In a 0-degree PA projection, which structure is best demonstrated alongside the frontal bone?

In a 0-degree PA (posteroanterior) projection, the dorsum sellae is best demonstrated alongside the frontal bone due to the specific orientation and positioning of the X-ray beam. The PA projection directs the X-ray beam perpendicular to the imaging receptor while the patient's forehead and nose are in contact with the plate. This positioning aligns the dorsum sellae, which is a part of the sphenoid bone that forms the posterior aspect of the sellar space, directly in the path of the X-ray beam.

As a result, in the resulting image, the dorsum sellae appears well-defined and clearly outlines its relationship with the frontal bone. Additionally, the projection helps reduce the object-to-image receptor distance, enhancing the clarity of structures that lie in the midline, such as the dorsum sellae.

Other structures in the choices may not be as prominently visualized or may overlap with other features in the projection due to their anatomical positioning. For instance, the maxillary sinuses, while visible in a PA projection, provide more detail in an occipitomental view. Similarly, the temporal bone and mandible, although structurally important, might not be as distinctly displayed in this particular projection angle. Thus