Olson A, et al. - The goal of this study is to assess beam attenuation from head and neck (HN) immobilization devices in volumetric-modulated arc therapy utilizing the Eclipse treatment planning system and the Anisotropic Analytical Algorithm. It is not a standardized practice among institutions to include immobilization devices within the body contour for dose calculations. However, with the increasing utilization of volumetric-modulated arc therapy for treatment of the HN region, precision is of the utmost importance, and the inclusion of immobilization devices ought to be standardized.