The DR composed of flat panel detectors is mainly divided into two types: one is the amorphous silicon flat panel detector, which belongs to the indirect energy conversion method; the other is the amorphous selenium flat panel detector, which belongs to the direct energy conversion method. A. Principle of amorphous silicon flat-panel detector: The structure of amorphous silicon flat-panel detector is mainly composed of scintillator and photoreceptor (amorphous silicon layer with photodiode function) and TFT array; its principle is to scintillate After the body is exposed to X-rays, the X-ray photons are converted into visible light, and then the amorphous silicon layer with a photodiode function is converted into an image electrical signal, which is detected by the TFT array (arrangement signal function), and finally obtained by A/D conversion. digitized image. B. Principle of amorphous selenium flat panel detector: the structure of amorphous selenium flat panel detector is mainly composed of amorphous selenium layer and TFT array; the principle is that the amorphous selenium layer directly generates electrical signals after X-ray exposure, and the array is detected by TFT , and then A/D conversion to finally obtain a digital image. Note: Although the image quality of the amorphous selenium flat panel detector is clearer and sharper than that of the amorphous silicon flat panel detector, the working environment of the amorphous selenium flat panel detector is very high during use, and the service life is short. The failure rate is high, and the maintenance cost is much higher than that of amorphous silicon flat-panel detectors. Therefore, amorphous silicon flat-panels dominate the flat-panel detectors in the market.
Flat panel detectors are used for a certain number of years (usually about three years) or after a certain number of exposures, and the flat panel detectors are inevitably damaged due to aging. The high maintenance cost of flat-panel detectors is mainly due to the high integration of internal components, and the unstable physical properties of amorphous silicon oxide transistors, which decay quickly under light, so large areas of dead pixels appear every day. When the number of dead pixels reaches a certain amount, it cannot be repaired, and the entire flat panel detector needs to be replaced. In fact, as of today, there is no flat-panel detector that can be used normally for more than five years. Most flat-panel detectors need to be replaced every two years or so. Since the flat-panel detector technology has been monopolized by foreign countries, its cost is very expensive. . The CCD chip in the CCD detector DR only needs to sense visible light, convert the visible light into an electrical signal, and finally obtain a digital image; its service life is very long. The “consumables” in CCD DR are mainly scintillation screens, and the maintenance of the system is focused on replacing the scintillation screens. The maintenance cost of CCD detector DR is relatively low. Therefore, the service life of the CCD detector DR is far longer than that of the flat panel detector DR, and the post-maintenance cost of the CCD detector DR is much lower than that of the flat panel detector DR. Nowadays, many hospitals only pay attention to the brand, detector structure, high pixel, high configuration, etc. during the purchase of DR, but often ignore the life of the equipment and the cost of later use and maintenance. On the basis of ensuring clinical use, it is the best choice to purchase CCD detector DR with higher stability, longer service life and lower maintenance cost, especially for primary hospitals.
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