A domestic CT machine that costs millions of dollars, the most critical core parts, can not be produced in China and has to rely on imports, the price ranges from 40 to 900,000 yuan, the most expensive thing is that this is still a consumable, and the life is calculated in seconds!
This core component is the CT tube, is it really worth that expensive?
Discover Mystery 1: How CT Tubes Work
X-rays are a type of electromagnetic wave that is penetrating and can penetrate human tissue. In a CT scan, the X-rays produced by the tube are used to penetrate the body and are then received by the detector.
By computer processing of the received X-rays, a two-dimensional or three-dimensional image of the inside of the human body can be reconstructed to provide a diagnostic basis for doctors.
The tube is mainly composed of a cathode, an anode, and a vacuum tube. The cathode is usually a filament that, when heated, releases free electrons. The anode is a metal target that produces X-rays when free electrons hit the anode. The entire tube is pumped into a high vacuum to reduce scattering and loss of electrons during movement.
In simple terms, how it works happens with the following steps:
- Heating the tube cathode filament: When the filament is heated to a certain temperature, the electrons inside gain enough energy to escape from the atom as free electrons.
- Free electrons are produced in the form of converging: these free electrons are accelerated and gathered together under the action of an electric field.
- Applying high voltage electricity to the cathode and anode: By applying a high voltage, the movement of the free electrons is accelerated so that it has enough kinetic energy to hit the anode.
- The free electron beam hits the anode through the cathode: when the free electron hits the anode, the kinetic energy is converted into heat energy and X-rays are produced at the same time.
- Creates an energy exchange: In this process, part of the kinetic energy is converted into heat energy, causing the tube temperature to rise.
- Convert 1% of this electrical energy into X-rays: While most of the electrical energy is converted into heat, about 1% of the electrical energy is still converted into X-rays.
- Emission through the window: The resulting X-rays are emitted through the window of the tube and are received by the detector of the CT device.
Explore the mystery 2: the structure of the CT tube
Are you curious about the structure of the CT tube. The tube is an important part of CT equipment, which is mainly composed of the following parts:
1. Tube sleeve
The sleeve is the shell of the tube that protects the internal components and circuitry. It is usually made of metal materials and has high mechanical strength and corrosion resistance. The inside of the sleeve is usually filled with insulating material to prevent electric shock or short circuits caused by the core coming into contact with the external environment.
2. Die
The die is the core component of the tube and can be divided into anode and cathode. The anode is the part that emits electrons, while the cathode is the part that receives the electrons.
The complex construction of the die enables high-power work with a small focal point. The construction and quality of the die directly affect the imaging quality and longevity of the tube.
3. Radiator
Heat sinks are used to dissipate heat and prevent the die from overheating. Since metal creates thermal resistance in heat conduction, heat sinks can help conduct heat out and maintain the normal operating temperature of the die. The design and material selection of the radiator has a significant impact on the performance and service life of the tube.
4. Insulating oil
Insulating oil is used to insulate and cool the core, preventing damage to the core caused by the high temperatures generated when the current is excessive. Insulating oil can effectively reduce the working temperature of the die and improve its service life. At the same time, the insulating oil can also act as a lubricating effect, reducing friction and wear inside the core.
5. Other accessory accessories
In addition to the above main components, the tube also includes some other accessories, such as circuit boards, connecting cables, etc. These accessories also have an impact on the performance and service life of the tube.
For example, circuit boards are used to control the operating state of the die and regulate the current level, and the connection wire is used to connect the signal transmission between the die and other components.
Exploring Mystery 3: Why is it so difficult to manufacture CT tubes in China?
This tube has a number of unique technical characteristics, including high heat, high vacuum, high voltage, high accuracy, high rotational speed and high momentum. This involves a number of technical fields, and has strict requirements for technology, basic support, and process equipment. As a result, this also brings many difficulties and challenges.
First of all, there are a lot of details that need to be solved to make such a tube. Vacuum, welding process, assembly process and error control are all very demanding, so engineers need to constantly explore and polish the process, which requires a long time of accumulation and a lot of expertise.
In addition, there is still a certain gap between the domestic process and foreign imported products. Engineers need to take their processes to the next level, especially when it comes to maintaining an intact vacuum. If a vacuum cannot be maintained and oxygen is present, the tube is likely to ignite during operation.
In addition to process problems, heat dissipation design is also a difficult point. Due to the problem of electronic energy being converted into heat, the heat dissipation requirements at high speeds, high vacuums, high pressures, and high thermal conditions are very high.
Engineers need to consider not only the heat dissipation requirements of ball bearings and liquid bearings, but also the heat dissipation solution that is suitable for this particular situation. At present, the commonly used ones are anode direct oil cooling and anode direct water cooling.
In addition, the alignment and calibration of the X-ray tube and detector also needs to be carefully addressed. In the process of tube encapsulation, the removal of gases is a problem that must be addressed, especially for hydrogen, which can cause stability and image distortion of the tube.
Despite the many difficulties, we believe that we can overcome these challenges and make better CT tubes as long as we continue to work hard and explore new solutions. Our efforts are not only for the advancement of science and technology, but also for people to enjoy more accurate and high-quality medical imaging diagnostic services.
Mystery 4: CT scans are expensive
CT equipment, as a cutting-edge clinical imaging diagnostic equipment, has a complex and precise structure. Each component has a direct or indirect impact on the overall use effect. The failure of any one component can lead to a degraded performance or failure to function properly of the entire equipment.
For example, the tube is one of the core components of CT equipment, and its function is to generate X-rays. Once the tube fails or is damaged, it will directly affect the normal use of CT equipment.
According to the bidding and procurement information of the mainland, the replacement price of the tube ranges from 40~900,000 yuan. In addition, the tube replacement cycle is closely related to the use of CT equipment.
Generally speaking, the lifespan of the tube is about 2 years, but hospitals with large outpatient volumes may need to replace the tube more frequently, such as a year or even half a year. This is also an important factor that affects the cost of our CT scan.
However, with our country's increasing investment in all walks of life, many high-end core components have been realized from scratch, and it is just around the corner to break through the technical monopoly of CT tubes.
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