1. A method of calibrating a computed tomography system including the steps of: mounting a scan geometry defining tool on a rotating object positioning unit of a computer tomography scanner, said scan geometry defining tool having structure at a known location relative to a center of rotation of the object positioning unit; directing a beam from an x-ray source of the computed tomography system through the structure of the scan geometry defining tool, analyzing a detected image after absorption of the x-ray from the scan geometry defining tool, and utilizing said analyzed image to determine a distance from an x-ray location to the center of rotation of the object positioning unit; directing a beam from the x-ray source at a system performance test standard tool and analyzing a number of electronic and computer performance characteristics, and comparing the analyzed characteristics to expected characteristics to provide feedback on the operation of electronic and computer functions within the computed tomography system; and said electronic and computer control characteristics including at least one of beam hardening, a signal to noise ratio feedback, a measured size of a portion of said system performance test standard tool, and measured sharpness and resolution of a detected image.