?
Range of blood velocities.
What does the x-axis on spectral Doppler represent?
Time.
What does the y-axis on spectral Doppler represent?
Velocity.
What does a clear spectral window indicate?
Similar blood velocities.
What does spectral broadening indicate?
Broad range of velocities.
Which flow pattern typically has a clear spectral window?
Laminar flow.
What does Color Doppler display?
Average velocity and direction.
Color Doppler is superimposed on?
2D image.
What does color hue primarily represent?
Direction.
What does red always mean in Color Doppler?
Depends on color map.
What does blue always mean in Color Doppler?
Depends on color map.
Flow toward the transducer creates?
Positive Doppler shift.
Flow away from the transducer creates?
Negative Doppler shift.
Faster blood flow produces?
Greater Doppler shifts.
What provides average velocity information in Color Doppler?
Color Doppler alone
What does PRF stand for?
Pulse Repetition Frequency
How is PRF measured?
Hz
What happens to PRF as depth decreases?
PRF increases with shallower depth.
What does increasing PRF do to the Nyquist limit?
Increases the Nyquist limit.
How is the Nyquist limit calculated?
PRF ÷ 2
What is the Nyquist limit for a PRF of 10 kHz?
5 kHz
What is the Nyquist limit for a PRF of 8 kHz?
4 kHz
When does aliasing occur?
When Doppler shift exceeds Nyquist limit.
What does aliasing represent?
Display limitation.
How does Color Doppler aliasing appear?
Abrupt color reversal.
What does color reversal caused by aliasing indicate?
Display limitation occurred.
Which Doppler modes experience aliasing?
Both PW and Color.
Which Doppler mode never aliases?
CW.
What Doppler mode is best for measuring extremely high velocities?
CW.
What Doppler mode is best for velocity information from one exact depth?
PW.
What happens to Doppler shift when blood velocity increases?
Doppler shift increases.
What happens to Doppler shift when transducer frequency increases?
Doppler shift increases.
What happens to Doppler shift when Doppler angle increases?
Doppler shift decreases.
What happens to Doppler shift when Doppler angle decreases?
Doppler shift increases.
Which Doppler angle produces the largest Doppler shift?
0°.
Which Doppler angle produces no Doppler shift?
90°.
What is the most accurate Doppler angle?
0°.
What is the clinically recommended Doppler angle?
≤ 60°.
Which Doppler mode measures velocities at a specific location?
PW.
Which Doppler mode measures very high velocities?
CW.
Which Doppler mode is affected by aliasing?
PW.
Which Doppler mode is not affected by aliasing?
CW.
What does decreasing PRF do to the Nyquist limit?
Decreases it.
What happens to PRF when imaging depth increases?
PRF decreases.
What happens to Nyquist limit when imaging depth increases?
Nyquist limit decreases.
What causes aliasing?
Doppler shift exceeds the Nyquist limit.
What does aliasing indicate?
Sampling limitation.
Does aliasing mean blood reversed direction?
False.
Does increasing PRF reduce aliasing?
Yes.
Does using a lower frequency transducer reduce aliasing?
Yes.
Does switching from PW to CW eliminate aliasing?
Yes.
Does increasing Doppler angle reduce aliasing?
Yes.
Does increasing blood velocity reduce aliasing?
No.
What does turbulent flow typically produce?
Spectral broadening.
What happens when gate size increases?
More spectral broadening.
What happens when sample volume is smaller?
Fewer velocities sampled.
What happens when sample volume is larger?
More velocities sampled.
Does Color Doppler provide exact velocity measurements?
False.
Does Spectral Doppler provide exact velocity measurements?
True.
Does red always mean artery?
False.
Does blue always mean vein?
False.
Does red always mean toward transducer?
False.
How should blood flow direction be determined?
Using color bar.
What does Color Doppler evaluate?
Direction and average velocity.
Does Doppler measure speed or velocity?
Velocity.
What does velocity include?
Speed and direction.
What does speed include?
Magnitude only.
What moving structure produces Doppler shifts in diagnostic ultrasound?
Red blood cells.
What is the Doppler effect?
Change in frequency and wavelength due to motion.
What is Doppler shift?
Difference between received and transmitted frequency.