A method for computer assisted determination of correction parameters of a medical device (1;3) relative to a target structure comprising the steps of: A) obtaining a medical image of a medical device which comprises a cylindrical reference means and of a target structure by means of a radiographic device, wherein the cylindrical reference means has a different density than the surrounding material of the medical device, a diameter d and a height h; B) determining an actual first position of the medical device with respect to a local system of coordinates fixed with the radiographic device by calculating the position of the cylindrical reference means with respect to the local system of coordinates by means of a numerical procedure using a computer and the medical image; C) calculating the actual first position of the target structure relative to the medical device by using the computer; D) retrieving a desired second position of the medical device relative to the target structure; E) calculating values of one or more correction parameters between the actual first position and the desired second position of the medical device relative to the target structure by means of the computer, wherein F) the numerical procedure essentially comprises the steps of: (i) automatic detection of the projection of the cylindrical reference means in the medical image and determination of a minimum of four characteristic landmarks within the projection of the cylindrical reference means; (ii) generating a virtual geometric representation of the cylindrical reference means; (iii) determining the virtual projection points representing said characteristic landmarks using the virtual geometric representation of the cylindrical reference means; and iv) iterative determination of the position and orientation of the cylindrical reference means by matching the virtual projection points of the virtual geometric representation of the cylindrical reference means with the characteristic landmarks of the projection of the cylindrical reference means, characterized in that G) the medical device comprises a plurality of said cylindrical reference means, preferably two cylindrical reference means, in a known position with respect to each other, wherein the longitudinal axes of the cylindrical reference means are arranged at an angle with respect to each other in a defined manner. A) obtaining a medical image of a medical device which comprises a cylindrical reference means and of a target structure by means of a radiographic device, wherein the cylindrical reference means has a different density than the surrounding material of the medical device, a diameter d and a height h; B) determining an actual first position of the medical device with respect to a local system of coordinates fixed with the radiographic device by calculating the position of the cylindrical reference means with respect to the local system of coordinates by means of a numerical procedure using a computer and the medical image; C) calculating the actual first position of the target structure relative to the medical device by using the computer; D) retrieving a desired second position of the medical device relative to the target structure; E) calculating values of one or more correction parameters between the actual first position and the desired second position of the medical device relative to the target structure by means of the computer, wherein F) the numerical procedure essentially comprises the steps of: (i) automatic detection of the projection of the cylindrical reference means in the medical image and determination of a minimum of four characteristic landmarks within the projection of the cylindrical reference means; (ii) generating a virtual geometric representation of the cylindrical reference means; (iii) determining the virtual projection points representing said characteristic landmarks using the virtual geometric representation of the cylindrical reference means; and iv) iterative determination of the position and orientation of the cylindrical reference means by matching the virtual projection points of the virtual geometric representation of the cylindrical reference means with the characteristic landmarks of the projection of the cylindrical reference means, characterized in that (i) automatic detection of the projection of the cylindrical reference means in the medical image and determination of a minimum of four characteristic landmarks within the projection of the cylindrical reference means; (ii) generating a virtual geometric representation of the cylindrical reference means; (iii) determining the virtual projection points representing said characteristic landmarks using the virtual geometric representation of the cylindrical reference means; and iv) iterative determination of the position and orientation of the cylindrical reference means by matching the virtual projection points of the virtual geometric representation of the cylindrical reference means with the characteristic landmarks of the projection of the cylindrical reference means, G) the medical device comprises a plurality of said cylindrical reference means, preferably two cylindrical reference means, in a known position with respect to each other, wherein the longitudinal axes of the cylindrical reference means are arranged at an angle with respect to each other in a defined manner.