[Distinguishing benign from malignant pulmonary nodules by gradient analysis of digitized chest radiographs]

Twenty-four conventional chest radiographs with small solitary pulmonary nodules were digitized to analyze optical density gradient. An index number, that could reflect sharpness and contrast of tumor lung interface, was calculated to differentiate benign from malignant pulmonary nodules. In four of 12 patients with benign non-calcified nodules, the index number allowed correct classification as a benign lesion.