Previously, the ring down artifact was thought to be a type of comet tail artifact, since both have bright “echogenic” lines arising from a specific location. However, the ring down artifact has a distinct feature compared to the comet tail artifact in that the echos do NOT dissipate as the depth of the image is increased. These echogenic vertical lines will go all the way to the bottom of the screen, regardless of depth. This has become known as the “ring down artifact” and is most commonly seen as “B-lines” in lung ultrasound, signifying interstitial edema.
The theory for the ring down artifact is that when fluid is trapped in a tetrahedron of air bubbles, the ultrasound waves reflect infinitely and result in an infinitely long vertical echogenic line.