CT reconstruction with extended z-range

In circular cone-beam CT the Feldkamp (FDK) algorithm is the most prominent image reconstruction algorithm. For example in radiation oncology images reconstructed with the Feldkamp algorithm are used for accurate patient positioning. The scan and reconstruction volume is limited by the size of the flat panel detector. Flat panel detectors, however, are expensive and difficult to manufacture in large size. For numerous treatment techniques, extending this scan volume would be very benecial. In most applications data from 360° or more are available. However, usually only those slices are reconstructed where each pixel is viewed under the full 360° range. Yet for a 360° scan there are regions that are viewed by less than 360°, namely those that lie further of the plane of the circular source trajectory. Performing a reconstruction also for those slices where all voxels are seen at least by 180° will extend the z-range and therefore increase the dose usage.