Ultrasonic Exposure Thresholds for Changes in Cells and Tissues

Abstract

Biological change consequent on ultrasonic exposure may arise through three distinct modes: thermal, cavitational (including stable bubble), and “other.” The thermal mechanism is quite well defined and predictable. Wide divergencies occur between different authors on values of cavitation thresholds, but these may be due, in part, to differences in criteria used. Our results are reported for dependence of “stable cavitation” on intensity, frequency, pulsing parameters, ambient pressure, and nature of the medium (liquid, gel, or organized tissue). Evidence is reviewed for the existence of, and relevant thresholds for, other mechanisms that are effective in living cells and tissues irradiated by ultrasonic beams.