Each bronchus branches into secondary bronchi (one per lobe of lung), tertiary bronchi (one per segment of lung), and many bronchioles leading to the pulmonary alveoli. 每根支气管再分成二级支气管（肺的每一叶）、三级支气管（肺的每一段）以及许多通向肺泡的细支气管。
VRT was the best way to display the mainly body of the pulmonary artery embolism. The next better one were MIP,MPR and the VE in order. MIP and MPR well displayed the small pulmonary artery embolism which below the lobe of lung. VRT成像对显示肺动脉主干部位的栓塞最为直观,依次为MIP、MPR及VE图像,其中MIP、MPR成像对显示肺叶以下动脉小栓塞情况较好。
Chest X ray realed infiltration in low lobes of lungs. 胸部X线 4 5例 (83.
Medial segment of right middle lobe of lung 右肺中叶内侧段
Space-occupying lesion in left upper lobe of lung 左上肺占位