Single-Acquisition Dual-Energy Multidetector Computed Tomography: Analysis of Vascular Enhancement and Postprocessing Techniques for Evaluating the Thoracic Aorta

Purpose: The objectives of this study were (1) to evaluate the potential of low-peak kilovoltage (kVp) images acquired with dual-energy computed tomography (DECT) to improve aortic attenuation and reduce contrast agent utilization and (2) to evaluate the feasibility of material-specific DECT imaging for evaluating aortic disease. Materials and Methods: Aortic imaging characteristics of 2 groups of patients examined with DECT were compared. In the first group, CT angiography (CTA) was performed in patients with known or suspected aortic disease (CTA group: n = 20, 100-150 mL of contrast at 4.5 mL/s). In the second group, reduced contrast volume CTA was performed in patients with "routine" indications (RC group: n = 20, 50-60 mL at 3 mL/s followed by a saline chaser). In both groups, aortic attenuation and SD were measured at 80 and 140 kVp, and the image quality was analyzed using a 5-point scale. The use of DECT post-processing techniques for assessing aortic pathology was also evaluated. Results: For all patients, the aortic attenuation was significantly higher at 80 kVp than at 140 kVp (P < 0.001). Image noise measured quantitatively was higher at 80 kVp (P G 0.001) but did not affect the perceived image quality (P = 0.3). Using low-peak kilovoltage allowed aortic CTA to be performed with a markedly reduced contrast volume and flow rate, with image quality similar to standard CTA (P = 0.2). In a series of cases with proved aortic disease, comparison of true precontrast and subtraction "virtual noncontrast" images showed the potential to eliminate aortic precontrast imaging, reducing radiation exposure. Conclusions: Single-acquisition DECT combines (1) the benefits of low-kVp vascular imaging (increased iodine conspicuity coupled with a contrast volume/rate reduction) and (2) the use of material-specific imaging techniques to uniquely characterize the aortic pathology.