Dual energy CT in patients with acute abdomen; is it possible for virtual non-enhanced images to replace true non-enhanced images?

This study aims to determine whether virtual non-enhanced images derived from dual-energy computed tomography (CT) can replace true non-enhanced images in patients with acute abdomen. Patients with acute abdomen (n = 202) underwent multidetector CT including non-enhanced and contrast-enhanced images obtained at the portal phase using the dual-energy technique. CT attenuation values were measured in abdominal organs. Image quality, noise, artifacts, and acceptability for virtual non-enhanced images compared to true non-enhanced images were rated. Mean sizes of clinically significant stones and mean attenuation values of intraabdominal hemorrhages were compared by means of five-point scales. Effective radiation doses were calculated. Mean CT attenuation values of virtual non-enhanced and true non-enhanced images were similar. Virtual non-enhanced images showed good image quality, mild noise, mild artifacts, and good acceptability compared to true non-enhanced images. A total of 71 clinically significant stones (11 appendicoliths, 33 gallbladder stones, 11 bile duct stones, and 16 urinary stones) and 15 intraabdominal hemorrhages were included in the study. Small stones were detected better on true non-enhanced images than on virtual non-enhanced images. Hemorrhage was similarly detected on both virtual non-enhanced and true non-enhanced images. Mean radiation dose reductions by omitting true non-enhanced images were 33 % in the virtual triple protocol and 47 % in the virtual dual protocol. Image qualities of virtual non-enhanced images are comparable to those of true non-enhanced images. Small stones can be obscured on virtual non-enhanced images. Therefore, tailored application of dual-energy CT is needed for evaluation of patients with acute abdomen.