Differences in CT density between dependent and nondependent portions of the lung: influence of lung volume.

Abstract

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.