General pulmonary overinflation small peripheral vessels normal or enlarged hilar pulmonary arteries. This combination results from various causes of pulmonary artery hypertension (pulmonary artery stenosis, widespread embolic disease to small arteries, pulmonary arteritis, primary pulmonary hypertension, etc.).ģ. Small peripheral vessels no overinflation enlarged hilar pulmonary arteries. This combination is indicative of a reduction in pulmonary blood flow and is pathognomonic of usually cyanotic congenital cardiac anomalies with a right to left shunt (tetralogy of Fallot with pulmonary atresia, persistent truncus arteriosus Type IV, Ebstein’s anomaly) or of isolated pulmonic stenosis without poststenotic dilatation.Ģ. Small peripheral vessels, no overinflation small hila. Four combinations of these changes are possible:ġ. ![]() An apparent bilateral decrease of pulmonary density may be caused by three factors or combinations thereof: (1) reduction of the caliber of peripheral pulmonary vessels (2) reduction of the size of pulmonary hila and (3) generalized pulmonary overinflation. CT is able to detect bilateral pulmonary hyperlucency earlier, when plain films are still apparently normal. The sensitivity of the assessment of bilateral changes in lung density with roentgenograms is limited due to technical variables, variations in the amount of extrathoracic soft tissue, and observer error. A decrease of lung density manifests as increased darkening on the chest radiograph. The increase in the amount of contained gas decreases the lung density. ![]() The density of lung parenchyma increases with the increasing amount of capillary blood and interstitial tissue or fluid. This allows visualization of blood vessels in the lungs without using contrast medium. The major blood vessels have a density of 1.0 g/ml, whereas the density of lung parenchyma at total capacity is only 0.08 g/ml. ![]() The roentgenographic density of the lungs is determined by the absorption of roentgen rays by gas, blood, and tissue.
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