American Journal of Roentgenology, Vol 161, 713-717, Copyright © 1993 by American Roentgen Ray Society

ARTICLES

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

JA Verschakelen, L Van fraeyenhoven, G Laureys, M Demedts and AL Baert
Department of Radiology, University Hospitals, K. U. Leuven, Belgium.

OBJECTIVE. 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. SUBJECTS AND METHODS. The subjects in the study were six healthy male volunteers. CT scans were obtained at the level of the aortic arch and 2 cm above the expiratory level of the diaphragm with the subjects supine and then with them prone. Scans were obtained at lung volumes of 10%, 50%, and 90% vital capacity by using a respiratory gating device connected to the CT scanner. The overall density of the lungs at these two levels and the densities in the dependent (posterior in supine, and anterior in prone body position) and nondependent (anterior in supine and posterior in prone body position) areas were measured by using a semiautomatic evaluation algorithm. RESULTS. Changes in lung volume caused the same changes in lung density in the right and left lungs and in the upper and lower parts of the lungs. For both body positions (supine and prone), the difference between lung density at 10% vital capacity and that at 90% vital capacity was significantly larger (p < .05) in the dependent parts of the lung than in the nondependent parts. In both positions, differences in density between dependent and nondependent regions were significantly (p < .05) greater at 10% vital capacity than at 90% vital capacity, and the differences became small when the volume of the lung was near total lung capacity. CONCLUSION. 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.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				J. Appelberg, T. Pavlenko, H. Bergman, H. U. Rothen, and G. Hedenstierna Lung Aeration During Sleep Chest, January 1, 2007; 131(1): 122 - 129. [Abstract] [Full Text] [PDF]

				I. Orlandi, C. Moroni, G. Camiciottoli, M. Bartolucci, M. Pistolesi, N. Villari, and M. Mascalchi Chronic Obstructive Pulmonary Disease: Thin-Section CT Measurement of Airway Wall Thickness and Lung Attenuation Radiology, February 1, 2005; 234(2): 604 - 610. [Abstract] [Full Text] [PDF]

				S. P. G. Padley, S. J. Jordan, P. Goldstraw, A. U. Wells, and D. M. Hansell Asymmetric ARDS Following Pulmonary Resection: CT Findings—Initial Observations Radiology, March 21, 2002; (2002) 2232010721. [Abstract] [Full Text]

				M. J. Rodriguez-Nieto, G. Peces-Barba, N. Gonzalez Mangado, M. Paiva, and S. Verbanck Similar ventilation distribution in normal subjects prone and supine during tidal breathing J Appl Physiol, February 1, 2002; 92(2): 622 - 626. [Abstract] [Full Text] [PDF]

				I. Amirav, S. S. Kramer, and M. M. Grunstein Methacholine-Induced Temporal Changes in Airway Geometry and Lung Density by CT Chest, June 1, 2001; 119(6): 1878 - 1885. [Abstract] [Full Text] [PDF]

				P. Scillia, S. A. Kafi, C. Melot, C. Keyzer, R. Naeije, and P. A. Gevenois Oleic Acid-induced Lung Injury: Thin-Section CT Evaluation in Dogs Radiology, June 1, 2001; 219(3): 724 - 731. [Abstract] [Full Text] [PDF]

				K. W. Lee, S. Y. Chung, I. Yang, Y. Lee, E. Y. Ko, and M. J. Park Correlation of Aging and Smoking with Air Trapping at Thin-Section CT of the Lung in Asymptomatic Subjects Radiology, March 1, 2000; 214(3): 831 - 836. [Abstract] [Full Text]

				C. Guckel, A. U. Wells, D. A. Taylor, F. Chabat, and D. M. Hansell Mechanism of mosaic attenuation of the lungs on computed tomography in induced bronchospasm J Appl Physiol, February 1, 1999; 86(2): 701 - 708. [Abstract] [Full Text] [PDF]

				S. P. G. Padley, S. J. Jordan, P. Goldstraw, A. U. Wells, and D. M. Hansell Asymmetric ARDS Following Pulmonary Resection: CT Findings—Initial Observations Radiology, May 1, 2002; 223(2): 468 - 473. [Abstract] [Full Text] [PDF]