How is the CR directed for a PA axial projection (Caldwell method) of the skull?

In the PA axial projection using the Caldwell method for the skull, the central ray (CR) is directed 15 degrees caudad. This specific angulation is designed to project the orbits below the frontal bone, providing a clearer view of the cranial structures. The 15 degrees caudad angle helps to highlight the frontal sinuses and reduces superimposition of the orbits over the skull.

This positioning technique is essential because it ensures that specific anatomical details, such as the sella turcica and the petrous ridges, are well visualized while maintaining an optimum image quality. This projection is commonly used in cranial imaging to assess possible fractures, lesions, and other conditions.

The other angles provided in the options would not position the CR correctly to achieve the desired imaging results in the Caldwell method. A higher degree of angulation or a different direction could obscure critical areas of interest or distort the anatomical relationships in the image being captured.