The frequency commonly used in physical therapy is generally 800 to 1000 kHz. The use of ultrasound therapy has become more and more extensive, and it has far surpassed the original general therapies of physiotherapy departments, such as ultrasound treatment of cancer, urologic lithotripsy and the use of stomatology, so the concept of ultrasound therapy has a broad sense (including various special ultrasound therapy ) and narrow sense (refers to the noninvasive dose therapy commonly used in the physiotherapy department) two types. At the same time, with the advancement of modern science and technology, ultrasound is not only used for treatment, but has also been widely used in diagnosis, basic and experimental medicine, and therefore has been called "ultrasonic machine"