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The Radiation Planning Session (Simulation)

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Careful planning is necessary before your radiation treatment can begin. The planning ensures that you get the full benefit of radiation with minimal impact on other parts of your body. During the planning session, a radiation oncologist maps out the breast area that needs treatment. The oncologist or radiation technician uses a special X-ray machine called a simulator, and the process is called simulation because the treatment is being "simulated," or not really given.

Because it is so important to position the angles of radiation accurately, the planning session can sometimes last up to an hour. The extra time and care during this session will make your future visits run more smoothly and help you get the most from your radiation therapy. You do not receive any treatment during the planning session.

Here's what you can expect to happen during your planning session visit to the radiation oncology department.

Before simulation

At the beginning of your planning session, your doctor will:

  • explain the pros and cons of radiation, the planning and treatment process, and answer any questions or concerns you may have
  • review the consent form and have you sign it
  • introduce you to the treatment team

During simulation

Your doctor will precisely identify the area on your body where you will receive radiation.

Positioning is extremely important in radiation therapy. Your body will be positioned carefully in order to get the best radiation treatment. You will be in the same position during every treatment, and you will have to remain still. To stabilize your position, you will probably be asked to lie in a special "immobilization device" on the treatment table.

There are different kinds of immobilization devices. Some look like a cradle; others look like a foam box that is shaped to your form. You will not be trapped or closed in. You may be asked to lie down in a custom-shaped mold that just touches your back and sides; or your treatment center may use a "breast board" that places your head, arm, and hand in a fixed position. Unfortunately, no padding can be used on the treatment table or positioning devices because that makes your treatment position less precise.

Pictures will be taken of the area that needs to be treated. Those images are sent to the radiation planning computer, which will help set up the general treatment fields (the areas that get the radiation).

Once the treatment fields are set, the radiation oncologist will mark the corners of the fields with small tattoos or a special pen (markings are usually no bigger than the head of a pin or a freckle). The marking is a guide to help the technician line up the radiation treatment fields the same way each time you receive treatment.

Most cancer centers today recommend that people have tattoo markings for radiation therapy rather than ink markings, because the ink can fade or wash off. While tattoos can be removed after treatment is over, they are also preferred over ink markings made with a pen because are that they permanently mark the area of the original treatment field in case radiation is needed in the future.

Tattoo markings are done with a very small needle and drop of ink. Some women may feel a small pinch, like an insect bite, while the markings are being created. A tattoo marking will have the appearance of a dark freckle.

After simulation

After the simulation is done, the dose of radiation you'll receive is calculated, and your radiation treatment is designed over the next few days. This is called dosimetry. Your radiation oncologist works closely with a radiation dosimetrist, who helps further define the best arrangement and size of your treatment fields and is responsible for making sure you receive the correct amount of radiation. Together they establish the size, shape, and number of the treatment fields. The treatment fields are designed to maximize the dose of radiation to the area that needs to be treated and to avoid or minimize the dose to the normal surrounding tissues.

A second planning session is usually required to verify the whole plan set-up in the treatment room. Special X-rays are taken of each treatment field to make sure they are all set up correctly, and additional markings may be made to better define the confirmed treatment fields.

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