"Ground-Glass Opacity-Ground glass opacification is seen as increased opacification of lung without obscuration of the bronchial and vascular markings. GGO can represent partially filled alveoli, active inflammation, or fine fibrosis below the resolution of CT images"
Causes - Alveolar proteinosis, Adult respiratory distress syndrome, Acute interstitial pneumonitis, Bronchiolitis obliterans oganizing pneumonia (BOOP),Desquamtive interstitial pneumonitis etc
AJR 2005; Miller WT, Shah RM. Isolated diffuse ground-glass opacity in thoracic CT: causes and clinical presentations. 184: 613-622