Patent ID: 6236886
Filing Date: 2001-05-22
Classification: A61B

Abstract:
A method for the construction of images of a body using electrical impedance tomography, comprising:a) placing a series of contact electrodes at spaced intervals on the surface of a body;b) selecting a pair of electrodes for a set of potential difference measurements, each measurement made by connecting an electric current source to pairs of non-selected electrodes sequentially, said pairs of electrically connected electrodes being separated by at least two other electrodes;c) selecting different pairs of measurement electrodes and repeating step b) for each pair until all pairs of measurement electrodes had been selected;d) determining the reference values of the potential differences ##EQU25##by the approximation of the measured distribution of the potential differences ##EQU26##in accordance with the expression ##EQU27##while the electric current source is connected to the i.sup.th pair of electrodes, and where i is the number of the exciting pair of electrodes, j is the number of the measuring pair of electrodes, ##EQU28##is the given distribution of voltage between adjacent electrodes along the boundary of the reference object, ##EQU29##are signals caused by spurious couplings, and ##EQU30##are the approximating coefficients of the measured distribution of the potential differences; ande) reconstructing the image of the spatial distribution of conductivity of said body by back projection along equipotential lines according to the expressions: ##EQU31## ##EQU32##where W.sup.lt, W.sup.rt are weighting factors determined according to the procedure of back projection in the direction from the left and from the right intersection of the equipotential line with the surface of said body, S is summed over all positions of the injecting electrodes, ##EQU33##are voltages measured on the left and on the right ends of the equipotential line that passes through the given point of the reconstructed cross section, and ##EQU34##are the reference potential differences corresponding to a body with homogeneous conductivity or determined according to claim 1d.