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Figure 1: Top left. Thin section CT image, perpendicular to the fourth generation of the right apical bronchus from a random patient. Top right. Sample of manual airway wall thickness extraction. Green doublehead arrow indicates external diameter D, and red doublehead arrow shows internal diameter L. Bottom left. Sample of manual delineation of the external layer (green line) and internal layer (red line), using the mouse on the CT scan image seen in top left. Bottom right. Automatic quantification of airway wall dimension (white arrow) using a Laplacian-of-Gaussian algorithm.