High-energy Industrial Ct Data Acquisition System And Image Reconstruction

Industrial Computerized Tomography (ICT) is a new non-destructive testing technology, which can get 2D grey-scale images of cross sections of detected object. It can distinguish the inner structure, assembly conditions, material type and flaws status of the detected object from different gray in the images. ICT has been widely used many fields, such as aerospace, aviation, military science, petroleum, steel, mechanism, automobile, mine and so on.The paper's work is base on the new 6MeV high energy ICT platform developed by Institute of Applied Electronics (IAE) of China Academy of Engineering Physics. The paper includes three parts:1. Data acquisition prototype software of the high energy ICT is developed. The modeling of data acquisition system based on Object Oriented Technology is researched. The demand analysis of the system is done in detail. The classes were consummated and the relationship is also defined to build the class store. To reduce the coupling degree, the system is built in a three-layer architecture: MVC architecture which includes model layer, view layer, control layer. In addition, the synchronization of the X-ray generation and image acquisition is analyzed. The proper sequence of the image acquisition is designed and the quality of the images is assured. CT projections are acquired through the data acquisition prototype software.2. The correction of CT projections is researched. The factors that lead errors in projections such as random noise, offset, non-uniform response, defective pixels, and impact noise are analyzed, including the reason of the errors, the influence of the errors on digital radiography (DR) images and CT reconstruction images. To correct the projections, several methods are used, including average, linear correction, neighborhood average, and median filter. At last, the projections from detector are logarithm corrected so that they can be used to reconstruct CT images. With these corrections, the errors of projections and the artifacts of CT images are reduced and the quality of CT images is increased.3. The simulation of CT projections and image reconstruction are researched. The calculation of the integral of a line to an ellipsoid is concluded. So projections of a 3D Shepp-Logan head phantom are calculated in analytical form. And the projections of a spatial resolution test card are calculated by Siddon's method in discrete form. 2D Filter Back-projection (FBP) reconstruction algorithm and 3D FDK reconstruction algorithm are researched. The FBP reconstruction formula is rewrite in new form, that only need the parameter DSD (distance from source to detector) to reconstruct. So the parameter DST (distance from source to table) is not necessary to measure when the imaging system magnification ratio is changed. And a fast FBP reconstruction is implemented by symmetry back-projection with recursion technique. The reconstruction speed is increased without loss of image quality.