Thermal and other non-cavitational mechanisms

Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. When ultrasound affects biological materials, this can be viewed as a bioeffect, a therapy study and/or a risk. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for understanding the range between risk assessment and image production. Relative to the former, that is, the mechanisms by which it is believed, or known, that ultrasound affects biological materials, ultrasonic bioeffects/therapies are generally separated into thermal and non-thermal mechanisms. The theme of this chapter deals with thermal and other non-cavitational mechanisms of ultrasound, that is, ultrasound-induced effects that are not believed to be bubble related.