Gas in scattering media absorption spectroscopy – from basic studies to biomedical applications

Self Cite

An improved method, where conventional otoscope investigation of human suspicious otitis media is combined with diffuse reflectance spectroscopy and gas in scattering media absorption spectroscopy (GASMAS) is being developed. Otitis media is one of the most common infectious diseases in children, whose Eustachian tube connecting the middle ear with the nasal cavity is more horizontal than for adults, which leads to impaired fluid drainage. At present, the use of an otoscope to visually observe possible changes in the tympanic membrane appearance is the main diagnostics method for otitis media. Inaccurate diagnosis related to similar symptoms, and the difficulty for small children to describe the condition experienced, frequently leads to over‐prescription of antibiotics and alarming increase in bacterial resistance development. More accurate diagnostic methods are highly desirable. Diffuse reflectance spectroscopy is a non‐invasive quantitative spectroscopic technique that enables to objectively quantify changes in the hemoglobin content of the tympanic membrane related to inflammation. If an infection is present, the ventilatory function of the Eustachian tube is frequently impaired and the middle‐ear cavity will be filled with fluid. GASMAS, a non‐invasive detection method, can non‐invasively determine if gas is replaced by fluid in the middle‐ear cavity.

Section: Experimental Arrangementmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Towards an optical diagnostic system for otitis media using a combination of otoscopy and spectroscopy

Lin

et al. 2019

Self Cite

“…The fitting equation can be obtained after using the Levenberg–Marquardt algorithm, as given by

S_{sample} ((), t) = P_{0} + P_{1} \times t + P_{2} \times t^{2} + K \times S_{air} ((), t)

S sample and S air are the normalized GASMAS signals for light passing through the sample and the reference ambient air, respectively. K is the fitting coefficient, t is the time in the sweep of the laser frequency and P 0, P 1 and P 2 are the coefficients of a quadratic polynomial which is used for compensating the difference in base line in the measurement of the sample and the ambient air . Finally, we obtain L eq as

L_{eq} = K \times L_{air}

…”

Section: Methodsmentioning

confidence: 99%

Detection of free oxygen and water vapor in fertilized and unfertilized eggs by diode laser spectroscopy—Exploration of diagnostics possibilities

Lin

Zhang

et al. 2017

Self Cite

Nonintrusive methods for characterizing food products are of increasing interest related to the greater awareness of food safety issues. Hen eggs are an important part in food consumption in most parts of the world. We have investigated an optical method utilizing tunable diode lasers for monitoring free gas in eggs. We show that oxygen signals, recorded around 760 nm, increase steadily as eggs become older. Further, we investigated fertilized eggs, which show a quite different temporal behavior during the hatching time. The oxygen signal decreases here with time, while water vapor, recorded around 937 nm, shows a steady increase. Conclusions regarding the size of the air cell and the oxygen availability in fertilized eggs are drawn. The technique might be developed for automatic control of egg freshness, as well as for assessing if eggs are fertilized or not.

“…The reason why this works is because the linewidth of an absorption resonance in gas molecules is several orders of magnitude less broadened by their microenvironment than absorption features of a solid or liquid material, allowing unambiguous discernment of spectral features associated with the gas. The technique of using TDLAS on scattering materials is also known as gas in scattering media absorption spectroscopy (GASMAS) . The technique has proven to be valuable in a number of medical applications by detecting gas embedded in the human sinus cavities and the mastoid bone .…”

Section: Introductionmentioning

confidence: 99%

Development of a 3‐dimensional tissue lung phantom of a preterm infant for optical measurements of oxygen—Laser‐detector position considerations

Larsson

Liao

Lundin

et al. 2017

There is a need to further improve the clinical care of our most vulnerable patients-preterm infants. Novel diagnostic and treatment tools facilitate such advances. Here, we evaluate a potential percutaneous optical monitoring tool to assess the oxygen and water vapor content in the lungs of preterm babies. The aim is to prepare for further clinical studies by gaining a detailed understanding of how the measured light intensity and gas absorption signal behave for different possible geometries of light delivery and receiver. Such an experimental evaluation is conducted for the first time utilizing a specially developed 3-dimensional-printed optical phantom based on a geometry model obtained from computer tomography images of the thorax (chest) of a 1700-g premature infant. The measurements yield reliable signals for source-detector distances up to about 50 mm, with stronger gas absorption signals at long separations and positions related to the lower part of the lung, consistent with a larger relative volume of this. The limitations of this study include the omission of scattering tissue within the lungs and that similar optical properties are used for the wavelengths employed for the 2 gases, yielding no indication on the optimal wavelength pair to use.