マンモグラフィ用カセッテにおける密着不良の評価 : ワイヤメッシュ法による濃度変化について

Abstract

Mammographic screen-film cassettes require quality control to obtain high definition in mammographic images. Evaluating screen-film contact is necessary for quality control because poor screen-film contact results in image degradation. Areas of poor contact are detected as darker regions in a copper mesh test pattern. However, we have not obtained any information regarding poor contact. Using an embedded spacer, we examined how trapped air caused by poor contact influenced density. With a fixed amount of trapped air space, the difference between optical average density in areas of good contact and those of poor contact increased according to the increase in milliampere-seconds. In addition, the microdensitometer density of wire in areas of good contact did not change, whereas that in areas of poor contact increased. Under a condition of fixed exposure, the optical average density for areas of poor contact increased according to increases in the amount of trapped air space. It is considered that suitable exposure is required to evaluate screen-film contact using a copper mesh.