Comparison between Conventional Unenhanced and Virtual Unenhanced Imaging of Hepatopancreaticobiliary System with Third-Generation Dual-Source Dual-Energy CT—An Observational Study

Abstract

Objectives The aims of our study were to assess the comparability of conventional unenhanced images (CUIs) of hepatopancreaticobiliary system with virtual unenhanced images (VUIs) derived from arterial and portal venous phases acquired in a third-generation, dual-source, dual-energy CT (DECT), and also to assess the best dataset among these VUIs. We also calculated the radiation effective dose (ED) reduction by eliminating noncontrast acquisition.

Materials and Methods 60 patients were included in our study. Unenhanced images in single energy and contrast-enhanced images in dual-energy mode were acquired. Arterial virtual unenhanced (AVU) and portal virtual unenhanced (PVU) images were generated and compared with CUI, using both objective and subjective methods. The ED was calculated separately for each phase. Statistical significance between difference in mean attenuation values were analyzed using ANOVA and unpaired student t-test.

Results In our study, the difference in mean attenuation of liver, spleen, and pancreas between the three phases—CU, AVU, and PVU—were insignificant with p-value > 0.05. This indicates that the values were comparable. Among the VUI, AVU images were statistically superior in image quality. Elimination of noncontrast CT from triple phase abdominal imaging can achieve an average ED reduction of 39%.

Conclusions We conclude that VUI generated in third-generation, dual-source DECT has diagnostic image quality and can replace the CUI in triple-phase studies, with a mean ED reduction by 39%. The VUI obtained from arterial phase is superior to those obtained from portal venous phase.

Keywords

True unenhanced - Virtual unenhanced - Third generation - Dual source - Dual energy - Radiation dose

Publication History

Article published online:
18 June 2021

• References

• 1 Johnson TR. Dual-energy CT: general principles. AJR Am J Roentgenol 2012; 199 (05) (Suppl) S3-S8
• 2 Coursey CA, Nelson RC, Boll DT. et al Dual-energy multidetector CT: how does it work, what can it tell us, and when can we use it in abdominopelvic imaging?. Radiographics 2010; 30 (04) 1037-1055
• 3 Raptopoulos V, Karellas A, Bernstein J, Reale FR, Constantinou C, Zawacki JK. Value of dual-energy CT in differentiating focal fatty infiltration of the liver from low-density masses. AJR Am J Roentgenol 1991; 157 (04) 721-725
• 4 Silva AC, Morse BG, Hara AK, Paden RG, Hongo N, Pavlicek W. Dual-energy (spectral) CT: applications in abdominal imaging. Radiographics 2011; 31 (04) 1031-1046 , discussion 1047–1050
• 5 Mileto A, Mazziotti S, Gaeta M. et al Pancreatic dual-source dual-energy CT: is it time to discard unenhanced imaging?. Clin Radiol 2012; 67 (04) 334-339
• 6 Johnson TR, Krauss B, Sedlmair M. et al Material differentiation by dual energy CT: initial experience. Eur Radiol 2007; 17 (06) 1510-1517
• 7 Schenzle JC, Sommer WH, Neumaier K. et al Dual energy CT of the chest: how about the dose?. Invest Radiol 2010; 45 (06) 347-353
• 8 Solomon J, Mileto A, Ramirez-Giraldo JC, Samei E. Diagnostic performance of an advanced modelled iterative reconstruction algorithm for low contrast detectability with a third generation dual source multidetector CT scanner: potential for radiation dose reduction in a multireader study. Radiology 2015; 275 (03) 735-745
• 9 De Cecco CN, Buffa V, Fedeli S. et al Dual energy CT (DECT) of the liver: conventional versus virtual unenhanced images. Eur Radiol 2010; 20 (12) 2870-2875
• 10 Gordic S, Desbiolles L, Stolzmann P. et al Advanced modelled iterative reconstruction for abdominal CT: qualitative and quantitative evaluation. Clin Radiol 2014; 69 (12) e497-e504
• 11 Li Y, Li Y, Jackson A. et al Comparison of virtual unenhanced CT images of the abdomen under different iodine flow rates. Abdom Radiol (NY) 2017; 42 (01) 312-321
• 12 De Cecco CN, Muscogiuri G, Schoepf UJ. et al Virtual unenhanced imaging of the liver with third-generation dual-source dual-energy CT and advanced modeled iterative reconstruction. Eur J Radiol 2016; 85 (07) 1257-1264
• 13 Chiro GD, Brooks RA, Kessler RM. et al Tissue signatures with dual-energy computed tomography. Radiology 1979; 131 (02) 521-523
• 14 Millner MR, McDavid WD, Waggener RG, Dennis MJ, Payne WH, Sank VJ. Extraction of information from CT scans at different energies. Med Phys 1979; 6 (01) 70-71
• 15 Kalender WA, Perman WH, Vetter JR, Klotz E. Evaluation of a prototype dual-energy computed tomographic apparatus. I. Phantom studies. Med Phys 1986; 13 (03) 334-339
• 16 Kelcz F, Joseph PM, Hilal SK. Noise considerations in dual energy CT scanning. Med Phys 1979; 6 (05) 418-425
• 17 Graser A, Johnson TR, Hecht EM. et al Dual-energy CT in patients suspected of having renal masses: can virtual nonenhanced images replace true nonenhanced images?. Radiology 2009; 252 (02) 433-440
• 18 Durieux P, Gevenois PA, Muylem AV, Howarth N, Keyzer C. Abdominal attenuation values on virtual and true unenhanced images obtained with third-generation dual-source dual-energy CT. AJR Am J Roentgenol 2018; 210 (05) 1042-1058
• 19 Laukamp KR, Ho V, Obmann VC. et al Virtual non-contrast for evaluation of liver parenchyma and vessels: results from 25 patients using multi-phase spectral-detector CT. Acta Radiol 2019; 0 (00) 1-10
• 20 Lee HA, Lee YH, Yoon KH, Bang DH, Park DE. Comparison of virtual unenhanced images derived from dual-energy ct with true unenhanced images in evaluation of gallstone disease. AJR Am J Roentgenol 2016; 206 (01) 74-80
• 21 Lehti L, Söderberg M, Höglund P, Wassélius J. Comparing arterial- and venous-phase acquisition for optimization of virtual noncontrast images from dual-energy computed tomography angiography. J Comput Assist Tomogr 2019; 43 (05) 770-774
• 22 Kaza RK, Raff EA, Davenport MS, Khalatbari S. Variability of CT Attenuation measurements in virtual unenhanced images generated using multimaterial decomposition from fast kilovoltage-switching Dual-energy CT. Acad Radiol 2017; 24 (03) 365-372