Ultrasound

Ultrasound is used in many areas of medicine, including diagnostic imaging, therapy, lithotripsy, and surgery. The chapter gives a general description of ultrasound, its propagation, bioeffects, and measurement techniques. Potential biohazards of ultrasound are tissue heating, cavitation, acoustic radiation forces, and mechanical strain due to particle displacement. Any bioeffects produced by ultrasound in diagnostic applications have little consequence for the individual, as illustrated by its routine use in diagnostic foetal scanning, but surgical techniques destroy tissue on a macroscopic scale. There are separate sections which consider exposure, standards and give practical guidance measures for each of the four main areas of medical application. All applications of ultrasound in medicine have an impressive safety record, and the 3 W cm-2 limit for therapeutic ultrasound is the only safety criterion that has been formally adopted into current international standards.