CT machine in the medical profession has been widely used in almost all hospitals above the county level with the preparation of such medical devices. Therefore, the medical service is often encountered in the machine. We now briefly look at the basic structure of the CT machine and the main source of the failure.

 

 

A, CT machine's basic structure

 

After years of development, CT machine structure has been greatly improved, increasing the detector layers, scanning speed is accelerating. Species are more numerous. But its composition is basically the same hardware, there are three main parts:

 

1, is partially and with X-ray detector gantry.

 

2 is a console with a computer

 

3, is to lift the patient bed.

 

Structure and function from the point of view can be divided into: control of the computer scanning and image reconstruction of part of the mechanical part of the patient positioning scan - scan frame and down bed. Produce high-pressure X-ray generator and X-ray tube and extract information and data detection part. According to these basic structural features of the CT failed to determine the sub off the basic direction and there is a basis.

 

 

 

Two CT machine fault classification, sources and characteristics

 

CT causes for the failure can be divided into three types: First, due to environmental factors caused the failure is not normal. The second is caused by the improper operation of the fault. Third, the CT component of aging itself, a qualitative change. Parameter drift leading to mechanical wear or failure.

 

 

 

1 failure of environmental factors

 

As the CT room temperature, humidity, air purification degree, CT stability of power supply failure caused by changes in environmental factors that we call failure. For example: poor ventilation, room temperature is too high will lead to certain appliances (such as power supply or transformer) overheating or even burning, circuit board damage. Interruption of the machine protection, detectors and associated circuitry generate excessive temperature drift and other image artifacts; CT supply voltage surges can cause the computer not working properly, the machine running unstable, even pressure is not normal, X-ray instability, eventually leading to image quality, etc.; air purification is not good dirt too easily lead to computer hard life cut short. A number of optical signal transmission control malfunction due to dust accumulation of lead; if humidity is too large, will lead to failure of electronic devices short-circuit fault. Environmental factors directly or indirectly caused by CT is a great harm, even cause permanent damage. Therefore, the operating environment as possible, CT fault less, longer service life.

 

 

 

2 human error caused by improper operation

 

Common human error factors are: lack of time or warm-up routine correction, resulting in uniformity of the image is not normal or good, resulting in CT for patient positioning errors are not allowed to sweep out the image; patients wear a metal image artifacts caused by produce; the same time lead to a variety of operating CT crash; choose scanning parameters increased image artifacts due to improper and so on. CT is usually human error will not lead to a damaging consequences, as long as identify the reasons for the correct procedures to re-operation or shutdown restart, will generally be able to successfully troubleshoot.

 

 

 

3 · CT hardware damage their own main production failure

 

The import of most mature CT is in accordance with the laws of statistical probability of occurrence of failure over time was saddle-shaped trends, which installs a high failure rate during the first six months, six months after a long period of time (5-8 years) in the period of relatively stable low seven or eight years and then began to gradually increase.

 

a · failure of mechanical parts

 

The following mainly from the three major fault were introduced;

 

With the increased life of equipment, mechanical failure but also with the increase every year. Early CT is used to switch a reverse rotation mode in a scan cycle time to complete a very short rotation speed - uniform - slow to stop, and constantly repeated, it led to a higher rate of mechanical failure. For example, speed often appear unstable, easy to generate spin too far out of control, brake, hit, belt too tight too loose. And cable wear, fracture and other failures. Today the vast majority of CT are using slip ring technology, one-way uniform rotation, and some high-end machine also uses magnetic drive technology, which greatly reduced the breakdown of rotating machinery. However, due to the use of slip rings, it also brings some other fault, because the slip ring rotating friction will lead to long-term poor contact, and trigger a series of mechanical and electrical failures, such as spin out of control, high pressure control, ignition (high slip ring), Some (slip ring transmission) control signal loss. So be sure to regularly slip ring maintenance and replacement. Other components are also prone to mechanical failure, such as X-ray collimator mechanical part is easy to get out of control, stuck; fan failure after long-term work; motor rotation control signal of the pulse generator may also occur due to wear or damage such as loss of pulse phenomena.

 

b · X-ray part of the fault generated

 

X-ray CT machine production control points from the following components: high-frequency inverter, high voltage transformers, two-ray tube and the control circuit, high voltage cable. One part of the main inverter is used to transform into a low-frequency added to the high-voltage transformer primary. Common faults are:

 

(1) failure-ray tube itself: such as rotating anode failure, manifested as a large rotating noise. Serious not to switch. Stuck, the exposure generated when the anode overcurrent phenomena; filament part of the fault, the filament off. Cause no radiation; X-ray tube glass core leakage failure resulting in rupture or leakage, not exposure, vacuum drop, high-voltage ignition and so on.

 

(2) generate high-pressure part of the fault: inverter circuit failure, breakdown, etc., high-voltage transformer short-circuit, high voltage capacitor ignition, breakdown. These failures often result in the corresponding fuse has blown. At the same time can not be exposed, or exposure of the automatic protection of the interruption.

 

(3) high-voltage cable fault: a common connector is loose, causing ignition, over-voltage or high voltage, high voltage cable early CT X-ray tube rotation following prolonged use, due to wear and tear caused internal short-circuit high-voltage ignition cables, these failures will normally correspond to the fuse blown.

 

c · computer part of the fault

 

Computer part failure probability is relatively small, it is easy to repair, such as the common keyboard, mouse, trackball, some small problems. Most is the hard disk, tape drives, magneto-optical failure, which is due to the hard disk and more prolonged use, the bad zone is gradually increased, leading to the total damage.

 

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