Method of and device for determining internal body structure
First Claim
1. A method of determining the internal structure of a body comprising the steps of:
- exposing the body to an electric field which extends between individual electrodes of an electrode array which at least partially surrounds the body;
successively rotating the electric field through a plurality of different orientations with respect to the body;
measuring electric currents which flow between the individual electrodes for each of the different orientations of the electric field;
determining electrical resistance projections for individual tubes of current flux generated between the electrodes for each of the orientations of the electric field from the measurements of electrical current; and
determining the value of electrical resistance in individual elements of an imaginary matrix defined over the body by;
(a) assuming a specific distribution of resistance over the matrix elements;
(b) calculating an approximate distribution of field lines and equipotential lines within the body for each orientation of the field on the basis of the assumed distribution of resistance;
(c) calculating an approximate resistance in each tube of flux on the basis of the approximate distribution of the field lines and the assumed distribution of resistance;
(d) calculating a correction resistance distribution in each tube of flux by determination of the difference between the approximate resistance in that tube and the resistance projection determined from the measurement of the electric currents; and
(e) calculating a correction value for the specific resistance value for each element from the correction resistance distribution by interpolation.
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Abstract
Determining the internal structure of a body, for example, a human body, by means of an electric field which extends between individual electrodes of an electrode array which at least partly surrounds the body. Each time the value of the currents flowing through the individual electrodes is measured. From the currents electrical resistance values in individual tubes of flux generated between the electrodes are measured. By exposure of the body successively to electric fields which each have a different direction and by measurement of the resistance values then occurring, the specific resistance in individual elements of a matrix which is imagined to be stationary with respect to the body can be determined. From the given distribution of the specific resistance in the elements of the matrix, resistance values are calculated in all tubes of flux successively at least once for each field direction. For determination of a correction for the specific resistance in the elements of the matrix, the calculated resistance values are compared with the measured resistance values. The magnitude of the difference determines the magnitude of the correction.
71 Citations
15 Claims
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1. A method of determining the internal structure of a body comprising the steps of:
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exposing the body to an electric field which extends between individual electrodes of an electrode array which at least partially surrounds the body; successively rotating the electric field through a plurality of different orientations with respect to the body; measuring electric currents which flow between the individual electrodes for each of the different orientations of the electric field; determining electrical resistance projections for individual tubes of current flux generated between the electrodes for each of the orientations of the electric field from the measurements of electrical current; and determining the value of electrical resistance in individual elements of an imaginary matrix defined over the body by; (a) assuming a specific distribution of resistance over the matrix elements; (b) calculating an approximate distribution of field lines and equipotential lines within the body for each orientation of the field on the basis of the assumed distribution of resistance; (c) calculating an approximate resistance in each tube of flux on the basis of the approximate distribution of the field lines and the assumed distribution of resistance; (d) calculating a correction resistance distribution in each tube of flux by determination of the difference between the approximate resistance in that tube and the resistance projection determined from the measurement of the electric currents; and (e) calculating a correction value for the specific resistance value for each element from the correction resistance distribution by interpolation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for determining the internal structure of a body comprising:
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an electrode array comprising a plurality of individual electrodes disposed to at least partially surround the body; means for producing a potential difference between at least some of the electrodes to produce an electric field in the body; measuring means connected to at least some of the electrodes for measuring currents flowing through individual electrodes, the measuring system functioning to measure currents flowing through individual electrodes at different orientations of the electric field with respect to the body, the currents being a measure of the electrical resistance values in tubes of flux generated between electrodes of different potential; means for successively changing the orientation of the elelctric field with respect to the body; first storage means for storing orientation values which are a measure of the orientation of the successive electric fields with respect to the body and for storing projections of the measured resistance values which are derived from currents measured at an associated orientation of the field; second storage means for storing specific, assumed resistance values each of which is associated with one element of an imaginary matrix of elements defined over the body; third storage means for the storage of further data; and central processor means for; determining, for each orientation, electric field and equipotential lines which divide a space determined by the matrix into meshes from the assumed resistance value and the orientation values, and for storing values which are a measure of coordinates of the meshes in the third storage means; determining, by interpolation, an approximate mesh resistance in each mesh from the specific resistance values in the elements and the coordinates of each mesh and for storing the approximate mesh resistances in the third storage means; calculating a resistance value between two field lines by summation of mesh resistance values which are directly proportional to the approximate mesh resistance and to the length and inversely proportional to the width of the associated mesh; determining, from the difference between the measured resistance value and the calculated resistance value for each field direction, a correction resistance distribution for each mesh which is directly proportional to the difference and to the length of the mesh and which is inversely proportional to the width of the mesh, and for storing the correction resistance value in the third storage means; determining, by interpolation, from the stored correction resistance values a correction for the assumed resistance value in each elements; and
adding the correction to the associated assumed resistance value and storing sums thus obtained in the second storage means. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification