Axial plane for imaging of the brain

A consistent axial plane for imaging of the brain needs to be chosen to allow for reproducible image acquisition and comparison. Unlike the sagittal plane, which is intrinsically defined by our inherent left-right plane of symmetry, axial and coronal planes need to be agreed upon and over the years a number of definitions of each have been proposed. 

The most widely used plane for MRI and increasingly for CT is Talairach's anterior commissure-posterior commissure (AC-PC) plane which, as the name implies, lies along the line connecting the anterior and posterior commissures. 

Other described and used planes include

• AC-PC line

  • Talairach definition

    • landmarks: from the superior edge of the anterior commissure to the inferior edge of the posterior commissure

    • use: most widely used axial plane for MRI and increasingly for CT

  • Schaltenbrand definition

    • landmarks: from the center of the anterior commissure and the center of the posterior commissure

• brainstem vertical line

  • landmarks: a line perpendicular to the posterior surface of the brainstem 

•  orbitomeatal line

  • ​landmarks: from the center of the mammillary body and the most posterior point of the cerebellar tentorium

  • use: traditionally most commonly used for CT 

• Reid's baseline

  • landmarks: from the center of the pituitary gland to the most posterior point of the cerebellar tentorium

  • use: imaging of the skull base, orbital cavity and paranasal cavities

• subcallosal line

  • landmarks: from the inferior border of the genu to the inferior border of the splenium of the corpus callosum

  • use: still recommended by the CMSC for MRI protocol for multiple sclerosis ²

• supraorbital-meatal line

  • landmarks: from the center of the mammillary body and the fastigium of the fourth ventricle

  • use: on tilted CT gantry systems, can be used to avoid irradiating the lens

• tuberculum sellae and the external occipital protuberance line

  • landmarks: from the tuberculum sellae to the internal occipital protuberance or the external occipital protuberance

  • use: parallel to the AC-PC line and convenient to use for axial CT reformats ³