Spectral Signal Density of Carotid Plaque Using Dual-Energy Computed Tomography

BACKGROUND AND PURPOSE: Plaque characterization using virtual monochromatic imaging derived from dual-energy computed tomography (CT) angiography requires the determination of normal signal density values of each plaque component. We sought to explore the signal density values of carotid plaque components using dual-energy compared to conventional single-energy CT angiography (CTA), and to establish the energy level with the largest differences between plaque components. METHODS: The present prospective study involved consecutive patients referred for carotid artery evaluation by CTA. Two scans (single-energy and dual-energy CTA) were performed in all patients, and a single radiologist analyzed the data. Single-source dual-energy CTA allowed the generation of virtual monochromatic images from 40 to 140 keV. RESULTS: A total of 35 internal carotid artery lesions were examined in 20 symptomatic patients. The mean age was 72.3 +/- 6.7 years, and 9 (45%) patients were male. Internal carotid artery geometrical variables including lumen area (P =.96), vessel area (P =.97), and percent area stenosis (P =.99) did not differ between groups (single-energy CTA, and dual-energy CTA at 40, 70, 100, and 140 keV). Differences between signal densities of different tissues were largest at 40 keV (calcium/lumen, P <.0001; fat/noncalcified, P <.0001). CONCLUSIONS: In the present pilot investigation, virtual monochromatic imaging at low-energy levels derived from dualenergy CTA allowed the largest differences in attenuation levels between tissues, without affecting vessel or plaque geometry.