Ultrasound is ultimately a form of pattern recognition. The better you understand what structures should look like, the easier it becomes to recognize when something is off. This is why Artifacts and understanding where they come from is so important. At first Artifacts seem completely random they usually are very bright or very dark echoes. Inside the body an artifact can make normal anatomy seem severely pathological. In some cases artifacts and double the anatomy and confuse the sonographer.
You could approach this topic and memorize the different artifacts and there markings to identify them one by one , like a Rorschach blot test. This approach could work but has a high chance that you’ll miss or forget something. Or we can discuss the causes of Artifacts and identify where they are more likely to show up . By doing this we can anticipated where we are more likely to see artifacts and get ahead of it. Once understood, artifacts become highly predictable and can be anticipated based on tissue interactions and machine assumptions.
What Are Artifacts ?
Artifacts are image features that do not accurately represent true anatomy. They occur because the ultrasound system is interpreting returning signals based on a set of assumptions. They can be bright areas ,dark areas, duplications of structures , odd distortions or erratic signals that create noise. We could think of an Artifacts as a mistake or an error , this would be a common interpretation. Instead lets think of them as not a mistake, but a system “limitation”
What Causes An Artifact?
In order to understand what causes an artifact in ultrasound. We first have to understand that Ultrasound and the mechanics that allow it to work have a set of rules that are assumes.
These “criteria” are as follows:
Sound travels in a straight line
Sound travels at a constant speed (~1540 m/s)
Echoes return directly to the probe
Each structure is encountered only once
Each echo represents a single reflection
In order for use to have perfect image all of the above criteria needs to be met. As you’ll learn many patients will have irregularity’s or inorganic structures in there body. If we know that a patient has a prosthetic , stent or some form of artifical material in their body we can already assume there will be artifact. In this instance Artifacts are used as a tool for identification
Clinical Example :
Patient has a metal screw in there ankle due to previous injury.
Take a look at this image , can you tell where the screw heads are ? Can you identify the artifact?
In this image, we can observe multiple artifacts including comet tail, edge shadowing, and acoustic shadowing. These are commonly seen with metallic hardware due to strong reflection and attenuation of the ultrasound beam.
Clinical Example 2 :
Patient presents with a large foreign object in their wrist and forearm. The object is identified on ultrasound and believed to be a wooden splinter.
Figure 2: Foreign object producing acoustic shadowing and edge enhancementartifacts
While ultrasound may not be the gold standard for identifying all foreign bodies, it is extremely useful in detecting them. In this case, artifacts such as edge shadowing and posterior shadowing help confirm that the structure does not belong in normal tissue.
Now that we’ve seen some scenarios of where wed see artifacts and how to utilize them to identify foreign bodies, lets dive into different type of artifacts and what causes them.
Artifacts are not random—they follow predictable patterns based on how sound interacts with tissue. Instead of memorizing each artifact individually, we can group them based on what is happening to the ultrasound beam.
There are a few things that can happen to the sound beam that can cause an artifact, here is a check list to keep in mind :
Is the sound being blocked?
Is it passing through easily?
Is it bouncing back and forth?
Is it being redirected?
Artifacts by Attenuation
What’s happening: the sound beam is losing energy as it travels
Attenuation refers to the loss of sound energy as the ultrasound beam travels through tissue. Attenuation is always occurring as the sound beam travels through the body. As energy is lost, the system has less information to work with this is where artifacts begin to appear.
Attenuation can give rise to :
Acoustic Shadowing (Shadow): A dark (hypoechoic/anechoic) band behind a structure that absorbs or reflects sound heavily. This is commonly seen near highly attenuating structures such as bone, calcifications, and metallic objects.
Acoustic shadowing around gallstones observed in the gallbladder. The calcification absorbs the sound beam as it passes through and nearby creating the shadowing artifact.Bone has a high attenuation coeff it absorbs a large portion of the saound beam. This is why bone appears hyperechoic. Acoustic shadowing happens after these hyperechoic areas.
Take away:
Bone and calcifications absorb a large amount of the ultrasound beam due to their high attenuation.
If you see a bright (hyperechoic) structure, expect to see shadowing behind it.
Posterior Acoustic Enhancement (Enhancement): A bright (hyperechoic) area behind a weak attenuator. This occurs when the ultrasound beam passes through a structure that does not significantly attenuate sound (such as fluid), because very little energy is lost, more sound reaches deeper tissues making the area behind the structure appear brighter. This is common around fluid filled areas such as cysts, the bladder or organs such as the liver or kidney under pathological criteria.
Posterior acoustic enhancement
In this image we have the Urinary bladder. The sound beam travels through the fluid inside the bladder. Fluid has a low attenuation coeff, as a result the sound beam meets the edges of the bladder with allot of energy creating hyperechoic areas.
Key Take Away: When sound passes through a fluid-filled structure, expect increased brightness behind it due to minimal energy loss.
How Do We Compensate for Attenuation?
As the sound beam travels deeper, attenuation increases—causing deeper structures to appear darker.
Time Gain Compensation (TGC) allows us to adjust gain at different depths, restoring a more uniform image.
Artifacts by Reflection
Reflection based artifacts occur when sound waves bounce off structures unexpectedly, defying the assumption that sound travels in a straight line back to the probe.
Reflection gives rise to:
Reverberation :
Parallel horizontal bands occur through out the ultrasound image. They occur when sound waves bounce back and forth between two strong, parallel reflectors .Can be caused by air pockets, bowel case or skin anomalies.
There are 3 types of Reverberation artifacts
A-line
Comet Tail
Ring down
A-line
A-lines are repeating horizontal lines caused by sound bouncing back and forth between the pleura and the probe. This pattern tells you you’re looking at air-filled lung, because air strongly reflects ultrasound, very little sound penetrates deeper tissue. This leads to repeated echoes that appear as evenly spaced horizontal lines. The space between the A-lines is equidistant to the tissue depth.
Comet Tail
Comet tail artifact appears as dense tapering trail of bright echoes. The sound beam is trapped between small high reflective structures in the body. This is more common when there are metal structure , cholestrol , or gas bubbles.
When it comes to comet tail , picture the sound beam bouncing between two walls what happens? The sound beam will bounce off of one wall and hit the other and propagate downward.
Ring Down Artifact
Appears as vertifcal lines that are solid and hyperechoic. The lines are parrallel to each other and extend to deeper strong reflectors. Ring down is more of a resonace artifact. Its a more complex reverberation artifact, Ring down is common in fluid or gas filled areas. Fluid and gas filled spaces trap the echoes and they vibrate through the fluid.
Take Away from Reflection artifact :
A- line artifact is common around the pleural space and the lungs and can be identified by wide parallel lines
Comet tail artifact is common around metallic structures , gas bubbles, and strong reflectors such as the diaphragm , bone , gas bubbles and organ spaces. It is identified by short parallel lines that taper down vertically, The sound beam is trapped by strong reflectors and bounces back and forth moving down.
Ring Down artifact is common around gas and fluid filled spaces. The sound beam is trapped in these spaces and echoes of off of the media creating continuous vertical echogenic band
With Reflection the sound beam is trapped and echoes off of nearby structure and media that contain it
How Do We Compensate for Reflection Artifacts?
Reflection artifacts can’t always be completely removed, but we can reduce their impact by adjusting how the sound beam interacts with the body.
Change your acoustic window Reposition the probe to avoid strong reflectors. Even a slight angle change can prevent the beam from bouncing back and forth between structures.
Use Tissue Harmonics Harmonic imaging helps reduce reverberation artifacts by filtering out weaker returning echoes, improving image clarity.
Adjust frequency (when appropriate) Higher frequencies improve resolution and can make artifacts easier to recognize, especially in superficial imaging—but they won’t eliminate reflection artifacts.
Optimize overall gain (not just TGCs) While TGCs primarily compensate for attenuation, adjusting gain settings can help reduce the visual intensity of reflection artifacts and make the image easier to interpret.
The goal isn’t always to eliminate reflection artifacts but to recognize them and prevent them from being misinterpreted as real anatomy.
Artifacts by Refractions
What’s happens? The sound beam is being redirected as it travels through different tissue media.
Did you ever put a pencil in a glass of water? Notice how the image above and below the waterline are not linear? This is the basis for refraction.
Refraction occurs when sound waves pass between two tissues at an angle and with different propagation speeds.
Instead of continuing in a straight path, the beam changes direction.
This defies the assumption that the sound beam returns in a linear path back to the probe. When this assumption is broken, the system places structures in the wrong location.
Types of Refraction Artifact:
Edge Shadowing
Duplication artifact
Edge Shadowing:
This occurs around curved edges of structures in the body. Edge Shadowing is a shadow like artifact that occurs at the edges of curved structures due to refraction of the sound beam.
Why it happens:
Beam hits a curved surface (like a cyst or vessel)
Gets bent outward
Less sound continues straight → shadow forms
In this image we can she edge shadowing at the curved edges of this rounded cyst like structure .
Takeaway:
If you see shadowing at the edges of a curved structure, think refraction not attenuation.
Duplication Artifact
A structure appears to be doubled due to refracting sound, the beam is bent and returns along a different path other than the one it traveled through.
The beam is refracted as it passes through a structure (like fluid or muscle), then reflects off a deeper object and returns to the probe.
The system assumes the echo came back in a straight line, so it places the structure in the wrong location—creating a duplicate image.
In this photo we observe an anomaly of what appears to be 2 Aortas. In this area the sound beam is reflected of of the rectus abdominis muscle and the peritoneal fat pad. The illusion here is that the patient has two Aortas. Even on doppler in transverse we get two of the same doppler signals as observed below. PW on the Duplicate artifact give’s us identical wave forms.
In this case if we turn our probe 90 degree into the sagittal plane the echoes causing the double Aorta will diminish.
Takeaway:
If anatomy looks duplicated across a boundary , check with PW on both structures. If the wave forms are identical than we can assume there’s a duplication artifact.
How to Recognize Refraction Artifacts:
Does the structure appear shifted or duplicated?
Is the artifact occurring near a curved boundary?
Does it not follow normal anatomical alignment?
If yes, think refraction
Final Takeaways
Attenuation → energy loss during propogation→ shadows & enhancement
Reflection → bouncing between structures → reverberation, comet tail, A-lines
Refraction artifacts occur because the sound beam is being bent as it travels between tissues. Unlike reflection, the problem isn’t the the sound beam, it’s the path the beam takes.
Because of this, compensation is less about machine settings and more about probe positioning and beam alignment.
Key Take Away:
If the beam is bending, your goal is to change the angle so it doesn’t bend in the first place.
Reposition your probe (find a better window) Move around the structure instead of scanning through it. Especially useful around curved structures like vessels or cysts.
Reposition your probe (find a better window) Move around the structure instead of scanning through it. Especially useful around curved structures like vessels or cysts.
Scan from multiple planes If something appears duplicated or misplaced:
Check with PW and note if wave forms are exact copies
Check it in another plane
A true structure will stay consistent, a refraction artifact will shift or disappear
Unlike attenuation or reflection artifacts, refraction is not easily corrected with machine settings.
Takeaway
If anatomy looks shifted or duplicated → think refraction
If changing your angle makes it disappear → confirms it
The solution is probe movement, not knob turning
How Do We Differentiate Between Artifacts
Think about what the sound beam is doing:
Is the beam being blocked? → attenuation
Attenuation artifacts occur when the sound beam is blocked from propogating
Is it bouncing between 2 refelctors? → reflection
Reflection artifacts have horizontal lines that are parallel and flow downward
Is it being redirected? → refraction
Is there a strong reflector or curved edge to derail the sounds beams path?
Final Thoughts: Artifacts Aren’t Random
At first, artifacts feel chaotic and like an impassable hurdle.
But once we realize that they’re not random. We can look for the patterns and realize artifacts have they’re own rules.
The sound beam is always doing one of a few things:
losing energy
bouncing
or changing direction
Once you understand that, you stop guessing m, and you can start predicting. Look at the structures in your acoustic window. What structure have high attenuation coefficients? which ones are strong reflectors? which ones are inorganic?
And that’s when ultrasound really starts to click. When you can answer these things just by looking at them on ultrasound and corelate them to their associated anomalies.
What’s Next?
Now that you understand how artifacts form, we’ll start breaking them down individually:
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