Patients irradiated to the brain frequently experience nausea. The dorsal vagal complex (DVC) area is a specific brainstem zone and has been identified as likely responsible for nausea. Existing clinical studies show correlation between dose to the DVC and nausea, but they concern tumors of the airways and upper digestive tract, where there are many confounding factors. The aim of this study is to establish a ling between radiation dose to the DVC and nausea. Defining a dose threshold to the DVC will allow radiation oncologists to optimize radiation dose distribution and reduce nausea in patients.