Laser “Breathalizers” Scan for Diseases

In the future, diagnosis of disease may be just a breath away thanks to a device called a quantum cascade (QC) laser—and scientists like Frank Tittel.

Current procedures for diagnosing diseases, such as biopsies, are not only invasive but costly and time-consuming, and they sometimes require hospitalization. But biomedical researchers know that many diseases produce specific gases, and it’s that fact that interests Tittel and other members of Rice University’s Laser Science Group, who have been designing laser-based gas sensors for medical and other uses.

“Each gas has a characteristic spectrum, like a fingerprint. The quantum cascade laser can be tuned to frequencies or wavelengths that correspond to specific gases, thereby determining the type and amount of gas that is present.” —Frank Tittel

Most recently, Tittel, the J.S. Abercrombie Professor in Electrical and Computer Engineering, collaborated with doctors at Baylor College of Medicine in Houston and medical researchers at Johns Hopkins University in Baltimore on a project involving lung transplant patients. Patients experiencing a transplant rejection have elevated levels of carbonyl sulfide, and although doctors can monitor these patients for carbonyl sulfide, the process requires routine bronchoscopies to collect and analyze tissues. To make the process simpler and quicker, Tittel and his colleagues developed a sensor capable of detecting trace amounts of various gases, including carbonyl sulfide.

“Each gas has a characteristic spectrum, like a fingerprint,” Tittel explains. “The quantum cascade laser can be tuned to frequencies or wavelengths that correspond to specific gases, thereby determining the type and amount of gas that is present.”

The process of collecting air samples from a patient might involve a simple mouthpiece, and the analysis is done in real time. “What could take days in terms of collecting and analyzing samples in a lab, the QC laser does almost immediately with as much reliability,” Tittel says. “At this point, there are approximately 400 diseases that have gas bio-markers.” Tittel has, for example, been able to measure nitric oxide, which can be an indication of airway inflammation.

The technology also has other potential applications in biomedical research, air quality studies, and the prediction of volcanic eruptions. In one study, the Laser Science Group has been working in collaboration with Federico Capasso of Harvard and Claire Gmachl of Princeton on a NASA-funded project to help monitor and improve air quality inside the space shuttles and the International Space Station. Of particular concern are carbon monoxide, ammonia, formaldehyde, and other gases that quickly become dangerous in confined areas and, therefore, are of critical concern during space flights. In field tests at Johnson Space Center, the QC laser has proved to be highly reliable and able to detect and distinguish different trace gases in a very short period of time.

Back on Earth, the team field tested its gas sensor at the edge of Masaya volcano outside of Managua, Nicaragua. In a region where steady emissions of volcanic gases have been a serious concern for the population’s health and its farming industry, Tittel and his colleagues were able to measure and compare the levels of various types of gases. “Using the quantum cascade laser to identify changes taking place in the carbon dioxide levels,” Tittel says, “could help predict volcanic eruptions up to two weeks before they happen.”

In another project, Tittel is helping the National Center for Atmospheric Research in Boulder, Colorado, monitor specific gases at different temperatures and heights in the atmosphere, including greenhouse gases such as carbon dioxide, methane, and nitrous oxide. Tittel also has been able to measure hydrochloric and hydrafluoric acid, which are critical process gases in the semiconductor industry, and he is involved in a project for the Department of Defense, looking at identifying toxic gases that might be used in terrorist attacks in the United States.

—Jade Boyd