Ulrik Birgersson

Electrical impedance spectroscopy and the diagnostic accuracy for malignant melanoma

Abstract:  Background:  The accuracy of diagnosis of skin cancer and especially of early malignant melanoma is most important to reduce its morbidity and mortality. Previous pilot studies using electrical impedance measurements indicate statistically significant accuracies for the detection of skin cancer.

Clinical performance of the Nevisense system in cutaneous melanoma detection: an international, multicentre, prospective and blinded clinical trial on efficacy and safety.

Even though progress has been made, the detection of melanoma still poses a challenge. In light of this situation, the Nevisense electrical impedance spectroscopy (EIS) system (SciBase AB, Stockholm, Sweden) was designed and shown to have the potential to be used as an adjunct diagnostic tool for melanoma detection.

Non-invasive bioimpedance of intact skin: mathematical modeling and experiments

The functional integrity and pathology of the skin is reflected in its electrical impedance spectra. Non-invasive electrical impedance measurements of intact skin are dominated by the high impedic stratum corneum in low frequencies and with increasing frequency gradually comes to be dominated by viable skin. Models of this multi-layered organ can increase our understanding of the actual physical properties/dimensions and facilitate better diagnostics in certain applications. Therefore, a mathematical model considering conservation of charge in the various layers of the skin and adjacent electrodes is derived and validated with experimental findings; the latter was carried out on 60 young female subjects. The impact of the stratum corneum thickness, inundation, solvent and cohort size on the electrical properties is studied. Both model parameters and experimental conditions were adjusted for calibration and subsequent validation of the model with measurements. It is found that both the models thickness of the stratum corneum as well as experimental soaking conditions (both time and saline concentration) affect the fit between the model and measurements. It is concluded that it is essential that the electrical properties of the skin are presented in the context of the ion concentration (if a moisturizer is employed) as well as the soaking time. Further refinements should be made to determine even more accurate dielectrical properties of the stratum corneum and viable skin layers by accounting for the true skin thickness and the heterogeneity of the skin layers-this would be useful in applications where subtle alterations in the skin are of interest.

Electrical impedance spectroscopy as a potential adjunct diagnostic tool for cutaneous melanoma

Previous studies have shown statistically significant differences in electrical impedance between various cutaneous lesions. Electrical impedance spectroscopy (EIS) may therefore be able to aid clinicians in differentiating between benign and malignant skin lesions.

Estimating electrical properties and the thickness of skin with electrical impedance spectroscopy: Mathematical analysis and measurements

Abstract Electrical impedance spectroscopy (EIS) allows for the study and characterization of tissue alterations and properties associated with the skin. Here, the potential application of EIS to estimate the thickness of the stratum corneum is explored in the form of a mathematical model for EIS, which is analyzed in the limit of 1 kHz and closed-form analytical solutions derived. These analytical expressions are verified with the numerical solution of the full set of equations and validated with an EIS study comprising 120 subjects: overall, good agreement is found in the frequency range 1-100 kHz, where the impedance is governed by the stratum corneum. Combining the closed-form expression for the thickness of the stratum corneum predicted by the model with the experimental EIS measurements, a distribution for the stratum corneum thickness of the subjects is found with a mean and standard deviation that agree well with reported stratum corneum thicknesses from other experimental techniques. This, in turn, suggests that EIS could be employed to measure the thickness of the stratum corneum with reasonable accuracy. In addition, the electrical properties relevant to EIS – conductivity and relative permittivity – of the stratum corneum can be estimated with the closed form expressions if the stratum corneum thickness is known.

Analysis of a mechanistic model for non-invasive bioimpedance of intact skin

Abstract 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.

Evolution of a Diagnostic Decision Support Tool Based on Electrical Impedance

Among physical properties of tissues, electrical impedance stands out as a potentially useful method to monitor alterations. Our aim is to bridge the gap between idea and product by understanding and overcoming the scientific, technical, financial, clinical, regulatory, and market challenges. Micro-invasive electrodes add benefits to deep skin measurements by overcoming the stratum corneum, and data can be analyzed and classified using methods which do not suffer from a preconceived paradigm. Venture capitalists (VC) are interested in new technologies if there is a market, and if the technology is protected by patents or similar rights. A medical device also has to fulfill a number of regulatory requirements. It was found early that popular lumped parameter methods were not adequate to characterize clinically relevant alterations in skin. Simple indices were tried, which proved sufficient to quantify and classify experimentally elicited reactions in skin and oral mucosa. To improve sensitivity and specificity, more information was extracted using various multivariate techniques, and proof-ofprinciple for a skin cancer detector was achieved.