Apparatus for measuring bio-magnetic fields

• US 20020062076A1
• Filed: 10/16/2001
• Published: 05/23/2002
• Est. Priority Date: 10/19/2000
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kandori, Akihiko, Miyashita, Tsuyoshi, Tsukada, Keiji, Suzuki, Daisuke, Yokosawa, Koichi
• Granted Patent: US 6,681,131 B2
• Time in Patent Office: Days
• US Class Current: 600/409
• CPC Class Codes: A61B 5/243 specially adapted for magnetocardiographic [MCG] signals
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

An apparatus for measuring bio-magnetic fields includes a plurality of magnetometers for detecting magnetic fields generated from a live body; a driving circuit for driving the magnetometers; a computer for collecting output signals of the driving circuit in the form of data representing at least one waveform of the magnetic fields generated from the live body and for performing an arithmetic processing on the data representing the waveform of magnetic fields; a display unit; at least one signal processing circuit for processing output signals of the driving circuit; a signal generator for generating high-frequency AC current to be applied to the live animal body; and an electric wire for transmitting the high-frequency AC current from the signal generator to the live body via a plurality of electrodes to be attached to a plurality of points on the live body. The computer further performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction (generally perpendicular to the front surface of the live body) with respect to time which is the output signals of the signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields to be displayed on the display unit. The apparatus can also detect mechanical movement which occurs as blood flows in organs and organs move.

Claims

1. An apparatus for measuring bio-magnetic fields comprising:

a plurality of magnetometers for detecting magnetic fields generated from a live body;

a driving circuit for driving said magnetometers;

a computer for collecting output signals of said driving circuit in the form of data representing at least one waveform of magnetic fields generated from said live body and for performing an arithmetic processing on said data representing the waveform of magnetic fields;

a display unit;

a first and a second signal processing circuits for processing output signals of said driving circuit;

a signal generator for generating high-frequency AC current to be applied to said live body; and

an electric wire for transmitting said high-frequency AC current from said signal generator to said live body via a plurality of electrodes to be attached to a plurality of points on said live body;

wherein said first signal processing circuit has a first band-pass filter for passing a first predetermined bandwidth portion of the output signals of said driving circuit, a filter for removing at least one predetermined frequency portion from output signals of said first band-pass filter, and a first amplifier for amplifying output signals of said filter,

said second signal processing circuit has a high-pass filter for passing a high bandwidth of the output signals of said driving circuit, a phase-shift detector for demodulating a portion with a frequency of said signal generator from output signals of said high-pass filter, a second band-pass filter for passing a second predetermined bandwidth portion of output signals of said phase-shift detector, and a second amplifier for amplifying output signals of said second band-pass filter, and

said display unit displaying at least one of the output signal of said first signal processing circuit and the output signal of said second signal processing circuit.

2. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein said display unit displays the output signals of said second signal processing circuit in correspondence with positions where said SQUID magnetometers are arranged.

3. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein said electrodes are attached to the head and both ankles of the live animal body.

4. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an averaging process on the output signals of said second signal processing circuit, which include a plurality of repetitive waveforms, by adding the repetitive waveforms then dividing results of the adding step by the number of the repetitive waveforms during a time period, a starting time and an ending time of the time period are determined based on trigger signals extracted from electrocardiograph measured during the same time period or based upon trigger signals extracted from the output signals of the first signal processing circuit measured during the same time period.

5. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of partial differentiation on the magnetic fields B_z in a z direction which is generally perpendicular to a x, y plane wherein the x, y plane is a front surface of the live body above which the magnetometers are arranged,

the computer also performs an arithmetic processing for forming from the resulted partial differentials ∂

B_z/∂

x and ∂

B_z/∂

y a contour map by connecting points of each equal {square root}{∂

B_z/∂

x)²+(∂

B_z/∂

y)²} magnitude value respectively at a predetermined time,

the computer selectively performs an arithmetic processing for forming an arrow map representing current arrows having I_x={∂

B_z/∂

x} as an x component and I_y=−

{∂

B_z/∂

y} as a y component at the predetermined time by connecting points with each equal I_xy={square root}(I_x²+I_y²) magnitude value, and

said contour map and said arrow map are selectively displayed on said display unit.

6. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time so as to generate at least one first-order differential waveform of the magnetic fields to be displayed on said display unit,

the waveform of the magnetic fields is outputted from said second signal processing circuit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

7. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time which is outputted from said second signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields to be displayed in a overlapping manner on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

8. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time which is outputted from said second signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields,

the computer also performs an arithmetic processing for forming a map by connecting points which have equal magnitude of said first-order differential waveform of the magnetic fields at a predetermined time so as to display said map on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

9. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the magnetic fields B_z in a z direction with respect to time which is outputted from said second signal processing circuit so as to generate at least one first-order differential waveform B_z′

of the magnetic fields,

the computer performs an arithmetic processing of partial differentiation on said first-order differential waveform B_z′

of the magnetic fields with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y of the magnetic fields,

the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer selectively performs an arithmetic processing for forming an arrow map representing current arrows having I_x={∂

B_z/∂

x} as an x component and I_y=−

{∂

B_z′

/∂

y} as a y component at the predetermined time by connecting points with each equal I_xy={square root}(I_x²+I_y²) magnitude value,

said contour map and said arrow map are selectively displayed on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

10. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of partial differentiation on the waveform of the magnetic fields B_z in a z direction with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y of the magnetic fields,

the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer performs an arithmetic processing for estimating at least one current dipole to be displayed on said display unit by using said contour map,

the waveform of the magnetic fields B_z are outputted from said second signal processing circuit, and

the z direction is generally perpendicular to a x,y plane and the x,y plane is a front surface of the live body above which the magnetometers are arranged.

11. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields B_z in a z direction with respect to time which is obtained as the output signals of said second signal processing circuit so as to generate at least one first-order differential waveform B_z′

of the magnetic fields,

the computer performs an arithmetic processing of partial differentiation on the waveform of the magnetic fields B_z in a z direction with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y of the magnetic fields, the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer performs an arithmetic processing for estimating at least one current dipole to be displayed on said display unit by using said contour map, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

12. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of partial differentiation on the waveform of the magnetic fields B_z in a z direction with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y of the magnetic fields,

the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer performs an arithmetic processing for estimating the distribution of conductivity in the live animal body to be displayed on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

13. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time which is outputted from said second signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields,

the computer performs an arithmetic processing of partial differentiation on the waveform of the magnetic fields B_z in a z direction with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y of the magnetic fields,

the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer performs an arithmetic processing for estimating the distribution of conductivity in the live animal body to be displayed on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

15. The apparatus for measuring bio-magnetic fields as defined in claim 14, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time so as to generate at least one first-order differential waveform of the magnetic fields to be displayed on said display unit,

the waveform of the magnetic fields is outputted from said signal processing circuit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

16. The apparatus for measuring bio-magnetic fields as defined in claim 14, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time which is outputted from said signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields to be displayed in a overlapping manner on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

17. The apparatus for measuring bio-magnetic fields as defined in claim 14, wherein the computer performs an arithmetic processing of first-order differentiation on the waveform of the magnetic fields in a z direction with respect to time which is outputted from said signal processing circuit so as to generate at least one first-order differential waveform of the magnetic fields,

the computer also performs an arithmetic processing for forming a map by connecting points which has equal magnitude of said first-order differential waveform of the magnetic fields at a predetermined time so as to display said map on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

18. The apparatus for measuring bio-magnetic fields as defined in claim 14, wherein the computer performs an arithmetic processing of first-order differentiation on the magnetic fields B_z in a z direction with respect to time which is outputted from said signal processing circuit so as to generate at least one first-order differential waveform B_z′

of the magnetic fields,

the computer performs an arithmetic processing of partial differentiation on said first-order differential waveform B_z′

of the magnetic fields with respect to an x variable in an x direction and a y variable in a y direction so as to generate at least one pair of partial differentials OB_z′

/∂

x and OB_z′

/y of the magnetic fields,

the computer performs an arithmetic processing for forming from said partial differentials ∂

B_z′

/∂

x and ∂

B_z′

/∂

y a contour map by connecting points with an equal {square root}{(∂

B_z′

/∂

x)²+(∂

B_z′

/∂

y)²} value at a predetermined time,

the computer selectively performs an arithmetic processing for forming an arrow map representing current arrows having I_x={∂

B_z/∂

x} as an x component and I_y=−

{∂

B_z/∂

y} as a y component at the predetermined time by connecting points with each equal I_xy={square root}(I_x²+I_y²) magnitude value,

said contour map and said arrow map are selectively displayed on said display unit, and

the z direction is generally perpendicular to a x, y plane and the x, y plane is a front surface of the live body above which the magnetometers are arranged.

19. The apparatus for measuring bio-magnetic fields as defined in claim 1, wherein the signal generator includes an oscillator.

20. The apparatus for measuring bio-magnetic fields as defined in claim 14, wherein the signal generator includes an oscillator.

14. An apparatus for measuring bio-magnetic fields comprising:

a plurality of magnetometers for detecting magnetic fields generated from a live animal body;

a driving circuit for driving said magnetometers;

a computer for collecting output signals of said driving circuit in the form of data representing at least one waveform of magnetic fields generated from said live animal body and for performing an arithmetic processing on said data representing the waveform of magnetic fields;

a display unit;

a signal processing circuit for processing output signals of said driving circuit;

a signal generator for generating high-frequency AC current to be applied to said live animal body; and

an electric wire for transmitting said high-frequency AC current from said signal generator to said live animal body via a plurality of electrodes to be attached to a plurality of points on said live animal body;

wherein said signal processing circuit has a high-pass filter for passing a high bandwidth of the output signals of said driving circuit, a phase-shift detector for demodulating a portion with a frequency of said signal generator from output signals of said high-pass filter, a band-pass filter for passing a predetermined bandwidth portion of output signals of said phase-shift detector, and an amplifier for amplifying output signals of said second band-pass filter, and

said display unit displaying the output signal from said signal processing circuit.