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A laser Doppler system for monitoring of intracerebral microcirculation
Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. (MINT)
Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. (MINT)ORCID iD: 0000-0002-0012-7867
2012 (English)In: Conf Proc IEEE Eng Med Biol Soc., ISSN 1557-170X, 1988-1991 p.Article in journal (Refereed) Published
Abstract [en]

A two-channel standard laser Doppler perfusion monitor has been adapted for intracerebral measurements. Software developed in Labview makes it possible to present the microvascular perfusion, total light intensity (TLI), heart rate and trend curves in real-time during surgery. A custom-made optical probe was designed in order to enable easy fixation during brain surgery. The constructed brain probe was evaluated and compared to a standard probe. Both probes presented similar feasibility when used for the skin recordings. In addition, evaluation was done in one patient in relation to tumor resection. Stable perfusion and TLI signals were immediately recorded when the probe was positioned in cerebral tissue. Movement artifacts were clearly seen when the probe was moved to a new site. Recordings in cortex and tumor border showed higher perfusion and lower TLI compared to measurements in subcortical white matter. The calculated heart rate estimate agreed well with the noted value from the electrocardiographic patient monitoring system.                                                                                                                                                      

Place, publisher, year, edition, pages
IEEE , 2012. 1988-1991 p.
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-86150DOI: 10.1109/EMBC.2012.6346346ISI: 000313296502058PubMedID: 23366307ISBN: 978-1-4244-4119-8 (print)ISBN: e-978-1-4244-4120-4 ISBN: 978-1-4577-1787-1 (print)OAI: oai:DiVA.org:liu-86150DiVA: diva2:575176
Funder
Swedish Research Council
Available from: 2012-12-07 Created: 2012-12-07 Last updated: 2017-02-03Bibliographically 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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Rejmstad, PeterHillman, JanWårdell, Karin

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