What artifact is described as shadowing at the lateral edges of the curved structure?

What artifact is described as shadowing at the lateral edges of the curved structure?

• A. Grating lobes
• B. Comet tail
• C. Acoustic speckle
• D. Refraction

Answer: (D)

Shadowing along the edges of a curved structure comes from refraction. When ultrasound waves meet a curved boundary, the waves bend as they pass into a medium with a different speed of sound. At the lateral edges, this bending is strongest and the rays are redirected away from the imaging plane, causing the edge tissue to be under-sampled and producing a dark shadow along those sides. This directional bending and misregistration is the hallmark of refraction artifact. Other artifacts don’t specifically explain edge shadowing: grating lobes yield extra off-axis echoes, comet tail appears as a tail behind a strong reflector, and acoustic speckle is a grainy texture from interference rather than edge shadowing from beam bending.

Shadowing along the edges of a curved structure comes from refraction. When ultrasound waves meet a curved boundary, the waves bend as they pass into a medium with a different speed of sound. At the lateral edges, this bending is strongest and the rays are redirected away from the imaging plane, causing the edge tissue to be under-sampled and producing a dark shadow along those sides. This directional bending and misregistration is the hallmark of refraction artifact. Other artifacts don’t specifically explain edge shadowing: grating lobes yield extra off-axis echoes, comet tail appears as a tail behind a strong reflector, and acoustic speckle is a grainy texture from interference rather than edge shadowing from beam bending.