Which tissue is described as having very high attenuation due to strong absorption of ultrasound energy?

• A. Water
• B. Soft tissue
• C. Air
• D. Bone

Answer: (D)

Attenuation in ultrasound means the loss of sound energy as it travels through tissue, primarily from absorption and scattering. Bone stands out because it is dense and mineral-rich, which causes a large portion of the ultrasound energy to be absorbed and scattered within it. This makes bone have a much higher attenuation coefficient than water, soft tissue, or air, so waves are rapidly weakened as they pass into bone and much energy doesn’t travel far beyond it. That strong absorption also leads to a bright interface at the bone surface and a pronounced shadow beyond. Water and soft tissue let more sound through with less loss, while air largely reflects energy at interfaces rather than transmitting it, so it isn’t characterized by high attenuation inside air itself. Hence, bone is the tissue described as having very high attenuation due to strong absorption.