The composition of the cT machine is mainly x-ray (x-ray) generation system, signal receiving system (detector), electronic computer processing system (signal processing and image reconstruction) and auxiliary equipment (monitors, cameras, etc.), the core device is the CT bulb. The core device is the CT bulb tube. The working principle of CT bulb tube (C ding lb wu, sorted x-ray jie 11璩 tube)
1.1 CT bulb tube structure
CT bulb tube is mainly drooping tube core? Tube sleeve? High-voltage circuits, circulating facultative cooling system and other parts of the composition. The core is composed of cup-shaped cathode filament, rotating anode molybdenum-based tungsten target, high-speed bearings, accessory heat sinks and other components.
1.2 cT tube principle of operation
CT bulb tube is actually a large high-vacuum cathode ray diode, is to produce x-rays of the system, the work process is: 12V current for the cathode filament heating, and produce free electron clouds, this time to the cathode and anode plus 40 a 150kV high-voltage power, the potential difference steeply increased in high-voltage electric field driven, in the active free electron beam, from the cathode and the anode, the free electron beam, the free electron beam, the cathode and the anode, the free electron beam, the free electron beam, the cathode and the anode, the free electron beam. State of the free electron beam, by the cathode high-speed impact
hit the anode molybdenum-based tungsten target, and energy conversion occurs, about l% of the electrical energy to form the x-ray, launched by the window, 99% of which is converted to heat, by the heat dissipation system.
x-ray is a short electromagnetic wave with strong penetrating power, and the higher the voltage, the stronger the penetrating power. x-ray will be partially absorbed in the process of penetrating the material that is attenuated, which is the physical basis of X-ray imaging. The use of this principle of human tissue to produce different attenuation of the ray projection, so that the film of silver bromide sensitized by the development of black; and not sensitized by the silver bromide, by the fixation processing for the transparent white, which produces a black and white image, which is the photographic effect. In addition, the degree of penetration of x-ray or the degree of absorption attenuation is also related to the density and thickness of the object being photographed, the imaging of the black and white shadow shown on the hierarchical differences on behalf of the density of human tissue differences, the higher the density, the more absorption, the less penetration, the less light-sensitive, the image of the more white; and vice versa, the more black. The density of human tissue changes when it is diseased, and the black and white shadows of the image change accordingly, which is the principle of diagnostic imaging. The above analog imaging technology, x-ray imaging technology has been combined with computer development for digital x-ray imaging technology, such as CR (computed Radiography) computer radiography and DR (DigitalRadiogra curve J digital ft x-ray photography, etc.o