Abstract: A method of positioning a surgical instrument is provided which includes mapping a volume adjacent an operating table by taking mapping images from two orientations of a calibration object which includes a 3-dimensional array of radio opaque markers in a known configuration. A patient is positioned on the operating table with a patient target area within a mapped volume, and an instrument holder carrying a known configuration of radio opaque markers positioned adjacent the target area. Further fluoroscopic target images of the target area and instrument holder are obtained from the two orientations and the target area then reconstructed in 3-dimensions by comparing the target images to the mapping images. An instrument holder orientation is then calculated from the reconstruction.