Improving the visibility of radio-opaque markers in mammography

Owing to the high mean film optical densities used in breast screening mammography, and the very high maximum optical densities that can be obtained using modern mammographic film, it is often found that for larger exposures the nominally radio-opaque markers used to identify views, left and right etc., cannot be seen using a normal illuminator. A simple solution to this problem is to back the radio-opaque markers with a thin metal filter chosen to keep the marker information visible over a wide range of exposures. A convenient material for this is copper foil in the form of self-adhesive tape. The improvement in marker contrast produced by this modification is illustrated using point optical density measurements on marked test films produced at the extremes of the mammographic exposure range.