Australia’s National Medical Cyclotron (NMC) - the electrical machine that has given doctors the power to
accurately diagnose thousands of Australians - is celebrating ten years of operation.

Operated by the Australian Nuclear Science and Technology Organisation (ANSTO) in Camperdown, Sydney, the Cyclotron has experienced continuously increasing demand for the radiopharmaceuticals it produces since it was officially opened by Governor General, Bill Hayden in 1992. Cyclotrons belong to a class of machine called particle accelerators. Most homes have at least one particle accelerator in them as part of a television picture tube or computer monitor.

The large majority of radiopharmaceuticals in Australia continue to be produced by the HIFAR research reactor at Lucas Heights, however demand for both reactor and cyclotron produced radiopharmaceuticals is increasing.

Nuclear reactors produce radioisotopes by adding an extra neutron into the atoms of the respective elements - that is, they are neutron-rich isotopes, and it is the excess of neutrons that makes the isotopes radioactive. On the other hand, cyclotrons bombard atoms with different particles (for example protons or deuterons) to produce isotopes that are deficient in the number of their neutrons. In this case it is the neutron deficiency that makes the isotopes radioactive.

This is why reactor radioisotopes cannot generally be made by a cyclotron, and cyclotron-produced radioisotopes cannot generally be made in a reactor. Reactor produced and cyclotron produced radioisotopes are complementary in nature and both are required to provide the range of diagnostic medical products needed to service Australia’s health needs.

The NMC supplies a high portion of Australia's needs for diagnostic medical radioisotopes such as gallium-67, thallium-201 and iodine-123. Gallium-67 detects soft tissue tumours and hidden infections, and is injected intravenously to assess cancers in the bronchi, lymph nodes, spleen (Hodgkin's Disease) and malignant melanoma. It is also used to track certain solid tumours in children and to assess the effectiveness of treatments.

Thallium-201 is used in the diagnosis of coronary artery disease, diagnosis of tissue viability (which helps the cardiologist judge the most appropriate course of therapy) and is the most powerful indicator of prospects for patient management over a broad range of coronary diseases.

Iodine-123 is used in SPECT applications to monitor thyroid function and detect adrenal dysfunction.

Another cyclotron-produced radiopharmaceutical experiencing increasing demand is Fluorine-18 deoxyglucose (FDG), a radioisotope with a 110-minute half life.

ANSTO is one of only a small number of manufacturing sites around the world with approval to produce FDG, which is the subject of some intensive medical studies into better imaging methods.

Operations Manager at the NMC, Doug Arnott said there have been considerable improvements made to the Cyclotron’s facilities over the last decade. "This is a considerable achievement, given that we’re one of very few facilities in the world producing the range and quantity of products we produce, with a single cyclotron, operating more than 100 hours per week," he said. "The Cyclotron Engineering, Production and Quality Control teams have worked hard over the years to hone their skills and do it better. We’ve been able to keep up with a steadily increasing demand for our main products. As an example, in 1993 our production of thallium-201, which is used for heart scans, was at the level of 60 GBq a week, today we supply around 250 GBq. In general, we produce more material, process it more efficiently, perform quality control faster and deliver more efficiently!"

There are three cyclotrons in Australia - the medium-power National Medical Cyclotron in Sydney, and two small ‘baby’ PET cyclotrons in Melbourne. A new baby PET cyclotron is planned for Perth - in April or May 2002, the WA state government issued a Request for Tender to site a cyclotron at Sir Charles Gairdner Hospital. PET cyclotrons may also be built in some other capital cities in the coming years.

What’s PET? Positron emission tomography. In a nutshell, this is the cutting-edge of diagnostic nuclear medicine. It is limited in its range of clinical applications, though there is potential to expand. PET uses short-lived isotopes, all (or almost all?) produced in cyclotrons. The baby cyclotrons cost roughly a few million dollars.

Because of their size, baby cyclotrons could not produce other important isotopes used in nuclear medicine such as technetium-99m. (Using larger cyclotrons to produce Tc-99m is technically feasible and has been demonstrated but there is no large-scale routine production - needs further R&D to scale-up demonstration work.)

To supplement short-lived PET radioisotopes produced on site, radioisotopes with a longer half life or those that can be milked from a longer-lived parent can be purchased commercially from reactors or larger cyclotrons.

Comparable countries are much further advanced in PET technology than Australia, esp. the US.

In addition to using cyclotrons to produce isotopes now produced in reactors, another option is using (different) cyclotron-produced isotopes to replace reactor-produced isotopes. For example, PET using fluorine-based FDG produced in cyclotrons is exceptionally useful for diagnosis and can be used in place of reactor-produced Tc-99m in some circumstances. Systematically pursuing R&D to expand the use of FDG in place of Tc-99m is the sort of forward-looking work that doesn’t get the government support it should, although there are some commercial interests pushing PET and baby cyclotrons. Many different uses for Tc-99m, it is used in about 75% of nuclear medicine procedures - its important role in nuclear medicine won’t come to an end any time soon even with progress with FDG PET etc.

Another development is modifying conventional cameras so they can use FDG, this is called fluorodeoxyglucose single photon emission computed tomography or FDG SPECT for short. As I understand it, this is a half-way option - it makes FDG studies more widely available but is not as good as dedicated (and more expensive) PET facilities. FDG SPECT also has the potential to reduce reliance on reactor-produced isotopes and this may already be happening to some extent.

More information on nuclear medicine, PET etc.:

Nuclear Medicine on the Internet <nucmed.auntminnie.com>

US Society of Nuclear Medicine / Journal of Nuclear Medicine
<www.snm.org>
<www.snm.org/about/news_order.html>

Examples of successive governments underfunding of cyclotrons/PET and overfunding of ANSTO at:http://www.geocities.com/jimgreen3/pet.html

This is PhD section with more info on PET, FDG etc., dated for a fast-moving field but still relevant:
http://www.uow.edu.au/arts/sts/pgrad/phdthesis/JimGreen/futureappend.html#anchor1671758