Computerized tomographic densitometry of the solitary pulmonary nodule using a nodule phantom.

The successful application of computerized tomographic density analysis for evaluating the solitary pulmonary nodule has previously been described and the technique has since been simplified by using a calcium-equivalent nodule reference phantom. Because published experience with this technique remains limited, the current research reports the Cleveland Clinic experience with the CIRS model III pulmonary nodule reference phantom. Without knowledge of the final diagnosis, the nodule phantom was used as the standard for categorizing 31 nodules in 29 patients as either benign or indeterminate. Secure diagnoses were obtained in all cases. Eleven nodules were called benign and ten proved so, whereas 20 nodules were classified as indeterminate. One lesion, an adenocarcinoma, was falsely called benign using this technique. The excellent density discrimination achieved with CT makes this a superior tool for analysis of the solitary pulmonary nodule, and the nodule reference phantom has greatly simplified the technique of CT densitometry. As demonstrated by this and prior studies, calcification is not a unique feature of the benign lesion and successful clinical application of this technique requires cautious interpretation of results.