1. A method for obtaining a registration of three-dimensional image data with an X-ray imaging system, the method comprising the steps of: obtaining a set of contour points for an image object in each of a plurality of section-planes; a user identifying at least two extreme opposing points on the object in a subject body from at least one X-ray image plane; performing a projection of each contour point on a sampling of the plurality of section-planes for evaluation; selecting the section-plane with the contour point projecting nearest to the user-identified extreme point; the user identifying a three-dimensional center point of the object relative to a X-ray imaging coordinate system; defining a first grid having a predetermined number of intervals at a predetermined interval spacing with the grid center at the user-identified center of the pre-operative image, performing a projection of the center of the three-dimensional image data set onto each grid point for evaluation, and selecting the grid point that when projected minimizes a cost function; iteratively defining a succeeding grid having a predetermined number of intervals at an interval spacing substantially smaller than the preceding grid spacing, with the grid center at the point selected in the preceding grid, performing a projection of the center of the three-dimensional image data set onto each point in the successive grid for evaluation, selecting a grid point that when projected minimizes a cost function, and repeating the iterative step until a grid point that projects within a predetermined minimum is obtained; and defining a translation using the obtained point for registering the three-dimensional contour data with the X-ray imaging coordinate system.