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How Radiation Therapy Works

If radiation therapy is part of your treatment program, you will receive treatment in Corvallis, in the Samaritan Pastega Regional Cancer Center.

The goal of radiation therapy is to get a high enough dose of radiation into the body to kill the cancer cells while sparing the surrounding healthy tissue from damage. Several different radiation therapy techniques have been developed to accomplish this.

Depending on the location, size and type of your tumor or tumors, you may receive one or a combination of these techniques. Your cancer treatment team will work with you to determine which treatment and how much radiation is best for you.

The Samaritan Cancer Program offers state-of-the-art, high-energy linear accelerators, which are computer controlled to deliver an extremely precise radiation treatment based on each patient’s customized treatment plan. 

Each treatment plan is customized using a three-dimensional treatment planning computer that allows cancer center physicians and staff to use computed tomography (CT) images to create a 3-D model of each patient and a treatment plan that precisely conforms to each patient’s unique tumor size and location. To precisely shape the radiation beam, the cancer center uses a multileaf collimation system to deliver radiation to the patient’s tumor and shield or avoid the healthy tissue.

External Beam Radiation

During external beam radiation therapy, the most common type of radiation therapy, a beam of radiation is directed through the skin to a tumor and the immediate surrounding area in order to destroy the main tumor and any nearby cancer cells. To minimize side effects, the treatments are typically given every day for a number of weeks.

The radiation beam comes from a machine located outside of your body that does not touch your skin or the tumor. Receiving external beam radiation is similar to having an X-ray taken. It is a painless, bloodless procedure. The most common type of machine used to deliver external beam radiation therapy is called a linear accelerator, sometimes called a “linac.” It produces a beam of high-energy X-rays or electrons. Using sophisticated treatment planning software, your radiation oncology treatment team plans the size and shape of the beam, as well as how it is directed at your body, to effectively treat your tumor while sparing the normal tissue surrounding the cancer cells.

Several special types of external beam therapy are used for particular types of cancer, and your radiation oncologist will recommend one of these treatments if he or she believes it will help you.

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Intensity Modulated Radiation Therapy

For tumors that require particularly precise radiation targeting, intensity modulated radiation therapy (IMRT) is used. This advanced form of external beam radiation is especially valuable in treating tumors that are situated among healthy tissues or critical organs.

IMRT is a specialized form of radiation therapy that allows radiation to be more exactly shaped to fit your tumor. With IMRT, the radiation beam can be broken up into many “beamlets,” and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the exact amount of radiation that is received by normal tissues that are near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, increasing the chance of a cure.

IMRT allows for a radiation beam to be so accurately sculpted to the tumor shape that it can zoom in on its target with minimal damage to surrounding tissue. The precision targeting also allows physicians to intensify the radiation to the cancerous area.

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3-D Conformal Radiation Therapy

Tumors usually have an irregular shape. Three-dimensional conformal radiation therapy (3-D-CRT) uses sophisticated computers and computer assisted tomography scans (CT or CAT scans) and/or magnetic resonance imaging scans (MR or MRI scans) to create detailed, three-dimensional representations of the tumor and surrounding organs.

Your radiation oncologist can then shape the radiation beams exactly to the size and shape of your tumor. The tools used to shape the radiation beams are multileaf collimators or blocks. Because the radiation beams are very precisely directed, nearby normal tissue receives less radiation exposure.