Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Ultrasound Physics > Doppler Artifacts > Flashcards

Doppler Artifacts Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Aliasaing

A

Aliasing results when the Nyquist criterion is violated. When the Doppler frequency shift is greater than one half of the PRF, the Doppler signal wraps around either the spectrum (spectral Doppler) or the color scale (Color Doppler).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the two types of aliasing

A

True and Display

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what steps should be taken to determine if something is display or true aliasing

A
  1. Change baseline
  2. Change scale
  3. Switch to CW or change the PRP, window, depth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

will CW have aliasing

A

No because CW Doppler has an infinite max velocity as opposed to PW, which will have aliasing and range ambiguity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Does CW have aiasing

A

NO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When aliasing is true aliasing

A

Note that in this case, the aliasing is a true alias in that it is not possible to determine the actual peak velocity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what must happen if aliasing is true

A

Have to change transducer to a lower frequency transducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

when is color aliasing more likely to occur

A 
Center of a vessel 
angle closer to 0 or 180
Low scales
high transmit frequency
Bend, branch etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

range ambguity

A

potential to detect signals from deeper depths as the echo from the previous transmit events overlaps the echoe from the current trasnmit event

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

all pulsed wave modalities

A

exhibit range amnguity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what modality uses range ambiguity to its advantage

A

spectral doppler modality of HPRF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Spectral mirroring

A

artificial doppler signal displaying the opposite direction of the true flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can result in Spectral mirroring

A
  • Excessive transmit
  • Excessive receive gain
  • Superficial doppler with high frequency transducer
  • insonification angle close to 90 degrees
  • poor electronic design
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

when insonification angle is close to 90 degrees

A

elements on one side of the steer line will see flow towards the transducer whereas elements on the other side of the steer line will see flow away-spectral mirror

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Spectral Spread (Broadening)

A
  • spectral broadening occurs normally from differing blood velocities
  • Can have artificial broadening
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Artificial spectral spread can cause what

A

can smear out the spectrum and INCREASE The peak velcoity

17
Q

what creates spectral spread/broandening

A

insonification angles greater then 7- degrees at more superficial gate depths cause this artifact
Principle cause is that the angle to flow from each element of an array is slightly different

18
Q

Spectral spread causes what

A

Overestimation of the peak velocity as well as the diminishment of a spectral window

19
Q

what is spectral spread exacerbated by

A
  • Large array transducers (linear arrays)
  • Superficial gate location
  • Large insonification angles (esp over 60)
  • Excessive gain
20
Q

Blossoming artifact

A

Occurs when signal is over gained

-higher then true peak velocity as well as the potential loss or decrease of the spectral window in PW Doppler

21
Q

Wall Filter saturation

A

When dynamic range is not adequately reduced by wall filters, circuit saturation occurs

22
Q

wall filter saturation occurs when

A

Clutter signals are not adequately attenuated

23
Q

what does wall filter saturation appear as

A

Bright, white line within the spectrum

24
Q

Total internal reflection

A

Can result in a loss in spectral signals as indicated by the diagram

25
Q

Twinkle artifact

A

Result of instrinic machine noise seen with colour Doppler

26
Q

what does twinkle appear as

A

Focus of alternating colours on Doppler signal behind a reflective object (like calculi) which gives the appearance of turbulent blood flow

27
Q

Twinkle can detect what?

A

More sensitive for the detection of small stones and is highly dependant on machine settings

28
Q

When is twinkle most pronounced

A

When reflecting surface is rough

29
Q

Colour and Power Doppler Flash

A

As a short term flash of colour within the colour box related to relative motion between the patient and the transducer, not the actual flow

30
Q

Doppler Spectral Dropout

A

Occurs due to

  • Poor Doppler angle
  • Inadequate sensitivity
  • high wall filter settings relative to low flow velocities
  • inappropriate settings
  • low receiver gain
  • Refraction artifact
  • Shadowing artifact
31
Q

HPRF

A

Comporomise between CW and PW doppler that uses the artifact of range ambiguity to increase the max detectable velocity without aliasing (at the expense of some range resolution)

32
Q

In PW what determines the minimum PRP (therefore the max PRF)

A

The Doppler gate depth

33
Q

a doppler gate depth results in what

A

A longer travel time and therefore a lower maximum PRF

34
Q

Colour Doppler Dropout

A
  • Poor Doppler angle (close to 90 degrees)
  • high colour scale settings (PRF)
  • Inadequate sensitivity (transmit frequency to high with deeper depths, transmit power too low, weak signal from insignificant number of RBC, packet size small when imaging low flow, small, deeper vessels)
  • Inappropriate settings such as low receiver gain
  • Low colour priority setting (esp if 2D receiver gain is high)
  • refraction
  • Shadowing artifact
35
Q

______ _______occurs at shallow depth settings in PW doppler, this results in an echo from a deeper depth registering as if from a shallower depth

A

Range ambguity

36
Q

Spectral mirroring is evident as a mirrored spectrum in the _______direction of strong flow

A

Reverse

37
Q

Spectral broadening generally becomes a significant concern when using large ________arrays and insonifcation angles of ______or greater

A

linear, 70

38
Q

what can spectral broandening result in

A

inaccurate measurements leading to PSV overestimation and pressure gradient overstimulation

Ultrasound Physics (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions