Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Optical Monitoring of Cerebral Microcirculation
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)ORCID iD: 0000-0003-1869-6387
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. , p. 68
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1807
Keywords [en]
optical monitoring, cerebral microcirculation, diffuse reflectance spectroswcopy (DRS), laser Doppler flowmetry (LDF)
National Category
Other Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-133781DOI: 10.3384/diss.diva-133781ISBN: 978-91-7685-634-5 (print)OAI: oai:DiVA.org:liu-133781DiVA, id: diva2:1063797
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, MT2012-0043Available from: 2017-01-17 Created: 2017-01-09 Last updated: 2017-01-26Bibliographically approved
List of papers
1. A laser Doppler system for monitoring of intracerebral microcirculation
Open this publication in new window or tab >>A laser Doppler system for monitoring of intracerebral microcirculation
2012 (English)In: Conf Proc IEEE Eng Med Biol Soc., ISSN 1557-170X, p. 1988-1991Article 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
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-86150 (URN)10.1109/EMBC.2012.6346346 (DOI)000313296502058 ()23366307 (PubMedID)978-1-4244-4119-8 (ISBN)e-978-1-4244-4120-4 (ISBN)978-1-4577-1787-1 (ISBN)
Funder
Swedish Research Council
Available from: 2012-12-07 Created: 2012-12-07 Last updated: 2017-02-03Bibliographically approved
2. A laser Doppler system for monitoring of cerebral microcirculation: implementation and evaluation during neurosurgery
Open this publication in new window or tab >>A laser Doppler system for monitoring of cerebral microcirculation: implementation and evaluation during neurosurgery
2016 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, ISSN 0140-0118, Vol. 54, no 1, p. 123-131Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to adapt and evaluate laser Doppler perfusion monitoring (LDPM) together with custom designed brain probes and software for continuous recording of cerebral microcirculation in patients undergoing neurosurgery. The LDPM system was used to record perfusion and backscattered light (TLI). These parameters were displayed together with the extracted heart rate (HR), pulsatility index (PI) and signal trends from adjustable time intervals. Technical evaluation was done on skin during thermal provocation. Clinical measurements were performed on ten patients undergoing brain tumour surgery. Data from 76 tissue sites were captured with a length varying between 10 s to 15 min. Statistical comparisons were done using Mann-Whitney tests. Grey and tumour tissue could be separated from white matter using the TLI-signal (p < 0.05). The perfusion was significantly higher in grey and tumour tissue compared to white matter (p < 0.005). LDPM was successfully used as an intraoperative tool for monitoring local blood flow and additional parameters linked to cerebral microcirculation (perfusion, TLI, heart rate and PI) during tumour resection. The systems stability opens up for studies in the postoperative care of patients with e.g. traumatic brain injury or subarachnoid haemorrhage.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2016
Keywords
Microcirculation, Brain tumour Laser Doppler perfusion monitoring (LDPM), Pulsatility index (PI), Neurosurgery
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-120632 (URN)10.1007/s11517-015-1332-5 (DOI)000371437900010 ()26105147 (PubMedID)
Funder
Swedish Research Council, 6212-010-4216
Available from: 2015-08-20 Created: 2015-08-20 Last updated: 2017-12-04Bibliographically approved
3. A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy
Open this publication in new window or tab >>A method for monitoring of oxygen saturation changes in brain tissue using diffuse reflectance spectroscopy
2017 (English)In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 10, no 3, p. 446-455Article in journal (Refereed) Published
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
Keywords
oxygenation, diffuse reflectance spectroscopy, hemoglobin, optical phantom, human brain
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:liu:diva-127362 (URN)10.1002/jbio.201500334 (DOI)000398216200012 ()27094015 (PubMedID)
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

Open Access in DiVA

omslag(3714 kB)23 downloads
File information
File name COVER01.pdfFile size 3714 kBChecksum SHA-512
be468d894cb5fb69f2c3cdcc065d5bdbdbcad79109736ccad17a93bc2e4438b5b17312b87a1af89476cfb4491c422858c10411da4f6d9977534f9f2a5ff1ff7a
Type coverMimetype application/pdf
fulltext(4249 kB)270 downloads
File information
File name FULLTEXT02.pdfFile size 4249 kBChecksum SHA-512
8a833378cf099902c7544e161a35dd0909fe963f9cf37e23cfac1ca2b3aaf37dc43cbc13639a1cf3a99cca18229200837437f1b0939325f1e0bcf10a245f0bb6
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Rejmstad, Peter
By organisation
Biomedical InstrumentationFaculty of Science & Engineering
Other Medical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 270 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
isbn
urn-nbn

Altmetric score

doi
isbn
urn-nbn
Total: 1165 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf