Method and apparatus for determining biocurrent distribution within subject
First Claim
1. A method for determining biocurrent distribution within a subject, comprising the steps of:
- measuring potentials at a plurality of points on a surface of said subject;
deriving physical properties of said subject in positions of a 3-D network of predetermined cells in said subject;
determining admittances of lines defining external shapes of said cells on the basis of said physical properties;
calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the admittances of said lines and biocurrent distribution within said subject and wherein at least one current source is connected in parallel with said lines;
changing position and current magnitude of each of said at least one current source while comparing said calculated potentials with said measured potentials, and determining the positions and current magnitudes of the at least one current source on the basis of said comparing anddetermining said biocurrent distribution from said positions and current magnitudes of the at least one current source.
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Accused Products
Abstract
A living body is replaced by a 3-D network. Admittance connected to lines forming the 3-D network is calculated. Position rt and magnitude qt=(jtx,jty,jtz) of a current dipole are assumed, and current sources jtx, jty and jtz are connected in parallel with lines coupled to a node. Node equations are formulated, and an admittance matrix Y is derived. An inverse matrix Y'"'"' of Y is calculated, and body surface potential generated by the current sources is calculated by using the inverse matrix Y'"'"'. Then, rt and qt minimizing cost function which is sum total of squares of differences between measured values of body surface potential and the above described calculated values for all measuring points are derived. Thereby potential distribution on the body surface can be calculated with due regard to the shape of the living body and conductivity distribution in the living body on the basis of the assumed current dipole. On the basis of measured data of potential distribution on the body surface, therefore, the position and magnitude of the current dipole can be estimated with high precision.
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Citations
22 Claims
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1. A method for determining biocurrent distribution within a subject, comprising the steps of:
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measuring potentials at a plurality of points on a surface of said subject; deriving physical properties of said subject in positions of a 3-D network of predetermined cells in said subject; determining admittances of lines defining external shapes of said cells on the basis of said physical properties; calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the admittances of said lines and biocurrent distribution within said subject and wherein at least one current source is connected in parallel with said lines; changing position and current magnitude of each of said at least one current source while comparing said calculated potentials with said measured potentials, and determining the positions and current magnitudes of the at least one current source on the basis of said comparing and determining said biocurrent distribution from said positions and current magnitudes of the at least one current source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for determining biocurrent distribution within a subject, comprising the steps of:
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measuring potentials at a plurality of points on a surface of said subject; measuring magnetic fields at said points; deriving physical properties of said subject in positions of a 3-D network of predetermined cells in said subject; determining admittances of lines defining external shapes of said cells on the basis of said physical property; calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the admittances of said lines and biocurrent distribution within said subject and wherein at least one current source is connected in parallel with said lines; calculating magnetic fields at said measuring points on the basis of said biocurrent distribution; and determining current vectors and positions thereof and minimizing the sum of the product obtained by multiplying a sum total of integer-th power values of absolute values of differences between said calculated potentials and said measured potentials for all of said measuring points by a first predetermined coefficient and the product obtained by multiplying the sum total of integer-th power values of absolute values of differences between said calculated magnetic fields and said measured magnetic fields for all of said measuring points by a second predetermined coefficient.
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17. A method for determining biocurrent distribution within a subject, comprising the steps of:
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measuring potentials at a plurality of points on a surface of said subject; deriving physical properties of said subject in positions of a 3-D network of predetermined cells in said subject; determining impedances of lines defining external shapes of said cells on the basis of said physical properties; calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the impedances of said lines biocurrent distribution within said subject and wherein at least one current source is connected in parallel with said lines; changing position and voltage magnitude of each of said at least one voltage source while comparing said calculated potentials with said measured potentials, and determining the positions and voltage magnitudes of the at least one voltage source on the basis of said comparing; and determining said biocurrent distribution from said positions and current magnitudes of the at least one voltage source and said impedances. - View Dependent Claims (18)
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19. An apparatus for determining biocurrent distribution within a subject, comprising:
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means for measuring potentials at a plurality of points on a surface of said subject; means for deriving physical properties of said subject in positions of predetermined cells in said subject, said cells forming a 3-D arrangement; means for determining admittances of lines defining an external shape of each of said cells on the basis of said physical properties; means for setting at least one current source connected in parallel with said lines on the basis of biocurrent distribution in said subject; means for calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the admittances of said lines and said current sources connected in parallel with said lines; means for changing positions and current magnitudes of said at least one current source while comparing said calculated potentials with said measured potentials, and determining the positions and current magnitudes of the at least one current source on the basis of said comparing; and means for determining said biocurrent distribution from said positions and current magnitudes of the at least one current source. - View Dependent Claims (20)
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21. An apparatus for determining biocurrent distribution within a subject, comprising:
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means for measuring potentials at a plurality of points on a surface of said subject; means for measuring magnetic fields at said points; means for deriving physical properties of said subject in positions of predetermined cells in said subject, said cells forming a 3-D arrangement; means for determining admittances of lines defining an external shape of each of said cells on the basis of said physical properties; means for setting at least one current source connected in parallel with said lines on the basis of biocurrent distribution in said subject; means for calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the admittances of said lines and said at least one current source connected in parallel with said lines; means for calculating magnetic fields at said measuring points on the basis of said biocurrent distribution; and means for determining positions and magnitudes of said at least one current source and minimizing the sum of the product obtained by multiplying a sum total of integer-th power values of absolute values of differences between said calculated potentials and said measured potentials for all of said measuring points by a first predetermined coefficient and the product obtained by multiplying the sum total of integer-th power values of absolute values of differences between said calculated magnetic fields and said measured magnetic fields for all of said measuring points by a second predetermined coefficient.
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22. An apparatus for determining biocurrent distribution within a subject, comprising:
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means for measuring potentials at a plurality of points on a surface of said subject; means for deriving physical properties of said subject in positions of predetermined cells in said subject, said cells forming a 3-D arrangement; means for determining impedances of lines defining an external shape of each of said cells on the basis of said physical properties; means for setting at least one voltage source connected in series to said lines on the basis of biocurrent distribution in said subject; means for calculating potentials of nodes of positions corresponding to at least said measuring points in a 3-D network formed by said lines, on the basis of the impedances of said lines and said voltage sources connected in series to said lines; means for changing positions and voltage magnitudes of said at least one voltage source while comparing said calculated potentials with said measured potentials, and determining the positions and voltage magnitudes of the at least one voltage source on the basis of a result of comparison; and means for determining said biocurrent distribution on the basis of determined voltage sources and said impedances.
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Specification