Solitary pulmonary nodules: evaluation with a CT reference phantom.

The Zerhouni computed tomographic (CT) reference phantom was used to study 112 solitary pulmonary nodules that were indeterminate with plain tomography. Of the 112 nodules, 33 were more attenuating than the reference phantom and 79 less attenuating. One patient with a previous endometrial malignancy had a pulmonary metastatic lesion that was more attenuating than the reference phantom, presumably due to microscopic calcification. The nodule in the other 32 cases was benign, as determined from follow-up studies of up to 4.5 years or by means of surgical sampling (two patients). Among the 79 nodules that were less attenuating than the reference phantom, 26 were malignant, 22 were benign, and 31 were followed up for up to 4.5 years with no evidence of malignancy. In this series, the CT reference phantom proved to be a useful adjuvant to plain tomography in patients whose nodules were uncalcified and had an indeterminate shape.