Where does the central ray enter for the AP Axial projection at the midsagittal plane?

In the AP Axial projection, particularly when imaging the skull, the central ray's entry point is crucial for obtaining the correct positioning and angles to visualize the desired anatomical structures accurately. The central ray entering 2.5 inches superior to the glabella ensures that it aligns effectively with the midsagittal plane and is angled correctly (usually around 15-20 degrees downwards) to project the anatomy of interest, such as the cranial base or the sella turcica.

The choice of this entry point at 2.5 inches superior to the glabella allows for an optimal angle of projection to capture the relevant structures without distortion, as it effectively directs the beam through the midsagittal plane. This positioning is critical for ensuring that the resulting radiographic image provides the necessary diagnostic information while minimizing the chance of superimposition or artifacts that might obscure vital anatomy.