The principle of color Doppler ultrasound is simply high-definition black-and-white B-ultrasound plus color Doppler.
First of all, let's talk about what ultrasound is. As we all know, the frequency of sound that the human ear can hear is 20Hz-20KHz, and the sound waves below 20Hz are infrasound waves, which the human ear cannot hear, while the sound waves above 20KHz are ultrasonic waves, which the human ear cannot hear. Ultrasound is widely used in the medical field because it has many wonderful characteristics:
1. Ultrasonic waves can travel in a straight line like light because of their high frequency and short wavelength, which enables us to emit ultrasonic waves in a certain direction.
2. Sound waves are longitudinal waves and can spread smoothly in human tissues.
3. Ultrasonic waves will generate reflected waves when they meet different media interfaces.
These characteristics form the basis for the wide application of ultrasonic instruments in today's medical field.
The basic principle of B-ultrasound imaging is to send a group of ultrasonic waves to the human body and scan them in a certain direction. According to the delay time of monitoring its echo, we can judge the distance and nature of the organ by its strength. After processing by electronic circuits and computers, our B-ultrasound images today are formed.
The key component of B-ultrasound is what we call an ultrasonic probe, which contains a group of ultrasonic transducers made of a group of special crystals with piezoelectric effect. This kind of piezoelectric crystal has a special property, that is, when a voltage is applied in a specific direction of the crystal, the crystal will be deformed; conversely, when the crystal is deformed, it will generate a voltage in the corresponding direction, thus realizing the conversion between electrical signals and ultrasonic waves.
The following is the general schematic diagram of B-ultrasound: The general working process of B-ultrasound is as follows: when the probe gets the excitation pulse, it sends out ultrasonic waves (at the same time, the probe is controlled by the focusing delay circuit to realize acoustic focusing of sound waves. Then, after a period of delay, the probe receives the reflected echo signal, and the echo signal received by the probe is processed by filtering, logarithmic amplification and other signal processing. Then the digital signal is converted by DSC circuit, further image processing is carried out under the control of CPU, and then the video signal is synthesized by chart forming circuit and measuring circuit and sent to the display to form a familiar B-ultrasound image, also called two-dimensional black-and-white ultrasound image.