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Physics C/O 2026 > Ch19 Doppler > Flashcards

Ch19 Doppler Flashcards

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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
Q

What does triplex imaging includes

A

Anatomical image
Tracing
Color Doppler

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26
Q

Which has good range resolution
PW or CW

A

PW

27
Q

What are the advantages of Pulsed Wave?

A

Range Resoultion

Sample Volume

28
Q

gray shades on a doppler spectrum are related to

A

amplitude of the reflected signal
or
number of blood cells creating the reflection

29
Q

What is the definition of range resolution

A

Being able to select the exact location where velocities are measured

30
Q

What is the sample volume (gate)

A

Depending on where the gate is placed and the size of it will depend on the appearance of the spectral tracing

31
Q

Where do you receive the most accurate information?

A

Place gate in valve jet (center of blood vessel) which is the fastest portion of the blood vessel

32
Q

T or F? Centering and narrowing the gate will produce a clean and clear tracing

A

True

33
Q

anything above the nyquist limit is

A

Aliasing

34
Q

How does transducer frequency affect aliasing ?

A

Higher frequency create more aliasing

35
Q

Less aliasing

A

slower blood velocity
lower frequency transducer
shallow gate (high PRF)

36
Q

More aliasing

A

faster blood velocity
higher frequency transducer
deep gate (low PRF)

37
Q

What is the equation of Nyquist limit?

A

PRF
——-
2

38
Q

Does aliasing occur with CW Doppler

A

NO

39
Q

What is the Nyquist limit?

A

the highest doppler frequency or velocity that can be measured without the appearance of aliasing

40
Q

Increasing PRF raises the nyquist limit and reduces

A

Aliasing

41
Q

Five techniques to avoid aliasing?

A

-Adjust scale
-Lower frequency transducer
-Use CW Doppler
-Use baseline shift
-Select new, shallow view

42
Q

Eliminating aliasing ______ the ability to measure the maximum velocity with Doppler

A

improve

43
Q

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

A

No Doppler shift

44
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

45
Q

T or F
When multiple colors appear, Colors near the black line is slower velocity

A

True

46
Q

Color doppler reports what

A

average or mean velocities

47
Q

Pulsed and Continuous (spectral) measures what

A

peak velocity

48
Q

What information does the variance mode show

A

Laminar flow
Turbulent flow

49
Q

In variance mode, left =

A

Laminar flow

50
Q

smaller less packet

A

less accurate doppler
less sensitive to slow velocity or low flow
higher frame rate; improved temporal resolution

51
Q

large packet

A

more accurate doppler
more sensitive to fast velocity or flow
lower frame rate, degraded temporal resolution

52
Q

Power mode is

A

non directional color doppler

53
Q

In variance mode,
Right=

A

Turbulent flow

54
Q

in power doppler image

A

all vessels have the same color, regardless of the direction of blood flow

55
Q

False echos that appears on our image are

A

Artifacts

56
Q

Energy mode or color angio is also

A

Power Doppler

57
Q

three advantages of power mode

A

increased sensitivity to low flow or velocity
unaffected by doppler angles unless the angle is 90
no aliasing

58
Q

T or F
Color power Doppler is non-directional

A

True

59
Q

Eliminating low frequency Doppler signal near the spectral baseline is

A

Wall filter

60
Q

three disadvantages of power mode

A

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
Q

Wall filter eliminates what Doppler shift artifacts

A

Clutter
Ghosting

62
Q

What is the form of mirror image artifact that appears on the spectral display?

A

Crosstalk

63
Q
A

Physics C/O 2026 (12 decks)

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