Method and apparatus for non-invasive identification of the endocorporeal spatial distribution of the electrical impedance in a subject
First Claim
1. An apparatus for identifying the endocorporeal spatial distribution of the electrical impedance in an examination region of a subject, comprising:
- an electric current source which generates a feed current;
two feed electrodes respectively connected to said current source by electrical connecting lines which carry said feed current, said connecting lines having a first magnetic field associated therewith due to said feed current carried therein, said feed electrodes being attachable to a subject and forming means for impressing said feed current into an examination region of said subject and causing a distribution of current in said examination region dependent on the electrical impedance distribution in said examination region and the position of said feed electrodes, said distribution of current causing a second magnetic field;
a compensation conductor Iccp connected to said current source;
said current source including means for supplying a compensation current to said compensation conductor Iccp having a direction opposite to said feed current for compensating said first magnetic field;
magnetic field measuring means for obtaining a spatial distribution of a characteristic quantity of said second magnetic field at a plurality of points outside said examination region;
evaluation means, supplied with said spatial distribution of a characteristic quantity, for reconstructing, from said spatial distribution of a characteristic quantity, an equivalent current density distribution in said examination region which would generate a theoretical magnetic field most closely coinciding with said second magnetic field, said evaluation means including means for identifying the spatial distribution of impedance in said examination region from said equivalent current density distribution; and
display means connected to said evaluation means for visually portraying said spatial distribution of impedance.
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Abstract
In a method and apparatus for identifying the spatial distribution of electrical impedance within an examination subject, a source of electrical current is electrically connected to at least two feed electrodes which impress a feed current from the source in an examination region of a subject. The resulting magnetic field is measured at points outside the examination region, and an equivalent current density distribution is reconstructed within the examination region from the measured values of the magnetic field by an evaluation unit. A compensation conductor is connected to the current source. The current source delivers a compensation current, which flows in a direction opposite to the feed current, through the compensation conductor loop, so that the magnetic field generated by the feed current in the connecting lines is compensated. The evaluation unit identifies the spatial distribution of the impedance from the equivalent current density distribution. The spatial distribution of the impedance can be portrayed on a display.
26 Citations
21 Claims
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1. An apparatus for identifying the endocorporeal spatial distribution of the electrical impedance in an examination region of a subject, comprising:
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an electric current source which generates a feed current; two feed electrodes respectively connected to said current source by electrical connecting lines which carry said feed current, said connecting lines having a first magnetic field associated therewith due to said feed current carried therein, said feed electrodes being attachable to a subject and forming means for impressing said feed current into an examination region of said subject and causing a distribution of current in said examination region dependent on the electrical impedance distribution in said examination region and the position of said feed electrodes, said distribution of current causing a second magnetic field; a compensation conductor Iccp connected to said current source; said current source including means for supplying a compensation current to said compensation conductor Iccp having a direction opposite to said feed current for compensating said first magnetic field; magnetic field measuring means for obtaining a spatial distribution of a characteristic quantity of said second magnetic field at a plurality of points outside said examination region; evaluation means, supplied with said spatial distribution of a characteristic quantity, for reconstructing, from said spatial distribution of a characteristic quantity, an equivalent current density distribution in said examination region which would generate a theoretical magnetic field most closely coinciding with said second magnetic field, said evaluation means including means for identifying the spatial distribution of impedance in said examination region from said equivalent current density distribution; and display means connected to said evaluation means for visually portraying said spatial distribution of impedance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for identifying the endocorporeal spatial distribution of the electrical impedance in an examination region of a subject, comprising the steps of:
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generating a feed current carried by electrical connecting lines, said connecting lines having a first magnetic field associated therewith due to said feed current carried therein; attaching feed electrodes, connected to said connecting lines, to a subject and impressing said feed current into an examination region of said subject and causing a distribution of current in said examination region dependent on the electrical impedance distribution in said examination region and the position of said feed electrodes, said distribution of current causing a second magnetic field; supplying a compensation current to a compensation conductor loop in a direction opposite to said feed current for compensating said first magnetic field; obtaining a spatial distribution of a characteristic quantity of said second magnetic field at a plurality of points outside said examination region; reconstructing, from said spatial distribution of a characteristic quantity, an equivalent current density distribution in said examination region which would generate a theoretical magnetic field most closely coinciding with said second magnetic field; identifying the spatial distribution of impedance in said examination region from said equivalent current density distribution; and visually portraying said spatial distribution of impedance. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification