Pronunciation: (RAY-dee-oh-NOO-klide)

An unstable form of a chemical element that releases radiation as it breaks down and becomes more stable. Radionuclides may occur in nature or be made in a laboratory. In medicine, they are used in imaging tests and in treatment. Also called radioisotope.

Source: NCI Dictionary of Cancer Terms

2007-12-14 Date last modified: 2008-01-10