放射線画像雑音のランダムドットモデル

抄録

Radiographic noise is mainly composed of X-ray photographic grain noise, fluorescent screen noise called structure mottle and quantum noise called quantum mottle. They consist of inhomogeneously distributed pattern of the grain. In order to analyze the statistical properties of radiographic noise, the random-dot model which is commonly used for photographic grain noise is extended. The extended random-dot model is composed of inhomogeneously distributed pattern of the model grain. Rigorous expressions of the mean transmittance and autocorrelation function of transmittance of the model pattern are obtained theoretically. For a simple inhomogeneous distribution of the grain number, useful approximate expressions of the mean transmittance and autocorrelation function of the model pattern are obtained. Showing numerical examples, theoretical results of the extended random-dot model are compared with experimental results in a practical fluorescent screenfilm system.