On the first visit, a Radiation Therapist will take the patient to the CT Simulator waiting area and explain what to expect during the planning session. The CT Simulator is not a treatment machine, but a diagnostic CT scanner used in the planning of the radiation treatment. The patient may have had a previous CT scan for diagnostic purposes; however, the simulation CT scan is necessary to accurately localize the treatment area. A Radiation Therapist will position the patient for the scan in the same position the patient will be in for treatments. Using the anatomical information gathered from the scan, the Radiation Oncologist will view the proposed treatment areas on a computer monitor and customize a radiation treatment to meet the particular needs of the patient. Care is taken to optimize the dose to the tumour while sparing normal surrounding tissue. This process usually takes between 15 and 45 minutes. If the treatment plan is complex, more than one CT scan may be required.
With the patient’s permission, once the scan is complete the therapists may place markings on the patient’s skin. These may be done using a waterproof pen for short courses of treatment, or permanent markings in the form of tiny tattoos may be used for courses of treatment longer than one week. If the treatment involves a facemask, the ink marks will be put on the mask rather than on the patient’s skin.
After the simulation, the plan is reviewed and approved by the Radiation Oncologist and the treatment team will make the final calculations for the treatment. Some patients may start treatment the same day as their simulation, while others may wait until a complex computerized treatment plan is created.