Region of interest cone beam tomography with prior CT data

Recent so-called very short-scan fan-beam reconstruction algorithms make it possible to reconstruct objects within the convex hull of the source path provided that the object is completely contained within the filed of view in all projections. In this work, we extend this result to the truncated cone-beam projection scenario that is typical of mobile C-arms in surgery under the assumption that a prior computed tomography scan is available and that the anatomy has only changed due to surgery within the convex hull of the source path. Practical algorithms and simulation results are given.