Table 1. HRCT findings in idiopathic pulmonary fibrosis (in relation to the usual interstitial pneumonia pattern).

	UIP	Probable UIP	Indeterminate for UIP	Alternative Diagnosis
Distribution	• Subpleural inferior predominance • Might be asymmetrical and heterogeneous	• Subpleural inferior predominance • Frequently heterogeneous	• Diffuse (without subpleural predominance)	• Peribronchovascular • Perilymphatic • Upper or mid lung • Subpleural sparing
HRCT characteristics	• Honeycombing (with or without traction bronchiectasis) • Irregular thickening of interlobular septa • Superimposed to reticular pattern • Mild GGO • Might have pulmonary ossification	• Reticular pattern with traction bronchiectasis • May have mild GGO (usually near areas of bronchiectasis) • Absence of subpleural sparing	• HRCT features of lung fibrosis that do not suggest any diagnosis	• Lung findings: • Cysts • Mosaic attenuation • GGO predominance (might be found if diagnosed during an AE-IFP) • Centrilobular micronodules • Nodules • Consolidations • Mediastinal findings: • Pleural plaques • Dilated esophagus

Based on Raghu et al. ^{3 )} UIP: usual interstitial pneumonia; GGO: ground-glass opacities; and AE-IPF: acute exacerbation of idiopathic pulmonary fibrosis.