Pulmonary kinematic analysis with non-rigid deformable registration for detecting localised emphysema

Emphysema is defined pathologically as destruction of alveolar walls and permanent enlargement of the airspaces. Detection of localised emphysema is difficult using conventional methods because the parameters evaluate macroscopic lung function. In this study, the pulmonary kinematics of control and emphysema model mice were evaluated to investigate whether pulmonary kinematic analysis is useful for diagnosing localised emphysema. Emphysema model mice were induced by porcine pancreatic elastase treatment, and 3D micro-CT images were obtained during stepwise inflation and deflation. The pulmonary vessels and pleura were segmented at each pressure, and pulmonary deformation and volumetric strain between consecutive different pressures were calculated by non-rigid deformable registration. In particular, during low lung pressure, craniocaudal deformation and volumetric strain were higher in the regions where the alveolar enlargement was observed in emphysema model mice. Furthermore, volumetric strain of emphysema model mice was larger at alveolar enlargement. On the other hand, there were no significant differences between control and emphysema model mice in conventional macroscopic lung pressures and volume relationships. The present results indicate that pulmonary kinematic analysis, examining craniocaudal deformation, and volumetric strain may become useful for the clinical assessment of localised emphysema.