Spectroscopy technique shows promise thanks to novel research model
A new lung phantom is taking scientists beyond previous research models for a more comprehensive look at changes in gas volume. This could ultimately lead to more effective clinical assessment and diagnosis of respiratory pathologies.
Developed by a team at Tyndall National Institute (Cork, Ireland), the new lung phantom mimics the organ’s optical properties, tissues, and structures. This includes the alveoli — tiny air sacs in the lungs that allow for rapid gas exchange. Previous lung phantoms have not included alveoli because of their very complex anatomy. Thanks to the new lung phantom, this study has proven the feasibility of gas-in-scattering-media absorption spectroscopy (GASMAS), a light-based technology that has the potential for noninvasive optical sensing of respiratory volumes.
GASMAS, with tunable diode laser spectroscopy, turns optical signals into information for measuring gas concentration. Organ phantoms, such as the lung used in the Tyndall team’s work, help biomedical optics researchers to identify technical challenges.
According to the Tyndall study, the new lung phantom features a capillary system that can be “variably and progressively” filled with liquid that matches the optical properties of lung tissue, “allowing incrementally variable pockets of air that mimic air-filled alveolar sacs. Light transmission corresponds to the capillary content in a way that's analogous to lung inflation and deflation.” This was all done in a controlled environment that simulated the human lung’s humidity levels (100% relative humidity) and temperature (around 37 °C/98 °F). Andrea Pacheco, a Ph.D. student in the Biophotonics Group at Tyndall and lead author of the study, notes that this was among the most challenging aspects of her team’s work.
"It was frustrating simply trying to maintain a temperature of 37 degrees Celsius inside a bottle half-filled with water. No matter what I tried, I did not manage to do two consecutive GASMAS measurements with the same, or at least similar, parameters," she says, adding that developing and being able to study a more comprehensive lung phantom (than previous models) helped ultimately alleviate this challenge.
In previous studies into the GASMAS technique’s feasibility for respiratory healthcare, using newborn babies, as they are in transition in their immunologic development. And according to the researchers, “the thickness of protective organs surrounding their lungs is within the limits of penetration depth for near-IR light.” They have been working toward expanding the use of GASMAS beyond neonates, which is where the development of the lung phantom has assisted. But it will depend, in part, on advances in miniaturization and integration of pulmonary endoscopes with GASMAS probes.
It could also be possible for researchers to vary the dimensions or density of the gas pockets in the lung phantom by creating a new capillary holder and using those capillaries with different inner radii.
"A further step in that direction could be to arrange two miniature GASMAS probes in an endoscope-like geometry,” Pacheco says, “and use our phantom to determine the signal quality and optimum source-detector separation."
Justine Murphy | Multimedia Director, Digital Infrastructure
Justine Murphy is the multimedia director for Endeavor Business Media's Digital Infrastructure Group. She is a multiple award-winning writer and editor with more 20 years of experience in newspaper publishing as well as public relations, marketing, and communications. For nearly 10 years, she has covered all facets of the optics and photonics industry as an editor, writer, web news anchor, and podcast host for an internationally reaching magazine publishing company. Her work has earned accolades from the New England Press Association as well as the SIIA/Jesse H. Neal Awards. She received a B.A. from the Massachusetts College of Liberal Arts.