Experimental Study On Linear Scanning CT System

Computed tomography(CT)is a mature nondestructive testing technique.Since CT was first used in clinical diagnosis in 1971,it has gone through nearly 50 years of development and has been widely used in medical diagnosis and industrial nondestructive testing(NDT).CT image reconstruction process is using the projection data from multi-direction to obtain the inner information of object.Therefore,in order to acquiring the sufficient angle projection data,modern medical CT system generally use the slip ring to complete the rotation movement of X-ray source and the detector.As a result,a gantry with a slip ring is indispensable,which is expensive and difficult to be moved around.Hence,modern medical CT system is expensive,which results in that some developing countries and regions can?t afford the cost for research and usage,these disadvantages not conducive to the promotion and application of CT technology.Hence,the research and development of new CT imaging system with mobile,simple structure and low cost has great practical significance.In 2014,a novel CT scanning method,which is based on the reverse translation of the tube/detectors,was proposed by Professor Ge Wang at Resselaer Polytechnic Institute of USA and Professor Fenglin Liu at Chongqing University of China.The system uses the linear motion of the source and detector instead of the rotational motion,which has the characteristics of low cost,simple structure and movable.Based on the system,this paper mainly completes the installation and debugging of this linear scanning system and related experimental research.The main contents of the paper are as follows:(1)Based on the theory of circular trajectory CT scanning CT,The basic principle and image reconstruction algorithm of the linear scanning CT system are studied.We analysised the linear scanning CT imaging model,the basic composition and the basic theory of scanning,then we introduce these several scanning mode: 1T,2T and 3T scanning patterns were compared.Filtering back-projection(FBP)and FDK analytic reconstruction algorithm are studied and applied to fan beam and cone beam linear scanning CT.Further,in order to improve the quality of reconstructed images,an iterative reconstruction algorithm of Total Variation(TV)optimization reconstruction(SART+TV)was introduced.It is a theoretical foundation for the follow-up experiments.(2)We complete the installation and debugging of the linear scanning CT system.On the basis of the foreword design,the main components of ray source,detector and motion control module are installation.The whole structure of the CT control system and the control procedures of the control parts are improved.(3)Based on the simulation environment and the existing test platform,we complete the relevant experimental research.FBP,FDK and SART+TV image reconstruction algorithm were used to perform linear scanning CT simulation under various scanning modes.The simulation results show that the projected data obtained by a linear scan(1T)is truncated and the reconstruction effect is poor.Three linear scanning(3T)and two linear scanning(2T)180 degree projection data is available,and the quality of the reconstructed image is good,The reconstructed images in the 3T scanning mode are not much different in quality from the reconstructed images.In addition,SART+TV algorithm can significantly improve image quality.According to the simulation results,six straight line scanning experiments were performed on the existing test platform,and the reconstructed images achieved by FDK algorithm and SART+TV algorithm were better.(4)The linear scanning CT system was used to study the linear scanning Computed Laminography(CL).First of all,FDK,SART and SART+TV image reconstruction algorithm were used to conduct linear scanning CL simulation in one scanning mode.The simulation results show that,with the increase of the finite Angle,the more projective data collected by the system,the better the reconstruction image quality of the three algorithms.The reconstruction algorithm of FDK is faster,while the SART+TV algorithm performs better in processing noise and truncation data.Using linear scanning cone beam CT system platform competed linear scanning CL experimental research,FDK algorithm and SART + TV were used chip and PCB of the linear scanning CL for global scanning and local scanning experiment,the reconstructed images were better.The experimental results show that the linear scanning CT test platform can not only complete the linear scanning CT study,but also complete the line scanning CL study.