Which paranasal sinuses are best demonstrated in the PA axial projection (Caldwell method)?

In the PA axial projection using the Caldwell method, the best demonstration is of the frontal sinuses. This technique utilizes angled positioning to project the frontal sinuses above the orbits, allowing for clear visualization on the resulting radiograph. The central ray is typically directed at an angle (usually 15 degrees) to the nasion, which helps to project the frontal sinuses into the path of the x-ray beam while minimizing the obstruction that other structures may cause.

The frontal sinuses are located just above the orbits, and during this projection, they are less likely to be obscured by surrounding anatomical structures. The results provide a clear view of the frontal sinuses for assessment of any pathology, such as sinusitis or other conditions. Understanding the positioning and angling in the Caldwell method is crucial for achieving optimal imaging of these particular sinuses.