Increasing Visual Detectability in Reduced Exposure Mammography by Contrast Adjustment

The radiobiologic level from an average direct-exposure, fine-grain mammograph approaches 4000 millirads. Copying reduced-exposure mammographs onto high gradient films yields a method of reducing radiation to the patient by a factor of 2. A mathematically based tone-reproduction system was developed in an attempt to produce acceptable facsimile images from a series of reduced-exposure mammographs. Acceptability was tested by radiologists using a sensitometric phantum. The radiologists were asked to quality rank a full exposure mammograph, facsimile mammographs, and a film-screen mammograph in terms of detectability of size and number of calcifications. Based on evidence, there is reason to believe that a facsimile mammograph produced with 50 percent normal radiation is diagnostically equivalent to a film/screen mammograph. However, even with this reduction in photographic and radiobiologic exposure, film/screen combination mammographs result in approximately 500 millirads, thus making them superior in terms of patient irradiation