Which line or plane is perpendicular to the IR when performing a lateral skull radiograph?

Which line or plane is perpendicular to the IR when performing a lateral skull radiograph?

• A. Orbitomeatal line (OML)
• B. Interpupillary line (IPL)
• C. Infraorbitomeatal line (IOML)
• D. Gonion line (GL)

Answer: (B)

In a lateral skull radiograph, the goal is a true lateral with no rotation, so the head sits perfectly side-on to the image receptor. The interpupillary line provides a stable, symmetrical reference across the face. When the interpupillary line is positioned perpendicular to the image receptor, the skull’s midline becomes parallel to the receptor, and the two sides of the skull are superimposed. This alignment minimizes distortion and ensures an accurate, true lateral view of the cranial structures, especially around the orbits and base of the skull. Other lines are useful for different views or orientations (for example, controlling tilt in other skull projections), but they don’t offer the same reliable reference for achieving a true lateral skull image.

In a lateral skull radiograph, the goal is a true lateral with no rotation, so the head sits perfectly side-on to the image receptor. The interpupillary line provides a stable, symmetrical reference across the face. When the interpupillary line is positioned perpendicular to the image receptor, the skull’s midline becomes parallel to the receptor, and the two sides of the skull are superimposed. This alignment minimizes distortion and ensures an accurate, true lateral view of the cranial structures, especially around the orbits and base of the skull.

Other lines are useful for different views or orientations (for example, controlling tilt in other skull projections), but they don’t offer the same reliable reference for achieving a true lateral skull image.