Ninety-one percent of hospitals, pharmacies and commercial imaging groups that answered a June survey by the Society of Nuclear Medicine said the shortage had affected them.
"You already have a vulnerable population with cancer, so it's not trivial," said Dr. Jeffrey Norenberg, who heads the National Association of Nuclear Pharmacies and directs radiopharmaceutical sciences at the University of New Mexico.
Technetium-99 is processed from molybdenum-99 and used in body scans for cancer, heart disease or kidney illness. It's combined with a substance to target a specific organ or tumor, then that tracer is injected and a gamma camera looks at the distribution of radioactivity to spot problems.
The shortage began with the shutdown of a Canadian nuclear reactor in Chalk River, Ontario, that produces half the U.S. supply of molydenum-99. Technetium-99 must be made daily because it lasts just six to 12 hours.
The Canadian reactor and another in the Netherlands produce most of the U.S. and European supply. The Dutch reactor is down for maintenance for several weeks, then will be offline for up to six months next year.
"With both of them offline, it's very perilous," Norenberg said.
In the meantime, the U.S. is getting a smaller supply from South Africa.
Past shutdowns have left similar problems; a monthlong shutdown of the Canadian reactor in 2007 created a critical shortage.
Nuclear medicine physicians and pharmacists say they can handle 75 percent of the caseload with as little as half pre-shortage isotope amounts by scheduling patients when isotopes are more available and scanning them longer using smaller amounts of the isotope.
Clinics normally operate Monday through Friday, but "we've begun doing bone scans on weekends" when isotopes are still available, said Dr. Michael Graham, president of the Society of Nuclear Medicine and head of nuclear medicine at the University of Iowa Carver College of Medicine.
The cost will rise as well. Existing contracts have kept prices from increasing instantly, but Graham expects them to double when contracts expire, raising per-patient cost for a technetium-99 study from $20 to $40.
Some patients now are being shifted to a formerly used isotope. Graham said it works, but the radiation dose "is somewhat higher, it takes longer to do, the image quality may not be quite as good."
A little over half of technetium-99 used in the U.S. goes for heart imaging. Norenberg said the only alternatives to some heart function tests are invasive procedures such as cardiac catheterization that increase a patient's risk.
Bone scans checking for the spread of cancer account for the next-highest use of the isotope. An alternative substance for bone scans is not widely available nor is the equipment to use it, Norenberg said. In addition, Medicaid, Medicare and other insurance won't reimburse for it.
Graham said no reasonable alternatives exist for a number of studies, such as evaluating kidney function.
Most molybdenum-99 comes from five reactors - all outside the U.S. - with an average age of 47 years. The Canadian reactor had a projected life of 40 years but is now 52, and increasing maintenance needs mean time-consuming outages.
"It's a bit like pulling a thread on your sweater; you don't know where it's going to stop," Norenberg said.
About a dozen years ago, the Canadian government announced a huge investment for new reactors at Chalk River to produce most of the world's supply. That prompted the U.S. to abandoned planned projects.
But last year the Canadians dropped their program, which was over budget and years beyond its projected start date. Two months ago, Prime Minister Stephen Harper said Canada will be out of the medical isotopes business by about 2016.
"Everybody's eggs were in that basket," Norenberg said. A new Australian reactor produces only about 7 percent of the supply, and Norenberg does not expect it to increase production significantly.
Other options - a reactor dedicated to medical isotopes, partnerships for specialized reactors or upgrading a University of Missouri reactor - are years away and face political, licensing or regulatory hurdles.
"So it would take a significant amount of time before there was meaningful production," Norenberg said.
--- On the Net: Society of Nuclear Medicine: http://www.snm.org