Using both contrast detail and receiver operating characteristic (ROC) evaluation tests, we evaluated different quality images, produced with different film-screen combinations. ROC curves were obtained for six observers who were attempting to detect lung nodules and pulmonary infiltrates. The contrast detail curves were obtained from images of regular circular test patterns of differing contrast, which had been presented to the observers. Our results indicate that contrast detail tests can be used for relative ranking of image systems prior to detailed ROC testing.

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Detection of lung nodules was assessed using a series of radiographs which were either normal or showed only one nodule. Stereoscopic pairs were obtained in 26 cases (10 positive and 16 normal). A "singles" series comprising one radiograph from each pair was presented to each observer on three occasions. The pairs were later presented side by side and finally were viewed stereoscopically. The results indicate that a second shifted radiograph improves detection of lung nodules enough to be cost-effective. The shifted radiographs do not need to be viewed stereoscopically.

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