DIMA-magnification mammography: use of phantoms for the investigation of image quality and radiation exposure.

Purpose: A mammographic system has been developed to provide direct radiographic magnification; investigation of image quality and radiation exposure for surveys and aimed exposures were carried out on phantoms and the results compared with two modern screen methods. Material and method: Image quality was defined by contrast transfer function, resolution of low contrast, contrast of large areas and recognition of low contrast detail, using suitable phantoms. Measurements of entrance surface dose were made with a 1 cm(3) flat chamber. Results: For survey examinations, the new mammographic system provided image quality equal to a screen system but using 50% radiation dose. For localised views, the new system used similar radiation dose but provided significantly better demonstration of diagnostic detail. Conclusion: Using a focal spot of 40-120 mu m, the new mammographic system provides markedly improved direct radiographic magnification. With reduced radiation exposure at times, there is a significant gain in diagnostic information compared with current standard systems.