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Ambers Physics 1 > Doppler Principles > Flashcards

Doppler Principles Flashcards

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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
What is the more detailed formula for doppler shift and what does it show the relationship between
(2*operating frequency)(velocity)(cos feta) Doppler shift = ——————————————————— Speed of sound
26
In the doppler shift equation what is the most meaningful component to sonographers
V (velocity of RBC)
27
The operating frequency has a —— relationship with the doppler effect
Linear
28
If the operating frequency increases what happens to the doppler Shift
Doppler shift increases as well
29
If frequency is higher/increases what happens to resolution and penetration
``` Increase resolution Decrease penetration (due to attenuation) ```
30
Since RBC return very little intensity a lower or higher frequency probe is needed for doppler
Lower frequency
31
In duplex scanning does the image or doppler use higher or lower frequencies
Image - higher | Doppler - lower
32
RBC has what kind of relationship with the doppler shift
Linear relationship
33
As RBC move faster the difference in the returning frequency increases therefore the doppler shift ——
Increases as well
34
What is extremely important in doppler
Angle
35
The cosine of 90 degrees is zero. Therefore when the beam is perpendicular to the vessel what happens to doppler shift
Doppler shift cannot be calculated
36
What impacts the velocity calculated in the equation? Because it must be consistent for proper patient care
Angle of insonation
37
What is the most accurate angle for the correct calculation of velocity
Zero degrees (cosine 1)
38
As —— increases so does the percent error for velocity
Angle of insonation
39
The calculation of RBC velocity is only as good as the accuracy of the
Angle
40
How does a sonographer ensure the angle is accurate
Setting the angle to 60 degrees and heel toe probe until the angle indicator line is parallel to flow
41
What is the limit reached when the RBC velocities are faster then the machines ability to sample called
Nyquist limitation
42
The rate at which pulses are sent out are limited by
The speed of sound in tissue
43
The nyquist limit is equal to
1/2 the PRF
44
1/2 PRF usually falls in which range
5-30 kHz
45
An artifact that occurs when the Nyquist limit is exceeded is known as
Aliasing
46
Aliasing is shown like what on a graph
Parts of the signal are wrapped around the baseline | Blood cells are not being sampled fast enough so false readings occur
47
Correcting aliasing can be done in which 5 ways
``` Move baseline (real life) Increase PRF (real life) Increase doppler angle - heel toe probe Lower the operating frequency Change to continuous wave ```
48
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
Range ambiguity
49
What should be positioned in the middle of the vessel, or where the fastest velocity flow occurs
The gate
50
—— allows several depths to be sampled simultaneously
Multi-gating
51
The sample volume is created because of the
Range equation
52
The sample volume is determined by what 3 factors
The beam width The receiver gate length The length of the emitted pulse (number of cycles in pulse)
53
The overall sample volume is equal to what
1/2 pulse length. Plus. Gate length
54
If the gate length is reduced what must happen to the pulse length
Pulse length must also be reduced
55
A bigger/smaller gate length will improve spectral display
Smaller
56
Longer/shorter pulses are required to improve the accuracy of the doppler shift
Longer
57
To achieve a more accurate beat frequency the pulse duration must be
Longer
58
A minimum of —— cycles/pulse are required for color and spectral
4 (typically at 30)
59
In 2D scanning a short or long pulse duration is best
Short
60
Range gating is not possible with what kind of doppler
Continous wave
61
CW doppler sample is found at the intersection of the transmitted and received beam and tends to be about how big
5-6 cm
62
The zone where the transmitted and received beams intersect is known as the
Zone of sensitivity
63
With a large sample volume it is possible to do what and it would result in a very complex spectral tracing
Possible to pick up more then one vessel
64
When the beam intersects flow, echos are produced and many different ——— are returned to the vessel
Doppler shifts
65
The spectrum created is a range of generated doppler shift frequencies from —— that pass through the sample volume
From each RBC
66
What term means “to take part”
Analysis
67
The spectrum is an array of the components of a wave arranged in order of ———— over ——
Increasing frequency over time
68
The spectral tracing of doppler frequencies generated by moving blood that we see are plotted along the following 3 axes
Time (x) Frequency or velocity (y) Power (z)
69
The power (Z-axis) is represented by what
Brightness of pixels
70
The brightness of pixels (power)(z-axis) is proportional to
The number of cells moving at one velocity at a given time
71
The greater the number of RBC contained in a sample the —— the waveform
Brighter
72
The way in which the system creates the spectral trace is through a process of
Fast Fourier Transform (FFT)
73
What is FFT
A mathematical technique that separates the individual doppler shifts from the complex beat frequency
74
The Y-axis can represent what two things
Frequency of doppler shift | Velocity of RBC
75
Frequency is expressed in what units | Velocity is expressed in what units
Frequency kHz | Velocity cm/s m/s
76
Is frequency or velocity preferred for on the y-axis and why
Velocity. Because it compensates for variations in vessel alignment relative to surface and more meaningful to technologist
77
When assessing flow direction on a spectral trace it is relative to
The transducer
78
What word means, flow towards the probe and is expressed as positive number on Y-axis
Antegrade
79
Which word means flow away from probe and is expressed as negative value on Y-axis
Retrograde
80
On spectral analysis (graph) the peak systolic velocity is where
The top “peak” of the spikes
81
On spectral analysis (graph) the envelope is where
All the white lines because it is the range of velocities
82
On spectral analysis (graph) the window is where
Is the black part below the envelope (white stuff) and above the baseline
83
On spectral analysis (graph) the dicrotic notch is where
The little second bump of the graph after the peak systolic velocity but before the end diastolic velocity
84
On spectral analysis (graph) the end diastolic velocity is where
After the diacrotic notch the low part right before the peak systolic velocity

Ambers Physics 1 (7 decks)

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