Understanding the Technology

If you have external beam radiation therapy, the radiation comes from a machine called a linear accelerator. While you lie on a table, the linear accelerator moves around your body, sending radiation to the tumor from different angles. Depending on the machine, you might hear a buzzing sound or other noises. You can listen to music in our radiation therapy suites to help you relax during treatment.

How does radiation therapy work?

Radiation therapy uses high-energy beams or electrons to destroy cancer cells and cells that cause other disorders. When the radiation comes from a machine outside your body, it is called external beam radiation. Radiation can also come from radioactive material your doctor puts inside your body. There are many different types of radiation therapy.

At the OHSU Knight Cancer Institute, our radiation oncologists and other radiation therapy experts will use their knowledge and expertise to make sure you receive the best care available. We also use the latest technology to make radiation treatment as safe and effective as possible.

The machines we use

The OHSU Knight Cancer Institute uses the latest radiation therapy technology so you receive the best cancer treatment available. Our machines include:

Varian Trilogy System

The Varian Trilogy system uses Real-time Position Management® to track tumors during external beam radiation therapy. Information from this system keeps the radiation beam directed at the tumor, avoiding healthy tissue. The Trilogy system can be used with many types of radiation therapy, including image-guided radiation therapy (IGRT), intensity-modulated radiation therapy (IMRT), 3D conformal radiation therapy, stereotactic radiosurgery, and stereotactic body radiation therapy.

OHSU KCI Brain Varian Trilogy in use.

Novalis Tx system

The Novalis Tx system is the most advanced treatment system for brain tumors and head and neck cancer. It can deliver radiation from any direction. The treatment bed can also be adjusted up and down, right and left and side to side. Because the Novalis Tx is so precise and adjustable, radiation therapy can be more comfortable than with other types of equipment .

Learn more about Novalis Tx

OHSU KCI Brain Novalis treatment machine.

Intrabeam system

OHSU KCI Intrabeam TechnologyThe OHSU Knight Cancer Institute is one of just a few oncology centers in the United States using the Intrabeam system to treat breast cancer. After surgery, your doctor places the Intrabeam applicator where the tumor was. The Intrabeam system sends radiation to the area, destroying cancer cells. Some patients have Intrabeam treatment instead of coming to the radiation therapy center for external beam radiation treatments .

Learn more about the Intrabeam system

Mobetron system

The Mobetron is a device is designed to deliver a precise dose of radiation during surgery, immediately after your tumor is removed. Because Mobetron therapy is so precise, treatment takes less time and causes fewer side effects than external beam radiation. It can lower the overall dose of radiation your body receives. The OHSU Knight Cancer Institute is the only cancer center in Oregon and Southwest Washington to offer Mobetron therapy.

Learn more about the Mobetron system

What is the difference between external beam radiation therapy and brachytherapy?

External beam radiation therapy

External beam radiation therapy comes from a machine outside the body. This is the most common type of radiation treatment.

Types of external beam radiation therapy include:

External beam radiation therapy is used to treat many different types of cancer.

There are different types of treatment available at OHSU KCI.


Brachytherapy is radiation therapy given by placing radioactive material inside a tumor or close by. A type of brachytherapy called seed implantation is used to treat some people with prostate cancer. Some gynecological cancers (cancers of the female reproductive system) and eye cancers are also treated with brachytherapy.

Learn more about brachytherapy