What is ultrasound? What are the advantages and disadvantages?

Ultrasonic therapy is to apply ultrasonic waves to the human body, and act on a certain stage or the whole body through neurohumoral channels, resulting in mechanical, thermal and cavitation effects on human tissues, resulting in accelerated blood flow in local tissues, improved blood circulation, enhanced blood vessel wall peristalsis, enhanced cell membrane permeability, ion redistribution, vigorous metabolism, decreased hydrogen ion concentration in tissues, increased PH value, enhanced enzyme activity, enhanced tissue regeneration and repair ability, muscle relaxation, reduced muscle tension and relieved or relieved pain.