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Radium-223
Radium-223 (Ra-223, 223Ra) is an isotope of radium with an 11.4-day half-life, in contrast to the more common isotope radium-226, discovered by the Curies, which has a 1601-year half-life. The principal use of radium-223, as a radiopharmaceutical to treat metastatic cancers in bone, takes advantage of its chemical similarity to calcium, and the short range of the alpha radiation it emits. ==Origin and preparation==
Although radium-223 is formed naturally in trace amounts by the decay of uranium-235, it is generally made artificially,〔R.H. Larsen, and Oyvind S. Bruland, "Radium Revisited" targeting of skeletal metastases by the alpha-emitter radium-223 ()〕 by exposing natural radium-226 to neutrons to produce radium-227, which decays with a 42-minute half-life to actinium-227. Actinium-227 (half-life 21.8 years) in turn decays via thorium-227 (half-life 18.7 days) to radium-223. This decay path makes it convenient to prepare radium-223 by "milking" it from an actinium-227 containing generator or "cow", similar to the moly cows widely used to prepare the medically important isotope technetium-99m.〔
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