Three-dimensional characterization of regional lung deformation

Area of Science:

• Pulmonary Biomechanics
• Medical Imaging Analysis
• Quantitative Physiology

Background:

• Lung deformation during breathing is complex, with regional variations in volume change and orientation.
• Existing imaging and image registration techniques capture lung displacement but lack physiologically relevant interpretation methods.
• Quantifying lung deformation is crucial for understanding respiratory mechanics and disease progression.

Purpose of the Study:

• To develop and validate novel indices for interpreting lung deformation from displacement fields.
• To provide physiologically intuitive measures of lung volume change and directional deformation preferences.
• To assess the utility of these indices in human subjects using clinical imaging data.

Main Methods:

• Proposed three novel indices: Jacobian (volume change), anisotropic deformation index (magnitude of directional preference), and slab-rod index (nature of directional preference).
• Applied deformable image registration to static CT images from Functional Residual Capacity (FRC) to Total Lung Capacity (TLC) in six human subjects.
• Calculated and analyzed the proposed deformation indices across different lung regions and lobes.

Main Results:

• Volume change was elevated in the inferior-dorsal lung regions, consistent with supine breathing.
• Anisotropic deformation index was higher in the inferior lung (diaphragm proximity) and lobar fissures (tissue sliding).
• Lower lung lobes demonstrated significantly greater volume change and anisotropy than upper lobes across subjects.
• Lung vessels exhibited rod-like deformation compared to the whole lung.

Conclusions:

• The developed lung deformation indices offer a physiologically relevant interpretation of displacement fields derived from imaging or simulations.
• These indices reveal distinct regional patterns of lung deformation, highlighting differences between lower and upper lobes.
• The findings provide quantitative insights into lung mechanics during respiration, particularly in the supine position.