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**7** 

*Russia* 

**Standards for Electrical** 

*Clinical Hospital #9, Yaroslavl* 

**Impedance Mammography** 

Marina Korotkova and Alexander Karpov

**1. Introduction** 

sectional slices of conductivity.

high frequency is employed in medical diagnostics.

**1.2 Tissue-specific peculiarities of electrical conductivity** 

**1.1 Imaging technique, employing feeble alternating current** 

Currently, a variety of electrical impedance diagnostic systems is used both in academic studies and in clinical practice. A significant part of such systems employs electrodes which reside in a single array and two-dimensional mathematical conductivity reconstruction algorithms in the array of the electrodes. Electrical impedance mammograph belongs to the class of 3D tomography systems. Thus, all the measurements are made on the surface of the object under investigation. The change of surface potential difference (compared with the homogeneous case), as a rule, is caused by the presence of a local heterogeneous area in the object. It is mainly concentrated in the area which is a projection of the local heterogeneous area on the surface of the object. Therefore, the main objective of electrical impedance mammography is to visualize the reconstructed three-dimensional electrical conductivity distribution of the object basing on the results of electrical measurements on its surface. For this purpose various modifications of mathematical method of "back projection" are employed. Mathematical methods provide also cross-

The usage of alternating current for this purpose is justified from several positions. Extreme complication of electrical conductivity measuring in biological systems at direct (i.e. unidirectional) current is conditioned by high degree of polarization of cellular membranes. Moreover, the flow of direct current through biological tissues is accompanied by irreversible chemical reactions at the electrodes, through which the object is connected with the external part of the circuit. Therefore, only alternating electric current of sufficiently

In biological tissue, electric current affects the components and structures that have a net electric charge and / or an electric dipole moment. This influence is carried out in an environment characterized by the presence of numerous interface regions. An example of such interface regions are cell membranes. In the space, surrounding cell membranes from both sides, the changes are carried by electric charges, mainly in the form of ions and the sources of dipole moment in the form of polar water molecules and mobile polar

