[Picture quality and film mammography. I. The physical parameters of the filming system (gradation, sensitivity, definition and granularity) and the effect of exposure geometry (author's transl)].

The physical parameters of three radiographic filming systems used for mammography were analysed (industrial film without screens, lo dose system (Dupont), industrial film with lo dose screens). Their effect on image quality was studied and the influence of the exposure geometry on sharpness and detail was investigated experimentally. Geometrical unsharpness so reduces the difference in definition between screenless industrial film and a film-screen combination that the total unsharpness at the centre of the breast parenchyma of an average breast becomes approximately the same. In particular, recognition of fine detail (microcalcification) is reduced by geometric unsharpness. Final grading of the three film systems is only possible after development of a concept of film quality which takes account of the parameters of the filming system and of exposlre geometry, together with physiological and practical requirements (paper II).