JP2000051169A - Biological magnetism measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological magnetism measuring instrument that can perform precise and stable measurement and treat users of various chest sizes due to a change in target parts or individual body sizes. SOLUTION: This biological magnetism measuring instrument is provided with multiple SQUID sensors 21 detecting magnetic signals of a subject and a Dewar 3 housing the sensors 21. The Dewar 3 is formed so that multiple detecting faces are spatially close to the surface of a subject body, and the intervals between the multiple SQUID sensors 21 are spatially changed in the Dewar 3. For example, distribution intervals are made narrower at the curved part of the Dewar 3 so that the distribution density of sensors becomes higher at the area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biomagnetic measuring apparatus for measuring a magnetic field (magnetic field) generated from a living body such as a brain or heart of a subject, and more particularly, to a method for measuring the size of a measurement site of the subject. Regardless, the present invention relates to a biomagnetism measuring device in which a plurality of magnetic sensors provided in a dewar (container) are set to be in an optimal state.

[0002]

2. Description of the Related Art A biomagnetic measuring device captures weak magnetic (magnetic field) signals generated from parts of a living body such as the brain and heart, and uses the signals to diagnose the functions of those parts.
Its development and research are being actively conducted.

[0003] As is well known in the art, for example, the human heart generates an electric current as it moves. This electrical signal is very weak, but can be measured non-invasively by various methods. One such method is biomagnetism measurement, which measures magnetism (magnetic field, magnetic field) generated by a current flowing through a living body. In particular, biomagnetic measurement for the brain is sometimes referred to as brain magnetic field measurement, and that for the heart is sometimes referred to as cardiac magnetic field measurement.

A conventional biomagnetism measuring device is generally detected by a bed on which a patient is placed or a device having the same function, a cylindrical or trough-shaped dewar having a magnetic sensor attached to a tip or a bottom, and a magnetic sensor. And a processing device having a computer for processing a detection signal taken out of the Dewar via a signal line.

From the viewpoint of the electric system, this biomagnetism measuring device has a sensor unit having a magnetic detection unit and a current detector as a magnetic sensor, and related electronics for signal processing, and has a specially devised device. It can also be called a sensitivity magnetic measurement system.

Each magnetic sensor includes a coil portion having a loop coil for detecting magnetism, and a current detector having a Josephson junction for converting a magnetic signal into a current signal. The coil unit is generally formed of a single-loop or multi-loop coil that generates a minute current by passing a magnetic flux. For example, when detecting a magnetic signal from the heart, it is desirable that the coil unit be disposed as close as possible to the chest of the subject. This is due to the change in the magnetic field strength, and the magnetic field strength decreases in proportion to the cube of the distance from the current source.

[0007] Magnetic sensors are required to have high sensitivity for detecting extremely weak magnetic signals. For this reason, recently, SQUIDs (Superconducting Quantum Interference Devices:
gQUantum Interference Device) is often used, and the use of a plurality of SQUIDs to increase the number of channels (for example, tens of channels) is also progressing. Recently, this S
QB operates at liquid nitrogen temperature (77K) YBCO
They are often made of materials.

A magnetic sensor using a superconducting material and including a current detector as described above maintains a superconducting state necessary for its operation and reduces Josephson noise, which is thermal noise caused by temperature rise. In addition, it is necessary to maintain a very low temperature.

In order to maintain the low temperature, the magnetic sensor is installed in an insulated container called Dewar, and is cooled by a refrigerant (liquid nitrogen or liquid helium) stored in the Dewar. A typical dewar is a cylinder about 55 cm in diameter and about 120 cm in length. As a cooling method, a method of immersing a magnetic sensor in a refrigerant stored in a Dewar and directly cooling the magnetic sensor is generally used. Since the dewar needs to store a refrigerant, the dewar usually has a double-layer structure having a vacuum heat insulating layer. At present, cryogenic liquid nitrogen or helium is indispensable to maintain the characteristics of the magnetic sensor comprising the SQUID in a superconducting state.

The reason why the Dewar is formed in a cylindrical shape or a tub shape in this way is that the magnetic sensor can be easily arranged on the inner bottom surface,
The prevention of evaporation of the refrigerant and the relatively good cooling efficiency are mentioned.

High sensitivity SQUID currently used
In the case of a biomagnetism measuring device using a magnetometer, a cylindrical dewar is placed, for example, directly above a chest of a subject lying on a bed. In order to detect a magnetic signal from a living body with high sensitivity, it is better to bring the magnetic sensor as close as possible to the body surface as described above. If the Dewar has a double-layer structure, the distance between the sensor and the body surface is longer by the vacuum heat insulating layer, so that the S / N of the detection signal is deteriorated. Not only the size of the dewar but also the necessity of disposing the sensor as close to the body surface as possible, there is a need to carefully design the geometric shape of the dewar. Usually, the magnetic sensors are arranged at spatially uniform intervals at or near the bottom surface inside the Dewar.

The processing apparatus is provided with patient image information collected by a modality such as an MRI (magnetic resonance imaging) apparatus or an X-ray CT scanner. Accordingly, the processing device processes the detection signal based on the magnetic sensor while referring to the image information to generate and display the image information. The function diagnosis of the living body is performed based on the generated / displayed information.

[0013]

For example, if the measurement site is a heart (chest), the magnetic signal is generated from the entire surface of the chest. Therefore, it is better to measure these signals as much as possible. It is considered that it is desirable from the viewpoint of improvement and, ultimately, improvement of measurement accuracy.

However, according to the above-described conventional biomagnetism measuring apparatus, a plurality of SQs
Since the arrangement interval of the UID sensor is always set to a certain value, in the case of a subject having a large chest area, a magnetic signal from the heart is picked up based on the large area.
The number of QUID sensors increases. On the other hand, in the case of a subject having a small chest area, the number of SQUID sensors involved in detecting a magnetic signal from the heart is reduced accordingly, and even the number of SQUID sensors required for measurement with an accuracy sufficient for diagnosis can be obtained. It may not be possible to secure. The measurement target includes not only adults but also children. In addition, even in adults, the breast area generally differs depending on gender. That is, in the conventional case, when the measurement target changes, the measurement accuracy fluctuates.

It is extremely difficult to prepare a plurality of types of sensor arrangement intervals in advance in accordance with the size of the chest area in an actual clinical setting in view of operation costs and operation time. . Therefore, there has been a situation in which even if the measurement accuracy is not sufficient depending on the measurement target, it must be accepted.

In addition, the conventional measuring apparatus has a problem regarding the shape of the dewar in the measurement of the magnetocardiogram. In the conventional case, even in the case of cardiac magnetic field measurement, a magnetic signal is detected from the front of the chest using a cylindrical dewar with a flat bottom. However, as described above, while the magnetic field radiated from the heart extends all around the chest, only the magnetic field measured in front of the chest is measured. For this reason, despite the fact that there is still room for improvement in terms of magnetic detection and measurement accuracy, no proposal has been made on this point.

Objects of the present invention The present invention has been made in view of the above-mentioned various unresolved problems of the prior art.

Therefore, the present invention can be applied to a single device even if the size of the measurement site of the subject changes depending on the type of the measurement object such as an adult, a child, and young and old, and also due to individual differences. It is a first object of the present invention to provide a biomagnetism measurement device that covers a subject and can always perform highly accurate and stable magnetic measurement. Particularly, when the measurement site is the heart (chest), it is possible to satisfactorily achieve such purpose.

Further, the present invention achieves the first object described above, and at the same time, detects as many magnetic signals radiated from the measurement site of the subject as possible, and increases the S / N to improve the measurement accuracy ( In other words, to improve the estimation accuracy of the magnetic field source)
This is the second purpose. In particular, since the heart is generally located on the left side of the center of the chest, at least the left chest side (part) is added to the measurement range to ensure that the purpose can be achieved.

[0020]

In order to achieve the above various objects, a biomagnetism measuring apparatus according to the present invention comprises a plurality of magnetic sensors for detecting a magnetic signal of a subject and a dewar accommodating the magnetic sensors. The dewar is formed in a shape having a plurality of detection surfaces spatially located around the body surface of the subject, and at least the arrangement interval between the plurality of magnetic sensors is spatially changed. And is arranged in the dewar.

Preferably, the Dewar has a shape in which at least two detection surfaces form a substantially L-shape when viewed from the body axis direction of the subject, and the two detection surfaces correspond to the subject. It is arranged to cover the front and side of the left chest. At this time, the Dewar has a curved detection surface that continuously curves and connects the two detection surfaces, and the magnetic sensor is arranged along the curved detection surface, It is preferable that the dewar is arranged such that the detection surface covers the body surface between the front and side surfaces of the left chest of the subject.

As a preferred example, the plurality of magnetic sensors can be arranged so that the mutual arrangement interval is narrowed as far as the curved detection surface and the sensor arrangement density is increased. As another preferred example, the plurality of magnetic sensors can be arranged so that only the mutual arrangement interval becomes narrower as far as the curved detection surface and the sensor arrangement density increases.

Further, for example, the Dewar has a shape in which at least three detection surfaces form a substantially U-shape when viewed from the body axis direction of the subject, and the at least three detection surfaces are formed by the subject. May be arranged so as to cover at least the front, side, and back of the left chest.

Further, it is preferable that each of the plurality of magnetic sensors is formed by a SQUID sensor having a differentiating direction, and the plurality of SQUID sensors are arranged such that the differentiating directions are directed in the same direction on each of the detection surfaces.

Further, the magnetic sensor comprises a SQUID sensor, and a cooling source provided outside the dewar, and a plurality of the magnetic sensors provided inside the dewar connected to the cooling source. A cooling means for cooling the SQUID sensor may be provided. In this case, for example, the cooling source is a refrigerator, and the cooling means is a heat pipe connected to the refrigerator.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First Embodiment A first embodiment will be described with reference to FIGS. 1 to 7 and FIGS.

The biomagnetism measuring apparatus according to this embodiment
An apparatus for measuring a cardiac magnetic field, wherein an L-shaped dewar is mounted as the dewar.

FIG. 1 shows a schematic configuration of the biomagnetism measuring device. The biomagnetism measuring apparatus includes a bed 1 on which a subject P is usually laid on his back, and a sensor unit 2 for detecting a magnetic flux generated by the heart of the subject P laid on the bed 1.
An L-shaped (substantially L-shaped) dewar 3 in which the sensor unit 2 is mounted; a pedestal 4 on which the L-shaped dewar 3 is mounted and fixed; and a drive of the sensor unit 2 and processing of a detection signal Drive / processing unit 5 for cooling and cooling mechanism 6 for sensor unit 2
And a control device 7 for controlling the entire device, an analysis device 8 for analyzing a detection signal of the sensor unit 2, and a display device 9 for displaying an analysis result.

Here, in FIG. 1, as a convenient coordinate axis, the length (longitudinal) direction of the table 1a of the bed 1, that is, the body axis direction of the subject P is generally set as the Z axis, The vertical direction is defined as the Y axis, and the width direction of the top plate is defined as the X axis.

The L-shaped dewar 3 is formed by molding a substantially rectangular parallelepiped plate-shaped closed casing of a predetermined height into a substantially L-shaped curved shape as shown in the figure (see FIG. 2). The length in the lateral direction when the casing is bent into an L-shape, that is, the length in the X-axis direction can sufficiently cover the body width of the subject P. That is, the width W in the lateral direction is longer than the height H of the casing. Also,
The degree of curvature of the curved portion C of the casing is set so as to conform as much as possible to the roundness of the body surface of the sleeping subject P from the front of the chest to the side of the chest. The curved portion C fits into the roundness of the body surface of the subject P, and has a structure in which a weak magnetic signal emitted from the heart can be detected with as high sensitivity as possible.

Due to the L-shaped curvature of the casing (ie, the L-shaped dewar 3), an L-shaped curved internal space IS is formed inside the casing when viewed from the direction facing the side surface (ie, the Z-axis direction). You. The internal space IS has a space portion ISy in the height (Y-axis) direction, a curved space portion ISc, and a width (X
The (axial) direction space portion ISx is formed continuously.

The entire casing is an outer casing 1
1a and the inner casing 11b, between which a vacuum insulation layer VS is formed. Inner casing 1
The inside of 1b forms the above-mentioned internal space IS. This internal space IS is also formed in a vacuum, and is vacuum insulated so that cold heat does not escape.

FIGS. 13 to 15 show an example of an improvement in the seal portion related to the vacuum heat insulating structure. The vacuum heat insulating layer VS and the inner space IS are formed in a vacuum of about 10 ⁻³ Torr, while the inner surface of the outer casing 11a and the inner casing 1 are formed.
The inner and outer surfaces of 1b are covered with a heat insulating film on which aluminum is deposited, thereby reducing heat inflow.
Further, the outer casing is provided with a suction port for evacuating the vacuum heat insulating layer VS and the internal space IS.
Furthermore, the inner spaces VS, I of the casings 11a, 11b
In order to maintain the airtightness between the S and the outside of the Dewar, the bonding portion of the outer casing 11a, its signal line drawing portion, and the drawing portion of the heat conduction mechanism such as a heat pipe are configured as shown in FIGS. . That is, as shown in FIG. 13, the outer casing 11a is airtightly bonded with the silicone rubber SL and the vacuum grease VG.
As shown in FIG. 14, the signal line SC is connected to the outer casing 1.
Silicon rubber SL and vacuum grease VG for 1a
Drawn through the airtight structure. In the figure,
Reference numeral MD is a molding agent. Further, as shown in FIG. 15, a heat transfer mechanism HT such as a heat pipe to be described later is drawn into the outer casing 11a via an airtight structure made of silicon rubber SL and vacuum grease VG.

By making such an improvement, heat inflow due to heat radiation is greatly reduced, and the cooling performance of the cooling mechanism can be further reduced. As a result, a refrigerator described later can be installed farther away from the Dewar, so that the mixing of magnetic noise due to the refrigerator can be reduced. Further, since both the vacuum heat insulating layer VS and the internal space IS need to be maintained at the same pressure, the structure and work of giving the inner casing a sealing property in order to increase the airtightness of the inaccessible inner casing are unnecessary. In spite of the complicated Dewar-shaped casing, there is a feature that the assembly becomes extremely easy. In addition, it is possible to adopt a structure in which a hole is formed in the inner casing in order to more easily arrange signal lines and to improve support and assembling properties of the casing and the sensor.

The sensor unit 2 includes a plurality of SQUID sensors 21... 21 for detecting magnetism. Each SQUID sensor 21 has a two-dimensional arrangement in the interior space IS of the casing of Dewar in a row along a series of spaces ISy, ISc, ISx, and a plurality of the rows are arranged in the Z-axis direction.

FIG. 3 shows an example of the sensor position based on this arrangement. In FIG. 3A, only the L-shaped dewar 3 is drawn.
The arrangement of the SQUID sensor 21 when the D-shaped dewar 3 is viewed from directly above the Y-axis (vertical) direction along the arrow A is shown in FIG. This is shown in FIG. This sensor arrangement pattern is one of the features of the present invention, and will be taken together in the section of mounting the SQUID sensor 21 described later.

Each magnetic sensor 21 has a cylindrical bobbin 22
For example, as shown in FIG.
Pick-up coil 23 wound in a hen type primary differential type
And a SQUID chip 24 (a superconducting ring and an input coil) having a Josephson coupling attached to a predetermined position of the bobbin 22. As a result, for example, when viewed on an XY plane orthogonal to the body axis (Z axis) direction, each SQUA
In FIG. 1, the differential direction of the ID sensor 21 is the differential direction at the rising portion (portion in the Y-axis direction) of the L-shaped dewar 3.
The direction becomes the X-axis (left / right) direction, and from that state, the differential direction gradually changes to the Y-axis (vertical) direction at the curved portion, and the differential direction = Y-axis (vertical) at the horizontal portion (portion in the X-axis direction). Direction.

Since a gap is formed in the curved portion C of the casing between the curved outer diameter sides of the SQUID sensors 21, the reference coil group 25 for removing the environmental magnetic field is provided in this gap. Thereby, the installation space of the coil can be effectively used.

The cooling mechanism 6 uses a refrigerator 31 and a heat pipe 32 directly connected to the refrigerator 31 to cool sensors and coils. This cooling structure
Details will be described later.

Driving / processing unit 4 provided in pedestal 4
Includes a drive circuit 41 and a preprocessor circuit 42. The drive circuit 41 includes the SQUID sensor 21
.., 21 for each sensor (that is, for each detection channel), for example, a plurality of FLL circuits. The preprocessor circuit 42 includes an analog filtering circuit, an amplifying circuit, and the like for preprocessing a signal detected by the drive circuit 41 using the SQUID sensors 21.

The control device 7 controls the operation of the bed, the drive circuit / preprocessor circuit, and the refrigerator. A monitor signal of the control device (a signal indicating what state the controlled side is in) is transmitted to the analysis device. The analyzer analyzes and displays electrocardiograms and myocardial electrophysiological phenomena using sensor signals and monitor signals obtained through a driving circuit and a preprocessor circuit.

By adopting such a dewar structure, in particular, the dewar portion before and after the curved portion C of the L-shaped dewar 3 fits the chest surface of the subject P, and
The distance between the QUID sensors 21 ... 21 and the chest surface can be kept short and constant. Therefore, a magnetic signal generated from the heart can be measured efficiently.

Next, an example of a more specific structure of the L-shaped dewar 3 and its cooling mechanism 6 will be described with reference to FIGS.

Since the cooling mechanism 6 uses a heat pipe, the principle of the heat pipe will be described first.

As an example, the heat pipe has a pipe as shown in FIG. 5, and a structure (wick) having a large capillary force such as a wire mesh or a porous material is provided on the inner wall side of the pipe, and heat is transported inside. A liquid (gas) called a working fluid is filled under a certain pressure. The wick has a structure in which a groove is formed in the inner wall of the pipe, and the groove can be used. The heat pipe has one end as an evaporating (endothermic) part and the other end as an aggregating (radiating) part, and the coagulated liquid in the wick enters the pipe due to the heat obtained from outside in the evaporating part. Evaporate. The heated steam moves to the other agglomeration part having a lower pressure. Since the moved steam is cooled, it aggregates in a liquid state on the wick, and the aggregated liquid is returned to the evaporator again by the capillary force of the wick. In the wick section, the pressure in the evaporating section is lower than in the aggregation section. This evaporation,
Cooling is enabled by transferring the heat absorbed in the evaporating section to the aggregating section through a cycle of agglomeration. Note that a heat insulating portion is provided between the evaporating portion and the aggregating portion, and the heat gradient is extremely low.

Here, since the heat pipe based on such a principle is used for the biomagnetism measuring device, a non-magnetic material is used for both the pipe material and the wick material. In addition, the pipe material is designed to prevent leakage of the internal liquid or gas so as to sufficiently withstand the internal pressure.

An L-shaped dewar 3 using this heat pipe
The structure of is shown schematically.

This L-shaped dewar 3 is, as shown in FIG.
An upper cover 3U located on the upper side of the drawing and a lower cover 3L located below the upper cover 3U are provided. And both covers 3
U and 3L are formed in an L-shape through a curved portion when viewed from the side (Z-axis direction). Both the covers 3U and 3L are connected to the outer casing 11 as described above.
a and the inner casing 11b.

The upper cover 3U integrally has a substantially L-shaped portion as viewed from the Z-axis direction facing the side surface as a whole and side covers 3Ua and 3Ub integrally provided at both ends thereof. Seal portions 51 and 52 are interposed at the contact portions between the side covers 3Ua and 3Ub and the lower cover 3L, respectively, to ensure airtightness. In addition, this lower cover 3
L is attached to the side covers 3Ua and 3Ub via seal portions 51 and 52 by opening and closing means such as screws. For this reason, the lower cover 3L is detachably openable and closable for convenience of maintenance and the like.

As described above, the space is defined by the upper cover 3U (and the side covers 3Ua and 3Ub) and the lower cover 3L. The internal space IS is connected to a vacuum pump 55 via a connection hose 54 inserted into a predetermined position of the upper cover 3U. For this reason, by operating the vacuum pump 55, the internal space IS is formed in a vacuum layer having a predetermined degree of vacuum, and is in a heat insulating state.

On the other hand, each of the upper cover 3U (and the side covers 3Ua and 3Ub) and the lower cover 3L
As described above, the vacuum layer ISa (ISb) has a double structure so as to have a vacuum layer ISa (ISb) therein.
Also has a heat insulating function. That is, the sensor has a double insulation structure with respect to the sensor placed inside the L-shaped dewar 3. In this way, consideration is given to minimizing heat inflow from the outside.

One end of a heat pipe 32 is connected to the refrigerator 31. The other end of the heat pipe 32 reaches the inside of the Dewar through a mounting hole on one side of the upper cover 3U sealed by the seal portion 56. With respect to the heat pipe 32, an exposed portion between the refrigerator 31 and the upper cover 3U and an exposed portion inside the dewar are covered with a heat insulating material 57. For this reason, the heat insulating material 57 has a heat insulating function for the heat pipe 32 and is designed to have a function of fixing and holding the heat pipe 32 while preventing heat from flowing out to the outside as much as possible.

The heat pipe 32 changes its direction at a right angle in the internal space IS of the dewar 3, extends out of the heat insulating material 57 and extends along the substantially L-shaped gap of the internal space IS, and is connected to the other end. Reach. A step is formed at the pipe reaching position inside the upper cover 3U, and the other end of the heat pipe 32 is attached and fixed to this step via a pipe attaching portion 58. Thereby, the entire heat pipe 32 is also fixed in the internal space IS.

Further, in the L-shaped dewar 3, a plurality of SQUID sensors 21... 21 are erected on the heat pipe 32 at fixed or adjusted intervals along the direction in which the pipe extends.

Each SQUID sensor 21 is provided via a heat conductor 58 provided on the joint surface with the pipe 32 as shown in FIG. 7, or is directly attached to the outer wall of the pipe 32. In any case, each SQUID sensor 21 is cooled by heat conduction. The SQUID sensor 21 is detachably attached. Since the surface closest to the Dewar 3 patient, ie, the lower cover 3L, can be opened and closed, if a defective channel occurs, the defective SQ
The UID sensor 21 can be easily replaced.

Further, nitrogen is used as a working fluid for the heat pipe 32. The hydraulic fluid may be changed depending on the material of the SQUID sensor 21. As long as the material of the SQUID sensor 21 can maintain the superconducting state, ammonia water, alcohol, methane, or the like may be used. If liquid nitrogen cannot be sufficiently cooled, neon, helium, or the like may be used.

As described above, in the present embodiment, the aggregation portion of the heat pipe 32 is provided with the liquid nitrogen tank which is a cryogenic refrigerant or the refrigerator 31 having a cooling capacity equivalent thereto, and the other end of the heat pipe 32 is provided. SQUID in evaporator
The sensors 21 are mounted. Thereby, the heat of the parts of the SQUID sensors 21... 21 can be transported to the aggregating part by the heat pipe 32, whereby the SQUID sensors 21.

Here, the SQUID sensors 21... 21 are attached to one end of the heat pipe along the axial direction, and the arrangement pattern arranged in the dewar will be described with reference to FIGS. 3 and 8 to 10 described above. explain.

3 (b) and 3 (c), the sensor arrangement density (the number of sensors arranged per unit area of the Dewar) and the sensor coil area (the magnetic flux of the loop coil) are indicated by circles C. (Through area: sensor area) is schematically shown. The direction of the change is linear as it goes toward the curved portion (corner) of the L-shaped dewar 3, as shown in FIGS.
The sensor arrangement density is increased and the coil area is reduced exponentially or in a multi-order (high-order) function. That is, in the case of the L-shaped dewar 3, the dewar measurement surface having the sensor arrangement pattern in which the sensor arrangement density is increased and the coil area is changed is different from the surface orthogonal to the Y-axis direction (detection surface) and the X-axis direction. It has two or more surfaces equivalently including a surface (detection surface) that is orthogonal. Note that only one of the sensor arrangement density and the coil area may be similarly changed.

Here, the sensor arrangement density is increased and / or the coil area is reduced as the position shifts to the curved portion of the L-shaped dewar 3. This is because a subject with a small chest area has the entire body on the left side. And positioning the left thoracic body surface closest to the curve of the Dewar, the magnetic signal radiated from the heart allows a greater number of SQUID sensors 2
1 and / or increasing the S / N of the magnetic signal. A subject having a large chest area is covered with a large number of SQUID sensors 21 by simply positioning the subject near the Dewar curve.

This sensor arrangement pattern can be implemented by changing to various types. This change example is shown in FIGS.
As shown in FIG. These figures show a pattern corresponding to the above-mentioned FIG. 3B, that is, a sensor arrangement pattern when the Dewar 3 is viewed from the upper side in the Y-axis direction, and (a) and (a ') in the upper part of each figure show the Dewar. 3 is a schematic diagram of the sensor arrangement and the coil diameter when viewed from the lateral direction (Z-axis direction), and lower parts (b) and (b ′) show the sensor arrangement and the coil diameter when the Dewar 3 is viewed from above in the vertical (Y-axis) direction. FIG.

Briefly, as shown in FIGS. 8 (a) and 8 (b), a Ketcen type primary differential coil and a high-temperature superconducting S
With the coil area of the QUID kept constant, the sensor arrangement density is set to be dense (large) so as to shift to the curved portion of the L-shaped dewar. FIGS. 6A and 6B are the same as FIGS.
The sensor arrangement shown in (b) is a multi-order (high-order) differential type. That is, as shown in FIG.
(At this time, the upper and lower SQUID sensors are installed in differentiating directions from each other), and the SQUID sensors 21
Is, for example, a first-order differential type, the difference is obtained by the upper and lower two stages U and L to form a second-order differential.

The sensor arrangement patterns shown in FIGS. 9A and 9B are similar to FIGS. 8A and 8B in that the sensor arrangement density is L-shaped with the coil area kept constant. The setting is made dense enough to shift to the curved part of the Dewar. However, the rate of change in the lateral (X-axis) direction is the same at any position in the body axis (Z-axis) direction as shown in FIG.
In this pattern, the rate of change of the sensor array density varies depending on the position in the (axis) direction. 9 (a ') and 9 (b') show the sensor arrangement shown in FIGS. 9 (a) and 9 (b) in a multi-order differential type.

Further, in the sensor arrangement patterns shown in FIGS. 10A and 10B, similarly to FIGS. 8A and 8B, the sensor arrangement density is L-shaped with the coil area kept constant. The setting is made dense enough to shift to the curved part of the Dewar. Where L
The sensor array density changes from sparse to dense from the periphery toward a predetermined position PS near the curved portion of the character dewar 3. The subject is positioned so that the heart portion of the subject is directly below the predetermined position PS. FIG.
(A ') and (b') show a multi-order differential type of the sensor arrangement shown in FIGS.

Therefore, an L-shaped dewar in which the arrangement density of SQUID sensors is set densely and the coil area is set small, or an L-shaped dewar in which only the arrangement density of SQUID sensors is set densely The subject's heart can be located at a position close to the part. This allows
The sensor array density is increased immediately above the heart and the spatial resolution is increased. Therefore, the analysis accuracy is also improved.

Further, the subject on the bed is, as described above,
By appropriately positioning the heart position near the curved part of the L-shaped dewar, the sensor density near the heart can be increased regardless of the body shape and physique of the subject such as a person with a wide chest, a narrow person, etc. , S / N can be improved, and a high and stable spatial resolution can always be ensured almost independently of the body shape of the subject.

The biomagnetism measuring apparatus according to the present embodiment has various excellent effects as compared with the conventional apparatus.

Specifically, first, the dewar structure has an L-shape when viewed from the direction facing the side surface (Z-axis direction) and has a two-dimensional spread when viewed from the vertical direction of the bed (Y-axis direction). By arranging the SQUID sensor two-dimensionally in the internal space, the SQUID sensor is also two-dimensionally located on a surface along the body side of the subject P. Therefore, a dewar structure suitable for cardiac magnetic field measurement is obtained, and a magnetic signal can be simultaneously detected from the anterior chest and the chest side, and a magnetic field from the heart can be efficiently collected. As a result, the number of detected data is larger and can be detected from various directions compared to the case of detecting from only the front chest or only the chest side as before, so the accuracy of magnetic field source analysis is greatly improved. I do.

In particular, the dewar of the above-described embodiment has a curved surface portion on the way from one flat surface portion to the other flat surface portion, and has a structure as smoothly as possible along the body surface of the subject. Also, a SQUID sensor is arranged two-dimensionally. Thereby, the magnetic signal can be measured from the oblique portion of the body surface in the same manner, so that the accuracy of the magnetic field source analysis can be further improved.

On the other hand, the above-mentioned L-shaped dewar is different from the conventional method in which the SQUID sensor is immersed in storing a liquid refrigerant, using a heat pipe, attaching a heat sink to the tip thereof, and circulating the wick. The SQUID sensor is cooled by latent heat of evaporation when the cooling liquid and the refrigerant passing through the inside of the wick of the heat pipe evaporate. As a result, a refrigerant circulation type dewar can be provided, and the shape of the dewar is not limited. Accordingly, the shape of the dual can be optimized for diagnosis.

The height (thickness) of the L-shaped dewar
May be a value that can secure the portions of the heat pipe, the SQUID sensor, and the heat insulating layer, so that a compact design can be achieved as a whole. There is also the advantage that the more compact the design, the easier it is to handle.

Further, by using the heat pipe, a large amount of refrigerant is not required at one time, and accordingly, the amount of evaporation can be suppressed and the operation cost of the apparatus can be reduced. Furthermore, since the storage position of the refrigerant can be separated from the Dewar, the size and weight of the Dewar can be reduced from this point as well.

Further, as described above, the sensor arrangement density and the coil area are changed as the shape of the L-shaped dewar is shifted to the curved portion. In addition, even when the size of the chest of a subject changes due to individual differences, a single device can reliably cover a variety of measurement sites of the subject with a desired number of sensors or more, and the accuracy is always constant. And stable and stable magnetic measurement can be performed. In particular, the combination of this effect and the above-described effect of simultaneously detecting the body surface region extending from the front of the chest to the left side of the chest at the same time, as much as possible from many magnetic signals radiated from the measurement site of the subject, In addition, the power is enormous from the viewpoint of detecting as close to the body surface as possible and increasing the S / N to improve the measurement accuracy.

FIG. 11 shows a modification of the arrangement of the SQUID sensor in view of the differential direction. When the SQUID sensor 21 is a vector type coil, a plurality of differential coils in all three directions are required, and the number of reference coils for detecting the reference signal of the environmental noise magnetic field when removing the environmental noise magnetic field is significantly increased. . However, considering the number and scale of the reference coils, the smaller the number of reference coils, that is, the number of reference signals, is easier to handle. If the differentiation direction is aligned in one direction,
The reference signal can be differentiated in only one direction. Further, in the case of a system having a detection surface in two directions, only two directions are sufficient as the differential directions of the reference signal. In other words, in order to use fewer reference coils, it is better to set the differential direction of each detection surface to one direction. In view of this, the detection surface (coil surface) described with reference to FIGS.
In the case of an apparatus for simultaneously measuring from two or more directions by using more than one surface, a structure in which the same differential direction is provided in the direction of the detection surface. FIG. 11 shows an example. As shown in the figure, in each of the Dewars 3A and 3B in which the SQUID sensor 21 is formed in a multi-order differential structure, the differential direction of the SQUID sensor 21 of the Dewar 3A exhibiting a detection surface parallel to one XZ plane is all in the Y-axis direction. SQUI of the dual 3B which is set in one direction and presents a detection plane parallel to the other YZ plane
The differential directions of the D sensor 21 are all set to one direction in the X-axis direction. Thereby, the number of reference coils (not shown) can be reduced to a necessary minimum, and the size can be suppressed.

Second Embodiment A second embodiment will be described with reference to FIG. Components that are the same as or equivalent to those of the above-described first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

This embodiment is characterized by a dewar structure, and is a further development of the dewar structure of the first embodiment.

The biomagnetism measuring apparatus according to this embodiment
A dewar 66 having a substantially U-shape as a whole is provided. The U-shaped dewar 66 includes a vertical dewar 66S facing the chest side of the subject P, an upper lateral dewar 66U facing the chest front, and a lower lateral dewar 66L.
It has a separate structure.

The divided dewars 66S, 66U, 66
L is substantially U (U) as shown in FIG.
It is joined in the shape of a letter. At this time, the vertical dewar 66S
Opposes the left side of the chest of the subject P, and the upper lateral dewar 66U and the lower lateral dewar 66L
Are positioned so as to face the chest front and back surfaces, respectively. That is, the three dewars can face the heart of the subject P from three directions. This substantially U-shaped dewar 66 is connected to an arm 64 via a connecting member 62 as shown in FIG.
Fixed and suspended.

Further, in order to make the dewar 66 easily accessible to the subject P, the table 1N of the bed 1 is formed in a U-shape opposite to the dewar 66, and the lower part thereof is placed on the bed. It is attached to the base. This inverted U-shaped structure achieves a retreat structure that allows the lower lateral dewar 66L to be positioned below the bed. Therefore, at least at the time of diagnosis, the lower lateral dewar 66L of the dewar 66 can be inserted to a position below the top plate 1N.

Each of the divided dewars 66S, 66U, and 66L independently has the same independent sensor structure and cooling structure as in the first embodiment described above, but the heat pipes 32S, 32U, 32L is connected to the common refrigerator 31. The refrigerator 31 is mounted on an arm 64 to save space.

In the biomagnetism measuring apparatus according to the second embodiment, an appropriate arrangement pattern of the improved SQUID sensor described above is selected and implemented.

As described above, the U-shaped dewar 66 is composed of the three planar (plate-shaped) divided dewars 66S, 66U, 66L, and the bed 1 has a structure accessible to the divided dewar 66L therein. As a result, it is possible to simultaneously measure not only the chest side and the chest front of the subject P but also the back of the subject P, and from the viewpoint of further enriching the detection data, the same operation and effect as described above can be obtained. Can be. In addition, since it has a separate structure, as in the first embodiment, the entire dewar can have a simple structure, which can contribute to a reduction in manufacturing costs and maintenance costs.

Also, of course, the first embodiment obtained
Simultaneous change in the arrangement density of the SQUID sensor 21 and the coil area, or change in only the arrangement density of the SQUID sensor 21 (ie, near the abutting sides of the divided dewars 66S, 66U corresponding to the curved portion of the entire dewar 66,
And / or the effect of increasing the sensor arrangement density and decreasing the coil area or increasing only the sensor arrangement density toward the abutting side of the divided dewars 66S and 66L can be obtained.

In each of the above embodiments and modifications thereof, the case where the magnetic measurement site of the subject is the heart has been described. However, this measurement site is not necessarily limited to the heart. For example, it may be a head.

The dewar has only to have a detection surface shape that matches the shape of the body surface of the measurement site as much as possible, and is not necessarily limited to the above-described L-shape or U-shape. These L-shape and U-shape can be formed into a deformed curved shape.

[0087]

As described above, according to the biomagnetism measuring apparatus of the present invention, the arrangement pattern (sensor arrangement density, coil arrangement) when a plurality of magnetic sensors formed by SQUID sensors or the like are arranged in a dewar. Area) is changed (at least the sensor arrangement density is increased) as it reaches the curved detection surface (curved portion) of the L-shaped dewar. Also, even when the size of the measurement site of the subject changes due to individual differences, a single device can cover those various subjects, and always perform accurate and stable magnetic measurement. it can. In particular, when the measurement site is the heart (chest), such an effect becomes remarkable.

According to the biomagnetism measuring apparatus of the present invention, in addition to the arrangement pattern of the magnetic sensors described above, the dewar is made to have an L-shaped (or substantially L-shaped) or Since it is formed in a U-shape (substantially U-shape), the above-described effect is obtained, and at the same time, as many magnetic signals radiated from the measurement site of the subject as possible are detected as many as possible.
By increasing / N, the measurement accuracy (that is, the estimation accuracy of the magnetic field source) can be improved. In particular, since the heart is generally located on the left side of the center of the chest, at least the left chest side (part) can be added to the measurement range, and such an effect can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an entire structure of an L-shaped dewar of a biomagnetism measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a series of appearances of an L-shaped dewar.

FIG. 3 is a view for explaining an arrangement pattern of SQUID sensors arranged in an L-type dewar.

FIG. 4 is a diagram illustrating a schematic structure of a first-order differential type SQUID sensor.

FIG. 5 is an explanatory diagram illustrating the principle of a heat pipe.

FIG. 6: L-shaped dewar heat pipe and SQUID
FIG. 3 is a partial cross-sectional view illustrating the arrangement of sensors.

FIG. 7 is an explanatory view showing an example of mounting a SQUID sensor.

FIG. 8 is a diagram schematically illustrating an example of an arrangement pattern of SQUID sensors.

FIG. 9 is a diagram schematically showing another example of the arrangement pattern of the SQUID sensors.

FIG. 10 is a diagram schematically showing still another example of the arrangement pattern of the SQUID sensors.

FIG. 11 is a view for explaining an arrangement method of SQUID sensors in which the differential directions are aligned for each detection surface.

FIG. 12 is a configuration diagram showing an entire structure of the biomagnetism measuring apparatus according to the second embodiment of the present invention, centering on a U-shaped dewar.

FIG. 13 is a partial cross-sectional view showing a bonding structure of an outer casing of an L-shaped dewar.

FIG. 14 is a partial cross-sectional view showing a structure for drawing a signal line into an outer casing of an L-shaped dewar.

FIG. 15 is a partial cross-sectional view showing a drawing structure of a heat conduction mechanism such as a heat pipe into an outer casing of an L-shaped dewar.

[Explanation of symbols]

Reference Signs List 1 bed 1N top plate 2 sensor unit 3 L-shaped dewar 3U upper cover 3L lower cover 4 pedestal 5 drive / processing unit 6 cooling mechanism 11a, 11b outer, inner casing 21 SQUID sensor 25 reference coil group 31 refrigerator (refrigerant tank) 32, 32S, 32U, 32L Heat pipe 54 Connecting hose 55 Vacuum pump 57 Insulating material 58 Heat conductor 62 Connecting member 63 Support column 64 Arm 66 U-shaped dewar 66S, 66U, 66L U-shaped dewar Forming a dewar

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Izumi Watanabe 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture Inside the Toshiba Nasu Plant (72) Inventor Yoshihiro Sakuma 1385-1, Shimoishigami, Otawara City, Tochigi Prefecture Stock Company F-term in Toshiba Nasu Factory (reference) 2G017 AA01 AC04 AD32 4C027 AA10 CC00 EE01 KK00 KK01

Claims (9)

[Claims] 1. A biomagnetism measuring apparatus comprising: a plurality of magnetic sensors for detecting a magnetic signal of a subject; and a dewar accommodating the magnetic sensors, wherein the dewar is provided around a body surface of the subject. Biomagnetic measurement characterized in that it is formed in a shape having a plurality of detection surfaces to be spatially positioned, and the plurality of magnetic sensors are arranged in the dewar by spatially changing at least an arrangement interval between the sensors. apparatus. 2. The dewar according to claim 1, wherein the dewar has a shape in which at least two detection surfaces are substantially L-shaped when viewed from the body axis direction of the subject. Is disposed so as to cover the front and side surfaces of the left chest of the subject. 3. The invention according to claim 2, wherein the dewar has a curved detection surface that continuously curves and connects the two detection surfaces, and connects the magnetic sensor to the curved detection surface. The biomagnetism measuring device, wherein the dewar is arranged so that the curved detection surface covers the body surface between the front and side surfaces of the left chest of the subject. 4. The invention according to claim 3, wherein the plurality of magnetic sensors are arranged such that the mutual arrangement interval is narrowed as far as the curved detection surface and the sensor arrangement density is increased. Characteristic biomagnetic measurement device. 5. The invention according to claim 3, wherein the plurality of magnetic sensors are arranged so that only the mutual arrangement interval is narrowed as far as the curved detection surface and the sensor arrangement density is increased. A biomagnetic measurement apparatus characterized by the above-mentioned. 6. The invention according to claim 1, wherein the dewar has a shape in which at least three detection surfaces form a substantially U-shape when viewed from the body axis direction of the subject, and the at least three detection surfaces are formed. A biomagnetism measurement apparatus, wherein a surface is arranged so as to cover at least a front surface, a side surface, and a back surface of the left chest of the subject. 7. The method according to claim 1, wherein each of the plurality of magnetic sensors has a differential direction.
A biomagnetism measuring apparatus comprising a SQUID sensor, and the plurality of SQUID sensors are arranged such that the differential directions thereof are directed to the same direction on each of the detection surfaces. 8. The invention according to claim 1, wherein the magnetic sensor comprises a SQUID sensor, while a cooling source provided outside the dewar and a state in which the cooling source is connected inside the dewar. And a cooling means for cooling the plurality of SQUID sensors. 9. The biomagnetism measuring apparatus according to claim 8, wherein the cooling source is a refrigerator, and the cooling means is a heat pipe connected to the refrigerator.