OPTIMIZATION OF IMAGE QUALITY IN MAMMOGRAPHY

In mammography it is particularly important that the maximum amount of diagnostic information is obtained from each radiograph. One of the factors influencing image quality is the optical density of the film. In this work the Newcastle contrast-detail test object was used to establish the optimum optical density value for one film-screen combination. Films taken using various mA.s values were developed in a nominally optimised film processor to mimic the real situation. The films were then viewed under optimum conditions on a variable brightness lightbox and the threshold contrast for each disc size calculated. Threshold contrast was plotted against optical density for each disc size and a curve fitted through the points. The optimum optical density, taken as being the point at which the threshold contrast is a minimum varied little with disc size. Averaged over all disc sizes the value of optimum density for this particular case was found to be 1.71 OD.