Choosing proper mammography screen-film system by computer simulation

Although digital mammography is currently being used all over the world, most of the mammographic units are still based on screen-film systems. In these systems, the choice of the best combination between the screen and the film is important to assure image quality. This work presents a computer simulation method to help choosing the proper screen-film system to each application, showing sensitometric parameters for each combination, like speed, latitude and contrast determined by sensitometric curves film and screen-film combination, measured experimentally, using commercial calibrated sensitometer and densitometer, allowing further comparison between them according to the application required. Panthom images are presented showing the results that will be obtained in clinical use. The influence of each screen is also determined. Phantom images were obtained using a known screen-film combination. These images were digitized in a laser scanner. The exposures information is used to predict the final image by using the screen-film sensitometric curve, chosen by the user. The computer simulation was used for evaluating several mammographic films combined with different screens, currently used for mammography. Simulated results were in good agreement with values obtained experimentally. The results obtained with the proposed algorithm confirm the possibility of using this method for evaluating the performance of any screen-film combination considering the sensitometric curve. It can be an important tool for quick evaluation of a screen-film system as it predicts the image characteristics with no unnecessary X-ray exposition.