Noise evaluation of PEID

The increasing application of photoelectronic imaging devices in radiology has led to a research program at the University of Arizona sponsored by the Bureau of Radiological Health. Its goal is the objective evaluation of photoelectronic components and systems as they are used in radiology. Of particular interest are such performance characteristics as signal, noise, and spatial resolution. In the first stage of the project, emphasis was placed on the evaluation of signal and noise. An evaluation facility of high precision was assembled, sufficient to permit accomplishment of this task. The findings clearly show that gain variations in phosphor screens (such as CaWO4) lead to a reduction in the signal-to-noise ratio. The reduction is larger when the incident x-ray energy is higher than the k-absorption edge of the material, resulting in k-escape effects (such as for the CsI x-ray image intensifier). However, even in this latter case, the reduction in the signal-to-noise ratio was generally less than 10%, indicating that at the level of the screen or x-ray image intensifier, the signal-to-noise ratio is practically determined by the statistics of the x-ray source, and that of the quantum absorption in the scintillator