Abstract. The purpose of this research was to determine the diagnostic criteria for differentiating volu metric lesions in the mammary g land in electrical impedance mammography. The research was carried out utilizing the electrical impedance computer mammograph «MEIK v.5.6» ® , which enables to acquire images of 3-D conductivity distribution layers within mamma's tissues up to 5 cm depth . The weighted reciprocal projection method was emp loyed to reconstruct the 3-D electric conductivity distribution of the examined organ. The results of 3,710 electrical impedance examinations were analyzed. The analysis of a volumetric lesion included assessment of its shape, contour, internal electrical structure and changes of the surrounding tissues. Moreover, mammary gland status was evaluated with the help of comparative and age-related electrical conductivity curves. The diagnostic chart is provided. Each criterion is measured in points. Using the numerical score for evaluation of mass and non-volumetric lesions within the mammary gland in electrical impedance mammography allowed co mparing this information to BI -RADS categories developed by American Co llege of Rad iology experts. The article is illustrated with electrical impedance mammograms and tables .

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Electrical impedance mammography (EIM) belongs to nonlocal techniques of image creation. It is based on a number of data collection methods, including the cross-sectional approach, the back-projection method with the weight function applied horizontally and vertically, and the static image method. The analysis of data acquired by applying the above methods enabled to work out the EIM diagnostic system. It involves the following diagnostic categories: structural percentile limits and the mammary gland structure, agerelated percentile limits and age-related electric conductivity, outlying values statistics and early diagnostics of breast cancer, D-statistics and distortion of the mammographic scheme in the presence of breast cancer, diagnostic table, and the assessment of the electrical impedance image.

The article presents the result of the electrochemical testing of the potential electric impedance mammograph "MEIK" (version 5.6) which reconstructs the image using the reciprocal projection method. The testing was carried out on several categories: biological objects visualization, definition size, location, depth and shape of the biological objects, concentration and electrical conductivity, resolution capability. The research has been conducted in the original tank filled with homogeneous and heterogeneous medium. The research of the visualization of abiological and bialogical objects, objects dimensions, objects location, objects structure. According to the data of the electrochemical testing, the resolution capability of the objects with high electrical conductivity ranges from 1 to 3 mm and of the objects with low electrical conductivity-from 3 to 5 mm. Due to the given electrochemical testing results potencial electric impedance mammograph "MEIK" (version 5.6) can be rated as the medical visualization device.