Table 2.

Definitions of adverse plaque characteristics

HRP feature	Definition
Low attenuation plaque	Presence of a central area within the plaque characterized by low CT attenuation <30 HU.10
Positive remodelling or remodelling index (RI)	Presence of an outer vessel diameter which is >10% of the diameter of the reference normal segment within the same vessel (RI >1.1).10
Spotty calcification	Small focal calcifications <3 mm diameter in any direction.10
Napkin-ring sign	Central area of low CT attenuation that is apparently in contact with the lumen and is surrounded by a rim of higher attenuation.11

CT, computed tomography; HU, Hounsfield unit; RI, remodelling index.