Absorption and noise in cesium iodide x‐ray image intensifiers

The measured and theoretically predicted values of detective quantum efficiency (DQE) for a CsI x-ray image intensifier are compared for nine monoenergetic beams of x rays. The agreement between measurement and theory of better than +/- 5% indicates that we have a sound understanding of the physical parameters controlling the DQE. It is shown that the fraction of K-fluorescent x rays escaping from the input phosphor is independent of incident energy. The number of electrons released within the x-ray image intensifier (XRII) by an incident x ray has been measured. The mechanism for energy broadening within the XRII is shown to be predominantly the limited number of electrons and not light absorption.