Radiographic mottle and patient exposure in mammography.

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Abstract
Radiographic mottle was analyzed in mammography using a comprehensive theory that takes into account fluctuations in absorbed X-ray energy and in phosphor light-photon yield, as well as film granularity and random variations in phosphor coating. Density fluctuations, signal-to-noise ratios and quantum-efficiencies are presented for 2 screen/film systems as functions of density and viewing-aperture size. For sampling apertures of less than 500 .mu.m in diameter, film granularity is the dominant source of noise for a Kodak Min-R screen/film system. This implies that quantum mottle can be increased and patient exposure reduced with little or no loss in imaged information. Such is the case for the 2nd combination, a Min-R screen combined with Ortho-M film.