The PA Caldwell projection is specifically designed to visualize the frontal sinuses by angling the central ray 15 degrees caudad, which projects the frontal sinuses above the orbital shadows. This projection also provides clear visualization of the anterior ethmoid air cells, but its primary clinical use is for assessing frontal sinus pathology such as sinusitis or fractures. The clear delineation of the frontal sinus structure is essential for surgical planning or diagnosis. The other sinuses (sphenoid, maxillary) are better demonstrated by different views (e.g., Waters or lateral projections).

Reference: Merrill's Atlas of Radiographic Positioning and Procedures, 14th Edition.