Patent ID: 9687308
Date: 2017-06-27
CPC Classifications: A61B

Claim:
1. A method for computer assisted determination of values of correction parameters for positioning a medical device in spatial relation to a target structure comprising the steps of: A) obtaining a medical image of the medical device and the target structure by means of a radiographic device, wherein the medical device comprises a cylindrical reference means that is surrounded by material of the medical device, and wherein the cylindrical reference means has a different density than the surrounding material of the medical device; B) determining an actual first position of the medical device with respect to a local system of coordinates fixed with respect to the radiographic device by calculating a 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 an actual first position of the target structure in spatial relation to the medical device by using the computer; D) retrieving a desired second position of the medical device in spatial relation 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 in spatial relation to the target structure by means of the computer; and F) positioning the medical device in the desired second position in spatial relation to the target structure using the values of one or more correction parameters calculated in step E); wherein the numerical procedure comprises the steps of: i) automatically detecting a projection of the cylindrical reference means in the medical image and determining 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 virtual projection points representing said characteristic landmarks using the virtual geometric representation of the cylindrical reference means; and iv) iteratively determining 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 minimum of four characteristic landmarks within the projection of the cylindrical reference means v) automatically detecting a lens-shaped projection of the cylindrical reference means in the medical image and determining two points of intersection and the a first and second apex of the lens-shaped projection of the cylindrical reference means; vi) generating the virtual geometric representation of the cylindrical reference means with the diameter d, the longitudinal axis, the center and the height h; vii) determining the virtual projection points representing the two points of intersection and the first and second apex using the virtual geometric representation of the cylindrical reference means; and viii) iteratively determining 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 two points of intersection and the first and second apex of the lens-shaped projection; and additionally comprising the step of transmitting the values of the correction parameters to a robotic positioning device wherein the positioning of the medical device in the desired second position relative in spatial relation to the target structure is effectuated by means of the robotic positioning device.