Which projection of the skull will result in the greatest exposure to the lens of the eye?

• A. Verticosubmental.
• B. Posteroanterior (PA) axial.
• C. Anteroposterior (AP) axial.
• D. Lateral.

Answer: (C)

Exposure to the lens hinges on how directly the primary X-ray beam passes through the orbits and how close the lens is to the source. The AP axial skull projection places the tube in front of the face and angles the beam through the orbits in a direct, high-intensity path, so the lenses lie right in the beam and receive the greatest dose. In the PA axial projection, the tube is behind the patient, so the eyes are farther from the source and more tissue attenuates the beam before it reaches the lenses, reducing exposure. The other projections either position the orbits away from the most intense part of the beam or direct the beam through facial structures that don’t involve the lenses as directly. Therefore, the AP axial projection yields the greatest exposure to the lens.