Final answer:
A ring-down artifact is echogenic and results from gas bubbles vibrating from interaction with the ultrasound beam, and it is often seen in sonographic images where gas is present.
Step-by-step explanation:
The type of artifact that appears echogenic and stems from gas bubbles vibrating due to the interaction with the ultrasound beam is called a ring-down artifact. This artifact is characteristic of the presence of gas within the body, such as in the lungs or intestines, which can cause reverberation that produces a continuous reflective echo pattern on the ultrasound image. Ultrasound imaging utilizes a speaker-microphone setup to send brief bleeps of sound into the body and listens for the returning echoes, which are used to construct an image that reveals the shape and density of internal structures.