Electrical bio-impedance can be used to assess skin cancers and other cutaneous lesions. The aim of this study was to distinguish skin cancer from benign nevi using multifrequency impedance spectra. Electrical impedance spectra of about 100 skin cancers and 511 benign nevi were measured. Impedance of reference skin was measured ipsi-laterally to the lesions. The impedance relation between lesion and reference skin was used to distinguish the cancers from the nevi. It was found that it is possible to separate malignant melanoma from benign nevi with 75% specificity at 100% sensitivity, and to distinguish nonmelanoma skin cancer from benign nevi with 87% specificity at 100% sensitivity. The power of skin cancer detection using electrical impedance is as good as, or better than, conventional visual screening made by general practitioners.

No abstract

For a full understanding of the properties of the human skin barrier, physical macroscopic parameters of barrier function must be correlated to the structural organization of the barrier on a molecular level. This study was undertaken to relate differences in the relative composition of the three main lipid classes of human stratum corneum, i.e., free fatty acids, cholesterol, and ceramides, to differences in transepidermal water loss, stratum corneum electrical impedance, and corneometer value. A new high performance liquid chromatography/light scattering detection-based analysis method recently developed was used for collection of quantitative lipid data in conjunction with gas chromatography/mass spectrometry/flame ionization detection measurements on the free fatty acid fraction. After subtraction of contaminating lipid fractions we have estimated the molar ratio of the human skin barrier lipid composition to be, respectively, 15% cholesterol esters, 16% saturated long chain free fatty acids, 32% cholesterol, and 37% ceramides. The inter-individual difference in the relative amount of free fatty acids, cholesterol, and ceramides, respectively, can be >100% in the individual case. It was found that the relative amount of ceramides to cholesterol is larger in the wrist area, paralleled by a higher transepidermal water loss and corneometer value as well as different skin electrical impedance values as compared with the upper forearm area. We conclude that the site-dependent differences in the stratum corneum lipid composition are small compared with the large inter-individual variation. Interestingly, in the individual case, no correlation was registered between relative ceramide content and barrier properties.

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 model's 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.

The results suggest that electrical impedance spectra can distinguish between malignant melanoma and benign skin lesions. Although it is indicated that the accuracy of the device is clinically promising, the overall performance, and the sensitivity to thin malignant melanomas, must be improved and thoroughly validated before the instrument can be used as a routine stand-alone diagnostic decision support tool. The technique is under revision to further improve the reproducibility, specificity and sensitivity.