What process describes conversion of sound energy into heat within tissue?

• A. Absorption
• B. Reflection
• C. Scattering
• D. Refraction

Answer: (A)

Absorption explains how sound energy is converted to heat inside tissue. As the ultrasound wave travels, part of its energy is dissipated by the tissue’s molecular interactions—viscous damping and relaxation processes—turning acoustic energy into a small amount of heat. This is the component that contributes to tissue heating and to the overall attenuation of the wave. In contrast, reflection sends energy back toward the transducer, refraction bends the wave at interfaces, and scattering redirects energy in multiple directions; none of these primarily create heat. So, absorption is the mechanism responsible for converting sound energy into heat within tissue.