A statistical method for low contrast detectability assessment in digital mammography

Abstract

This study proposes a method to estimate low contrast detectability (LCD) applying a statistical method, based on the analysis of a uniform region. A dedicated test object was designed, made up of an acetate sheet equipped with a central uniform insert and an aluminium step wedge, allowing linear conversion from pixel values to millimeters of aluminium. A Matlab program for automated image analysis was developed. Phantom images were acquired on two different digital mammography systems. Reproducibility and sensitivity to exposure variations of the proposed method were investigated for different dose levels. Further the impact of scattering and attenuation on LCD was studied adding PMMA layers of variable thickness (2 to 7 cm) upon the acetate sheet during exposure in automatic exposure control modality. The statistical method turned out to be a reliable and rapid method for LCD evaluation. Applications include routine assessment of equipment performance for digital mammography systems.