External Beam Radiation Therapy

External beam radiation therapy, or EBRT, refers to radiation that is delivered from outside the body through a machine, often called a linear accelerator.

It carefully aims high-powered X-rays or particles directly at the tumor. The machine moves around the patient’s body. Since it does not touch the patient, it does not cause any pain.

At Northside Hospital Cancer Institute, external beam radiation therapy may include delivery through any one of the various methods below:

External Beam photo
  • Conventional Radiation Therapy – During conventional radiation therapy, one or more radiation beams are positioned around the patient to deliver the prescribed therapeutic dose of radiation to the targeted area. A team of physicians, medical dosimetrists and medical physicists work together using various forms of imaging to create a treatment plan to accurately deliver the dose where intended.

  • Intensity-Modulated Radiation Therapy (IMRT) – IMRT employs multiple small radiation beams of varying intensities to radiate a tumor with great precision. IMRT uses computed tomography (CT) images and computerized dose calculations to modulate the intensity of the radiation beams so that they conform to the tumor’s three-dimensional shape. The advantages of intensity-modulated radiation therapy include the safe delivery of higher and more effective radiation doses with fewer side effects, as well as reduced toxicity.

  • Image-Guided Radiation Therapy (IGRT) - Image-guided radiation therapy uses frequent imaging during radiation therapy to provide real-time positioning and targeting of select tumor(s). This added accuracy allows radiation to be delivered to a tumor based on its exact location in the body.

    Images are obtained of the patient while on the treatment table and in their treatment position. The treatment machine is equipped with special imaging technology that allows imaging immediately before and during the time the radiation is delivered. Using specialized computer software, the images are compared to reference images taken during simulation. Any necessary adjustments are made to the patient’s position or radiation beam in order to achieve precise and accurate treatment delivery to the treatment area while avoiding surrounding healthy tissues.

  • RapidArc IMRT - RapidArc IMRT is a type of volumetric modulated arc therapy, or VMAT, which takes conventional IMRT a step further. RapidArc delivers radiation directly to a tumor two-to-eight times faster than conventional intensity modulated radiation therapy. The treatment machine rotates 360 degrees around the patient to deliver the radiation to the tumor from multiple angles. This precision reduces the chance of tumor movement during treatment and preserves surrounding healthy tissue.
  • Stereotactic Radiosurgery (SRS) - Frameless stereotactic radiosurgery (SRS) is a highly precise form of radiation therapy that delivers focused beams with an accuracy of within one-to-two millimeters. Radiosurgery is called "surgery" because it is a one-session radiation therapy treatment that creates a similar result as an actual surgical procedure and can be used as an alternative to invasive surgery. This method allows providers to treat very small tumors, located in hard-to-reach places in shorter treatment times than traditional radiation therapy.

  • Stereotactic Body Radiotherapy (SBRT) - Stereotactic body radiotherapy employs the same principles of SRS to deliver precise radiation for treatment of malignant or benign small-to-medium size tumors in the body. SBRT is usually prescribed for one-to-five sessions over the course of one-to-two weeks.

Learn more about radiation therapy and cancer treatments.

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