Laser light can be used to detect molecules in breath that may be markers for diseases like asthma or cancer.
Although it has yet to be tested in clinical trials, a new apparatus may allow doctors to screen people for certain diseases simply by sampling their breath, according to JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado (CU-Boulder).
Known as optical frequency comb spectroscopy, the method is powerful enough to sort through all the molecules in human breath and sensitive enough to distinguish rare molecules that may be biomarkers for specific diseases, said Ye.
When many breath molecules are detected simultaneously, highly reliable, disease-specific information can be collected. Asthma, for example, can be detected much more reliably when carbonyl sulfide, carbon monoxide and hydrogen peroxide are all detected simultaneously with nitric oxide.
While current breath analysis using biomarkers is a noninvasive and low-cost procedure, approaches are limited because the equipment is either not selective enough to detect a diverse set of rare biomarkers or not sensitive enough to detect particular trace amounts of molecules exhaled in human breath.
"The new technique has the potential to be low-cost, rapid and reliable, and is sensitive enough to detect a much wider array of biomarkers all at once for a diverse set of diseases," Ye said.
To test the technology, Ye's team had several CU-Boulder volunteer students breathe into an optical cavity -- a space between two curved mirrors -- then directed sets of ultrafast laser pulses into the cavity. As the light pulses ricocheted around the cavity tens of thousands of times (covering a distance of several kilometers by the time it exited the cavity), the researchers determined which frequencies of light were absorbed, indicating which molecules -- and their quantities -- were present by the amount of light they absorbed.
The remarkable combination of a broad spectral coverage of the entire comb and a sharp spectral resolution of individual comb lines allows them to sensitively identify many different molecules, Ye said. They detected trace signatures of gases like ammonia, carbon monoxide and methane from the samples of volunteers. In one measurement, they detected carbon monoxide in a student smoker that was five times higher compared to a nonsmoking studen.
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