Fig. 1

Twenty-minute dynamic posterior acquisition presented as eight pictures each representing 2½ min of normal tracheobronchial bolus transport. Boluses of mucus are seen to ascend from the main stem bronchi to the trachea (top four pictures) and further up the trachea (bottom four pictures). In the midline, two ⁵⁷Co markers placed above the vertebra C7 and L1 are seen over the trachea and under the lungs, respectively