Evaluation of Signal Detectability with Lung Nodular Reproduction by ROC Analysis using Photographic Density

Abstract

We examined the effect that contrast and graininess of X - ray film/screen system had on the detection of the faint nodular shadows which overlaps with ribs and mediastinum. To evaluate the system, we adopted the receiver operating characteristic (ROC) analysis by the continuously - distributed scale method which using photographic densities of the shadow parts of chest X - rays as data. As a result, the detectability of the screen/film system for chest radiography was significantly higter than that of the conventional system. The result also agreed well with number of noise equivalent quata (NEQ(u)). Therefore, we conclude that this evaluation method is more convenient than NEQ(u), and it seems to be an useful evaluation method integrating contrast and graininess.