Eugene V. Stepanov

Single-breath NO detection with tunable diode lasers for pulmonary disease diagnosis

An analyzer aimed for single-breath detection of exhaled endogenous NO is described. It is based on lead-salt MBE tunable diode lasers (TDL) operating at 5.4 micrometers spectral region. Specially designed high sensitive and fast acquisition system used in combination with the Herriott multipass gas cell allows 1 ppb concentration sensitivity to exhaled NO with about 0.5 s temporal resolution. Careful selection of the used analytical spectral region ensures high NO detection selectivity in the conduction if elevated water vapor and carbon dioxide content in exhaled air. Due to the TDL high spectral resolution the analyzer is also insensitive to the other numerous endogenous substances that could be present in exhaled air. The TDL NO analyzer was tested in measuring endogenous NO content in exhalation of patients suffering from different pulmonary diseases as well as of healthy control subjects. Some single-breath NO trace specific in asthma and COPD was observed allowing differentiation of these diseases with the exhalation NO test.

Infrared fibers: power delivery and medical applications

The enhancement of polycrystalline MIR-fibers for 4 - 16 um range allows to spread their practical usage in medicine. The improved parameters of core/clad MIR-fibers are considered for the main areas of medical applications: power delivery for CO2-laser surgery; fiber probes for IR-spectroscopy diagnostics; and fiber pyrometry or IR-imaging with fiber bundles.

Diode-laser spectroscopy of collisional broadening in the spectra of polyatomic molecules

Abstract Collisional broadening of absorption lines in 32SF6 and CF2Cl2 spectra has been investigated by using diode-laser (DL) spectroscopy for different buffer gases. New methods are proposed to obtain average information on line widths in polyatomic molecular spectra that are characterized by high spectral line densities.

Endogenous CO monitoring in exhalation with tunable diode lasers: applications to clinical and biomedical diagnostics

Middle IR tunable diode lasers were applied to studies of pulmonary excretion of endogenous carbon monoxide (CO). Variations of the CO content level in exhaled air of healthy nonsmokers were investigated for different environmental conditions with the applied laser technique. Correlation of the obtained data with atmospheric CO contamination and elevated oxygen content were studied as well as diurnal variations of the endogenous CO in exhalation was observed. Criteria for correct conditions of the endogenous CO detection in breath could be derive don this basis. Developed laser approach and methods were applied for the analysis of the excreted CO level in different diseases like bronchial asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, anemia and hepatitis. Laser based close-to-real-time monitoring of the endogenous CO elimination with breath in the course of different dynamic tests was demonstrated to be informative in studies of blood oxygen transport and pH variations in tissues for different challenges tests in human physiology.

13CO2/12CO2 ratio analysis in exhaled air by lead-salt tunable diode lasers for noninvasive diagnostics in gastroenterology

An analyzer of 13CO2/12CO2 ratio in exhaled air based on lead-salt tunable diode lasers is presented. High accuracy of the carbon isotope ratio detection in exhaled carbon dioxide was achieved with help of very simple optical schematics. It was based on the use of MBE laser diodes operating in pulse mode and on recording the resonance CO2 absorption at 4.2 micrometers . Special fast acquisition electronics and software were applied for spectral data collection and processing. Developed laser system was tested in a clinical train aimed to assessment eradication efficiency in therapy of gastritis associated with Helicobacter pylori infection. Data on the 13C-urea breath test used for P.pylori detection and obtained with tunable diode lasers in the course of the trail was compared with the results of Mass-Spectroscopy analysis and histology observations. The analyzer can be used also for 13CO2/12CO2 ratio detection in exhalation to perform gastroenterology breath test based on using other compounds labeled with stable isotopes.

Multicomponent gas analyzers based on tunable diode lasers

A family of multicomponent gas analyzers based on tunable diode lasers (TDL) are presented including an open optical path 3-component gas analyzer for monitoring atmosphere pollution; a 4-gas component analyzer with a multipass cell, a multichannel TDL system with multipass cell and MIR fiber optics delivery, and a multichannel TDL analyzer for breath content gas analysis. A4B6 tunable diode lasers of different spectral region form 4 to 12 micron were used in every channel of the analyzers to obtain atmospheric transmission spectra and to measure concentration of studied gases. Main gaseous atmospheric pollutants like CO, NO, NH3, CH4, SO2, etc. and some of breath gases could be measured at ppb concentration level in real time with these systems depending on customers requirements. The analyzers are driven by IBM compatible PC. The first results on field monitoring tests as well as on their application to human exhalation content analysis and human exposure monitoring are presented.

Tunable diode laser spectroscopy accessories based on middle IR halide and chalcogenide fibers

The use of mid-IR fiberoptic components in spectroscopy and analysis using A4B6 tunable diode lasers has been studied, and the results are reported. Spectral parameters of the fibers and complete spectroscopic systems based on the fibers and Pb-salt diode lasers are presented. The further development of the presented systems for applications in remote monitoring, multicomponent gas mixtures analysis, and evanescent wave spectroscopy of gases is addressed.

Spectral gas analysis of polyatomic molecules by tunable diode lasers

The application of high-resolution tunable diode laser spectroscopy to the trace gas analysis of polyatomic molecules is experimentally investigated. A trace detection limit of 10 exp -8 vol pct was obtained for Freon-12, allowing the concentration of this gas in the atmosphere to be measured.

Infrared diode laser chemical sensors with multipass cell based on silver halide and chalcogenide fibers

A high sensitive chemical analyzer of molecular gases is presented. Its based on measurements of high resolution molecular absorption spectra obtained with infrared tunable diode lasers (TDL). To transmit radiation from lasers to an analytical cell and back to detectors, infrared fibers with low optical losses are used. A multipass optical cell is used to enhance the essential sensitivity of the sensor. Various gaseous molecular objects could be detected by this analyzer due to the wide spectral range of available TDLs and fibers. Use of fibers for laser transfer could provide remote monitoring and multicomponent mixture analysis and evanescent spectroscopy of gases in the near future.

Determination of integral intensity of the ν6 band of CF235Cl2 (freon-12) according to the data of diode laser spectroscopy

Abstract This paper presents the results of the measurements of absolute values of absorption coefficients of the CF 2 Cl 2 molecule in the regions 915–915.7 ( P branch), 923–923.5 ( Q branch), and 929.55–930.10 cm −1 ( R branch) carried out using a diode laser spectrometer with high resolution (10 −4 –10 −3 cm −1 ), and vibration-rotation transitions have been identified in these ranges. The integrated intensity of the ν 6 band CF 2 35 Cl 2 s = 292 cm −2 atm −1 and the first derivative of the dipole moment ∥ ϖμ ϖq 6 ∥ = 0.38 D have been found.