Pericoronary adipose tissue attenuation assessed by dual-layer spectral detector computed tomography is a sensitive imaging marker of high-risk plaques

Background: The pericoronary fat attenuation index (FAI) derived from conventional polychromatic computed tomography (CT) can capture the presence of coronary inflammation. However, conventional polychromatic CT has limitations in material component differentiation, and spectral CT could have a better ability to discriminate tissue characteristics. Hence, this study sought to assess pericoronary adipose tissue (PCAT) attenuation using spectral CT and explore its association with atherosclerotic plaque characteristics. Methods: We enrolled 104 patients with coronary atherosclerosis who met the inclusion criteria and underwent coronary CT angiography with dual-layer spectral detector computed tomography (SDCT). Plaque anatomical characteristics were measured, and the PCAT attenuation was assessed by polychromatic images (CTpoly), virtual mono-energetic images at 40 keV (CT40 keV), the slope of spectral attenuation curve (lambda(HU)), and the effective atomic number (Z(eff)). The association of PCAT attenuation indicators with the presence of high-risk plaques was analyzed, along with the indicators' ability to identify high-risk plaques. Results: PCAT attenuation indicators around high-risk plaques were higher than those around non-high-risk plaques, especially CT40 keV [-153.76 +/- 24.97 (non-high-risk plaque) vs. -119.87 +/- 22.74 (high-risk plaque), P<0.001]. CT40 keV was a predictive factor of high-risk plaques, and high CT40 keV (>=-120.60 HU) could assist in the identification of high-risk plaques, with an area under the curve of 0.883 (95% CI: 0.83-0.94, P<0.05). Conclusions: PCAT surrounding high-risk plaques showed higher attenuation; a finding that has been associated with coronary artery inflammation. The metrics derived from SDCT, especially CT40 keV, showed higher discriminatory power for detecting changes in PCAT attenuation than polychromatic CT. PCAT attenuation assessed by CT40 keV may provide a novel imaging marker of plaque vulnerability.