Medical imaging is one of the fastest growing disciplines in medicine. The development of innovative new imaging modalities and radiopharmaceuticals has improved the ability to study biological structures and functions in health and disease, and continues to contribute to the evolution of medical care. Besides the routine use of X-rays, the most common imaging techniques in current clinical practice are: computed tomography (CT or CAT), magnetic resonance imaging (MRI), ultrasound (US), planar scintigraphy (gamma camera) and single photon emission computed tomography (SPECT). The use of Positron emission tomography (PET) is less common, but is growing fast. CT and MRI scanners, ultrasound units and gamma cameras are now an essential part of clinical practice. PET and magnetic resonance spectroscopy (MRS) are also increasingly used in the management of patients with cancer and neurological disorders. Planar scintigraphy, CT, SPECT and PET make use of ionizing radiation, and except for CT, these nuclear imaging modalities make use of medical radioisotopes. SPECT/CT and PET/CT perform better than SPECT and PET respectively. Therefore the share of these hybrid modalities is increasing rapidly.
Artificially made radioisotopes, among which those for medical use, are mainly produced by research reactors. Currently more than 80% of the medical radioisotopes are produced by research reactors. The remaining isotopes are made by particle accelerators, mostly with circular accelerators (cyclotrons) and sometimes with linear accelerators (linacs), or by other methods. Production of medical isotopes is used by the nuclear industry as public relation for nuclear research reactors. The production of medical isotopes is seen as the sole purpose of the planned replacement of the Dutch High Flux reactor by the Pallas reactor, although 50 percent of reactor-time will be used for nuclear related research. Actually, such research reactors are not necessary at all for the production of isotopes. After an intense debate in Canada the Canadian government recently decided to cancel the plan for the construction of a new research reactor and to opt for isotopes production with particle accelerators. They have learnt from their mistakes in the past and have chosen for innovation and modernization. Canada should be a shining example for the rest of the world.
Radioisotopes production with cyclotrons offers many advantages over a nuclear reactor. Firstly, the volume of radioactive waste produced by cyclotrons is far less and much less hazardous than the radioactive waste of research reactors. Secondly, the production is decentralized. Cyclotrons are located hospital-based, by which the delivery of pharmaceuticals to patients is much more secured. In addition the risk of transport accidents is practically zero. Thirdly, there are no risks due to nuclear-power accidents, because there is no need for controlled chain reactions. Fourthly, there is no nuclear proliferation risk.
This report is answering the key question: Is it possible to ban the use of research reactors for the production of medical radioisotopes? A recent bulletin of the World Nuclear Association (WNA) on nuclear medicine stated: “Over 10,000 hospitals worldwide use radioisotopes in medicine, and about 90% of the procedures are for diagnosis. The most common radioisotope used in diagnosis is technetium-99m (in technical jargon: 99mTc), with some 30 million procedures per year, accounting for 80% of all nuclear medicine procedures worldwide.”1 Other sources mentions the figure 80-85%2, and the figure of 90% of all diagnostic procedures in Europe in 20083 (European Association of Nuclear Medicine). Today, technetium-99m (99mTc) can be manufactured easily by using cyclotrons. Besides technetium-99m there are also other popular medical isotopes that can be made with cyclotrons. At the same time radiopharmaceuticals used with PET oust increasingly the 99mTc radiopharmaceuticals currently in use. In addition, there are other accelerator-based isotopes with energies that are similar to the energies of reactor-produced isotopes, currently in use in nuclear medicine. A few isotopes that can’t be made now by accelerators can be made by sub-critical systems, such as accelerator-driven systems (ADS). The rapid development of new accelerator-based isotopes can make the use of such systems redundant in the near future.
- Radioisotopes in Medicine. 16 April 2010: http://www.world-nuclear.org/info/inf55.html
- Kahn, Laura H.; The potential dangers in medical isotope production. Bulletin of the Atomic Scientists, 16 March 2008: http://www.isotopeworld.com/filestore/Danger%20Medica l%20Isotope%20pdf.pdf
- Public Health - Radioisotopes for Medical Use http://ec.europa.eu/health/ph_threats/radioisotopes/radioiso topes_en.htm