Where is the central ray directed for a transthoracic lateral projection of the humerus?

For a transthoracic lateral projection of the humerus, the central ray is directed to the surgical neck of the humerus. This area is anatomically significant because it serves as a narrow section where the proximal part of the humerus transitions into the long shaft, making it a relevant landmark for imaging.

When performing this projection, the goal is to obtain a clear visualization of the entire humerus in profile, especially in situations where there may be an injury or fracture. Targeting the surgical neck allows the radiologist to see both the proximal and distal aspects of the humerus, including the relationship of the shoulder joint and the elbow.

The surgical neck of the humerus is also clinically important since it is a common site for fractures, particularly in older populations, making its assessment crucial in medical evaluations. This anatomical focus ensures that the radiographic image effectively captures any potential pathologies associated with this area.