| Silhouette | lost interface | contact with a water‑density structure (localisation) |
| Air bronchogram | air‑filled bronchi in opaque lung | airspace disease |
| Golden S (S sign of Golden) | reverse‑S minor fissure | RUL collapse + central mass |
| Luftsichel | periaortic lucent crescent | LUL collapse |
| Flat waist | flattened aortic knuckle/PA | LLL collapse |
| Juxtaphrenic peak | peak on the hemidiaphragm | upper lobe collapse |
| Deep sulcus | deep lucent CP angle on supine film | pneumothorax |
| Continuous diaphragm | air under the heart | pneumomediastinum |
| Naclerio V | left para‑aortic/supradiaphragmatic gas | oesophageal rupture |
| Spinnaker sail / angel wing | thymus lifted by air | neonatal pneumomediastinum |
| Split pleura | separated enhancing pleura | empyema |
| Meniscus | curved fluid margin | pleural effusion |
| Hampton's hump / Westermark / Fleischner / Palla / polo mint | infarct / oligaemia / enlarged PA / enlarged right descending PA / central filling defect | pulmonary embolism |
| Monod / air crescent / halo | mobile fungus ball / crescent in recovering angioinvasive / haemorrhagic halo | aspergilloma / angioinvasive aspergillosis |
| Finger‑in‑glove | mucoid impaction | ABPA (also bronchial atresia) |
| Signet ring / bunch of grapes / tram‑track | dilated bronchus > artery / cystic bronchiectasis / parallel walls | bronchiectasis |
| Tree‑in‑bud | centrilobular branching nodules | infective bronchiolitis (active TB) |
| Crazy paving | GGO + septal thickening | PAP (also PCP, haemorrhage) |
| Reversed halo (atoll) | central GGO, peripheral ring | organising pneumonia, mucormycosis, TB |
| CT angiogram | vessels visible in low‑density consolidation | invasive mucinous adenocarcinoma, lymphoma |
| Holly leaf / incomplete border | calcified plaque en face | asbestos‑related pleural disease |
| Hilum overlay / cervicothoracic / thoracoabdominal | localisation signs | mediastinal masses |
| Bat wing / Kerley B / cephalisation | perihilar oedema / septal lines / upper lobe diversion | pulmonary venous hypertension |
| Water bottle / boot / egg on string / snowman / box / figure 3 | cardiac silhouettes | pericardial effusion / TOF / TGA / TAPVC / Ebstein's / coarctation |
| Steeple / thumb | subglottic narrowing / swollen epiglottis | croup / epiglottitis |
| Sail (thymic) | triangular thymic lobe | normal infant thymus |