Studies On CT Analytical Reconstruction Algorithm For Non-circular Trajectory

The CT scanning imaging method of non-circular trajectory is mainly to solve the complex shaped workpiece CT imaging, limited by the imaging system dynamic range and X-ray photon energy, in some traditional circular projection angle, prone to X-ray energy and effective thickness does not match, lack of projection information, CT reconstruction of poor quality and other issues. The existing iterative reconstruction algorithm, which is not restricted by the geometric relations of the trajectory space, has the problems of poor convergence, high computational complexity and large data storage resources, etc. Therefore,the paper mainly focuses on the analytical reconstruction algorithm, whose data storage space is small and the reconstruction speed is fast. Taking concrete products as objects, based on analytic reconstruction condition, rational planning of CT scanning trajectory, this paper studies non- circular trajectory reconstruction algorithm.In this paper, firstly, for the complicated structure component with the characterize of uniform distribution of effective thickness, so we study CT scan trajectory planning,overcoming the limitations of traditional CT circular trajectory, and on this basis, noncircular trajectory reconstruction algorithm was deduced based on FDK. Secondly, since FDK is an approximate reconstruction algorithm, therefore, the accurate reconstruction algorithm based on PI line BPF(back projection filter) and FBP(filtered back projection) is derived,achieving the accurate reconstruction of the spiral trajectory, further improving the quality of the reconstructed image. Finally, according to the problem that the projection data is missing on the limited angle, the method of translating and rotating objects is proposed to compensate the missing data, through the correction of the superposition achieve three-dimensional reconstruction of the object under a limited angle, effectively reducing image artifacts,ensuring the quality of CT image reconstruction with limited angle. In the same time oftheoretical research, experiment analysis has proved the inclined circular trajectory is better than circular trajectory, it has also indicated the reconstruction efficiency of the non-circular trajectory analysis reconstruction algorithm is higher than the iterative reconstruction. It is more effective to implement three-dimensional CT reconstruction of complex products.