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External Beam Radiation Therapy

External beam radiation therapy (EBRT) is a method that delivers beams of high-energy X-rays to a patient's tumor or abnormality from outside the body. The beams are produced by a highly advanced machine called a linear accelerator. A predetermined dose of radiation is aimed precisely at the area of the tumor or abnormal tissue to destroy the cancer cells, while sparing as much of the surrounding normal tissue as possible. External beam radiation is usually given daily and over several weeks depending on the location of the tumor.

There are several types of external beam radiation therapy, each of which is described below.

Three-Dimensional Conformal Radiotherapy (3DCRT)

3DCRT is a technique that sculpts radiation beams to the shape of a tumor. This is ideal for tumors that have irregular shapes or that lay close to healthy tissues and organs. Using specially equipped linear accelerators, we match the radiation dose to the particular dimensions of the tumor which allows delivery of a higher dose, while limiting radiation exposure to surrounding healthy tissue. This technique has been largely incorporated into Intensity-Modulated Radiation Therapy (IMRT) except that in 3DCRT the delivery of the radiation is the same across the targeted treatment area.  

Learn more about cancer programs at Smilow and our commitment to the diagnosis, treatment and care of cancer patients.

Intensity-Modulated Radiation Therapy (IMRT)

Intensity-modulated radiation therapy is an advanced form of three-dimensional conformal radiotherapy (3DCRT). This technology is used to deliver extremely conformal radiation beams to the intended target by very closely matching the radiation delivered to the three dimensional shape of a tumor. In addition, specially equipped linear accelerators and advanced software planning allows us to adjust the intensity of radiation beams across the treatment area with pinpoint accuracy so that we can deliver higher radiation doses while minimizing exposure to healthy tissues. With this greater conformity and degree of accuracy, our physicians have more treatment options for patients who had previous radiation therapy, have a recurrent tumor in the treated area, or simply need this advanced form of external beam radiation treatment.

Learn more about how IMRT combined with other therapies is being used to treat head and neck cancers at Smilow.

Volumetric Modulated Arc Therapy (VMAT)

Volumetric Modulated Arc Therapy (VMAT) Radiotherapy Technology is an advanced form of intensity-modulated radiation therapy (IMRT). Unlike conventional IMRT treatments, during which the machine must rotate several times around the patient or make repeated stops and starts to treat the tumor from a number of different angles, VMAT delivers the radiation dose to the entire tumor in a 360-degree rotation, typically in less than two minutes. VMAT uses special software and an advanced linear accelerator from to deliver IMRT treatments up to eight times faster than what was previously possible.

Image-Guided Radiotherapy (IGRT)

IGRT refers to the use of imaging technology before or during radiation therapy to ensure the most precise radiation treatment is delivered. This technology is incorporated into your daily treatment because areas of the body are continuously moving. Radiation therapy machines equipped with this specialized technology allow the physicians to take images to reference certain details about your tumor before and during treatment. By comparing these images to the reference images taken during simulation, we can ensure accurate positioning and make any daily adjustments required. IGRT enhances the ability to precisely target the tumor and protect nearby normal tissue by minimizing exposure to radiation. For a very select few cases of IGRT small markers may be implanted near your tumor to add another layer of precision for alignment of the radiation to be delivered. These very small markers are usually placed during a separate outpatient appointment.

Stereotactic Radiosurgery (SRS) Linear Accelerator

SRS differs from conventional external beam radiation in that it uses a higher degree of highly focused, highly accurate x-ray beams to deliver a large dose of radiation in a single treatment. This is possible because of new imaging capabilities that allow precise and accurate setup SRS is used to treat small brain and spinal cord tumors (benign and malignant) and certain blood vessel abnormalities. SRS is delivered via a linear accelerator with advanced hardware and software which allows the treatment to target very small lesions while minimizing dose to normal tissue.

Learn more about Brain Tumors Program at Smilow Cancer Hospital.

Stereotactic Body Radiation Therapy (SBRT)

Stereotactic Body Radiation Therapy (SBRT) uses the same principles as stereotactic radiosurgery (SRS) for the brain, but on other areas of the body. Because of the pinpoint accuracy of this technology, SBRT can deliver higher doses of radiation in fewer treatment sessions, with less risk to surrounding healthy tissue. Treatment is delivered in one to five sessions compared to five to eight weeks with other types of external beam radiation treatment. SBRT is particularly effective against small, well-defined tumors in inoperable or surgically risky locations such as the liver or lung. 

Learn more about the advances in early detection for lung (thoracic) cancer in high risk individuals and liver cancer services at Smilow.