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 (CT poly ), virtual mono-energetic images at 40 keV (CT 40 keV ), the slope of spectral attenuation curve (λ 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 nonhigh-risk plaques, especially CT 40 keV [−153.76±24.97 (non-high-risk plaque) vs. −119.87±22.74 (high-risk plaque), P<0.001]. CT 40 keV was a predictive factor of high-risk plaques, and high CT 40 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 CT 40 keV may provide a novel imaging marker of plaque vulnerability.

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Display speed is one of the important factors in NC simulation system. It is very difficult to meet the requirement of the continuous animation by full-redraw mechanism. An algorithm for part-redraw mechanism, based on OpenGL stencil buffer and the display area defined twice, is delivered. When the algorithm is put into use in NC simulation system, the top surface of the workpiece can be represented as a set of triangle grids, especially, the number of the triangle grids exceeds millions of magnitude, the display speed is increased from (2.109±0.10)f/s to (57.826±1.00)f/s.