Effect of Anode/Filter Combination on the Dose and Image Quality of a Digital Mammography System Based on an Amorphous Selenium Detector

A comparison of image quality and glandular breast dose was carried out on two digital mammography systems using i¾? -Se flat panel detectors. The two digital mammography systems currently available from Hologic were compared. The original system utilises Mo/Mo and Mo/Rh as target/filter combinations, while the new system uses W/Rh and W/Ag. Images of mammography phantoms with different simulated breast thickness and various glandular tissue equivalency were acquired under different spectral conditions. The contrast of five details, corresponding to five glandular compositions, was calculated and the AGD needed to visualize a detail with a CNR of 5 was estimated. For each phantom thickness and target/filter combination, there is an optimum voltage which maximizes the AGD. Using the Tungsten tube system there is a dose reduction of 16% at 4 cm and 5 cm, and 35% for 6 cm compared with the dose needed with the Mo/Mo combination.