Three Nuclear Isotopes in Medicine and Industry

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Technetium-99m, or Tc-99m is the world’s most widely used medical nuclear isotope for diagnostic imaging. In its name, the ‘m’ of 99m describes indicates the metastability of the particular radionuclide. This metastability is the ability for a certain energy state of the radionuclide to exist indefinitely until, whether spontaneously or because of outside factors, it changes to the much more stable Tc-99, with a half-life of over 210,000 years. Technetium-99m is used as a radioactive tracer which can be taken orally or injected and can be used to detect internal blockages with the use of a gamma camera. With such a short biological half-life of one day, Tc-99m is well suited for scanning procedures that can collect data quickly and doesn’t expose the patient to much radiation. Unfortunately this short half-life means that the use of Tc-99m is fairly limited to diagnostic uses and is unsuitable for therapeutic use. The short half-life also complicates transport due to the logistical problems with long journeys; this is solved by transporting Molybdenum-99 and extracting the Tc-99m in situ. The transport of Mo-99 rather than Tc-99m is also because where Technetium decays with gamma radiation, the Molybdenum decays with easier to shield beta decay. Tc-99m use in hospitals is convenient because of the frequency of the gamma rays it emits. At 140 keV it’s a similar frequency as used by conventional X-ray equipment and so is easy to retro-fit. As with any radioactive material, there are risks that come with the use and handling of Tc-99m. With the standard quantities to be administered being between 11 to 30 mCi (millicuries), a patient will be exposed to around 10 mSv (microsieverts) which is equivalent to around 500 chest X-rays. With this low level of exposure does come with a 1 in 1000 lifetime risk of developing a cancerous growth or leukaemia.

Iodine-131 is a commonly used nuclear isotope almost exclusively used in the medical field for treatment requiring...
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