Figure 2.

Illustration of maximum narrowing detection between inspiration and expiration. The figure shows the inspiration‐expiration pair of sections with the minimum T. (a) Axial inspiratory scan image showing the inspiration section with the lowest T. (b) Detail view of the tracheal cross‐section in (a). (c) Axial expiratory scan corresponding to the inspiratory image in (a). (d) Detail view of the tracheal cross‐section in (c). In the detail views, the trachea segmentation is outlined in black. The four equiangular rays cast (at 0, 90, 180 and 270 degrees) from the center to the boundary of the trachea are shown in white, and the intersections of the rays with the trachea segmentation are highlighted with grey circles. These rays also represent the distances used for the computation of the T. The dashed rays depict the distance quantified by the tracheal features at 0 degrees.