After nearly a decade of looming shortages, supplies of critical medical isotopes have stayed stable, but vulnerabilities remain, explained experts during a side event at the IAEA’s 61st General Conference today. The event focused on Molybdenum-99 (Mo-99) and its daughter isotope Technetium-99m (Tc-99m), the most common radioactive isotopes used in medical diagnosis, and covered the current supply situation, new alternatives for their production and the role of the IAEA. Watch the Facebook Live recording of the event.
“Following the unforeseen disruptions in supplies, we assessed the likely supply situation in 2014 and, at that time, the risk of shortages was expected to get worse as of 2017,” said Kevin Charlton, a medical isotope expert and analyst from the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD). “But now it’s 2017, and we can report that positive actions taken by the players in the supply chain have increased the production capacity of existing facilities, and the supply situation is now more stable.”
Mo-99 is the parent isotope of Tc-99m, the most widely used radionuclide for medical imaging. Tc-99m is extracted from Mo-99 using a Mo-99/Tc-99m generator device and then specific, targeting molecules can be readily labelled with Tc-99m to create specialized medical drugs called radiopharmaceuticals. These drugs are used on patients for diagnostic procedures related to health conditions like cancer and cardiovascular diseases. Hospitals need a constant supply of these isotopes to provide patients worldwide with more than 30 million nuclear medicine scans each year.
Both Mo-99 and Tc-99m have to be used quickly once they are produced. Within hours of production, Mo-99 is transported to a generator production facility and then on to hospitals where specialists extract Tc-99m on site. Within 24 hours of using Tc-99m radiopharmaceuticals, almost 94% of it has already left the patient’s body. While this short lifespan keeps the dose of radiation low and safe for people, it means both radioisotopes have to be produced constantly to meet global demand.
For decades, Mo-99 had primarily been produced by a limited number of research reactors. However, since 2007, these aging reactors have required more maintenance, and some have faced unexpected shutdowns. This led to supply disruptions with significant shortages particularly in 2009 and 2010.
In response to the crisis, medical practitioners implemented policies to increase efficiency in how these isotopes are used for medical scans, which helped to lower demand. This lower demand could be successfully met by the remaining suppliers who have progressively worked to increase their production capacities. This has helped to maintain supplies despite the planned closure of a number of important facilities. In parallel, scientists have worked to develop ways to increase production capacity by using other technologies.
“Supply conditions have improved and are now steady,” Charlton said. “While the current supply chain should be sufficient until at least 2022, the situation still requires careful and well-considered planning for the foreseeable future.” This includes monitoring supplies from alternative technologies as they enter the market, as well as monitoring the price changes needed to ensure a long-term, economically sustainable model for production, he added.
New methods to keep supplies coming
Scientists continue working on new production methods to maintain supplies with an aim to reach commercial-scale production. Many of these alternative methods focus on innovative ways to complement production of Mo-99 with smaller, regional operations, and some directly produce Tc-99m.
One promising method highlighted during the event involves linear accelerators and the naturally occurring Molybdeneum-100 (Mo-100) to produce Mo-99 and consequently Mo-99/Tc-99m generators. The method is based on what is called a photonuclear reaction, which, in this case, is created using the linear accelerator’s high energy X-rays causing the Mo-100 to lose a neutron, converting it into Mo-99.
Accelerators could be a suitable option for countries that wish to install a facility for the sole purpose of radioisotope production. These machines can be turned on and off to operate as needed, and they do not produce radioactive waste, said Kennedy Mang’era, Chief Operating Officer of Canadian Isotope Innovations. “The main advantage of this approach is that it uses linear accelerators, which are relatively easy to establish.”
Although the new method is economically competitive, it has some challenges and risks, Mang’era explained. For example, the Mo-99 produced is of low specific activity, rendering it unsuitable for conventional alumina based Tc-99m generators and making it necessary to improve current generators or develop new ones, he added.
An IAEA coordinated research project launched this year will develop this method further and result in guidelines for using it to produce Mo-99. The project will also focus on optimizing available Mo-99/Tc-99m generators and develop new ways to separate Tc-99m from Mo-99, such as using new adsorbents, or electrochemical methods.
Accurate data, accurate doses
Readily accessible nuclear data is paramount to developing these alternative Mo-99/Tc-99m production methods, explained Katie Gagnon, Global Research Alliance Manager from the Cyclotrons and TRACER center at GE Healthcare in Sweden. “As Tc-99m is used clinically, access to reliable and accurate nuclear data allows scientists to understand and optimize the production yield and quality of this important isotope.”
Collecting and coordinating nuclear data and supporting these projects on alternative methods are just a few of the ways the IAEA has been helping experts worldwide, explained Joao Osso, Head of the IAEA’s Radioisotope Products and Radiation Technology Section. Others include training courses, technical meetings, publications, and major conferences, as well as close collaboration with other scientific institutions.
“Countries have worked with the IAEA for decades to research and develop ways to produce and use medical isotopes,” said Osso. “Several projects coordinated across the IAEA are now underway and aim to continue refining current methods and developing new, innovative approaches to ensuring life-saving isotopes keep reaching the people who need them.”
"While the current supply chain should be sufficient until at least 2022, the situation still requires careful and well-considered planning for the foreseeable future."
