The trigger for the supply-chain disruption was the unexpected closure in August of the High Flux Reactor in Petten, the Netherlands - one of the main production sites for the radioisotopes used in radiopharmaceuticals.

That shutdown has resulted in an interruption in the supply of molybdenum-99 (Mo-99), a fission by-product that's used to make technetium-99m (Tc-99m) and iodine-131 (I-131). Tc-99m and I-131 are the predominant radionuclides used in diagnostic and therapeutic nuclear-medicine studies.

The High Flux Reactor is not expected to be operational again until the end of November at the earliest. To make matters worse, two of the other handful of reactors that produce Mo-99 - one in Belgium, the other in France - have also been closed for maintenance.

Right now, the EMEA estimates that availability of Mo-99/Tc-99m "generators" has been cut by 50% in EU countries. Generators are solutions of parent radionuclides that are supplied to nuclear-medicine centres, where they are used to produce a short-lived radionuclide for radiolabelling.

One option being floated with regulatory authorities in EU member states is to permit suppliers of Mo-99/Tc-99m generators to make minor changes to their manufacturing processes to yield other sources for the radionuclides.

Gill Vivian, president of the British Nuclear Medicine Society, says the radioisotope shortage has resulted in delays in investigations for some patients. "Nuclear-medicine specialists have been working with authorities in member states to ensure that other investigations are available where the radioisotope shortage may lead to a delay in diagnosis and treatment," he told medicalphysicsweb.

To date, the industry has been able to maintain a minimum level of supply and departments have modified their work practices to optimize utilisation. "Where possible," Vivian added, "other radioisotopes are being used - e.g. thallium-201 for heart scans - and we are using new software designed to improve image quality to obtain diagnostic scans with reduced activity administered."

In single-photon-emission computed tomography, which is commonly used for brain and bone scans, Tc-99m is administered to the patient and the escaping gamma rays captured by a rotating gamma camera to yield a 3D data set. I-131 (or radioiodine) is a beta emitter that can be used to treat cancer and other diseases of the thyroid gland.