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intro > Ch. 19 Doppler > Flashcards

Ch. 19 Doppler Flashcards

1
Q

_________________________________ is the change in frequency of sound as the sound source and receiver move closer together or farther apart

A

Doppler Shift is the change in frequency of sound as the sound source and receiver move closer together or farther apart

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2
Q

Doppler Shift is also called Doppler _______________________

A

Doppler Shift is also called Doppler Frequency

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3
Q

Doppler Shift is a _____________ frequency that rides on top of the much higher transducer frequency

A

Doppler Shift is a low frequency that rides on top of the much higher transducer frequency

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4
Q

_________________________ is the process of extracting the low doppler frequency from the transducer’s carrier frequency

A

Demodulation is the process of extracting the low doppler frequency from the transducer’s carrier frequency

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5
Q

Short formula for Doppler Shift:

A

Doppler Shift (Hz) = reflected frequency - transmitted frequency

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6
Q

When the doppler shift is positive, the reflected sound has a __________________ frequency than the transmitted sound.

A

When the doppler shift is positive, the reflected sound has a higher frequency than the transmitted sound

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7
Q

When the doppler shift is negative, the reflected sound has a ____________________ frequency than the transmitted sound.

A

When the doppler shift is negative, the reflected sound has a lower frequency than the transmitted sound.

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8
Q

Doppler frequencies indicate _________________________, not speed.

A

Doppler frequencies indicate velocity, not speed

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9
Q

Speed is purely a ____________________________

A

Speed if purely a magnitude

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10
Q

Velocity is defined by a _______________ and a _________________

A

Velocity is defined by a magnitude and a direction

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11
Q

long formula for doppler shift:

A

Doppler Shift = 2 V Fo Cos / C

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12
Q

doppler shift is ____________________ related to the velocity of red blood cells

A

directly

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13
Q

The faster the velocity, the _____________________ the doppler shift

A

The faster the velocity, the greater the doppler shift

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14
Q

The x-axis of a doppler spectrum represents _______________

A

The x-axis of a doppler spectrum represents time

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15
Q

The y-axis of a doppler spectrum represents _________________________ or __________________________

A

The y-axis of a doppler spectrum represents Doppler shift or velocity

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16
Q

doppler shift is _________________ related to the frequency of the transmitted sound

A

doppler shift is directly related to the frequency of the transmitted sound

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17
Q

If the transducer frequency is doubled, the doppler shift will _______________

A

double

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18
Q

What is the range of frequencies for doppler shift?

A

20 Hertz - 20,000 Hertz (audiable range)

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19
Q

What is the relationship between the transmitted frequency and the doppler shift?

A

Directly related

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20
Q

When blood cells are moving __________ to the sound beam the entire velocity is measured

A

When blood cells are moving parallel to the sound beam the entire velocity is measured

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21
Q

The percentage of the true velocity that is measured depends on the ______________ of the angle between the sound beam and the direction of motion.

A

The percentage of the true velocity that is measured depends on the cosine of the angle between the sound beam and the direction of motion

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22
Q

What information does doppler provide (4 things)?

A
  1. presence of flow
  2. direction of flow
  3. speed of flow
  4. characteristics of flow (laminar, turbulent)
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23
Q

cosine of 90 degrees

A

0%

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24
Q

cosine of 60 degrees

A

0.5 or 50%

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25
Q

cosine of 0 degrees

A

100%

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26
Q

cosine of 180 degrees

A
  • 1.0
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27
Q

The most common clinical doppler devices are _______________________________, which distinguish the direction of flow toward or away from the transducer

A

The most common clinical doppler devices are Bidirectional, which distinguish the direction of flow toward or away from the transducer

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28
Q

Are arterial velocities higher/lower than venous velocities

A

higher

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29
Q

Continuous wave doppler requires __________ crystals within the transducer

A

Continuous wave doppler requires 2 crystals within the transducer

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30
Q

What is the greatest advantage of continuous wave doppler?

A

Accurately measure very high velocities

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31
Q

Primary disadvantage of continuous wave doppler is?

A

The exact location of the moving blood cells cannot be determined

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32
Q

The limitation of continuous wave doppler is that the exact location of moving blood cells cannot be determined and this is called:

A

range ambiguity

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33
Q

Another disadvantage of continuous wave doppler is its lack of:

A

TGC’s time gain compensation

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34
Q

A dedicated continuous wave transducer is simple because it does not create __________________________________

A

A dedicated continuous wave transducer is simple because it does not create anatomic images

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35
Q

Dedicated continuous wave transducers contain _____ elements, each shaped like a ___________________

A

Dedicated continuous wave transducers contain 2 elements, and each shaped like a semicircle

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36
Q

Simultaneous imaging and doppler imaging is called:

A

Duplex imaging

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37
Q

Dedicated continuous wave transducers do not use ______________________ which results in:
- undampened transmitted signal
- narrow bandwidth
- high quality factor
- higher sensitivity

A

Dedicated continuous wave transducers do not use backing which results in:

  • undampened transmitted signal
  • narrow bandwidth
  • high quality factor
  • higher sensitivity
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38
Q

In Pulsed wave doppler how many PZT crystals are necessary?

A

1

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39
Q

What is the greatest advantage of pulsed wave doppler?

A

the greatest advantage of pulsed wave doppler is being able to select the exact location where velocities are measured, called range resolution

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40
Q

The greatest advantage of pulsed wave doppler is called:

A

Range Resolution, Range Specificity, or freedom from range ambiguity artifact

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41
Q

With pulsed wave doppler the sonographer positions a small marker called the _______________________________________ on a 2D image

A

With pulsed wave doppler the sonographer positions a small marker called the sample volume or sample gate on a 2D image

42
Q

What is the primary disadvantage of pulsed wave doppler?

A

Inaccurate measurement of high velocity signals

43
Q

When high velocity flow is incorrectly displayed as traveling in the opposite direction the inaccuracy is called _______________________

A

When high velocity is incorrectly displayed as traveling in the opposite direction the inaccuracy is called Aliasing

44
Q

Pulse wave doppler transducers are imaging transducers and contain _________________________________, which provide low Q-factor, lower sensitivity, and wide bandwidth pulses.

A

Pulse wave doppler transducers are imaging transducers and contain backing material, which provide low Q-factor, lower sensitivity, and wide bandwidth pulses.

45
Q

_______________________ is the most common error associated with doppler ultrasound.

A

Aliasing is the most common error associated with doppler ultrasound

46
Q

An alias is a:

A

false identity

47
Q

Aliasing occurs only with __________________ doppler

A

Aliasing occurs only with pulsed doppler

48
Q

Nyquist limit equation

A

Nyquist limit = PRF/2

49
Q

______________________________ is the highest doppler frequency that can be measured without appearance of aliasing

A

Nyquist limit is the highest doppler frequency that can be measured without appearance of aliasing

50
Q

2 ways to avoid aliasing are:

A
  1. raise the nyquist limit
  2. reduce the doppler shift
51
Q

The sampling rate of pulsed doppler is the systems _____________

A

The sampling rate of pulsed doppler is the systems PRF

52
Q

When sample volume is deep the PRF Is ___ and the nyquist limit is ___

A

low, low

53
Q

Since deeper sample volumes have a lower PRF, __________ happens

A

Aliasing

54
Q

Higher or Lower frequency transducers create more aliasing

A

Higher

55
Q

5 techniques used to avoid aliasing artifact

A
  1. adjust scale to max
  2. select new ultrasonic view with shallower sample volume
  3. select lower frequency transducers
  4. use baseline shift
  5. use continuous wave doppler
56
Q

When the sonographer adjusts the scale to its max the ________________ is also increased to its max

A

When the sonographer adjusts the scale to its max the PRF is also increased to its max

57
Q

What is the advantage of maximizing the PRF?

A

Maximizing the PRF, raises the nyquist limit and aliasing is less likely to occur

58
Q

What is the disadvantage of raising the PRF to its max?

A

reduces sensitivity to low velocities

59
Q

What is the advantage of selecting a lower frequency transducer?

A

lower shifts occur with lower frequency transducers

60
Q

Advantage of zero baseline shift

A

High velocity flows are displayed in proper direction

61
Q

Advantage of using continuous wave doppler

A

Aliasing never appears with continuous wave doppler

62
Q

Eliminating aliasing improves the ability to measure the ____________________________ with doppler

A

Eliminating aliasing improves the ability to measure the maximum velocity with doppler

63
Q

Gray shades on a Doppler spectrum are related to the ______________________ of reflected signal, or the number of ____________________________ creating the reflection.

A

Gray shades on a Doppler spectrum are related to the amplitude of reflected signal, or the number of blood cells creating the reflection.

64
Q

_______________________________ is a form of 2D doppler where velocity information is coded into colors and superimposed on a 2 dimensional gray scale anatomic image

A

Color Flow Doppler is a form of 2D doppler where velocity information is coded into colors and superimposed on a 2 dimensional gray scale anatomic image

65
Q

Color doppler provides information on the location of flow and therefore:

A
  • is a pulsed ultrasound technique
  • has range resolution
  • is subject to aliasing
66
Q

Color Doppler measures the ____ velocity.

A

Color Doppler measures the mean velocity

67
Q

Spectral Doppler measures the _______________ velocity

A

Spectral Doppler measures the peak velocity

68
Q

Color doppler uses a “dictionary” or a ___________________________ to concert measured velocities into colors that appear on the image

A

Color doppler uses a “dictionary” or a lookup table to concert measured velocities into colors that appear on the image

69
Q

The two most commonly used dictionaries for color doppler are called:

A

Velocity mode and Variance mode

70
Q

What do the colors mean in a velocity mode map mean?

A

Flow direction and velocity

71
Q

What do the colors mean on a variance mode map?

A

In addition to direction and velocity, variance mode distinguishes laminar flow from turbulent flow

72
Q

with the variance map, remember that the left side is always the __________________ side

A

with the variance map, remember that the left side is always the laminar side

73
Q

The black region in the middle of the color map means?

A

No doppler shift

74
Q

With color doppler multiple ultrasound pulses are used to accurately determine blood velocities, these multiple pulses are called a

A

packet or ensemble

75
Q

Power mode only identifies the presence of a

A

Doppler shift

76
Q

Power mode is _____________________ color doppler

A

Power mode is non-directional color doppler

77
Q

Power Doppler is also known as:

A

~ energy mode
~ color angio

78
Q

In power mode the ____________ of the reflected signal is processed without regard to the bloods direction or speed

A

In power mode the strength of the reflected signal is processed without regard to the bloods direction or speed

79
Q

The amplitude of the reflection is _____________________ related to the number of moving blood cells

A

The amplitude of the reflection is directly related to the number of moving blood cells

80
Q

3 advantages of power mode are:

A
  1. Increased sensitivity
  2. unaffected by doppler angles
  3. no aliasing
81
Q

3 disadvantages of power mode are:

A
  1. no measurement of velocity or direction
  2. lower frame rates
  3. susceptible to motion of the transducer, patient, or soft tissues, which may result in a burst of color, or flash artifact
82
Q

On spectral displays, the low frequency doppler shift artifacts are called _________________________

A

On spectral displays, the low frequency doppler shift artfiacts are called clutter

83
Q

With color doppler, the low frequency doppler shifts are called ______________________________________

A

with color doppler, the low frequency doppler shifts are called Ghosting Artifact

84
Q

What is used to eliminate low frequency doppler shifts from moving anatomy rather than from moving blood cells?

A

Wall filter

85
Q

Wall Filters serve as a _____________________ for doppler

A

Wall Filters serve as a Reject for doppler

86
Q

With color Doppler, _____________________ eliminate color arising from slow velocity reflectors

A

With color doppler, wall filters eliminate color arising from slow velocity reflectors

87
Q

___________________________ is a special form of “mirror image” artifact that arises only with spectral doppler

A

Crosstalk is a special form of “mirror image” artfiact that arises only with spectral doppler

88
Q

Crosstalk results from either:

A
  1. Doppler gain is too high
  2. incident angle is near 90°
89
Q

_______________________________________ 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.

A

Spectral analysis 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

90
Q

2 methods of spectral analysis are:

A
  1. Fast Fourier Transform (FFT)
  2. Autocorrelation
91
Q

_____________________________________ is a digital (computer-based) technique that is used to process both pulsed and continuous wave doppler signals

A

Fast Fourier Transformation is a digital (computer-based) technique that is used to process both pulsed and continuous wave doppler signals

92
Q

Fast Fourier Transformation has what 2 advantages?

A
  1. exceedingly accurate
  2. displays all individual velocities
93
Q

The spectral display of an FFT distinguishes _______________________ flow from __________________________ flow

A

The spectral display of an FFT distinguishes laminar flow from turbulent flow

94
Q

With laminar flow the region between the baseline and the spectrum that is “clear” and is called the

A

spectral window

95
Q

With turbulence flow the spectral window is filled in and is known as

A

spectral broadening

96
Q

The digital technique used to analyze color flow doppler is called ________________________________

A

The digital technique used to analyze color flow doppler is called Autocorrelation

97
Q

Autocorrelation is somewhat less accurate but substantially faster to perform than ________________________________

A

Autocorrelation is somewhat less accurate but substantially faster to perform than Fast Fourier Transformation

98
Q

The Doppler effect is presented as a ___________________ when the source and receiver are ________________

A

The Doppler effect is presented as a frequency shift when the source and receiver are in motion relative to each other

99
Q

Starting from the same point, the sound source is moving toward the east at 12 miles/hour and the receiver is moving toward the west 10 miles/hour. The Doppler shift is ____________________ (positive or negative)

A

The Doppler shift is negative because the source and receiver are moving farther apart

100
Q

Starting from the same point, the receiver is moving toward the west at 12 miles/hour and the source is moving toward the west at 10 miles/hour. The Doppler shift is _______________________ (positive or negative)

A

The Doppler shift is negative because the source and receiver are moving farther apart

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