Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-08-29
2004-06-01
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S481000, C600S509000, C324S248000
Reexamination Certificate
active
06745063
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention is relevant to U.S. patent application Ser. No. 09/941,752 being filed by Daisuke Suzuki, Atsushi Ninomiya, Tsuyoshi Miyashita, Akihito Kandori, Keiji Tsukada and Kouich Yokosawa, and assigned to the present assignee, based on Japanese Patent Application No. 2000-334921 filed on Oct. 30, 2000, and is relevant to U.S. patent application Ser. No. 09/940,507 being filed by Kouichi Yokosawa, Daisuke Suzuki, Keiji Tsukada, Tsuyoshi Miyashita and Akihiko Kandori, and assigned to the present assignee, based on Japanese Patent Application No. 2001-044426 filed on Feb. 21, 2001. In particular, the biomagnetic field measuring apparatus of the invention was developed based on the Instrument For Measuring Magnetic Field as disclosed in JP Pat. App. No. 2000-334921, and the SQUID magneto-meters of the invention are based on the Detection Coil-Integrated Gradiometer And Magnetic Field Measuring Instrument as disclosed in JP Pat. App. No. 2001-044426, which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a biomagnetic field measuring method and apparatus for measuring a biomagnetic field generated by neural action in a brain, myocardial action in the heart of a living body by means of a plurality of fluxmeters including a high-sensitive superconducting quantum interference device (SQUID).
Heretofore, a measured result of a biomagnetic field is represented by a time changing waveform of measured magnetic field components or an iso-magnetic field map prepared by connecting points where the intensity of the magnetic field at arbitrary time is identical. For example, it is known that Z components (B
z
) in the orthogonal coordinates or equal-diameter components (B
r
) in the polar coordinates are measured and values of B
z
or B
r
are expressed as an iso-magnetic field map (H. Hosaka and D. Cohen, J. Electrocardiol., 9-4, 426 (1976)). Further, it is also known that tangential components (B
x
, B
y
) in the orthogonal coordinates are measured to be expressed as an iso-magnetic field map for each component or two-dimensional magnetic field vectors are calculated from {square root over ( )}{(B
x
)
2
, (B
y
)
2
} to be expressed as an iso-magnetic field map (K. Tsukada et al., Review of the Scientific Instruments, 66, 10 (1995)). In addition, a method is known in which normal components B
z
are measured and magnetic field components equivalent to tangential components (B
x
, B
y
) are analytically calculated from the normal components B
z
(T. Miyashita et al., Proceedings 20th International Conference IEEE/EMBS (Hong Kong), 520-523 (1998)).
Heretofore, the analytical result of the biomagnetic field components is represented by using a time waveform of a magnetic field and an iso-magnetic field map. Further, positions, intensities, directions and the like of current sources in a living body at arbitrary time are presumed by solving an inverse problem and these presumed data are used to presume a pre-excited location of arrhythmia in the heart, foci of epilepsy in the brain and the like. In order to trace dynamic phenomena in a certain time zone such as excitation conduction process of myocardium in the heart and neural excitation conduction in the brain, a lot of iso-magnetic field maps at individual time are displayed side by side or loci of vectors of current sources presumed at individual time are represented in a diagram (N. Izumida et al., Japanese Heart Journal, 731-742 (1998)).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide biomagnetic field measuring method and apparatus capable of quantifying conduction process of electro-physiological excitation without presumption of a dipole (magnetic field source) and display of many iso-magnetic field maps.
Without arranging many iso-magnetic field maps side by side to analyze dynamic excitation conduction in the heart and the brain by means of the pattern recognition, a graph or diagram representation for quantifying dynamic excitation conduction without using the pattern recognition is requested. A method of presuming current sources every moment can presume current sources as dipole models when the current sources are positioned locally, while generally the current sources are distributed widely with the spread in many time zones. When the inverse problem is solved every moment, many arithmetic operations are required until the solution is converged. Particularly, when the coincidence of a calculated distribution of magnetic fields prepared by presumed current sources and a distribution of actually measured magnetic fields is bad, presumed values of the current sources are deteriorated. Consequently, when the current sources are presumed every moment in a certain time zone, there is a problem that presumption error is increased to thereby produce an analytical result having interrupted continuity in change of time with respect to positions, intensities and directions of the current sources.
In the present invention, the orthogonal coordinates (x, y, z) (magnetic field components are B
x
, B
y
and B
y
) and the polar coordinates (r, &thgr;, &phgr;) are used as coordinates in measurement of a biomagnetic field. When an object to be measured is the heart, the orthogonal coordinates employing the chest as an xy plane is used. When an object to be measured is the brain, the polar coordinates (r, &thgr;, &phgr;) (magnetic field components are B
r
, B
&thgr;
and B
&phgr;
) is used since the head has a shape near to a sphere. The magnetic field components (normal components) vertical to the surface of the head are represented by B
z
and B
r
and components (tangential components) parallel to the plane tangential to the surface of the living body are represented by B
x
, B
y
, B
&thgr;
and B
&phgr;
.
The following description is made by using the orthogonal coordinates (x, y, z) by way of example, while when the polar coordinates (r, &thgr;, &phgr;) is used, B
z
, B
x
and B
y
are to be replaced by B
r
, B
&thgr;
and B
&phgr;
, respectively.
In the biomagnetic field measuring apparatus of the present invention, a set of sensor arrays is used to measure a biomagnetic field in various different directions. At this time, in order to analyze measured results of the biomagnetic field in many directions, (1) simultaneously with measurement of the biomagnetic field in respective directions, any of an electrocardiograph, a phonocardiograph, a polygraph, an electroencephalograph and the like is used as a living-body signal measuring apparatus to measure and collect living-body signals periodically generated except the biomagnetic field signals and including any of waveforms in electrocardiogram, heart sound, polygraph, electroencephalogram and the like as pairs with the biomagnetic field signals, or (2) synchronous signals synchronizing with the start of application of any stimulation signals generated by stimulating a nervous system by electrical stimulation of part of the living body by means of an electric stimulator, by stimulating auditory nerve by generation of sound by means of an auditory stimulator, by stimulating rhinencephalon by generation of smell by means of a smell stimulator, by stimulating visual area by generation of light signal or color signal by means of a visual stimulator, by stimulating tactile nerve by stimulation of skin by means of a touch stimulator or the like are collected as pairs with the biomagnetic field signals in respective directions.
A biomagnetic field (hereinafter referred to as cardiac magnetic field) generated from the heart is measured in two directions on the breast side and the back side or in four directions on the breast side, the back side, the right side and the left side of the chest or heart, for example. It is a matter of course that the biomagnetic field generated from the heart may be measured from different directions other than the above directions.
A biomagnetic field (hereinafter referred to cerebral magnetic field) generated from the head (brain) in
Kandori Akihiko
Miyashita Tsuyoshi
Suzuki Daisuke
Tsukada Keiji
Yokosawa Koichi
Fisher, Esq Stanley P.
Marquez, Esq Juan Carlos A.
Smith Ruth S.
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