Image Reconstruction And Error Analysis Of ART Algorithm For X-ray ICT

Industrial CT technology has been widely used in medical diagnosis, non-destructive testing and national defense and other fields. Since the CT theory was proposed in the mid nineteenth Century, this technology has been developed rapidly, and it has become the world’s most recognized the best nondestructive testing technology. The attenuation degree of different materials to the X ray is different, and the information of the object can be obtained by using the ray projection at multiple angles, hence, the defects in the object can be observed and the type of material can be obtained. In theory, the technology is not affected by the shape, material and size of the object, and the result of the reconstruction is intuitive and accurate.In this paper, based on the ART algorithm, the image reconstructions under scanning modes of parallel beam, fan beam and cone beam were realized. Under the scanning modes of the parallel beam and fan beam, the reconstructed object was a hollow circle and the pixel size is 128×128. The appropriate parameters were selected to make the reconstruction quality better. The results show that the deviation between the pixel value and the original value of the object boundary is larger than that of the internal of the object. Meanwhile, the square with less model noise was also selected as the reconstruction object and the image quality was improved greatly. The ART algorithm(prepared by C++) was applied to the actual experiment, then the initial image reconstruction was realized, which also can verify the reliability of the program.In the scanning mode of cone beam, a hollow sphere was chosen as the reconstruction object and the voxel size was 128×128×128, the appropriate parameters and the better criterion value reconstruction results were analyzed, the result showed that there was a strip artifact in the slice image of Z=116, in the strip artifact, the calculated volume and the original value of the simulation are very large. The deviation between the voxel values obtained by simulation and original values was very large, the cause of the strip artifact is that the defects were existed in the projection data. In order to verify the above conclusions, taking the human classic head model Shepp Logan as example, two defects were added in the projection data of the center section(the deviation between the projection values of the defects and the nearby projection values were very large), the reconstruction results show that there are two strip artifacts appeared in the center of the slices. In general, in the actual experiment, due to the lack of hardware of CT system, the strip artifact is easy to appear. In the last, the paper discussed the source of the projection defect in the simulation process.