London: A global shortage of medical isotopes, used in more than 80 percent of heart and bone scans and in detection of cancer, will hamper diagnostic examinations over the coming weeks.

Medical isotopes are small quantities of radioactive substances used in the imaging and treatment of disease. They are delivered directly to the site of diseased cells and can be tracked by imaging equipment.

Hospitals in Britain are receiving less than 50 percent of expected supplies and rations are expected to drop still further in the coming weeks, wrote Alan Perkins and colleagues from the British Nuclear Medicine Society BNM.

According to the European Association of Nuclear Medicine, hospitals are already limited to only 20 percent of normal nuclear medical activities.

Currently Europe's three isotope production reactors are all shut down for maintenance and European producers only have enough radioisotopes to last until on Monday.

In addition, other reactors in Canada and South Africa have also been temporarily closed, leaving just the Australian reactor which, according to the authors, does not have enough potential to significantly increase supply to the world market.

The closure of the Canadian reactor for two months in 2007 for safety reasons affected over 50,000 patient examinations in the US.

The authors pointed out that this is not just a short term emergency. Most of the commercial reactors are around 40 years old and new production capacity is urgently needed to meet the increasing demands of isotopes for research, diagnosis and treatment.

They warned that urgent global investment in new reactor facilities is essential or these problems will continue and it will be the patients that suffer.

The report appeared in the online version of the British Medical Journal on Saturday. IANS