During production of a sonogram you image the following structures. Which is the MOST attenuating?

• A. Blood
• B. Bile
• C. Soft tissue
• D. Calcification

Answer: (D)

Attenuation in ultrasound depends on how much energy the sound wave loses as it travels through tissue—through absorption, reflection, and scattering. Very dense, highly reflective materials absorb and scatter more sound, causing greater attenuation and often a strong posterior shadow. Calcifications fit that description because they are dense calcium deposits with a large acoustic impedance mismatch to surrounding tissue, so they markedly reduce the transmitted beam. Fluids like blood and bile are relatively low in attenuation since they’re fluid and don't scatter much, and soft tissue, while it does attenuate more than fluids, still doesn't reach the high attenuation seen with calcifications. So calcification is the most attenuating among the options.