Digital mammography detectors have a large linear dynamic range that allows dose optimization. CD-MAM phantom is widely used in image quality assessment on mammography systems. Currently human readers score the phantom, which is time-consuming and leads to intra and inter observer variability. We discuss the design and validation of an algorithm based on the Non-Prewhitening Matched Filter observer that intends to replace human observers in the task of CDMAM 3.4 phantom scoring. Correlation between both observers has been evaluated through a dose study. Correlation has been established between scores obtained by both observers. The algorithm presents a higher sensitivity and a better discrimination power to dose variations, which makes automated scoring of CDMAM phantom a potential tool, free of observer variability, for quality control in screening mammography.