Plaque burden assessment and attenuation measurement of carotid atherosclerotic plaque using virtual monoenergetic images in comparison to conventional polyenergetic images from dual-layer spectral detector CT

To compare virtual monoenergetic images (VMIs) with conventional polyenergetic images (PI) of Dual-layer spectral detector CT angiography (DLCTA) in plaque burden assessment and attenuation measurement of carotid atherosclerotic plaques. Supra-aortic DLCTA imaging of thirty patients (8 female, mean ages 63.1 ± 7.5 years) were respectively reviewed. Lumen area, wall area, and calcified area of plaques were outlined and recorded. Normalized wall index (NWI) was calculated for plaque burden and compared between PI and different VMIs. The attenuation of the non-calcified, calcified area of the plaques, sternocleidomastoid muscle (SCM), as well as Z effective values were measured and compared. Fifty carotid plaques (27 left, 23 right) of thirty patients were analyzed. The average values of lumen, wall, calcified areas and NWI on PI were 34.50 ± 20.57mm2, 47.61 ± 19.94 mm2, 5.25 mm2 (1.35- 51.86 mm2), and 0.59 ± 0.16 respectively. No significant difference was found in the lumen area (p = 0.314), wall area (p = 0.600), and NWI (p = 0.980) between different VMIs and PI. A significant difference was found in the calcified area between VMIs and PI (p = 0.009). Attenuations of non-calcified and calcified components in carotid plaques were comparable to PI for 50−120 keV (all: p > 0.05) and 60−120 keVs (all p > 0.05), respectively. Z Effective values for non-calcified, calcified and SCM were 7.67 ± 0.42, 11.70 ± 1.22, and 7.45 ± 0.12, respectively. Carotid plaque burden assessment was comparable between PI and VMIs at 40−120 keVs. Attenuations of non-calcified components in carotid plaques were comparable to PI for 50−120 keV VMIs of DLCTA. VMIs might provide more information on carotid plaque features.