Global trends in the use of medical radioisotopes and the vital role of research reactors in their production

Radioisotopes have been used in healthcare since almost eight decades, evolving continuously with advancements in bio-medical sciences as well as computation and imaging technologies. While the initial use of medical isotopes was primarily for therapeutic purposes (Cobalt-60 in teletherapy and Iridium-192 in brachytherapy; and Iodine-131 and Phosphorus-32 in in-vivo nuclear medicine), the last few decades of the last century witnessed a steep growth in diagnostic nuclear medicine with the advent of the most widely used medical radioisotope, Technetium-99m and its versatile nature, earning it the name 'Work horse of nuclear medicine'. The new millennium witnessed a paradigm shift with the phenomenal growth in the production and use of positron(β+) emitting isotopes, especially Fluorine-18 to provide high resolution images. Thanks to the innovations in the various related fields, nuclear medicine has a niche, unique place in medical diagnosis as well as treatment of several ailments, especially cancers. Therapeutic applications using particulate (especially β- emitting radionuclides) has witnessed a resurgence and growth in the past 2 to 3 decades, and a large number of radioisotopes have yielded excellent results, among which Lutetium-177, Samarium-153, Rhenium-188/186 and Yttrium-90 deserve special mention. In the recent years, the use of alpha emitters for therapy has gained much attention owing to the very impressive results in certain types of cancers. 'Theranostics', the use in both diagnosis and therapy, has evolved as the new approach for personalised therapy, owing to the availability of suitable radioisotopes. From the beginning, Research reactors have played a vital role in the production of radioisotopes, which is often not known to the end user. As most of the research reactors that supplied the isotopes to the world aged, long shut downs were unavoidable, leading to short supply of isotopes, bringing forth the importance of having the fleet of research reactors around the world in operation to cater to the global needs. Although radioisotope production in accelerators has seen a huge growth, it is beyond doubts that research reactors are essential for production of a huge range of important radioisotopes in large quantities and at affordable cost. (author)