Assessment of Lung Biomechanics in COPD Using Image Registration

Lung biomechanical properties can be used to detect disease, assess abnormal lung function, and track disease progression. In this work, we used computed tomography (CT) imaging to measure three biomechanical properties in the lungs of subjects with varying degrees of chronic obstructive pulmonary disease (COPD): the Jacobian determinant (J), a measure of volumetric expansion or contraction; the anisotropic deformation index (ADI), a measure of the magnitude of anisotropic deformation; and the the slab-rod index (SRI), a measure of the nature of anisotropy (i.e., whether the volume is deformed to a rod-like or slab-like shape). We analyzed CT data from 247 subjects collected as part of the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS). The results show that mean J and mean ADI decrease as disease severity increases, indicating less volumetric expansion and more isotropic expansion with increased disease. No differences in average SRI index were observed across the different levels of disease. The methods and analysis described in this study may provide new insights into our understanding of the biomechanical behavior of the lung for COPD patients with various Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages.