The shortage of technetium-99m (99m Tc) — the main radiotracer used for single-photo emission CT myocardial perfusion imaging (SPECT-MPI) — is a problem that could be solved by adopting cardiac positron emission tomography (PET), according to the president of the American Society of Nuclear Cardiology.
A link found between a shortage of 99m Tc and a subsequent rise of excess catheterization was not necessarily just due to the substitution of inferior SPECT-MPI radiotracers, such as thallium-201, as the authors had suggested, said Brian G. Abbott, MD, of Rhode Island Hospital in Providence, in a telephone interview.
The real culprit was the fact that alternative tests — namely stress echocardiography, CT coronary angiography, PET — were not administered to make up for the 99m Tc deficiency, he suggested, which left patients heading directly to cardiac catheterization without sufficient imaging.
“Cardiac catheterization is an invasive procedure and they may have been performed unnecessarily in cases that normally would not have gone to catheterization,” he said.
Abbott suggested several factors pushing clinicians that direction: “It might be the availability of the other tests at the time — a center might not have CT or stress echocardiography, for example,” he suggested. “It also depends on the patient population; nuclear cardiology may be used in a higher-risk population.”
“The feeling might be that if we can’t evaluate these patients with a stress test, maybe it’s better to go directly to catheterization,” he commented.
Of late, 99m Tc supplies from the usual Canada and the Netherlands reactors have been stable. “But the two reactors that make this are 50 years old, and that’s why they’re getting shut down for maintenance,” Abbott said, adding that the license for the nuclear facility in Ontario expires in 2 years and is not certain to be renewed, leaving only the European reactor running.
He suggested that this could be where PET imaging would come in. With the use of different isotopes such as the “widely available” rubidium-82, “if there are more 99m Tc shortages, many different tracers that are produced locally would almost be the solution to the problem.”
Radiotracer supply aside, PET imaging with rubidium-82 is an attractive alternative because of lower radiation exposure to the patient than with SPECT-MPI using 99m Tc, Abbott added.
However, he acknowledged one major downfall — cost. “PET imaging in America is more expensive. The cameras and the rubidium itself both cost more. That’s why it’s not as widespread as SPECT.”
Still, he concluded, while “we can anticipate that 99m Tc won’t completely run out in the near future, shortages may continue that make rubidium-82 and PET a good alternative.”
Abbott reported no relevant conflicting interests.