Radiation Therapy Treatment Techniques
External Beam Radiation Therapy
IMRT, or intensity modulated radiation therapy, is a technique which uses the 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 changed to suit the shape of the tumor. This directs the prescribed amount of radiation to each part of the tumor, and minimizes exposure to the surrounding healthy tissue. IMRT treatments are typically delivered daily for 10-20 minutes over a 6-8 week time 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 tumor, or target, and the surrounding tissues. The scans typically are produced by computed tomography (CT scan), magnetic resonance imaging (MRI), or positron emission tomography (PET scan).
VMAT, or volumetric arc therapy, is an advanced form of radiation treatment introduced by Varian. VMAT uses special software and an advanced linac to deliver treatments quickly. With conventional treatments the linac makes repeated stops to treat the tumor from a number of different angles. With VMAT, the treatments can be delivered to the entire tumor in a single, brief, smooth rotation.
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 5 sessions. Despite the use of the word "surgery" in its name, it 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 5 sessions.
Internal Radiation Therapy - Brachytherapy
Brachytherapy, which is also called internal radiation therapy, treats cancer by placing radioactive seeds directly into or next to the target area. The technique has proven to be a highly successful 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.
Low Dose Rate (LDR) Brachytherapy
LDR uses tiny, 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 appreciable amounts of radiation.
High Dose Rate (HDR) 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.
