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A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)ORCID iD: 0000-0002-0555-8877
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)ORCID iD: 0000-0002-0012-7867
2017 (English)In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 10, no 3, 446-455 p.Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Continuous measurement of local brain oxygen saturation (SO2) can be used to monitor the status of brain trauma patients in the neurocritical care unit. Currently, micro-oxygen-electrodes are considered as the “gold standard” in measuring cerebral oxygen pressure (pO2), which is closely related to SO2 through the oxygen dissociation curve (ODC) of hemoglobin, but with the drawback of slow in response time. The present study suggests estimation of SO2 in brain tissue using diffuse reflectance spectroscopy (DRS) for finding an analytical relation between measured spectra and the SO2 for different blood concentrations. The P3 diffusion approximation is used to generate a set of spectra simulating brain tissue for various levels of blood concentrations in order to estimate SO2. The algorithm is evaluated on optical phantoms mimicking white brain matter (blood volume of 0.5–2%) where pO2 and temperature is controlled and on clinical data collected during brain surgery. The suggested method is capable of estimating the blood fraction and oxygen saturation changes from the spectroscopic signal and the hemoglobin absorption profile.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2017. Vol. 10, no 3, 446-455 p.
Keyword [en]
oxygenation, diffuse reflectance spectroscopy, hemoglobin, optical phantom, human brain
National Category
Other Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-127362DOI: 10.1002/jbio.201500334ISI: 000398216200012PubMedID: 27094015OAI: oai:DiVA.org:liu-127362DiVA: diva2:922407
Note

Funding agencies: Swedish Childhood Cancer Foundation; Swedish Research Council [621-2010-4216, 621-2013-6078]

Available from: 2016-04-22 Created: 2016-04-22 Last updated: 2017-04-20Bibliographically approved
In thesis
1. Optical Monitoring of Cerebral Microcirculation
Open this publication in new window or tab >>Optical Monitoring of Cerebral Microcirculation
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The cerebral microcirculation consists of a complex network of small blood vessels that support nerve cells with oxygen and nutrition. The blood flow and oxygen delivery in the microcirculatory blood vessels are regulated through mechanisms which may be influenced or impaired by disease or brain damage resulting from conditions such as brain tumors, traumatic brain injury or subarachnoid hemorrhage (SAH). Monitoring of parameters relating to the microvascular circulation is therefore needed in the clinical setting. Optical techniques such as diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) are capable of estimating the oxygen saturation (SO2) and tracking the microvascular blood flow (perfusion) using a fiber optic probe. This thesis presents the work carried out to adapt DRS and LDF for monitoring cerebral microcirculation in the human brain.

A method for real-time estimation of SO2 in brain tissue was developed based on the P3 approximation of diffuse light transport and quadratic polynomial fit to the measured DRS signal. A custom-made fiberoptic probe was constructed for measurements during tumor surgery and in neurointensive care. Software modules with specific user interface for LDF and DRS were programmed to process, record and present parameters such as perfusion, total backscattered light, heart rate, pulsatility index, blood fraction and SO2 from acquired signals.

The systems were evaluated on skin, and experimentally by using optical phantoms with properties mimicking brain tissue. The oxygen pressure (pO2) in the phantoms was regulated to track spectroscopic changes coupled with the level of SO2. Clinical evaluation was performed during intraoperative measurements during tumor surgery (n = 10) and stereotactic deep brain stimulation implantations (n = 20). The LDF and DRS systems were also successfully assessed in the neurointensive care unit for a patient treated for SAH. The cerebral autoregulation was studied by relating the parameters from the optical systems to signals from the standard monitoring equipment in neurointensive care.

In summary, the presented work takes DRS and LDF one step further toward clinical use for optical monitoring of cerebral microcirculation.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 68 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1807
Keyword
optical monitoring, cerebral microcirculation, diffuse reflectance spectroswcopy (DRS), laser Doppler flowmetry (LDF)
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-133781 (URN)10.3384/diss.diva-133781 (DOI)978-91-7685-634-5 (ISBN)
Public defence
2017-02-10, Hugo Theorell, Campus US, Linköping, Norra entrén, Plan 9, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2010-4216Swedish Research Council, 621-2013-6078Swedish Childhood Cancer Foundation, MT2012-0043
Available from: 2017-01-17 Created: 2017-01-09 Last updated: 2017-01-26Bibliographically approved

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