A.V. Kobelev1, A.N. Briko2, S.I. Shchukin3

1–3 Moscow Bauman State Technical University (Moscow, Russia)
1 briko@bmstu.ru

Background. The contribution of biological tissues at different depths to the electrical impedance signal depends on the geometry of the electrode system. The areas located in the immediate vicinity of the electrodes have the greatest influence on the measured signal, but to optimize the design, it is necessary to understand the ultimate capabilities of the electrode system in terms of "depth sensitivity". In electrical exploration, the effective depth of exploration, reflecting the capabilities of the electrode system, is estimated by the effective probing depth. This approach leads to contradictions. In foreign literature, the "median depth of exploration" according to Edwards is used – this is the depth below which half of the total power from the current source is dissipated. The obtained estimates of the "median depth" are 4-5 times smaller than the dimensions of the electrode system and do not allow us to estimate the ultimate capabilities of the electrode system in depth.

Aim. To analyze existing approaches to assessing the sensitivity of tetrapolar electrode systems depending on the depth of the study area, identify existing contradictions and propose a way to eliminate them.

Results. A new concept is introduced – the event horizon of the electrode system, which characterizes its capabilities for studying heterogeneities at a certain depth. The concept of the event horizon depends on the location of both the current and measuring electrodes and satisfies the principle of reciprocity. The results of experimental verification of the obtained analytical expressions are presented.

Practical significance. The obtained results can be applied in the development of tetrapolar electrode systems for electrical impedance studies.

Kobelev A.V., Briko A.N., Shchukin S.I. On the issue of probing depth of tetrapolar electrode systems in electrical impedance myography. Biomedicine Radioengineering. 2024. V. 27. № 6. P. 5–19. DOI: https:// doi.org/10.18127/j15604136-202406-01 (In Russian)

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