Diagnostic color ultrasound is referred to as color ultrasound.
The principle of color ultrasound, in simple terms, is a high-definition black and white ultrasound coupled with color Doppler.
First of all, let's talk about what is ultrasound, we know that the human ear can hear the sound frequency of 20Hz ----20KHz, lower than 20Hz sound waves for infrasound, the human ear can not hear, higher than 20KHz sound waves for ultrasound, the human ear is also inaudible. Ultrasound is widely used in the medical field because he has many wonderful features:
1. Because of the high frequency and short wavelength of ultrasound, he can be like light along a straight line, making it possible to launch ultrasound to a certain direction has been determined.
2. Sound waves are longitudinal waves, which can propagate smoothly in human tissue.
3. Ultrasound waves are reflected when they meet the interface of different media.
These characteristics form the basis for the wide range of applications of ultrasound instruments in medicine today.
The basic principle of ultrasound imaging is that a set of ultrasound waves is emitted into the body and scanned in a certain direction. According to the monitoring of the delay time of its echo, the strength can be judged by the distance and nature of the organs. After the electronic circuitry and computer processing, the formation of the ultrasound images we have today.
The key component of the ultrasound is what we call the ultrasound probe (probe), which has a set of ultrasound transducers inside, made from a set of special crystals that have a piezoelectric effect. This piezoelectric crystal has the special property that when a voltage is applied to the crystal in a particular direction, the crystal deforms, and in turn, when the crystal deforms, a voltage is generated in the corresponding direction, realizing the conversion of electrical signals to ultrasound.
The following is a general schematic diagram of an ultrasound: A general ultrasound works as follows: when the probe is excited by an excitation pulse, it emits an ultrasound wave, and the probe is controlled by a focusing delay circuit, which realizes the acoustic focusing of the wave. Then after a period of time delay and then by the probe to receive the echo signal reflected back, the echo signal received back by the probe after filtering, logarithmic amplification and other signal processing. Then by the DSC circuit for digital conversion to form a digital signal, further image processing under the control of the CPU, and then with the chart formation circuit and measurement circuit together with the synthesis of video signals sent to the monitor to form a familiar ultrasound images, also known as two-dimensional black and white ultrasound images.
We talked about black and white ultrasound above, and then let's talk about color ultrasound, that is, "color ultrasound".
In fact, color ultrasound is not the real color of the human body tissue, but in the black-and-white ultrasound image on the basis of the Doppler effect principle based on the pseudo-color and the formation of. So what is the Doppler effect, when we stand in the train station platform to listen to a distant train whistle will be far away from us than the train whistle sound higher pitch, that is to say, for a stationary observer, towards the observer of the sound wave frequency of the object will be raised, the opposite frequency will be reduced, this is the famous Doppler effect. Modern medical ultrasound is the use of this effect, when the ultrasound wave encounters the flow away from the probe liquid echo frequency will be reduced, the flow of liquid to the probe will make the probe to receive the echo signal frequency increase. The use of computer pseudo-color technology to describe, so that we can determine the direction of the flow of liquid in the ultrasound image and the size and nature of the flow rate, and will be superimposed on the two-dimensional black and white ultrasound image, the formation of the color ultrasound images we see today.
Diagnostic ultrasound frequency shift, or D ultrasound, which applies the principle of the Doppler effect, when there is relative motion between the source and receiver (i.e., probe and reflector), the frequency of the echo is changed, and this frequency change is called frequency shift, D ultrasound, including pulsed Doppler, continuous Doppler, and color Doppler blood flow images.
Color Doppler ultrasound generally uses autocorrelation for Doppler signal processing, and the blood flow signals obtained by autocorrelation are color-coded and then superimposed on a two-dimensional image in real time to form a color Doppler ultrasound blood flow image. As a result, color Doppler ultrasound (i.e., color ultrasound) not only has the advantages of two-dimensional ultrasound structural images, but also provides a wealth of information on hemodynamics, and its practical application has been widely valued and welcomed, and it is known as "non-traumatic angiography" in clinical practice. Its main advantages are: ① It can quickly and intuitively display the two-dimensional distribution of blood flow. ②It can show the running direction of blood flow. ③It is good for identifying arteries and veins. ④It is good for recognizing vascular and non-vascular lesions. ⑤Facilitates the understanding of the nature of blood flow. ⑥ It can facilitate the understanding of the temporal phase and velocity of blood flow. ⑦ It can reliably detect shunts and refluxes. (8) It can quantitatively analyze the origin, width, length, and area of blood flow bundles.
But the color ultrasound using the relevant technology is pulsed wave, the speed of the detection of the object is too high, the color of the color flow color error will occur, in the quantitative analysis of obviously inferior to the spectral Doppler, nowadays color Doppler ultrasound instrument have the function of the spectral Doppler, that is, for the color 鈹 bifunctional ultrasound.
Color Doppler flow mapping (CDF), also known as color Doppler ultrasound imaging (CDI), obtains the same source of echo information and spectral Doppler, the distribution and direction of the blood flow is displayed in two dimensions, and different speeds are distinguished by different colors. Dual-energy Doppler ultrasound systems, that is, B-mode ultrasound images show the location of blood vessels. Doppler measures blood flow, and this combination of B-mode and Doppler systems allows for more precise localization of any given vessel.
1. Direction of blood flow In the spectral Doppler display, the direction of blood flow is distinguished by the zero baseline. Above the zero baseline indicates flow toward the probe, and below the zero baseline indicates flow away from the probe. In CDI, the direction of blood flow is color-coded, with red or yellow chromatograms indicating blood flow toward the probe (hot) and blue or blue-green chromatograms indicating blood flow away from the probe (cold).
2. Vascular distribution CDI shows blood flow within the lumen of a blood vessel and is therefore a flow channel type of display, which does not show the vessel wall or epithelium.
3. Identification of the types of blood vessels in cancerous nodules The blood vessels of hepatocellular carcinoma nodules can be categorized with CDI. Distinguish them as perinodal winding vessels, curved vessels to the inner edge of the nodule. The inflow vessels of the nodule, the internal vessels of the nodule and the outflow vessels of the nodule.