Prior to actual radiation treatments, a simulation will be performed. This treatment planning process will identify the precise area of your body that the radiation will target. The exact positioning of your body during the simulation is important so that the radiation treatments are most effective. You will be placed in the same position for every treatment and will be asked to remain still during the treatment.
During the simulation, very small permanent tattoos will be placed on your skin to serve as markers that identify the treatment area. Depending on the area of the body being treated, it may be necessary for some patients to have an immobilization device made. The device will be used to make sure that you are in the exact position for every treatment.
Your CT scan will locate the treatment fields. The CT scan, which is not done for diagnostic purposes, will produce information that will be used to create a map so that a treatment can be designed specifically to treat your cancer. Sometimes, an MRI or a PET/CT scan will also be done to produce additional information to be used in planning your treatment.