Leeds Test Objects Ltd is a manufacturer of medical X-ray test objects, or phantoms, based in the north of England. These phantoms, the first of which was manufactured in 1955, have become world renowned as a clinical standard for establishing the correct operating performance of X-ray machines, following their adoption for clinical use by the U.K. Health Service (NHS) in 1973 and as a testing protocol by the U.K. Hospital Physicists’ Association (I.P.E.M.) in 1979.