Chapter 19 Pt. 2

Question 1

The most common error associated with Doppler Ultrasound

Answer 1

Aliasing

Question 2

High velocity flow in one direction that is incorrectly displayed as traveling in the opposite direction is?

Answer 2

Aliasing

Question 3

The very top of the display is called?

Answer 3

Nyquist limit

Question 4

Part of the spectrum appearing at the bottom

Answer 4

Aliasing

Question 5

The highest Doppler frequency or velocity that can be measured without the appearance of aliasing

Answer 5

Nyquist frequency (limit)

Question 6

Nyquist limit is ___________ of the pulse repetition frequency (PRF)?

Answer 6

half

Question 7

Two ways to avoid aliasing are:

Answer 7

1. raise the nyquist limit

2. reduce the Doppler shift

Question 8

Higher frequency transducers create________ aliasing,

Answer 8

more

Question 9

Higher frequency transducers create _________Doppler shifts and lower frequency transducers create ____ Doppler shifts

Answer 9

Higher, lower

Question 10

5 techniques used to avoid aliasing

Answer 10

1. Adjust the scale to its max
2. Select a new ultrasonic view with a shallower sample volume
3. Select a lower frequency transducer
4. Use baseline shift
5. Use continuous wave doppler

Question 11

Color Doppler measures. . .

Answer 11

average or mean velocity

Question 12

Spectral Doppler (continuous and pulsed) measures

Answer 12

peak velocity

Question 13

In Velocity mode the colors above the black stripe indicate?

Answer 13

Blood cells moving towards the transducer, Positive Doppler shift

Question 14

Colors below the black stripe indicate?

Answer 14

Blood cells moving away from the transducer, Negative Doppler shift

Question 15

The black region in the middle of the color map indicates:

Answer 15

No Doppler shift

Question 16

Variance mode distinguishes

Answer 16

laminar and turbulent flow

Question 17

In variance mode, colors of the left side of the map indicate?

Answer 17

Laminar flow

Question 18

In Variance mode, colors on the right side of the map indicate?

Answer 18

Turbulent flow

Question 19

Multiple pulses used in color Doppler to accurately determine blood velocity

Answer 19

Packet or ensemble

Question 20

Power mode is

Answer 20

Nondirectional Doppler

Question 21

Power Doppler is also called

Answer 21

energy mode or color angio

Question 22

On Spectral displays, low frequency Doppler shift artifacts are called

Answer 22

Clutter

Question 23

With color Doppler low frequency Doppler shift artifacts are called?

Answer 23

Ghosting

Question 24

Wall filters are used to eliminate what?

Answer 24

Clutter

Question 25

a special form of "mirror" image artifact, that arises only with spectral Doppler

Answer 25

Crosstalk

Question 26

a tool that breaks the complex signal into its basic "building blocks" and identifies the individual velocities that make up the reflected Doppler signal

Answer 26

Spectral analysis

Question 27

Two methods that spectral analysis is currently used for?

Answer 27

1. Fast Fourier Transform (FFT) | 2. Autocorrelation

Question 28

A digital technique, used to process both pulsed and continuous wave Doppler signals

Answer 28

Fast Fourier Transform (FFT)

Question 29

Two advantages of FFT

Answer 29

- exceedingly accurate | - displays all individual velocity components that make up the complex reflected signal

Question 30

Spectral display of an FFT distiguishes

Answer 30

laminar from turbulent flow

Question 31

a wider range of velocities and Doppler shift within the sample volume

Answer 31

Spectral broadening

Question 32

a digital technique used to analyze color flow Doppler

Answer 32

Autocorrelation

Question 33

Identifies the highest velocity jets anywhere along the length of the ultrasound beam

Answer 33

Continuous wave Doppler

Question 34

Accurately identifies the location of flow

Answer 34

Pulsed wave

Question 35

Provides two dimensional flow information directly on anatomic image

Answer 35

Color flow

Question 36

Used with low velocity or small volume blood flow

Answer 36

Power mode

Question 37

With what Doppler modality does Range ambiguity occur?

Answer 37

Continuous wave Doppler

Question 38

With what Doppler modality does Range resolution occur?

Answer 38

Pulsed wave Doppler, Color Flow, and power mode

Question 39

Doppler modality that is most sensitive?

Answer 39

Continuous wave

Question 40

Pulsed wave Doppler is ____________ sensitive?

Answer 40

Moderately

Question 41

Moderately sensitive and the size of the color jet is most affected by color Doppler gain settings

Answer 41

Color flow

Question 42

What Doppler modality has greater sensitivity than color flow?

Answer 42

Power mode

Question 43

What Doppler modalities have Very good temporal resolution?

Answer 43

Continuous wave and pulsed wave

Question 44

Color flow has reduced temporal resolution due to ___________?

Answer 44

multilple packets

Question 45

What Doppler mode has the lowest temporal resolution?

Answer 45

Power mode

Question 46

__________has no aliasing

Answer 46

Continuous wave

Question 47

This modality is subject to aliasing

Answer 47

Pulsed wave

Question 48

Power mode is subject to __________ artifact, not to aliasing

Answer 48

flash

Question 49

Based on pulsed ultrasound, color flow is subject to

Answer 49

aliasing

Question 50

Which Doppler measures mean velocities

Answer 50

Color flow

Question 51

Which Doppler measures Peak velocities

Answer 51

Continuous wave and pulsed wave

Question 52

Which Doppler measures no velocities

Answer 52

Power mode

Question 53

Doppler shift is directly related to

Answer 53

velocity & transducer frequency

Question 54

Doppler shift is _______________ related to the cosine of the angle between the directions of flow and the direction of sound

Answer 54

directly

Question 55

CW transducer do not use __________

Answer 55

Backing material

Question 56

No use of backing material results in

Answer 56

- undampened transmitted signal - narrow bandwidth - high quality factor - higher sensitivity

Question 57

CW transducers have ___________and they detect ___________ amplitude reflections and small Doppler shifts

Answer 57

increased sensitivity , low

Question 58

Pulsed Doppler Transducers are ________ transducers and contain__________

Answer 58

imaging, backing material

Question 59

Since PW transducers have backing material they have

Answer 59

- low quality factor - lower sensitivity - wide bandwidth pulses

Question 60

Nyquist limit formula

Answer 60

nyquist limit(Hz) = PRF (Hz)/2

Question 61

- slower blood velocity - lower frequency - shallow gate (high PRF)

Answer 61

Less aliasing

Question 62

- Faster blood velocity - Higher frequency - deep gate (low PRF)

Answer 62

More aliasing

Question 63

Doppler shift formula

Answer 63

Doppler shift (Hz)= reflected frequency- transmitted frequency

Question 64

What two techniques to avoid aliasing have no disadvantages?

Answer 64

Selecting a new ultrasonic view, and lower frequency tranducer