The radiographic demonstration of calcification in a solitary pulmonary nodule renders the possibility of malignancy extremely unlikely, although rare exceptions have been reported. Conventional roentgenograms and tomograms sometimes provide inconclusive evidence although CT can be highly accurate in both identifying and quantifying calcium content. An alternative method is dual-energy subtraction utilizing scanned projection digital radiography. Forty-one patients with solitary (occasionally multiple) pulmonary nodules were examined with the technique, employing second-generation fan-beam equipment: 28 nodules or masses were noncalcified and 13 calcified. Of the former, 20 were pathologically proved, 16 being malignant and 4 benign (2 granulomas, 2 bronchiectasis); in 3 of the remaining 8, a presumptive diagnosis was reasonably certain (1 granuloma, 2 metastases), while in 5 the diagnosis was not made. In 8 of the 13 calcified lesions, the diagnosis can reasonably be regarded as confirmed as granulomas; 5 are being followed up with that presumptive diagnosis.
