Figure 3a. Transverse thin-section (2.5-mm section thickness) CT scans obtained in 41-year-old woman show diffuse panbronchiolitis. Centrilobular small nodules, branching nodular structures (tree-in-bud pattern) (arrowheads), and mosaic low-attenuation areas, features consistent with air trapping (open arrow), were observed in both lungs. Also note bronchiectasis (solid arrows) and volume decrease in middle lobe of right lung. (a) Image obtained at level of proximal basal arteries. (b) Image obtained at level of subsegmental bronchi.