【作者】 陈国华；

【导师】 雷威；

【作者基本信息】 东南大学 ， 物理电子学， 2016， 硕士

【摘要】 X射线成像是重要的医学诊断和治疗技术之一。在X射线断层扫描以及对动态器官的成像中,需要X射线源提供高强度的脉冲X射线。传统的热阴极X射线源采用电子受热发射模式,无法实现电子束的快速开关,需要外加机械快门或电子快门来实现快速成像,X射线的利用率低,被诊断对象接受的X射线辐射剂量大。针对热阴极电子源无法实现电子束的快速调制这一技术障碍,本文研究了基于石墨烯复合栅网碳纳米管作为场发射电子源的冷阴极X射线管,设计了脉冲高压发生电路调制场发射电子束,搭建了基于影像增强器的冷阴极X射线源快速成像系统,实现对静态物体和动态物体的快速脉冲成像。本文主要研究内容如下：首先,分析研究了场发射原理和冷阴极X射线管的工作特性,以课题组设计制作的石墨烯复合栅网碳纳米管冷阴极X射线管作为发射源,分析其构成组件及其X射线发射性能。然后,设计并制作了基于IGBT串联的冷阴极X射线管栅极同步驱动电路,该电路以FPGA为脉冲信号源产生1ms～1s脉宽可调的短脉冲,以光纤收发器HFBR-1521/2521实现驱动信号的同步,以IDI414PI驱动器为基础设计隔离驱动电路,最终设计了以5只IXGH10N170串联的IGBT均压电路,该电路耐压值为6kV,可以产生脉宽1ms～1s、幅值0～6kV的高压脉冲驱动信号。在此基础上,借助实验室的X射线机、影像增强器系统搭建了冷阴极X射线源快速成像系统,实现了对静态物体和动态物体的快速成像,并且通过对照实验的成像效果分析论证了驱动信号与成像效果之间的关系。此外,本文还利用传统的胶片成像来测试该冷阴极X射线源的胶片成像性能。结果表明,该冷阴极X射线源快速成像系统能够实现对静态物体和动态物体的快速成像,并且该冷阴极X射线源与传统的胶片成像系统具有良好的兼容性。更多还原

【Abstract】 X-ray imaging is an important technique in medical diagnosis and treatment. In X-ray tomography and imaging of dynamic organs, X-ray source is required to provide high intensity pulsed X-rays. With the method of heating filament to emit electrons, traditional thermionic cathode X-ray source can’t achieve fast switching of electron beam, it needs extra mechanical shutter or electronic shutter to realize fast imaging. The utilization rate of X-rays is low in this method, and the X-ray radiation dose received by the object to be diagnosed is massive.On account of thermionic cathode X-ray source can’t achieve rapid modulation of electron beam, a cold cathode X-ray tube based on graphene composite grid carbon nanotube as field emission electron source is researched in this paper. At the same time, a high voltage pulse generating circuit is designed to modulate field emission electron beam. In addition, a cold cathode X-ray fast imaging system is built with image intensifier, which can realize fast pulse imaging of static/dynamic objects.The main research contents of this paper are as follows:Firstly, the principle of field emission and working characteristics of cold cathode X-ray tube are analyzed in this paper. A Graphene composite gate grid carbon nanotube cold cathode X-ray tube is designed as the emission source and the X-ray emission properties are analyzed.Then, a gate synchronous driving circuit for cold cathode X-ray tube is designed based.on series connected IGBTs. The circuit can generate 1ms～1s short pulse which pulse width is adjustable with a FPGA device. It can synchronize driving signals with fiber optic connector HFBR-1521/2521, and realize isolation drive with IGBT integrated driver IXDI414PI. In this paper, series connected IGBTs voltage equalization circuit is designed based on five IGBTs IXGH10N170, its withstand voltage reaches 6kV, the circuit could generate high voltage pulse drive signal with 1ms～1s pulse width,6kV amplitude.On this basis, cold cathode X-ray source fast imaging system is built in this paper with the aid of existing equipment of X-ray machine and image intensifier system, by the system, fast pulse imaging of static/dynamic objects is realized. Meanwhile, the relationship between driving signal and imaging effect is analyzed by controlled experiment. In addition, traditional film imaging method is adopted to measure the imaging performance of the cold cathode X-ray source.Experimental results shows that, this cold cathode X-ray source fast imaging system can realize fast pulse imaging of static/dynamic objects, and the cold cathode X-ray source has good compatibility with the traditional film imaging system.更多还原