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

We aimed to evaluate whether virtual unenhanced images (VUI) generated from nephrographic phase on rapid kV-switching dual energy CT (rsDECT) can replace true unenhanced images (TUI) by comparing attenuation values of various intraabdominal structures.

In this retrospective study, 142 patients had unenhanced and nephrographic phase dual energy CT images. Attenuation values of the aorta, liver,spleen, pancreas, bilateral renal parenchyma, inferior vena cava, gallbladder and paraspinal muscle on TUI and VUI were recorded. Frequencies of organs who had more than 10 and 20 HU of attenuation difference were also calculated.

A total of 1224 ROIs were sampled. No statistically significant differences were found between TUA and VUA 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). 20% of organs had more than 10 HU difference and 5% had more than 20 HU difference between TUI and VUI.

rsDECT based VUI does not seem to be an ideal surrogate for TUI.