Optimized reconstruction algorithm for helical CT with fractional pitch between 1PI and 3PI.

We propose an approximate approach to use redundant data outside the 1PI window within the exact Katsevich reconstruction framework. The proposed algorithm allows a flexible selection of the helical pitch, which is useful for clinical applications. Our idea is an extension of the one proposed by KOhler, Bontus, and Koken (2006).

Exact image reconstruction for a circle and line trajectory with a gantry tilt.

We investigate image reconstruction with a circle and line trajectory with a tilted gantry. We derive new equations for reconstruction from the line data, such as equations of filtering lines, range of filtering lines and range of the line scan. We analyze the detector requirements and show that the line scan does not impose extra requirements on the cylindrical detector size with our algorithm, that is, the axial truncation of the filtering lines does not occur.

Extension of the reconstruction field of view and truncation correction using sinogram decomposition.

We propose a novel truncation correction algorithm that completes unmeasured data outside of the scan field of view, which allows extending the reconstruction field of view. When a patient extends outside the detector coverage the projection data are transversely truncated, which causes severe artifacts. The proposed method utilizes the idea of sinogram decomposition, where we consider sinogram curves corresponding to image points outside the field of view.

Formulation of four Katsevich algorithms in native geometry.

We derive formulations of the four exact helical Katsevich algorithms in the native cylindrical detector geometry, which allow efficient implementation in modern computed tomography scanners with wide cone beam aperture. Also, we discuss some aspects of numerical implementation.

Helical cone beam CT with an asymmetrical detector.

If a multislice or other area detector is shifted to one side to cover a larger field of view, then the data are truncated on one side. We propose a method to restore the missing data in helical cone-beam acquisitions that uses measured data on the longer side of the asymmetric detector array. The method is based on the idea of complementary rays, which is well known in fan beam geometry; in this paper we extend this concept to the cone-beam case.