Comparison of the CO-RADS and the RSNA chest CT classification system concerning sensitivity and reliability for the diagnosis of COVID-19 pneumonia

Insights into Imaging

Table 2 RSNA chest CT classification system related to COVID-19

RSNA category	CT findings
Typical appearance	Peripheral, bilateral ground-glass opacities (GGO) ± consolidation or visible intralobular lines “crazy paving”
	Multifocal rounded GGO ± consolidation or visible intralobular lines “crazy paving”
	Reverse halo sign
Indeterminate appearance	Absence of typical CT findings and the presence of:
	Multifocal, diffuse, perihilar, or unilateral GGO ± rounded or non-peripheral consolidation
	Few very small GGO with a non-rounded and non-peripheral distribution
Atypical appearance	Absence of above features and the presence of:
	Isolated lobar or segmental consolidation without GGO
	Discrete small nodules e.g. tree-in-bud
	Lung cavitation
	Smooth interlobular septal thickening with pleural effusion
Negative for pneumonia	No GGO and consolidation

RSNA radiological Society of North America, CT computed tomography, COVID-19 coronavirus disease 2019, GGO ground-glass opacities