Virtual non-contrast images from dual-energy CT angiography of the abdominal aorta and femoral arteries: comparison with true non-contrast CT images.

Abstract

To assess whether virtual non-contrast (VNC) computed tomography (CT) images acquired from dual-energy CT (DECT) have sufficient image quality to replace true non-contrast (TNC) CT images in CT angiography (CTAG). This study enrolled 63 consecutive patients who underwent a CTAG that included a single-energy non-contrast scan, followed by a post-contrast DECT scan. Comparison of attenuation and noise between TNC and VNC images was made by drawing circular regions of interest (ROI) on a picture archiving and communication system (PACS) workstation within the aortic lumen at the levels of the renal arteries, the aortic bifurcation and right femoral artery. Mean attenuation and image noise (one standard deviation) were registered in Hounsfield units (HU). The VNC images were subjectively evaluated for artifacts such as subtraction of calcifications or architectural distortion based on TNC image as a standard of reference. Most attenuations of the VNCs were higher than TNC, except right femoral artery of reader 2. Most image noises of TNC were higher than VNC, except abdominal aorta in reader 1. In qualitative image analysis, mean scores of VNC according to the 5-point scale were 3.68 and 3.63 (reader 1 and reader 2, respectively) which mean good to excellent to diagnose. HUs and VNC image noises are different from TNC images in CTAG. VNC images have sufficient image quality to replace TNC images in the diagnosis of calcific lesions. VNC images acquired from DECT have image quality adequate to replace TNC images in the diagnosis of the calcific lesion on the CTAG. VNC images based on DECT can avoid excessive and unnecessary patient exposure to radiation during CTAG.