From the case:
Orbitomeatal line (diagram)
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The orbitomeatal line, also known as the canthomeatal line, was the traditional axial plane used for CT of the brain. It was easily identified on the inspection of the patient's head when tilting the gantry or patient's head to achieve a standard axial plane.
The orbitomeatal line was defined as running from the outer canthus of the eye to the midpoint of the external auditory meatus.
Image from pixabay.com, in the public domain.