proton beam radiation therapy
(PROH-ton beem RAY-dee-AY-shun THAYR-uh-pee)
A type of radiation therapy that uses streams of protons (tiny particles with a positive charge) that come from a special machine. This type of radiation kills tumor cells but does not damage nearby tissues. It is used to treat cancers in the head and neck and in organs such as the brain, eye, lung, spine, and prostate. Proton beam radiation is different from x-ray radiation.