Non-circular cone beam CT trajectories: A preliminary investigation on a clinical scanner

The use of cone beam CT (CBCT) image guidance in interventional and therapeutic procedures is becoming increasingly common. Clinical systems consist of a kV x-ray source mounted opposite a flat panel digital detector often on a C-arm system. The source and detector typically rotate in a circle about the patient. However data acquired in such a circular cone beam manner provides insufficient coverage of the object and thus the reconstructed image volume is degraded by artifacts. Several combinations of trajectories and exact analytical reconstruction algorithms have been proposed to overcome these artifacts, however to the knowledge of the authors few if any of these have been studied with data acquired from a real system, with the exception of the widely used standard helical trajectory. An apparatus for performing non-circular scans without altering a clinical scanner has been constructed and the accuracy of achieving a specified trajectory verified. A Defrise style disk phantom was fabricated to test the reduction of cone angle artifacts. Reconstruction results are shown.