Three-dimensional visualization and morphometry of small airways from microfocal X-ray computed tomography.

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Anatomy

Background:

• Physiological morphometry significantly influences airflow dynamics in small airways.
• Previous methods for airway visualization often require dehydration and fixation, potentially altering natural geometry.
• Accurate three-dimensional (3D) structural data of small airways is essential for biomechanical studies.

Purpose of the Study:

• To develop and validate a novel method for visualizing and analyzing the 3D structure of small airways without fixation.
• To reconstruct and analyze the morphometry of small airways (generations 8-16) in rat lungs.
• To assess the utility of the developed method for understanding biomechanical dynamics.

Main Methods:

• A two-step staining and computed tomographic (CT) imaging (SCT) method was developed.
• Lung tissue was stained with a radiopaque solution and visualized using a cone-beam microfocal X-ray CT system.
• A 3D thinning algorithm was employed to analyze airway morphometry, including diameter, length, and angles.

Main Results:

• The SCT method successfully visualized 3D branching and merging bronchi (500–150 µm) in excised rat lungs without fixation.
• Airway diameter and length were found to decrease exponentially with increasing airway generation.
• Bifurcation asymmetry decreased with generation, and one branching angle influenced the other.

Conclusions:

• The SCT method is the first reported technique to provide high-resolution, faithful 3D images of soft tissue geometry without fixation.
• The detailed 3D morphometry of small airways obtained using this method is valuable for biomechanical dynamics research.
• This non-destructive imaging approach offers a significant advancement in pulmonary research.