Research On Electron Beam Deflection Scanning System Of Micro-focus X-ray Source For Stationary CT

Since the traditional CT source can only perform single focus projection scanning,to get multi-view projection data,the X-ray source and detector are required to rotate relative to the object consistently.However,the conventional CT has difficulty in improving the scanning speed,and the mechanical movement during the scanning will cause artifacts.Electron beam CT is a new type of stationary CT,during the scanning process,the source,the object and the detector are kept in a stationary state,which overcomes the problem of low efficiency of traditional cone beam CT detection and avoids mechanical motion,so as to improve the spatial resolution of CT greatly.Therefore,it is of great significance and application value to realize stationary scanning method.The high-precision electron beam deflection system is an important part of the multifocus X-ray source for stationary CT,and the performance parameters such as electron beam deflection scanning accuracy,repeatability and linearity determine the spatial resolution,density resolution and other indicators of the stationary CT system.In this paper,the research on the electron beam deflection scanning system of micro-focus Xray source for stationary CT is carried out under the support of National Instrument Special(2013YQ030629).The specific researches are listed as follows:(1)The theoretical calculation,simulation analysis and system design of the electron beam deflection are completed.Firstly,the physical principle and the deflection sensitivity of the magnetic field deflection are analyzed.Then,the deflection magnetic field is designed,and the magnetic field characteristics of the deflection magnetic field are tested based on the Hall Effect using a Gauss meter.The possible aberrations of the deflection scanning are analyzed.Finally,the calculation method of focus position offset based on projection image method is explained in detail,which provides a theoretical basis for the precise control of electron beam and the conversion of parameters in subsequent deflection scanning experiments.(2)The design and programming of the electron beam deflection control software is completed.Based on MFC(Microsoft Foundation Classes),the PC interface and functions of control software are written.The control software can realize communication and data transmission with the deflection amplifier,which is composed of four functional modules: scanning control,parameter setting,cache query and data management.(3)The main parameters such as spatial resolution and linearity of the electron beam deflection are verified through experiments.Based on the electron beam deflection system designed in this paper,a stationary CT system for deflection scanning imaging is established.The spatial resolution of the electron beam deflection stationary CT system measured by JIMA card can reach 4?m or more;The test results of focus position test card show that the deflection current value and focus position offset is highly dependent,and the system has ideal linearity characteristics;When the X-ray source tube voltage is set to 40 kV and 60 kV,respectively,the deflection scanning experiments in the x and y directions are performed,which verified that the deflection system has good repeatability and stability.(4)The stationary CT scanning experiment of electron beam deflection is completed.The toothpick sample is scanned by electron beam deflection scanning,and CT images with micron resolution are obtained.It is proved that the electron beam deflection system of micro-focus X-ray source meets the requirements of theoretical design.