Artifacts in Ultrasound

Artifacts: 

  • Doppler Ghosting
  • Range Ambiguity
  • Multi-Path
  • Reverberation
  • Comet Tail
  • Propagation Speed Error
  • Shadowing
  • Enhancement
  • Rounding (Edge Shadow)
  • Mirror (Spectral)


Know how to fix artifacts. There will be 4-5 Questions on the exam.

Artifacts (imaging errors)

Many artifacts are the result of the sound beam being larger than the reflector.

Side lobes make a sound beam wider which results in an artifact and diminishing lateral resolution.

  • A pulse that is long will obscure anatomy and diminish axial resolution.
  • A thick pulse will diminish your elevational resolution (slice thickness).

Artifacts are displayed echoes that are not real or echoes that are real that are not displayed. There are many types. Reflectors that are missing, have improper brightness, size, shape and/or position.

They are created because the machine assumes certain things to be true and if there is any deviance an acoustic artifact is created.

Some artifacts are created through a flaw in the machine or possibly a malfunction.

An anatomic pitfall is something that causes an error in interpretation by the operator.

Some artifacts are solely because of operator error.

  • Doppler Ghosting. 

Doppler  systems convert frequency shifts into a spectrum of colors Frequency shifts arise from movement. An ultrasound machine measures the movement of Red Blood Cells. Since the blood flows through a vessel that has walls that pulsate, this pulsation causes it’s own Doppler shift so the machine creates a color map that “bleeds” into the surrounding tissue (ghosting).

A high pass filter (wall filter or low velocity reject) will help eliminate the movement of anatomy and not blood cells. It does this by elimination low level Doppler shifts that sit around the baseline.

  • Range ambiguity.

Is created when an echo from a deep reflector arrives after another pulse is already created. When the Pulse Repetition Frequency (PRF) is too high the machine assumes that the echo came from the second pulse and displays the echo to shallow on the image.

  • Multi-path Artifact. 

This results in a reflector positioned incorrectly on the display because the path that the echo returned on is longer that the path the initial beam took to get to the reflector. This causes more of a poor image than a specific misplaced echo.

  • Reverb artifact (Reverberations)

This is usually created from sound bouncing between two strong reflectors. What you notice is that you will have multiple, equally spaced echoes in a line displaying deep to the reflectors that lie parallel to the sound beam.

  • Comet tail or ring down

This artifact appears as a solid line deep to the originating echo. Similar to reverb artifact with the space between the artificial echos merged together.

  • Propagation Speed Errors

An ultrasound machine assumes that the medium is soft tissue. If the sound beam travels through material that has a different propagation speed then there will be a time/distance error.

Mainly you will see reflections that are displayed at incorrect depths.

If the Propagation speed is greater than 1540 m/s (soft tissue) then the resulting echo will be placed more superficial than it actually is.

If the Propagation speed is less than 1540 m/s (soft tissue) then the resulting echo will be placed deep to where it actually is.

  • Shadowing 

Shadowing occurs when a structure has a high level of attenuation. Structures deep to it will not be seen because there will not be a sufficient amount of returning echoes due to the  highly attenuating structure.

  • Enhancement 

Enhancement is the opposite of shadowing. It occurs when a structure has a lower than normal level of attenuation. Structures deep to it will appear hyperechoic because there will be a greater than normal amount of returning echoes due to the decreased attenuation of the structure.

  • Rounding artifact (edge shadow, refraction shadow)

On a round structure there is an discernible amount of refraction. Since this occurs the sound beam does not make the return trip and is not recorded. So a shadow occurs at the edges of the round structure.

  • Mirror image 

We see this when you have a strong reflector in the path of the beam. A great example is the diaphragm. You can see a really nice reflection of the hepatic vessels superior to the diaphragm.

Sound is reflected at an oblique angle and then returns to the machine. The machine assumes that the path was straight.


Ultrasound artifacts review

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Your answers are highlighted below.
Question 1
If the propagation speed of a medium is greater than soft tissue, where will the resulting echo be placed?
A
More superficial than it actually is.
B
Lateral to the true location.
C
Deeper than it actually is.
D
There is no change.
Question 2
Rounding artifact (edge shadow) is mainly due to what?
A
Refraction
B
Shadowing
C
Reflection
D
Absorption
Question 3
Comet tail artifact has what characteristics?
A
Echogenic line superficial to reflector.
B
Echogenic line deep to reflector.
C
Twinkle seen on color doppler deep to reflector.
D
Shadow deep to reflector.
Question 4
Shadowing occurs when a structure has a high level of what?
A
Absorption
B
Attenuation
C
Reflection
D
Refraction
Question 4 Explanation: 
Explanation: Attenuation includes all of the above. Shadowing is not due to absorption or reflection alone, but a combination of them.
Question 5
Rounding artifact (edge shadow) is mainly due to what?
A
Absorption
B
Rounding artifact (edge shadow) is mainly due to what?
C
Reflection
D
Refraction
Question 6
Enhancement occurs when a structure has a low level of what?
A
Absorption
B
Attenuation
C
Refraction
D
Reflection
Question 6 Explanation: 
Attenuation includes all of the above. Enhancement is not due to lack of absorption or reflection alone, but a combination of them.
Question 7
Range ambiguity results from what assumption?
A
That an echo that passed through a solid structure with a lower propagation speed is placed at the correct depth.
B
That the second of two echoes returning is actually the first.
C
That the path that the echo takes to return is the same length as the initial path to the echo.
D
That an echo that passed through a cystic structure with a higher propagation speed is placed at the correct depth.
Question 8
Doppler Ghosting is the result of what?
A
The color gain being too high
B
The baseline incorrectly positioned.
C
The thickness of the beam
D
The doppler shift created by pulsating vessel walls.
Question 9
Comet tail artifact is similar to ring down artifact. What characteristic causes the traditional "comet tail"?
A
Closely spaced reverberations that merge together.
B
Gas trapped within the structure.
C
Cavitation within the originating echogenic reflector.
D
Increasing strength of the return echo reverberations.
Question 10
Mirror image artifact is created when there is what object in the image?
A
A scattering reflector
B
A large Diffuse reflector
C
A large Specular reflector
D
A medium reflector
Question 11
If the propagation speed of a medium is less than soft tissue, where will the resulting echo be placed?
A
There is no change.
B
Deeper than it actually is.
C
Lateral to the true location.
D
More superficial than it actually is.
Question 12
Reverb artifact is created when what happens?
A
A harmonic is created when sound bounces between two strong reflectors.
B
The sound wave hits a large specular reflector.
C
The echo is created perpendicular to the reflector.
D
The sound wave bounces between two strong reflectors.
Question 13
Shadowing occurs when a structure has a high level of what?
A
Reflection
B
Absorption
C
Attenuation
D
Refraction
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I am the founder and lead Instructor here at ExamRefresh.com. I strive to help those that are entering the field of Ultrasound to be the best that they can be. Ultrasound is my passion.

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