Thoracic Radiology
Core framework
Thoracic questions cover the ICU chest, pulmonary embolism, interstitial lung disease, and lung cancer screening. Know the silhouette sign, air bronchograms, and the difference between alveolar and interstitial patterns. In the ICU, recognize pulmonary edema (cephalization, Kerley B lines, perihilar bat-wing opacities), ARDS (bilateral opacities without cardiogenic cause), and pneumonia.
PE and vascular
CT pulmonary angiography is the test of choice; filling defects in contrast-opacified arteries confirm PE. Right heart strain signs (RV/LV ratio >1, septal bowing, reflux of contrast into the IVC) predict worse outcomes. Chronic PE shows webs, bands, and mosaic attenuation. Aortic dissection is discussed in the cardiovascular domain but also appears here.
Interstitial disease
UIP/IPF: peripheral, lower-lobe, subpleural reticulation with honeycombing and traction bronchiectasis, minimal ground-glass. NSIP: predominant ground-glass with fine reticulation. Hypersensitivity pneumonitis: centrilobular nodules, air trapping, mid-to-upper lung. Sarcoidosis: perilymphatic nodules and bilateral hilar lymphadenopathy. Always assess for the "does it fit a pattern" question rather than a single finding.
Screening and staging
Lung-RADS: category 3 (probably benign, 6-month follow-up), 4A/4B (suspicious, further workup), 4X (additional suspicious features). Lung cancer staging uses TNM; T stage depends on size and invasion. Mediastinal compartments help localize masses: anterior (thymoma, teratoma, thyroid, lymphoma), middle (lymphadenopathy, bronchogenic cyst), posterior (neurogenic tumors).
Traps and rule of thumb
Traps: calling honeycombing "ground-glass"; missing a small pneumothorax on a supine film (deep sulcus sign); attributing air bronchograms to interstitial disease.
Rule of thumb: "honeycombing plus traction bronchiectasis at the bases equals UIP" - a diagnosis of exclusion made only after excluding known causes.