At what angle is the central ray positioned during a PA projection of the skull?

In a posteroanterior (PA) projection of the skull, the central ray is positioned perpendicular to the image receptor. This positioning allows for a flat projection of the skull onto the image, minimizing distortion and providing a clear representation of the anatomical structures of the skull. When the central ray is perpendicular, it ensures that the shadow cast on the image receptor accurately depicts the true dimensions and relationships of the bones without the influence of angling that could alter the appearance of the structures. This method is crucial in radiographic imaging to obtain precise diagnostic images of the cranial anatomy.

Additionally, alternative angles such as 15 degrees caudad, 30 degrees cephalad, or 45 degrees caudad would produce different projections that could obscure clinical details essential for diagnosis, thereby reinforcing the importance of maintaining a perpendicular orientation for this specific projection.