Artifacts

Question 1

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

Answer 1

a. rectangular, parallelogram

Question 2

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

Answer 2

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

Question 3

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

Answer 3

b. Fast Fourier Transforms

Question 4

Spectral analysis of color flow Doppler is most commonly performed by which of the following techniques?

a. zero-crossing detectors
b. Fast Fourier Transforms
c. autocorrelation
d. Chirp-Z transforms

Answer 4

c. autocorrelation

Question 5

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

Answer 5

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

Question 6

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

Answer 6

e. none of the above

Question 7

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

Answer 7

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

Question 8

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 imaging
d. longitudinal resolution

Answer 8

a. reverberation

Question 9

Which situation will commonly produce 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

Answer 9

c. two strong reflectors that lie along the main axis of the beam

Question 10

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

a. weak reflectors, closely spaced, low propagation speed
b. strong reflectors, widely spaced, high propagation speed
c. strong reflectors, closely spaced, low propagation speed
d. strong reflectors, closely spaced, high propagation speed

Answer 10

d. strong reflectors, closely spaced, high propagation speed

Question 11

What is the most likely cause of ring down artifact?

a. refraction
b. inversion
c. reabsorption
d. reflection

Answer 11

d. reflection

Question 12

Where 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

Answer 12

c. deeper than a structure with a high attenuation

Question 13

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

Answer 13

d. reflectors being absent on the image

Question 14

What of these produces shadowing?

a. reverberation
b. multipath
c. reflection
d. attenuation

Answer 14

d. attenuation

Question 15

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

Answer 15

c. unexpectedly low acoustic attenuation

Question 16

Unexpectedly low attenuation results in which of the artifacts listed below?

a. refraction
b. attenuation
c. enhancement
d. shadowing

Answer 16

c. enhancement

Question 17

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

a. in the near field
b. deeper than a weak attenuator
c. in the far field
d. shallower than a weak reflector

Answer 17

b. deeper than a weak attenuator

Question 18

Acoustic focusing of an ultrasound beam may create which artifact?

a. side lobes
b. refraction
c. speckle
d. enhancement

Answer 18

d. enhancement

Question 19

Which process causes mirror image artifact?

a. reflection
b. refraction
c. propagation speed error
d. attenuation

Answer 19

a. reflection

Question 20

Where is a mirror image artifact located?

a. sometimes shallower on the image than in the body
b. always deeper on the image than in the body
c. sometimes the same depth on the image as in the body
d. never deeper on the page than in the body

Answer 20

b. always deeper on the image than in the body

Question 21

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

a. lateral resolution
b. slice thickness
c. mirror imaging
d. longitudinal resolution

Answer 21

c. mirror imaging

Question 22

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

Answer 22

a. vertical misregistration

Question 23

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

Answer 23

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

Question 24

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. they are placed in too shallow a location on the image
b. they are placed in too deep a location on the image
c. they are likely to be placed at the correct depth

Answer 24

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

Question 25

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. they are placed in too shallow a location on the image
b. they are placed in too deep a location on the image
c. they are likely to be placed at the correct depth

Answer 25

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

Question 26

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

Answer 26

c. range ambiguity

Question 27

What causes side lobe 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

Answer 27

d. acoustic energy radiating in a direction other than the beam’s main axis

Question 28

Side lobe artifact usually results in all of the following expect _____.

a. hollow structures appearing “filled in” on the image
b. reflectors not appearing on an image
c. reflectors appearing in improper locations on the image
d. reflectors appearing in multiple locations on the image

Answer 28

b. reflectors not appearing on an image

Question 29

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

a. annular array
b. continuous wave
c. mechanical scanners
d. linear arrays

Answer 29

d. linear arrays

Question 30

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

a. side lobes
b. reverberation
c. transaxial lobes
d. acoustic speckle

Answer 30

a. side lobes

Question 31

True or False?

Grating lobes are a result of substantial acoustic energy directed outward from a linear array transducer, but not along the main axis of the sound beam.

Answer 31

True

Question 32

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

a. demodulation
b. subduing
c. deconvolution
d. none of the above

Answer 32

b. subduing

Question 33

True or False?

Grating lobes are attributed only to array transducers.

Answer 33

True

Question 34

Which artifact results in improper side-by-side positioning of reflectors?

a. multipath
b. comet tail
c. refraction
d. reverberation

Answer 34

c. refraction

Question 35

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 place is very thin

Answer 35

c. sound travels in a straight line

Question 36

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

a. axial resolution
b. lateral resolution
c. elevational resolution

Answer 36

c. elevational resolution

Question 37

What artifact results from an ultrasound beam having a finite and measurable three-dimensional profile?

a. acoustic speckle
b. multiparty artifact
c. slice thickness artifact
d. grating lobe artifact

Answer 37

c. slice thickness artifact

Question 38

How does slice thickness artifact commonly express itself?

a. fill in of cystic structures
b improper brightness of reflectors
c. absence of reflectors
d. strong linear echoes

Answer 38

a. fill in of cystic structures

Question 39

With depth resolution, _______.

a. too many reflectors appear on the image
b. reflectors are placed too deep on the image
c. too few reflectors are on the image
d. reflectors appear too shallow on the image

Answer 39

c. too few reflectors are on the image

Question 40

Axial resolution artifacts are due to which of the following?

a. multiple reflections
b. beam width
c. attenuation
d. pulse length

Answer 40

d. pulse length

Question 41

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

a. 10 MHz, 8 mm beam diameter, 6 cycles per pulse
b. 4 MHz, 4 mm beam diameter, 2 cycles per pulse
c. 9 MHz, 8 mm beam diameter, 2 cycles per pulse
d. 6 MHz, 2 mm beam diameter, 2 cycles per pulse

Answer 41

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

Question 42

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

a. 10 MHz, 4 mm beam diameter, 4 cycles per pulse
b. 4 MHz, 4 mm beam diameter, 2 cycles per pulse
c. 7.5 MHz, 8 mm beam diameter, 2 cycles per pulse
d. 6 MHz, 2 mm beam diameter, 2 cycles per pulse

Answer 42

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

Question 43

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

Answer 43

b. 4 mm

Question 44

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 mages on the system’s display?

a. the beam width
b. the pulse length
c. the PRF
d. the TGC

Answer 44

a. the beam width

Question 45

Which artifact is not related to the unexpected reflection of an acoustic wave?

a. multipath
b. comet tail
c. reverberation
d. lateral resolution

Answer 45

d. lateral resolution

Question 46

True or False?

Side lobe, grating lobe, and refraction artifacts all reduce lateral resolution.

Answer 46

True

Question 47

True or False?

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

Answer 47

True

Question 48

True or False?

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

Answer 48

False

Question 49

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

a. axial resolution
b. lateral resolution
c. neither; they have identical values

Answer 49

b. lateral resolution

Question 50

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

a. reflection
b. rarefaction
c. refraction
d. attenuation

Answer 50

a. reflection

Question 51

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

a. poor angular resolution
b. creation of hyperechoic regions
c. mild image degradation
d. gross horizontal misregistration

Answer 51

c. mild image degradation

Question 52

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

a. strength of the electron beam
b. form of phosphor coating of the screen
c. number of lines of the monitor’s display
d. the pulse duration

Answer 52

c. number of lines of the monitor’s display

Question 53

What is the cause of acoustic speckle?

a. refraction
b. attenuation
c. interference of tiny acoustic wavelets
d. resonance of particles in the near field

Answer 53

c. interference of tiny acoustic wavelets

Question 54

What is true of acoustic speckle?

a. its effects are mild and it tends to slightly degrade images
b. it is a rare artifact that does not occur in real-time imaging
c. its effects are dramatic
d. it is eliminated with apolarization

Answer 54

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