Routine quality control tests for film-screen mammographic systems with automatic exposure control

Quality control of the contrast and density of mammograms is of extreme importance not only because of patient dose considerations but also because of the need to monitor changes in the breast over extended periods of time. A phantom and test technique has been developed and used at two institutions for monitoring the ability of mammographic generators and phototiming systems to provide consistent contrast and density. The phantom consists of a solid acrylic block and an embedded aluminum step wedge designed specially for low kVp use. Optical densities of various portions of the phantom are used to determine constancy of density and contrast. By minimizing fluctuations due to processing and film handling, normal variations were reduced enough to determine changes in contrast and density due to generator and phototimer changes equivalent to those monitored in processor quality control programs. The data have been correlated with changes in processor function. Changes in density and contrast values have also been related to phototimer malfunction and reduced image quality.