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Spectral determination of a two-parametric phase function for polydispersive scattering liquids
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-3454-6576
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.ORCID iD: 0000-0001-6385-6760
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2009 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 3, 1610-1621 p.Article in journal (Refereed) Published
Abstract [en]

A method for determining a two-parametric Gegenbauer-kernel phase function that accurately describes the diffuse reflectance from a polydispersive scattering media at small source-detector separations (0.23 to 1.2 mm), is presented. The method involves spectral collimated transmission measurements, spatially resolved spectral diffuse reflectance (SRDR) measurements, and inverse Monte Carlo technique. Both absolute calibration (using a monodispersive polystyrene microsphere suspension) and relative calibration (eliminating differences between fibers) of SRDR spectra yielded comparable results. When applied to water dilutions of milk, simulated and measured spectra deviated less than 6.5% and 2.5% for the absolute and relative calibration case, respectively, even for the closest fiber separation. Corresponding values for milk including ink as an absorber, were 13.4% and 7.3%.

Place, publisher, year, edition, pages
2009. Vol. 17, no 3, 1610-1621 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-18841DOI: 10.1364/OE.17.001610OAI: oai:DiVA.org:liu-18841DiVA: diva2:221894
Available from: 2009-06-05 Created: 2009-06-05 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Quantitative diffuse reflectance spectroscopy: myocardial oxygen transport from vessel to mitochondria
Open this publication in new window or tab >>Quantitative diffuse reflectance spectroscopy: myocardial oxygen transport from vessel to mitochondria
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the field of biomedical optics, diffuse reflectance spectroscopy (DRS) is a frequently used technique for obtaining information about the optical properties of the medium under investigation. The method utilizes spectral difference between incident and backscattered light intensity for quantifying the underlying absorption and scattering processes that affects the light-medium interaction.

In this thesis, diffuse reflectance spectroscopy (DRS) measurements have been combined with an empirical photon migration model in order to quantify myocardial tissue chromophore content and status. The term qDRS (quantitative DRS) is introduced in the thesis to emphasize the ability of absolute quantification of tissue chromophore content. To enable this, the photon migration models have been calibrated using liquid optical phantoms. Methods for phantom characterization in terms of scattering coefficient, absorption coefficient, and phase function determination are also presented and evaluated. In-vivo qDRS measurements were performed on both human subjects undergoing routine coronary artery bypass grafting (CABG), and on bovine heart during open-chest surgery involving hemodynamic and respiratory provocations. The application of a hand-held fiber-optic surface probe (human subjects) proved the clinical applicability of the technique as the results were in agreement with other studies. However, problems with non-physiological variations in detected intensity due to intermittent probe-tissue discontact were observed. Also, systematic deviations between modeled and measured spectra were found. By model inclusion of additional chromophores revealing the mitochondrial oxygen uptake ability, an improved model fit to measured data was achieved. Measurements performed with an intramuscular probe (animal subjects) diminished the influence of probe-tissue discontact on the detected intensity. It was demonstrated that qDRS could quantify variations in myocardial oxygenation induced by physiological provocations, and that absolute quantification of tissue chromophore content could be obtained.

The suggested qDRS method has the potential of becoming a valuable tool in clinical practice, as it has the unique ability of monitoring both the coronary vessel oxygen delivery and the myocardial mitochondrial oxygen uptake ability. This makes qDRS suitable for directly measuring the result of different therapies, which can lead to a paradigm shift in the monitoring during cardiac anesthesia.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 92 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1276
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-25587 (URN)978-91-7393-522-7 (ISBN)
Public defence
2009-10-30, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2009-10-15 Created: 2009-10-08 Last updated: 2016-08-31Bibliographically approved

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Lindbergh, TobiasFredriksson, IngemarLarsson, MarcusStrömberg, Tomas

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