Ultrasound is a kind of elastic mechanical wave in material medium. It is a wave form. Therefore, it can be used to detect the physiological and pathological information of human body, that is, diagnostic ultrasound. At the same time, it is also a form of energy. When a certain dose of ultrasound propagates in organisms, through their interaction, it can cause changes in the function and structure of organisms, that is, ultrasonic biological effect.

The effects of ultrasound on cells mainly include thermal effect, cavitation effect and mechanical effect. The thermal effect is that when ultrasound propagates in the medium, the friction hinders the molecular vibration caused by ultrasound and converts part of the energy into local high heat (42-43 ℃). Because the critical lethal temperature of normal tissue is 45.7 ℃, and the sensitivity of swollen Liu tissue is higher than that of normal tissue, the metabolism of swollen Liu cells is impaired at this temperature, and the synthesis of DNA, RNA and protein is affected, so as to kill cancer cells without affecting normal tissue.

Cavitation effect is that under ultrasonic irradiation, vacuoles are formed in organisms. With the vibration of vacuoles and their violent explosion, mechanical shear pressure and turbulence are generated, which makes swelling Liu bleeding, tissue disintegration and necrosis.

In addition, when the cavitation bubble breaks, it produces instantaneous high temperature (about 5000 ℃) and high pressure (up to 500 ℃) × 104pa), which can be produced by thermal dissociation of water vapor OH radical and H atom, by OH radical and The redox reaction caused by H atom can lead to polymer degradation, enzyme inactivation, lipid peroxidation and cell killing.