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Asthma, cancer diagnoses may be just a breath away

By Bill Scanlon, Rocky Mountain News (Contact)

Published February 18, 2008 at 11:01 a.m.
Updated February 18, 2008 at 11:01 a.m.

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Detecting asthma or cancer could be only a breath away, with help from powerful laser lights.

Colorado scientists have found that by blasting laser light at a person's breath, they can detect molecules that could be markers of asthma or cancer.

The technique is powerful enough to sort through all the molecules in human breath, and is sensitive enough to distinguish rare molecules that may be biomarkers for disease, said Jun Ye, a fellow at the University of Colorado's Joint Institute for Laboratory Astrophysics.

The process is called optical frequency comb spectroscopy, Ye and his colleagues at CU and the National Institute for Standards and Technology, wrote in the on-line edition of Optics Express.

When people breathe, they inhale a mix of gases — nitrogen, oxygen, carbon dioxide, water vapor and trace amounts of other gases such as carbon monoxide, nitrous oxide and methane, said Ye, who also is a scientist with NIST in Boulder.

The air people exhale contains less oxygen, more carbon dioxide and more than 1,000 types of other molecules, mostly in trace amounts.

Dentists know that bad breath can indicate dental problems.

Similarly, too much methylamine can be a signal of liver and kidney disease, Ye said.

Excess ammonia can indicate renal failure; too much acetone could mean diabetes; more than expected nitric oxide could indicate asthma.

A more reliable diagnosis of asthma could be made if carbon dioxide, carbonyl sulfide and hydrogen peroxide all are detected along with nitric oxide. The comb can detect all those molecules, and their relative quantity.

Ye worked with CU graduate assistant Michael Thorpe, doctoral student Matthew Kirchner and former graduate student David Balslev-Clausen on the project.

The optical frequency comb was developed in the 1990s by CU's John Hall and Theodor W. Hansch of the Max-Planck Institute, who shared the 20005 Nobel Price in physics.

Ye's group was the first to apply the frequency combs to spectroscopy — the analysis of the light emitted or absorbed by matter.

The comb is a precise laser. for measuring different frequencies of light, Ye said. Each tooth on the comb line is tuned to measure a different frequency. Each molecule vibrates and rotates at a distinct frequency, and the comb can distinguish among them all, Ye said.

To test their technique, the scientists asked several CU students to breathe into a space between two curved mirrors. The scientists then blasted ultra-fast laser pulses into the cavity formed by the mirrors.

The light pulses ricocheted around the cavity tens of thousands of times. The scientists detected which light frequencies were absorbed, learning which molecules were present — and at what quantities — by the amount of light they absorbed.

They detected trace signatures of gases like ammonia, carbon monoxide and methane in the volunteers.

One volunteer, who was a smoker, had five times the level of carbon monoxide compared to non-smoking students.

Current breath-analysis techniques don't use equipment sensitive enough to detect many of the rare biomarkers or those in tiny trace amounts, Ye said.

The new technique could be a "low-cost, rapid and reliable" diagnostic tool for a wide variety of diseases, he said.

The U.S. Air Force, Agilent Technologies, NIST, the National Science Foundation and CU were among those that funded the study.