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Radiation Oncology: External beam therapy

External beam therapy (EBT) uses beams of photons and electrons to destroy cancer cells while sparing the healthy tissue that surrounds the tumor. A machine called a linear accelerator generates the beam, which is carefully targeted to deliver a dose of radiation to the tumor site within the body.

What to expect

External beam therapy requires very careful planning for optimal results. Therefore, it will include three stages.

  1. Simulation: You will begin with a simulator machine that will take X-rays. For the simulation, you will be positioned on the table in the same position that you will be in during your radiation therapy. The technologist will help position you, and straps and pillows may be used to help you maintain the correct position throughout the simulation. You may also get a CT scan where you will lie in that same position. Your radiation oncologist will use the images from the simulator and the CT scan to determine the tumor volume and the specific area to be treated.
  2. Treatment planning: Your radiation oncologist will work with the physicist and dosimetrist to make careful calculations about the doses needed, and develop a plan to deliver the appropriate dose to the tumor while minimizing the dose to the healthy surrounding tissues. 
  3. Treatment: The treatment will in many ways feel similar to the simulation. You will be situated on the linear accelerator table in exactly the same position as you were during simulation, using the same props to help you maintain the correct position. When the procedure begins, the machine will move around you, and you may hear some buzzing noises from the machine, but you should not feel anything from the machine. You will be alone in the room, but able to easily communicate with the technologist.

Most treatment plans call for radiation once daily, Monday through Friday, for one to nine weeks, although each treatment plan is unique. Treatment generally takes only a few minutes.

Learn more about our Radiation Oncology program.

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