Serious Issues With Isotope Supply

Technetium, which fuels the majority of SPECT procedures in cardiology, has suffered several disruptions in supply over the past decade. A reactor at Chalk River Laboratories in Ontario, Canada, normally supplies about half of the world’s molybdenum, which serves as a generator of technetium. The vast majority of the technetium generators are used in the United States. Canada plans to permanently shut down the reactor in 2016 due to its age and safety concerns. Thus far, no other North American sources of molybdenum have surfaced to make up for this deficit.

In the past, supply disruptions have seriously impacted the nuclear medicine community. When a radioactive leak sidelined the reactor in 2009, extreme shortages of technetium resulted over the 15 months the reactor was out of service. Because molybdenum has a half-life of 66 hours, shipments from overseas reactors to the United States caused significant logistical headaches. 

Some physicians turned to the PET tracer rubidium-82 to fill in until news broke last year that improper daily monitoring of the generator was resulting in strontium breakthroughs that left radioactive material in the patient long after a perfusion exam. While crossing the border between the United States and Canada in July 2011, two patients who had recently undergone rubidium-82 PET scans set off radiation alarms. It was learned that these patients had been inadvertently exposed to large doses of strontium contaminant, the parent isotope used in the generation of rubidium. Rubidium-82 was voluntarily taken off the market by Bracco pending review by the FDA and did not return to market until nine months later, after the FDA traced the fault to improper handling of the generator, not its manufacture. The incident has had lasting effects, however, on the molecular imaging community. Today, those using rubidium-82 must undergo special training and are subject to daily reporting requirements.

Currently, the U.S. Department of Energy (DOE) is the only domestic supplier of the isotope strontium-82 used in rubidium-82 generators. Positron Corp. is working with the FDA for certification so it can begin its own production of strontium-82, through its subsidiary Manhattan Isotope Technology, to provide a second source for the PET cardiac perfusion isotope.