Room: AAPM ePoster Library
Purpose: determine the quantification accuracy of virtual non-contrast/unenhanced images and establish the lower limit of iodine quantification as a function of dose.
Methods: large elliptical-cylindrical phantom mimicking the patient abdomen was scanned on two commercial dual-energy CT scanners. The phantom contained simulated soft tissues, blood, and bone with known elemental composition. It also contained simulated iodine concentrations (0.2-15 mg/mL) and iodine-enhanced blood (0.5-5 mg/mL). The mean absolute CT value error in VNC/VUE images, and mean absolute percent error in iodine-/calcium-/fat-specific images were measured.
Results: images: If excluding the simulated bone, the mean absolute CT value error was 8.0 ± 5.0 HU and 9.0 ± 6.2 HU for the IQon and the Revolution CT, respectively (p=0.61). The mean CT value error of the simulated bone was -90.5 ± 111.6 HU and -98.5 ± 117.8 HU on the IQon and the Revolution CT, respectively (p=0.08). Iodine-specific images: The mean absolute percent error was 13.7% and 8.3% for the IQon and the Revolution CT, respectively, above 0.5 mg/mL, and 150% and 100% less than 0.5 mg/mL. The mean absolute percent error increased from 16.2% at 100% radiation dose to 18.9% and 24% at 75% and 50% dose, respectively, on the IQon; and from 8.8% at 100% dose to 11.1% and 17.8% at 75% and 50%, respectively, on the Revolution CT.
Conclusion: VNC/VUE images are reasonably accurate for the simulated soft tissues and contrast materials, except for the simulated bone. The lower limit of iodine quantification is radiation dose dependent. For typical dose levels, 0.5 mg/mL is the lower threshold for iodine detection accuracy.
Funding Support, Disclosures, and Conflict of Interest: B.L./S.W.A.: GE Research Grant (not related to this study).