Can black and white color Doppler ultrasound be called color Doppler ultrasound?

Imagine such a scene: You went to the hospital for a medical examination and entered the color Doppler ultrasound room. The doctor took a mysterious instrument to play with your stomach for a long time, and then a diagnosis report was released. You hold the report form, but you clearly see that the image on the report form is printed with such an image:

Picture source: Literature 1

You watched the report, and asked the doctor: Why did I do "color ultrasound", but the results of the report were black and white?

The doctor glanced at the report form and said, "Yes, this is the color ultrasound report." Then he greeted the next patient.

You are full of suspicion, what kind of thing is the color Doppler ultrasound? Why is the "color" super? So after returning home, you tried to search the Internet "What is a color Doppler ultrasound" and got such an answer:

The color Doppler ultrasound is the color Doppler blood flow, the English abbreviation CDFI. The color Doppler ultrasound will process the Doppler information obtained, and through the color gray order, the direction and speed of the blood flow are identified by different colors and brightness, and the B ultrasonic image diagram is superimposed.

In the face of this string of understanding each word, but you do n’t even know what it means to be together, you do n’t seem to understand why the color ultrasound report is black and white.

In order to intuitively understand what color Doppler ultrasound is, why do color Doppler ultrasound, and the question of "why color Doppler ultrasound can be black and white", we also need to start with the history of medical ultrasound testing.

The earliest ultrasound form -A Super

When a person stood on the mountain peak and shouted towards the cliff on the opposite side, the sound waves reflected to the cliff on the opposite side and generated echoes. If you understand some physics, you can also calculate the distance between you and the cliff on the opposite side by measuring the time difference from shouting to hearing.

Image source: Askiitians

The principle of medical ultrasound examination is similar to it. When ultrasound first appeared in the field of medical examinations, doctors used not using flat -length ultrasound probes in our common today, but more like a pillar probe. This probe can produce a slender ultrasonic beam.

Picture source: Author shooting

When a thin ultrasonic beam spreads in the human body, if the boundary between different tissues, or tissues and organs is encountered, there is a small difference between the physical properties of different tissues in the human body, and some ultrasonic waves will reflect.

Image source: Made in the author

We use the probe to record these reflected echoes and display the echo in the form of time-amplitude to the oscilloscope.

Since the transmission speed of ultrasound in the human body is about 1540m/s, we can easily correspond to the distance between the echo time of the ultrasonic probe and the distance between the human tissue boundary to the probe.

This is the earliest form of ultrasound medical examination: amplitude type ultrasound, referred to as A super.

Image source: Made in the author

The role of A super -examination is equivalent to using an ultrasonic probe to open a virtual "window" in the human body without hurting the human body. In depth, the human tissue has changed, and some diagnosis is made in conjunction with existing medical knowledge.

Compared with other medical examination methods, ultrasound has a lot of advantages. It has no trauma, no radiation, and small and portable operation instruments.

However, the human tissue structure is very complicated. By looking at the waveform waveform, the tissue structure changes are speculated. The inspection method of this tube is obviously not intuitive and easy to make errors.

Go to B -ultrasound

In order to solve the above problems, scientists have made a series of improvements on the ultrasound on the basis of A super.

First of all, scientists have made clever improvements in ultrasound probes, so that the probe can be rotated by mechanically, or an electronic focusing method to launch an ultrasonic beam to multiple directions and targets, where the latter is called beam formation. In the most common ultrasound system, these beams will be combined into a virtual fan or rectangular plane as needed.

Picture source: Literature 2

Picture source: Literature 3

Secondly, scientists have improved the display of ultrasound echo based on radar -based experience. In the echo generated by a single beam, corresponding to the goal height of different depths, it is converted into a different depth of brightness information on the scanning line.

Image source: Made in the author

Combined with the beam formation technology mentioned above, many roots scanning lines in the human body can be obtained in the human body. Combining these scan lines together, what you get is an ultrasonic image that reflects a cross -section structure in a certain position in the human body.

Image source: Made in the author

Because in this ultrasonic inspection technology, the human structure information is displayed in different positions at different locations, so it is called Brightness type ultrasound, which is B -ultrasound.

The color ultrasound is finally here!

So what is color Doppler ultrasound? Simply put, scientists have found that with the advancement of technology, not only can the structural location information of the human body be extracted from ultrasonic waves, but also the Doppler sports information can be extracted.

Everyone should have seen such a scene in person or in the camera: a car pulls you with a sharp roar, and the sound becomes low after driving through your position. This is the Doppler effect discovered by Austrian physicist Doppler in 1842.

When a movement object comes towards the observer, the sound waves emitted will be compressed because of the relative movement between the two, and the frequency will increase and it sounds more acute. On the contrary, when an object goes away from the observer, the sound waves will be stretched, the frequency decreases, and it sounds lower. Picture source: Literature 4

Scientists recognize that on the basis of the B -ultrasound mentioned above, it can also be further determined whether the echo corresponding to a certain position is compressed, stretched or maintained to determine whether this area exists in the human body. For example, whether there is blood flow.

Picture source: Author shooting

For example, when a doctor is checked on the neck of the patient's neck, you can see a clear cross -sectional image of the neck tissue.

Picture source: Author shooting

On this basis, you can see that the color Doppler ultrasound function can be seen that because the blood in the carotid artery moves from the heart towards the brain, that is, it flows towards the ultrasonic probe, so the region of the carotid artery in the image will be displayed as red, which means that the direction of movement will indicate the direction of the movement. For positive information. The blood in the cervical vein flowing the direction of the ultrasonic probe, the direction of movement is negative, displayed as blue.

Other tissues such as blood vessels and muscles have not occurred and the relative movement of probes, and there is no Doppler frequently, and it is not displayed on the screen.

From the above explanation, we can see that the color in the color Doppler image is just to make the tissue movement information more distinguished from the artificial regulations of the organization structure information. It is not the essential difference between color Doppler ultrasound and ordinary B -ultrasound Essence

According to the principle and purpose of color Doppler ultrasound imaging, it is not difficult to think of many color Doppler ultrasound application scenarios, such as checking whether the blood flow movement in a certain area is smooth, etc., we only need to know whether there is an organizational movement, and there is no information on the direction of the organization movement. need.

At this time, you can use black and white images to indicate the motor information detected by the ultrasound system.

The white plaques and motion speed in the imaging area in the figure correspond to the Doppler sports information picture of the blood flow detected by the ultrasound system.

In other words, compared to ordinary B -ultrasound, the difference between color Doppler ultrasound is not to increase the display color, but whether it can obtain the sports information of human tissues from the image, that is, the content in the figure above.

Therefore, the case is solved here. The color Doppler ultrasound can indeed show different colors, but not every imaging map needs to display the color.

Produced: Popular Science China

Author: Zeng Qiu Yuchen (Ultrasound Laboratory)

Producer: China Science Popularization Expo

Edit: Wang Tingting

references

1. Cantisani, V., et al., Color-Doppler ultrasound with Superb Microvascular Imaging (SMI) compared to Contrast Enhanced Ultrasound (CEUS) and CT angiography to identify and classify endoleaks in patients undergoing EVAR. 2016

2. Kurjak, A. Arenas, J., Donald School Textbook of Transvaginal Sonography. 2018.

3. Jensen, J., Linear Description of Ultrasound Imaging Systems: Notes for the International Summer School on Advanced Imaging at the Technical University.

4. MAULIK, D., Doppler Ultrasound in Obstetrics and Gynecology. 2005.

5. Wanming Xi, biomedical ultrasound (upper, lower volumes). 2010.

6. Shi Keren, Guo Yu, phase control array ultrasound imaging detection. 2010.

7. Amsterdam, T.L.S., Diagnostic Ultrasound Imaging: Inside Out. 2004.

8. WOO, J., a Short History of the Development of Ultrasound in Obstetrics and Gynecology. History of ultrasound in obstetrics and gynecology, 2002. 3: P. 1-25.

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