Where does the CR exit for the parietoacanthial projection for the skull?

In the parietoacanthial projection, commonly referred to as the Waters view, the central ray (CR) exits at the acanthion. This projection is specifically designed to visualize the maxillary sinuses, orbits, and nasal structures. Positioning the CR to exit at the acanthion ensures that the anatomical structures of interest are properly aligned and clearly demonstrated.

The acanthion is located at the junction of the upper lip and the base of the nose, serving as a standard reference point in skull imaging. Using this specific exit point allows radiologists to accurately assess not just the maxillary sinuses, but also important relationships between facial bones and the skull. Thus, positioning the CR accurately at this landmark is crucial for achieving high-quality images in radiographic examinations of the skull.