Figure 15:

High-risk plaque (HRP) features on coronary CTA. (A) Spotty calcium, defined as punctate calcium within a plaque (B) “napkin ring sign,” defined in a non-calcified plaque cross-sectional image by the presence of two features: a central area of low attenuation plaque that is apparently in contact with the lumen; and a ring-like peripheral rim of higher CT attenuation surrounding this central area (arrows); (C) Positive remodeling, defined as the ratio of outer vessel diameter at the site of plaque divided by the average outer diameter of the proximal and distal vessel greater than 1.1, or Av/[(Ap + Ad)/2] >1.1; and (D) Low attenuation plaque, defined as non-calcified plaque with internal attenuation less than 30 HU. Please note that a combination of two or more high-risk features is necessary to designate the plaque as high-risk for CAD-RADS.