1. A method for performing coordinate transformation in navigation-guided procedures between an imaging diagnostic tool with at least one reference structure having a known surface geometry and orientation relative to the imaging diagnostic tool, and a position-determining system, characterized in that, the at least one reference structure is contacted with the tip of a pointer at three or more contact points forming a non-isosceles triangle, wherein the tip of the pointer has markers that can be detected by the position-determining system, the coordinates of the contacted points are determined by the position-determining system in a coordinate system of this position-determining system and are transmitted to an evaluation computer of the imaging diagnostic tool, and a transformation matrix, which recursively transforms the coordinate systems of the position-determining system and the imaging diagnostic tool one into the other, wherein the transformation matrix is calculated from the coordinates of the contacted points in the coordinate system of the position-determining system, and from the known surface geometry of the reference structure in a coordinate system of the imaging diagnostic tool, by a computer program in the evaluation computer.