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Since the development of nuclear medicine in the 1950s, radioisotopes have been used extensively in medicine for one of two purposes. Some, such as 'Technetium' allow the non-invasive exploration of body functions and structures, whilst other radioisotopes are used to treat diseases, primarily cancer, by the destruction of cancer cells.

Cobalt-60 is a radioisotope used to destroy cancer cells due to the emission of high energy gamma rays. Cobalt-60 is considered a radioisotope because it contains an extra neutron from the normal cobalt nucleus (Cobalt-59). The result of this extra neutron is instability in the nucleus of the cobalt atom which results in its radioactive decay.

The decay of Cobalt-60 releases a low energy election (315keV) and two high energy gamma rays (1.33 MeV). These gamma rays can be focussed into a beam during radiotherapy and can then be channelled into cancerous regions of the body. The basis of radiotherapy is that more cancer cells are killed than normal body cells.

This is because during the gamma treatment, both normal and cancerous cells will be exposed to the harmful radiation, despite the emphasis on targeting only cancerous cells. Consequently, radiotherapy involving an external irradiator such as Cobalt-60 inevitably results in some body degradation, which is evident in symptoms such as hair loss, pallid skin and low energy.

As we move into the 21st century, the use of the radioisotope Cobalt-60 has been limited in the use of medicine in favour of X-rays and particle accelerators. The reason for this is that Cobalt-60 is very flaky, and easy disintegrates into a fine dust. This can make radiation protection very difficult. Additionally, Cobalt-60 has a very high half-life' which is the time taken for half of the radioisotope to form stable compounds. This means that Cobalt-60 remains radioactive for a very long time (over 5 years) and this leads to difficulty with safe disposal of used radioisotope.

In conclusion, the radioisotope Cobalt-60 has been used extensively in radiotherapy, especially from the 1950s until the onset of the 21st century. During this time, it has helped control countless cases of cancer, and hence saved the lives of millions. As we move into the future, it has been replaced by safer and more effective radioisotopes and sources of radiation, but has nonetheless remained immortalised as one of the largest medical breakthroughs of all time.

Learn more about this author, Anthony Khoo.
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