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Physics > Lecture 21 > Flashcards

Lecture 21 Flashcards

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1
Q

Ultrasound basics

A

A sound wave of a particular freq is sent out
It bounces off a stationary structure
It returns at the same frequency we sent out

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2
Q

Doppler effect

A

Change in freq caused by the motion of a source, reflector or reciever

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3
Q

Doppler of US

A

Change in frequency caused by the motion of the reflector

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4
Q

Doppler shift is

A

Change in frequency

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5
Q

Doppler shift

A

Depending on whether the object is moving closer or farther away, the freq will come back higher or lower

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6
Q

Doppler shift equation

units

A

Fd=fR-fT

KHz

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7
Q

In the doppler shift when thing are getting closer together frequency goes

A

Up

Postive shift

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8
Q

Doppler shift getting farther apart, frequency goes

A

Down

Gives a negative fD

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9
Q

Doppler shift equation with velocity

A

,, ,fD= 2 x f0 x v / c

,f0 - fundamental f aka transmitted fT
, v - speed of blood flow
, c- propag speed

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10
Q

Velocity equation

A

V= 77 x fD / f0

Units cm/ms

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11
Q

In doppler we (4)

A

Fire a particular frequency
Measure the frequency that returns
Figure out the doppler shift
Can calculate how fast an object is moving

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12
Q

What happens in doppler if frequency goes up

A

When frequency goes up doppler shift goes up

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13
Q

What happens when doppler shift goes up

A

Frequency goes up to compensate and velocity doesnt change

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14
Q

Were not directly affecting the _____ by changing the frequency

A

Velocity

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15
Q

The doppler shift is the different between

A

The sent and returning frequencies of the sound wave

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16
Q

Doppler effect

A

Police speed detectors
Weather forecasting
Door openers
Burglar alarms

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17
Q

So far with doppler angle we assume our probe is

A

Parallel to blood flow

18
Q

If the angle of interrogation is non-zero _____ doppler shift will occur

A

Less

19
Q

We incorporate ______ to compnsate for the lesser shift

A

cos (angl)

20
Q

Doppler angle is

A

Angle between teh sound beam and the vessel

21
Q

Cos 0

A

1

hitting the vessel straight on

22
Q

Cos 30

A

0.87

23
Q

Cos 60

A

0.5

24
Q

Cos90

A

O

Hitting the vessel perpendicular

25
Q

Decreased dopller shift measurement = _____ velocity measurement

A

Decreased

26
Q

Techniques to get closer to 0 degrees

A

Heel toe
Phase (steer)
Angle correct

27
Q

Angle correct on US machine

A

Tell the machine that were off and it compensates, increases the velocity back to where it should be

28
Q

Increase in doppler angle, the ____ error in the speed calculation

A

Increase

29
Q

0 degree = ____% error

A

0.4%

30
Q

70 degrees = ____% error

A

32%

31
Q

In real life we work under _____ degrees

A

60

32
Q

Doppler displays

A

Colour
Spectral
Audible

33
Q

Colour doppler aka

A

Colour flow imaging

34
Q

Colour doppler defined by

A

Presence, speed, charactter and direction of flow

35
Q

Colour doppler assess a _____ area at a time

A

Very large compared to spectral doppler

36
Q

Colour ___________ on gray scale image

A

Superimposed

37
Q

Colour doppler often steeres via ____, to get closer to ____ degree to avoid if vessels are parallel to the surface

A

Phasing

90 degrees

38
Q

If returning echoes have a different freq than from emitted, ________ has occured

A

Doppler shift

39
Q

Depending on the sign of doppler shift

A

Its towards or away

Colour will be assigned to pixels

40
Q

In colour doppler, multiple _______ are sent per _______

A

Pulses are sent per scan line

Vs. One per scan line in B mode

41
Q

Doppler shift is calculated within

A

The signal processor

Physics (32 decks)

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