Welcome to Day 24, where we continue exploring ultrasound artifacts — this time focusing on four crucial ones that affect brightness, edge detection, and beam behavior. These artifacts are both diagnostically helpful and testable in the SPI exam.
Let’s dive into Shadowing, Enhancement, Edge Artifact, and Side Lobes.
🌑 1. Shadowing Artifact
Definition: A dark band (hypoechoic or anechoic) appearing distal to a highly attenuating structure.
Cause:
Strong absorbers or reflectors reduce the beam intensity beyond them.
Examples:
- Gallstones
- Bone
- Calcified plaque
SPI Tip:
Shadowing results from high attenuation — less sound reaches the tissue behind.
🌕 2. Posterior Enhancement (Through Transmission)
Definition: A bright (hyperechoic) area posterior to a structure that allows sound to pass through with minimal attenuation.
Cause:
Low-attenuation tissues let more ultrasound reach the deeper tissues.
Examples:
- Urinary bladder
- Simple cyst
- Gallbladder
SPI Tip:
Use enhancement to confirm cystic structures — a key diagnostic clue!
🔪 3. Edge Artifact (Refraction Shadow)
Definition: A shadow-like line extending from the edge of a curved structure.
Cause:
Refraction of the beam at the curved interface + beam divergence.
Examples:
- Gallbladder edges
- Fetal skull
- Renal cyst edges
SPI Tip:
Edge artifact appears lateral, not posterior — don’t confuse with true shadowing.
🔊 4. Side Lobes (or Grating Lobes)
Definition: Additional energy that travels off-axis from the main ultrasound beam and returns false echoes.
Cause:
Weak secondary sound beams reflecting off strong interfaces.
Examples:
- Artificial echoes within a cyst
- Multiple dots within anechoic regions
SPI Tip:
Side lobes and grating lobes create artificial internal echoes — especially in fluid-filled structures.
🧠 Artifact Quick Summary Table
| Artifact | Appearance | Cause | Clue Example |
| Shadowing | Dark posterior band | Strong attenuation | Gallstones |
| Enhancement | Bright posterior area | Low attenuation | Simple cyst |
| Edge Artifact | Lateral shadows | Refraction at curved edges | Gallbladder edge |
| Side Lobes | False internal echoes | Off-axis beam reflections | Artificial cyst echoes |
📘 SPI Exam Key Points
✅ Shadowing = high attenuation
✅ Enhancement = low attenuation
✅ Edge Artifact = lateral shadow due to refraction
✅ Side Lobes = false echoes from off-axis beams
📝 Flashcard
Q: What artifact can help confirm a cystic structure on ultrasound?
A: Posterior acoustic enhancement
🧭 Conclusion
Recognizing these artifacts will sharpen both your clinical interpretation and exam performance.
In upcoming posts, we’ll review Doppler artifacts and how to handle them.