Cardiothoracic Imaging
Contents Anatomy Techniques Findings Cases References
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Image finding: Normal chest PA film, case 2




Notes

COMMENTS

Erect posterior-anterior ("PA") chest radiograph PA images commonly show significant differences from AP (antero-posterior) films particularly in relation to the proportional size of the mediastinum. The PA position places the heart and upper mediastinum closer to the film with greater distance to the exposing Xray tube (generally 72 inches) making the Xrays more parallel as they enter the body and avoiding disproportional enlargement of anterior vs. posterior structures.

The effects of gravity have visible effects on the pulmonary vasculature since the pulmonary artery pressures are low (~25 mm Hg. in systole and ~12 mm Hg. in diastole) and the vessel walls are soft and compliant.

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December 18, 2004 (PL)
version b.003