The process of measuring your body and marking your skin to help your team direct the beams of radiation safely and exactly to their intended locations is called simulation also called “marking session” or making “measurements.” This visit may take up to an hour and is critical in creating the best possible treatment plan for you.
On the day of simulation you may have been given instructions drink some contrast, to keep a relatively full bladder, or even to have taken a laxative or enema to help empty your rectum. You may be given IV contrast. The purpose of these maneuvers is to provide the best treatment plan and to minimize the toxicity of treatment. We appreciate you working with us on these steps.
During simulation, your radiation oncologist and radiation therapist place you on the simulation machine in the exact position you will be in during the actual treatment. Immobilization devices are molds, casts, headrests or other devices that help you remain in the same position during the entire treatment. Your radiation therapist, under your doctor’s supervision, then marks the area to be treated directly on your skin or on immobilization devices. In this position, you will undergo a separate CT scan which will be used for treatment planning, also known as “CT simulation.”
Once you have finished with the simulation, your radiation oncologist and other members of the treatment team review the information they obtained during simulation along with your previous medical tests to develop a treatment plan. Often, a special scan is done to provide additional images to “fuse” with your simulation scan – this may be a MRI or a PET/CT scan.
Sophisticated treatment-planning computer software is used to help design the best possible treatment plan. After reviewing all of this information, your doctor will construct a radiation therapy course that treats the exact area of concern while minimizing radiation exposure to normal body tissues.