Accelerators for Society

Medical isotopes from irradiated thorium   

From, 16 February 2015

Medical physicists in France have generated a series of medical isotopes from the irradiation of thorium-232 (Th-232). One of the products decays into thorium-226, a promising isotope for alpha radionuclide therapy, while another product is molybdenum-99 (Mo-99) – an increasingly sought-after isotope used in diagnostics.

Radioisotopes are used in medicine for both cancer therapy and diagnosis. For therapy, there is a small demand for alpha emitters – isotopes that decay with the release of a helium nucleus – since these can deliver a high dose of radiation over a very short range. For diagnosis, there is a sharply increasing demand for metastable technetium-99 (Tc-99m), a gamma-emitting isotope that is already used in upwards of 25 million examinations every year.

Tc-99m is the decay product of Mo-99, which is generated by five ageing reactors across the globe – HFR in the Netherlands, SAFARI-1 in South Africa, BR2 in Belgium, NRU in Canada and OSIRIS in France. NRU and OSIRIS, which together deliver nearly half of the world's Mo-99, are expected to cease production over the next two years, prompting several medical authorities to warn of a looming "Tc-99m crisis" – although new reactors are due to come online in France and Australia.

With the demand for alpha emitters and Mo-99 in mind, Charlotte Duchemin from the cooperative lab SUBATECH based at the University of Nantes, together with colleagues from SUBATECH and the ARRONAX cyclotron, have investigated the medical isotopes that can be generated when Th-232 – the only stable isotope of thorium – is irradiated with protons or deuterons. Read more >>



ctanguy, 2015-02-16
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