Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-02-19
2002-07-23
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S425000, C600S523000, C600S524000, C600S440000, C600S509000, C323S909000
Reexamination Certificate
active
06424853
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field measurement apparatus consisting of a magnetometer comprised of a Superconductive Quantum Interferometer Device (SQUID) for measuring magnetic fields generated by the nervous activity of the brain of humans or animals or myocardial activity or magnetic substances contained in the subject to be inspected.
2. Description of Related Art
In measurements of very weak magnetic fields in the conventional art using equipment such as SQUID for measuring biomagnetic fields, generally the magnetic field on the surface of a living body is capable of being measured. Such measurements can be just the vertical components of a magnetic field with the head regarded as a sphere, for instance the polar coordinates (r, &phgr;, &thgr;) in the case of the head, and the magnetic field component B
r
in the vertical r direction on the head surface, or in the case of the heart, the orthogonal coordinates (X, Y, Z), of the chest section when measured on the flat planes X and Y, and the magnetic field component B
Z
in the vertical Z direction on the X and Y planes.
On the other hand while few in number, there is literature reporting on measurement apparatus for measuring magnetic components of a biomagnetic field in a plurality of directions. For instance, the simultaneous measurement of the magnetic component B
X
in the X direction and the magnetic component B
Y
in the Y direction on the orthogonal coordinates (X, Y, Z); as well as the display of magnitude {square root over ( )}(B
X
2
+B
Y
2
) synthesized by magnetic component B
X
in the X direction and magnetic component B
Y
in the Y direction have been reported (K. Tsukada et. al., Rev. Sci. Instrum., 66 (10), pp 5085-5091 (1995)).
Further, though not the three directions B
r
, B
&phgr;
, B
&thgr;
of the polar coordinates (r, &phgr;, &thgr;) of the magnetic components B
X
, B
Y
and B
Z
in the three directions of the orthogonal coordinates (X, Y, Z); a method has been reported for measuring the three components of each intersecting magnetic field, finding the magnetic components B
r
, B
&phgr;
, B
&thgr;
in the three directions on the polar coordinates (r, &phgr;, &thgr;) and displaying a waveform showing the time variation of each magnetic component in three directions on polar coordinates (r, &phgr;, &thgr;) on a CRT screen (Y. Yoshida et. al., 10th Int'l Conf. on Biomagnetisim (1996)).
Also, in the conventional art, not only a waveform showing time variations in a magnetic field strength, but also the distribution of the magnitude of a magnetic field can be found from results of magnetic measurements of a plurality of points in an organism utilizing a plurality of magnetometers, and the result displayed as a magnetic field magnitude contour map. Factors such as the position, magnitude and direction of electrical current sources in an organism can be analyzed over desired periods of time on a magnetic field contour map and changes over time in the electrical physiological phenomenon in the organism thus discovered. In the conventional art, changes in electrical physiological phenomena in a dynamic organism can therefore be revealed by utilizing these magnetic field contour maps to aid in the diagnosis of disease.
In the method used in the conventional art, the heart of the child or adult which is the subject of measurement is fixed in a constant position and direction versus the magnetic plane of the magnetic field of the magnetometer. However, there is the problem that when measuring the magnetic field of the heart of a fetus, an accurate measurement of the heart's magnetic field cannot be made since the position and direction of the fetus cannot be fixed since the fetus is constantly moving within the body of the mother. In other words, even if there is no change in the electrical current source within the heart of the fetus, the position and direction will change versus the magnetic plane of the magnetic field generated in the magnetometer by the heart of the fetus, creating the problem that the time waveform and the components of the magnetic field being measured cannot be fixed. Another problem in the conventional art, is that a standardized waveform cannot be obtained due to variations in the magnetic field waveform due to changes in the body position of the fetus within the body of the mother, making an accurate diagnosis of the heart disease of the fetus difficult. Further, when the position of the Dewar's vessel housing the magnetometer is moved in order to increase the magnetic signal to measure the component in just one direction of the magnetic field, the magnetic signal reaches a maximum and the measurement range narrows so that setting an ideal position and direction for measurement with the Dewar's vessel is difficult, creating the problem that a long time is required. A still further problem is that a large drift occurs in the magnetic signal being detected when moving the Dewar's vessel to an optimal position versus the subject being measured and a long time is thus required to stabilize the magnetic signal being detected.
Yet another problem is that high sensitivity non-destructive inspection of minute impurities having magnetic properties within a nonmagnetic substance is difficult, and furthermore the investigation cannot be conducted with high speed.
SUMMARY OF THE INVENTION
In order to resolve the above mentioned problems, it is therefore an object of this invention to provide a magnetic field measurement apparatus and a magnetic field measurement method for accurately measuring the electrical physiological phenomena within the heart of a fetus without affecting a change in the status of the fetus, even when the direction and position of the fetus changes within the body of the mother. It is a further object of the invention to provide a magnetic field measurement apparatus and a magnetic field measurement method for accurately detecting changes over time in the magnetic field from the subject of inspection, even in cases where a position change has occurred in the subject for inspection while placed in an environment for inspection or the subject for inspection is placed inside a special material for inspection.
The magnetic field measurement apparatus of this invention is comprised of detection coils for detecting magnetic fields of three directions and a superconductive quantum interferometer device (SQUID) connected to these detection coils; a single or a plurality of vector magnetometers are provided for isolating and measuring each of the magnetic components for the three directions. The magnetic components of the intersecting three directions measured with the single or plurality of vector magnetometers are synthesized by the square sum method and a time waveform of the resulting magnitude of the magnetic field is shown on a display means (monitor).
In the magnetic field measurement apparatus of this invention, a holding means and control means for storing and cooling the vector magnetometers, maintaining the vector magnetometers in a superconductive state in the Dewar's vessel and varying the direction of the center position of the bottom of the Dewar's vessel towards the subject for inspection is provided. The center position of the bottom of the Dewar's vessel is set to an ideal position and direction versus the subject for inspection so that the magnitude of the time waveform reaches a maximum, while observing the time waveform on the monitor. When shifting the bottom of the Dewar's vessel for optimum direction and position while watching the monitor, and the frequency band width of the magnetic field being measured is widened, time is required for the signal drift to significantly stabilize so that in order to remove the drift of the output waveform when moving the Dewar's vessel, the signal from each magnetometer is split into two signals. One of these signals is fed to a highpass filter, the signal then processed and displayed on the monitor. The o
Kandori Akihiko
Miyashita Tsuyoshi
Sasabuchi Hitoshi
Tsukada Keiji
Hitachi , Ltd.
Lateef Marvin M.
Lin Jeoyuh
Mattingly Stanger & Malur, P.C.
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