Making Patients See-Through

Scientists are exploring a dramatic new way to peer into patients' bodies: using specially treated gases that let doctors watch, for the first time, how breath flows through the lungs.

But the technology isn't just for lungs -- it promises to light up other organs now difficult to see with conventional scanning. Researchers are poised to try it as a colon cancer test, and say it might also offer better images of the brain or a woman's reproductive tract, without the discomfort or radiation of some of today's tests.

"It really looks like it's going to help people," said University of Virginia radiology professor James R. Brookeman.

These so-called hyperpolarized gases are still highly experimental, experts caution. But radiologists compare the black blob an MRI pictures as a lung with the brightly lit image of helium-filled lungs, and say the need is great.

"It's a new idea and a new technique" that provides "very striking" images, said James MacFall, a Duke University medical physicist who also has tested the gases.

Scanners like magnetic resonance imaging, or MRI, provide incredible illumination of parts of the body. But they don't image some organs well. They don't picture airflow through the lungs, for instance - something that could help treat emphysema, cystic fibrosis, asthma, even monitor how well a transplanted lung is adapting.

But with the help of hyperpolarized gas, an MRI shows a bright image of plump lungs. Where there's an obstruction -- where the lungs aren't doing their job -- the image is dark.

Dr. Tom Daniel, a UVA lung surgeon, uses hyperpolarized helium to help perform a tricky surgery for emphysema patients: slicing away dead portions of lung so the remaining good lung tissue moves and breathes more freely.

"It told me with a lot more confidence what part of her lung was not getting oxygen," Daniel said.

Molecules of substances like gas normally spin randomly. Physicists can fire a laser at certain gases, and the molecules temporarily spin in the same direction, called hyperpolarization.

Two Princeton University physicists were researching hyperpolarized gases for the military when one of them needed an MRI -- and wondered if the research might also help medicine.

Experiments showed the lined-up molecules of hyperpolarized helium-3 produced an MRI signal thousands of times stronger than today's technology.

Helium is benign -- divers routinely breathe it, and a helium-induced high-pitched voice is an old comedian's trick. The isotope helium-3, a byproduct of the tritium used in hydrogen bombs, is the version that can be used.

Now New Jersey-based Nycomed Amersham Imaging is preparing clinical trials necessary to prove to the Food and Drug Administration that hyperpolarized helium lung scans are safe and useful. In addition to UVA's ongoing study, Nycomed hopes to begin other studies by year's end.

But helium's not the only choice. Xenon-129 also can be hperpolarized. It can penetrate into the brain -- giving it an anesthetic effect -- and thus might give better brain scans. It's also more abundant than helium-3, which Nycomed now must buy from the former Soviet Union because the Defense Department won't sell its supplies.

Those aren't the only potential uses:

Brookeman plans next year to study inflating people's colons with helium to hunt colon cancer. Everyone over age 50 now is supposed to get a colonoscopy in which a fiber-optic tube is threaded through the intestine. Using helium to just light up precancerous colon polyps promises to be less uncomfortable, says Brookeman, who has successfully tried the experiment in dogs.

A common test to check for infertility is to inject an oily substance into a woman's fallopian tubes and then X-ray her abdomen. An early animal experiment suggests helium could tell if the fallopian tubes are blocked without an X-ray's radiation, Brookeman said.

Written By Lauran Neergaard