Fig. 1

Airway wall thickness analysis. a The airway wall tree as extracted by the software program. The airway highlighted in yellow is stretched to a 2D picture in (b). The grey square corresponds to the purple vertical line in (b). This is a cross sectional image of the airway oriented perpendicular to the local centerline direction and given in more detail in (c). The red line is the outer airway wall perimeter and the yellow line is the inner airway wall perimeter. Airway wall thickness (AWT) and wall area percentage (%AWA) are measured in areas of the continuous red line. Dashed parts of the outer perimeter are interpolated and not used for measurements. The assessed perimeter fraction (APF) is the fraction of the outer perimeter that has a continuous line