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MIDS 197 > Ch 13 Spectral Doppler > Flashcards

Ch 13 Spectral Doppler Flashcards

1
Q

Hemodynamics is based on the investigation of what 2 physical principles?

A

Blood flow + circulation

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2
Q

The fundamental doppler principles are partly based on what principles?

A

Hydraulic principles: investigation of steady flow of a uniform fluid through a solid tube

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3
Q

Blood is not uniform due to what?

A

Containing solid matter

(it travels through “elastic tubes” which expand + contract)

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4
Q

Blood flow characteristics are based on a range of factors, list 5?

A

-Type of vessel (artery vs vein)
-Size of vessel
-Resistance to flow offered by vessel
-Phase of cardiac cycle the flow is occurring
-Disease processes which cause vessel narrowing

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5
Q

What is the driving force behind all fluid flow?

A

Pressure - differences in pressure is required for flow to occur

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6
Q

Does flow follow the path of least or most resistance?

A

Least - ex. higher pressure at 1 end of a tube than another causes fluid to move from an area of higher pressure to an area of lower pressure

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7
Q

Blood flows from the LA into the LV once when happens?

A

Once the pressure in the LA exceeds the pressure in the LV, causing the MV to open

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8
Q

Resistance to flow is determined by that 3 factors?

A

-Bloods viscosity
-Radius of vessels lumen
-Length of vessel

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9
Q

Rate of flow is determined by what 2 things?

A

-Pressure difference
-Resistance to flow

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10
Q

Define viscosity?

A

The ease in which fluid particles move past one another

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11
Q

Higher viscosity causes greater or lesser resistance to flow?

A

Greater

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12
Q

Define Poiseuille’s Law?

A

Relationship b/w flow rate, pressure difference + resistance

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13
Q

Define laminar flow?

A

Movement of fluid in “layers” or streamlines that travel parallel to one another, in the same direction + at approx the same velocity

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14
Q

List 4 types of laminar flow?

A

-Plug
-Parabolic
-Skewed
-Disturbed

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15
Q

Where would plug flow occur?

A

At entrance of a vessel where velocities of all streamlines are roughly the same, with the exception of mild disturbances caused by valves

Examples:
-RVOT + LVOT
-MV + TV inflows

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16
Q

Define parabolic flow? Where would this occur?

A

-Occurs in long, straight vessels.
-Walls cause friction + slowing of flow, while the center moves at a higher velocity

Examples:
-Peripheral vessels of cardiovascular system
-Pulmonary veins

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17
Q

Define curved skewed flow? Where would we see this flow?

A

-Asymmetric flow profile caused by vessel curvature.
-Higher velocities on the outside curve, lower velocities on the inside curve.

Example:
-Carotid artery

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18
Q

Define U-Shaped skewed flow? Where would we see this flow?

A

-Complex flow based on many variables.
-Higher velocities on inner side of ascending limb + on outer side of descending limb.

Example:
-Aortic arch

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19
Q

Define disturbed flow? Where would we see this flow?

A

-Laminar blood flow that is NOT traveling in a straight path.
-There is laminar flow at the outer walls of the vessel, then slower circular flow (Eddy flow) on the inner side of branches.

Example:
-PA Bifurcation

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20
Q

When would turbulent flow occur?

A

When blood passes through an area of obstruction or a narrowed orifice

Examples:
-Stenosis
-Regurgitation
-Septal defects

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21
Q

Flow obstructions increase or decrease velocities?

A

Increases - causing a curling whirlpool flow pattern called vortices (casts off jets at different velocities + directions)

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22
Q

If there is an increase in velocity at a narrowing/stenosis, what happens to the pressure?

A

There is a decrease + drop in pressure at the stenosis

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23
Q

According to the continuity principle, when there is a narrowed orifice will the blood velocity increase or decrease across it?

A

Must increase

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24
Q

The continuity principle is based on conservation of what?

A

Mass - “whatever mass flows in, must flow out”

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25
Q

Flow before a stenosis + after a stenosis must be greater, lesser or equal?

A

Equal

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26
Q

In order to maintain the same volume of flow, velocities at a stenosis will be greater or lesser than the velocity proximal + distal to the stenosis?

A

Greater

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27
Q

Volumetric flow rate relates to what 2 things?

A

-Average flow velocity
-Cross sectional area of particular location

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28
Q

When we want to doppler a structure, do we want the u/s beam parallel or perpendicular to blood flow?

A

Parallel

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29
Q

What does a cosine of 1 mean?

A

100% detectable doppler shift

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30
Q

What happens if the u/s beam is perpendicular to blood flow when we want to doppler?

A

No doppler shift will be recorded (cosine of 0)

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31
Q

Should we use angle correct for cardiac doppler applications?

A

No! B/c will likely only make things worse

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32
Q

How can we avoid errors in calculating the velocity of blood flow?

A

Ensuring the intercept angle of the u/s beam + direction of blood flow is as parallel as possible

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33
Q

We use doppler in various forms for hemodynamic assessment of the heart, what are they?

A

-Velocity + pressure measurements (PW + CW)
-Assessment of myocardial tissue velocities (TDI)
-Recognition of normal + abnormal blood flow (CD, PW, CW)

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34
Q

How can we differentiate CW + PW tracings?

A

CW: no spectral window
PW: spectral window (anechoic space in waveforms)

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35
Q

Should we use CD before using any type of doppler?

A

Yes!

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36
Q

What does the x-axis + y-axis represent in a spectral doppler display?

A

X-axis: time across cardiac cycle (adjusted by sweep speed)

Y-axis: velocity scale (adjustable by scale into m/s or cm/s)

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37
Q

Define antegrade + retrograde flow?

A

Antegrade: flow above baseline, towards probe
Retrograde: flow below baseline, away from probe

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38
Q

Define velocity (frequency shift)?

A

Measurable speed of flow

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39
Q

Define signal amplitude?

A

-Brightness of pixels
-Velocities are shown in shades of grey + correspond to the amplitude (dB) of the signal

40
Q

The brightness of a signal + the density of a signal relates to what?

A

The intensity of velocity present

41
Q

A min of how many spectral waveforms should be present in our tracings?

A

Min 3

42
Q

What is a “full envelope” in a spectral tracing?

A

Means there is a complete, full + clear waveform we can trace

43
Q

List 2 ways PW is recognizable?

A

-Spectral window present in waveforms (however abnormal flow may cause spectral broadening)

-Presence of a sample volume box (=)

44
Q

Does PW detect flow in 1 location or along the cursor line?

A

1 location - detects flow in the particular location the sample volume box is set + only that location

(useful for determining velocities in a specific location)

45
Q

Do we commonly adjust the sample volume box with PW doppler?

A

No, usually only with pediatrics. Can cause spectral broadening if box is set too large.

(do not need to worry about FR when changing sample volume box size)

46
Q

The length of the sample volume box (how big we make the box) with PW determines what?

A

The amount of time the pulses of u/s are being sent out for

47
Q

What is PRF determining with PW?

A

How often PW “samples” the velocities it encounters

48
Q

Does a higher PRF mean PW is taking more or less samples?

A

More

(higher PRF = more often it takes a sample, lower PRF = less often it takes a sample)

49
Q

When is the new signal sent out with PW?

A

Not until the original signal is received back

50
Q

PW needs how many samples per cycle to prevent aliasing?

A

2

(when doppler shift exceeds 1/2 PRF aliasing occurs)

51
Q

What is a disadvantage to PW?

A

-Is subject/prone to aliasing at higher velocities (b/c sampling 1 specific spot)

-Limited amount of sample time which limits how high of a velocity it can detect

(PW can’t “see” what it can’t sample)

52
Q

What describes the max doppler shift/max doppler velocity that can be displayed properly using PW?

A

The Nyquist limit (scale) - applies to any form of doppler

53
Q

The Nyquist limit is determined by what?

A

The sampling rate (PRF)

54
Q

List 2 ways that CW is recognizable?

A

-Lack of spectral window present in waveforms
-Lack of a sample volume box along cursor line

55
Q

How does CW detect flow?

A

-Along the entire cursor line
-U/s signals are constantly sent + received along the entire length of u/s beam, which accurately measuring high velocities

56
Q

What is an advantage to using CW?

A

Useful for determining high velocities that will be prone to aliasing

57
Q

What is a disadvantage of CW?

A

The constant signals on the entire beams make it difficult to tell what depth the signal is exactly coming from (range ambiguity)

58
Q

Do we measure what is more averaged amongst the spectral waveforms, or the waveform that is the outlier?

A

Always measure what is more averaged + constant throughout the tracing. Shows what is true to the pt.

59
Q

What word describes why it is important that Sonographers understand the way normal, waveforms appear, as well as their timing in the cardiac cycle?

A

Ambiguity

60
Q

In theory, the best CW signals will come from which probe?

A

Pedof/blind probe

61
Q

Why does the pedof probe give us the best CW signals?

A

-Smaller footprint (easier to angle for flow alignment, can get more parallel)
-Uses lower frequency (1.9 MHz) which improves sensitivity
-Higher “signal to noise” ratio (clearer spectral envelope)

62
Q

When is the pedof probe used?

A

Primarily in evaluating stenosis (m/c aortic)

63
Q

Is CW or PW ambiguous?

A

CW

64
Q

Spectral doppler is used to calculate what?

A

Pressure gradients b/w chambers

65
Q

Does spectral doppler allow quantification or qualification of the pressure gradient for areas of narrowing (ex. calcified AoV)?

A

Quantification

66
Q

What is the Bernoulli equation?

A

P = 4V^2

(P = pressure gradient, V = velocity)

67
Q

Solving for the Bernoulli equation gives us what information?

A

The pressure difference b/w 2 chambers at a specific point in time

68
Q

As velocity increases, does pressure increase or decrease?

A

Decreases

69
Q

Determine the max pressure gradient across the TV based on the max velocity (4.15 m/s) of the TV regurgitation?

A

P = 4V^2
P = 4(4.15)^2
P = 69.0 mmHg

70
Q

What does TDI + DTI stand for?

A

TDI: tissue doppler imaging
DTI: doppler tissue imaging

71
Q

What does TDI record?

A

Records velocities within the myocardium itself + at the corners of the MV + TV annuli

72
Q

List 3 variations/uses for TDI?

A

-Colors are overlaid on the 2D image to enhance definition (like a chroma map)
-Pseudo “color m-mode” of sorts by placing cursor through area of interest
-Sample volume box along cursor line to obtain a spectral waveform (our primary focus!!!)

73
Q

The red/blue colors with TDI indicates what?

A

Movement of tissue - tells us when the annulus is moving antegrade/retrograde

74
Q

Is myocardial velocity with higher or slower than blood?

A

Slower

75
Q

Is the TDI scale set much higher or lower when compared to PW + CW?

A

Lower - scale should be much lower than PW + CW

(don’t change the scale with tissue doppler)

76
Q

Does BART apply to tissue like it does for blood?

A

Yes!

77
Q

What is TDI primarily used for?

A

Assessing diastolic function/dysfunction of the LV + systolic function of RV

78
Q

List 4 other TDI applications we will learn more about in cardiac 2?

A

-Estimation of LV filling pressures
-Differentiating b/w restrictive + constrictive physiology
-Early diagnosis of genetic disease of the heart
-Differentiating athletic hearts from hypertrophic cardiomyopathy

79
Q

When should we adjust our spectral doppler scale?

A

-Adjust it to avoid cutting any waveform peaks off (increase scale to fix aliasing)
-Should show the signal of interest

80
Q

Waveforms of interest should take up how much of the spectral doppler screen?

A

Approx 2/3

81
Q

If we see stenosis, how can we optimize + adjust our spectral doppler scale to prepare for acquisition?

A

Increase our scale to make room for the waveforms b/c stenosis has high velocity

82
Q

The baseline is used along with the doppler scale to eliminate what?

A

Aliasing, the baseline should be optimized for the entire doppler signal

83
Q

Areas of antegrade flow will appear above or below the baseline? Where should we move the baseline?

A

Above - move the baseline down to make room in advance

84
Q

Areas of retrograde flow will appear above or below the baseline? Where should we move the baseline?

A

Below - move the baseline up to make room in advance

85
Q

How many beats should be displayed on a spectral tracing?

A

At least 3 beats

86
Q

A min sweep speed of what is recommended?

A

100 mm/s

87
Q

When would we adjust our sweep speed?

A

Fast HR: increase it (spreads out waveforms)
Slow HR: decrease it (shows more waveforms)

88
Q

What is the sample volume length m/c set at?

A

3mm (typically not necessary to adjust it)

89
Q

What can happen if we increase our sample volume length?

A

Possible to create more noise in our doppler signal + create spectral broadening

90
Q

What do wall filters do?

A

Allows for removal of high intensity, low velocity signals called clutter from our display

91
Q

What causes clutter in our tracings?

A

Can be due to movement of chamber walls or valve leaflets

92
Q

When might we turn our wall filter down very low?

A

When trying to detect very low velocities, so we can detect a doppler signal

93
Q

Why would we adjust our doppler gain in our spectral tracings?

A

For clear visibility of waveforms, while preventing artifact + clutter

(1dB is optimal gain level)

94
Q

What is spectral broadening?

A

It is the filling in of the PW doppler spectral windows, due to a wide range of velocities present in the sample volume box

95
Q

Do some pathologies occur during normal flow?

A

Yes, know cardiac cycle timing to help decipher what we are seeing

96
Q

What are 2 helpful tips to keep in mind when dopplering?

A

-Have cursor line as parallel to flow as possible
-May have to intentionally alter image + be off axis to align flow to cursor line

97
Q

Are velocities + pressure gradients under or overestimated the more perpendicular the jet is to our cursor?

A

Underestimated

MIDS 197 (15 decks)

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