Camera-Augmented C-Arm

In the medical imaging research community, there has been a considerable effort in replacing fluoroscopic guidance with an interactive and intuitive display of 3D reconstructions of the target anatomy. Within the scope of our project, conventional intraoperative c-arm systems are now being extended with a (tracking) camera that is firmly attached to the frame of the device. Through an offline calibration process, we are able to co-register the two modalities. The resulting system enables intuitive augmented reality visualizations. Since the publication of the first concept in 1999 [1], numerous further developments have been proposed, such as the calibration of 2D/3D cameras [2-4], trackers [5] and more recently HMD systems [6]. In the last two decades, our research partners have published more than 60 articles about CAMC research.

Further information about the research project, all publications and a historic outline of the project including a presentation of selected papers can be found on Medical Augmented Reality.

In our current research project, we developed a novel radiation-free concept to calibrate a tracker to the c-arm gantry. [7] By using a tracking system, the center of rotation of the c-arm can be determined by analyzing the mechanical configuration of the X-ray system. As shown in the video, trajectories during the rotation of the mobile C-arm system around its main axes are independently recorded. These trajectories span the surface of a spindle torus whose mathematical formulation describes the rotation center of the system. By decomposing this 3D fitting problem into two-dimensional subproblems, the recorded trajectories can be used to determine the position and orientation of the center of rotation, which is crucial for the spatial localization of X-ray images and the reconstruction of 3D volumes of the patient's anatomy. The result of this offline calibration can be applied to provide intuitive AR applications in orthopedic surgery.