CT simulation is a process used by the radiation therapy team to determine the exact location and size of the area to be treated. This is done in a room that contains a narrow, movable table and special X-ray equipment.

During simulation, you will lie on the table. The radiation therapist will position you and then watch you through a window while the CT scanner takes pictures or “slices” of the treatment site. Your radiation oncologist looks at the cancerous area with the radiation therapist.

You must lie still during simulation so the exact area to be treated can be pinpointed. Relaxing during simulation ensures consistent, accurate treatments. If you are already taking pain medication, you may want to take it before coming to your appointment and even bring some with you in case you need it.

The radiation therapist may use special pillows, pads, or other devices to help hold your body in the proper position. Sometimes contrast material (liquid with dye in it) may be swallowed or injected into your body so internal organs are easier to see on the CT scan.

After your radiation oncologist locates the area to be treated, the radiation therapist will outline the treatment field (area to be treated) on your skin. These tiny, permanent dots will be used as a guide for correct positioning during your treatments.

Simulation usually lasts between 15 and 30 minutes; however, you may need additional simulation after treatment has begun. After the simulation, dosimetry is performed.