How should the central ray be directed when performing a posteroanterior (PA) (Cladwell method) of the sinuses with a vertical image receptor?

When performing a posteroanterior (PA) projection of the sinuses using the Caldwell method, the central ray must be directed horizontally, meaning it should be perpendicular to the image receptor and the floor. This orientation ensures that the anatomical structures of the sinuses are adequately visualized without distortion caused by improper angling.

In the Caldwell method specifically, the central ray is directed through the nasion, which is the bridge of the nose, and aimed horizontally to capture a clear image of the frontal sinuses, ethmoid sinuses, and any related structures. This positioning is crucial for providing diagnostic quality images that can be accurately interpreted.

The other options, such as vertical or angled directions like 45 degrees caudal or 25 degrees cephalic, would not fulfill the requirements of the Caldwell method and could lead to misrepresentation of the sinuses’ structures in the resulting image. These angles would not align the central ray appropriately to capture the frontal and ethmoidal sinuses effectively.