Patent ID: 8104957

Claim:
A method for calibrating a C-arm x-ray apparatus, said C-arm x-ray apparatus including an arm having a radiation source and an image intensifier, the method comprising the following steps: a) moving the C-arm x-ray apparatus to an initial position; b) acquiring a calibration image, wherein values for an orbital angle and polar angle of the arm of the C-arm apparatus during acquisition of the calibration image are stored; c) determining a position of the center of projection in the radiation source based on information obtained from the calibration image and the corresponding values for the orbital angle and the polar angle of the arm of the C-arm x-ray apparatus; d) moving the arm to a number of calibration positions in a range of orbital angles and polar angles, and directly measuring a relative position of the radiation source and the image intensifier of the C-arm x-ray apparatus for each calibration position; e) measuring a change in the position of the radiation source relative to the image intensifier of the C-arm x-ray apparatus for each calibration position; f) ascertaining the position of the center of projection corresponding to each calibration position from: the position of the center of projection, as determined in Step c); and from the change in the position of the radiation source relative to the image intensifier; and g) retrievably storing the position of the center of projection for each calibration position.