Method for calibrating a medical c-arm x-ray imaging device in terms of its image acquisition geometry, comprising the steps of - positioning an imaging phantom with predetermined geometrical features in a first position inside a maximum detection range of the imaging device, wherein the maximum detection range is a complete volume of space which can be imaged by the imaging device using its full range of motion or adjustability, - acquiring at least one image of the phantom in the first position using the imaging device and recording a corresponding pose of the imaging device, - moving the phantom out of the first position and into at least one other position inside the maximum detection range of the imaging device and acquiring at least one image of the phantom in the at least one other position using the imaging device and recording a corresponding pose of the imaging device, - while moving the phantom, tracking its motion relative to the first position by means of a tracking device (2, 6, 7, 8, 9), - keeping continuous track of a spatial relation between the phantom and the imaging device by tracking the motion of the phantom, - calibrating the medical imaging device based on the acquired images, the corresponding recorded poses of the imaging device, and the tracked motion of the phantom, characterised in that the motion of the phantom is tracked using the imaging device itself as at least part of the tracking device (2, 6, 7, 8, 9), and in that to track the motion of the phantom using the imaging device, the phantom is at least partly permanently kept inside a respective current field of view of the imaging device while being moved and, after the respective at least one image of the phantom in each position has been acquired, the imaging device is moved corresponding to the respective last motion of the phantom before the phantom is again moved to a next one of the other positions. - positioning an imaging phantom with predetermined geometrical features in a first position inside a maximum detection range of the imaging device, wherein the maximum detection range is a complete volume of space which can be imaged by the imaging device using its full range of motion or adjustability, - acquiring at least one image of the phantom in the first position using the imaging device and recording a corresponding pose of the imaging device, - moving the phantom out of the first position and into at least one other position inside the maximum detection range of the imaging device and acquiring at least one image of the phantom in the at least one other position using the imaging device and recording a corresponding pose of the imaging device, - while moving the phantom, tracking its motion relative to the first position by means of a tracking device (2, 6, 7, 8, 9), - keeping continuous track of a spatial relation between the phantom and the imaging device by tracking the motion of the phantom, - calibrating the medical imaging device based on the acquired images, the corresponding recorded poses of the imaging device, and the tracked motion of the phantom, characterised in that the motion of the phantom is tracked using the imaging device itself as at least part of the tracking device (2, 6, 7, 8, 9), and in that to track the motion of the phantom using the imaging device, the phantom is at least partly permanently kept inside a respective current field of view of the imaging device while being moved and, after the respective at least one image of the phantom in each position has been acquired, the imaging device is moved corresponding to the respective last motion of the phantom before the phantom is again moved to a next one of the other positions. characterised in that the motion of the phantom is tracked using the imaging device itself as at least part of the tracking device (2, 6, 7, 8, 9), and in that to track the motion of the phantom using the imaging device, the phantom is at least partly permanently kept inside a respective current field of view of the imaging device while being moved and, after the respective at least one image of the phantom in each position has been acquired, the imaging device is moved corresponding to the respective last motion of the phantom before the phantom is again moved to a next one of the other positions.