There are two broad categories of radiation therapy; both are designed to target the tumor precisely while minimizing exposure to the healthy surrounding tissue. In the first category, external beam radiation therapy (EBRT), the radiation is usually delivered by a machine called a linear accelerator, or linac, which focuses a high-energy x-ray beam into your tumor site from outside your body. In the second treatment category, the radiation is delivered by radioactive material placed inside the body near the cancer cells — a procedure called brachytherapy (also called internal radiation therapy or implant radiation therapy).
External Beam Radiation Therapy
VMAT/RapidArc, is an advanced form of IMRT that was introduced in 2007. VMAT, or volumetric modulated arc therapy, uses special software and an advanced linear accelerator to deliver IMRT treatments up to eight times faster than what was previously possible. 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 can deliver the dose to the entire tumor in a single rotation — in less than two minutes.
IMRT, or intensity modulated radiation therapy with image guidance, uses 3-D scans of your body to guide the beams of radiation to the tumor from many different angles. At each of these angles, the intensity of the radiation is varied (modulated) and the shape of the beam is changed to match the shape of the tumor. These adjustments enable the prescribed amount of radiation to be delivered to each part of the tumor, while minimizing exposure to the surrounding healthy tissue. Treatments are typically given up to five times per week over a period of four to six weeks, with each session taking from five to 20 minutes.
IGRT, or image-guided radiation therapy, uses sophisticated computer software to analyze a series of image scans to create a detailed, three-dimensional picture of the target area and surrounding tissue, which enables your team to view the tumor and its position in your body before and during each treatment. The scans typically are produced by computed tomography (CT scan), magnetic resonance imaging (MRI), or positron emission tomography (PET scan).
Brachytherapy (Internal Radiation Therapy)
Brachytherapy (from the Greek word "brachy," which means "close") is used infrequently for head and neck cancers, although it is sometimes used to treat tumors in the oral cavity and oropharynx.
Instead of projecting the radiation beam from outside the body, the radiation is delivered by placing tiny radioactive seeds, each about the size of a grain of rice, inside the patient with a needle or catheter. The treatment session typically takes a few minutes, and then the seeds are removed. Upon removal, no radioactivity remains in the body. This type of therapy is typically repeated every day for a week. Many patients undergoing brachytherapy also receive several sessions of external beam radiation therapy.