Calcified plaque on ultrasound can cause which artifact?

• A. Color blooming
• B. Posterior acoustic enhancement
• C. Grating lobe
• D. Acoustic shadowing

Answer: (D)

Calcified plaque causes acoustic shadowing because dense calcium strongly attenuates the ultrasound beam. The plaque reflects and absorbs most of the energy, so little sound returns from tissues behind it. The result is a bright, echogenic plaque with a dark, distal shadow that obscures the lumen and distal vessel details. This is distinct from posterior acoustic enhancement (which occurs behind low-attenuation fluids and makes the area beyond brighter), grating lobe artifacts (ghost echoes from the transducer’s array), or color blooming (a Doppler signal spread artifact). The attenuation from calcification specifically produces shadowing, making it the correct artifact in this scenario.