Ultrasound does not always show reality.
Sometimes it shows physics.
Artifacts are not errors —
they are predictable consequences of sound interaction with tissue.
Understanding them prevents misdiagnosis.
1️⃣ Posterior Acoustic Enhancement
What Happens?
When ultrasound passes through fluid (low attenuation),
more sound energy reaches deeper tissues.
Result:
The area behind the fluid appears brighter.
Clinical Example
- Ovarian cyst
- Allantoic cyst
- Simple breast cyst
Enhancement supports cystic nature.
If the posterior wall looks brighter than adjacent tissue,
think fluid.
2️⃣ Acoustic Shadowing
What Happens?
Strong reflectors or highly attenuating structures block sound transmission.
Result:
Dark shadow posterior to the structure.
Clinical Example
- Calcifications
- Gallstones
- Fibrotic scars
- Umbilical cord calcification (rare)
Clean shadow → strong reflector
Dirty shadow → gas
3️⃣ Reverberation Artifact
What Happens?
Sound bounces repeatedly between two strong reflectors.
Result:
Multiple equally spaced echoes.
Clinical Example
- Needle artifacts
- Gas in bowel
- Near-field artifacts
If echoes appear evenly spaced,
it is likely reverberation — not multiple structures.
4️⃣ Mirror Image Artifact
What Happens?
Sound reflects off a strong interface (e.g., diaphragm)
and creates a duplicated structure.
Clinical Example
- Liver lesion appearing above diaphragm
- Pelvic structures duplicated
Always check if the structure moves symmetrically.
Obstetric Practical Notes
In fetal ultrasound:
- Enhancement may exaggerate cystic lesions.
- Shadowing can hide subtle calcifications.
- Reverberation may mimic membranes.
- Mirror artifact can confuse fluid spaces.
Before labeling pathology, ask:
Is this tissue — or is this physics?
Key Summary Table
| Artifact | Appearance | Cause | Clinical Meaning |
| Enhancement | Bright posterior | Low attenuation | Suggests fluid |
| Shadowing | Dark posterior | High attenuation | Suggests calcification/solid |
| Reverberation | Repeated echoes | Multiple reflections | Not real structures |
| Mirror | Duplicated image | Strong interface refled | False duplication |
Closing Line
Experience teaches anatomy.
Understanding artifacts teaches judgment.
