Noise Measurements On Rare-Earth Intensifying Screen Systems

Many popular examples exist for demonstrating how the statistics begin to show (and picture quality deteriorates) when atempts are made to form images with smaller and smaller numbers of photons (Ref. 1, 2). That this state of affairs reigns even in general purpose screen-film radiography has been shown over a dozen years ago by Cleare et al. (Ref. 3) and by Rossmann (Ref. 4, 5). The expression "quantum mottle" was invented to describe the blotchiness or clustering of film grains through which this effect is manifested. Quantum mottle, together with two additional but lower level sources of noise, namely screen structure mottle and film graininess, have been quantitatively analyzed in a series of experiments by Doi (Ref. 6). A few more examples of quantification of such radiographic screen-film noise can be cited (Ref. 7-10), but the samples studied are few and generally unidentified.