There are two broad categories of radiation therapy; both are designed to target the tumor precisely while minimizing exposure to the surrounding, healthy 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 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 / RapidArc can deliver the dose to the entire tumor in a single rotation — in less than two minutes.
IMRT, or intensity modulated radiation therapy, 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 daily for 10 to 20 minutes over a six to eight week period.
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).
SRS, or stereotactic radiosurgery, is a technique that is most commonly used for tumors in the brain or spinal column. Unlike IMRT, SRS is typically delivered in a maximum of five sessions using higher doses of radiation with each session. Despite the use of the word "surgery" in its name, SRS does not involve removing the tumor with a surgical blade. Instead, a focused high-intensity beam of radiation is used to target the tumor.
SBRT, or stereotactic body radiation therapy, is a very similar technique to SRS, but is used for targets that are outside the brain and the spine. SBRT is most commonly used for targets in the lung, liver, pancreas and kidney, and is typically delivered in a maximum of five sessions.
Brachytherapy (Internal Radiation Therapy)
Brachytherapy treats cancer by placing tiny radioactive seeds inside the body, directly into or next to the target area. The technique has proven to be a powerful treatment option for many cancers of the prostate, cervix, endometrium, breast, skin, bronchus, esophagus, and head/neck, as well as soft-tissue sarcomas and several other types of cancer. There are two common techniques available to the physician when administering Brachytherapy: LDR and HDR.
LDR (Low Dose Rate) Brachytherapy
LDR uses sealed, low-strength radioactive seeds about the size of a grain of rice to deliver radiation to the target. These seeds are permanently implanted in the body. As the seeds emit radiation, they reduce in strength and in a few weeks no longer emit any measurable amounts of radiation.
HDR (High Dose Rate) Brachytherapy
HDR uses higher-strength radioactive sources (compared to LDR) to provide radiation to the target. As opposed to LDR, these sources are only implanted in the body temporarily.