A method for determining a translation of a three-dimensional pre-operative image 
data set to obtain a registration of the three-dimensional image data with a patient positioned in a projection imaging 
system. In one embodiment the user identifies an initial three-dimensional organ center from projections and extreme contour 
landmark points of the object on a set of projections. A set of contour points for the 
image object in each of a plurality of three-dimensional cross-section planes; is obtained and the points projecting nearest to the user-identified 
landmark points are selected. A three-dimensional grid having a predetermined number of intervals at a predetermined interval spacing centered at the user-identified organ center is defined. The three-dimensional image data contour points as centered onto each grid point are projected for evaluation and selection of the grid point leading to contour points projecting nearest to the user-identified 
landmark points. This selection leads to the iterative definition of a series of improved estimated three-dimensional organ centers, and associated translation vectors. Registration of a three dimensional image data to the patient positioned in a projection imaging 
system will allow, among other things, 
overlay of a visual representation of a pre-operative 
image object onto a 
projection image plane that can serve as a 
visual tool and a surgical 
navigation aid. In particular, the position and orientation of a 
medical device can be shown with respect to the three-dimensional image data and thus enable quicker, 
safer, and 
less invasive navigation of the 
medical device to and within an organ of interest.