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Physics C/O 2026 > Ch19 Doppler > Flashcards

Ch19 Doppler Flashcards

1
Q

Doppler shift is also called

A

Doppler frequency

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2
Q

When blood cells move toward the transducer

A

Positive Doppler shift

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3
Q

What does the “2” in the Doppler equation represent

A

It accounts for transmission and reflection

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4
Q

What is the definition of speed?

A

Distance per time

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5
Q

What is the definition of velocity?

A

Distance per time AND direction

Doppler shift are velocities. They give us a speed and a direction

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6
Q

Which cos angel is accepted

A

60°

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7
Q

What is Doppler shift directly related to?

A

blood cell velocity
transducer frequency
cos

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8
Q

What is the equation for velocity?

A

Velocity(cm/s) = Doppler shift (khz) * propagation speed(cm/s)
—————————————————
2* transmitted frequency (Khz) * cos

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9
Q

X-axis of Doppler spectrum

A

Time

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10
Q

Away from the transducer =

A

Negative Doppler shift

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11
Q

Y-axis of Doppler spectrum =

A

Velocity

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12
Q

T or F
Perpendicular angle is the best Doppler measurement

A

False
Parallel is the best but not achievable

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13
Q

What angle do you want to be at?

A

60 °

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14
Q

What is the most common error in Doppler US

A

Aliasing

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15
Q

When there is an angle between the directions of the sound beam and the flow, what happens?

A

Doppler measures something less than the true velocity

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16
Q

What is the equation for measured velocity?

A

true velocity x cos

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17
Q

Displaying flow Below the baseline means

A

Flow away from the transducer

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18
Q

Which Doppler uses two crystals

A

Continuous wave Doppler

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19
Q

How many crystals does the pulsed wave Doppler have

A

1

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20
Q

What is the primary disadvantage of CW

A

Range ambiguity

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21
Q

T or F? Does pulsed wave have one crystal?

A

True

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22
Q

What is other disadvantage of CW Doppler

A

No TGC display

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23
Q

What is the definition of range ambiguity?

A

Sonographer will not know exactly where the sound is coming from

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24
Q

Advantages of CW Doppler

A

-Does not produce aliasing
-Ability to detect very high velocities

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25
What does triplex imaging includes
Anatomical image Tracing Color Doppler
26
Which has good range resolution PW or CW
PW
27
What are the advantages of Pulsed Wave?
Range Resoultion Sample Volume
28
gray shades on a doppler spectrum are related to
amplitude of the reflected signal or number of blood cells creating the reflection
29
What is the definition of range resolution
Being able to select the exact location where velocities are measured
30
What is the sample volume (gate)
Depending on where the gate is placed and the size of it will depend on the appearance of the spectral tracing
31
Where do you receive the most accurate information?
Place gate in valve jet (center of blood vessel) which is the fastest portion of the blood vessel
32
T or F? Centering and narrowing the gate will produce a clean and clear tracing
True
33
anything above the nyquist limit is
Aliasing
34
How does transducer frequency affect aliasing ?
Higher frequency create more aliasing
35
Less aliasing
slower blood velocity lower frequency transducer shallow gate (high PRF)
36
More aliasing
faster blood velocity higher frequency transducer deep gate (low PRF)
37
What is the equation of Nyquist limit?
PRF ——- 2
38
Does aliasing occur with CW Doppler
NO
39
What is the Nyquist limit?
the highest doppler frequency or velocity that can be measured without the appearance of aliasing
40
Increasing PRF raises the nyquist limit and reduces
Aliasing
41
Five techniques to avoid aliasing?
-Adjust scale -Lower frequency transducer -Use CW Doppler -Use baseline shift -Select new, shallow view
42
Eliminating aliasing ______ the ability to measure the maximum velocity with Doppler
improve
43
The black region in the middle of the color map indicates?
No Doppler shift
44
Color Doppler provides information on the location of flow and therefore:
is a pulsed ultrasound technique has range resolution is subject to aliasing
45
T or F When multiple colors appear, Colors near the black line is slower velocity
True
46
Color doppler reports what
average or mean velocities
47
Pulsed and Continuous (spectral) measures what
peak velocity
48
What information does the variance mode show
Laminar flow Turbulent flow
49
In variance mode, left =
Laminar flow
50
smaller less packet
less accurate doppler less sensitive to slow velocity or low flow higher frame rate; improved temporal resolution
51
large packet
more accurate doppler more sensitive to fast velocity or flow lower frame rate, degraded temporal resolution
52
Power mode is
non directional color doppler
53
In variance mode, Right=
Turbulent flow
54
in power doppler image
all vessels have the same color, regardless of the direction of blood flow
55
False echos that appears on our image are
Artifacts
56
Energy mode or color angio is also
Power Doppler
57
three advantages of power mode
increased sensitivity to low flow or velocity unaffected by doppler angles unless the angle is 90 no aliasing
58
T or F Color power Doppler is non-directional
True
59
Eliminating low frequency Doppler signal near the spectral baseline is
Wall filter
60
three disadvantages of power mode
no measurement of velocity or direction lower frame rates (reduced temp resoultion) susceptible to motion of the transducer, pt, soft tissues which may result in a burst of color, or flash artifact
61
Wall filter eliminates what Doppler shift artifacts
Clutter Ghosting
62
What is the form of mirror image artifact that appears on the spectral display?
Crosstalk
63

Physics C/O 2026 (12 decks)

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