Radiological Society of North America chest CT classification system for reporting COVID-19 pneumonia (adapted from reference 15)
| COVID-19 Pneumonia Imaging Classification | Rationale | CT Findings |
|---|---|---|
| Typical appearance | Commonly reported imaging features of greater specificity for COVID-19 pneumonia | Peripheral, bilateral GGOs with or without consolidation or visible intralobular lines (“crazy-paving”) Multifocal GGOs of rounded morphology with or without consolidation or visible intralobular lines (crazy-paving) Reverse halo sign or other findings of organizing pneumonia (seen later in the disease) |
| Indeterminate appearance | Nonspecific imaging features of COVID-19 pneumonia | Absence of typical features AND Presence of: Multifocal, diffuse, perihilar, or unilateral GGO with or without consolidation lacking a specific distribution and are non-rounded or non-peripheral Few very small GGO with a non-rounded and non-peripheral distribution |
| Atypical appearance | Uncommonly or not reported features of COVID-19 pneumonia | Absence of typical or indeterminate features AND Presence of: Isolated lobar or segmental consolidation without GGO Discrete small nodules (centrilobular, “tree-in-bud”) Lung cavitation Smooth interlobular septal thickening with pleural effusion |
| Negative for pneumonia | No features of pneumonia | No CT features to suggest pneumonia |
Note:—GGOs indicates ground-glass opacities