OpticChiasm

Delineation Information

Modality

CT

Guideline

Taken from Eekers DBP, Di Perri D, Roelofs E, Postma A, Dijkstra J, Ajithkumar T, et al. Update of the EPTN atlas for CT- and MR-based contouring in Neuro-Oncology. Radiother Oncol 2021;160:259–65. https://doi.org/10.1016/j.radonc.2021.05.013.

Method

Manual The optic chiasm (14 mm transverse, 8 mm antero-posterior and 2–5 mm thick) is located 1 cm superior to the pituitary gland, which has high signal on T1 MRI, and just anterior to the pituitary stalk (located above the sella turcica). The lateral border is the internal carotid artery. The chiasm is superiorly located in the antero-inferior part of the third ventricle, below the supra-optic recess and above the infundibular recess of the third ventricle, with the optic nerves in front and the divergence of the optic tracts behind. The anterior cerebral arteries and the anterior communicating artery are located ventral to the chiasm.

Anatomical Boundaries

Cranial

supraoptic recess

Caudal

1 cm superior to the pituitary gland

Lateral

Internal carotid artery

Ventral

Optic nerves

Dorsal

Divergence of the optic tracts

Additional Metrics