Which gray scale artifact is caused by the oscillation of gas bubbles?

Ring-down artifact occurs when gas bubbles resonate or oscillate, creating continuous echoes distal to the structure that appear as a vertical, echogenic band extending posteriorly. This is distinct from reverberation, which produces multiple discrete reflections.

According to Zwiebel’s Introduction to Vascular Ultrasound:

“Ring-down artifact results from resonance of gas bubbles, producing a continuous, echogenic tail distal to the reflecting interface.”