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Clinical Utility of Dual-Energy CT in the Evaluation of Solitary Pulmonary Nodules: Initial Experience¹

¹ From the Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1, Poongnap-dong, Songpa-gu, Seoul 138-736, Korea (E.J.C., J.W.S., J.B.S., Y.M.J., K.S.S.); and Siemens Medical Solutions, Forchheim, Germany (B.K.). Received November 9, 2007; revision requested January 14, 2008; revision received April 5; accepted April 17; final version accepted May 29. Supported by a grant (2007-439) from the Asan Institute for Life Sciences, Seoul, Korea. Address correspondence to J.W.S. (e-mail: jwsong49{at}amc.seoul.kr).

Purpose: To determine the clinical utility of dual-energy computed tomography (CT) in evaluating solitary pulmonary nodules (SPNs).

Materials and Methods: This study was approved by the institutional review board, and informed consent was obtained. CT scans were obtained before and 3 minutes after contrast material injection in 49 patients (26 men, 23 women; mean age, 60.39 years ± 12.24 [standard deviation]) by using a scanner with a dual-energy technique. Image sets that included nonenhanced weighted average, enhanced weighted average, virtual nonenhanced, and iodine-enhanced images were reconstructed. CT numbers of SPNs on virtual nonenhanced and nonenhanced weighted average images were compared, and CT numbers on iodine-enhanced image and the degree of enhancement were compared. Diagnostic accuracy for malignancy by using CT number on iodine-enhanced image and the degree of enhancement were compared. On the virtual nonenhanced image, the number and size of calcifications were compared with those on the nonenhanced weighted average image. Radiation dose was compared with that of single-energy CT.

Results: CT numbers on virtual nonenhanced and nonenhanced weighted average images and CT numbers on the iodine-enhanced image and the degree of enhancement showed good agreements (intraclass correlation coefficients: 0.83 and 0.91, respectively). Diagnostic accuracy for malignancy by using CT numbers on iodine-enhanced image was comparable to that by using the degree of enhancement (sensitivity, 92% and 72%; specificity, 70% and 70%; accuracy, 82.2% and 71.1%, respectively). On virtual nonenhanced image, 85.0% (17 of 20) of calcifications in the SPN and 97.8% (44 of 45) of calcifications in the lymph nodes were detected, and the apparent sizes were smaller than those on the nonenhanced weighted average image. Radiation dose (average dose-length product, 240.77 mGy · cm) was not significantly different from that of single-energy CT (P = .67).

Conclusion: Dual-energy CT allows measurement of the degree of enhancement and detection of calcifications without additional radiation dose.

© RSNA, 2008