A New FBP-type Algorithm on Improving Feldkamp Reconstruction for Z-axially Untruncated Data from a Circular Orbit

The Feldkamp algorithm is the most popular algorithm for circular cone-beam CT. In spite of its approximate character, it preserves four good properties of accuracy. Recently, we expanded the reconstruction definition domain of Feldkamp algorithm to all the points in 3D space. We proved the Feldkamp reconstruction in this expanded definition domain preserves the value of integrals along oblique lines in an oblique angular range larger than the original Feldkamp reconstruction. In this paper, we find the Feldkamp algorithm backprojects some available information outside the actual object support, even the whole 3D space. In other words, if we can draw the Feldkamp reconstruction value outside the object and append them to inside the object, the Feldkamp reconstruction would be greatly improved. So, we use the computed exact stereogram to improve the Feldkamp reconstruction to produce satisfactory images in the case of relatively large cone angles without increasing any radiation dose. Finally, numerical simulations are present to demonstrate the effectiveness of the improved algorithm.