Which has the greatest amount of attenuation?

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

Answer: (A)

Attenuation is how much the ultrasound energy is reduced as it travels through tissue, mainly from absorption and scattering. Dense, mineralized structures absorb and scatter sound more, so they reduce the beam more than softer tissues. Bone has a very high attenuation coefficient because of its high density and mineral content, causing substantial energy loss and shadowing behind it. In contrast, water attenuates very little, fat is low to moderate, and muscle is higher than fat but far less than bone. So bone exhibits the greatest attenuation among the options.