To be effective, radiation therapy must be aimed precisely at the same target or targets every treatment. Before we start treatments, we need to do what is called a simulation planning session. It involves:
Doing CT scan of your body and marking your skin to help your team direct the beams of radiation safely and exactly to their intended locations
Positioning you on the simulation machine in the exact position you will be in during the actual treatment
Using immobilization devices - molds, casts, headrests or other devices - to help you remain in the same position during the entire treatment.
Marking your skin and/or the immobilization devices either with a bright, temporary paint or a set of small, permanent tattoos.