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Thursday, September 16, 2010

Global isotope shortage

At a recent National Meeting of the American Chemical Society, Robert Archer of the National Isotope Development Center led a team of scientists in identifying a global isotope shortage. This is already having implications in the medical community and beyond.

Isotopes are chemical elements with varying numbers of neutrons. For example, carbon has an atomic number of 6, meaning it normally has 6 protons and 6 neutrons. This type of carbon is known as carbon-12. However, carbon atoms can have 7 or even 8 neutrons (carbon-13 and carbon-14 respectively). Among those isotopes, carbon-14 is radioactive, meaning that it decays in a specific amount of time, whereas carbon-12 and carbon-13 are stable and will not decay.

Radioactive isotopes (radioisotopes) are particularly useful in medicine. They are used to both diagnose and treat a variety of illnesses, most notably cancer. In particular, eight out of ten procedures rely on one specific radioisotope: technetium-99m. This element has a half-life of only six hours. This means that in six hours, half the radioactivity that was injected into the body is gone. In twelve hours, 75% is gone, and in 48 hours there is less than 1% remaining. In other words, all traces of radioactivity are quickly cleared from the body.

One consequence of its short half-life is that technetium-99m can’t be stockpiled but must be constantly manufactured and rushed to waiting hospitals. Unfortunately, the main production site for technetium-99m and other important radioisotopes is the Chalk River facility in Ontario Canada, a facility that has been shut down since 2009.

Researchers are hoping that Chalk River will reopen soon, but in the meantime, doctors have been scrambling to come up with other, often less than ideal, treatments for their patients. The shortage has also called attention to the fact that less than 15% of the isotopes used in U.S. hospitals are produced domestically.