Wednesday, July 6, 2011

Medical Nuclear Supply Chains -- Where Physics Meets Operations Research for Healthcare Security

I came across an interesting presentation given to a pharmaceutical audience on medical nuclear supply chains in which my book, Supply Chain Network Economics, was cited.

This topic very much intrigued me so I began to research it.

For some background:

Each day, 41,000 nuclear medical procedures are performed in the United States using Technetium-99m, a radioisotope obtained from the decay of Molybdenum-99. The Molybdenum is produced by irradiating primarily Highly Enriched Uranium (HEU) targets in research reactors. Surprisingly, for over two decades, no irradiation and subsequent Molybdenum processing has occurred in the United States. All of the Molybdenum necessary for our nuclear medical diagnostic procedures, which include diagnostics for two of the greatest killers, cancer and cardiac problems, comes from foreign sources. Since Molybdenum-99 has a half-life of only 66.7 hours, continuous production is needed to provide the supply for the medical procedures. Thus, the US is critically vulnerable to Molybdenum supply chain disruptions that could significantly affect our healthcare security and is completely at the mercy of foreign suppliers.

Currently, about 60% of the supply of Molybdenum-99 (Mo-99) for the United States comes from a Canadian reactor, with the remainder coming from Western Europe, with its production taking place in Western Europe, the former Eastern-Bloc States, and South Africa. Worldwide, there are only 9 reactors used for the target irradiation and only 6 major processing plants. The shutdown of any of the reactors or processing plants, due to routine maintenance, upgrades, or, as occurred during 2009 and 2010, for emergency repairs, could significantly disrupt our Molybdenum supply and impact our medical facilities' abilities to perform the necessary imaging for cardiac and cancer diagnoses. The number of processors that supply the global market, however, is only four, and they are located in Canada, Belgium, The Netherlands, and South Africa. Australia and Argentina produce bulk for their domestic markets but are expected to be exporting smaller amounts in the future.

Limitations in processing capabilities restrict the ability to produce the medical radioisotopes from regional reactors since long-distance transportation of the product raises safety and security risks, and also results in greater decay of the product. The number of generator manufacturers, in turn, with substantial processing capabilities, is under a dozen. In addition, several of the reactors currently used, including the Canadian one, are due to be retired by the end of this decade, with the majority of them being between 40 and 50 years of age.

Moreover, although most of the current production of Mo-99 uses HEU targets, all producing countries, where economically and technologically feasible, have agreed, in principle, to convert to low enriched uranium (LEU) according to the latest OECD Nuclear Energy Agency (2011) report. However, although the use of LEU targets for Mo-99 production has advantages over HEU, with proliferation resistance (and, hence, enhanced global security) being a primary one, along with easier availability of the target material and also easier compliance for its transportation and processing, the negatives, nonetheless, include: a lower production yield than HEU and a greater number of targets needed to be irradiated with associated increased volumes of waste. Hence, both production and processing pressures are raised as well as waste management issues.

Since Mo-99 decays with a 66.7 hour half-life, approximately 99.9% of the atoms decay in 27.5 days, making its production, transportation, and processing all extremely time-sensitive. In fact, its production is quantified in Six-day curies end of processing denoting the activity of the sample 6 days after it was irradiated to highlight this. In addition to the time-sensitivity, the irradiated targets are highly radioactive, significantly constraining transportation options between the reactor and the processing facilities to only trucks that can transport the heavily shielded transportation containers. While the extracted M0-99 continues to be constrained by its decay, its shielding requirements are reduced, allowing for transportation by modes other than trucks, including by air.

So what did we do?

We began to identify what a rigorous medical nuclear supply chain network model for this radioisotope should include.

For example, a proper model of this critical medical nuclear supply chain, which allows for appropriate economic cost quantification, heavily emphasized by policy-makers, must include the physics-based principles of the underlying radioactivity, and must incorporate multicriteria decision-making and optimization to capture the operational and waste management costs as well as risk management, subject to constraints of demand satisfaction at the hospitals and medical facilities. Moreover, it must be sufficiently flexible and robust in order to provide rigorous solutions as the technological landscape changes. Furthermore, it should enable the redesign of the supply chain network.

With the creation of such a medical nuclear supply chain network economic optimization model, decision-makers, policy-makers, as well as, healthcare providers, would have the ability to analyze the medical nuclear supply chain vulnerabilities, and synergies, as well as to explore the relevant costs and risks. In addition, the effects on costs and risks of changes in demand, which is expected to increase given the aging population, could be assessed. Moreover, the various stakeholders including the government, the medical firms, and the hospital and imaging facilities, through such a supply chain network economic optimization model, could determine the true costs of operating the reactors, and the same holds for the processing facilities, as well as the generator manufacturing facilities. Such a transparent framework would enhance healthcare security, would allow for more accurate pricing and cost recovery, and would enable the evaluation of disruptions to the medical nuclear supply chain.

We have developed such a model, which is a generalized network model, along with an algorithm, in the paper, Medical Nuclear Supply Chain Design: A Tractable Network Model and Computational Approach, which may be downloaded at:

This paper, I co-authored with my husband, Professor Ladimer S. Nagurney, who holds a PhD in physics, so it represents a true meeting of physics and operations research.

I will be presenting this paper later this month at the Seventh Conference on Integrated Risk Management in Operations and Global Supply Chains. This year, this conference is being hosted by the Desautels Faculty of Management at McGill University, in Montreal, Canada, July 31st - August 1st, 2011. The goal of the conference is to bring together leading academic researchers and practitioners whose work strives to meet at the intersection of Finance, Economics, Operations, and Supply Chain Management. The conference web site is

According to the conference announcement, this two-day conference will feature a single track of presentations that combine technical presentations, industry practices, and discussions on relevant challenges and approaches in the topic area. There will be sixteen 90-minute sessions. Each session has two 30-minute presentations, followed by a discussant giving an overview of related research as well as facilitating a discussion with session participants. The format aims to stimulate discussion and interaction among speakers and participants.

I am very much looking forward to this conference and to presenting our work on medical nuclear supply chains.