[Previous] [Next]  PA Chest  Many of the mediastinal structures
have intermediate levels of density, so it is difficult to
discern them with radiography. However, structures that are
adjacent to the radiolucent lungs (less dense) can be visualized
due to the difference in density.  Identify the following:  1.
heart  2. aortic knob (the "edge" that corresponds to the
portion of the aortic arch in contact with the lung)  3.
superior vena cava  4. descending aorta  5. trachea  Can you see
where the trachea birfurcates? Answer