Chapter 19

Question 1

Doppler shift is the apparent change in the ____ of a wave as a result of relative motion between the sound source and the observer.

Answer 1

Frequency

Question 2

____ ____ is the principle used to measure the velocity of blood moving in the body.

Answer 2

Doppler shift

Question 3

Doppler Shifts are created when transmitted sound waves strike moving ____ ____ ____.

Answer 3

Red blood cells

Question 4

What is the equation for doppler shift?

Answer 4

Doppler shift (Hz) = reflected freq. – transmitted freq.

Question 5

With a positive doppler shift, the red blood cells are moving ____ the transducer.

Answer 5

Towards

Question 6

With a negative doppler shift, the red blood cells are moving ____ the transducer.

Answer 6

Away from

Question 7

Doppler frequencies indicate ____ NOT speed.

Answer 7

Velocity

Question 8

____ is a magnitude, indicates distance but not direction. Units are cm/sec.

Answer 8

Speed

Question 9

____ is a magnitude and a direction (north, south, towards, away).

Answer 9

Velocity

Question 10

The equation for velocity is:

Answer 10

Doppler shift x (1540 m/s) / 2 x transducer frequency x cosine angle

Question 11

Doppler shift is ____ related to the velocity of the blood cells.

Answer 11

Directly

Question 12

Doppler shift is ____ related to the transmitted frequency.

Answer 12

Directly

Question 13

Doppler shift is ____ related to the Doppler angle.

Answer 13

Inversely

Question 14

If the sound beam and flow direction are not parallel, the percentage of the true velocity that is measured depends on the ____ between the sound beam and the direction of motion.

Answer 14

Cosine of the angle

Question 15

Doppler shift is ____ related to the cosine of the angle between flow direction and direction of sound.

Answer 15

Directly

Question 16

If flow is perpendicular (90˚), then the cosine = ____.

Answer 16

0

Question 17

With flow parallel to the sound beam, the angle would be ____ or ____.

Answer 17

0° or 180°

Question 18

With flow perpendicular to the sound beam, the angle would be ____.

Answer 18

90°

Question 19

____ doppler distinguishes the presence and direction of flow.

Answer 19

Bidirectional

Question 20

Most common clinical Doppler devices are ____.

Answer 20

Bidirectional

Question 21

____ ____ is a commonly used signal processing technique for bidirectional Doppler.

Answer 21

Phase quadrature

Question 22

Continuous wave doppler requires how many crystals in the transducer?

Answer 22

Two

Question 23

Main advantage of ____ doppler is its ability to accurately measure very high velocities.

Answer 23

CW

Question 24

The main disadvantage of CW is ____ ____, which is the inability to determine the exact location of the moving red blood cells that are creating the waveform.

Answer 24

Range ambiguity

Question 25

Pulsed wave doppler requires how many crystals in the transducer?

Answer 25

One

Question 26

A major advantage for ____ doppler is range resolution.

Answer 26

PW

Question 27

____ ____ is the ability to determine the exact location of the moving red blood cells that are creating the waveform.

Answer 27

Range resolution

Question 28

Aliasing exists only with ____ Doppler.

Answer 28

PW

Question 29

____ is when the PW Doppler sampling rate is too low in comparison to measured blood velocity, therefore cells moving at high velocities are displayed as moving in the wrong direction.

Answer 29

Aliasing

Question 30

____ ____ is the highest Doppler velocity that can be measured without the appearance of aliasing.

Answer 30

Nyquist limit

Question 31

How to you calculate the nyquist limit?

Answer 31

PRF/2

Question 32

Higher frequency transducers create ____ aliasing because they create higher Doppler shifts

Answer 32

More

Question 33

Lower frequency transducers create ____ aliasing because they create lower Doppler shifts.

Answer 33

Less

Question 34

What are the five techniques that may be used to avoid aliasing?

Answer 34

1. Adjust the waveform scale to its maximum 2. Move the baseline shift up or down so that the entire waveform fits in the appropriate area 3. Select a new ultrasound view with a shallower sample 4. Select a lower frequency transducer 5. Use continuous wave Doppler

Question 35

The grey shades on a Doppler spectrum are related to the ____ of the reflected signal, or number of ____ creating the reflection.

Answer 35

Amplitude; redblood cells

Question 36

____ imaging is simultaneous anatomic imaging (2D greyscale image) and Doppler.

Answer 36

Duplex

Question 37

Best type of transducers for duplex imaging are ____.

Answer 37

Arrays

Question 38

____ doppler simply measures the presence of moving blood cells by detecting a Doppler shift. Does not distinguish direction of flow.

Answer 38

Power

Question 39

____ dopper is a form of two-dimensional Doppler. The velocity of blood flow is coded into colors and superimposed on a 2D greyscale, anatomic image.

Answer 39

Color flow doppler

Question 40

Color Doppler reports ____ velocities.

Answer 40

Average

Question 41

Pulsed and continuous wave doppler report ____ velocities.

Answer 41

Peak

Question 42

The colors in a velocity mode map present information on flow ____.

Answer 42

Direction

Question 43

The black region in the middle indicates ____ Doppler shift.

Answer 43

No

Question 44

The colors above the black region indicate blood cells moving ____ the transducer (positive Doppler shifts).

Answer 44

Toward

Question 45

The colors below the black region indicate blood cells moving ____ the transducer (negative Doppler shifts).

Answer 45

Away from

Question 46

Colors closer to the black region indicate ____ velocities, while colors further from the black region indicate ____ velocities.

Answer 46

Lower; higher

Question 47

Top and bottom (yellow and green on bar to left) represent the ____ ____.

Answer 47

Nyquist limit

Question 48

The ____ maps display different colors side to side.

Answer 48

Variance

Question 49

With variance maps, colors from the left side of the map indicate ____ flow.

Answer 49

Laminar

Question 50

With variance maps, colors from the right side of the map indicate ____ flow.

Answer 50

Turbulent

Question 51

With color Doppler, multiple ultrasound pulses are used to accurately determine blood cell velocities. These multiple pulses are called a ____ or ____.

Answer 51

Packet or ensemble

Question 52

On spectral displays (doppler graph), the low frequency doppler shift artifacts are called ____.

Answer 52

Clutter

Question 53

On color doppler, the low frequency doppler shift artifacts are called ____.

Answer 53

Ghosting

Question 54

____ ____ (aka high pass filters) eliminate low frequency Doppler shifts from moving anatomy rather than blood flow.

Answer 54

Wall filters

Question 55

Crosstalk is a special form of mirror image artifact that arises only with ____ doppler.

Answer 55

Spectral

Question 56

____ appears as an identical Doppler spectrum both above and below the baseline.

Answer 56

Crosstalk

Question 57

____ ____ is 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 57

Spectral analysis

Question 58

Two methods of spectral analysis are:

Answer 58

- Fast Fourier Transform (FFT) - Autocorrelation

Question 59

Fast Fourier Transform (FFT) is a digital (computer-based) technique used to process both ____ and ____ wave doppler signals.

Answer 59

Pulsed and continuous

Question 60

Because ____ displays all the individual frequencies, the spectral display can distinguish laminar flow from turbulent flow.

Answer 60

FFT

Question 61

Autocorrelation is the digital technique used to analyze ____ doppler. It determines the mean velocity.

Answer 61

Color flow

Question 62

____ is used to analyze color Doppler because of the huge amounts of data that is processed.

Answer 62

Autocorrelation

Question 63

Autocorrelation is ____ accurate than FFT but ____ at processing large amounts of data.

Answer 63

Less; faster