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Myocardial tissue oxygenation estimated with calibrated diffuse reflectance spectroscopy during coronary artery bypass grafting
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, Medical Informatics.
Linköping University, Department of Medical and Health Sciences, Thoracic Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
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2008 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 13, no 5, 054030- p.Article in journal (Refereed) Published
Abstract [en]

We present a study using a method able to assess tissue oxygenation, taking into account the absorption and the level of scattering in myocardial tissue using a calibrated fiber optic probe. With this method, interindividual comparisons of oxygenation can be made despite varying tissue optical properties during coronary artery bypass grafting (CABG). During CABG, there are needs for methods allowing continuous monitoring and prediction of the metabolism in the myocardial tissue. 14 patients undergoing CABG are investigated for tissue oxygenation during different surgical phases using a handheld fiber optic spectroscopic probe with a source-detector distance of less than 1 mm. The probe is calibrated using a light transport model, relating the absorption and reduced scattering coefficients (mu(a) and mu()(s)) to the measured spectra. By solving the inverse problem, absolute measures of tissue oxygenation are evaluated by the sum of oxygenized hemoglobin and myoglobin. Agreement between the model and measurements is obtained with an average correlation coefficient R-2 of 0.96. Oxygenation is found to be significantly elevated after aorta cross-clamping and cardioplegic infusion, as well as after reperfusion, compared to a baseline (p < 0.05). Tissue oxygenation decreases during cardiac arrest and increases after reperfusion.

Place, publisher, year, edition, pages
2008. Vol. 13, no 5, 054030- p.
Keyword [en]
diffuse reflectance spectroscopy, oxygenation, myocardium, tissue, coronary artery bypass grafting
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-16251DOI: 10.1117/1.2976433OAI: oai:DiVA.org:liu-16251DiVA: diva2:133523
Note

Original Publication: Erik Häggblad, Tobias Lindbergh, Daniel Karlsson, Henrik Casimir-Ahn, Göran Salerud and Tomas Strömberg, Myocardial tissue oxygenation estimated with calibrated diffuse reflectance spectroscopy during coronary artery bypass grafting, Journal of Biomedical Optics, (13), 5, 054030, 2008. http://dx.doi.org/10.1117/1.2976433 Copyright 2008 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

Available from: 2009-01-12 Created: 2009-01-09 Last updated: 2017-05-23Bibliographically approved
In thesis
1. In Vivo Diffuse Reflectance Spectroscopy of Human Tissue: From Point Measurements to Imaging
Open this publication in new window or tab >>In Vivo Diffuse Reflectance Spectroscopy of Human Tissue: From Point Measurements to Imaging
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents the non-invasive use of diffuse reflectance spectroscopy (DRS) to provide information about the biochemical composition of living tissue. During DRS measurements, the incident, visible light is partially absorbed by chromophores but also scattered in the tissue before being remitted.

Human skin and heart, the main tissue objects in this thesis, are dependent on a sufficient inflow of oxygenized blood, and outflow of metabolic byproducts. This process could be monitored by DRS using the spectral fingerprints of the most important tissue chromophores, oxyhemoglobin and deoxyhemoglobin.

The Beer-Lambert law was used to produce models for the DRS and has thus been a foundation for the analyses throughout this work. Decomposition into the different chromophores was performed using least square fitting and tabulated data for chromophore absorptivity.

These techniques were used to study skin tissue erythema induced by a provocation of an applied heat load on EMLA-treated skin. The absorbance differences, attributed to changes in the hemoglobin concentrations, were examined and found to be related to, foremost, an increase in oxyhemoglobin.

To estimate UV-induced border zones between provoked and nonprovoked tissue a modified Beer-Lambert model, approximating the scattering effects, was used. An increase of chromophore content of more than two standard deviations above mean indicated responsive tissue. The analysis revealed an edge with a rather diffuse border, contradictory to the irradiation pattern.

Measuring in the operating theater, on the heart, it was necessary to calculate absolute chromophore values in order to assess the state of the myocardium. Therefore, a light transport model accounting for the optical properties, and a calibrated probe, was adopted and used. The absolute values and fractions of the chromophores could then be compared between sites and individuals, despite any difference of the optical properties in the tissue.

A hyperspectral imaging system was developed to visualize the spatial distribution of chromophores related to UV-provocations. A modified Beer-Lambert approximation was used including the chromophores and a baseline as an approximate scattering effect. The increase in chromophore content was estimated and evaluated over 336 hours.

In conclusion, advancing from a restricted Beer-Lambert model, into a model estimating the tissue optical properties, chromophore estimation algorithms have been refined progressively. This has allowed advancement from relative chromophore analysis to absolute values, enabling precise comparisons and good prediction of physiological conditions.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 88 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1210
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-15191 (URN)978-91-7393-809-9 (ISBN)
Public defence
2008-10-31, Elsa Brändströmsalen, Södra entrén, Campus US, Universitetssjukhuset, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2008-10-22 Created: 2008-10-22 Last updated: 2009-04-30Bibliographically approved
2. 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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Häggblad, ErikLindbergh, TobiasCasimir-Ahn, HenrikSalerud, GöranStrömberg, Tomas

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Häggblad, ErikLindbergh, TobiasKarlsson, M. G. DanielCasimir-Ahn, HenrikSalerud, GöranStrömberg, Tomas
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The Institute of TechnologyBiomedical InstrumentationMedical InformaticsThoracic SurgeryFaculty of Health SciencesDepartment of Thoracic and Vascular Surgery
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