Variation of degree of stenosis quantification using different energy level with dual energy CT scanner

Purpose: To investigate the variation in the quantification of the carotid degree of stenosis (DoS) with a dual energy computed tomography (CT), using different energy levels during the image reconstruction. Methods: In this retrospective study, 53 subjects (37 males; mean age 67 ± 11 years; age range 47–83 years) studied with a multi-energy CT scanner were included. Datasets were reconstructed on a dedicated workstation and from the CT raw data multiple datasets were generated at the following monochromatic energy levels: 66, 70, 77, and 86 kilo-electronvolt (keV). Two radiologists independently performed all measurements for quantification of the degree of stenosis. Wilcoxon test was used to test the differences between the Hounsifield unit (HU) values in the plaques at different keV. Results: The Wilcoxon analysis showed a statistically significant difference (p = 0.001) in the DoS assessment among the different keVs selected. The Bland-Altman analysis showed that the DoS difference had a linear relation with the keV difference (the bigger is the difference in keV, the bigger is the variation in DoS) and that for different keVs, the difference in DoS is reduced with its increase. Conclusion: A standardization in the use of the energy level during the image reconstruction should be considered.