If you are eligible and agree to take part in this study, you will have a computed tomography (CT) simulation. A simulation is like a planning session for your SSRS. For this, a bag filled with small foam beads is formed to your body and then the air is vacuumed out. This creates a mold that you will lie in so that the doctors can plan the radiation treatment that you will receive. This mold will then be used to keep you from moving during SSRS. If the study doctor thinks it is needed, a meshed plastic mask will also be used to fit to your head and neck area to help accuracy during SSRS. If a mask is used, you will still be able to breathe normally.