JPH05317279A - Biomagnetism measuring instrument - Google Patents

Abstract

PURPOSE:To simplify a three-dimensional inverse problem to a two-dimensional inverse problem or one-dimensional inverse problem by enclosing the magnetic field sensor of the superconducting quantum interferometer with one piece or plural pieces of superconductors and selectively detecting and measuring only the magnetic fields generated from the currents existing within the arbitrary sectional part having a certain thickness in a living body. CONSTITUTION:The magnetic field sensor 3 of the superconducting quantum interferometer (SQUID) is enclosed with one piece or plural pieces of the superconducting plates 2, 2 and only the currents j existing within the arbitrary sectional part having a certain thickness or within the arbitrary columnar part having a certain sectional area or the magnetic fields (m) generated from a magnetic flux source in the living body 7 are selectively detected and measured. A region 8 to be detected and measured is nearly equalled to the section cut off by two sheets of the superconducting plates 2, 2 within a limited range by adequately selecting the spacing between two sheets of the superconducting plates 2 and 2 and the position and size of the magnetic sensor 3 of the SQUID at this time. As a result, the biomagnetic information effective for the medical and clinical observation and diagnosis of the local part of the lesion is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biomagnetism measuring device. When the brain is activated, an electric current based on the stimulation of the nerve tissue of the brain flows inside the brain. Therefore, if we can know what kind of current is distributed and flowing inside the brain,
You can grasp the activity status of the brain. From a clinical point of view, this makes it possible to identify functional defects and locations of the brain, which is very useful information for the surgical treatment. In addition, with the movement of the heart muscle, an electric current flows through the nerve in the heart muscle. Therefore, if it is possible to know what kind of current is distributed and flowing in the heart, the activity status of the heart can be grasped. From the medical and clinical point of view, this makes it possible to identify the functional defect and location of the heart, which is extremely useful information for its surgical treatment.

On the other hand, when a current flows, a magnetic field is always generated. Therefore, the research and development of so-called biomagnetic measurement technology, which measures the magnetic field leaking outside the human body and tries to know the current distribution flowing in the brain and heart of the human body from the information on the contrary, is energetically pursued in many countries around the world. In Japan, research and development is being carried out in one of the development projects of the Ministry of International Trade and Industry.

[0003]

2. Description of the Related Art Conventionally, a superconducting quantum interferometer (SQUID, hereinafter referred to as a "skid") has been used as a magnetic field sensor for measuring a biomagnetic field, and the current development task is to increase the number of channels (Fig. 1). Also, from the output signal of the channel skid, the inside of the living body (brain, heart, etc.)
The development of a calculation method for obtaining the distribution of current flowing in is also an important issue. If these two problems are solved, so-called SQUID-CT can be realized.

However, the calculation for obtaining the distribution of the output signal of the multi-channel skid, that is, the distribution of the electric current flowing inside the living body (brain, heart, etc.) from the distribution of the magnetic field outside the living body is not inherently uniquely determined. A typical example of the inverse problem, solving this problem is the most difficult research problem. That is, in the conventional biomagnetic measurement, there is a three-dimensional inverse problem in which the current flowing in a three-dimensional distribution in the living body is obtained from the measurement result of the magnetic field outside the living body, and it is very difficult to solve the problem. However, no effective method has been developed yet.

[0005]

The object of the present invention is to simplify such a three-dimensional inverse problem into a two-dimensional inverse problem or a one-dimensional inverse problem, and to perform local observation and diagnosis of lesions in clinical medicine. An object of the present invention is to provide a biomagnetism measuring device capable of obtaining effective biomagnetic information.

[0006]

The inventor of the present invention, as a result of earnest research for achieving this object, has a superconducting parallel plate, or a superconducting cylinder and a magnetic sensor (skid), which exist in an arbitrary cross section or in an arbitrary direction of the living body. The present invention has been devised to selectively detect a magnetic field from a magnetic flux source (current dipole, magnetic dipole), and the present invention has been invented based on this finding.

In the biomagnetism measuring device of the present invention,
The skid magnetic field sensor is surrounded by one or more superconductors to selectively select only the magnetic field generated from the electric current existing in an arbitrary cross section having a certain thickness inside the living body or an arbitrary column having a certain cross sectional area. There is a device in which the skid is surrounded by a superconducting parallel plate (Fig. 2) and a device in which the skid is surrounded by a superconducting cylinder whose cross section is electrically open (Fig. 3). In addition, the superconductor may have a shape as shown in FIG.

Now, when the current dipole S is at the front a of the superconducting plate, the magnetic field B at the position y is

[Equation 1] Here, S is a magnetic flux source and S'is a mirror image thereof. S =-
S ', so

[Equation 2] Becomes The second term on the right side is a component due to a mirror image, and the magnetic field becomes weaker by this amount.

In front of the superconducting plate, as shown by the equation,
It is possible to measure the combined magnetic field of the magnetic flux source S and its mirror image S ′. However, the magnetic field is 0 behind the superconducting plate. In other words, the magnetic field generated by the magnetic flux source S cannot be measured behind the superconducting plate. This is consistent with the case of a light source and a mirror of infinite size. That is, the light source and its mirror image can be seen in front of the mirror, but not behind the mirror.

In FIG. 5, it is possible to divide into a limited area A, B and C which includes a magnetic flux source and a superconducting plate within a circle.
That is, A is a region where the magnetic field of the magnetic flux source can be directly measured, B is a region where the magnetic field of the magnetic flux source can be measured while being influenced by the mirror image, and C is a region where the magnetic field of the magnetic flux source cannot be measured. Therefore, when many magnetic flux sources are distributed in the space, it is possible to realize a measurement system that selectively detects only the magnetic flux sources in a limited area by using the superconductor.

[0011]

EXAMPLES The present invention will be specifically described with reference to Examples.
However, the present invention is not limited to these examples. Example 1 Detection of Magnetic Flux Source in Living Body by Superconducting Parallel Plate / Magnetic Field Sensor In FIG. 5, when S is a magnetic sensor, the magnetic flux source existing in the area A is detected by the magnetic sensor without being much influenced by the superconducting plate. It The magnetic flux source existing in the region B is detected while being influenced by the superconducting plate. The magnetic flux source existing in the area C is not detected. Therefore, as shown in FIG.
When a magnetic detection system is constructed by sandwiching a magnetic sensor between two superconducting parallel plates, the magnetic flux source space that can be detected by this system is limited to the narrow region shown in the figure.

On the other hand, the magnetic flux that can easily enter between the superconducting parallel flat plates is the magnetic flux flowing in parallel to the flat plates. Therefore,
When the magnetic flux source is a current dipole, the direction of the current dipole that allows the flow of magnetic flux to infiltrate between the superconducting parallel plates with sufficient strength is obtained. As shown in FIG. It can be seen that the current dipole is perpendicular to. Similarly, when the magnetic flux source is a magnetic dipole, it can be seen that the magnetic dipole is parallel to the flat plate surface as shown in FIG. 7B.

From the above, it is possible to construct a magnetic flux source detection and measurement system in a living body by a superconducting parallel plate / magnetic field sensor as shown in FIG. By appropriately selecting the distance between the two superconducting parallel plates and the position and size of the magnetic sensor (skid), the space to be detected and measured is within a limited range and the cross section cut by the two superconducting parallel plates is almost the same. Can be equal.

Example 2 Detection of Magnetic Flux Source in Living Body by Superconducting Cylinder / Magnetic Field Sensor In FIG. 9, the cross section of the superconducting cylinder is an electrically open loop, and the magnetic flux parallel to the cylinder axis is inside the superconducting cylinder. Only can penetrate. In addition, the magnetic flux source region that can be detected by the superconducting cylinder / magnetic field sensor corresponds to the thick cross section of the living body in the case of the superconducting parallel plate / magnetic field sensor, and has a body axis (round bar shape) with an area cut by the inner surface of the superconducting cylinder. )
Becomes Therefore, the only magnetic flux source that can be detected with good sensitivity by the superconducting cylinder / magnetic field sensor is the magnetic dipole parallel to the cylinder axis existing in the detection region.

[0015]

According to the present invention, a three-dimensional problem can be simplified into a two-dimensional or one-dimensional problem and an inverse problem can be easily handled. Further, since only the magnetic signal from the local part of the living body can be selectively detected and measured, it is effective for the observation and diagnosis of the local site of the lesion in the medical clinic.

[Brief description of drawings]

FIG. 1 is a brain magnetic field measurement (SQUA) showing an example of biomagnetic field measurement.
It is a schematic explanatory drawing of (ID-CT). Then, the main points are as follows.

[Table 1]

FIG. 2 is an explanatory diagram of biomagnetic field measurement by a superconducting parallel plate / magnetic field sensor.

FIG. 3 is an explanatory diagram of biomagnetic field measurement by a superconducting cylinder / magnetic field sensor.

FIG. 4 is an example of a superconductor surrounding a SQUID. (A)
Is a non-parallel two superconducting flat plate, (b) is a superconducting parallel plate with both ends turned up, (c) is a rectangular superconducting tube whose cross section is electrically open, and (d) is a cross section. Superconducting cylinder narrowed in the direction of the electrically opened tip, (e) Superconducting cylinder whose cross section is electrically opened and part of the tip is narrowed, (f) Part of the tip is narrow in two parallel plates It is a superconducting flat plate.

FIG. 5 is a diagram showing three spatial regions divided by a finite-sized superconducting plate and a magnetic flux source.

FIG. 6 is a diagram showing a magnetic flux source region detectable by a superconducting parallel plate / magnetic field sensor system.

FIG. 7 is a diagram showing directions of (a) current dipole and (b) magnetic dipole detected and measured by a superconducting parallel plate / magnetic field sensor system.

[Explanation of symbols]

 1 multi-channel SQUID, 2 superconducting plate, 3 magnetic field sensor (SQUID), 4 sensor cooling head, 5 vacuum, 6 liquid helium, 7 living body, 8 measurement target area, 9 measurement non-target area, 10 superconducting cylinder, 11 magnetic field sensor ( SQUID), 12 electrical insulation part, 13 living body, 14 magnetic dipole, 15 measurement target region, 16 measurement non-target region, 17 superconducting plate, 18 magnetic field sensor, 19 detectable magnetic flux source region, 20 superconducting plate, 21 magnetic field sensor, 22 current dipole, 23 magnetic field dipole, 24 detectable flux source area.

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[Procedure amendment]

[Submission date] June 4, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

FIG. 1 is a brain magnetic field measurement (SQUA) showing an example of biomagnetic field measurement.
It is a schematic explanatory drawing of (ID-CT).

Claims (3)

[Claims] 1. A skid (SQUID, superconducting quantum interferometer) magnetic field sensor is surrounded by one or a plurality of superconductors, and inside a living body inside an arbitrary cross-section having a certain thickness or within an arbitrary pillar having a certain cross-sectional area. A biomagnetism measuring device characterized by selectively detecting and measuring only a magnetic field generated from an existing current or magnetic flux source. 2. The biomagnetism measuring device according to claim 1, wherein the superconductor according to claim 1 comprises a parallel plate. 3. The superconductor according to claim 1, wherein the superconductor is made of a cylinder and has an electric insulating portion in all cross sections thereof so as not to be an electrically closed loop when the circuit crosses the cross section. Item 1. A biomagnetism measuring device according to item 1.