That old party favor, the helium balloon, somewhat bothers Dr. Rakesh A. Shah.

"I go to kids' parties all the time, and see helium balloons," Shah said. "As fun as they are, someday these kids may wish our generation had instead saved the helium for the MRI studies they may need as adults."

The Earth, it turns out, is rapidly depleting its easily gotten stocks of the universe's second-most abundant element, and Shah said radiologists should take notice.

In an opinion article in the current issue of the Journal of the American College of Radiology, Shah, a radiologist with Winthrop-University Hospital in Mineola, N.Y., calls on his colleagues to join groups of concerned scientists worried that U.S. helium stocks are fast running out.

The gas, used for super-cooling superconducting MRI magnets, among other applications, is formed during a billion-year process of radioactive decay, and can't be artificially manufactured. The United States owns the world's largest helium reserves, mostly trapped in a series of north Texas wells. This cache is thought to supply about one-third of the globe's helium needs. But we're running out -- and partly by design.

"This stuff is literally going up in the air," Shah told DOTmed News.

In 1996, a budget-panicky Congress passed the Helium Privatization Act, which forces the government to sell off its helium reserves by 2015 to pay back the costs of investing in the system, a process that began in the 1920s.

According to a Fort Worth Star-Telegram report this week, the Federal Helium Reserve in Texas is running a bit behind schedule, but still should exhaust its helium stocks by 2020, possibly forcing the United States to become a net importer of the inert gas as early as 2025.

Some experts argue the reason for helium's speedy depletion is that, in large part because of the U.S. government's mandatory sell-off, the price of the gas is kept artificially low. A 2010 report by the National Academy of Sciences, which pointed out that helium was too cheaply priced, warned about the risks of losing the U.S. reserves, and called for extending the depletion deadline, investing in cheaper ways to recycle the gas and working out a market-driven price.

"The harsh truth of the matter is, the only way to make this last longer is to raise the price," Shah said.

In an interview with the Telegraph last year, Robert Richardson, the chair of the NAS' helium report committee and a Nobel prize winner, said if the price of helium captured its true value, the cost of helium balloons, for instance, should be roughly 64 pounds -- or north of $100 -- a piece.

Off the radar

Although helium is used to run high-speed particle accelerators and in industrial leak testing, about a quarter of the country's helium supplies go toward health care, both for keeping MRI magnets cold and generating radioactive isotopes for nuclear medicine, Shah said.

Despite its importance in radiology, Shah said he was surprised to learn most of his colleagues aren't especially aware of the problem.

"I work in an academic setting and my colleagues are up to date on all the latest developments in radiology. They can tell you about some of the most obscure diagnoses and newest procedures," he said. "But [helium's] completely off the radar of most radiologists."

Yet, once world gas reserves run out, the next option will be processing it out of the air -- which, at least with current technology, would be hugely inefficient and costly, requiring the distillation of thousands of gallons of air to squeeze out only tiny usable amounts of helium. Of course, by then, the pressure to conserve the gas could result in widespread, and more efficient, methods of recycling. And one day -- although this is now firmly in the realm of science-fiction -- helium could be extracted from the moon.

But Shah said, at least for the near future, he's not optimistic. "We can't even tackle global warming," he said.