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Improved model for myocardial diffuse reflectance spectra by including mitochondrial cytochrome aa3, methemoglobin, and inhomogenously distributed RBC
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.
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.
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2011 (English)In: Journal of Biophotonics, ISSN 1864-063X, Vol. 4, no 4, 268-276 p.Article in journal (Refereed) Published
Abstract [en]

Hemo- and myoglobin oxygen saturation and cytochrome aa3 oxidation was locally assessed using calibrated diffuse reflectance spectroscopy in fourteen patients undergoing coronary artery bypass grafting. Diffuse spectral reflectance data, recorded with a handheld fiberoptic probe with a single source-detector separation, was analyzed using an empirical light transport model relating the absorption and reduced scattering coefficients to the measured spectrum. The absorption coefficient has previously been modeled as a sum of hemoglobin and myoglobin, fat, and water. In this study, inclusion of cytochrome aa3 and the sum of methemoglobin and metmyoglobin improved the spectral fit, especially in the wavelength regions where their absorption is prominent. On average, the extended model increased the mean R2 from 0.96 to 0.99 and displayed 4% units higher saturation levels. After aorta cross-clamping, the sum of hemo- and myoglobin oxygen saturation increased while cytochrome aa3 oxidation decreased slightly. Opposite trends were observed during cardiac arrest. At reperfusion, the saturation increased compared to the levels found at cardiac arrest, and the cytochrome aa3 oxidation was restored. The estimated tissue chromophore fractions, saturation and oxidation, were in agreement with other studies.

Place, publisher, year, edition, pages
John Wiley & Sons, 2011. Vol. 4, no 4, 268-276 p.
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:liu:diva-25583DOI: 10.1002/jbio.201000048ISI: 000289716000007OAI: oai:DiVA.org:liu-25583DiVA: diva2:246009
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-02-09Bibliographically 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)
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Available from: 2009-10-15 Created: 2009-10-08 Last updated: 2016-08-31Bibliographically approved

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Lindbergh, TobiasHäggblad, ErikAhn, HenrikSalerud, GöranLarsson, MarcusStrömberg, Tomas

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