Isotope Shortage Hinders Nuclear Medicine
It was the worst news that the nuclear-medicine community could receive when, on August 12, Atomic Energy of Canada Ltd (AECL), Chalk River, Ontario, announced that the National Research Universal (NRU) reactor would remain shut down until at least January 2010. The 51-year-old reactor, which has been inoperative since May owing to a heavy-water leak, needs repair in at least nine areas, according to the AECL. The loss of the NRU reactor had already created a shortage of medical isotope technetium Tc 99m; when another reactor in the Netherlands was shut down on July 18, US supply of the radionuclide became severely limited.
“As physicians on the front line, we want the most appropriate test to answer the question at hand in as timely a manner as possible. There are only a handful of these reactors around the world, and they’re all aging. We’re having this problem now, we’ve had it before, and we will have it again in the future.”--Mylan Cohen, MD
Mylan Cohen, MD
Mylan Cohen, MD, president-elect of the American Society of Nuclear Cardiologists, characterizes technetium as “the workhorse of nuclear medicine.” The radionuclide, a product of the decay of molybdenum 99, is used in more than 40,000 imaging procedures daily in the United States.¹ “Technetium, when combined with various organic molecules, is used to target a number of organs to evaluate disease states,” Cohen says. “It’s used extensively in cardiology to evaluate blood flow to the heart, and it is also used to image cancer patients.” Technetium has attained its workhorse status in nuclear medicine partly because of its short half-life (just six hours), which minimizes the dose of radiation received by the patient. That half-life is also a liability, preventing hospitals and imaging centers from stockpiling the isotope for future use. “This shortage points to the need for the United States to have a viable solution for future shortages, such as its own reactor,” Cohen says. Rationing and Work-arounds The very limited supply of technetium currently available to physicians in the United States has to be rationed carefully, Cohen says. “A trickle of technetium is coming from other reactors worldwide, but the supply is really scaled back. We have to pick and choose which patients will get it,” he notes. “It has a huge impact on the quality of the images.” For nuclear cardiology, Cohen says, the most common substitution for technetium is thallium, which is cyclotron produced and has been widely used in the past. “Although it’s a well-validated radionuclide, there are a lot of characteristics of thallium that make it less preferable to use than technetium,” he explains. “It has a lower energy, so the images that we get with thallium aren’t as crisp.” Using thallium can also lead to workflow issues, Cohen notes. “Thallium redistributes, so after you inject it, it goes to the heart, and then it moves around,” he says. “Technetium sticks to the myocardium like glue. Cardiac imaging with thallium means you have to alter your schedule to ensure that patients are imaged very quickly after injection.” For patients with cancer, technetium is commonly used to image bone tumors or to locate the lymph node nearest to a breast tumor for biopsy. The alternative to using technetium to image breast cancer is injecting a dye, which is not as effective at pinpointing the node.¹ In some cases, PET with fludeoxyglucose F 18, also cyclotron produced, is being used for bone scintigraphy, but as Cohen says, “Alternative modalities aren’t always available in rural states like Maine. PET is highly sophisticated, and generally only offered in urban tertiary care centers.” One factor that helps determine which patients get technetium is body weight, Cohen says. “Because technetium is a higher-energy radionuclide, it has higher penetration in larger patients. If we have a very large patient (over 250 pounds, which is not a rare occurrence in the United States), we may try to image that person with technetium.” In the meantime, Cohen says, some patients might get stress ECGs instead of technetium stress tests. “There are alternative modalities for both patients with cancer and patients with heart disease, but I think what you try to do, as a physician, is obtain the appropriate test to answer the question at hand in the best fashion possible,” Cohen says. “The alternative to nuclear medicine can’t always do that. The shortage of technetium has meant that some patients who should have exams aren’t getting them, and that means delay in diagnosis and appropriate care.” In those cases where no adequate substitute for technetium is available, exams must often be delayed or rescheduled, leading to workflow problems. Many hospitals have been forced to schedule tests at night or on weekends to accommodate increasingly rare shipments of the isotope before they decay beyond usability. Because the radionuclide is in such high demand, its cost has also increased by 20% to 30%.² No Long-term Solution—Yet Cohen emphasizes that a long-term solution for technetium production is needed. “There’s a clear need for a reactor here in the United States,” he says, echoing the words of many in the nuclear medicine community who have dealt with three shutdowns of the Canadian reactor in the past 18 months. “The issue is cost.” In July, Rep Edward Markey (D–MA) issued a clarion call to the House of Representatives, calling the current shortage “a crisis in nuclear medicine.” Markey, who is chair of the House Energy and Commerce Committee’s Energy and Environment Subcommittee, cosponsored a bill, with Rep Fred Upton (R–MI), that would authorize $163 million in funding for the establishment of new US production facilities over the next five years. The American Medical Isotopes Production Act of 2009 (HR 3276) was referred to the House Energy and Commerce Committee. In the meantime, the White House is coordinating efforts with the Nuclear Regulatory Commission, the FDA, and the Department of Energy to pinpoint potential new sources of technetium, including a government-owned reactor at the Oak Ridge National Laboratory in Tennessee that could potentially be outfitted to extract molybdenum. Officials warn, however, that the effort could take months. “As physicians on the front line, we want the most appropriate test to answer the question at hand in as timely a manner as possible,” Cohen says. “There are only a handful of these reactors around the world, and they’re all aging. We’re having this problem now, we’ve had it before, and we will have it again in the future.” Cat Vasko is editor of and associate editor of Radiology Business Journal.