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Ultrasound Physics > Optimizing Doppler Imaging & Artifacts > Flashcards

Optimizing Doppler Imaging & Artifacts Flashcards

1
Q

While using a linear sequential array transducer during a color Doppler exam, the shape of the gray scale image is most often ____, whereas the shape of the color Doppler portion of the image is ____
A. rectangular, parallelogram
B. rectangular, sector
C. sector, trapezoid
D. square, rectangular

A

A. rectangular, parallelogram

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2
Q

What is the meaning of the term “analysis” in the context of spectral analysis of Doppler signals?
A. building a sophisticated signal from components
B. building a simplified signal from components
C. identifying the building blocks or components of a complex signal
D. measuring a complex signal, then modifying its information content

A

C. identifying the building blocks or components of a complex signal

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3
Q

The analysis of Doppler spectra using ____ is most accurate
A. zero-crossing detectors
B. Fast Fourier Transforms
C. time interval histograms
D. Chirp-Z transforms

A

B. Fast Fourier Transforms

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4
Q

Acoustic artifacts include: (More than one answer may be correct.)
A. images of reflectors in an inappropriate position
B. images of reflectors with improper shape
C. images of reflectors with incorrect brightness
D. images that do not correspond to anatomical structures

A

A,B,C, and D

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5
Q

Which of the following is not a potential cause of artifact in diagnostic imaging?
A. operator error
B. equipment malfunction
C. patient motion
D. ultrasound physics
E. none of the above

A

E. none of the above

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6
Q

Ultrasound systems are designed to automatically ______
A. display similar structures with equal brightness, regardless of depth
B. position structures at the correct depth, regardless of the medium
C. display all reflections on a line corresponding to the main axis of the sound beam, regardless of refraction
D. select the optimal beam width based on the clinical application

A

C. display all reflections on a line corresponding to the main axis of the sound beam, regardless of refraction

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7
Q

Six distinct, equally spaced reflections appear on an image at ever increasing depths. What type of artifact is this?
A. reverberation
B. ring down
C. mirror image
D. longitudinal

A

A. reverberation

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8
Q

Which situation will commonly produces reverberation artifact?
A. two masses that lie perpendicular to the sound beam’s main axis
B. two weak reflectors that lie close to each other along the axis of the beam
C. two strong reflectors that lie along the main axis of the beam
D. a single highly reflective mass

A

C. two strong reflectors that lie close to each other along the axis of the beam

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9
Q

What are the characteristics of a medium that produces come tail artifact?

A

D. strong reflectors, closely spaced, high propagation speed

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10
Q

What is the most likely cause of ring down artifact?
A refraction
B. inversion
C. reabsorption
D. reflection

A

D. reflection

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11
Q

What are shadowing artifacts commonly seen on an acoustic scan?
A. deeper than a structure with a high impedance
B. shallower than a structure with a low propagation speed
C. deeper than a structure with a high attenuation
D. alongside of a structure with a low elastance

A

C. deeper than a structure with a high attenuation

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12
Q

How is shadowing artifact expressed?
A. positioning structures too deep on the image
B. locating structures in improper lateral position
C. placing reflections in multiple locations
D. reflectors being absent on the image

A

D. reflectors being absent on the image

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13
Q

Which of these produces shadowing?
A reverberation
B. multipath
C. reflection
D. attenuation

A

D. attenuation

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14
Q

What causes enhancement artifact?
A. sound beams bending
B. linear array transducer architecture
C. unexpectedly low acoustic attenuation
D. acoustic energy radiating in a direction other than the beam’s main axis

A

C. unexpectedly low acoustic attenuation

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15
Q

When enhancement occurs, where does it appear on the image?

A

B. deeper than a weak attenuator

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16
Q

Acoustic focusing of an ultrasound beam may create which artifact?

A

D. enhancement

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17
Q

Which process causes mirror image artifact?

A

A. reflection

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18
Q

Where is a mirror image artifact located?

A

B. always deeper on the image than in the body

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19
Q

Which artifact is not affected by the shape or dimensions of an ultrasound pulse?

A

C. mirror imaging

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20
Q

Which artifact is created by sound moving through a medium with a propagation speed less than soft tissue?
A. vertical misregistration
B. horizontal misregistration
C. lateral resolution
D. ring down

A

A. vertical misregistration

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21
Q

While imaging a test object, an ultrasound system displays one image 1.8 cm deeper than another. Upon measuring the test object, it is found that it is actually 2.0 cm deeper. What conclusion can be drawn from this?
A. speed of sound in the test object is the same as soft tissue
B. speed in the test object is less than that in soft tissue
C. attenuation of sound in the test object is less than that in soft tissue.
D. speed in soft tissue is less than that of the test object

A

D. speed in soft tissue is less than that of the test object

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22
Q

If an ultrasound pulse travels through a large mass in the body at a speed of 1.2 mm/us, what happens to the position of all echoes produced from reflectors shallower than the mass?

A

C. they are likely to be placed at the correct depth

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23
Q

If a sound pulse travels through a large mass at a speed of 1.2 mm/us, what happens to the position of echoes from reflectors deeper than the mass?

A

B. they are placed in too deep a location on the image

24
Q

What type of artifact causes a reflection to be placed at an incorrect depth?
A. lateral incertitude
B. shadowing
C. range ambiguity
D. indeterminate relaxation

A

C. range ambiguity

25
Q

What causes side lobe artifacts?
A. sound beams bending
B. linear array transducer architecture
C. unexpectedly low acoustic attenuation
D. acoustic energy radiating in a direction other than the beam’s main axis

A

D. acoustic energy radiating in a direction other than the beam’s main axus

26
Q

Side love artifact usually results in all of the following except _______
A. hollow structures appearing “filled in” on the image
B. reflectors not appearing in improper locations on the image
C. reflectors appearing in improper locations on the image
D. reflectors appearing in multiple locations on the image

A

B. reflectors not appearing in improper locations on the image

27
Q

Grating lobes are most common with which type of transducer technology?

A

D. linear arrays

28
Q

Grating lobes are produced by the same mechanism as which other artifact?

A

A. side lobes

29
Q

T/F: Grating lobes are a result of substantial acoustic energy directed outwards from a linear array transducer, but not along the main axis of the sound.

A

True

30
Q

Which technique of linear array transducer design has virtually eliminated the appearance of the grating lobe artifact on modern ultrasound systems?

A

B. subdicing

31
Q

T/F: Grating lobes are attributed only to array transducer

A

True

32
Q

Which artifact results in improper side-by-side positioning of reflectors
A. multipath
B. comet tail
C. refraction
D. reverberation

A

C. refraction

33
Q

What assumption is violated when a refracted sound wave is processed?
A. waves travel directly to and from a reflector
B. sound travels at an average speed of 1.54 mm/us
C. sound travels in a straight line
D. the acoustic imaging plane is very thin

A

C. sound travels in a straight line

34
Q

With standard diagnostic imaging instrumentation, which has the higher numerical value?
A. axial resolution
B. lateral resolution
C. elevational resolution

A

C. elevational resolution

35
Q

What artifact results from an ultrasound beam having a finite and measurable three-dimensional profile?
A. acoustic speckle
B. multipath artifact
C. slice thickness artifact
D. grating lobe artifact

A

C. slice-thickness artifact

36
Q

How does slice thickness artifact commonly express itself?

A

A. fill in of cystic structures

37
Q

With depth resolution ______.

A

C. too few reflectors are on the image

38
Q

Axial resolution artifacts are due to which of the following?
A. multiple reflections
B. beam width
C. attenuation
D. pulse length

A

D. pulse length

39
Q

Which of these pulses is least likely to produce an axial resolution artifact?

A

C. 9MHz, 8mm beam diameter, 2 cycles per pulse

40
Q

With which of the following pulses would lateral resolution be worst?

A

C. 7.5 MHz, 8mm beam diameter, 2 cycles per pulse

41
Q

The lateral resolution of four ultrasound systems appear below. Which will produce the finest quality picture?
A. 2 cm
B. 4 mm
C. 6 mm
D. 8 hm

A

B. 4 mm

42
Q

Two small cysts, positioned perpendicular to the main axis of a sound beam, are 2.4 mm apart. What determines whether they appear as two distinct images on the system’s display?

A

A. the beam width

43
Q

Which artifact is not related to the unexpected reflection of an acoustic wave?
A. multipath
B. comet tail
C. reverberation
D. lateral resolution

A

D. lateral resolution

44
Q

T/F: Side lobe, grating lobe, and refraction artifacts all reduce lateral resolution.

A

True

45
Q

T/F: Artifacts are likely to appear when the dimensions of the sound beam area are larger than the dimensions of the reflectors in the body.

A

True

46
Q

T/F: All artifacts are errors in imaging that do not represent the true anatomy of the imaged organ. Therefore, they are all undesirable and should be eliminated if possible.

A

False

47
Q

With standard diagnostic imaging instrumentation, which has the higher numerical value?

A

B. lateral resolution

48
Q

What is a comet tail artifact’s fundamental mechanism of formation?

A

A. reflection

49
Q

In diagnostic imaging, how does multipath artifact affect the image?

A

C. mild image degredation

50
Q

Which of the following determines the spatial resolution of an image on a monitor?

A

C. number of lines of the monitor’s display

51
Q

What is the cause of acoustic speckle?

A

C. interference of tiny acoustic wavelets

52
Q

What is true of acoustic speckle?

A

A. its effects are mild and it tends to slightly degrade images.

53
Q

Artifacts include reflections that are described as:

A
  • not real
  • not seen on the image
  • incorrect shape or size
  • incorrect position
  • incorrect brightness
54
Q

Artifacts result from:

A
  • violation of assumptions
  • equipment malfunction or poor design
  • the physics of ultrasound
  • operator error
55
Q

What eliminates low frequency Doppler shifts?

A

Wall Filter: removes the color from slowly moving reflectors such as blood cells and vibrating tissues

56
Q

Does increasing the color Doppler scale decrease the sensitivity to flow flows?

A

Yes; increasing scale removes aliasing

Ultrasound Physics (2 decks)

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