In a correctly positioned parietocanthial projection (Waters method), where should the petrous pyramids be seen with respect to the maxillary sinuses?

• A. Above the maxillary sinuses
• B. At the level of the maxillary sinuses
• C. Below the maxillary sinuses
• D. Superimposed on the maxillary sinuses

Answer: (C)

In a correctly positioned parietocanthial projection, also known as the Waters method, the petrous pyramids are visualized below the maxillary sinuses. This positioning is crucial for accurately assessing the maxillary sinuses, as the method is designed to provide a true representation of these structures.

The Waters projection involves the patient's chin being placed in contact with the image receptor, which angles the petrous ridges sufficiently downward. This results in the petrous pyramids being projected into the lower part of the image, thus positioning them below the maxillary sinuses. This positioning allows for a clear view of the sinuses and surrounding anatomical structures, which is important for diagnosis and treatment planning.

Visualizing the petrous pyramids below the maxillary sinuses confirms that the radiographic technique has been executed correctly and that the structures will not obscure the evaluation of the sinuses.