Refraction artifact occurs due to bending of sound waves at tissue interfaces causing echoes to appear displaced.

• A. Mirror
• B. Shadowing
• C. Refraction
• D. Grating lobes

Answer: (C)

Refraction artifacts happen when the ultrasound beam changes direction at a tissue boundary because the speeds of sound are different on either side. If the incidence is oblique, this speed change bends the beam (Snell’s law), so echoes return from a location that’s not along the straight-line path the system assumes. Because the image is built from those assumed straight paths, the reflector appears displaced laterally from its true position. This bending and misregistration is distinct from mirror artifacts (ghost images created by strong reflectors), shadowing (loss of signal behind highly attenuating structures), or grating lobes (off-axis beams causing faint copies).