Miliary PatternThe 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: 1143
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