NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 8,036 terms related to cancer and medicine.

ionizing radiation
(I-uh-NY-zing RAY-dee-AY-shun)
A type of high-energy radiation that has enough energy to remove an electron (negative particle) from an atom or molecule, causing it to become ionized. Ionizing radiation can cause chemical changes in cells and damage DNA. This may increase the risk of developing certain health conditions, such as cancer. Ionizing radiation can come from natural sources, such as radon and cosmic rays (rays that enter the earth's atmosphere from outer space). It may also come from medical imaging equipment, such as x-ray, CT scan, or PET scan machines. Nuclear power plant accidents and atomic weapons also release high levels of ionizing radiation. Being exposed to very high doses of ionizing radiation can cause immediate damage to a person’s body, including severe skin or tissue damage, acute radiation sickness, and death.