Doppler

Question 1

Cosine for 0, 60, and 90 degree angles

Answer 1

1
.5
0

Question 2

If Doppler shift is positive then flow:

Answer 2

Is moving towards transducer

Question 3

If flow is away from transducer the Doppler shift is:

Answer 3

Negative

Question 4

The machine measures the _____________ but calculates the _____________.

Answer 4

Frequency shift

Velocity

Question 5

Initial f: 5 MHz
Reflected f: 4.85 MHz
What is Doppler shift?

Answer 5

-150kHz

Question 6

Advantage of CW Doppler

Answer 6

No upper limits for velocity

No aliasing

Question 7

Disadvantage of CW

Answer 7

Range ambiguity

Question 8

What is fast Fourier transform?

Answer 8

Breaks down signal to produce spectral waveform

Question 9

What is display on horizontal axis of spectral analysis?

Answer 9

Time

Question 10

What is the vertical axis present?

Answer 10

Velocity

Question 11

What does the brightness of the display represent?

Answer 11

The amplitude of the signal

Question 12

Causes of spectral broadening

Answer 12

Tortuous vessels
Turbulent flow
Sample gate too big
Sample gate too close to wall

Question 13

What is the NyQuist limit? How do we find it?

Answer 13

Level that aliasing begins

1/2PRF

Question 14

Advantages of PW

Answer 14

Range resolution

Question 15

Disadvantage of PW

Answer 15

Aliasing doesn’t allow accurate measurements of high velocities

Question 16

What is a key indicator of severity of disease within a vessel?

Answer 16

Peak velocity

Question 17

Color flow mapping is a form of pulsed Doppler.

T/F

Answer 17

True

Question 18

How is a “packet” defined?

Answer 18

of pulses sent per line of color

Question 19

How big is a packet usually?

Answer 19

Between 3-30 pulses per line

Question 20

What’s another term for packet size?

Answer 20

Ensemble length

Question 21

Hue is:

Answer 21

Perceived color

Question 22

Faster velocities are represented by:

Answer 22

Lighter hues

Question 23

More saturated means:

Answer 23

Slower flow

Question 24

Less saturation:

Answer 24

Faster flow

Question 25

How are velocity maps arranged?

Answer 25

``` White Lighter color Color Darker color Black Darker color Color Lighter color White ```

Question 26

Variance maps add color in a:

Answer 26

Side to side orientation

Question 27

What are the side colors usually and what are they used for?

Answer 27

Green or yellow | To tag turbulent flow

Question 28

Color Doppler is not angle dependent. | T/F

Answer 28

False

Question 29

Advantages of color Doppler

Answer 29

Can see vessels too small to be seen on gray scale image Helps find PSV in vessel Documentation of occlusions, severe stenosis, turbulent flow

Question 30

Disadvantage of color Doppler

Answer 30

Aliasing Can’t pick up slow/low flow areas Angle dependent

Question 31

Fast Fourier transform is faster than autocorrelation. | T/F

Answer 31

False

Question 32

Temporal resolution is decreased with autocorrelation because:

Answer 32

Large packet size | Lower frame rate

Question 33

Time domain processing/correlation determines velocity of moving reflector by:

Answer 33

Measuring change in spatial location during known time interval

Question 34

Time domain processing uses a wide bandwidth to improve:

Answer 34

Spatial info

Question 35

The Doppler angle MUST be known for time domain correlation. T/F

Answer 35

True

Question 36

Power Doppler measures _______________ of flow.

Answer 36

Concentration

Question 37

Power Doppler is able to:

Answer 37

Detect low flow in smaller vessels on venous flow

Question 38

Power Doppler is angle dependent. | T/F

Answer 38

False

Question 39

As the angle between the transducer and the flow decreases, the Doppler shift:

Answer 39

Increases

Question 40

What is clutter?

Answer 40

Noise in Doppler signal caused by high amplitude, Doppler shifted echoes

Question 41

Wall filter is a type of:

Answer 41

Reject control