| 1. |
- Barup, Kerstin, et al.
(författare)
-
Multi-disciplinary lidar applications
- 2010
-
Ingår i: Laser Applications to Chemical, Security and Environmental Analysis, LACSEA 2010. - 2162-2701. - 9781557528803
-
Konferensbidrag (refereegranskat)abstract
- Lidar is a powerful technique normally associated with atmospheric monitoring. However, lidar techniques, also of the laser-induced fluorescence and laser-induced breakdown spectroscopy varieties, provide many new possibilities in unconventional fields including cultural heritage and ecological applications.
|
|
| 2. |
- Lewander, Märta
(författare)
-
Laser Absorption Spectroscopy of Gas in Scattering Media
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Absorption spectroscopy constitutes a chemical analysis tool which can be applied to various samples and application fields. This thesis focuses on gas absorption spectroscopy with the means of diode lasers - tunable diode laser absorption spectroscopy, TDLAS. In particular, the absorption of gases inside porous scattering solids and liquids, referred to as GASMAS - gas in scattering media absorption spectroscopy, has been studied. The spectrally sharp wavelength from a diode laser is scanned over the absorption fingerprint of the studied gas, and the transmitted intensity is detected. Although the light is heavily absorbed and scattered by the bulk material, the gas absorption imprint can still be distinguished. The free gas, in contrast to the bulk material which is made out of perturbed molecules, exhibits narrow absorption lines and its absorption can thus be isolated although the light has been heavily absorbed by the solids and liquids. The diffuse light propagation demands alternative solutions to extract gas concentration, which otherwise is obtained through the Beer-Lambert law using the interaction distance. Water vapor sensing in samples with liquid water present has shown to be a feasible way to achieve information about the effective distance through gas inside the sample even though the light is heavily scattered. Applications studied in this thesis work include gas sensing within the human body for medical diagnostics, gas monitoring inside food packages for quality assurance, and fundamental studied of gas in nanoporous ceramics. Investigations of GASMAS as a diagnostic tool for the paranasal sinuses, subject to the common rhinosinusitis have been carried out. Correlation between obstruction and ventilation of the sinuses diagnosed by computer tomography and GASMAS data has been demonstrated. Diagnostic useful data from the air cell system in the mastoid bone, located behind the ears, have also been obtained. Furthermore, possibilities of gas sensing in the lungs of premature born babies have been demonstrated in a feasibility study on a realistic model made out of animal lung tissue and gelatin based phantoms. Sensing of the gas non-intrusively by GASMAS has been demonstrated on packages of minced meat, bread as well as on the headspace of translucent containers with milk or orange juice. Food packages are to an increasing extent filled with a modified atmosphere where the O2 concentration is suppressed. Traditional gas detectors for food packages are intrusive or demand direct optical access. GASMAS constitutes an alternative interesting approach with high potential. Gas detection in nano-porous samples allows fundamental studies of the gas molecules. Broadening of absorption lines of O2 and H2O due to tight confinement in nano pores in ceramics has been studied, as well as diffusion of the gases. In addition to fundamental physical interest the study of broadening and diffusion allows for assessment of material parameters.
|
|
| 3. |
- Lewander, Märta, et al.
(författare)
-
Non-intrusive measurements of headspace gas composition in liquid food packages made of translucent materials
- 2011
-
Ingår i: Packaging Technology & Science. - : Wiley. - 0894-3214. ; 24:5, s. 271-280
-
Tidskriftsartikel (refereegranskat)abstract
- The increase in chilled food consumption requires enhanced food safety and quality assurance. Food deteriorating processes are affected by the presence of oxygen, combined with factors such as time and temperature. To slow down deterioration processes and prolong shelf life, traditional packaging methods are being replaced by Modified Atmosphere Packaging (MAP), for example. Oxygen, which is naturally present in the headspace of most food packages, is then reduced and controlled. Many sensing techniques for food quality assurance have been developed; however, almost all are intrusive, increasing the complication level and causing sample waste. The purpose of this article is to introduce a non-intrusive technique (GASMAS) for measuring gas composition in the headspace of liquid food packages. The GASMAS method uses diode laser absorption spectroscopy combined with diffuse light propagation to analyze gas located inside solids and liquids. By illuminating the package from the outside and analyzing the scattered light that emerges, the absorption from the gas inside the headspace can be studied. The GASMAS technique was evaluated on a series of carton packages with high quality orange juice and a nitrogen headspace. A clear variation in oxygen content was measured for samples with different storage times. The results demonstrate the possibility of using the GASMAS method for non-intrusive quality measurements in food products and packaging. They also indicate the potential for non-intrusive quality assurance applications without waste of samples. A further development of the technique could include “in-line” quality control of packed food items throughout the food packaging supply chain.
|
|
| 4. |
- Lewander, Märta, et al.
(författare)
-
Non-invasive diagnostics of the maxillary and frontal sinuses based on diode laser gas spectroscopy
- 2012
-
Ingår i: Rhinology. - 0300-0729. ; 50:1, s. 26-32
-
Tidskriftsartikel (refereegranskat)abstract
- Problem: Suspected, but objectively absent, rhinosinusitis constitutes a major cause of visits to the doctor, high health care costs, and the over-prescription of antibiotics, contributing to the serious problem of resistant bacteria. This situation is largely due to a lack of reliable and widely applicable diagnostic methods. Method: A novel method for the diagnosis of rhinosinusitis based on non-intrusive diode laser gas spectroscopy is presented. The technique is based on light absorption by free gas (oxygen and water vapour) inside the sinuses, and has the potential to be a complementary diagnostic tool in primary health care. The method was evaluated on 40 patients with suspected sinus problems, referred to the diagnostic radiology clinic for low-dose computed tomography (CT), which was used as the reference technique. Main results:The data obtained with the new laser-based method correlated well with the grading of opacification and ventilation using CT. The sensitivity and specificity were estimated to be 93% and 61%, respectively, for the maxillary sinuses, and 94% and 86%, respectively, for the frontal sinuses. Good reproducibility was shown. Principal conclusion: The laser-based technique presents real-time clinical data that correlate well to CT findings, while being non-intrusive and avoiding the use of ionizing radiation.
|
|
| 5. |
- Lewander, Märta, et al.
(författare)
-
Nonintrusive gas monitoring in neonatal lungs using diode laser spectroscopy: feasibility study.
- 2011
-
Ingår i: Journal of Biomedical Optics. - : SPIE-Intl Soc Optical Eng. - 1083-3668. ; 16:12
-
Tidskriftsartikel (refereegranskat)abstract
- A feasibility study on noninvasive, real-time monitoring of gases in lungs of preterm infants is reported, where a laser-spectroscopic technique using diode lasers tuned to oxygen and water vapor absorption lines was employed on realistic tissue phantoms. Our work suggests that the technique could provide a new possibility for surveillance of the lung function of preterm infants, in particular the oxygenation, which is of prime importance in this patient group.
|
|
| 6. |
- Lindberg, Sven, et al.
(författare)
-
Method for Studying Gas Composition in the Human Mastoid Cavity by Use of Laser Spectroscopy
- 2012
-
Ingår i: Annals of Otology, Rhinology & Laryngology. - 0003-4894. ; 121:4, s. 217-223
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: We evaluated a method for gas monitoring in the mastoid cavity using tunable diode laser spectroscopy by comparing it to simultaneously obtained computed tomographic (CT) scans. Methods: The presented optical technique measures free gases, oxygen (O2), and water vapor (H2O) within human tissue by use of low-power diode lasers. Laser light was sent into the tip of the mastoid process, and the emerging light at the level of the antrum was captured with a detector placed on the skin. The absorption of H2O was used to monitor the probed gas volume of the mastoid cavity, and it was compared to the CT scan measured volume. The ratio between O2 absorption and H2O absorption estimated the O2 content in the mastoid cavity and thus the ventilation. The parameters were compared to the grading of mastoid cavities based on the CT scans (n = 31). The reproducibility of the technique was investigated by measuring each mastoid cavity 4 times. Results: Both O2 and H2O were detected with good reproducibility. The H2O absorption and the CT volume correlated (r = 0.69). The average ratio between the normalized O2 absorption and the H2O absorption signals was 0.7, indicating a lower O2 content than in surrounding air (expected ratio, 1.0), which is consistent with previous findings made by invasive techniques. All mastoid cavities with radiologic signs of disease were detected. Conclusions: Laser spectroscopy monitoring appears to be a usable tool for noninvasive investigations of gas composition in the mastoid cavity, providing important clinical information regarding size and ventilation.
|
|
| 7. |
- Lundin, Patrik, et al.
(författare)
-
Non-intrusive headspace gas measurements by laser spectroscopy – Performance validation by a reference sensor
- 2012
-
Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774. ; 111:4, s. 612-617
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe oxygen concentration in the headspace of a large number of liquid food containers is assessed with non-intrusive diode laser absorption spectroscopy. The results are compared to those given by a traditional intrusive measurement method. The upper portions of the containers are made of translucent but non-transparent plastic materials, through which the laser light is diffusively transmitted. Measurements are performed both on packages with modified atmosphere and with normal air conditions. It is concluded that the novel non-intrusive technique provides oxygen concentrations that generally differ by less than one percentage point from the reference sensor values.
|
|
| 8. |
- Lundin, Patrik, et al.
(författare)
-
Non-invasive gas monitoring in newborn infants using diode laser absorption spectroscopy: A case study
- 2012
-
Ingår i: Optical Diagnostics and Sensing XII: Toward Point-of-Care Diagnostics; and Design and Performance Validation of Phantoms Used in Conjunction with Optical Measurement of Tissue IV. - : SPIE. - 1996-756X .- 0277-786X. ; 8229
-
Konferensbidrag (refereegranskat)abstract
- Non-invasive diode laser spectroscopy was, for the first time, used to assess gas content in the intestines and the lungs of a new-born, 4 kg, baby. Two gases, water vapor and oxygen, were studied with two low-power tunable diode lasers, illuminating the surface skin tissue and detecting the diffusely emerging light a few centimeters away. The light, having penetrated into the tissue, had experienced absorption by gas located in the lungs and in the intestines. Very distinct water vapor signals were obtained from the intestines while imprint from oxygen was lacking, as expected. Detectable, but minor, signals of water vapor were also obtained from the lungs, illuminating the armpit area and detecting below the collar bone. Water vapor signals were seen but again oxygen signals were lacking, now due to the difficulties of penetration of the oxygen probing light into the lungs of this full-term baby. Ultra-sound images were obtained both from the lungs and from the stomach of the baby. Based on dimensions and our experimental findings, we conclude, that for early pre-term babies, also oxygen should be detectable in the lungs, in addition to intestine and lung detection of water vapor. The present paper focuses on the studies of the intestines while the lung studies will be covered in a forthcoming paper.
|
|
| 9. |
- Lundin, Patrik, et al.
(författare)
-
Noninvasive monitoring of gas in the lungs and intestines of newborn infants using diode lasers: feasibility study.
- 2013
-
Ingår i: Journal of Biomedical Optics. - 1083-3668. ; 18:12
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT. Preterm newborn infants have a high morbidity rate. The most frequently affected organs where free gas is involved are the lungs and intestines. In respiratory distress syndrome, both hyperexpanded and atelectatic (collapsed) areas occur, and in necrotizing enterocolitis, intramural gas may appear in the intestine. Today, these conditions are diagnosed with x-ray radiography. A bed-side, rapid, nonintrusive, and gas-specific technique for in vivo gas sensing would improve diagnosis. We report the use of noninvasive laser spectroscopy, for the first time, to assess gas content in the lungs and intestines of three full-term infants. Water vapor and oxygen were studied with two low-power diode lasers, illuminating the skin and detecting light a few centimeters away. Water vapor was easily detected in the intestines and was also observed in the lungs. The relatively thick chest walls of the infants prevented detection of the weaker oxygen signal in this study. However, results from a previous phantom study, together with scaling of the results presented here to the typical chest-wall thickness of preterm infants, suggest that oxygen also should be detectable in their lungs.
|
|
| 10. |
- Svensson, Tomas, et al.
(författare)
-
Disordered, strongly scattering porous materials as miniature multipass gas cells
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:14
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the interaction of light and gas in strongly scattering nano- and macroporous media. Manufacturing and structural characterization of ZrO2, Al2O3 and TiO2 ceramics with different pore sizes, measurements of optical properties using photon time-of-flight spectroscopy, and high-resolution laser spectroscopy of O 2 at 760 nm are reported. We show that extreme light scattering can be utilized to realize miniature spectroscopic gas cells. Path length enhancement factors up to 750 are reached (5.4 m path through gas for light transmitted through a 7 mm ZrO2 with 49% porosity and 115 nm pores). © 2011 American Physical Society.
|
|
