Modified FDK Algorithm for Cone-Beam Reconstruction with Efficient Weighting Scheme

The FDK algorithm to reconstruct cone-beam (CB) data suffers from the density drop with increasing cone angle under a circular trajectory. To overcome the drawback, a rotation-angle-dependent weighting scheme is presented to modify the FDK algorithm. By the analysis of rotation angle increment of the tilted fan plane, CB reconstruction is subdivided into a set of filtered backprojections, each of which is implemented on the corresponding family of planes (FOPS) with the same tilted angle relative to the midplane. Based on such decomposition, there are two important details neglected by the FDK algorithm. The first is that rotation angle in the FOPS isn´t equal to the angle in the midplane at the same projection view. The second is that limited-angle projections are acquired on the FOPS. Hence, a rotation-angle-dependent weighting scheme is increasingly developed to obtain three modified FDK algorithms in combination with Parker´s window function and the characteristic of the short-scan CB reconstruction. Simulated experiments show that they can all compensate for the density drop inherent to the FDK algorithm on the different level