Medical centers around the country are reporting that medical tests requiring radioisotopes, such as diagnostic tests for cancer and heart disease, are being rationed or delayed due to the extended shutdown of a Canadian nuclear reactor.
The Atomic Energy of Canada's reactor at Chalk River, Ontario, produces most of the base isotopes for technetium-99, the most commonly used isotope in medical testing and nuclear medicine studies.
Atomic Energy of Canada Ltd. said earlier this week that the reactor will not be fully operational again until mid-January. Atomic Energy produces 50 to 80 percent of the world's supply of molybdenum-99, the isotope that breaks down into technetium-99.
"We use the same radioisotope [technetium-99] as a tracer to do cardiac imaging or bone imaging or kidney imaging or any one of those and many others, so it's not like there's one prescription drug not available ... it's a precursor to losing a number of different imaging agents and it touches many different corners of the hospital," said Ted Palmer, director of clinical nuclear medicine at Massachusetts General Hospital in Boston.
Although Palmer and many other doctors said it was too early to tell how much the shortage of technetium-99 will impact medical centers in the United States, many have already begun taking steps to preserve their supply of the isotope by offering radioactive isotope medical tests only to patients who urgently require a diagnostic imaging test.
"We will have to make determinations about which imaging agents we'll offer to patients, and we'll do it on basis of what is most urgent in a sense, what tests are needed the most," Palmer explained. "So if [the shortage] persists, we'll need to do some rationing."
"We have reduced the dose of Tc-99m for all studies requiring this isotope so as to preserve materials in hand," said Dr. Alan D. Waxman, director of nuclear medicine and co-chair of the department of imaging at Cedars-Sinai Medical Center in Los Angeles. "We preserve study quality by acquiring data for a longer period of time. We are attempting to import additional generators from a European supplier for backup."
However, in some radioactive tests, other isotopes can be used as substitutes for technetium-99. Some medical centers are now using thallium for some radioactive medical tests, which can be produced in-house by a cyclotron -- a type of particle accelerator used to produce isotopes.
"PET imaging relies on [isotopes from] a different source -- a cyclotron -- and there are many of these around the U.S. and these are all in working order," said Dr. Kristen DeStigter, assistant director of radiology at Fletcher Allen Health Care. "In response, we have shifted our cardiac studies to thallium-201, another cyclotron product."
In some cases, doctors are substituting nonradioactive methods of evaluating patients for those radioactive medical tests requiring technetium. However, this often requires using more invasive -- and less accurate -- diagnostic techniques.
"There are alternatives to make these diagnoses, and some patients will be studied in other ways, but these [radioactive] tests are usually the best way to make these diagnoses," said Manuel Cerqueira, chairman of the department of nuclear medicine at Cleveland Clinic in Ohio. "In some cases, if we have high enough suspicion that the patient has heart disease, we'll do cardiac catherization, or an angiogram, but it's very invasive."