Which tissue typically appears bright on ultrasound due to high reflectivity?

Which tissue typically appears bright on ultrasound due to high reflectivity?

• A. Bone
• B. Muscle
• C. Fat
• D. Air

Answer: (A)

Brightness on ultrasound comes from echogenicity—the amount of sound that a tissue reflects. Bone has a very large acoustic impedance difference compared with surrounding soft tissues because of its high density and mineral content. That big mismatch causes most of the ultrasound beam to be reflected at the bone surface, so the bone appears as a bright, hyperechoic line on the image. Behind the bone, the beam is largely blocked, leading to posterior shadowing. In comparison, muscle and fat reflect less sound and appear progressively darker, while air reflects strongly but tends to create artifacts and obscure what lies beyond. So bone's strong reflectivity makes it the tissue that typically looks brightest on ultrasound.

Brightness on ultrasound comes from echogenicity—the amount of sound that a tissue reflects. Bone has a very large acoustic impedance difference compared with surrounding soft tissues because of its high density and mineral content. That big mismatch causes most of the ultrasound beam to be reflected at the bone surface, so the bone appears as a bright, hyperechoic line on the image. Behind the bone, the beam is largely blocked, leading to posterior shadowing. In comparison, muscle and fat reflect less sound and appear progressively darker, while air reflects strongly but tends to create artifacts and obscure what lies beyond. So bone's strong reflectivity makes it the tissue that typically looks brightest on ultrasound.