Radiation can be given either externally or internally.  Every case is different.  Some patients require both, while others need only external radiation.  The chosen technology depends on whether a cancer is near the skin surface or deeper within the body.

In external radiation therapy, a radiation machine will direct the high-energy radiation at the cancer. The various machines used work in slightly different ways. Some are better for treating cancers near the skin surface; others work best on cancers deeper within the body. The most common types of machines used for radiation therapy are the Linear Accelerator and the Gamma Knife. The physician decides which type of radiation therapy machine is best for a particular patient.

IMRT is another form of external radiation therapy. Using computer-generated 3-D images from dozens of CT scans, intensity modulated radiation therapy, or IMRT, maps the tumor precisely, then bombards it with high-intensity radiation. This treatment allows a higher dose of radiation to be delivered to the tumor, potentially increasing the chance of a cure.  At the same time, IMRT radiation is able to avoid organs and other healthy tissue, thereby shielding them from radiation exposure.   IMRT's precision means that many hard-to-reach and "untreatable" tumors are now within range, even some that are wrapped around a patient's spine or in delicate regions of the brain.

For internal radiation therapy, or brachytherapy, the radiation source is placed inside the body.  This involves inserting an implant directly into the tumor or tumor site.  This type of therapy is sometimes used after a tumor has been removed to kill any remaining tumor cells.

One form of brachytherapy, designed especially for the treatment of breast cancer, is the MammoSite®  RTS.  The MammoSite RTS is a minimally invasive method of delivering internal radiation therapy following a lumpectomy for breast cancer to lessen the chance of recurrence.