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Virtual noncontrast renal imaging using dual-energy CT: evaluation of CT numbers of renal parenchyma and renal masses

Satomi Kawamoto, Xiaodong R Zhou, Christianne Leidecker, George SK Fung, Benjamin MW Tsui and Elliot K Fishman

Aims: To evaluate the subjective image quality and accuracy of CT numbers of renal parenchyma and masses on virtual noncontrast (VNC)-CT created from contrast-enhanced dual-energy CT datasets using a first or second generation dual source scanner.
Material & Methods: A total of 62 patients referred for dedicated urinary tract CT were evaluated. 30 patients were scanned on a first generation scanner (80/140 kVp tube voltage set), and 32 patients on a second generation scanner (100/140 kVp with tin [Sn] filtration). After administration of intravenous contrast material, arterial phase CT was acquired in the dual-energy mode, and VNC-CT images were created using commercial software at the vendor’s default setting. Subjective image quality, and the CT numbers of renal parenchyma and renal masses (including cysts and solid masses) on VNC-CT were compared to standard noncontrast (SNC)-CT.
Results: Subjective image quality of VNC-CT was better at 100/140 kVp with Sn filtration than at 80/140 kVp. The CT numbers of renal parenchyma were lower on VNC-CT than on SNC-CT, both at 80/140 kVp (20.4 ± 9.8 Hounsfield units [HU] vs 29.2 ± 3.4 HU, p < 0.0001) and 100/140 kVp with Sn filtration (25.7 ± 5.5 HU vs 28.7 ± 3.2 HU, p < 0.0001). The CT numbers of renal masses were lower on VNC-CT than on SNC-CT at 80/140 kVp (-0.2 ± 15.4 HU vs 10.9 ± 13.2 HU, p < 0.0001), but not significantly different at 100/140 kVp with Sn filtration (10.6 ± 14.8 HU vs 11.2 ± 12.5 HU, p = 0.5080).
Conclusion: VNC-CT is useful for evaluation of renal masses. The second generation scanner was more accurate, with small differences in the CT numbers between VNC-CT and SNC-CT in renal parenchyma and renal masses.