A system for measuring electrical impedance in human tissues comprising a plurality of needles; said plurality of needles being arranged along a circumference; where said plurality of needles have a length greater than 0.5 cm; said plurality of needles being coated with an electrically insulating material throughout their entire length except for a portion having a maximum length of 0.5 mm; each of said plurality of needles being connected to a multiplexer; an alternating-current generator being connected to an input of said multiplexer; where said current generator is configured to send a current at at least two different frequencies ranging between 10 Hz and 1 MHz; a voltmeter being connected to an output of said multiplexer; a control centre connecting selectively and in succession said current generator to first two needles of said plurality of needles; said control centre being configured to control said multiplexer so as to connect selectively and in succession said voltmeter to second two needles of said plurality of needles according to a predefined scheme; said control centre being configured to measure the impedance between said second two needles at said at least two frequencies and repeat the measurements on all pairs of the needles; said control centre being configured to calculate an image, having a size substantially equal to that of said circumference, for each of said at least two frequencies corresponding to said measurement of the impedance between said second two needles; said control centre being configured to supply said image to a system for displaying said image; wherein said plurality of needles are N greater than 3 to be evenly distributed in one and the same plane and the number of measurements for reconstructing the image is computed as N(N - 3) for each frequency. said plurality of needles being arranged along a circumference; where said plurality of needles have a length greater than 0.5 cm; said plurality of needles being coated with an electrically insulating material throughout their entire length except for a portion having a maximum length of 0.5 mm; each of said plurality of needles being connected to a multiplexer; an alternating-current generator being connected to an input of said multiplexer; where said current generator is configured to send a current at at least two different frequencies ranging between 10 Hz and 1 MHz; a voltmeter being connected to an output of said multiplexer; a control centre connecting selectively and in succession said current generator to first two needles of said plurality of needles; said control centre being configured to control said multiplexer so as to connect selectively and in succession said voltmeter to second two needles of said plurality of needles according to a predefined scheme; said control centre being configured to measure the impedance between said second two needles at said at least two frequencies and repeat the measurements on all pairs of the needles; said control centre being configured to calculate an image, having a size substantially equal to that of said circumference, for each of said at least two frequencies corresponding to said measurement of the impedance between said second two needles; said control centre being configured to supply said image to a system for displaying said image; wherein said plurality of needles are N greater than 3 to be evenly distributed in one and the same plane and the number of measurements for reconstructing the image is computed as N(N - 3) for each frequency.