Evaluation of different keV-settings in dual-energy CT angiography of the aorta using advanced image-based virtual monoenergetic imaging.

To compare quantitative image quality in dual-energy CT angiography (DE-CTA) studies of the aorta using different virtual monoenergetic imaging (MEI) and advanced image-based virtual monoenergetic (MEI+) settings at varying kiloelectron volt (keV) levels. Fifty consecutive patients with clinically-indicated CT of the whole aorta to evaluate suspected aortic disease underwent DE-CTA on a third-generation dual-source CT scanner. Quantitative image quality indices were assessed. Contrast material, saline flush and flow rate were kept equal for optimum comparability. DE-CTA MEI and MEI+ series ranging from 40 to 100 keV (10-keV intervals) were reconstructed. Signal intensity, noise, signal-to-noise ratio and contrast-to-noise ratio (CNR) of multiple aortic segments were evaluated. Comparisons between the different MEI and MEI+ datasets were performed. Three-hundred aortic segments total were evaluated. In the MEI+ series the 40, 50 and 100 keV MEI+ showed superior noise and CNR levels (+84, +58, +103 % on average; all p < 0.05) compared to MEI. However, signal intensity between MEI+ and MEI at nearly all aortic segments showed no significant difference (p > 0.1). MEI+ shows lower image noise compared to MEI, resulting in superior quantitative image quality, in particular at low keV levels (40 or 50 keV).