External Radiation Therapy at the Knight Cancer Institute

A female patient undergoes external radiation therapy
The OHSU Knight Cancer Institute offers the latest technology for radiation therapy. We are able to precisely target cancer while avoiding healthy tissue.

At the OHSU Knight Cancer Institute, our team specializes in all types of external radiation therapy.

We offer: 

  • Leading-edge technology and innovative new approaches. 
  • Tools and techniques to precisely target cancer while sparing healthy tissue. 
  • Experienced radiation oncologists who work with your full cancer team to give you the best possible care. 

What is external radiation therapy?

Tuality/OHSU Cancer Center radiation therapist Estel Hayes prepares radiation therapy equipment.
Tuality/OHSU Cancer Center radiation therapist Estel Hayes prepares radiation therapy equipment.

External beam radiation attacks cancer with high-powered beams of energy, such as X-rays. It uses a machine called a linear accelerator to send energy beams through the skin and into the body. While you lie on a table, the linear accelerator moves around you, sending radiation to the tumor from different angles.

Schedule: Treatment usually lasts five days a week for several weeks. This allows your team to deliver enough radiation to kill cancer cells while giving your body time to recover.

Type: Your team may consider several types of radiation therapy. They will recommend a treatment plan tailored to your overall health and the type and stage of your cancer.

What is it? 3D CRT uses computer-assisted scans to pinpoint the size, shape and location of your tumor and surrounding organs. This helps your doctor tailor radiation beams to the shape of the tumor. Because the shaped beam is so precise, we can deliver a higher dose of radiation without harming healthy cells.

How is it delivered? Most patients receive 3D CRT five days a week for several weeks. Your radiation oncologist will make a mold or cast of the body part being treated. This serves as a shield and helps you stay still so radiation targets the tumor and avoids healthy tissue. It helps destroy more cancer cells with each treatment and allows you to recover more quickly.

What cancers is it used for?

  • Breast cancer 
  • Children’s cancers 
  • Cancers that have traveled to the brain or bone 

What is it? IMRT is a specialized type of 3D conformal radiation therapy that breaks the radiation into many beams to “paint” treatment in three dimensions. The tumor is first mapped in 3D using computed tomography (CT) scans or magnetic resonance imaging (MRI). Then computers calculate and vary radiation doses from different angles. It allows your doctor to more precisely match the shape of the tumor and vary radiation to different parts of the tumor. This precise control can lessen side effects.

How is it delivered? Most patients receive IMRT five days a week for several weeks. Because of the many angles used to deliver radiation, each treatment may take as long as an hour to deliver.

What cancers is it used for?  

  • Brain tumors 
  • Gastrointestinal cancers 
  • Gynecologic cancers 
  • Head and neck cancer 
  • Lung cancer 
  • Prostate cancer 
  • Sarcomas 
  • Thyroid cancer 

What is it? IGRT is a type of intensity-modulated radiation therapy that uses scans during therapy to better target cancer cells. This is important because moving or breathing can change a tumor’s position. IGRT allows the doctor to make sure that the treatment is delivered to where the cancer is each day. It uses scans such as ultrasounds, X-rays, MRI, PET or CT scans for planning and just before a treatment session.

How is it delivered? Most patients have IGRT once a day five days a week. During treatment, you will have a series of scans. Your doctor will analyze the scans by computer to find any changes in the tumor’s position or size. Your doctor will then adjust the dose or location to target cancer cells and avoid healthy tissue.

If you have prostate cancer, you may receive IGRT using the state-of-the-art Calypso system. Calypso lets us continuously monitor your tumor with tiny sensors placed inside the prostate gland. We can focus radiation on the tumor and spare healthy areas.

What cancers is it used for?

  • Brain cancer 
  • Gastrointestinal cancers 
  • Children’s cancers 
  • Prostate cancer 
  • Lung cancer 
  • Lymphoma 

What is it? Proton therapy is a different type of external radiation. It uses proton beams instead of photon beams, the standard form of external radiation.

Protons are positively charged particles of energy that can be targeted to stop within the tumor. This allows the doctor to reduce the amount of healthy tissue that receives radiation.

How is it delivered? A machine speeds up the protons, then sends proton beams through the skin to your tumor. The beams conform to the shape and depth of the tumor.

Oregon currently has no proton therapy center. However, the Tuality/OHSU Cancer Center offers proton therapy consultation with Medical Director Dr. Timur Mitin.

Dr. Mitin studied proton therapy at Harvard University, which has one of the longest-running proton therapy programs in the country. His expertise can help you decide if this treatment is right for you. If you choose to go ahead, we can refer you to a center that offers it.

What is it used for? Proton therapy is most effective for childhood tumors and for tumors that are near important body parts such as the eyes, brain or spinal cord. 

What is it? Stereotactic body radiation therapy is similar to stereotactic radiosurgery, but it’s used to treat areas beyond the brain and spinal cord. In SBRT, IGRT is combined with more advanced techniques to deliver high doses of radiation to the tumor in fewer treatment sessions.

Your team will use advanced imaging techniques such as MRI and CT scans to zero in on tumor tissue. At OHSU, we use the sophisticated Novalis Tx system for SBRT, ensuring that you get the optimum dose while sparing healthy tissue.

How is it delivered? Patients usually have up to five sessions, with one a day. Most sessions take a few minutes to an hour.

The Novalis Tx machine rotates around you, adjusting to your movements. The imaging system makes sure radiation focuses on the tumor. Because we can send more radiation to the tumor at each session, you may need fewer sessions than with other radiation treatments.

What cancers is it used for?  

  • Lung cancer 
  • Liver cancer 
  • Pancreatic cancer 
  • Head and neck cancer 
  • Previously treated cancers
A TomoTherapy machine.

What is it? TomoTherapy is a type of image-guided IMRT that combines CT and external beam technology in one machine. Your doctors can adjust your treatment as they go based on even the smallest anatomy changes.

How is it delivered? Most patients receive TomoTherapy in a daily visit five days a week. Each session lasts 10 to 20 minutes. The machine is shaped like a doughnut, and you recline on a bed in its center. It scans your tumor, then rotates around you to send radiation precisely where you need it.

What cancers is it used for?

  • Gynecologic cancers 
  • Head and neck cancers 
  • Rectal and anal cancers 
  • Pancreatic cancers 
  • Spinal cord cancers 
  • Children’s cancers 

What is it? Also called total body radiation therapy, this treatment uses a low dose of radiation to kill cancer cells throughout your body. Because radiation travels through your entire system, TBI may be used to treat blood disorders or blood cancers. If your treatment plan includes a bone marrow or stem cell transplant, you might have TBI first. This helps keep your immune system from harming the transplanted healthy cells.

How is it delivered? Your lungs and kidneys may be covered with a shield to protect them from radiation. Depending on your cancer type and other factors, you might have several treatments or just one. Because you’ll receive a low dose, you might also have chemotherapy to help destroy cancer cells.

What cancers is it used for? 

  • Leukemia 
  • Lymphoma 
  • Multiple myeloma 
  • Other blood disorders 

What is it? Unlike other forms of radiation, which use photons, this type uses electrons to treat a rare cancer called skin lymphoma. Electrons are useful because most of the radiation dose is absorbed into the skin.

How is it delivered? TSEB is usually done over 18 or 36 treatments, Monday through Friday. Because the radiation is distributed over your entire skin, patients stand during treatment. OHSU uses the Stanford technique, in which you stand in three positions one day, then three different positions the next day. This allows the radiation to reach as much of your skin as possible.

What cancers is it used for? Mycosis fungoides, the most common type of skin lymphoma. 

What is it? Also called alternating electric field therapy, TTF fights cancer with mild electrical fields instead of radioactive beams. A wearable device sends electrical pulses through the skin in your scalp. These pulses disrupt cancer cells’ ability to reproduce. When cancer cells can’t grow, they die. TTF does not affect normal cells.

How is it delivered? Patients wear a portable, battery-operated device for most of the day. Shaped like a close-fitting cap, the device sends alternating electric fields to the tumor. TTF can be delivered at home. Patients usually check in with their care team every month or two to monitor effectiveness. The Tuality/OHSU Cancer Center was the first in the state to offer TTF. 

What cancers is it used for? It is a promising treatment for glioblastoma, a fast-growing cancer that affects the brain and spinal cord. More research is needed before it is approved to treat other types of cancer. 

Learn more

For patients

  • Request an appointment at our Marquam Hill location: 503-494-8756
  • Request an appointment at our Beaverton location: 971-262-9400

Visit our For Cancer Patients page to find a cancer doctor and links to diagnoses.


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Portland, OR 97239
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Beaverton, OR 97006
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