A radiation oncologist's guide to contouring the Hypothalamus
Faculty and Abstracts
Purpose: Limiting the dose to the hypothalamus will likely decrease endocrine problems from brain radiotherapy. The purpose of this poster is to present a step-by-step guide to contouring the hypothalamus on axial images as would be done in the standard process of planning conformal radiotherapy for brain radiotherapy.
Methodology: We explain how to contour the hypothalamus on axial T1 echo sequence magnetic resonance images with intravenous gadolinium.
Results: To accurately identify and delineate the hypothalamus on an axial MRI, follow a systematic process. Begin by understanding that the hypothalamus is a collection of diencephalic nuclei located deep in the inferior lateral parts of the third ventricle. Familiarize yourself with the anatomy of the third ventricle, the cavity of the diencephalon. Then, locate the anterior boundary of the third ventricle, marked by the anterior commissure and the lamina terminalis. Recognize that the hypothalamus lies beneath the third ventricle and appears as funnel-shaped grey matter, extending inferiorly and connecting to the infundibulum linked to the pituitary gland. Use T2-weighted images to enhance third ventricle contours and switch to T1-weighted images to confirm hypothalamic grey matter. Identify the anterior boundary, posterior boundary defined by the hypothalamic sulcus, and explore the floor and lateral wall of the hypothalamus. By following these steps and considering adjacent structures, you can accurately contour the hypothalamus on axial MRI.
Conclusions: This poster presents a step-by-step guide to contouring the hypothalamus on axial magnetic resonance images for radiation therapy treatment planning.
