Regional pulmonary function analysis using image registration

Lung function depends on the expansion and contraction of lung tissue during the respiratory cycle. The measurement of regional pulmonary function is of great interest and importance since many lung diseases can cause changes in biomechanical or material properties. It is also significant to study the radiation-induced changes in pulmonary function following radiation therapy.

In this thesis, we propose a technique that uses four-dimensional (3D+time) CT imaging (4DCT), 3D non-rigid image registration to estimate regional lung function. Lung images reconstructed at different inflation levels are analyzed for dynamic lung function development during a breath cycle. We demonstrate local pulmonary function can be reproducibly measured using 4DCT in human subjects prior to RT. The image registration accuracy is validated using semi-automatic anatomic landmark picking system.

The major contributions of this thesis include: 1) demonstrating the robustness and reproducibility of regional pulmonary function measurement using 4DCT in both sheep and human subjects, 2) developing approaches to improve the measurement reproducibility by dynamic lung volume matching and Jacobian normalization, 3) development and comparison four cubic metrics for reproducibility analysis, 4) research on time-varying lung ventilation in different breathing phases in both sheep and human subjects. Our contributions in this thesis are useful for diagnosis and assessment of lung diseases, useful for qualifying radiation induced changes in pulmonary function in irradiated and non-irradiated lung tissue.