Thalamus

Thalamus

The thalamus is a central structure within the brain that acts as a major relay and integration hub for information travelling between different regions of the nervous system. Nearly all sensory information, with the exception of olfaction, passes through the thalamus before reaching the cerebral cortex. Beyond its well-known role in sensory processing, the thalamus also contributes to a wide range of cognitive functions, including attention, learning, memory, information processing, and cognitive flexibility. Through its extensive connections with cortical and subcortical networks, the thalamus is essential for normal cognitive performance and efficient communication between brain regions.Because of its central role in sensory, cognitive, and behavioural networks, there is increasing interest in assessing radiation dose to the thalamus and its potential impact on neurocognitive outcomes and quality of life after brain irradiation. Accurate delineation is therefore important for both clinical practice and research.

For contouring, the left and right thalamus should be delineated separately. Co-registration with a T1-weighted MRI is recommended to facilitate accurate identification of the structure. The thalami are paired, oval-shaped grey matter structures situated deep within the brain and measuring approximately 4 cm in length. Although generally similar in appearance, slight asymmetry between the two sides is common.

Key anatomical landmarks include:

• Medial border: the third ventricle, with the left and right thalami often connected by the interthalamic adhesion.Lateral border: the posterior limb of the internal capsule.
• Anterior border: the level of the interventricular foramen.
• Posterior border: the atrium of the lateral ventricle.
• Superior border: forms part of the floor of the lateral ventricle.Inferior border: adjacent to the hypothalamus anteriorly and the midbrain posteriorly.

The accompanying video provides a step-by-step demonstration of how to identify and contour the thalamus using these anatomical landmarks. This educational resource is intended to support consistent, accurate, and reproducible delineation for clinical and research applications.

Please site as follows:

Hofstede, D., Di Perri, D., Roelofs, E., Postma, A., Troost, E., & Eekers, D. EPTN International Neurological Contouring Atlas (INCA) instruction videos. CancerData, 2022. doi:10.17195/candat.2022.02.1