In order for the doctor to design your treatment, the exact location of the tumor, including its size and position relative to the surrounding structures (organs, bones, tissues, etc.) must first be determined. This is done typically by taking a detailed 3-D scan of the tumor with a CT scan (computed tomography). Depending on the general location of the tumor, disease type and other factors, additional scans may be recommended, which could include an MRI, a PET scan or an ultrasound scan. With the help of these scans, your healthcare team can see details of the tumor from every possible angle.

These imaging scans serve as guides, not only to enable the doctor to design your treatment, but also to help the rest of the team direct the radiation delivery equipment when treatment is actually being administered. It is therefore very important that the position in which you are being scanned is reproduced at the time of treatment. Sometimes temporary skin marks or even tiny tattoos (about the size of a freckle) are made on your body to assist in maintaining your position, day after day. Depending on the location of the tumor, a body mold, a head mask or other device may be constructed to make it easier for you to remain in the same position during treatment.

Once your scans have been completed, your doctor, the medical physicist and the dosimetrist will meet to design your treatment plan. They take many factors into account when they design the treatment plan. These can include the type of cancer, its location and size, your medical history, and your lab test results. The treatment plan considers these factors and determines the amount of radiation to be delivered, the appropriate angles from which to deliver it, and the number of sessions needed to deliver the prescribed treatment.

Once your treatment plan is complete, you will be informed about your number of treatment days and you’ll be given a treatment schedule. Before each day’s treatment, you may be asked to change into a gown. The radiation therapist (RT) will help you get positioned on the treatment “couch” – a platform designed to work with the radiation machine. If a facemask, mold or other device was created for you during simulation, it will be placed on you or under you at this time. The couch will be adjusted so a laser light shines on the mark that was put on your skin, helping to position you correctly. If you are treated on a Varian machine, the two arms of the machine’s On-Board Imager (OBI) may extend on either side of you in order to create an image of the tumor in that day’s treatment position and match it to the position that was planned for you. The scan is then compared to the planned position. If the target has shifted, even by a fraction of a millimeter, the RT can make fine-tuned adjustments to the couch with the touch of a button, to align you for treatment as accurately as possible.

If you are treated on a Varian machine, it will have a gantry, which is the head of the machine. The gantry houses a device called a multi-leaf collimator, which “shapes” the radiation beam so it conforms to the shape of the tumor from any given angle. During your treatment, the gantry will move around you to deliver the radiation with sub-millimeter accuracy. The treatment, or radiation beam, is not visible to the eye when it leaves the gantry so you will not see it.

Your first two treatments may take 15 minutes or more, as your team helps you get into position and takes images to verify that your set-up on the machine is the same as the treatment plan. Subsequent treatments are often shorter. In fact, some treatments—from entering the waiting room to leaving the clinic—can take as little as 12 to 30 minutes.

After your treatment course has ended, your doctor and other team members may initially want to see you at short intervals to monitor the results. Thereafter, checkups are typically scheduled at six-month intervals, but yours may be more or less frequent, depending upon your initial diagnosis