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Obmann MM, An C, Schaefer A, Sun Y, Wang ZJ, Yee J, Yeh BM. Improved Sensitivity and Reader Confidence in CT Colonography Using Dual-Layer Spectral CT: A Phantom Study. Radiology 2020; 297:99-107. [PMID: 32720868 DOI: 10.1148/radiol.2020200032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Background Limited cathartic preparations for CT colonography with fecal tagging can improve patient comfort but may result in nondiagnostic examinations from poorly tagged stool. Dual-energy CT may overcome this limitation by improving the conspicuity of the contrast agent, but more data are needed. Purpose To investigate whether dual-energy CT improves polyp detection in CT colonography compared with conventional CT at different fecal tagging levels in vitro. Materials and Methods In this HIPAA-compliant study, between December 2017 and August 2019, a colon phantom 30 cm in diameter containing 60 polyps of different shapes (spherical, ellipsoid, flat) and size groups (5-9 mm, 11-15 mm) was constructed and serially filled with simulated feces tagged with four different iodine concentrations (1.26, 2.45, 4.88, and 21.00 mg of iodine per milliliter), then it was scanned with dual-energy CT with and without an outer fat ring to simulate large body size (total diameter, 42 cm). Two readers independently reviewed conventional 120-kVp CT and 40-keV monoenergetic dual-energy CT images to record the presence of polyps and confidence (three-point scale.) Generalized estimating equations were used for sensitivity comparisons between conventional CT and dual-energy CT, and a Wilcoxon signed-rank test was used for reader confidence. Results Dual-energy CT had higher overall sensitivity for polyp detection than conventional CT (58.8%; 95% confidence interval [CI]: 49.7%, 67.3%; 564 of 960 polyps vs 42.1%; 95% CI: 32.1%, 52.8%; 404 of 960 polyps; P < .001), including with the fat ring (48% and 31%, P < .001). Reader confidence improved with dual-energy CT compared with conventional images on all tagging levels (P < .001). Interrater agreement was substantial (κ = 0.74; 95% CI: 0.70, 0.77). Conclusion Compared with conventional 120-kVp CT, dual-energy CT improved polyp detection and reader confidence in a dedicated dual-energy CT colonography phantom, especially with suboptimal fecal tagging. © RSNA, 2020.
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Affiliation(s)
- Markus M Obmann
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Chansik An
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Amanda Schaefer
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Yuxin Sun
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Zhen J Wang
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Judy Yee
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
| | - Benjamin M Yeh
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 513 Parnassus Ave, San Francisco, CA 94117 (M.M.O., C.A., A.S., Y.S., Z.J.W., B.M.Y.); and Department of Radiology, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY (J.Y.)
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