Chapter 07: Imaging and Doppler Artifacts

Hagen-Ansert: Textbook of Diagnostic Sonography, 8th Edition

Multiple Choice

1. Lack of axial and lateral resolution result in: a. echoes originating only from the center of the beam. b. decrease in ultrasound pulse length and width in the scan plane. c. Failure to resolve structures and detail loss. d. beam width artifacts on the scan plane.

ANS: C

Axial and lateral (detail) resolutions are artifactual because a failure to resolve means a loss of detail, and two adjacent structures may be visualized as one.

PTS: 1 REF: p. 120

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Propagation

2. Multiple reflections can occur between the transducer and a strong reflector. This is an example of: a. reverberation. b. mirror image. c. speckle tracking. d. refraction.

ANS: A

The multiple echoes may be sufficiently strong to be detected by the instrument and to cause confusion on the display. The multiple reflections are placed beneath the real reflector at separation intervals equal to the separation between the transducer and the real reflector.

PTS: 1 REF: p. 120

OBJ: Describe how specific artifacts can be recognized. TOP: Propagation

3. The artifact that shows structures that exist on one side of a strong reflector as being present on the other side as well is known as: a. range ambiguity. b. mirror image. c. refraction. d. speed error.

ANS: B

Mirror-image artifacts also a form of reverberation, shows structures that exist on one side of a strong reflector as being present on the other side as well.

PTS: 1 REF: p. 121

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Propagation

4. The reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure is: a. enhancement. b. resonance. c. comet tail. d. shadowing.

ANS: D

A shadow is present when strongly attenuating or reflecting structure weakens the sound distal to it, causing echoes from the distal region to be weak and thus to appear dark.

PTS: 1 REF: p. 127

OBJ: Describe how specific artifacts can be recognized. TOP: Attenuation

5. The strengthening of echoes from reflectors that lie behind a weak attenuating structure is: a. aliasing. b. multiple reflection. c. resonance. d. enhancement.

ANS: D

Enhancement results in reflectors being placed on the image with amplitudes that are too high.

PTS: 1 REF: p. 128

OBJ: Describe how specific artifacts can be recognized. TOP: Attenuation

6. Insufficient sampling during a Doppler study that results in the improper representation of information is known as: a. multiple reflection. b. resonance. c. aliasing. d. enhancement.

ANS: C

Aliasing in its technical use indicates improper representation of information that has been insufficiently sampled.

PTS: 1 REF: p. 129

OBJ: List ways in which spectral and color Doppler displays can present motion and flow information incorrectly. TOP: Spectral Doppler

7. The upper limit to the pulsed wave Doppler shift that can be properly detected by pulsed instruments is called: a. aliasing. b. Nyquist limit. c. shadowing. d. speed error.

ANS: B

The upper limit to the pulsed wave Doppler shift that can be properly detected by pulsed instruments is called the Nyquist limit. Aliasing occurs when the pulsed wave Doppler shift frequency exceeds one-half of the pulse repetition frequency (PRF).

PTS: 1 REF: p. 129

OBJ: List ways in which spectral and color Doppler displays can present motion and flow information incorrectly. TOP: Spectral Doppler

8. Artifacts caused by sonographic technique include all of the following except: a. noise. b. banding. c. side lobes. d. breathing.

ANS: C

Side lobes are equipment artifacts caused by secondary (weaker) beams of sound traveling out from a single element in different directions of the primary (main) beam.

PTS: 1 REF: p. 123

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Propagation

9. The best example of a mirror-image artifact is seen with the: a. gallbladder and cystic duct. b. pancreas and duodenum. c. uterus and fallopian tube. d. diaphragm and liver.

ANS: D

Mirror imaging occurs if a structure has a curved surface. Structures that exist on one side of a strong reflector are present on the other side as well.

PTS: 1 REF: p. 121 | p. 123

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Mirror Image, Shadowing, Clutter, and Noise a. Decreasing the Doppler angle b. Decreasing the transducer frequency c. Increasing the depth of the sample volume d. Decreasing the pulse repetition frequency

10. Which one of the following will reduce or eliminate aliasing?

ANS: B

Methods of reducing or eliminating aliasing include increasing the pulse repetition frequency, larger Doppler angle, and decrease depth of the sample volume. Decreasing the transducer frequency is another method.

PTS: 1 REF: p. 130

OBJ: List ways in which spectral and color Doppler displays can present motion and flow information incorrectly. TOP: Spectral Doppler

11. Refraction can cause a reflector that is: a. missing. b. not real. c. misplaced. d. of improper brightness.

ANS: C

Refraction can cause a reflector to be positioned improperly (lateral) on a sonographic display.

PTS: 1 REF: p. 123

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Propagation a. Noise b. Speckle c. Speed error d. Range ambiguity

12. Which one of the following artifacts results from constructive and destructive interference of the returning echoes?

ANS: B

Speckle is the interference pattern resulting from constructive and destructive interference of echoes returning simultaneously from many scatterers within the propagating ultrasound pulse at any instant.

PTS: 1 REF: p. 121

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Propagation

13. Echoes resulting from grating lobes may be imaged if they fall within a(n) region. a. complex b. anechoic c. echogenic d. hypoechoic

ANS: B

If grating lobes encounter a strong reflector (e.g., air), their echoes may well be imaged, particularly if they fall within an anechoic region.

PTS: 1 REF: p. 123

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Propagation a. Cyst b. Air c. Bone d. Blood vessel

14. Which one of the following structures is most likely to demonstrate strong posterior shadowing?

ANS: C

Calcified plaque, bone, and stones are examples of structures that demonstrate strong posterior shadowing. Air demonstrates a “dirty” shadow posteriorly.

PTS: 1 REF: p. 127

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Attenuation a. zones b. intensity c. banding d. attenuation

15. Increased intensity in the focal region of the sound beam is called focal ___________________.

ANS: C

Increased intensity in the focal region of the sound beam is called focal banding or focal enhancement.

PTS: 1 REF: p. 128

OBJ: Describe how specific artifacts can be recognized. TOP: Attenuation

16. Shadowing is reduced by using: a. harmonics imaging. b. pixel interpolation. c. three-dimensional imaging. d. spatial compounding.

ANS: D

Shadowing is reduced with spatial compounding because several approaches to each anatomic site are used, allowing the beam to “get under” the attenuating structure.

PTS: 1 REF: p. 128

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Attenuation a. Noise b. Aliasing c. Mirror image d. Range ambiguity

17. Identify the artifact commonly seen with pulsed wave Doppler imaging.

ANS: B

Aliasing is the most common artifact encountered in pulsed wave Doppler ultrasound.

PTS: 1 REF: p. 129

OBJ: List ways in which spectral and color Doppler displays can present motion and flow information incorrectly. TOP: Spectral Doppler a. Shifting the baseline b. Decreasing the Doppler angle c. Increasing the transducer frequency d. Increasing the pulse repetition frequency

18. Which one of the following eliminates aliasing using the “cut and paste” technique?

ANS: A

Baseline shift is an electronic “cut and paste” technique that moves the misplaced aliasing peaks over their proper location.

PTS: 1 REF: p. 129

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Spectral Doppler a. Shifting the baseline and decreasing the pulse repetition frequency b. Decreasing the pulse repetition frequency and increasing the depth of the sample gate c. Shifting the baseline and increasing the pulse repetition frequency d. Increasing the pulse repetition frequency and increasing the depth of the sample gate

19. Which of the following solutions are common and convenient to aliasing?

ANS: C

Shifting the baseline and increasing the pulse repetition frequency are common and convenient solutions to aliasing.

PTS: 1 REF: p. 129

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Spectral Doppler

20. To decrease internally generated electronic noise in the Doppler signal, the sonographer should decrease the: a. Doppler gain. b. overall gain. c. imaging depth. d. transducer frequency.

ANS: A

Internally generated electronic noise appears if the Doppler gain is set too high.

PTS: 1 REF: p. 132

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Spectral Doppler

21. Reverberation artifact displays structures that are: a. not real. b. misplaced. c. improper in shape. d. improper in brightness.

ANS: A

Reverberation (multiple reflections) results in the display of additional reflectors that are not real.

PTS: 1 REF: p. 120

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Imaging artifacts a. Speckle b. Aliasing c. Mirror image d. Range ambiguity

22. Increasing the pulse repetition frequency increases the chances of displaying which one of the following artifacts?

ANS: D

Higher pulse repetition frequencies (PRF) permit higher Doppler shifts to be detected but also increase the chance of the range ambiguity artifact occurring.

PTS: 1 REF: p. 125 | p. 136

OBJ: Explain how artifacts can be handled to avoid the pitfalls and misdiagnosis that they can cause. TOP: Propagation a. Noise b. Aliasing c. Mirror image d. Range ambiguity

23. Cross-talk can produce which one of the following artifacts?

ANS: C

Cross-talk can produce a Doppler mirror-image artifact.

PTS: 1 REF: p. 132

OBJ: List ways in which spectral and color Doppler displays can present motion and flow information incorrectly.

TOP: Spectral Doppler a. brightness b. duplication c. shadowing d. enhancement

24. Refraction of the sound beam at a boundary may result in false sonographic ________________.

ANS: C

Refraction of the sound beam at a boundary may result in false sonographic shadowing (edge shadowing).

PTS: 1 REF: p. 123 | p. 125

OBJ: Describe how specific artifacts can be recognized. TOP: Propagation a. temporal b. lateral c. axial d. contrast

25. The width of the pulse determines ______________ resolution.

ANS: B

The width of the pulse determines lateral resolution.

PTS: 1 REF: p. 136

OBJ: List ways in which sonographic gray-scale images can present anatomic structures incorrectly. TOP: Table 7-2