Compatibility of true and virtual unenhanced attenuation in rapid kV-switching dual energy CT

PURPOSE We aimed to evaluate whether virtual unenhanced images generated from nephrographic phase on rapid kV-switching dual energy computed tomography (rsDECT) can replace true unenhanced images by comparing attenuation values of various intraabdominal structures. METHODS In this retrospective study, 142 patients had unenhanced and nephrographic phase DECT images. Attenuation values of the aorta, liver, spleen, pancreas, bilateral renal parenchyma, inferior vena cava, gallbladder and paraspinal muscle on true and virtual unenhanced images were recorded. Frequency of organs that had more than 10 and 20 HU of attenuation difference were also calculated. RESULTS A total of 1224 regions of interest were sampled. No statistically significant differences were found between true and virtual unenhanced attenuation of the aorta, spleen and pancreas. The other structures had significant differences (P < 0.001). Correlation between measurements were weak to moderate (r, 0.17-0.72). Of the organs, 20% had more than 10 HU difference and 5% had more than 20 HU difference between true and virtual unenhanced images. CONCLUSION rsDECT-based virtual unenhanced images do not seem to be an ideal surrogate for true unenhanced images.