liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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
Inverse Monte Carlo for estimation of scattering and absorption in liquid optical phantoms
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.ORCID iD: 0000-0003-4377-8544
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-3454-6576
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.ORCID iD: 0000-0001-6385-6760
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2012 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 11, 12233-12246 p.Article in journal (Refereed) Published
Abstract [en]

A spectroscopic probe with multiple detecting fibers was used for quantifying absorption and scattering in liquid optical phantoms. The phantoms were mixtures of Intralipid and red and blue food dyes. Intensity calibration for the detecting fibers was undertaken using either a microsphere suspension (absolute calibration) or a uniform detector illumination (relative calibration between detectors). Two different scattering phase functions were used in an inverse Monte Carlo algorithm. Data were evaluated for residual spectra (systematic deviations and magnitude) and accuracy in estimation of scattering and absorption. Spectral fitting was improved by allowing for a 10% intensity relaxation in the optimization algorithm. For a multi-detector setup, non-systematic residual spectrum was only found using the more complex Gegenbauer-kernel phase function. However, the choice of phase function did not influence the accuracy in the estimation of absorption and scattering. Similar estimation accuracy as in the multi-detector setup was also obtained using either two relative calibrated detectors or one absolute calibrated detector at a fiber separation of 0.46 mm.

Place, publisher, year, edition, pages
Optical Society of America , 2012. Vol. 20, no 11, 12233-12246 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-78815DOI: 10.1364/OE.20.012233ISI: 000304403100070OAI: oai:DiVA.org:liu-78815DiVA: diva2:536040
Note

Funding Agencies|VINNOVA||Perimed AB|2008-00149|ResearchGrow program|2011-03074|European Union||Linkoping University through the Center for Excellence NIMED-CBDP (Center for Biomedical Data Processing)||

Available from: 2012-06-21 Created: 2012-06-21 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Model-based quantitative assessment of skin microcirculatory blood flow and oxygen saturation
Open this publication in new window or tab >>Model-based quantitative assessment of skin microcirculatory blood flow and oxygen saturation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The microcirculation, involving the smallest vessels in the body, is where the oxygen transport to all tissue occurs. Evaluating microcirculatory parameters is, therefore, important and involves the quantification of oxygen content of red blood cells (RBCs), the amount of RBCs and their speed.

Diffuse reflectance spectroscopy (DRS) can be used to estimate blood oxygen saturation and fraction of RBCs in tissue since oxygenated and deoxygenated blood have different light absorption characteristics. By illuminating the skin with white light and detecting the spectrum of the backscattered light, tissue absorption and scattering can be assessed. Laser Doppler flowmetry (LDF) is a technique to measure blood flow in tissue. When laser light encounter moving objects in tissue, i.e. RBCs, the light is Doppler shifted, which can be detected and used to calculate tissue perfusion (the fraction of moving RBCs times their speed). With a small distance between light source and detector, both techniques measure superficially where most vessels are microcirculatory vessels. Photon transport in tissue can be simulated with Monte Carlo techniques and the simulations form the basis of modeled DRS and LDF spectra. The estimated microcirculatory parameters are given by the model that best describe measured DRS and LDF data.

This thesis describes the development and the evaluation of an optical method to simultaneously measure oxygen saturation, RBC tissue fraction and speed resolved perfusion in absolute units by integrating DRS and LDF. By combining DRS and LDF into one system with a common tissue model, the two modalities can benefit from each other’s strengths. Different calibration methods and model assumptions for the system were evaluated in optical phantoms and in skin measurements. A simple calibration method with two detector distances for DRS was found adequate to accurately estimate absorption and scattering in optical phantoms. It was also necessary to model blood located in vessels, rather than homogeneously distributed in the skin, to obtain accurate parameter estimates. The system was evaluated in healthy subjects during standard provocations, where the parameters were in agreement with other studies and followed an expected pattern during the provocations. In patients with diabetes type 2, tissue fraction of RBCs and nutritive blood flow were reduced in baseline compared to healthy controls. These differences were not related to prevalence of microalbuminuria, a marker sign of microvascular complications in the kidneys.

A combined system with DRS and LDF enables a more comprehensive assessment of the microcirculation by measuring oxygen saturation, RBC tissue fraction and speed resolved perfusion simultaneously and in absolute units. This system has clinical potential to assist in the evaluation of the microcirculation both in healthy and diseased individuals.

Abstract [sv]

Mikrocirkulationen innefattar de minsta kärlen i kroppen och det är här syretransporten till all vävnad i kroppen sker. Det är därför viktigt att kunna utvärdera mikrocirkulatoriska parametrar såsom syresättningen hos de röda blodkropparna, mängden röda blodkroppar samt deras hastighet.

Diffus reflektansspektroskopi (DRS) kan användas för att beräkna syresättningen i blodet och mängden röda blodkroppar eftersom syresatt blod har ett karaktäristiskt sätt att absorbera ljus. Absorptionen och spridningen i vävnaden kan skattas genom att belysa huden med vitt ljus och mäta spektrumet från det tillbakaspridda ljuset. Laserdopplerbaserad flödesmätning (LDF) är en teknik som mäter blodflöde i vävnad. När laserljus träffar objekt i vävnaden som rör sig, t.ex. röda blodkroppar, så uppstår Dopplerskift. Dessa Dopplerskift kan detekteras och ett perfusionmått för vävnaden (mängden röda blodkroppar i rörelse gånger deras hastighet) kan beräknas. Med små avstånd mellan ljuskälla och detektor kan båda teknikerna mäta ytligt där den största delen av kärlen tillhör mikrocirkulationen. Fotontransporten i vävnad kan simuleras med Monte Carlo-teknik och simuleringarna ligger till grund för att modellera DRS- och LDF-spektra. De mikrocirkulatoriska parametrarna ges från den modellen som bäst passar DRS- och LDF-data.

Avhandlingen beskriver utvecklingen och utvärderingen av en optisk metod för att simultant mäta syresättningen, mängden röda blodkroppar och hastighetsupplöst perfusion i absoluta enheter genom att integrera DRS och LDF. Genom att kombinera DRS och LDF i ett system med en gemensam hudmodell kan de två modaliteterna dra nytta av varandras styrkor. Olika kalibreringsmetoder och modellantaganden för systemet utvärderades i optiska fantomer och i hudmätningar. En enkel kalibreringsmetod med två detektoravstånd för DRS visade sig vara tillräckligt för att kunna skatta absorption och spridning i optiska fantomer. Det var också nödvändigt att modellera blod i kärl istället för homogent fördelat i huden för att uppnå noggranna parameterskattningar. Systemet utvärderades under standardprovokationer på friska försökspersoner där parametrarna stämde överens med andra studier och följde ett förväntat mönster under provokationerna. Hos patienter med diabetes typ 2 sågs en minskad mängd röda blodkroppar och kapillärt blodflöde i oprovocerad hud jämfört med friska kontroller. Skillnaden var inte kopplad till förekomsten av mikroalbuminuri, ett tecken på mikrovaskulära komplikationer i njurarna.

Ett kombinerat system med DRS och LDF ger en mer fullständig bild av mikrocirkulationen genom att samtidigt och i absoluta enheter mäta syresättningen, mängden röda blodkroppar och hastighetsupplöst perfusion. Systemet kan användas för att utvärdera mikrocirkulationen både hos friska och sjuka individer.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 80 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1753
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-127691 (URN)10.3384/diss.diva-127691 (DOI)978-91-7685-801-1 (ISBN)
Public defence
2016-06-10, Berzeliussalen, Campus US, Linköping, 13:00 (English)
Opponent
Supervisors
Funder
VINNOVAEuropean Science Foundation (ESF)
Available from: 2016-05-24 Created: 2016-05-08 Last updated: 2016-05-24Bibliographically approved

Open Access in DiVA

fulltext(264 kB)708 downloads
File information
File name FULLTEXT01.pdfFile size 264 kBChecksum SHA-512
004dfb9c9da7088dfda4f17efa5bb87fefdf43538717428025e7deed69b147fc27a5b887869a28c454d19123087da47aa457d81a2b1259150eb6984e0898c641
Type fulltextMimetype application/pdf

Other links

Publisher's full text

Authority records BETA

Karlsson, HannaFredriksson, IngemarLarsson, MarcusStrömberg, Tomas

Search in DiVA

By author/editor
Karlsson, HannaFredriksson, IngemarLarsson, MarcusStrömberg, Tomas
By organisation
Biomedical InstrumentationThe Institute of Technology
In the same journal
Optics Express
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 708 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
urn-nbn

Altmetric score

doi
urn-nbn
Total: 526 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • 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