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In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry
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.
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2003 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 7-8, 124-134 p.Article in journal (Refereed) Published
Abstract [en]

Methods for local photon pathlength and optical properties estimation, based on measured and simulated diffuse reflectance within 2mm from the light source, are proposed and evaluated in vivo on Caucasian human skin. The accuracy of the methods was good (2-7%) for pathlength and reduced scattering but poor for absorption estimation. Reduced scattering and absorption were systematically lower in the fingertip than in the forearm skin (633 nm). A maximum intra-site and inter-individual variation of ~35% in the average photon pathlength was found. The methodology was applied in laser Doppler flowmetry (LDF), where pathlength normalization of the estimated perfusion removed the optical property dependency.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik , 2003. Vol. 42, no 7-8, 124-134 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-11658DOI: 10.1364/AO.42.000124OAI: oai:DiVA.org:liu-11658DiVA: diva2:18068
Note
Larsson, M., Nilsson, H. & Strömberg, T., In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry, 2003, Applied Optics, (42), 7-8, 124-134. http://dx.doi.org/10.1364/AO.42.000124. This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://ao.osa.org/abstract.cfm?id=70860. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. Copyright OSA., http://www.osa.org/Available from: 2008-04-24 Created: 2008-04-24 Last updated: 2017-12-13
In thesis
1. Influence of optical properties on Laser Doppler Flowmetry
Open this publication in new window or tab >>Influence of optical properties on Laser Doppler Flowmetry
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Laser Doppler flowmetry (LDF) is based on the principle that a Doppler shift occurs when coherent light is scattered by a moving object, i.e. red blood cell (RBC). The magnitude of these frequency shifts affects the optical beating that occurs w hen shifted and non-shifted light is mixed. Based on the optical beating, an LDF perfusion measure is calculated. However, the measure is not only sensitive to the RBC velocity and concentration, but also to the photon path Jength in tissue and the scattering characteristics of the RBC. The Jatter two are both govemed by the optical properties (OP), attributes that differ both within and between individuals.

The aim of this thesis was to evaluate how the RBC and tissue OP affect the LDF perfusion measure, and to propose methods that partly correct for these errors. Phantom measurements and Monte Carlo simulations showed that the LDF perfusion was significantly affected by variations in OP relevant to skin, especially when comparing individual readings. Simulations revealed that the variations in OP affected the LDF perfusion and the photon path length in a similar manner. This suggests that a path length normalised measure would decrease the OP induced variations, possibly enabling accurate intra and inter-individual comparisons of LDF perfusion measures in different organs.

A path length estimation technique, based on spatially diffuse reflectance, is proposed and evaluated. Monte Carlo simulations showed that the algorithm predicted the photon path length with an rms error of less than 5%. In vivo measurement (11 subjects) displayed a longer estimated path length (~35%) for the fingertip compared to the forearm. Comparing individual measurements from similar locations, variations up to 40% (max/min) were found. These findings clearly indicate the need for a path length normalization when comparing LDF readings.

The LDF Doppler spectrum is govemed by the RBC velocity distribution and its phase function. In this thesis, an approach is presented where a measured LDF Doppler spectrum is decomposed using a number of theoretical, single-velocity spectra. As a result, a velocity-resolved perfusion measure is achieved. As the blood flow velocity depends on the dimension of the blood vessel, this approach has the potential to differentiate between arteriole/ venule and capillary activity. In addition, the path length estimation technique and the RBC scattering theory, presented in this thesis, provides a promising step towards an absolute perfusion measure.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2004. 64 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 914
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28932 (URN)14139 (Local ID)91-85297-04-6 (ISBN)14139 (Archive number)14139 (OAI)
Public defence
2004-12-17, Sal Eken, Universitetssjukhuset, Linköping, 09:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2016-08-31

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Larsson, MarcusStrömberg, Tomas

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