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A laser Doppler system for monitoring of cerebral microcirculation: implementation and evaluation during neurosurgery
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. (MINT)
Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). (MINT)ORCID iD: 0000-0002-0012-7867
2016 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, ISSN 0140-0118, Vol. 54, no 1, 123-131 p.Article 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. Vol. 54, no 1, 123-131 p.
Keyword [en]
Microcirculation, Brain tumour Laser Doppler perfusion monitoring (LDPM), Pulsatility index (PI), Neurosurgery
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-120632DOI: 10.1007/s11517-015-1332-5ISI: 000371437900010PubMedID: 26105147OAI: oai:DiVA.org:liu-120632DiVA: diva2:847367
Funder
Swedish Research Council, 6212-010-4216
Available from: 2015-08-20 Created: 2015-08-20 Last updated: 2017-12-04Bibliographically 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, PeterÅneman, OscarWårdell, Karin
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