Parallax-free intra-operative X-ray image stitching

We present a novel method to generate parallax-free panoramic X-ray images during surgery by enabling the mobile C-arm to rotate around its X-ray source center, relative to the patient's table. Rotating the mobile C-arm around its X-ray source center is impractical and sometimes impossible due to the mechanical design of mobile C-arm systems. In order to ensure that the C-arm motion is a relative pure rotation around its X-ray source center, we propose to move the table to compensate for the translational part of the motion based on C-arm pose estimation. For this we employ a visual marker pattern and a Camera Augmented Mobile C-arm system that is a standard mobile C-arm augmented by a video camera and mirror construction. We are able to produce a parallax-free panoramic X-ray image independent of the geometric configuration of imaged anatomical structures. Our method does not require a fronto-parallel setup or any overlap between the acquired X-ray images. This generated parallax-free panoramic X-ray image preserves the linear perspective projection property. It also presents a negligible difference (below 2 pixels) in the overlapping area between two consecutive individual X-ray images and has a high visual quality. This promises suitability for intra-operative clinical applications in orthopedic and trauma surgery. The experiments on phantoms and ex-vivo bone structure demonstrate both the functionality and accuracy of the method.