Clinical evaluation of breast dose and the factors affecting breast dose in screen-film mammography.

PURPOSE To investigate the factors affecting the mammographic breast dose. MATERIALS AND METHODS The assessment was done on 622 qualified mammograms obtained with use of "variable kV" technique, i. e., semiautomatic mode, in screen-film mammography. Actual breast doses were calculated and analyzed to determine the roles of two screens and three films, two anode/filter selections (Mo/Mo and Mo/ Rh), three imaging projections (craniocaudal, 45 degrees and 60 degrees mediolateral oblique [MLO]), breast thickness, and breast composition. RESULTS Min R 2190 screen provided about half dose of Min R screen. All films used with the faster screen resulted in similar doses in < 50 mm thicknesses (mean, 0.9-1.1 mGy) (P > 0.05). The doses were significantly greater in thicker (> or =50 mm) breasts, in dense breasts, and in 45 degrees MLO view, compared to the < 50 mm breasts, fatty breasts and in 60 degrees view (P < 0.05). CONCLUSION The affecting factors of dose are many, and their complex interrelations are difficult to control in clinical settings. Well tailoring of kVp/anode/filter combination, selection of faster screens and well matched films are mandatory, while 60 degrees instead of 45 degrees in oblique projection can help reducing the dose. However, tailoring of kVp/anode/filter, which should be based on both breast thickness and composition, is difficult to achieve accurately at all times. Therefore, automatic beam quality control should replace the semiautomatic mode in screen-film mammography practice in order to provide easier and more effective control on breast dose and image quality.