Unit 2

Question 1

What is spectral analysis

Answer 1

The process of determining the individual doppler shifts that are present in a signal and their importance

Question 2

What does each color represent in a color doppler image

Answer 2

each color represents a velocity

Question 3

what is spectral broadening?

Answer 3

addition of many doppler signals like waveforms or color

Question 4

What is fast fourier transform? What does it allow?

Answer 4

an analysis of signals that processes pulse wave and color signals. It allows for each velocity to be written seperately.

Question 5

Why is it important that FFT allows us to write each velocity seperately?

Answer 5

This gives us the ability to show laminar flow and turbulent flow in a waveform

Question 6

What is autocorrelation used for?

Answer 6

it is used to analyze color doppler.

Question 7

Is autocorrelation more or less accurate than FFT? Why?

Answer 7

Less accurate. It does not use every scan line.

Question 8

Which is faster? FFT or Autocorrelation

Answer 8

autocorrelation is faster

Question 9

What does color encoding mean?

Answer 9

the darker the color the slower the flow

Question 10

What does color saturation mean?

Answer 10

regions with high velocity flow are displayed with increased color saturation, or lighter/whiter colors.

Question 11

What is a tissue bruit

Answer 11

In areas of high velocity stenosis, vibrations might occur in the tissue. These vibrations might make a color signal and be heard through a stethescope.

Question 12

What is color noise

Answer 12

when the doppler is set too high and very weak echoes are assigned colors insead of grey.

Question 13

What is color bleed? Why does it happen?

Answer 13

When color is extended out of the correct region because gain is too high.

Question 14

What is the difference between what we analyze using color and pulse wave doppler?

Answer 14

WIth color doppler, we analyze color but with pulse wave we analyze spectral broadening

Question 15

what is pulsatility index?

Answer 15

a ratio to show impedence or resistance to flow

Question 16

What is the Pulsatility index equation

Answer 16

PI = v(max) - v(min) / v mean

Question 17

what is the resistive index equation? What does it mean

Answer 17

RI = v(max) - v(min) / v(max)
A higher number means it is more resistant.

Question 18

What is the volume flow rate equation?

Answer 18

Q = mean velocity x area

Question 19

Are windows normal

Answer 19

Yes

Question 20

What are advantages of color doppler

Answer 20

it guides the placement of the pulse wave doppler, allows real time frame rate, and is sensitive to spatial display of blood flow

Question 21

What are disadvantages of color doppler

Answer 21

aliasing, limited frame rate, mean velocity, limited field of view

Question 22

How many crystals are in a continuous wave transducer

Answer 22

2, one sends and one receives.

Question 23

Does continuous wave have a high or low Q value?

Answer 23

A high Q value and high sensitivity

Question 24

Does CW listen to very high or very low velocities? Why?

Answer 24

Very high velocities. CW doesn’t need a break to pulse.

Question 25

What is a disadvantage of continuous wave doppler?

Answer 25

it listens to everything across the beam's axis, not just the main gate. It

Question 26

What does FFT stand for

Answer 26

fast fourier transform

Question 27

When would a velocity be hemodynamically significant

Answer 27

If it shows 51% or greater occlusion

Question 28

When would box shaped waveforms occur? What sound is associated with this

Answer 28

When there is 90% or greater occlusion. A knocking sound might be heard.

Question 29

What is an eddy? Is it normal?

Answer 29

Normal flow reversal around curves

Question 30

What is a color tag? What does it mean?

Answer 30

Green or white color Doppler flow. This means the velocity value is so high it doesn't register as a normal red or blue color

Question 31

What does pulse wave Doppler analyze?

Answer 31

Spectral broadening

Question 32

What is the ICA/CCA ratio used for? Is it quantitative or qualitative

Answer 32

It quantifies the stenosis in a vessel

Question 33

What is aliasing? Does it touch the baseline?

Answer 33

when the peak velocity is so high it can't be measured. It shouldn't touch the baseline

Question 34

What is crosstalk and why does it occur? Does it touch the baseline?

Answer 34

Crosstalk is a mirroring of the waveform below the baseline. It occurs when a vessel is scanned at 90 degrees because the transducer can't tell the direction of flow. It touches the baseline

Question 35

What is range ambiguity?

Answer 35

When there is no sample gate (cont wave) so everything in the beams axis is listened to.

Question 36

Does continuous wave have TGCs? Why or why not?

Answer 36

No. Continuous wave doesn't obey the theory that distance = velocity x time

Question 37

What happens when we assign color to continuous wave Doppler?

Answer 37

We get power Doppler

Question 38

Does power Doppler alias? Why or why not?

Answer 38

No. It cannot detect direction and is sensitive to lower flow

Question 39

What is power Doppler called in small vessels

Answer 39

Power Angio

Question 40

What is 1, 2, and 3 plex in ultrasound?

Answer 40

1 plex is grey scale, 2 plex is color Doppler, 3 plex is spectral Doppler

Question 41

Explain the nyquist limit in regards to aliasing

Answer 41

Aliasing occurs when the speed of blood exceeds the PRF, or the nyquist limit

Question 42

How does aliasing differ in color vs pulse wave Doppler

Answer 42

In color Doppler is manifests as flow reversal but in spectral Doppler it appears to wrap around the baseline.