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Echo 2 > Doppler Review > Flashcards

Doppler Review Flashcards

1
Q

Define Doppler method

A

A method for detecting the direction and velocity of moving red blood cells and tissue within the heart

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2
Q

What does Doppler echo include

A

Colour flow imaging

Spectral Doppler

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3
Q

What is kind of Doppler is used in colour flow imaging

A

Power Doppler

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4
Q

What types of Doppler are involved in spectral Doppler

A

Pulsed wave (PW)
Continuous wave Doppler (CW)
Tissue Doppler

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5
Q

What is the doppler principle measuring

A

Frequency shift

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6
Q

What is the doppler shift formula

A

Df = fd– f0

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7
Q

F0

A

Transmitted beam frequnecy

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8
Q

Fd

A

Received beam frequency

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9
Q

V

A

Velocity of blood flow

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10
Q

C

A

Sound speed in the medium

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11
Q

What is the doppler shift formula for blood flow

A

Df = 2 x f0 x V x cos f/ C

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12
Q

What is the purpose of doppler in echo

A

Detect areas of NORMAL and ABNORMAL flow
Assess systolic and diastolic function
Provide functional information

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13
Q

What are the areas of abnormal flow that doppler can detect

A

Valves: stenosis/regurg
Shunts
Differentiate between tissue and areas of blood flow

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14
Q

What is the functional information that doppler in echo provides

A

Flow velocity

Pressure gradient through valves

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15
Q

What are the advantages of PW doppler

A

Range specificity
Adjustment of sample volume size and position
Able to map velocities at any point in the heart

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16
Q

What are the disadvantages of PW doppler

A

Inability to measure high velocities (>2.0-2.5m/s) due to aliasing
Is limited by the speed of sound in tissue and PRF

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17
Q

What is the main limitation of PW doppler due to

A

The NyQuil limit

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18
Q

What is the Nyquist limit

A

Approximately 1/2 PRF

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19
Q

When does aliasing occur

A

If the nyquist limit is exceeded

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20
Q

What is doppler CW

A

2 crystal transducer

-one for transmitting, one for receiving

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21
Q

What is the main advantage of CW doppler

A

High velocity range

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22
Q

What is the main disadvantage for CW doppler

A

No range resolution

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23
Q

Why is there no range resolution in CW doppler

A

Only maximum velocity is measured along a scan line

Unable to be sure that a velocity is coming from a specific location- can only assume

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24
Q

What does TDI use the same principle as

A

Blood flow

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25
Q

What does TDI measure

A

Movement of myocardial tissue

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26
Q

tissue doppler signal if of what intensity

A

Greater

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27
Q

When the tissue doppler signal is compared to the blood flow signal, which velocity is lower

A

Tissue doppler (e prime, s prime)

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28
Q

What is the machine automatically able to change the settings on for TDI

A

Filters set to exclude high velocities

Filters set to exclude weak reflectors (blood)

29
Q

What is the pros of tissue doppler

A

Easily reproducible
Provides systolic and diastolic information in one waveform
Can be preformed on TDS patients
Less volume (preload) dependant than MV inflow

30
Q

What are the cons of tissue doppler

A

Angle dependant
E primes should be measured at end expiration
Filter settings can vary widely between vendors
Gain setting can be to low on certain machines
Velocities will be lower than myocardium in rest of LV due to
-prosthetic valves, MAC, mitral annular ring

31
Q

What does the x axis represent on doppler signal display

A

Time in seconds

32
Q

What does the y axis represent on the doppler signal display

A

Direction + velocity (m/sec or cm/s)

33
Q

What does the z axis represent in doppler signal display

A

Brightness, strength of returning echo, # of cells at a particular velocity

34
Q

What does a strong signal represent in doppler signal display

A

More cells moving at that velocity

35
Q

What does a weak signal represent on doppler signal display

A

Less cells moving at that velocity

36
Q

In spectral Doppler the velocity range is adjusted so what happens to the waveform

A

So that it occupies at least 50% of the available scale

37
Q

What does blue represent in colour doppler

A

Flow away from the probe

38
Q

What does red represent in colour doppler

A

Flow towards the probe

39
Q

What does green indicate in colour doppler

A

Turbulence

40
Q

What is colour doppler

A

A pulsed wave technique, subject to aliasing

41
Q

What happens when the colour doppler aliases

A

The flow direction becomes ambiguous

42
Q

In the heart how can the flow direction change

A

It can change within one structure during the cardiac cycle

43
Q

What does flow direction add to cardiac scanning

A

A dynamic component

44
Q

If we call flow “normal” in cardiac scanning what are we referring to

A

Directional flow during a particular portion of the cardiac cycle

45
Q

Is colour doppler effected by the nyquist limit

A

Yes

46
Q

What are the advantages of colour doppler

A

Sensitivity
Region of interest
Laminar vs turbulent flow

47
Q

What are the disadvantages of colour doppler

A

Aliasing

Directional ambiguity

48
Q

What does the Bernoulli equation outline

A

The relationship between velocity and pressure

49
Q

As velocity of a moving fluid increases what what happens to the pressure within the fluid

A

Decreases

50
Q

What does the drop in pressure create

A

A pressure difference between the region proximal to a narrowing and within the narrowing

51
Q

What is the simplified Bernoulli equation

A

P1-P2=4V^2

52
Q

When is the modified Bernoulli equation used

A

To assess maximum instantaneous and mean pressure gradients

53
Q

What is the maximum gradient calculated from

A

The maximum velocity

54
Q

How is the mean gradient calculated

A

By averaging the instantaneous gradients over the ejection period

55
Q

Pressure gradient estimations can be underestimated by

A

Non-parallel sampling of blood flow

56
Q

A 20 degree offset from flow direction = what

A

6% underestimation of blood flow velocity

57
Q

When the offset degree is factored into the Bernoulli equation what will happen

A

The error will be much higher because the velocity is squared

58
Q

If an arrhymia is present what must be measured for pressure gradient estimations

A

3-5 beats, they will than be averaged

59
Q

What are other factors that will underestimate the pressure gradients

A

Significant flow acceleration
Viscous forces
Increased proximal velocities

60
Q

Are prosthetic valves heavier than normal valves

A

Yes

61
Q

What are the different types of viscous forces

A

Long, tubular stenosis
When a stenosis is >10mm in length
Eccentric wall jets

62
Q

In a normal heart where there is no significant regurg or shunts, the SV through all 4 valves will be what

A

The same

63
Q

The stroke volume through a regurgitant valve will be what than through a competent valve

A

Higher

64
Q

The SV through a regurgitant valve will include what

A

The volume of the leak and the normal SV

65
Q

What is the equation for SV

A

SV(rv)= SV(cv)+ RV

66
Q

What is the equation for the regurgitant calculation

A

RF=RV/SV

67
Q

What does the Dp/Dt measure

A 
The rise (or fall) of pressure divided by the change in time 
How quickly the LV can generate pressure
68
Q

What is the Dp/Dt most often used for

A

Assess LV global systolic function

69
Q

When is Dp/Dt only done

A

When MR is present

Echo 2 (6 decks)

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