Which artifact is caused by reverberation resulting in multiple echoes?

• A. Comet tail
• B. Ring-down
• C. Side lobe
• D. Reverberation

Answer: (D)

Reverberation is the phenomenon where the ultrasound pulse bounces back and forth between two strong reflectors, creating a train of echoes that are equally spaced along the beam. This repeated back-and-forth reflection produces multiple echoes, which is exactly the artifact described. Other options describe different effects—ring-down comes from resonance (often gas bubbles) and shows a rapid series of echoes in place; side lobe artifacts arise from off-axis energy; comet-tail is a tail of echoes behind a strong reflector. The defining feature here is the multiple, evenly spaced echoes caused by reverberation, so this term names the artifact.