Absorption of ultrasound in tissues

Abstract

The primary absorption of ultrasound in most soft tissues occurs at the macromolecular level. The attenuation observed when a tissue sample is interposed between a source and receiver may be affected by reflection, refraction, and phase distortion in the wave transmitted through the sample. However, when these effects are minimized, the differences between absorption and attenuation coefficients are small. Most soft tissues are characterized by small negative temperature coefficients up to physiological temperatures. At high intensities, nonlinear phenomena become important and can create losses in tissues which are mechanistically distinct from small amplitude absorption processes.