Why do mirror image artifacts occur and when are they common?

• A. Strong reflectors (like the diaphragm) create a secondary reflection that produces a copy on the other side.
• B. They reflect energy forward
• C. They cause posterior enhancement
• D. They produce mirror image artifact.

Answer: (A)

Mirror image artifacts happen when a very strong, smooth reflector acts like a mirror for the ultrasound beams. The sound pulse travels to a deep structure, hits a strong interface (like the diaphragm), then bounces back toward the transducer, possibly reflecting again off that same interface before returning. The machine interprets the round-trip travel time as if the echo came straight back from a deeper location, so the structure behind the reflector is displayed as a duplicate image on the opposite side of the reflector. That creates a ghost copy that looks like a mirror image.

These artifacts are common when imaging near large, smooth reflectors such as the diaphragm, where the liver or other structures lie behind it. The effect can appear anywhere a strong boundary exists and the beam path allows the two-step reflection to occur. You can often reduce it by changing the probe angle or position to avoid having the strong reflector align with the retroreflective path.