Q. How do you define Normal Pulmonary Vasculature?

Pulmonary vessels are seen in the medial 2/3 of the lung. Vessels are generally not identified in the lateral third. The radiographic appearance of pulmonary vasculature is dependent on technique. Underexposure will lead to prominence of the vasculature, while overexposure will cause an apparent decrease in the vasculature.

Patient position may vary appearances greatly. In the erect position, there is reduced low to the upper lobes due to gravity. Alveolar pressure tends to collapse the upper lobe veins. The normal size ratio of upper to lower lung vessels is 1/2 or 1/3 on the erect PA radiograph. The hilar angle, which is the angle between the superior pulmonary vein and the descending pulmonary artery is normally concave.