Internal Radiation Therapy at the Knight Cancer Institute

Dr. Charles Thomas, one of OHSU’s radiation oncologists
Dr. Charles Thomas is just one of OHSU’s radiation oncologists. Our doctors are skilled in all types of radiation therapy and will recommend the most effective treatment for your needs.

We offer you expertise in all types of internal beam radiation therapy. You’ll find:

  • The latest techniques to safely attack cancer cells while avoiding healthy tissue. 
  • Advanced technology to deliver internal radiation more quickly and with fewer side effects. 
  • Radiation experts who work with the rest of your cancer team to give you the best possible care. 

What is internal radiation therapy?

Internal radiation therapy places a source of radioactive material in or near a tumor. It allows your cancer team to safely and effectively deliver a higher dose than with external beam radiation therapy. It can be permanent or temporary depending on your diagnosis and needs.

Your team may consider several kinds of internal radiation therapy. They will recommend the one that’s best for you based on your overall health and the type and stage of your cancer.


What is it? Brachytherapy places tiny radioactive implants in the shape of seeds, capsules or pellets in the tumor (interstitial brachytherapy) or nearby (intracavity brachytherapy).

Treatment can be temporary, with your doctor removing the implants after treatment. Or it can be permanent, with the material staying in place. This is safe because the implants produce less radiation as time passes. Low-level radiation will not harm people around you.

How is it delivered? Brachytherapy can be given in a high-dose rate (HDR) or a low-dose rate (LDR).  

  • HDR: This treatment is temporary and given in repeat sessions. Because it uses powerful radiation, it usually takes less time than LDR brachytherapy. Your doctor will use thin flexible tubes called catheters to precisely place the implants. The implants are removed after a few minutes. You may have one or two HDR sessions in one day, or several in a week.  
  • LDR: This treatment can be temporary or permanent. If temporary, it may take just a few minutes, or it can last several hours or days. You will stay in a room designed for the procedure. Your care team will limit exposure to others. If LDR treatment is permanent, the implants may be placed in your body during surgery. You may stay in the hospital overnight or for a few days to recover. The implants slowly release radiation over a few weeks or months.  

What cancers is it used for?

  • Eye cancer 
  • Prostate cancer 
  • Head and neck cancer 
  • Cervical cancer 
  • Endometrial cancer 
  • Vaginal cancer 

Selective internal radiation therapy (SIRT)

What is it? Also called radioembolization, this therapy targets liver tumors by sending radioactive beads through your blood vessels directly to the cancer. It is used to treat tumors that can’t be removed through surgery.

How is it delivered? Most of the blood supplied to liver tumors comes from a blood vessel called the hepatic artery. Your doctor inserts a thin, flexible tube called a catheter into the artery, then uses it to send radioactive beads to the tumor. Because the beads emit radiation only over a short distance, they affect just the tumor, avoiding damage to the liver and other tissue.

What cancer is it used for?

  • Liver cancer 

Systemic radiation therapy

What is it? Systemic radiation uses medications with radioactive materials to distribute radiation to your whole body. These radiopharmaceuticals travel through your bloodstream and attach themselves to cancer cells. They give off small amounts of radiation that kills the cancer. In some cases, they may be given along with external radiation therapy.

How is it delivered? Radiopharmaceuticals can be taken in pill or liquid form. They also might be given in an IV. Some radioactive material will remain in your system during treatment, so you may stay in a special hospital room for a day or two to protect others from exposure. Everyone’s bodies eliminate radiation at different rates. Your doctor can help you take steps to protect friends and family in the days after you go home.

What cancers is it used for?  

  • Thyroid cancer 
  • Bone cancers 
  • Prostate cancer 
  • Non-Hodgkin lymphoma 

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.


Parking is free for patients and their visitors.

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Kohler Pavilion, fourth floor
808 S.W. Campus Drive
Portland, OR 97239
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15700 S.W. Greystone Court
Beaverton, OR 97006
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