Production and Supplies of 99mo: Lessons Learnt and New Options within Research Reactors and Neutron Sources Community

During the past few years, the research reactor (RR) topic has occupied the centre stage being the major factor in the crisis faced world over in the supplies of medical isotopes, molybdenum-99 in particular. It is therefore an important aspect for discussion at the quadrennial international conference on research reactors organised by the IAEA. The November 2011 IAEA conference at Rabat, Morocco comes at a time when the international availability of Mo has fairly stabilised following the excellent technological efforts in terms of repairs done in the two large reactors, in Canada (NRU) and The Netherlands (HFR), serving the bulk of Mo users. The author, who had led and coordinated the IAEA activities in addressing the various issues and extending support to international efforts and initiatives during the period until March 2011, shares in this article his professional analysis of the field of Mo production, lessons and experience from the crisis as well as the aspects to be addressed to securing sustainable supplies of both Mo and Tc in future. In line with the suggestion of the International Programme Committee of the IAEA Conference, the scope of coverage is confined to sourcing Mo and Tc from RR and other neutron sources, while accelerator-based options are not included in this article. 1. HIGH IMPORTANCE OF Tc AND Mo Diagnostic imaging forms 90% of all nuclear medicine procedures (the rest 10% being radionuclide therapy) and out of this, over 80% involve the use of 99m Tc ( 18 F accounts for 10% and all the rest 10%). With over 30 million studies reported per annum, there is practically one diagnostic imaging study performed every second using 99m Tc. The medical use of 99m Tc is growing particularly in countries expanding their healthcare programmes (25% per year), while it is expected to stabilise around 1-2% per annum in the long term. The excellent nuclear characteristics of 99m Tc enable high quality images with low radiation doses to patients. Its chemical characteristics make it very versatile for attaching to different chemical substances, so that it can be used to target different organs and lesions required for different diagnostic procedures. The two major uses of 99m Tc are in imaging myocardial perfusion in cardiac patients and imaging bone metastasis in cancer patients. Further, there are unique advantages of 99m Tc imaging in certain other cases, as for example, in differential diagnosis of prosthetic infection from loosening of prosthesis, and sentinel lymph node imaging in breast cancer patients. It is expected that all the above applications of 99m Tc will continue to be of high utility in future too, at least for the next 20-30 years. 99m Tc continues to reign as the Queen of Nuclear Medicine and 99 Mo as the Queen Mother. Fission-produced 99 Mo (f.p. 99 Mo) of very high specific activity and alumina column based 99m Tc generators have remained the mainstay in the field as ‘gold standard’. Reliable weekly availability of 99 Mo of high specific activity has thus been essential for uninterrupted supplies of 99m Tc to serve patients. The technologically demanding process management and regular weekly supply services to users have been successfully handled, thanks to excellent † Formerly Director of Division of Physical and Chemical Sciences (NAPC), IAEA, Vienna