Computer aided assessment of image quality for mammography using a contrast detail phantom

The aim of this study is to develop an objective method for image quality assessment for mammography using a computer code to analyse images of a contrast detail (CD) phantom. The results from the computer analysis are compared to those obtained by human observers. The CD phantom is subdivided into a matrix structure of squares. In each square two identical cylinders are milled. The diameters and depths of the cylinders vary along the axes of the CD phantom. Human observers indicate for each square if both objects are visible. To obtain an observer independent scoring, the radiographs are digitised to allow computer analysis. The computer code employs knowledge on each square, such as diameter and potential cylinder positions. The ratios in optical density are determined between the potential test spots and their background. These ratios are ranked to determine the most probable test spot locations. Various parameters are employed to assess the reliability.