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In iterative reconstruction algorithms, it is very important to calculate the weighting factor quickly and accurately, which directly affects the reconstruction efficiency and accuracy of computed tomography images. In this paper, a new calculation method for accurate length weighting factor is developed. Firstly, the ray equation is determined according to the coordinates of the source and the ray's projection. Second, the intersections of the ray and the equidistant parallel planes along three coordinate axes are calculated, and the points intersecting with the reconstructed object are put into a set. Finally, when the X‐axis coordinates of all points in the set are different, the points are arranged according to their X‐axis coordinates; when the X‐axis coordinates of all points are same, the points are arranged according to their Y‐axis coordinates. The sorted point set is the intersections that the ray traverses the reconstructed object in sequence. The index and weighting factor of all voxels that the ray passes through can be determined by the sorted point set. Compared with the classical Siddon's method, it avoids the step of describing the intersections with parameters, and its calculation speed is increased by nearly 20%. The numerical simulations and real data reconstruction experiments are conducted to validate the proposed calculation method of exact length weighting factor. [ABSTRACT FROM AUTHOR]

In many applications of circular cone-beam computed tomography (CT), it is common that the reconstructed specimens are plate-like. In this paper, a novel method is presented to reconstruct plate-like specimens in a super-short scan, thus reducing imaging time and increasing practical CT system throughput. The algorithm of the proposed method is an improved backprojection-filtration (BPF) algorithm using an integral operator with a fixed integral interval. The results of numerical simulation and real data reconstructions show that the proposed method is a good choice for reconstructions of plate-like specimens, because not only can it yield images with a quality comparable to those obtained with existing algorithms, but it can also reduce imaging time and increase CT system throughput. [ABSTRACT FROM AUTHOR]

In various applications of computed tomography (CT), it is common that the reconstructed object is over the field of view (FOV) or we may intend to sue a FOV which only covers the region of interest (ROI) for the sake of reducing radiation dose. These kinds of imaging situations often lead to interior reconstruction problems which are difficult cases in the reconstruction field of CT, due to the truncated projection data at every view angle. In this paper, an interior reconstruction method is developed based on a rotation-translation (RT) scanning model. The method is implemented by first scanning the reconstructed region, and then scanning a small region outside the support of the reconstructed object after translating the rotation centre. The differentiated backprojection (DBP) images of the reconstruction region and the small region outside the object can be respectively obtained from the two-time scanning data without data rebinning process. At last, the projection onto convex sets (POCS) algorithm is applied to reconstruct the interior region. Numerical simulations are conducted to validate the proposed reconstruction method. [ABSTRACT FROM AUTHOR]

In computed tomography (CT) image reconstruction, the iterative algorithms have many advantages that the analytic algorithms don't have. However, the calculation of system matrix is time-consuming, which affects their application in real-time CT image reconstruction. In this paper, a fast system matrix calculation method is proposed on the basis of that the distance between the voxel and the adjacent rays reflects the contribution of the voxel to the ray projections. Firstly, every voxel is projected at a projection angle, and then the weighting factor is determined according to the distance between the voxel's projection and the adjacent ray projection on the detector. Finally, the ray equations and weighting factors corresponding to every voxel at all projection angles are obtained. The calculation amount of the proposed method are greatly improved compared with the current grid traversal (GT) method, and it has good parallel computing performance. In the simulation experiment, the Shepp-Logan head phantom is reconstructed by using the proposed system matrix calculation method and algebraic reconstruction technique (ART). Compared with GT method, its cost is reduced by nearly 30 %, and its acceleration ratio is four times that of the GT method. The experimental results show that it is a fast and effective method to calculate the system matrix. [ABSTRACT FROM AUTHOR]