Which term describes the cumulative loss of wave energy as it travels through tissue?

• A. Diffraction
• B. Absorption
• C. Attenuation
• D. Refraction

Answer: (C)

Attenuation describes the cumulative loss of wave energy as it travels through tissue. As the ultrasound beam moves deeper, energy is diminished because some of it is absorbed by the tissue and converted to heat, some is scattered in directions away from the main beam, and some may be reflected back. All of these processes together reduce the remaining energy, which is what attenuation captures. Diffraction involves bending around boundaries and doesn’t inherently quantify energy loss with depth. Absorption is a key mechanism that contributes to attenuation, but attenuation encompasses absorption plus scattering (and other minor losses) as the wave propagates. Refraction is the change in direction due to speed differences at interfaces, not a measure of energy loss.