1. 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: capturing a stream of digitized 2D images from a single-plane fluoroscope; detecting the image of the medical object in a subset of the digital 2D images; applying pixel-level geometric calculations to measure the medical-object image; applying conical projection and radial elongation corrections to the image measurements; and calculating the 3D position and orientation of the medical object from the corrected 2D image measurements.