Patent ID: 7412086

Claim:
A method for setting a relative position of a radiation device and of a patient, comprising the following steps: a) a two-dimensional comparison image is obtained, or has been obtained, by a comparison image recording device, wherein the comparison image corresponds to a current relative position of the patient and of the comparison image recording device; b) a two-dimensional image is reconstructed from a three-dimensional image data set of the patient; c) for a comparison image and a first reconstructed image, which form a first image pair and which corresponds to a first relative position of the patient and of the comparison image recording device, a measure for a mutual image information of the two images of the first image pair is determined, wherein the mutual image information is defined as that information, which one image contains about the other image of the image pair, or wherein the mutual image information is equivalent to the thus defined information; d) in order to obtain an amended image pair, at least one of the following three steps is performed: i) the comparison image is amended, without distortion of image content, ii) the reconstructed image is amended, without distortion of image content, iii) a second reconstructed image is reconstructed from the three-dimensional image data set of the patient, so that the second reconstructed image corresponds to a relative position of the patient and of the comparison image recording device which differs from the first relative position, resulting in the amended image pair comprising a comparison image and a reconstructed image so that at least one of the comparison image and reconstructed image of the amended image pair corresponds to another relative position of the patient and of the comparison image recording device, than the comparison image and the reconstructed image which form the first image pair; e) the measure for the mutual image information is determined for the images of the amended image pair resulting from step d); f) the two previous steps d) and e) are repeated using an optimisation algorithm, until an image pair is found having a maximum of the mutual image information; g) by evaluating changes in the relative position of the patient and of the comparison image recording device in the images, which arise, or have arisen, starting from the first image pair and proceeding until the image pair having the maximum of the mutual image information is found, a geometrical transformation of the actual relative position of the patient and of the comparison image recording device or of another actual relative position or position of the patient is calculated and h) steps c) to g) are repeated, wherein the first reconstructed image is selected, such that it corresponds to a position of the patient or to a relative position of the patient and of the comparison image recording device which is obtained by modifying a previous position corresponding to the geometric transformation calculated in step g).