With the rapid development of science and technology and my country's medical and hygienic cause, medical X-ray and CT machines have been improved in cities and county-level hospitals in my country, and multi-slice spiral CT is also being used in provincial and municipal key hospitals. Expensive and cost-effective core components, the purchase price ranges from hundreds of thousands of yuan to millions of yuan. During scanning (especially the tubes with enough exposures), tube failures are often reported, and careful inspection and analysis are required to prevent non-fatal failures. Repairing and cleaning in time and restoring normal scanning will not only reduce downtime, ensure good social benefits, but also effectively extend the service life of the tube and create good economic benefits. Some problems with the tube, I hope it can play a role as a guide. I hope that experts and colleagues, teachers and friends will correct me if there is anything wrong.

1 Structural composition of the bulb

ordinaryCT tubeIt is composed of a tube core, a tube sleeve and a matching oil circulation cooling part, and the tube core is composed of a rotating anode, a filament, a tube core glass shell, etc.

2 Factors affecting the service life of the tube

The factors that affect the service life of the CT tube mainly include the following aspects:

2.1 Device debugging of the tube ball

The filament voltage, current, etc. should be adjusted strictly according to the requirements of the technical parameters of the tube, and the front and rear positions, kV, mA, etc. should be calibrated, and the parameters should be checked regularly and adjusted in time. Otherwise, it will not only affect the life of the tube, but also affect the graph. image quality and even artifacts.

2.2 Setting of scanning technical conditions

The main conditions are: kV, mA, scanning time (the time required for the tube to rotate once), layer thickness, pitch, scanning range, reconstruction method and other parameters.

2.3 Working state of the tube ball cooling system

for the most partCT tubeIt is extremely important to pay attention to the working efficiency of the tube-ball cooling system. The most important task is to regularly clean the dust on the filter screen and the dust on the radiator, so that the air flow rate has been maintained in a good state. , improve the cooling efficiency.

2.4 The quality of the tube itself

The rational use of the tube is mainly manifested in the control of the scanning heat capacity. Under the condition of not affecting the image quality, the MAS can be appropriately reduced according to the scanning request and the actual human body scanning image. Adjust the pitch of the parts; regularly check the power supply parameters of the tube and the working status of the cooling system. After the above methods are used to formulate the work routine of each CT, the operators are required to strictly implement it. After more than 2 years of inspection, the average service life of the tube has been greatly improved. improvement.

3 Daily maintenance and maintenance of CT tube

3.1 External 3-phase power detection.

Including the phase of the 3-phase power supply, the phase-to-radio balance is stable, and the phase-to-radio balance, no phase shift, and the resistance of the ground wire and whether the ground is good or not.

3.2 Eliminate animals such as mice and cockroaches.

Because they bite off the wires, pollute the circuit boards, and cause fires are not uncommon.

3.3 The temperature and humidity of the computer room.

If the temperature is too high or too low, the electronic circuit will not work properly. The working environment is too dry, which is easy to cause static electricity; the working environment is too humid, and it is easy to cause circuit short circuit due to humidity such as oxide dust. Usually the working environment temperature is maintained between 20-300, The temperature change rate is less than or equal to 30C\/h, the humidity is 75%, and the humidity change rate is less than or equal to 5%\/h.

3.4 CT detection of various working parameters of the tube, including kV, Ma, temperature, etc. of the CT tube.

3.5 The contact between the high-voltage cable and the bulb is good, and the contact parts are free of impurities. Check it every 2 years.

4 Common faults and maintenance of the tube

For the failure phenomenon caused by the tube and its high pressure, we can roughly summarize it as follows:

4.1 Filament problem Common filament open circuit or half open circuit

The fault is as follows: no exposure after high voltage is applied, no tube current or current is unstable, indicating that the filament is open (or Low mA), under the condition that the power supply of the filament is checked and normal, the open circuit of the measured filament resistance is mostly the open circuit of the tube filament. Need to pay attention to The only thing is: sometimes the filament is in a semi-open state, when it is on and off when it is on, when it is working, the heating causes an open circuit, and when it is powered off, it is cooled and connected, which often causes misjudgment and needs to be repeatedly identified.

4.2 The vacuum degree of the die falls or the glass bulb of the die is damaged

The fault is as follows: check the fault code and generally prompt an overload alarm. One situation is that after the tube core is used for a long time, the filament evaporates, the target surface is damaged and gasified, and the vacuum degree of the tube core is reduced; 2. The tube is not used for a long time, and the tube core has gas. Infiltration, or aging and cracking of the core shell, oil infiltration, high temperature carbonization to generate gas, and the vacuum of the tube core decreases.

4.3 The rotating anode does not rotate

Fault performance: The alarm shows the fault of the rotating anode (Rotor). This fault generally has the following two reasons: one is that the stator coil of the rotating anode is damaged (open circuit or short circuit); the other is that the rotor of the rotating anode is stuck or the bearing is worn after the gap is too large, and the power is turned on. After dispersing the magnetic field imbalance and sucking to death.

4.4 High pressure ignition in the pipe sleeve

When this kind of fault occurs, the alarm will show overload. The looseness of the high-voltage cable plug or the reduction of the sealing insulation between the high-voltage cable and the socket or the cracking of the high-voltage plug can cause intermittent ignition. There are thin interference lines in the middle. Pull out the high-voltage cable plug and check, you can find that the plug and socket have obvious discharge carbonization burn marks, accompanied by irritating breath. After cleaning with anhydrous alcohol and gauze, re-seal the high-voltage rubber pad. It can return to normal after silicone ester or insulating oil.

4.5 Internal ignition of the die

The fault is as follows: as soon as the exposure is started, it is overloaded, indicating overload (Over mA), which usually occurs in the tube with more exposure counts. Sometimes it can be scanned after reducing the kV and mA, but the image is poor. After the tube core is used for a long time, the filament evaporates, The target surface is damaged and gasified, and the vacuum degree of the tube core is reduced; or the glass shell has cracks under high temperature oil pressure, and the tube core has gas infiltration; or the core shell is aging and cracked, oil infiltrates, high temperature carbonization produces gas, and the tube core vacuum degree Landing, the tube is scrapped.

4.6 Oil leakage of pipe casing

Small oil leakage will not affect the work. After a large amount of oil leakage, there will be air bubbles in the tube sleeve, and overload will appear during scanning (fire in the sleeve). Visual inspection can be found, and careful inspection can find the oil leakage part, mostly the tube The joints are loose or the gaskets are aged. Tighten the joints or replace the gaskets to return to normal.

4.7 Tube overheating

The fault is as follows: the waiting time for cooling is too long during the scan, indicating a temperature or oil pressure fault, which is mostly a fault in the oil circulation cooling system of the ball tube. The details can be divided into:

4.7.1 The radiator grid is stuffed with dust, and the heat dissipation is poor, and it is normal after cleaning.

4.7.2 The cooling fan does not rotate, mostly because the winding is damaged or the bearing is stuck. Replace the fan.

4.7.3 The circulating oil pump is broken. The oil pump motor is broken or the bearing is stuck or the oil pump is damaged. Repair or replace it.

4.7.4CT tubeThe oil filter is blocked. There are too many impurities or foreign objects in the insulating oil. It is normal to clean and change the oil.

There are many factors related to the identification of tube failure. How to distinguish whether the tube problem is relatively complicated, we can subdivide it into:

(1) High voltage control loop failure; (2) High voltage inverter (trigger) failure; (3) Anode rotation controller failure; (4) Anode inverter trigger failure; (5) Filament circuit failure; (6) High voltage cable strike (7) Abnormal reaction resistance in the high-pressure fuel tank; (8) breakdown of the silicon stack in the high-pressure fuel tank, etc.

The rational use of the tube is mainly manifested in the control of the scanning heat capacity. Under the condition that the image quality is not affected, the mAS can be appropriately reduced according to the requirements of the scanning site and the actual body scan image; the power supply parameters of the tube and the working status of the cooling system are regularly checked. Through the above methods, the work routines of each CT are formulated and the operators are required to strictly implement them, which can greatly improve the life of the CT.