Il est etabli que le courant de basse frequence est limite a l'espace extracellulaire, tandis... more Il est etabli que le courant de basse frequence est limite a l'espace extracellulaire, tandis que de plus hautes frequences sont transmises par capacite a travers les membranes cellulaires. Un des types d'irritation de la peau est l'oedeme extracellulaire. Un index d'impedance, ou index d'irritation, defini comme le quotient du module de l'impedance a 20kHz et de celui a 1MHz, a ete observe etre le plus sensible a des reactions irritatives provoquees par le lauryl-sulfate de sodium (SLS) a des concentrations plus basses que celles produisant une modification visible de la peau. Des spectres d'impedance electrique entre 1kHz et 1MHz ont ete mesures a cinq profondeurs. Les resultats ont ete mis en relation avec l'aspect histologique des differentes couches de la peau. L'observation dominante a ete un epaississement de l'epiderme du a l'œdeme. La plus grande amplitude du signal d'impedance a ete constatee pour une profondeur de mesure comprenant tout l'epiderme. Du point de vue de l'EIT, nos experiences suggerent d'imbiber la peau avec le SLS pour provoquer une legere dermatite avant les mesures. Une telle lesion, faible et reversible, de la peau entraine une amelioration importante des proprietes conductrices de la peau. Cela devrait diminuer les distorsions en EIT dues a l'interface electrode/peau.
Page 1. PREDICTION OF BIO-IMPEDANCE PROPERTIES OF CHEMICALLY INDUCED SKIN IRRITATIONS Peter Åberg... more Page 1. PREDICTION OF BIO-IMPEDANCE PROPERTIES OF CHEMICALLY INDUCED SKIN IRRITATIONS Peter Åberg a , Ingrid Nicander b , Paul Geladi c ,Stig Ollmar a a Karolinska Institutet, Medical Engineering, Novum ...
Our aim is to establish an objective, easy-to-use technique to evaluate tissue irritation in vivo... more Our aim is to establish an objective, easy-to-use technique to evaluate tissue irritation in vivo using non-invasive electrical impedance measurements. Such a technique would facilitate testing the biocompatibility of various materials, and also in quantifying skin diseases and other processes involving structural changes. It has been found that irritation of the oral mucosa not clinically or histologically discernible could be detected with a simple device based on electrical impedance techniques. Originally, the key problem was to focus the probing electrical field in order to minimize artefacts emanating from tissue layers of no interest. The device was then refined and applied to skin testing. It was found that irritation effects far below the limit of the commonly used visual readings could be detected. In this case, it is desirable to exclude from the measurement tissue layers with no diagnostic information, or at least reduce their influence. In this paper, the essential step...
We determine the in-vivo dielectric properties—resistivity and relative permittivity—of living ep... more We determine the in-vivo dielectric properties—resistivity and relative permittivity—of living epidermis and dermis of human skin soaked with a physiological saline solution for one minute between 1 kHz and 1 MHz. This is done by fitting approximate analytical solutions of a mechanistic model for the transport of charges in these layers to a training set comprising impedance measurements at two depth settings on stripped skin on the volar forearm of 24 young subjects. Here, the depth settings are obtained by varying the voltage at a second inject on the electrical-impedance-spectroscopy probe. The model and the dielectric properties are validated with a test set for a third depth setting with overall good agreement. In addition, the means and standard deviations of the thicknesses of living epidermis and dermis are estimated from a literature review as 61±7 μm and 1.0±0.2 mm respectively. Furthermore, extensions to resolve the skin layers in more detail are suggested.
A mechanistic mathematical model for electrical impedance spectroscopy (EIS) measurements of huma... more A mechanistic mathematical model for electrical impedance spectroscopy (EIS) measurements of human skin is analyzed, leading to a reduced model and approximate solutions. In essence, the model considers a complex-valued Laplace equation in the frequency domain for the alternating current from a circular EIS probe passing through the layers – stratum corneum, viable skin and adipose tissue – of human skin in the frequency range 1 kHz – 1 MHz. The reduced model, which only needs to be solved numerically for the viable skin with modified boundary conditions, is verified with the full set of equations (non-reduced model): good agreement is found with a maximum relative error of less than 3%. A Hankel transform of the reduced model allows for approximate solutions of not only the measured impedance but also the point-wise potential distribution in the skin. In addition, the dimensionless numbers governing the EIS are elucidated and discussed.
Bio-electrical impedance spectra of skin cancer and other lesions can be assessed using both regu... more Bio-electrical impedance spectra of skin cancer and other lesions can be assessed using both regular non-invasive probes and a novel type of microinvasive electrode system with a surface furnished with tiny spikes that penetrate stratum corneum. The aim of the study was to compare the accuracy of detection for various types of skin cancer using impedance spectra measured with these two different electrode systems in an objective way without optimising the power of discrimination. Impedance spectra of 99 benign nevi, 28 basal cell carcinomas (BCC), and 13 malignant melanomas (MM) were measured using the two electrode systems. Classification of the lesions was made using Fisher's linear discriminant, and the sensitivities and specificities of the techniques were estimated using cross-validation. The best separation between nevi and BCC was achieved using the regular non-invasive probe (96% sensitivity and 86% specificity), whereas the best separation between nevi and MM was achieved using the microinvasive electrodes (92% sensitivity and 80% specificity). Our results indicate that the choice of electrode system is application dependent.
27 Within and beyond the Skin Barrier as Seen by Electrical Impedance Stig Ollmar and ... 18.Mart... more 27 Within and beyond the Skin Barrier as Seen by Electrical Impedance Stig Ollmar and ... 18.Martinsen, ØG, Grimnes, S., and Sveen, O., Dielectric properties of the epidermal stratum corneum ... Rantanen, I., Nicander, I., Jutila, K., Ollmar, S., Tenovuo, J., and Söderling, E., Betaine ...
2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2001
We present predictive models that can foresee how skin will react when exposed to chemicals. Skin... more We present predictive models that can foresee how skin will react when exposed to chemicals. Skin impedance spectra, 31 frequencies between 1 and 1000 kHz at five depth settings, were collected before and after application of chemicals on volar forearms of volunteers. Tegobetaine and sodium lauryl sulphate were used to induce the irritations. The spectra were filtered using orthogonal signal
Il est etabli que le courant de basse frequence est limite a l'espace extracellulaire, tandis... more Il est etabli que le courant de basse frequence est limite a l'espace extracellulaire, tandis que de plus hautes frequences sont transmises par capacite a travers les membranes cellulaires. Un des types d'irritation de la peau est l'oedeme extracellulaire. Un index d'impedance, ou index d'irritation, defini comme le quotient du module de l'impedance a 20kHz et de celui a 1MHz, a ete observe etre le plus sensible a des reactions irritatives provoquees par le lauryl-sulfate de sodium (SLS) a des concentrations plus basses que celles produisant une modification visible de la peau. Des spectres d'impedance electrique entre 1kHz et 1MHz ont ete mesures a cinq profondeurs. Les resultats ont ete mis en relation avec l'aspect histologique des differentes couches de la peau. L'observation dominante a ete un epaississement de l'epiderme du a l'œdeme. La plus grande amplitude du signal d'impedance a ete constatee pour une profondeur de mesure comprenant tout l'epiderme. Du point de vue de l'EIT, nos experiences suggerent d'imbiber la peau avec le SLS pour provoquer une legere dermatite avant les mesures. Une telle lesion, faible et reversible, de la peau entraine une amelioration importante des proprietes conductrices de la peau. Cela devrait diminuer les distorsions en EIT dues a l'interface electrode/peau.
Page 1. PREDICTION OF BIO-IMPEDANCE PROPERTIES OF CHEMICALLY INDUCED SKIN IRRITATIONS Peter Åberg... more Page 1. PREDICTION OF BIO-IMPEDANCE PROPERTIES OF CHEMICALLY INDUCED SKIN IRRITATIONS Peter Åberg a , Ingrid Nicander b , Paul Geladi c ,Stig Ollmar a a Karolinska Institutet, Medical Engineering, Novum ...
Our aim is to establish an objective, easy-to-use technique to evaluate tissue irritation in vivo... more Our aim is to establish an objective, easy-to-use technique to evaluate tissue irritation in vivo using non-invasive electrical impedance measurements. Such a technique would facilitate testing the biocompatibility of various materials, and also in quantifying skin diseases and other processes involving structural changes. It has been found that irritation of the oral mucosa not clinically or histologically discernible could be detected with a simple device based on electrical impedance techniques. Originally, the key problem was to focus the probing electrical field in order to minimize artefacts emanating from tissue layers of no interest. The device was then refined and applied to skin testing. It was found that irritation effects far below the limit of the commonly used visual readings could be detected. In this case, it is desirable to exclude from the measurement tissue layers with no diagnostic information, or at least reduce their influence. In this paper, the essential step...
We determine the in-vivo dielectric properties—resistivity and relative permittivity—of living ep... more We determine the in-vivo dielectric properties—resistivity and relative permittivity—of living epidermis and dermis of human skin soaked with a physiological saline solution for one minute between 1 kHz and 1 MHz. This is done by fitting approximate analytical solutions of a mechanistic model for the transport of charges in these layers to a training set comprising impedance measurements at two depth settings on stripped skin on the volar forearm of 24 young subjects. Here, the depth settings are obtained by varying the voltage at a second inject on the electrical-impedance-spectroscopy probe. The model and the dielectric properties are validated with a test set for a third depth setting with overall good agreement. In addition, the means and standard deviations of the thicknesses of living epidermis and dermis are estimated from a literature review as 61±7 μm and 1.0±0.2 mm respectively. Furthermore, extensions to resolve the skin layers in more detail are suggested.
A mechanistic mathematical model for electrical impedance spectroscopy (EIS) measurements of huma... more A mechanistic mathematical model for electrical impedance spectroscopy (EIS) measurements of human skin is analyzed, leading to a reduced model and approximate solutions. In essence, the model considers a complex-valued Laplace equation in the frequency domain for the alternating current from a circular EIS probe passing through the layers – stratum corneum, viable skin and adipose tissue – of human skin in the frequency range 1 kHz – 1 MHz. The reduced model, which only needs to be solved numerically for the viable skin with modified boundary conditions, is verified with the full set of equations (non-reduced model): good agreement is found with a maximum relative error of less than 3%. A Hankel transform of the reduced model allows for approximate solutions of not only the measured impedance but also the point-wise potential distribution in the skin. In addition, the dimensionless numbers governing the EIS are elucidated and discussed.
Bio-electrical impedance spectra of skin cancer and other lesions can be assessed using both regu... more Bio-electrical impedance spectra of skin cancer and other lesions can be assessed using both regular non-invasive probes and a novel type of microinvasive electrode system with a surface furnished with tiny spikes that penetrate stratum corneum. The aim of the study was to compare the accuracy of detection for various types of skin cancer using impedance spectra measured with these two different electrode systems in an objective way without optimising the power of discrimination. Impedance spectra of 99 benign nevi, 28 basal cell carcinomas (BCC), and 13 malignant melanomas (MM) were measured using the two electrode systems. Classification of the lesions was made using Fisher's linear discriminant, and the sensitivities and specificities of the techniques were estimated using cross-validation. The best separation between nevi and BCC was achieved using the regular non-invasive probe (96% sensitivity and 86% specificity), whereas the best separation between nevi and MM was achieved using the microinvasive electrodes (92% sensitivity and 80% specificity). Our results indicate that the choice of electrode system is application dependent.
27 Within and beyond the Skin Barrier as Seen by Electrical Impedance Stig Ollmar and ... 18.Mart... more 27 Within and beyond the Skin Barrier as Seen by Electrical Impedance Stig Ollmar and ... 18.Martinsen, ØG, Grimnes, S., and Sveen, O., Dielectric properties of the epidermal stratum corneum ... Rantanen, I., Nicander, I., Jutila, K., Ollmar, S., Tenovuo, J., and Söderling, E., Betaine ...
2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2001
We present predictive models that can foresee how skin will react when exposed to chemicals. Skin... more We present predictive models that can foresee how skin will react when exposed to chemicals. Skin impedance spectra, 31 frequencies between 1 and 1000 kHz at five depth settings, were collected before and after application of chemicals on volar forearms of volunteers. Tegobetaine and sodium lauryl sulphate were used to induce the irritations. The spectra were filtered using orthogonal signal
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