What positioning requirement must be met when radiographing the skull in the lateral position?

When radiographing the skull in the lateral position, it is essential for the midsagittal plane to be parallel to the image receptor (IR). This positioning is crucial because it ensures that the skull is accurately demonstrated without any distortion and that both sides of the skull are evenly represented.

In the lateral view, the goal is to capture a profile of the skull, which relies on the proper alignment of anatomical planes. By keeping the midsagittal plane parallel, this allows for optimal visualization of the lateral anatomy, including the structures of the cranium and facial bones. Proper alignment reduces superimposition and maintains the image quality necessary for diagnostic purposes.

Positioning the interpupillary line, midsagittal plane, or infraorbitomeatal line incorrectly, as seen in the other options, would not provide the optimal representation of the skull for lateral projection and could lead to diagnostic errors or inadequate images.