Today, ultrasonic diagnostic equipment plays an important role in image medical diagnosis

Just like X-ray, CT and MRI (magnetic resonance imaging). Ultrasonic examination has no invasive effect on the human body, and is not only used for abdominal and heart diagnosis, but also widely used in obstetrics, gynecology and pediatrics. Compared with other image diagnostic instruments, ultrasonic diagnostic instruments are small in size, cheap in price, easy to operate, and can observe the dynamics of the heart and fetus in real time. Therefore, ultrasonic medical devices are now being promoted rapidly.

When the ultrasonic wave enters the human body and propagates

It compresses the human tissue for a while and expands the human tissue for a while. When performing this kind of movement, it is necessary to generate heat and consume part of the ultrasonic energy.  As a result, as the ultrasound advances, the vibration intensity gradually decreases. It seems that the ultrasonic wave is absorbed and attenuated in the human body, so this attenuation is called absorption attenuation. Diagnosis of fatty liver as absorption decay in diagnostic applications.

When ultrasonic waves are perpendicularly incident on the boundaries of human tissues with different acoustic resistances, reflection and refraction will occur. The display method that uses the amplitude of the waveform to indicate the strength of the echo signal is called A-type display. The display mode in which the intensity of the echo signal is represented by the brightness of the image is called a B-type display. In order to obtain image display on the actual screen, both A-type display and B-type display must move (scan) the ultrasonic beam (bright spot on the screen). Instead, the ultrasound beam is fixed in one direction and only moves (scans) the screen or paper to display the image, which is called an M-mode display. The M-mode display is mainly used to observe the movements of heart valves and walls for diagnosis.

The ultrasonic beam scanning shown in Type B includes mechanical scanning and electronic scanning.

A group of multiple ultrasonic vibrators (about dozens of vibrators in each group) is electronically switched at a certain time, at a certain interval, and in sequence at a high speed to obtain a B-type display image. Because the ultrasonic beam is moved linearly, it is called linear scanning. Using this method, 10-30 ultrasound images can be obtained per second. Since B-mode images are obtained at such a high speed, peristalsis of the fetus and pulsation of blood vessels can be observed.