AJR. American journal of roentgenology
-
AJR Am J Roentgenol · Oct 1993
Cause of regional ventilation-perfusion mismatching in patients with idiopathic pulmonary fibrosis: a combined CT and scintigraphic study.
Regional ventilation and perfusion were studied in patients with idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) to seek an explanation for the mismatched ventilation/perfusion (V/Q) seen on scintigrams, which may suggest pulmonary embolic disease. ⋯ The cystic air spaces that are often seen on CT scans of patients with idiopathic pulmonary fibrosis are unperfused (probably due to vascular obliteration) but are usually normally ventilated. This V/Q mismatch on scintigrams explains the large physiologic dead space seen at rest and on exercise and could suggest pulmonary embolism unless a CT scan is obtained. Conversely, the larger cystic spaces might be mistaken for emphysema unless V/Q scintigraphy is done.
-
AJR Am J Roentgenol · Oct 1993
Differences in CT density between dependent and nondependent portions of the lung: influence of lung volume.
Lung tissue, blood, and air determine the physical density of the lung and hence the attenuation measured on CT scans. These components are not homogeneously distributed throughout the lungs, and their relative proportion changes continuously during respiration. The objective of this study was to measure densities in various areas of the normal lung with CT and to examine the influences of gravity and of the degree of lung inflation on these densities. ⋯ Changes in lung volume have different effects on changes in lung density in dependent and nondependent parts of the lung. The largest changes in lung density occur in the dependent regions. The difference in density between dependent and nondependent lung regions is smallest for lung volumes near total lung capacity. These findings may be useful as a baseline for interpreting CT measurements of regional lung density in suspected cases of lung disease, which would alter the physical density of lung tissue. Our results also suggest that measurements near total lung capacity should be included.