Biomechanical Determinants of Emphysema Progression

Emphysema is characterized by a loss of tissue structure and an enlargement of contiguous air spaces in the lungs.  These destructive phenomena are associated with the redistribution of stresses in the remaining tissue structure, which can lead to progressively worsening patient condition.  The goals of this project were to characterize the changes in lung structure during the course of emphysema progression using computed tomographic (CT) images, and predict the disease progression using a computational model of force-based rupture.

Low-attenuation areas (LAAs) in a CT image, scanning from apex to base (i.e., head to toe direction).  Each cluster is colored to emphasize distinct connected components in each two-dimensional slice.  The distribution of LAA cluster sizes is described by a power-law, with many small clusters and few very large clusters.

The so-called “super cluster” consists of only one contiguous low-attenuation region (dark), formed by the aggregation of multiple smaller clusters throughout the course of emphysema progression.  Many much smaller clusters are not shown in this image.  The super cluster is unique: it is an outlier to the typical power-law distribution of cluster sizes.  The formation of a super cluster likely indicates the end-stage of tissue structure loss in emphysema.