A method for automatically determining the 3D position and orientation of a radio-opaque medical object in a living body using single-plane fluoroscopy comprising: (a) capturing a stream of digitized 2D images from a single-plane fluoroscope (b) detecting an image of the medical object in a subset of the digital 2D images (c) applying to the digital 2D images calculations which preserve original pixel intensity values and permit statistical calculations thereon, using (i) multiple sequential determinations of a midline of the medical object image, (ii) a plurality of unfiltered raw-data cross-sectional intensity profiles perpendicular to each sequentially-determined midline, (iii) removal of outlier profiles from each plurality of profiles, and (iv) statistically combining each plurality of profiles to estimate image dimensions, thereby to measure the medical-object image from a final estimation of image dimensions (d) applying conical projection and radial elongation corrections to the image measurements and (e) calculating the 3D position and orientation of the medical object from the corrected 2D image measurements.
