Computed Tomography Studies of Lung Mechanics

Abstract

The study of lung mechanics has progressed from global descriptions of lung pressure and volume relationships to the highresolution, three-dimensional, quantitative measurement of dynamic regional mechanical properties and displacements. X-ray computed tomography (CT) imaging is ideally suited to the study of regional lung mechanics in intact subjects because of its high spatial and temporal resolution, correlation of functional data with anatomic detail, increasing volumetric data acquisition, and the unique relationship between CT density and lung air content. This review presents an overview of CT measurement principles and limitations for the study of regional mechanics, reviews some of the early work that set the stage for modern imaging approaches and impacted the understanding and management of patients with acute lung injury, and presents evolving novel approaches for the analysis and application of dynamic volumetric lung image data. Keywords: computed tomography; mathematical modeling; physiologyThe phenomena covered by the word "respiration" are very diverse. When a person is seen to breathe, what is observed is a movement of the chest and abdomen by which air is alternately drawn into his lungs and again expelled. This constitutes the mechanical aspect of respiration.-August Krogh, 1941 In the 60-odd years since A. Krogh (1) opened his treatise on the comparative physiology of respiration with these words, an enormous amount of work has explored the relationship between lung expansion or deformation and the forces that drive such changes. Most recently, advances in imaging techniques have extended the study of lung mechanical behavior to the regional level, and currently evolving technologies permit the threedimensional characterization of dynamic lung volume changes in intact subjects. X-ray computed tomography (CT), because of its speed, widespread availability, high-resolution anatomic visualization, and unique ability to quantify regional air and tissue volumes, provides a particularly powerful tool for the noninvasive measurement of lung mechanics in experimental models as well as human subjects. This review presents relevant CT measurement principles for regional mechanics, presents examples of static and dynamic approaches to lung mechanics, and emphasizes some exciting and promising new high-resolution, vol-

Tensor grid based image registration with application to ventilation estimation on 4D CT lung data

“…Assuming that the ventilation and the change in volume within the lungs are correlated, the Jacobian metric gives a physiologically meaningful estimate of the ventilation. Furthermore, the metric is Several research groups [9,23] have found a good global agreement of the known volume change of the entire lung with the volume change computed with the Jacobian analysis as well as a good local correlation to Xenon-CT [11], supporting our decision to favor this metric for the ventilation assessment.…”

Computed Tomography Measurement of Rib Cage Morphometry in Emphysema

“…Besides anthropometric factors, several lung diseases are independent determinants of the rib cage variability [5], [10], [11], [12], [13], [14]. Notably, chronic obstructive pulmonary disease (COPD) is a multi-compartmental disease which may cause hyperinflation of the lungs and musculoskeletal abnormalities [10], [11], [15], [16], [17].…”

Volumetric Xenon-CT Imaging of Conventional and High-frequency Oscillatory Ventilation1

“…Functional lung imaging with X-ray computed tomography (CT) facilitates the study of pulmonary structure-function relationships by providing both detailed anatomic information as well as co-localized physiologic information (1,2). As the speed and volumetric coverage of multi-detector CT (MDCT) scanners has increased over time, so has the ability to rapidly and efficiently characterize variation in regional lung function across the entire lung.…”