Welcome to Day 23 of our journey toward SPI success!
Today we begin a two-part series on a crucial topic for both the SPI exam and real-world scanning — ultrasound artifacts. These “image errors” can mislead diagnoses or reveal hidden truths — if you know how to interpret them!
Let’s begin with four commonly tested artifacts: Reverberation, Comet Tail, Ring Down, and Mirror Image.
🔁 1. Reverberation Artifact
Definition: Multiple, equally spaced echoes caused by the bouncing of sound waves between two strong reflectors, like the transducer and a metallic object.
Appearance: A ladder-like, stacked pattern of echoes.
Example: Seen anterior to metal clips, needles, or the pleura.
SPI Tip:
Occurs when the sound beam gets trapped, repeatedly bouncing back and forth before returning to the transducer.
🌟 2. Comet Tail Artifact
Definition: A subtype of reverberation, caused by closely spaced reverberations within a small, highly reflective structure.
Appearance: A short, tapering, bright trail behind the object.
Example: Cholesterol crystals in the gallbladder, air bubbles, surgical clips.
SPI Tip:
Comet tail has a dense, tapering shape — no gaps between the lines unlike regular reverberation.
🔔 3. Ring Down Artifact
Definition: Caused by resonance of gas bubbles. It’s a continuous stream of sound emitted by the bubbles.
Appearance: A long, uninterrupted bright band extending posterior to air.
Example: Seen in gas-containing bowel, abscesses, or pneumobilia.
Difference from Comet Tail:
- Comet Tail = Discrete, tapering lines
- Ring Down = Solid, non-tapering band
🪞 4. Mirror Image Artifact
Definition: When sound reflects off a strong interface (like the diaphragm) and produces a duplicated image on the opposite side of the reflector.
Appearance: A false structure (copy) appears deeper than the real structure.
Example: Fetal parts duplicated below the diaphragm, or liver lesions mirrored across the diaphragm.
SPI Tip:
Always suspect mirror image when you see symmetrical duplicates opposite a strong reflector.
🧠 Quick Review Table
| Artifact | Cause | Key Appearance | Example |
| Reverberation | Repeated bouncing between reflectors | Ladder-like echoes | Anterior bladder wall |
| Comet Tail | Small metallic or crystalline reflectors | Bright tapering tail | GB cholesterol crystals |
| Ring Down | Resonating gas bubbles | Bright continuous band | Pneumobilia |
| Mirror Image | Strong reflector duplication | Symmetric copy across interface | Diaphragm-mirrored liver |
📘 SPI Exam Alert
✅ All four artifacts are frequently tested.
✅ Be able to identify each by appearance and cause.
✅ Know the difference between comet tail and ring down — very common SPI question!
📝 Flashcard
Q: Which artifact appears as a bright continuous band caused by gas bubbles?
A: Ring Down Artifact
🧭 Conclusion
Artifacts aren’t just exam material — they’re diagnostic clues. Learn to recognize them to avoid misdiagnosis and to interpret images wisely.
In the next post, we’ll cover Shadowing, Enhancement, Edge Artifact, and Side Lobes in Part 2 of Artifacts.