Magnetic resonance imaging can reveal the human body's inner workings in elegant detail, except in one place—the lungs.

But if UNH's second spin-out company is successful, MRI's blind spot may soon be corrected. Formed by Bill Hersman, a UNH nuclear physics professor, Xemed will try to capitalize on his innovations to give doctors an unprecedented look inside the lungs.

MRI scanners polarize the water molecules in our bodies, aligning the hydrogen nuclei with the poles of a powerful magnet. Responding to radio waves transmitted by the scanner, the polarized nuclei resonate with their own small radio waves, and a computer uses these signals to paint a clear picture of the interior of a human body.

Lungs, however, are filled with air instead of water, and show up as a hazy blur in conventional MRIs. One solution to the problem—giving a patient pre-polarized helium to inhale—produces sharp lung images. The drawback is that pre-polarized helium is prohibitively expensive. But xenon—present in tiny quantities in the air we breathe—is not. In addition, xenon has been used as an anesthetic in surgery and has a long track record of safe use in humans. It also dissolves into lung tissue and diffuses slowly, which makes it better at revealing damaged areas of the lungs. For all these reasons, researchers have been racing to polarize xenon.

One of the hurdles when using polarized gases in lung MRIs is that they are thousands of times less dense than water. To work, they must be highly polarized to levels thousands of times higher than normal. Researchers "hyperpolarize" helium by mixing it with vaporized rubidium, and exposing the mixture to a polarizing laser. Like a clutch transferring power from a car's engine to its wheels, the rubidium transfers polarization from the laser to the helium whenever the two collide.

To increase the number of collisions between rubidium and helium atoms, the gaseous mixture is kept at high pressure so the atoms will be densely packed. Once cooled, the rubidium returns to its solid state, leaving behind pure hyperpolarized helium. Magnetic fields aid the polarization process and keep the gas in a polarized state until it is needed.

Adapting this process to xenon is an interesting problem with potentially big financial rewards. International research teams with strong financial backing have been working on it for some time in Germany, Japan and elsewhere in the United States.

Enter Hersman and his team of graduate and undergraduate researchers. As a nuclear scientist, Hersman had been polarizing gas for years to help shed light on the behavior of subatomic particles called quarks. With a small grant from the National Institutes of Health, he set out to solve the problem of lung MRIs.

Faced with a shoestring budget, Hersman brought a little Yankee ingenuity to bear. He knew that at low pressure, rubidium would combine with xenon to form short-lived molecules, a more efficient way to transfer polarization. To take advantage of that, however, he would have to come up with a way to effectively polarize rubidium at low pressure. His solution was amazingly simple. Instead of pointing the laser in the same direction as the gas flow, he turned it around and pointed it the other way. He also made the device's glass cylinder much longer to give the rubidium more exposure time. Hersman's methods produce xenon that is 60 to 70 percent polarized, better than any other method.

"Changing any one thing—lowering the pressure, increasing the flow or lengthening the cylinder—would make the system worse, but changing all three together resulted in polarization 10 times better than any other method," says Hersman. "And with a bigger laser, we can go up to a factor of 30 to 100 better."

When his grant ran out, it looked as if the project might die. Hersman persevered, however, and in 2003, the National Institutes of Health awarded Hersman two grants totaling $3.7 million to continue the work. More recently, NIH awarded Xemed $300,000 in Small Business Technology transfer grants to commercialize the technology, and Hersman anticipates another $2 million over the next few years. The grants will allow Xemed to further refine the technology and shrink the size of the polarizer.

"As a diagnostic tool, lung MRIs could benefit millions with chronic obstructive pulmonary disease, the fourth leading cause of death in the United States. There's also "a significant potential for medical cost savings by extending the frontiers of noninvasive diagnostics," he notes.

But to make the device practical, Herman's team had to fit it into a cabinet small enough so that every hospital with an MRI unit could have one. "The challenge is to bring everything together into a small space without the magnetic fields involved interfering with one another," he says.

UNH has already filed for three patents based on Hersman's innovations and is in the process of filing for two more. "This is great for UNH and New Hampshire because students can continue to be involved in the development of the technology," says Robert Dalton, director of UNH's Office of Intellectual Property Management, "and if the company takes off, it could be located right here in the Seacoast." UNH's first spin-off company, Chaoticom (now named Groove Mobile), was launched by UNH math professor Kevin Short, and is now located in Andover, Mass.

Still in the research and development phase, Xemed has only one employee besides Hersman, but he is hiring three or four more to help hand-build polarizers. Instead of selling the polarizers, the company will initially place them on site in hospitals and research institutions with annual service agreements to provide polarized xenon, says Hersman.

In time, Hersman says the company could grow dramatically. "If we can demonstrate it is effective in not only assessing and monitoring diseases, but also in helping determine whether a patient should have drugs or surgery, it could be big," he says, "and if HMOs start reimbursing for the procedure, it could be huge."

Having secured FDA approval to test polarized xenon with MRI on humans, Hersman relocated the UNH polarizer to the Brigham and Women's Hospital in Boston this spring. Working with hospital collaborator Sam Patz, he recently made the first polarized-xenon measurements on patients.

"The pressure is on now," he says. "The world has been waiting long enough for a diagnostic procedure for lung health, so we're scrambling to provide it."

Robert Emro is the science writer for UNH's College of Engineering and Physical Sciences.