Figure 4

30-year-old man with chronic asthma. Coronally-reformatted inspiratory CT image shows normal lung parenchyma (a). Coronally-reformatted expiratory CT image shows extensive air-trapping (b). No collapse of trachea, main and lobar bronchi could be seen on axial scan (not shown). Axial inspiratory CT image through the lung bases shows normal bronchi (c). Axial expiratory CT scan demonstrates extreme narrowing of the bronchial lumen with air-trapping due to bronchial hyper-responsiveness (d).