Central Nervous System Normal Structures
Recent developments in radiation and neuro-oncology provide the ability to deliver required radiation dose to target volumes for pediatric brain tumors while avoiding sensitive normal central nervous system (CNS) structures uninvolved by tumor. Many CNS target volumes are smaller than in previous years due to better understanding of areas at risk for recurrence or involvement and patterns of spread for given diagnoses. Advances in neuroimaging and treatment planning software allow for better delineation of tumors and normal neuroanatomy. Utilization of these advances requires accurate delineation of avoidance structures. For optimal avoidance as well as accurate reporting of normal structure tolerance, it is of paramount importance to contour these structures properly. Neuroanatomy is complex and formal education in this area is not at present formally taught in radiation oncology training. This chapter is included to provide guidance for contouring of pediatric CNS structures.