Information in full and reduced data sets of electrical impedance spectra from various skin conditions, compared using a holographic neural network

Information relating to patho-physiological events in living tissues, including skin, should be found in the beta-dispersion frequency range of the electrical impedance. For intact skin, the alpha-dispersion is strongly influenced by the condition of the stratum corneum, particularly its hydration. For intact skin, these dispersions are not well separated: in a Nyquist plot, most of the relatively small beta-dispersion will be hidden behind the upper-frequency end of the a-dispersion are. In the study, information obtained with a set of four indices, claimed to extract most of the information in the pertinent frequency interval, is compared with the full information measured at 31 frequencies, between f kHz and f MHz, for irritant and allergic contact reactions and nodular basal cell carcinomas, using a holographic neural network that appears to be useful for model-independent evaluation of the consequences of data-reduction procedures. Cole parameters should be avoided in the beta-range for intact skin. The indices are well supported, as long as differences from a reference site are used,and it seems that they can serve as the basis for differential diagnostics even as absolute values, although more information may be extracted from the complete spectrum.