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

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

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