Miliary Pattern

The dense shadows in the miliary pattern measure about 1 to 3 mm in size and are discrete. Early miliary pattern may be missed in conventional radiology and CT may be necessary in order to diagnose. The miliary patterns are produced classically in miliary tuberculosis, tropical eosinophilia, miliary carcinoma­tosis, hemosiderosis and occupational disorders such as silicosis, bagassosis, etc.

Nodular Pattern

When the densities are more than 5 mm but less than 1 cm, these are generally termed as nodular densities. These are well circumscribed and distributed in both lungs. The etiology for this nodular pattern includes septic emboli, tuberculosis and hematogenous meta­stasis.

Coin Shadows

The term coin shadow comes from the shape and size of the density in the PA view of the chest. These coin shadows in reality have three dimensions and hence should be called "Marble shadows". These could be single or multiple. When multiple, these are due to septic emboli, multiple tuberculomata, fluid-filled cysts, infected bronchiectatic lesions, adenocarcinoma of the lung and metastasis.

Parenchymal Masses

Any opacity in the lung measuring more than 3 cm is described as a mass. It is important to be sure by conventional radiographs whether the mass is located in the lung parenchyma, pleura or extrapleural in origin such as arising from the rib, intercostal nerve, mediastinum, etc. In general, parenchymal mass is outlined both in PA and lateral views of the chest, whereas with pleural or extrapleural mass, one of the borders will not be outlined, as it silhouettes with pleura.

Cavitary Pattern

Cavitation occurs in abscess, tuberculosis, fungal granuloma, infarcts, ruptured hydatid cyst, end stage disease of sarcoidosis, primary malignancies and metastasis.

Cavity in the lung may contain air, pus, hemor­rhage or a fungus ball. The common cause of cavity in the lung particularly in the upper lobes is tuber­culosis. Tuberculous cavities in general are thin walled and air containing.

Infiltrates

Alveolar infiltrate is homogeneous, patchy, segmental or lobar, and generally has an air bronchogram effect. These alveolar infiltrates are generally observed in bacterial pneumonias. These shadows are also called consolida­tions and generally involve a single lobe or segment of the lung, whereas

Interstitial infiltrates are gene­rally linear, streaky, bilateral and nonsegmental. The classical interstitial infiltrates are often noted in viral and mycoplasma pneumonias. In pulmo­nary edema, independent of the etiology, the pattern starts with interstitial process.

The mixed patterns are noted in bronchopneumo­nias, malignancy and other miscellaneous conditions.

Date: 2014-12-28; view: 1089