Also known as teletherapy, external beam radiation therapy is radiation generated from an external source. In most cases, this means a linear accelerator. Mission Hospitals has two Siemens linear accelerators-the MD-2(tm) and the PRIMUS®. These particular accelerators can produce very high energy x-rays called photons for tumors deep within the body or electrons, a type of radiation used for treatment of tumors close to the surface.

In external beam radiation, the patient lies on a treatment table while these high-voltage accelerators are aimed at the designated cancer in the body. The dose is delivered to a very confined target. Patients usually receive their total dose over a period of four to eight weeks. Each daily treatment takes a few minutes and is painless.