JP4077945B2 - Biomagnetic measurement device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biomagnetic measurement device that measures magnetism (magnetic field) generated from a living body such as a subject's brain and heart, and in particular, regardless of the size of the measurement site of the subject. The present invention relates to a biomagnetism measuring apparatus that is set so that an arrangement state of a plurality of magnetic sensors arranged inside is optimal.
[0002]
[Prior art]
Biomagnetic measurement devices capture weak magnetic (magnetic field) signals generated from parts such as the brain and heart of a living body and use them for functional diagnosis of those parts. In recent years, development and research have been actively conducted. It has been broken.
[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 of the methods is biomagnetism measurement, which measures magnetism (magnetic field, magnetic field) generated due to current flowing in the living body. In particular, biomagnetic measurement for the brain may be referred to as cerebral magnetic field measurement, and it may be referred to as heart magnetic field measurement separately from the cardiac magnetic field measurement.
[0004]
Conventional biomagnetism measuring devices are generally detected by a bed or a device having the same function as a bed on which a patient is placed, a cylindrical or bowl-shaped dewar with a magnetic sensor attached to the tip or bottom, and a signal line. And a processing device having a computer for processing the detection signal extracted outside the dewar.
[0005]
When this biomagnetism measuring device is seen from the electric system, it has a sensor unit having a magnetic detection unit and a current detector as a magnetic sensor, and related electronics for signal processing, and is a highly sensitive magnetic measurement with special measures. It can be said to be a system.
[0006]
Each magnetic sensor includes a coil unit having a loop coil that detects magnetism, and a current detector having a Josephson junction that converts the magnetic signal into a current signal. The coil section is generally composed of a single-loop or multi-loop coil that generates a minute current through the passage of 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 because the magnetic field intensity is weakened in proportion to the cube of the distance from the current source.
[0007]
The magnetic sensor is required to have high sensitivity for detecting a very weak magnetic signal. For this reason, recently, SQUID (Superconducting Quantum Interference Device) is often used, and multi-channeling (for example, several tens of channels) using a plurality of SQUIDs is also progressing. Recently, this SQUID is often made of YBCO material that operates at liquid nitrogen temperature (77K).
[0008]
A magnetic sensor including a current detector using a superconducting material in this way maintains a superconducting state necessary for its operation, and also reduces Josephson noise, which is thermal noise due to temperature rise, It is necessary to maintain a very low temperature.
[0009]
In order to maintain this low temperature, the magnetic sensor is installed in a heat insulating container called a dewar and cooled by a refrigerant (liquid nitrogen or liquid helium) stored in the dewar. A typical dewar is cylindrical with a diameter of about 55 cm and a length of about 120 cm. As a cooling method, a method in which a magnetic sensor is immersed in a refrigerant stored in a dewar and directly cooled is generally used. Since it is necessary to store the refrigerant in the dewar, the dewar usually has a double layer structure having a vacuum heat insulating layer. At present, cryogenic liquid nitrogen and helium are indispensable to maintain the characteristics of the magnetic sensor composed of SQUID in the superconducting state.
[0010]
The reason why the dewar is formed in a cylindrical shape or a saddle shape in this way is that it is easy to place a magnetic sensor on the inner bottom surface, the evaporation of the refrigerant is prevented, and the cooling efficiency is relatively good.
[0011]
In the case of a biomagnetic measurement apparatus using a highly sensitive SQUID magnetometer currently in use, a cylindrical dewar is placed, for example, just above the chest of a subject who is lying on the bed. In order to detect a magnetic signal from a living body with high sensitivity, as described above, the magnetic sensor should be as close to the body surface as possible. When the dewar has a double-layer structure, the distance between the sensor and the body surface becomes as much as 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 need to place the sensor as close to the body surface as possible, we want to carefully design the geometric shape of the dewar. Usually, the magnetic sensors are arranged at equal intervals in the bottom surface inside the dewar or at a position close to this surface.
[0012]
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. Therefore, 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. A function diagnosis of the living body is performed based on the generation / display information.
[0013]
[Problems to be solved by the invention]
For example, if the measurement site is the heart (chest), the magnetic signal is generated from the entire surface of the chest. Therefore, measuring as many of these signals as possible can improve the S / N and therefore the measurement accuracy. This is desirable from the viewpoint.
[0014]
However, according to the above-described conventional biomagnetic measuring device, since the arrangement intervals of the plurality of SQUID sensors arranged in the dewar are always set to a certain value, the case where the subject has a wide chest area Depending on the area, the number of SQUID sensors that pick up magnetic signals from the heart increases. On the other hand, in the case of a subject with a small chest area, the number of SQUID sensors involved in the detection of magnetic signals from the heart is reduced accordingly, and even the number of SQUID sensors necessary for measurement with an accuracy sufficient for diagnosis can be obtained. It may not be secured. Measurement targets include children as well as adults. Even in adults, the chest area generally differs depending on the sex. That is, in the conventional case, there is a problem that the measurement accuracy varies when the measurement object changes.
[0015]
It is very difficult to prepare a dewar having a plurality of types of sensor arrangement intervals in advance according to the size of the chest area in an actual clinical setting in consideration of operational costs and operational effort. Therefore, depending on the measurement object, even when the measurement accuracy is not sufficient, it was in a situation that it was inevitably accepted.
[0016]
In addition, the conventional measuring apparatus has a problem regarding the shape of the dewar in the magnetocardiogram measurement. In the conventional case, even in the case of measuring a magnetocardiogram, a magnetic signal is detected from the front of the chest using a cylindrical dewar with a flat bottom surface. However, as described above, the magnetic field radiated from the heart extends over the entire circumference of the chest, whereas only the magnetic field on the front surface is measured. For this reason, although there is still room for improvement in terms of magnetic detection and measurement accuracy, no proposal has been made on this point.
[0017]
Object of the present invention
The present invention has been made in view of various unsolved problems of the above-described prior art.
[0018]
Therefore, the present invention provides a variety of examinations with a single device even when the size of the measurement site of the subject varies depending on the type of measurement target, such as adults and children, young and old men and women, and individual differences. It is a first object of the present invention to provide a biomagnetic measuring device that covers a person and can always perform accurate and stable magnetic measurement. In particular, when the measurement site is the heart (chest), this object can be satisfactorily achieved.
[0019]
  In addition, the present invention achieves the first object described above, and at the same time, detects as many magnetic signals as possible from the measurement site of the subject as many faces as possible, and S / NratioThe second object is to improve the measurement accuracy (that is, the estimation accuracy of the magnetic field source). In particular, since the heart is generally located to the left of the center of the chest, at least the left chest side surface (part) is added to the measurement range so that this purpose can be reliably achieved.
[0020]
[Means for Solving the Problems]
  In order to achieve the various objects described above, the biomagnetic measurement device of the present invention includes a plurality of magnetic sensors for detecting a magnetic signal of a subject and a dewar that houses the magnetic sensor, and the dewar is the test subject. Multiple detection surfaces spatially positioned around the body surface of the personAnd at least a part of the detection surface has a flat surface portion.Forming at least one of the plurality of magnetic sensors between the sensors.Narrow the vicinity of the edge of the detection surface to increase the sensor arrangement densityArranged in the dewarIs.
[0021]
Preferably, 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, and the two detection surfaces are formed on the left chest of the subject. It arrange | positions so that a front surface and a side surface may be covered. At this time, the dewar has a curved detection surface that continuously curves and connects the two detection surfaces, and the magnetic sensor is disposed along the curved detection surface. It is desirable to arrange the dewar so that the detection surface covers the body surface between the front and side surfaces of the left chest of the subject.
[0022]
Further, as a preferred example, the plurality of magnetic sensors can be arranged so that the arrangement interval between the plurality of magnetic sensors becomes narrower toward the curved detection surface so that the sensor arrangement density increases. As another preferred example, the plurality of magnetic sensors can be arranged so that only the mutual arrangement interval becomes narrower toward the curved detection surface and the sensor arrangement density is increased.
[0023]
  Further, for example, when the dewar is viewed from the body axis direction of the subject, at least three detection surfaces are substantially U-shaped.Or approximately U-shapedThe at least three detection surfaces may be arranged so as to cover at least the front surface, the side surface, and the back surface of the left chest of the subject.
[0024]
Further, it is preferable that each of the plurality of magnetic sensors is formed by a SQUID sensor having a differential direction, and the plurality of SQUID sensors are arranged so that the differential direction faces the same direction on each of the detection surfaces.
[0025]
Further, the magnetic sensor is composed of a SQUID sensor, a cooling source disposed outside the dewar, and a plurality of SQUID sensors disposed in the dewar in a state of being connected to the cooling source. Cooling means for cooling 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]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0027]
First embodiment
1st Embodiment is described based on FIGS. 1-7 and FIGS. 13-15.
[0028]
The biomagnetic measurement apparatus according to this embodiment is an apparatus for measuring a cardiac magnetic field, and is characterized by mounting an L-shaped dewar as its dewar.
[0029]
FIG. 1 shows a schematic configuration of this biomagnetic measuring apparatus. The biomagnetism measuring apparatus includes a bed 1 for laying a subject P in a state where the subject P is usually placed on his back, a sensor unit 2 for detecting magnetic flux generated by the heart of the subject P laid on the bed 1, and the sensor. L-shaped (substantially L-shaped) dewar 3 with the portion 2 mounted therein, a pedestal 4 on which the L-shaped dewar 3 is placed and fixed, and a drive for use in driving the sensor unit 2 and processing detection signals The processing unit 5, the cooling mechanism 6 of the sensor part 2, the control apparatus 7 of the whole apparatus, the analysis apparatus 8 which analyzes the detection signal of the sensor part 2, and the display apparatus 9 which displays an analysis result are provided.
[0030]
Here, in FIG. 1, as a convenient coordinate axis, the length (longitudinal) direction of the top plate 1a of the bed 1, that is, generally the body axis direction of the subject P is the Z axis, and the top and bottom direction of the top plate is The Y axis and the width direction of the top plate are defined as the X axis.
[0031]
The L-shaped dewar 3 is a substantially rectangular parallelepiped having a predetermined height and is formed into a plate-shaped hermetic casing that is curved in a substantially L shape as shown in the figure (see FIG. 2). The lateral direction when the casing is bent in 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 transverse direction is longer than the height H of the casing. Further, the degree of curvature of the curved portion C of the casing is set so as to match the roundness of the body surface from the front of the chest of the sleeping subject P to the side of the chest as much as possible. The curved portion C fits to the roundness of the body surface of the subject P, and has a structure in which a weak magnetic signal radiated from the heart can be detected with as high sensitivity as possible.
[0032]
Due to the L-shaped curve of the casing (that is, the L-shaped dewar 3), an internal space IS that is also curved in an L-shape is formed inside the casing as viewed from the direction facing the side surface (that is, the Z-axis direction). In this internal space IS, a height (Y-axis) direction space portion ISy, a curved space portion ISc, and a width (X-axis) direction space portion ISx are continuously formed.
[0033]
The casing is entirely formed of an outer casing 11a and an inner casing 11b, and a vacuum heat insulating layer VS is formed between them. The inside of the inner casing 11b forms the internal space IS described above. This internal space IS is also formed in a vacuum, and is insulated by vacuum so that cold heat does not escape.
[0034]
Examples of improvement of the seal portion related to this vacuum heat insulating structure are shown in FIGS. The vacuum heat insulating layer VS and the internal space IS are 10^-3While a vacuum of about Torr is formed, the inner side surface of the outer casing 11a and the inner side surface and the outer side surface of the inner casing 11b are covered with a heat insulating film deposited with aluminum, thereby reducing heat inflow. Further, the outer casing is provided with a drawing port for evacuating the vacuum heat insulating layer VS and the internal space IS. Furthermore, in order to maintain the airtightness between the inner spaces VS and IS of the casings 11a and 11b and the outside of the dewar, the bonded portion of the outer casing 11a, the signal wire drawing portion, and the drawing portion of the heat conduction mechanism such as a heat pipe. Is configured as shown in FIGS. That is, as shown in FIG. 13, the outer casing 11a is hermetically bonded by the silicon rubber SL and the vacuum grease VG. Further, as shown in FIG. 14, the signal line SC is drawn into the outer casing 11a through an airtight structure of silicon rubber SL and vacuum grease VG. In the figure, reference sign MD is a molding agent. Further, as shown in FIG. 15, a heat conduction mechanism HT such as a heat pipe, which will be described later, is drawn into the outer casing 11a through an airtight structure with silicon rubber SL and vacuum grease VG.
[0035]
By making such improvements, heat inflow due to heat radiation is greatly reduced, and the cooling performance of the cooling mechanism can be made smaller. Thereby, since the refrigerator mentioned later can be separated from a dewar and can be installed in the distance, mixing of the magnetic noise resulting from a refrigerator can be reduced. Further, since both the vacuum heat insulating layer VS and the internal space IS only need to be maintained at the same pressure, a structure and work such as providing the inner casing with a sealing property in order to increase the airtightness of the inner casing which is difficult to reach are unnecessary. In spite of the complicated dewar-shaped casing, the assembly is extremely easy. In addition, a structure in which a hole is formed in the inner casing can be employed in order to more easily wire the signal line and to improve support and assembling of the casing and the sensor.
[0036]
The sensor unit 2 includes a plurality of SQUID sensors 21 to 21 for magnetic detection. Each SQUID sensor 21 has a two-dimensional arrangement in the inner space IS of the Dewar casing in a row along the series of space portions ISy, ISc, ISx, and a plurality of rows in the Z-axis direction.
[0037]
An example of the sensor position by this arrangement is shown in FIG. FIG. 4A shows only the L-shaped dewar 3 and shows the arrangement of the SQUID sensor 21 when the L-shaped dewar 3 is viewed along the arrow A from directly above the Y-axis (vertical) direction. This is shown in (b), and when viewed along the arrow B from the side of the X-axis (lateral) direction, 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.
[0038]
Each magnetic sensor 21 includes a cylindrical bobbin 22, a pickup coil 23 wound around the bobbin 22 in, for example, a Ketchen type first-order differential type, and a Josephson coupling attached to a predetermined position of the bobbin 22. SQUID chip 24 (superconducting ring body and input coil). As a result, for example, when viewed on the XY plane orthogonal to the body axis (Z axis) direction, the differential direction of each SQUID sensor 21 is the rising portion (the Y axis direction portion) of the L-shaped dewar 3 in FIG. The differential direction becomes the X axis (left and right) direction, the differential direction gradually changes from the state to the Y axis (vertical) direction at the curved portion, and the differential direction = Y axis in the horizontal portion (X axis direction portion). (Vertical) direction.
[0039]
Since there is a gap between the curved outer diameter sides of the SQUID sensors 21 in the curved portion C of the casing, a reference coil group 25 for removing the environmental magnetic field is installed in this gap. Thereby, the installation space of a coil can be utilized effectively.
[0040]
The cooling mechanism 6 uses a refrigerator 31 and a heat pipe 32 directly connected to the refrigerator 31 to cool the sensor and the coil. This cooling structure will be described in detail later.
[0041]
  Drive / processing unit provided in pedestal 45Comprises a unit of a drive circuit 41 and a preprocessor circuit 42. The drive circuit 41 is composed of, for example, a plurality of FLL circuits that drive the SQUID sensors 21... 21 for each sensor (that is, for each detection channel). The preprocessor circuit 42 includes an analog filtering circuit, an amplifier circuit, and the like that preprocess signals detected by the drive circuit 41 using the SQUID sensors 21.
[0042]
  The control device 7 includes a bed, a drive circuit41・ Preprocessor circuit42,refrigerator31To control the operation. Control device7Monitor signal (a signal indicating what state the controlled side is in) is transmitted to the analyzer. Analysis device8In the drive circuit41・ Preprocessor circuit42Electrocardiograms and myocardial electrophysiology are analyzed and displayed using sensor signals and monitor signals obtained through.
[0043]
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 body surface of the subject P, and the SQUID sensors 21... The distance between the two can be kept short and constant. Therefore, the magnetic signal generated from the heart can be measured efficiently.
[0044]
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.
[0045]
  This cooling mechanism 6 is a heat pipe32First, heat pipe32The principle will be described.
[0046]
  heat pipe32As an example, as shown in FIG. 5, the pipe has a pipe, a structure (wick) having a large capillary force such as a wire mesh or a porous material on the inner wall side of the pipe, and an operation that enables heat to be transferred to the inside. A liquid (gas) called a liquid is filled under a certain pressure. The wick has a structure in which a groove is cut in the inner wall of the pipe, and the groove can be used. One end of the heat pipe is an evaporation (endothermic) part, and the other end is an agglomeration (heat dissipation) part, and the condensed liquid in the wick is put into the pipe due to the heat obtained from the outside in the evaporation part. Evaporate. The steam with heat moves to the other agglomerated part having a low pressure. Since the vapor | steam which has moved is cooled, it agglomerates in the liquid state to a wick part, and this aggregate liquid returns to an evaporation part again by the capillary force of a wick. In the wick part, the pressure in the evaporation part is lower than that in the aggregation part. Cooling is possible by carrying the endotherm in the evaporation section to the aggregation section through this evaporation and aggregation cycle. In addition, it is a heat insulation part between the evaporation part and the aggregation part, and the thermal gradient is very low.
[0047]
  Here is the heat pipe of this principle32Is used for the biomagnetism measuring device, non-magnetic materials are used for both the pipe material and the wick material. Also, the pipe material prevents leakage of internal liquid and gas so as to sufficiently withstand the internal pressure.
[0048]
  This heat pipe321 schematically shows the structure of an L-shaped dewar 3 using
[0049]
As shown in FIG. 6, the L-shaped dewar 3 includes an upper cover 3U positioned on the upper side of the drawing and a lower cover 3L positioned on the lower side thereof. The entire cover 3U, 3L is formed in an L shape through a curved portion when viewed from the side surface direction (Z-axis direction). Both the covers 3U and 3L have a double heat insulating structure composed of the outer casing 11a and the inner casing 11b as described above.
[0050]
The upper cover 3U integrally has a substantially L-shaped portion as viewed from the Z-axis direction, which faces the side surface as a whole, and side surface covers 3Ua and 3Ub that stand integrally at both ends thereof. Seal portions 51 and 52 are respectively inserted in contact portions between the side covers 3Ua and 3Ub and the lower cover 3L to ensure airtightness. The lower cover 3L is attached to the side covers 3Ua and 3Ub via seal parts 51 and 52 by opening and closing means such as screws. For this reason, the lower cover 3L can be freely opened and closed for the convenience of maintenance and the like.
[0051]
Thus, the upper cover 3U (and the side covers 3Ua and 3Ub) and the lower cover 3L are defined, and a space IS is formed therein. This internal space IS is connected to a vacuum pump 55 via a connecting hose 54 inserted through 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.
[0052]
On the other hand, each of the upper cover 3U (and the side covers 3Ua and 3Ub) and the lower cover 3L has a double structure so as to have a vacuum layer ISa (ISb) inside as described above. ISb also has a heat insulating function. That is, a double heat insulation structure is provided for the sensor placed inside the L-shaped dewar 3. Thus, consideration is given to suppressing heat inflow from the outside as much as possible.
[0053]
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 3 </ b> U 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 with respect to the heat pipe 32 and is designed to perform the function of fixing and holding the heat pipe 32 while preventing the heat outflow to the outside as much as possible.
[0054]
The heat pipe 32 changes its direction at right angles in the internal space IS of the dewar 3, passes through the heat insulating material 57, extends as it is along the substantially L-shaped gap of the internal space IS, and reaches the other end. A step portion is formed at the pipe arrival position inside the upper cover 3U, and the other end portion of the heat pipe 32 is attached and fixed to the step portion via a pipe attachment portion 58. Thereby, the entire heat pipe 32 is also fixed in the internal space IS.
[0055]
In the L-shaped dewar 3, a plurality of SQUID sensors 21... 21 are erected on the heat pipe 32 along the pipe extending direction at regular intervals or adjusted intervals.
[0056]
  Each SQUID sensor 21 is as shown in FIG.heatVia a thermal conductor 58 provided on the joint surface with the pipe 32, orheatIt 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 patient of the Dewar 3, that is, the lower cover 3L can be opened and closed, when a defective channel occurs, the defective SQUID sensor 21 can be easily replaced.
[0057]
Further, nitrogen is used as the working fluid of 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 sufficiently cool, neon, helium, or the like may be used.
[0058]
As described above, in this embodiment, the aggregation portion of the heat pipe 32 is provided with the liquid nitrogen tank that is a cryogenic refrigerant or the refrigerator 31 having the cooling capacity corresponding thereto, and the other evaporation portion of the heat pipe 32 is provided in the other evaporation portion. The SQUID sensors 21... 21 are attached. Thereby, the heat | fever of the part of SQUID sensor 21 ... 21 can be conveyed to the aggregation part by the heat pipe 32, and, thereby, SQUID sensor 21 ... 21 is cooled.
[0059]
  Here, the SQUID sensors 21... 21 are attached to one end of the heat pipe along the axial direction thereof so that the dewar is obtained.3The arrangement pattern arranged inside will be described with reference to FIGS. 3 and 8 to 10 described above.
[0060]
  The sensor arrangement pattern in FIGS. 3B and 3C has a sensor arrangement density (dewar3The number of sensors arranged per unit area) and the coil area of the sensor (the magnetic flux penetration area of the loop coil: sensor area) are both schematically changed. The direction of the change is linear, exponential, or multi-order (higher order) as it proceeds toward the curved portion (corner portion) of the L-shaped dewar 3, as shown in FIGS. Functionally, the sensor placement density is increased and the coil area is reduced. That is, in the case of this L-shaped dewar 3, a dewar measurement surface having a sensor arrangement pattern in which the sensor arrangement density is increased and the coil area is changed is a surface (detection surface) orthogonal to the Y-axis direction and the X-axis direction. Two or more surfaces are equivalently included including the orthogonal surface (detection surface). Only one of the sensor arrangement density and the coil area may be changed in the same manner.
[0061]
  Here, the more the transition to the curved portion of the L-shaped dewar 3, the higher the sensor arrangement density and / or the smaller the coil area is. The left chest body surface is dewar3The magnetic signal emitted from the heart is detected by a greater number of SQUID sensors 21 and / or the S / N of the magnetic signal.ratioDepends on rising. A subject having a large chest area is covered with a large number of SQUID sensors 21 by simply positioning in close proximity to the Dewar curve.
[0062]
This sensor arrangement pattern can be implemented in various types. Examples of this change are shown in FIGS. These figures show a pattern corresponding to the above-described FIG. 3B, that is, a sensor arrangement pattern in a state where the dewar 3 is viewed from the upper side in the Y-axis direction, and (a) and (a ′) at the top of each figure are dewars. 3 is a schematic diagram of sensor arrangement and coil diameter as viewed from the lateral direction (Z-axis direction), and (b) and (b ′) in the lower stage are schematic diagrams of sensor arrangement and coil diameter as viewed from the upper side of the dewar 3 in the vertical (Y-axis) direction. FIG.
[0063]
  Briefly, as shown in FIGS. 8A and 8B, the sensor arrangement density is set to an L-shaped dewar in a state where the coil area of a ketcen type first-order differential type coil or a high-temperature superconducting SQUID is constant.3The denser (larger) is set so as to shift to the curved portion. (A ') and (b') are the arrangements of the sensors shown in (a) and (b) in the multi-order (higher order) differential type. That is, as shown in FIG. 5 (a '), the number of sensor groups in the dewar 3 is set to two upper and lower stages U and L (at this time, the upper and lower SQUID sensors are installed in the differential direction), If the SQUID sensor 21 of the stage is, for example, a first-order differential type, the difference is formed by the upper and lower two stages U and L to form a second-order derivative.
[0064]
  Further, the sensor arrangement pattern shown in FIGS. 9A and 9B is similar to FIGS. 8A and 8B in that the sensor arrangement density is set to an L-shaped dewar in a state where the coil area is constant.3It is set so densely that it shifts to the curved portion. However, as shown in FIG. 8, the rate of change in the lateral (X-axis) direction is the same at any position in the body axis (Z-axis) direction, and the sensor according to the position in the body axis (Z-axis) direction. The pattern has a different change rate of the array density. 9A and 9B show the sensor arrangement shown in FIGS. 9A and 9B in a multi-order differential type.
[0065]
  Furthermore, the sensor arrangement pattern shown in FIGS. 10A and 10B is similar to FIGS. 8A and 8B in that the sensor arrangement density is set to an L-shaped dewar with a constant coil area.3It is set so densely that it shifts to the curved portion. However, the sensor array density changes from sparse to dense toward the predetermined position PS near the curved portion of the L-shaped dewar 3. The subject is positioned so that the heart portion of the subject comes directly below the predetermined position PS. FIGS. 10A and 10B show the sensor arrangement shown in FIGS. 10A and 10B in a multi-order differential type.
[0066]
  Therefore, SQUID sensor21L-shaped dewar with a dense array density and a small coil area3Or SQUID sensor21L-shaped dewar in which only the arrangement density of3The heart portion of the subject can be positioned at a position near the curved portion. As a result, the sensor arrangement density is increased immediately above the heart and the spatial resolution is increased. Therefore, the analysis accuracy is also improved.
[0067]
  Also sleeper1The upper subject has an L-shaped dewar as described above.3The sensor density near the heart is increased regardless of the body type and physique of the subject, such as a person with a wide chest or a narrow person, by appropriately positioning at a position near the curved portion of the S / N.ratioImprove the subjectPIt is always possible to ensure a high and stable spatial resolution regardless of the body shape.
[0068]
The biomagnetic measurement apparatus according to the present embodiment has various excellent effects as compared with the conventional apparatus.
[0069]
  Specifically, first, it is L-shaped when viewed from the direction facing the side surface (Z-axis direction), and the bed.1The dewar structure has a two-dimensional expansion as seen from the vertical direction (Y-axis direction) of the SQUID sensor in the inner space.21By placing the SQUID sensor in a two-dimensional manner on the surface along the body side of the subject P21Is located. Therefore, a dewar structure suitable for cardiac magnetic field measurement is obtained, magnetic signals can be detected simultaneously from the front and chest sides, and the magnetic field from the heart can be collected efficiently. As a result, the number of detected data is larger and the detection can be performed from various directions compared to the case of detecting from the front of the chest or the side of the chest as in the past. To do.
[0070]
  In particular, the dewar of the embodiment described above.3Has a curved surface portion on the way from one flat surface portion to the other flat surface portion, and has a structure that follows the body surface of the subject as smoothly as possible, and the curved surface portion also has a two-dimensional SQUID sensor.21Is arranged. Thereby, since a magnetic signal can be measured in the same manner from an oblique portion of the body surface, the magnetic field source analysis accuracy can be further improved.
[0071]
  On the other hand, the above-mentioned L-shaped dewar3SQUID sensor while storing liquid refrigerant as before21Unlike the soaking method, heat pipe32, A heat sink attached to the tip, cooling liquid circulating in the wick, and heat pipe32SQUID sensor by the latent heat of vaporization when the refrigerant passing through the wick evaporates21To cool down. As a result, the refrigerant circulation type dewar3Can provide the dewar3Any shape can be chosen. Therefore, Dua3Can be optimized for diagnosis.
[0072]
  This L-shaped dewar3The height (thickness) of the heat pipe32, SQUID sensor21And any value that can secure the portion of the heat insulation layer, a compact design as a whole is possible. There is an advantage that it is easy to handle as it is designed to be compact.
[0073]
  Also heat pipe32By using this, a large amount of refrigerant is not required at one time, and the amount of evaporation can be suppressed correspondingly, and the operation cost of the apparatus can be reduced. In addition, the storage location of the refrigerant3From this point, Dewa3Can be reduced in size and weight.
[0074]
  Furthermore, as described above, the sensor arrangement density and the coil area can be changed to an L-shaped dewar.3The subject was changed as it moved to the curved part of the subject, such as adults and children, men and women of all agesPEven if the size of the subject's chest changes due to differences in the types of individuals or due to individual differences, the measurement site of those various subjects can be assured with a desired number of sensors or more with a single device. Therefore, it is possible to always perform magnetic measurement with high accuracy and stability. In particular, the combination of this effect and the above-described effect of simultaneously detecting the body surface region from the front of the chest to the left side of the chest, the magnetic signal radiated from the measurement site of the subject as many as possible, Moreover, it detects as close to the body surface as possible, and S / NratioThe power is tremendous from the viewpoint of improving measurement accuracy.
[0075]
  SQUID sensor21FIG. 11 shows a modification relating to the arrangement 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 is significantly increased when the environmental noise magnetic field is removed. . However, considering the number of installed reference coils and the scale, it is easier to handle a reference coil having a smaller number of reference signals. If the differential directions are aligned in one direction, only one differential direction of the reference signal is required. In the case of a two-direction detection surface system, only two directions are sufficient for the differential direction of the reference signal. That is, 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, in an apparatus that uses two or more detection surfaces (coil surfaces) described in FIGS. 8 to 10 to measure simultaneously from two or more directions, the same differential direction as the detection surface direction. Make the structure to have. An example is shown in FIG. 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 directions of the SQUID sensor 21 of the dual 3A exhibiting a detection surface parallel to one XZ plane are all in the Y-axis direction. The differential direction of the SQUID sensor 21 of the dual 3B that exhibits a detection surface parallel to the other YZ plane is set to one direction in the X-axis direction. Thereby, the number of reference coils (not shown) can be reduced to the minimum necessary, and the scale can be suppressed.
[0076]
Second embodiment
A second embodiment will be described with reference to FIG. Constituent elements that are the same as or equivalent to those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted or simplified.
[0077]
This embodiment is characterized by a dewar structure, and is a further development of the dewar structure of the first embodiment.
[0078]
The biomagnetism measuring apparatus according to this embodiment includes a dewar 66 that is substantially U-shaped as an overall shape. The U-shaped dewar 66 is divided into a vertical dewar 66S facing the chest side of the subject P, an upper lateral dewar 66U facing the front of the chest, and a lower lateral dewar 66L. It has become.
[0079]
These divided dewars 66S, 66U, 66L are coupled in a substantially U-shape as shown in the figure via connecting members 62. At this time, the longitudinal dewar 66S faces the left side of the chest of the subject P, and the upper lateral dewar 66U and the lower lateral dewar 66L face the front and back surfaces of the subject P, respectively. So that it is positioned. That is, the three dewars can face the heart of the subject P from three directions. The substantially U-shaped dewar 66 is fixed and suspended on an arm 64 through a connecting member 62 as shown in the figure.
[0080]
Further, in order to facilitate access to the subject P of the Dewar 66, the top plate 1N of the bed 1 is formed in a U (U) shape opposite to the Dewar 66, and its lower part is attached to the bed base. It is. The opposite U-shaped structure achieves a retracting structure that allows the lower lateral dewar 66L to be positioned under the bed. For this reason, 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.
[0081]
Each of the divided dewars 66S, 66U, 66L is independent and has the same independent sensor structure and cooling structure as in the first embodiment described above, but the heat pipes 32S, 32U, 32L used in the three-part dewar are common. It is connected to the refrigerator 31. The refrigerator 31 is placed on the arm 64 for space saving.
[0082]
Note that the biomagnetic measuring apparatus according to the second embodiment is also implemented by selecting an appropriate arrangement pattern of the above-described SQUID sensor.
[0083]
As described above, the U-shaped dewar 66 is constituted by three planar (plate-shaped) divided dewars 66S, 66U, 66L, and the bed 1 is structured to be accessible by the divided dewar 66L. In addition, not only the chest side surface and the chest front surface of the subject P but also the back surface can be measured simultaneously, and from the viewpoint of further enrichment of detection data, the same effects as described above can be obtained. Moreover, since it is a separate structure, the entire dewar can be made a simple structure as in the first embodiment, which can contribute to a reduction in manufacturing cost and maintenance cost.
[0084]
Naturally, the simultaneous change in the arrangement density and coil area of the SQUID sensor 21 or the change in only the arrangement density of the SQUID sensor 21 obtained in the first embodiment (ie, this corresponds to the curved portion of the entire dewar 66). The sensor arrangement density is increased and the coil area is reduced or only the sensor arrangement density is increased toward the butt side of the divided dewars 66S and 66U and / or closer to the butt side of the divided dewars 66S and 66L. The effect resulting from doing is also acquired.
[0085]
In each of the above-described embodiments and variations thereof, the case where the subject's magnetic measurement site is the heart has been described. However, this measurement site is not necessarily limited to the heart. Part.
[0086]
Further, the dewar is only required to have a detection surface shape that matches the body surface shape of the measurement site as much as possible, and is not necessarily limited to the above-described L-shape or U-shape. These L-shaped and U-shaped can be formed into a deformed curved shape.
[0087]
【The invention's effect】
As described above, according to the biomagnetic measurement apparatus of the present invention, the arrangement pattern (sensor arrangement density, coil area) when arranging a plurality of magnetic sensors formed by SQUID sensors or the like in the dewar is, for example, Since it is configured to change as it reaches the curved detection surface (curved part) of the L-shaped dewar (at least increase the sensor arrangement density), depending on the type of measurement target, such as adults and children, young and old, men and women, Even if the size of the measurement site of the subject changes due to the difference, these various subjects can be covered with a single device, and accurate and stable magnetic measurement can always be performed. In particular, such an effect becomes remarkable when the measurement site is the heart (chest).
[0088]
  Further, according to the biomagnetic measuring device of the present invention, in addition to the arrangement of the magnetic sensor having the above-described configuration, the dewar is, for example, L-shaped (or substantially L-shaped) or U-shaped (U). Since it is formed in a shape (substantially U-shaped), the above-mentioned effects are obtained, and at the same time, as many magnetic signals as possible from the measurement site of the subject are detected as many as possible.ratioTo improve the measurement accuracy (that is, the estimation accuracy of the magnetic field source). In particular, since the heart is generally located to the left of the center of the chest, at least the left chest side (part) can be added to the measurement range to increase this effect.
[Brief description of the drawings]
FIG. 1 is a configuration diagram schematically showing an overall structure centered on an L-shaped dewar of a biomagnetic measurement 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 diagram for explaining an arrangement pattern of SQUID sensors arranged in an L-order dewar.
FIG. 4 is a diagram illustrating a schematic structure of a first-order differential type SQUID sensor.
FIG. 5 is an explanatory diagram for explaining the principle of a heat pipe.
FIG. 6 is a partial cross-sectional view for explaining an arrangement state of an L-shaped dewar heat pipe and a SQUID sensor.
FIG. 7 is an explanatory view showing an example of attachment of a SQUID sensor.
FIG. 8 is a diagram schematically showing an example of an arrangement pattern of SQUID sensors.
FIG. 9 is a diagram schematically showing another example of an arrangement pattern of SQUID sensors.
FIG. 10 is a diagram schematically showing still another example of an arrangement pattern of SQUID sensors.
FIG. 11 is a diagram for explaining a method for arranging SQUID sensors in which differential directions are aligned for each detection surface;
FIG. 12 is a configuration diagram showing an overall structure centering on a U-shaped dewar structure of a biomagnetic measurement device according to a second embodiment of the present invention.
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]
1 sleeper
1N top plate
2 Sensor part
3 L-shaped dewar
3U upper cover
3L lower cover
4 pedestal
5 Drive and processing unit
6 Cooling mechanism
11a, 11b Outer and 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 Insulation
58 Thermal conductor
62 Connecting member
63 prop
64 arms
66 U-shaped dewar
66S, 66U, 66L Split dewars that form U-shaped dewars

Claims (9)

In a biomagnetism measuring apparatus comprising a plurality of magnetic sensors for detecting a magnetic signal of a subject and a dewar that houses the magnetic sensors,
The dewar has a plurality of detection surfaces spatially positioned around the body surface of the subject , and is formed into a shape having a flat portion at least in part of the detection surfaces ,
The biomagnetism measuring apparatus, wherein the plurality of magnetic sensors are arranged in the dewar so that at least the arrangement interval between the sensors is reduced in the vicinity of the end portion of the detection surface and the sensor arrangement density is increased . In the invention of claim 1,
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, and these two detection surfaces cover the front and side surfaces of the left chest of the subject. A biomagnetism measuring device arranged so as to cover. In the invention of claim 2,
The dewar has a curved detection surface that continuously curves and connects the two detection surfaces, and the magnetic sensor is disposed along the curved detection surface, and the curved detection surface is The biomagnetism measuring apparatus, wherein the dewar is arranged so as to cover a body surface between a front surface and a side surface of the left chest of the subject. In the invention of claim 3,
The biomagnetic measuring device, wherein the plurality of magnetic sensors are arranged so that a mutual arrangement interval becomes narrower toward the curved detection surface and a sensor arrangement density is increased. In the invention of claim 3,
The biomagnetic measuring apparatus, wherein the plurality of magnetic sensors are arranged such that only the arrangement interval between the plurality of magnetic sensors reaches the curved detection surface so as to increase the sensor arrangement density. In the invention of claim 1,
The dewar has a shape in which at least three detection surfaces are substantially U-shaped or substantially U-shaped when viewed from the body axis direction of the subject, and the at least three detection surfaces are located on the left side of the subject. A biomagnetism measuring device arranged to cover at least the front, side, and back of the chest. In the invention of claim 1,
Each of the plurality of magnetic sensors is formed by a SQUID sensor having a differential direction, and the plurality of SQUID sensors are arranged so that the differential directions thereof are directed in the same direction on each of the detection surfaces. . In the invention of claim 1,
While the magnetic sensor is composed of a SQUID sensor, a cooling source disposed outside the dewar, and a cooling source disposed inside the dewar connected to the cooling source and cooling the plurality of SQUID sensors. A biomagnetism measuring device comprising a cooling means. In the invention of claim 8,
The biomagnetism measuring apparatus, wherein the cooling source is a refrigerator, and the cooling means is a heat pipe connected to the refrigerator.

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