The right mid-lung window.

On conventional chest radiographs, an area of diminished vascularity usually indicates focal disease. On CT scans of the chest, however, there is often a focal vascular deficiency in the right mid-lung that appears to be normal. In a study of 50 patients, diminished vascularity was noted at the level of the bronchus intermedius on 92% of the scans. The anatomical basis for this finding is discussed.