Orbitomeatal line

A.Prof Frank Gaillard et al.

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 1,2

This plane fell out of favor for CT of the brain as it generated significantly elevated doses to the lens compared to planes that avoid the orbit 1. Until recently the standard plane for CT of the brain in most departments was along the roof of the orbit, seen easily on the CT scout. This had the advantage of including the posterior fossa but avoiding the lens. 

More recently, with volumetric scans becoming standard, and many CT scanners no longer being able to tilt, the whole head is scanned and then axial images are reconstructed at any desired angle. As such many departments are switching the standard axial CT brain plane to be aligned with the AC-PC line which is standard in MRI 2,3. Interestingly, this plane is quite close to the original orbitometal line and to the plane of the planum sphenoidale and hard palate

Share article

Article information

rID: 50729
Section: Radiography
Synonyms or Alternate Spellings:
  • Canthomeatal pitch

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.