When taking a posteroanterior (PA) axial projection (Caldwell method) of the skull, the central ray is directed:

For a posteroanterior (PA) axial projection of the skull using the Caldwell method, the central ray is indeed directed 15 degrees caudad. This specific angulation is key for accurately visualizing the orbits and the anterior cranial fossa while minimizing distortion.

In the Caldwell method, the patient’s forehead and nose are placed in contact with the film or detector, and the head is positioned in such a way that the orbitomeatal line (OML) is perpendicular to the film. The caudad angulation of 15 degrees directs the central ray through the nasion, which allows for a clear projection of the frontal sinuses and the occipital area.

This angling technique is a standard practice in radiography to ensure that the structures being imaged are adequately represented without superimposition from other anatomical features. Thus, understanding the correct angulation and positioning is crucial for achieving optimal radiographic results in cranial imaging.