Radioisotopes are radioactive isotopes. So what is an isotope? An isotope is a version of an element that has different number of neutrons. For example, "standard" carbon (the most abundant isotope) is carbon-12, which has 6 protons (particles with a positive charge) and 6 neutrons (particles with no charge). The carbon isotope used in carbon dating artifacts is carbon-14. The difference between this carbon and the more abundant carbon-12 is that carbon-14 has 8 neutrons instead of 6. Several elements have many isotopes, with some being stable and others being unstable, readily decaying or decaying over a period of time. The unstable isotopes tend to be radioactive, and are made artificially or from the decay of larger elements such as uranium and thorium. There are currently over 1800 known isotopes, and many of those have useful applications in medicine and other fields.
Radioisotopes become stable by emitting particles such as alpha particles, beta particles, or positrons from their nuclei. These particles are accompanied by an emission of energy. This overall process is known as radioactive decay. In medical processes, radioisotopes can be introduced into the body through some method, and can be used as a tracking device as it goes through the body and does its business. They can also be used in radiation therapies as a radiation source.
Several different elements' isotopes are used, depending on what is trying to be accomplished. One of the less common is cobalt. Cobalt is a transition metal that as an atom is about 59 times heavier than hydrogen, the lightest element. The only naturally occurring isotope is cobalt-59, and there are ten radioactive isotopes. One of the isotopes of cobalt that is used in medicine is cobalt-60. This is a radioactive metal that is usually employed in radiotherapy. As it undergoes decay, it emits two gamma rays, which supply radiation for killing off cancer cells. This method has been in use for over fifty years. Cobalt-60 is also used in the sterilization of medical supplies and medical waste. In addition, it is used in the Schilling test, which helps to determine if the body is properly making and utilizing vitamin B12. One of the advantages to cobalt-60 as a medical isotope is that its half-life (the time it takes for half of the sample to decay) is 5.26 years, whereas many others, such as molybdenum-99, have half-lives of only a few days, which makes it more difficult to stockpile a supply.
Another isotope of the metal, cobalt-57, is used in medical tests, such as the Schilling test (cobalt-58 is also used in this test). It is also used as a radiolabel for the uptake of vitamin B12 and for the study of anemia related to deficiency of this vitamin. It can also be used in labeling to help estimate organ size and location. Cobalt-57 imaging has also been used in the past as a technique for evaluating tumors of the head and neck. It has been found that this isotope delivers the smallest radiation dose of all the cobalt isotopes.
The use of manufactured atoms and radioisotopes continues to grow as a branch of the medical field. Cobalt's isotopes are just a few of the many radioisotopes in use. As the knowledge of the atom continues to grow, the usefulness of variations of atoms should expand as well.