What are the main effects of biological tissues on incident ultrasound?

The biological effects of ultrasound have complex effects and mechanisms at different biological levels. Ultrasound has obvious effects on biological macromolecules, especially DNA, mainly degradation, leading to DNA breakage, and its mechanism may be cavitation. High intensity ultrasound can lead to cell membrane rupture, decrease of membrane surface charge or change of membrane permeability. The absorption of ultrasound by biological tissues is relatively high, and the heat conduction is low, which is easy to cause the temperature to rise, thus causing blood vessels to dilate or contract and changing blood pressure. High intensity focused ultrasound irradiation can destroy tumor cells or inhibit their growth, while appropriate intensity stimulation can promote tissue growth. The energy conversion and relaxation of ultrasound in biological media are closely related to frequency and accompanied by thermal effect. The radiation pressure and sound pressure of ultrasound lead to disturbance and friction effect, which affects the structure and function of living things. The biochemical effects induced by ultrasound can be considered as secondary effects. Ultrasonic biological effect caused by ultrasonic mechanical vibration is the basis of ultrasonic diagnosis and treatment.