Objective To retrospectively determine the features of stones and calcifications in hepatobiliary system on virtual nonenhanced (VNE) dual-energy computed tomography (CT)

and to evaluate the possibility of VNE images in diagnosis for those lesions.Methods A total of 128 gall stones and calcifications of the liver found in 110 patients were examined with triple phase abdominal CT scan from July 2007 to December 2011

in which true nonenhanced (TNE) phase and arterial phase were performed with single-energy CT (120 kVp) and portal venous phase was performed with dual-energy CT (100 kVp and 140 kVp). VNE images were generated from the portal venous phase dual-energy CT data sets by using commercially VNC software. The mean CT values for the stone

liver

bile and paraspinal muscle

mean lesion density and size in area dimension

contrast-to-noise ratio (CNR) of lesion to the liver or bile

and image noise were assessed and compared between VNE and TNE images. The effective dose and size-specific dose estimate (SSDE) were also calculated.Results The mean CT values of the lesions measured on VNE images declined significantly compared with those measured on TNE images (164.51±102.13 290.72±197.80 HU

<0.001)

so did the lesion-to-liver CNR (10.80±11.82 18.81±17.06

<0.001) and the lesion-to-bile CNR (17.24±14.41 21.32±17.31

<0.001). There was no significant difference in size of lesions area between VNE and TNE images (0.69±0.88 0.72±0.85 cm

=0.062). Compared to the 128 lesions found in TNE images

VNE images showed the same density in 30 (23.4%) lesions

lighter density in 88 (68.8%) lesions

while failed to show 10 (7.8%) lesions

and showed the same size in 61 (47.7%) lesions and smaller size in 57 (44.5%) lesions. The CT cutoff values of lesion and size were 229.21 HU and 0.15 cm

respectively. The total effective dose for triple phase scan protocol with TNE images was 19.51±7.03 mSv

and the SSDE was 39.84±11.10 mGy. The effective dose for dual phase scan protocol with VNE images instead of TNE images was 13.29±4.89 mSv

and the SSDE was 27.83±9.99 mGy. Compared with TNE images

the effective dose and SSDE of VNE images were down by 32.05%±3.69 % and 30.63%±2.34 %

respectively.Conclusions Although the CT values and CNR of the lesions decreased in VNE images

the lesions of which attenuation greater than 229.21 HU and size larger than 0.15 cmcould be detected with good reliability and obvious dose reduction. There was good consistency in the size of stones and calcifications in hepatobiliary system between VNE images and TNE images

which ensured the possibility of the clinical application of VNE images.