Triple-source Swinging Spiral CT (TS-SCT) Imaging For Security Inspection

Computed tomography(CT)is a technique to obtain the internal structure information of an object by means of energy attenuation after X-ray penetrating the object.CT technology is widely used in security inspection,medical diagnosis and industrial components detection because of its advantages of visualization and high spatial resolution.Among them,security inspection CT plays an important role in the detection of passengers' luggage,express parcels,large containers and vehicles.The research on new security inspection CT imaging method has important theoretical and practical values.In this paper,a triple-source swinging spiral CT(TS-SCT)imaging method is proposed,which can be used for the security inspection of passengers' luggage and express parcels.Three groups of X-ray source and detector uniformly distributed in the circumference are used to swing around the rotation center in the range of 120°.At the same time,the detected object moves along the line passing through the rotation center and perpendicular to the plane of the X-ray source and detector to realize the swinging spiral scanning.Compared with spiral CT,this method does not need full rotation,and can use of the rotating parts which are easier to maintain and wear-resistant than the slip-ring.In addition,the cable is used to transmit data and power,which is not limited by the slip-ring.In this paper,the research of TS-SCT imaging method mainly includes the following aspects:(1)TS-SCT imaging theory is studied.Imaging geometry model of TS-SCT is established,scanning mode of TS-SCT is analyzed,relevant scanning parameters of TS-SCT are studied,and the influence of the ratio r of the X-ray forward distance of swing 120° to the projection height of the cone-beam is analyzed;(2)A TS-SCT system is designed.According to the imaging method of TS-SCT,a system structure of CT for security inspection of passengers' luggage and express parcels is designed,and the system composition and working mode of TS-SCT are introduced;(3)TS-SCT image reconstruction algorithms are studied.Based on the research of general cone-beam image reconstruction algorithms and TS-SCT scanning mode,the analytic reconstruction algorithm TS-SCT FDK and iterative reconstruction algorithm TS-SCT SIRT are derived;(4)TS-SCT imaging experiments are fulfilled.In order to verify the feasibility of TS-SCT imaging method and the effectiveness of the reconstruction algorithms,simulation and experiment are carried out.Several groups of TS-SCT control experiments are set to verify the influence of r on the quality of reconstructed image.At the same time,SCT control experiment was set up.Simulation and experiment results show that the two algorithms can effectively reconstruct images,and TS-SCT imaging method is feasible.In TS-SCT FDK algorithm,r has a great influence on the reconstruction result,when r ? 1/2,each layer of reconstructed image can get ideal result,and it is better than SCT r = 1.In SIRT algorithm,r has little effect on the reconstruction result,which indicates that SIRT algorithm can correct image quality degradation caused by uneven sampling.However,the convergence of TS-SCT is not as good as SCT.