Which statement is true regarding the posteroanterior (PA) axial projection of the paranasal sinuses?

In the posteroanterior (PA) axial projection of the paranasal sinuses, the frontal and ethmoidal sinuses are indeed visible, making this statement accurate. This projection is specifically designed to allow clear visualization of these sinuses along with the maxillary sinuses. The orientation and angle positioning of the patient's head is crucial during this procedure; the facial bones are arranged so that the sinuses are projected effectively onto the film or digital receptor.

In this projection, the central ray typically enters at the nasion, which helps to project the frontal and ethmoidal sinuses directly in the path of the x-ray beam. As a result, the anatomy of the frontal and ethmoidal sinuses appears well-defined, providing valuable diagnostic information regarding any potential pathology.

The other statements do not accurately describe the PA axial projection. The orbitomeatal line does not form a 30-degree angle with the central ray in this projection and is actually positioned differently during the imaging. Furthermore, the orbitomeatal line is not parallel to the floor, which is crucial for correctly visualizing the sinuses, and clarity of the frontal and ethmoidal sinuses is not achieved when they are not correctly oriented or positioned during the imaging process.