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Vascular Test 1 > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

what is the doppler shift?

A

the frequency of a reflected wave is different than the transmitted beam

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2
Q

what is the doppler shift

A

the difference between the incident frequency and the reflected frequency

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3
Q

RBCs moving towards the transducer are?

A

compressed= higher frequency

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4
Q

RBCs moving away are

A

expanded=lower frequency

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5
Q

positive doppler shift

A

towards transducer

above baseline

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6
Q

negative doppler shift

A

away from transducer

below baseline

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7
Q

is doppler shift in the audible range?

A

yes!

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8
Q

what is the doppler shift dependent on?

A

direction of movement

speed at which the target is moving

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9
Q

angle of incidence

A

angle formed by the axis of the incident sound beam and the incident flow

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10
Q

incident frequency

A

emitted from the doppler transducer

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11
Q

reflected frequency

A

returning to the doppler transducer

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12
Q

what kind of info is derived from doppler investigation?

A
  • direction of blood flow
  • velocity
  • range of velocities
  • type of flow
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13
Q

PW doppler

A

listens at one gate

has great range resolution

precise locations

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14
Q

CW doppler

A

listening along entire beam

wide range of velocities

separate crystals send and receive

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15
Q

info obtained by spectral analysis

A

type of flow

PS velocity

ED velocity

range of velocities

spectral window

direction of flow

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16
Q

describe laminar flow

A

orderly flow, most RBC are the same velocities

17
Q

describe turbulent flow

A

can be change of flow direction due to stenosis or tortuosity

18
Q

what happens to the doppler shift when you increase the angle

A

decreases

19
Q

when is maximum flow detected?

A

when the flow is moving directly toward or away the transducer

20
Q

lateral resolution is determined by what?

A

the beam width

21
Q

daxial dimension is determined by what?

A

the pulse length

22
Q

PRF is limited by what?

A

depth

23
Q

what is the nyqusit limit?

A

it is ½ PRF and if exceeded aliasing occurs

24
Q

aliasing is caused by?

A

long travel time

high velocity

25
Q

aliasing

A

an incorrect estimation of the frequency of a signal due to insufficient sampling of the signal

26
Q

how can you correct aliasing

A
  • increase PRF
  • lower baseline
  • decrease probe frequency
  • increase angle
  • decrease depth
27
Q

doppler effect

A
28
Q

doppler formula

A
29
Q

Angle of Incidence:

A

Angle formed by the axis of the incident sound beam and the incident flow.

Vascular Test 1 (4 decks)

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