Are Two-dimensional CT Measurements of Small Noncalcified Pulmonary Nodules Reliable?

PURPOSE: To evaluate the intra- and interreader agreement of two-dimensional computed tomographic (CT) measurements of pulmonary nodules less than 2 cm in diameter. MATERIALS AND METHODS: Three readers independently made three serial measurements of each of 54 pulmonary nodules measuring 3-18 mm that had been observed on standard-dose multisection CT images obtained in 24 patients who ranged in age from 36 to 81 years (mean age, 54.6 years). There were 14 women (58%), who ranged in age from 43 to 81 years (mean age, 58.9 years), and 10 men (42%), who ranged in age from 36 to 65 years (mean age, 48.5 years). The largest transverse cross-sectional diameter of each nodule was measured at picture archiving and communication system, or PACS, workstations by using high-spatial-resolution reconstructed CT images and identical window settings. Intra- and interreader agreement were determined by using methods described by Bland and Altman: the coefficient of repeatability for intrareader agreement, and methods derived from the 95% limits of agreement defined by Bland and Altman for interreader agreement. RESULTS: The repeatability coefficients were 1.70, 1.32, and 1.51 mm for readers 1, 2, and 3, respectively. The 95% limits of agreement for the difference among readers were -1.73 and 1.73. CONCLUSION: Two-dimensional CT measurements are not reliable in the evaluation of small noncalcified pulmonary nodules.