Method for marker-free automatic fusion of 2-D fluoroscopic C-arm images with preoperative 3D images using an intraoperatively obtained 3D data record

A C-arm x-ray apparatus comprising:

• a C-arm on which an x-ray source and a radiation detector are mounted adapted for irradiating a region of a patient during a medical interventional procedure;
• a tool plate mounted to said C-arm;
• a navigation system;
• and
• a control and operating unit for operating said C-arm, said x-ray source and said radiation detector, and for receiving signals from said navigation system, for during a medical interventional procedure involving a region of a patient, intraoperatively obtaining a 3D image of the region using a C-arm x-ray system having a C-arm and having a tool plate attached to the C-arm x-ray system, undertaking an image-based matching of an existing preoperative 3D image of the region, obtained prior to said medical interventional procedure, relative to the intraoperative 3D image, and thereby generating a matching matrix, matching the tool plate relative to a navigation system, obtaining a 2D fluoroscopic image using said C-arm x-ray system with said C-arm at any arbitrary position, determining a projection matrix for matching said 2D fluoroscopic image to said 3D image, and matching said 2D fluoroscopic image with said preoperative 3D image using said matching matrix and said projection matrix.