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Ambers Physics 1 > Doppler Principles > Flashcards

Doppler Principles Flashcards

1
Q

The doppler effect was first described by who, when

A

Christian Andreas Doppler

1803-1853

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2
Q

Doppler proposed a theory in what year to explain the observed differences of the colour of some stars

A

1842

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3
Q

What are some examples of how doppler is used

A

Radar
Sonar
Ultrasound

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4
Q

A change in —— results from relative motion of the source of the sound or the receiver

A

Pitch

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5
Q

When a sound source is moving towards you the wave crests are closer or farther apart and the pitch is higher or lower

A

Wave crests closer

Pitch is higher

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6
Q

When a sound source is moving away from you the wave crests are closer or farther apart and the pitch is higher or lower

A

Wave crests are further apart

Pitch is lower

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7
Q

Doppler info is primarily used to assess blood flow what two ways

A

Qualitatively

Quantitatively

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8
Q

Doppler can give you what three pieces of information

A

Presence of flow
Direction of flow
Quality of flow

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9
Q

Presence, direction and quality of flow through doppler is provided in what three ways

A

Spectral tracing
Color imaging
Audible sound

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10
Q

Direction of flow moving away is represented as a positive or negative shift in frequency

A

Negative

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11
Q

Direction of flow moving towards is represented as a positive or negative shift in frequency

A

Positive

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12
Q

Conventially on the machines what acronym is commonly used to show blood flow and what does it mean

A

BART
BA. Blue away
RT. Red towards

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13
Q

When scanning both 2D image and doppler simultaneously it is called what

A

Duplex scanning

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14
Q

When the display shows the image and a spectral tracing at the same time this is called

A

Duplex scanning

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15
Q

When scanning both the 2D image and colour doppler is on simultaneously this is referred to as

A

Triplex scanning

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16
Q

Sound reflecting off of moving blood cells does what to returning frequency

A

It alters the returning frequency

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17
Q

The amount of change to the frequency returning from reflecting off of blood cells depends on what two things

A

Direction
Speed
Of red blood cells

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18
Q

Is this change in frequency within our hearing range

A

Yes

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19
Q

What is the typical diameter of a red blood cell

A

7 um

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20
Q

Since blood cells diameter is smaller then a typical wavelength what type of scatter occurs

A

Rayleigh scatter

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21
Q

The intensity of scattered sound is directly proportional to —— and therefore indicates the quantity of blood in the sample

A

To the number of red blood cells

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22
Q

The doppler shift is based on what principle

A

The principle of wave interference

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23
Q

A reflected wave varies slightly in frequency from the transmitted wave what results

A

A beat frequency is the result

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24
Q

What is the most basic level formula used to calculate the doppler shift

A

Doppler shift = received f - transmitted f

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25
Q

What is the more detailed formula for doppler shift and what does it show the relationship between

A

(2*operating frequency)(velocity)(cos feta)
Doppler shift = ———————————————————
Speed of sound

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26
Q

In the doppler shift equation what is the most meaningful component to sonographers

A

V (velocity of RBC)

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27
Q

The operating frequency has a —— relationship with the doppler effect

A

Linear

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28
Q

If the operating frequency increases what happens to the doppler
Shift

A

Doppler shift increases as well

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29
Q

If frequency is higher/increases what happens to resolution and penetration

A 
Increase resolution 
Decrease penetration (due to attenuation)
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30
Q

Since RBC return very little intensity a lower or higher frequency probe is needed for doppler

A

Lower frequency

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31
Q

In duplex scanning does the image or doppler use higher or lower frequencies

A

Image - higher

Doppler - lower

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32
Q

RBC has what kind of relationship with the doppler shift

A

Linear relationship

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33
Q

As RBC move faster the difference in the returning frequency increases therefore the doppler shift ——

A

Increases as well

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34
Q

What is extremely important in doppler

A

Angle

35
Q

The cosine of 90 degrees is zero. Therefore when the beam is perpendicular to the vessel what happens to doppler shift

A

Doppler shift cannot be calculated

36
Q

What impacts the velocity calculated in the equation? Because it must be consistent for proper patient care

A

Angle of insonation

37
Q

What is the most accurate angle for the correct calculation of velocity

A

Zero degrees (cosine 1)

38
Q

As —— increases so does the percent error for velocity

A

Angle of insonation

39
Q

The calculation of RBC velocity is only as good as the accuracy of the

A

Angle

40
Q

How does a sonographer ensure the angle is accurate

A

Setting the angle to 60 degrees and heel toe probe until the angle indicator line is parallel to flow

41
Q

What is the limit reached when the RBC velocities are faster then the machines ability to sample called

A

Nyquist limitation

42
Q

The rate at which pulses are sent out are limited by

A

The speed of sound in tissue

43
Q

The nyquist limit is equal to

A

1/2 the PRF

44
Q

1/2 PRF usually falls in which range

A

5-30 kHz

45
Q

An artifact that occurs when the Nyquist limit is exceeded is known as

A

Aliasing

46
Q

Aliasing is shown like what on a graph

A

Parts of the signal are wrapped around the baseline

Blood cells are not being sampled fast enough so false readings occur

47
Q

Correcting aliasing can be done in which 5 ways

A 
Move baseline (real life)
Increase PRF (real life) 
Increase doppler angle - heel toe probe 
Lower the operating frequency
Change to continuous wave
48
Q

It is possible to send out the second wave before the first comes back but by doing so we are at risk of what occurring

A

Range ambiguity

49
Q

What should be positioned in the middle of the vessel, or where the fastest velocity flow occurs

A

The gate

50
Q

—— allows several depths to be sampled simultaneously

A

Multi-gating

51
Q

The sample volume is created because of the

A

Range equation

52
Q

The sample volume is determined by what 3 factors

A

The beam width
The receiver gate length
The length of the emitted pulse (number of cycles in pulse)

53
Q

The overall sample volume is equal to what

A

1/2 pulse length. Plus. Gate length

54
Q

If the gate length is reduced what must happen to the pulse length

A

Pulse length must also be reduced

55
Q

A bigger/smaller gate length will improve spectral display

A

Smaller

56
Q

Longer/shorter pulses are required to improve the accuracy of the doppler shift

A

Longer

57
Q

To achieve a more accurate beat frequency the pulse duration must be

A

Longer

58
Q

A minimum of —— cycles/pulse are required for color and spectral

A

4 (typically at 30)

59
Q

In 2D scanning a short or long pulse duration is best

A

Short

60
Q

Range gating is not possible with what kind of doppler

A

Continous wave

61
Q

CW doppler sample is found at the intersection of the transmitted and received beam and tends to be about how big

A

5-6 cm

62
Q

The zone where the transmitted and received beams intersect is known as the

A

Zone of sensitivity

63
Q

With a large sample volume it is possible to do what and it would result in a very complex spectral tracing

A

Possible to pick up more then one vessel

64
Q

When the beam intersects flow, echos are produced and many different ——— are returned to the vessel

A

Doppler shifts

65
Q

The spectrum created is a range of generated doppler shift frequencies from —— that pass through the sample volume

A

From each RBC

66
Q

What term means “to take part”

A

Analysis

67
Q

The spectrum is an array of the components of a wave arranged in order of ———— over ——

A

Increasing frequency over time

68
Q

The spectral tracing of doppler frequencies generated by moving blood that we see are plotted along the following 3 axes

A

Time (x)
Frequency or velocity (y)
Power (z)

69
Q

The power (Z-axis) is represented by what

A

Brightness of pixels

70
Q

The brightness of pixels (power)(z-axis) is proportional to

A

The number of cells moving at one velocity at a given time

71
Q

The greater the number of RBC contained in a sample the —— the waveform

A

Brighter

72
Q

The way in which the system creates the spectral trace is through a process of

A

Fast Fourier Transform (FFT)

73
Q

What is FFT

A

A mathematical technique that separates the individual doppler shifts from the complex beat frequency

74
Q

The Y-axis can represent what two things

A

Frequency of doppler shift

Velocity of RBC

75
Q

Frequency is expressed in what units

Velocity is expressed in what units

A

Frequency kHz

Velocity cm/s m/s

76
Q

Is frequency or velocity preferred for on the y-axis and why

A

Velocity. Because it compensates for variations in vessel alignment relative to surface and more meaningful to technologist

77
Q

When assessing flow direction on a spectral trace it is relative to

A

The transducer

78
Q

What word means, flow towards the probe and is expressed as positive number on Y-axis

A

Antegrade

79
Q

Which word means flow away from probe and is expressed as negative value on Y-axis

A

Retrograde

80
Q

On spectral analysis (graph) the peak systolic velocity is where

A

The top “peak” of the spikes

81
Q

On spectral analysis (graph) the envelope is where

A

All the white lines because it is the range of velocities

82
Q

On spectral analysis (graph) the window is where

A

Is the black part below the envelope (white stuff) and above the baseline

83
Q

On spectral analysis (graph) the dicrotic notch is where

A

The little second bump of the graph after the peak systolic velocity but before the end diastolic velocity

84
Q

On spectral analysis (graph) the end diastolic velocity is where

A

After the diacrotic notch the low part right before the peak systolic velocity

Ambers Physics 1 (7 decks)

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