About Ultrasound

Development history

International aspect

Compared with optical methods such as infrared and ultraviolet, ultrasound started relatively late, with a history of fewer than 100 years. From the end of the 19th century to the beginning of the 20th century, after the piezoelectric effect and the inverse piezoelectric effect were discovered in physics, people solved the method of using electronic technology to generate ultrasonic waves, which quickly opened a historical chapter in the development and promotion of ultrasonic technology.

In 1922, the definition of ultrasound was proposed for the first time, and ultrasound became a brand-new concept. The first invention patent for ultrasound therapy appeared in Germany;

In 1939, literature reports on the clinical effects of ultrasound therapy were published.

In the late 1940s, ultrasound therapy emerged in Europe and the United States. It was not until the first international medical ultrasound academic conference held in 1949 that there was an exchange of papers on ultrasound therapy, which laid the foundation for the development of ultrasound therapy. In 1956, many papers were published at the Second International Conference on Ultrasound Medicine, and ultrasound therapy entered a stage of practical maturity.

Domestic aspect

In China, the field of ultrasound therapy started a little later. In the early 1950s, only a few hospitals carried out ultrasound therapy. In 1950, the 430 μm wavelength ultrasound therapy machine was first used in Beijing to treat various diseases, and it was gradually promoted in the 1950s. And have domestic equipment. Published reports in the literature began in 1957. In the 1970s, there were various types of domestic ultrasonic therapy instruments, and ultrasonic therapy was popularized in large hospitals across the country.

For more than 40 years, major hospitals across the country have accumulated a considerable amount of data and relatively rich clinical experience. Especially in the early 1980s, ultrasonic extracorporeal mechanical wave lithotripsy and ultrasonic surgery were major breakthroughs in the history of stone disease treatment. Now it has been promoted and applied internationally. High-intensity focused ultrasound for non-invasive surgery has made ultrasound therapy an important part of contemporary medical technology. In the 21st century, ultrasound-focused surgery (HIFU) has been hailed as the latest technology in the treatment of tumors in the 21st century.

Effect

Ultrasonic effect: When the ultrasonic wave propagates in the medium, due to the interaction between the ultrasonic wave and the medium, the medium changes, resulting in a series of mechanical and electromagnetic ultrasonic effects, including the following two effects:

1. Mechanical effects. The mechanical action of ultrasound can promote the emulsification of liquids, the liquefaction of gels, and the dispersion of solids. When a standing wave is formed in the ultrasonic fluid medium, the tiny particles suspended in the fluid condense at the node due to the action of mechanical force, forming a periodic accumulation in space. When ultrasonic waves propagate in piezoelectric materials and magnetostrictive materials, induced electric polarization and induced magnetization are caused by the mechanical action of ultrasonic waves.

2. Cavitation. A large number of small air bubbles can be generated when ultrasonic waves are applied to the liquid. One reason is that there is local tensile stress in the liquid to form a negative pressure, and the reduction of the pressure makes the gas originally dissolved in the liquid supersaturated, and escapes from the liquid as small bubbles. Another reason is that the strong tensile stress "rips" the liquid apart into a cavity called cavitation. Inside the cavity is a liquid-vapor or another gas dissolved in a liquid, possibly even a vacuum. The small bubbles formed by cavitation continue to grow or burst suddenly. When it bursts, the surrounding liquid suddenly rushes into the bubble to generate high pressure, and a shock wave is generated at the same time. The internal friction accompanied by cavitation can form an electric charge, and the phenomenon of luminescence is generated in the bubble due to the discharge. Most of the techniques for sonication in liquids are related to cavitation.