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Sub-epidermal imaging using polarized light spectroscopy for assessment of skin microcirculation
Department of Physics, University of Limerick, Plassey Technological Park, Limerick, Ireland.
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine.
Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Dermatology and Venerology . Östergötlands Läns Landsting, Centre for Medicine, Department of Dermatology and Venerology in Östergötland.
Department of Physics, University of Limerick, Plassey Technological Park, Limerick, Ireland.
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2007 (English)In: Skin research and technology, ISSN 0909-752X, Vol. 13, no 4, 472-484 p.Article in journal (Refereed) Published
Abstract [en]

Background/aims: Many clinical conditions that affect the microcirculation of the skin are still diagnosed and followed up by observational methods alone in spite of the fact that non-invasive, more user-independent and objective methods are available today. Limited portability, high cost, lack of robustness and non-specificity of findings are among the factors that have hampered the implementation of these methods in a clinical setting. The aim of this study is to present and evaluate a new, portable and easy-to-use imaging technology for investigation of the red blood cell (RBC) concentration in the skin microvasculature based on the method of polarization light spectroscopy using modified standard digital camera technology.

Methods: The use of orthogonal linear polarization filters over both the flash source and the detector array removes the polarization-retaining light reflected from the epidermal layer. Only the depolarized light backscattered from the papillary dermal matrix reaches the detector array. By separating the RGB color planes of an image acquired in this manner and applying a dedicated image processing algorithm, spectroscopic information about the chromophores in the dermal tissue can be attained. If the algorithm is based on a differential principle in which the normalized differences between the individual values of the red and green color plane are calculated, tissue components with similar spectral signature in both planes are suppressed, while components with different spectral signatures such as RBCs are enhanced.

Results: In vitro fluid models compare well with theory and computer simulations in describing a linear relationship between the imager output signal termed the tissue viability index (TiVi index) and RBC concentration in the physiological range of 0-4% RBC fraction of tissue volume (cc=0.997, n=20). The influence of oxygen saturation on the calculated RBC concentration is limited to within -3.9% for values within the physiological range (70-100% oxygen saturation). Monte Carlo simulations provide information about the sampling depth (about 0.5mm on the average) of the imaging system. In vivo system evaluation based on iontophoresis of acetylcholine displays a heterogeneous pattern of vasodilatation appearing inside the electrode area after about 10min. Topical application of methyl nicotinate and clobetasol propionate further demonstrates the capacity to document the extent and intensity of both an increase (erythema) and a decrease (blanching) in the skin RBC concentration without movement artifact and with compensation for irregularity in pigmentation.

Conclusions: Polarization light spectroscopy imaging for assessment of RBC concentration in the skin microvasculature is a robust and accessible technique for the clinical setting. Additionally, the technique has pre-clinical research applications for investigation of the spatial and temporal aspects of skin erythema and blanching as well as a potential role in drug development, skin care product development and skin toxicological assessment.

Place, publisher, year, edition, pages
2007. Vol. 13, no 4, 472-484 p.
Keyword [en]
Biomedical optics, Blanching, Erythema, Microcirculation, Polarizationspectroscopy
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-48066DOI: 10.1111/j.1600-0846.2007.00253.xOAI: diva2:268962
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2009-10-13Bibliographically approved
In thesis
1. Assessment of microvascular effects of vasoactive drugs: Methodological in vivo studies in humansbased on iontophoresis
Open this publication in new window or tab >>Assessment of microvascular effects of vasoactive drugs: Methodological in vivo studies in humansbased on iontophoresis
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular disease is the leading cause of death in western societies and endothelial dysfunction is one of the earliest signs seen in the development of such conditions. Thedevelopment of prognostic tools to aid in the prediction of micro- and macrovascular diseasebased on assessment of vascular reactivity is therefore of paramount importance.

Transdermal iontophoresis offers a quick, non-invasive and relatively straightforward way todeliver vasoactive substances in order to provoke a vascular response in man. When combined with either laser Doppler flowmetry (LDF) or tissue viability imaging (TiVi) for quantification of these responses the methodology offers a potentially powerful tool forvascular investigations. The technique has, however, not been established in clinical practice yet and is mostly used in experimental settings. The lack of consensus in what data analysistechnique to use, uncertainty concerning the actual drug dose applied, and the difficulties associated with the assessment of responses to vasoconstrictors may have contributed to thisfact. The aim of this thesis is therefore to address these issues and thus facilitate the use and improve the applicability of transdermal iontophoresis for assessment of cutaneous microvascular function.

More specifically, a non-linear dose-response model (Emax-model) that is commonly used in in vitro investigations of vascular function was applied to the iontophoresis data. The resultsshow that the Emax-model accurately describes the cutaneous vascular responses totransdermally iontophoresed acetylcholine (ACh) and, sodium nitroprusside (SNP). The Emaxmodelgenerates variables that can be used for quantitative statistical analysis of data andenables a more powerful analysis compared to the methods presently used. It is furtherdemonstrated that the maximal dose effect and vascular responses vary between differentprotocols with the same total iontophoretic charge but with different current strengths anddurations. This finding implies that the assumption that the local drug dose is linearlyproportional to the iontophoretic charge (used for estimation of delivered drug dose to themicrovascular bed) may be inaccurate in in vivo investigations and that there is need for amore refined model.

It is also demonstrated that in a vasoconstrictive setting (iontophoresis of noradrenaline andphenylephrine) TiVi is the favourable technique for measuring vascular responses as it issensitive enough to generate data that can be fitted to the Emax-model even without predilatationof the vessels.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 47 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1125
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-50642 (URN)978-91-7393-638-5 (ISBN)
Public defence
2009-11-06, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Available from: 2009-10-13 Created: 2009-10-13 Last updated: 2009-10-13Bibliographically approved

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