JP5712640B2 - Magnetic measuring device and biomagnetic measuring method - Google Patents

Description

  The present invention relates to an apparatus and a method for magnetic measurement of a living body represented by magnetoencephalography.

  Conventionally, in biomagnetic measurements represented by the above-mentioned magnetoencephalography, a SQUID (Superconducting Quantum Interference Device), which is a highly sensitive magnetic sensor that detects a weak magnetic field, has been used. The rough measurement mechanism is that when superconductors with different phases are joined via a barrier layer (Josephson junction), a tunnel current flows between the superconductors, and the tunnel current is a magnetic flux penetrating the junction surface. It uses the Fraunhofer-type quantum interference effect, which is weakened when is an integral multiple of the flux quantum and strengthened at other times. Such a property is called the Josephson effect, and a device in which one or more Josephson junctions are connected by a superconducting loop is called the SQUID.

  Most of the SQUID elements currently in practical use are made of niobium (Nb), and in order to work as a SQUID element, it is necessary to make this niobium into a superconducting state as described above. Since the superconducting transition temperature is 9.2K, cooling with liquid helium is required. Therefore, in actual measurement, liquid helium is circulated through the pot and cooled to a low temperature of about 10K, while a large number of the SQUID elements are arranged and fixed in the concave surface at the bottom of the pot. The subject's head is put in for measurement.

  Patent documents 1-5 etc. are proposed as such a SQUID sensor and a magnetoencephalography measuring device using the same. In particular, as shown in Patent Document 1, SQUID is cooled by liquid helium, so there are many incidental facilities other than a magnetic sensor such as a refrigerator, the apparatus is expensive, the space is bulky, and expensive helium gas There is a problem that the running cost is very high because the water is consumed by transpiration. In addition, when the Josephson element fails, the maintenance burden is heavy, such as the need to remove the liquid helium once.

  In addition, the structure of the sensor portion is not a structure that flexibly follows the subject's head, but is simply a structure in which the head is put into a hard concave surface portion, so that the scalp and the concave surface cannot be in close contact with each other, and a gap is generated. Moreover, even if the head is in close contact with the concave surface, the heat insulation layer has a thickness of 3 to 4 cm for heat insulation between the cooled sensor and the head, and the SQUID sensor is separated from the site to be inspected accordingly. Therefore, although the SQUID sensor alone is high in magnetic field sensitivity, the SQUID sensor is arranged away from the region to be inspected, so the magnetic field entering the sensor becomes weak, and adjacent magnetic fields intersect to form one SQUID. Since it is input, there is a problem that the position resolution in measurement is greatly reduced. In addition, if the posture changes for each measurement or if there is body movement during measurement, the positional relationship between the brain and the SQUID sensor changes, causing a large measurement error. There is also.

  On the other hand, Non-Patent Document 1 shows an example of an electrocardiogram measurement using an MI (magnetic impedance) element capable of performing weak magnetic measurement at room temperature. When such a method is used, it is not necessary to cool the sensor, so there is no restriction such as SQUID, and these elements can be brought into close contact with the human body directly. Close contact avoids misalignment, improves position resolution, and eliminates the need for a heat insulating layer, enabling close-up measurements and more positional resolution before adjacent magnetic fields intersect. Measurement with a high magnetic field and a strong magnetic field is also possible. In this way, an improvement in the resolution of the measuring device can be achieved.

JP 2000-193364 A JP 2004-65605 A JP 2007-17248 A JP-A-2-40578 Japanese Patent Laid-Open No. 3-1839

“A Measurement of Magnetocardiogram (MCG) by Planar Type Sensor using CoNbZr FILM” Y.Ohtomo, S. Yabukami, K. Kato, T. Ozwa and I, Arai (Journal of Magnetics Society of Japan Vol.33, No.3, 2009)

  However, in the above-described prior art, although the magnetic sensor has improved adhesion to the living body, the plurality of magnetic sensors are not fixed sensors as in the SQUID, and are attached to the living body at every measurement. There is a problem that it is not always possible to deposit at the same position exactly every time. Therefore, if a deviation occurs in the positional relationship between the magnetic sensors, a large influence (error) is given when the magnetic generation source is specified.

  That is, for example, as shown in FIG. 19A, when one magnetic generation source 501 is detected by two sensor units 502 and 503, the attachment positions of the sensor units 502 and 503 are deviated from the prescribed positions. Then, as shown in FIG. 19B, the individual magnetism generation sources 501a and 501b, that is, one of them is caught like a ghost. The sensor units 502 and 503 include a large number of magnetic sensors 504 arranged in an array.

  Specifically, since the magnetic sensor is three-dimensionally arranged in each direction of the subject's head, not only the signal distribution from the vicinity of the scalp to which each magnetic sensor is attached, but also a signal coming from a deeper position. If the positional relationship of the magnetic sensor is detected incorrectly, the magnetic measurement results include the depth direction, the position of the magnetic source 501 is erroneously derived, and the analysis result is incorrect as the ghost. Cause. Even if the depth direction of the magnetic generation source 501 is shallow, when analyzing magnetic signals from directions other than the direction directly below the magnetic sensor, there is an erroneous analysis result if there is no position information.

  An object of the present invention is to provide a magnetic measurement device and a biomagnetic measurement method capable of suppressing the generation of a ghost due to a positional deviation of a magnetic sensor and performing highly accurate magnetic analysis.

The magnetic measurement device of the present invention measures a relative positional relationship between a plurality of magnetic sensors that are attached to a measurement target and whose positions between the magnetic sensors are not fixed, and each of the magnetic sensors attached to the measurement target. And a weak magnetic field generated in the measurement object by performing magnetic field analysis on the measurement result of each magnetic sensor based on the relative positional relationship between the three-dimensional measurement device and each magnetic sensor obtained by the three-dimensional measurement device. A measuring device main body that collects information about current, wherein the magnetic sensor is a magnetic sensor that uses a ferromagnetic material and has a pair of magnetic detection elements that are equal to each other and an output end. The elements are arranged spaced apart from each other in the direction of the detected magnetic flux such that the direction of the easy axis of magnetization is perpendicular to the detected magnetic flux and the mutual easy axes of magnetization are orthogonal to each other, and the output end is Pair of magnetism Wherein the output obtained a difference between the detection result of the device.

  According to said structure, in order to collect the information regarding the weak electric current which generate | occur | produced in measurement objects, such as a biological body, the said magnetic sensor has a TMR (tunnel magnetoresistive) element, a GMR (giant magnetoresistive) element, or A magnetic sensor capable of measuring a magnetic field due to the weak current is used without cooling or simple cooling of an MI (magnetic impedance) element or the like, and a plurality of the magnetic sensors are attached to the measurement object. By performing magnetic field analysis on the measurement result of the magnetic sensor, information (distribution status of the generation source of the magnetic field (weak current)) regarding the weak current generated in the measurement target is collected (drawn).

  And before or after the magnetic measurement, the relative positional relationship between the magnetic sensors attached to the measurement object is measured by the three-dimensional measuring device, and the relative position between the magnetic sensors obtained by the three-dimensional measuring device. Based on the relationship, the magnetic sensor analyzes the measurement results of the magnetic sensors.

As a result, for example, in the magnetoencephalogram or magnetocardiogram obtained as an analysis result when the measurement target is a living body, it is possible to suppress the generation of a ghost due to displacement and perform a highly accurate analysis.
Further, in a magnetic sensor for measuring a weak magnetic flux caused by a weak current generated in a living body, a ferromagnetic material such as a TMR (tunnel magnetoresistance) element or an MI (magnetic impedance) element that can be measured in a normal temperature range. Two magnetic detection elements using are used in pairs. The two magnetic detection elements are stacked with a gap therebetween in the direction of the detected magnetic flux (in the case of a living body, the direction away from the surface of the living body), and the direction of the easy magnetization axis is substantially orthogonal to the detected magnetic flux. And are arranged so that their easy magnetization axes are orthogonal to each other. That is, in the case of a living body, the detected magnetic flux generated inside the living body is radiated to the outside substantially perpendicular to the surface of the living body, and the easy axis of magnetization of the magnetic detection element is provided parallel to the surface of the living body. become. However, the easy magnetization axes of the two magnetic detection elements are provided so as to be orthogonal to each other in a plane parallel to the biological surface. On the other hand, as the output of the magnetic sensor, the difference between the detection results of the two magnetic detection elements is taken.
Here, the detection magnetic flux generated by the weak magnetic flux source such as the living body forms a magnetic flux loop at a position relatively close to the surface, and the magnetic detection element relatively close to the surface passes through. The ratio of the magnetic flux passing through the relatively far magnetic detecting element is reduced by the loop. On the other hand, a relatively large magnetic flux (noise) due to an environment outside the living body such as geomagnetism and environmental magnetic field passes through the two magnetic detection elements almost in common. Therefore, by taking the difference between the detection results of the two magnetic detection elements, it is possible to efficiently reduce the environmental magnetic field (noise) at the first input stage and improve the SN ratio. Thus, the magnetic sensor including the room temperature magnetic detection element using the ferromagnetic material can measure a weak magnetic flux with low cost and high sensitivity. Further, the shielding of the external magnetic field can be eliminated or simplified, and the cost and space can be significantly reduced as compared with the configuration in which the entire room is magnetically shielded such as the SQUID.

  In the magnetic measurement device of the present invention, the magnetoencephalogram or magnetocardiogram is created by using the measurement object as a living body. The apparatus further includes a tomographic apparatus that captures a three-dimensional tomographic image of the living body, and the measurement apparatus main body is obtained by the feature points in the three-dimensional tomographic image obtained by the tomographic apparatus and the three-dimensional measurement apparatus. By matching the obtained feature points, the information on the weak current obtained by the measurement apparatus main body is synthesized with the three-dimensional tomographic image obtained by the tomography apparatus.

Furthermore, the biomagnetic measurement method of the present invention is a biomagnetic measurement method that collects information on a weak current generated in a living body, and takes a three-dimensional tomographic image of the living body with a tomographic apparatus, and features from the captured image. A step of detecting a point; a step of detecting a magnetic field due to the weak current; and a step of attaching a plurality of magnetic sensors whose positions between the magnetic sensors are not fixed to the living body; A step of measuring the relative positional relationship and the feature points between the magnetic sensors deposited; a step of detecting the magnetic field by the magnetic sensors; and a relative relationship between the magnetic sensors obtained by the three-dimensional measuring device. Based on the positional relationship, the measuring device main body analyzes the measurement result of each magnetic sensor by magnetic field analysis, and thereby information on the weak current generated in the living body. The measuring device main body matches the feature point in the three-dimensional tomographic image obtained by the tomography device with the feature point obtained by the three-dimensional measuring device by the collecting step. information relating to the weak current obtained by viewing including the step of combining the three-dimensional tomographic image obtained by the tomograph, the magnetic sensor of a ferromagnetic material, mutually equal pair of magnetic detection A magnetic sensor having an element and an output end, wherein the pair of magnetic detection elements are arranged so that the direction of the easy axis of magnetization is perpendicular to the detected magnetic flux and the easy axes of magnetization are perpendicular to each other. The detection magnetic fluxes are arranged to be spaced apart from each other in the direction of the detection magnetic flux, and the output end obtains a difference between detection results of the pair of magnetic detection elements .

  According to the above configuration, for example, when the measurement site is the brain, in order to know the actual state of the brain, it is required to measure the spatial resolution with an accuracy of 3 mm. In order to achieve this accuracy, However, it is necessary to use actual subject information (three-dimensional tomographic image) using CT scan or MRI instead of analysis based on a so-called standard brain model. Therefore, the tomography device measures the actual brain model of the subject, and on the model, a characteristic point of the human body such as an eyeball and an ear hole, or a marker artificially attached to the living body, etc. In the three-dimensional measurement apparatus, the feature points are extracted from the three-dimensional image by image analysis or the like, and the feature points are associated with the tomography in the measurement apparatus body. Information related to the weak current obtained from the three-dimensional measurement device to the measurement device main body is synthesized with a three-dimensional tomographic image of a living body by the device.

  With this configuration, in addition to the relative positional relationship between the magnetic sensors, the relative positional relationship between the living body and the magnetic sensor, for example, the spatial position information of the magnetic sensor with respect to the brain model can be accurately measured. In addition, high-definition magnetic measurement can be made possible. This is particularly effective in the case of magnetoencephalography measurement, because the shape of the brain is also important when assigning functions.

  In the magnetic measuring device of the present invention, the plurality of magnetic sensors are mounted on a support member made of a flexible material.

  According to the above configuration, since the plurality (large number) of magnetic sensors are collectively mounted on the support member, it is possible to facilitate the attachment to the subject, and the positional relationship between the magnetic sensors is as follows: It can be kept constant to some extent. However, if the support member is formed of a flexible material so as to improve the familiarity with the surface of the living body, the magnetic sensor supported by the support member does not always maintain the same positional relationship. There is a possibility that the exact positional relationship of each time is shifted every measurement. Therefore, it is effective to measure the relative positional relationship as described above.

In the magnetic measurement device of the present invention, the magnetic sensor is any one of a tunnel magnetoresistive element, a giant magnetoresistive element, and a magnetoimpedance element .

  Furthermore, in the magnetic measuring device of the present invention, the support member is a cylindrical body that covers the body.

  According to said structure, the measurement object can be made into a heart or a fetus, and the said magnetocardiogram can be created as an analysis result, for example.

  In the magnetic measurement device of the present invention, the timing of signal acquisition from the magnetic sensor by the measurement device main body is the same-phase timing in the heartbeat cycle.

  According to said structure, the function of the effect | action of the pump which sends out the blood flow of the heart is acquired by changing own magnitude | size and a position periodically. For this reason, when creating a magnetic image (the magnetocardiogram), the timing is specified at an arbitrary timing in the heart's motion cycle, such as the timing at which the heart is most expanded, contracted, or arbitrarily offset from those timings. And an accurate said magnetic image can be acquired by measuring at the same timing each time.

  Furthermore, the magnetic measurement device of the present invention is characterized by further comprising a covering member that covers the magnetic sensor attached to the living body and shields it from an external magnetic field.

  According to the above configuration, when performing magnetic measurement by providing a plurality of magnetic sensors capable of performing weak magnetic measurement in a normal temperature range without performing cooling with liquefied gas as described above, Is provided with a covering member so as to cover the magnetic sensor attached to the living body, and shields the magnetic sensor and the measured part from an external magnetic field.

  With this configuration, the entire room such as SQUID, which is a conventional measurement apparatus for weak current in a living body, is not magnetically shielded, but only the periphery of the measured part is shielded. And the degree of freedom in measurement can be improved.

  The magnetic measurement apparatus and biomagnetic measurement method of the present invention can suppress the generation of ghosts due to displacement and perform highly accurate analysis.

It is a figure which shows typically the use condition of the biomagnetic measuring device which concerns on the 1st Embodiment of this invention. It is a perspective view which shows arrangement | positioning of the magnetic sensor element by which the three-dimensional position measurement was carried out by the three-dimensional measuring apparatus in the said biomagnetic measuring device. It is the figure which synthesize | combined the head model in FIG. It is a figure which shows an example of the measurement result in FIG. It is a block diagram which shows the electrical structure of the said biomagnetic measuring device. FIG. 6 is a block diagram illustrating an electrical configuration of an interface in FIG. 5. FIG. 6 is a block diagram showing an electrical configuration of the sensor platform board in FIG. 5. It is a figure for demonstrating the identification method of the generation source of the magnetic field by the weak electric current by the arithmetic unit which guides a measurement result as shown in FIG. It is a figure for demonstrating rotation of the easy magnetization axis | shaft in a tunnel magnetoresistive element. It is a perspective view which shows the specific structure of 1 element of the magnetic sensor element which concerns on this invention. It is a figure which shows the structure at the time of applying the magnetic sensor element shown in FIG. 10 to an actual magnetic sensor. It is a flowchart for demonstrating the measuring method of the said biomagnetic measuring device. It is a front view which shows typically the use condition of the biomagnetism measuring device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows typically the use condition of the biomagnetic measuring device which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows typically the use condition of the biomagnetic measuring device which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the electrical constitution of the biomagnetism measuring device which concerns on the 4th Embodiment of this invention. It is a perspective view which superimposes and marks the marking position by the position marker used with the biomagnetic measuring device of FIG. 16 on the MRI image of a head. It is a flowchart for demonstrating the measuring method of the biomagnetic measuring device shown in FIG. It is a figure for demonstrating the ghost generation | occurrence | production mechanism by the sensor position shift which arises by biomagnetic measurement.

(Embodiment 1)
FIG. 1 is a diagram schematically showing a use state of the biomagnetic measurement device 1 according to the first embodiment of the present invention. The biomagnetism measuring apparatus 1 according to the present embodiment measures the magnetism emitted from the head 21 of the subject 2 and obtains a magnetoencephalogram. Specifically, this biomagnetic measuring apparatus 1 measures the magnetic field generated from the current that flows when the brain neurons are excited, for example, where the epileptic seizure occurs, and how far it can be excised by brain surgery It is used to determine etc.

  In the biomagnetic measurement device 1, the sensor unit 3 is put on the head 21 of the subject 2. The sensor unit 3 is made of a non-magnetic, flexible material, and is formed by mounting a number of sensor platform boards 32 side by side on a support member 31 formed in a so-called balaclava type. As a result, only by the subject 2 wearing the sensor unit 3, a large number of sensor platform boards 32 can be easily attached to the subject 2. A large number of sensor platform boards 32 are distributed at predetermined intervals on either the front or back surface of the support member 31 so that the inner surface of the support member 31 is pressed along the surface of the head 21. The sensor unit 3 is placed on the head 21 of the subject 2 so that the sensor surface of the sensor platform board 32 is along the surface of the head 21 at regular intervals (through contact or through the thickness of the support member 31). become.

  The sensor platform board 32 does not require cooling with a liquefied gas and can perform a weak magnetic measurement in a normal temperature range, a TMR (tunnel magnetoresistive) element, a GMR (giant magnetoresistive) element, or MI (magnetic impedance). It is an aggregate of various magnetic sensor elements such as elements. The term “magnetic sensor” in the claims refers to a single magnetic sensor element mounted on the sensor platform board 32. Hereinafter, as the magnetic sensor element, a tunnel magnetoresistive element or a magnetic impedance element, A tunnel magnetoresistive element is mainly used.

  The opening 33 of the eye 22 portion of the subject 2 in the support member 31 takes into account the mental influence of the subject 2 and the like, and may not be provided depending on circumstances such as the measurement site. In that case, it becomes possible to measure the magnetoencephalogram emitted from the face portion as well as the frontal region, the occipital region and the temporal region.

  In such a sensor unit 3, since the support member 31 is formed of a flexible material in order to improve the familiarity with the surface of the living body, the magnetic sensor element supported by the support member 31 does not always maintain the same positional relationship. Therefore, there is a possibility that the strict positional relationship between the magnetic sensor elements is shifted every measurement. Therefore, the positional relationship between the sensor platform boards 32 is measured by the three-dimensional measuring device 8 with the sensor unit 3 mounted on the head 21 of the subject 2.

  In the example of FIG. 1, the three-dimensional measuring device 8 exemplifies an optical three-dimensional measuring device using a plurality of stereo cameras 81. As the measurement method, as shown in FIG. 1, two or more stereos that surround the head 21 of the subject 2 to which the sensor unit 3 is attached and are arranged so that there is no leakage or concealed portion on each sensor platform board 32. Images are simultaneously captured by a camera group including the cameras 81, and the captured images are processed in each camera system and replaced with the three-dimensional information of the imaging target (each sensor platform board 32). Thereafter, the magnetic measurement result of each sensor platform board 32 performed before or after this position measurement is analyzed based on the position information of each sensor platform board 32 obtained as described above, and the magnetoencephalogram is created. Is done.

  FIG. 2 is a diagram of a magnetic sensor element whose three-dimensional position is measured by the three-dimensional measuring device 8. In FIG. 2, in order to avoid complication of the drawing, the magnetic sensor elements are greatly thinned out and the size per element is shown larger than the actual size. FIG. 2 shows only the relative positional relationship of the magnetic sensor elements and is difficult to imagine. FIG. 3 shows an example of superposition on the model of the head 21 of the subject 2. The actual shape of the head 21 cannot be measured in the shadow of the magnetic sensor element by the above-described three-dimensional optical measurement. However, FIG. 3 shows an image before the sensor unit 3 is mounted or after tomography described later. It is shown superimposed on. FIG. 4 shows a magnetoencephalogram obtained by combining the current source (affected part position) obtained from the magnetic field detected by the magnetic sensor element thus measured in three dimensions and the vector indicating the direction and magnitude in FIG. Show.

  FIG. 5 is a block diagram showing an electrical configuration of the biomagnetic measurement device 1 configured as described above. The biomagnetism measuring device 1 includes the sensor unit 3, the three-dimensional measuring device 8, an arithmetic device 5, and an interface 6. The arithmetic device 5 is composed of a personal computer or the like, and is connected to the sensor unit 3 via the interface 6 and to the three-dimensional measuring device 8. The sensor unit 3 and the interface 6 are connected by a cable 7. The sensor unit 3 can be moved within the reach of the cable 7, and the direction can be freely changed. The cable 7 includes a power line 71 and a signal line 72.

  FIG. 6 is a block diagram showing an electrical configuration of the interface 6. The interface 6 includes a PCI bus controller 61, a command conversion buffer controller 62, an SRAM 63, and a serial interface driver 64. The PCI bus controller 61 performs communication between the arithmetic device 5 and the command conversion buffer controller 62. The command conversion / buffer controller 62 transmits a command from the arithmetic unit 5 to each sensor unit 3, develops the measurement result transmitted from each sensor unit 3 as a serial signal, and writes it in the SRAM 63. At the same time, in response to a read request from the arithmetic device 5, the stored contents of the SRAM 63 are read and transmitted to the arithmetic device 5. The serial interface driver 64 performs communication between the command conversion / buffer controller 62 and each sensor platform board 32.

  FIG. 7 is a block diagram showing an electrical configuration of each sensor platform board 32. The sensor platform board 32 is electrically connected and mechanically fixed with TMR array modules 321, 321,... Including a plurality of TMR elements of several mm square arranged in an array. The sensor platform board 32 also includes a controller 322, a RAM 323, and amplification / conversion circuits 324, 324,. The amplification / conversion circuit 324 is provided for each TMR array module 321 and is connected to the TMR array module 321 on a one-to-one basis. The amplification / conversion circuit 324 includes an amplifier 324 a that amplifies the output signal from the TMR array module 321, and an A / D converter 324 b that converts the output of the amplifier 324 a into a digital signal and inputs the digital signal to the controller 322. The RAM 323 is a storage device that stores information input to the controller 322 and information calculated by the controller 322.

  The controller 322 receives a command from the arithmetic unit 5 and starts measurement, operates the TMR array module 321, sequentially takes the output signal through the amplification / conversion circuit 324, and stores it in the RAM 323. Thereafter, the controller 322 alternatively outputs the output signal of the TMR array module 321 to a predetermined timing at an appropriate timing (in response to polling from the arithmetic unit 5 or at a time predetermined for each controller 322). Is transmitted to the arithmetic unit 5 through the signal line 72 by serial communication in the format of.

  The arithmetic device 5 which is a measuring device main body collects information on the weak current generated in the living body, for example, information such as a position and a size flowing from the generation position, from the output signal of each TMR array module 321. However, the relative positional relationship of each sensor platform board 32 is measured in advance for each sensor platform board 32 by the three-dimensional measuring device 8, and the position of each TMR element from each TMR array module 321 in each sensor platform board 32 is , Which can be recognized from the arrangement of modules and arrays, and these pieces of information are recognized by the arithmetic unit 5.

  In the three-dimensional measuring apparatus 8, the images captured by the stereo cameras 81 are converted into digital information through the I / F 82 and sent to the position measuring unit 83. In the position measurement unit 83, first, the feature point extraction unit 831 specifies the position in the image of each sensor platform board 32 from each captured image, and then the position measurement unit 832 determines the amount of positional deviation between the images. Position information is determined based on the triangle method, and each spatial position information is determined. A method for creating such spatial position information is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-90583.

  The positional relationship between the stereo cameras 81 is fixed, and the positional relationship is separately measured and stored in the positional information integration unit 841 of the synthesis unit 84. In this way, the information obtained by each stereo camera 81 is sent from the position measurement unit 832 to the feature point matching unit 842 of the synthesis unit 84, and is arranged for each feature point, and then the information is obtained by the position information integration unit 841. Are combined and integrated as position information of each sensor platform board 32 and sent to the arithmetic unit 5.

  FIG. 8 is a diagram for explaining a method of specifying a magnetic field generation source caused by a weak current by the arithmetic unit 5. As described above, the relative positional relationship between the tunnel magnetoresistive elements is recognized in advance. In FIG. 8, the recognized tunnel magnetoresistive elements are referred to as sensors Pa and Pb. Thus, the method of performing analysis by reflecting the position of the sensor utilizes the fact that the signal intensity attenuates in inverse proportion to the square of the distance. That is, in this analysis method, if the signals of the two sensors that have received the strongest signal among the magnetic signals simultaneously received by a large number of sensors and the position of the received sensor are identified, the intensity of the pulse is 2 of the distance. Since it attenuates in inverse proportion to the power, the ratio of the distances from the two sensors is used to be the reciprocal of the square root of the signal intensity. Therefore, the magnetic field generation source P exists somewhere in the Apollonius circle R defined by the ratio of the reciprocal of the square root of the signal intensities Sa and Sb from the two points of the sensors Pa and Pb.

Since the circle R is precisely a space, it is the surface of a sphere of a rotating body with two points connecting the sensors Pa and Pb as rotation axes. For example, for simplicity, the coordinates of one sensor Pa are a (0, 0, 0), the coordinates of the other sensor Pb are b (0, d, 0), and the signal strengths are Sa and Sb, respectively. If the ratio of the reciprocals of the square roots of the signal intensities Sa and Sb is k (= (Sa / Sb) ^0.5 ), the center is (0, d / (1-k ² ), 0), and the radius | (d ² + K ² ) ^0.5 / (1−k ² ) |

Furthermore, generally, when the coordinates of the sensors Pa and Pb are (xa, ya, za) and (xb, yb, zb), respectively, the center is ((−k ² xa + xb) / 1−k ² , (−k ² ya + yb) / 1−k ² , (−k ² za + zb) / 1−k ² ). The radius d is set to d = ((xa−xb) ² + (ya−yb) ² + (za−zb) ² ) ^0.5 , so that | (d ² + k ² ) ^0.5 / (1− k ² ) |.

  In this way, by preparing three spheres that can be considered as the signal source P and obtaining points that contact each sphere, the signal source can be specified. The sensors used for obtaining the three spheres are, for example, the sensors that received the strongest three signals among the magnetic signals received at the same time, and among these three sensors, three sets obtained from a combination of two sensors. Use information. At this time, it may appear that there is a source outside the object to be measured, but it is removed. More specifically, the position accuracy can be improved by obtaining a large number of spheres from the positions and signal strengths of various two sets of sensors and capturing the points where the intersections of the sphere surfaces are concentrated as magnetic sources. .

  In actual biomagnetism measurement, power is first applied to the entire biomagnetism measuring apparatus 1, and current is also applied to each magnetic sensor array module 321. Thus, an output signal is derived from each magnetic sensor element in the magnetic sensor array module 321 under the influence of the magnetic flux generated from the head 21 of the subject 2. Next, a measurement execution command is input to the arithmetic device 5 by the operator. Then, the arithmetic device 5 sends a measurement execution command to the n sensor platform boards 32. In each sensor platform board 32, the controller 322 receives a measurement execution command. The controller 322 receives the digitized output signal from each magnetic sensor array module 321 via the amplification / conversion circuit 324, and links this to the information specifying the address information of each magnetic sensor array module 321. Is sent to the arithmetic unit 5 as biomagnetic measurement information. The arithmetic device 5 analyzes biomagnetic measurement information from each controller 322, calculates a magnetoencephalogram comprising a combination of the position on the head 21 of the subject 2 and the strength and direction of the magnetic field, and converts it into image information. To the display device 51.

  The measurement execution command may be one in which the arithmetic device 5 executes measurement each time a command is input, or may be composed of a measurement start command and a measurement end command. In that case, the arithmetic unit 5 may perform measurement at a constant time rate during the period between the measurement start command and the measurement end command, and display a magnetoencephalogram or magnetocardiogram that changes in real time on the display device 51. It is valid. In addition, biomagnetic measurement information, magnetoencephalogram and magnetocardiogram information, and image information generated for display are recorded so as to be readable from the arithmetic unit 5, and can be displayed and reproduced on the display unit 51. It is preferable to keep it.

  On the other hand, as described above, a magnetic impedance element or a tunnel magnetoresistive element can be used as the magnetic sensor of the present embodiment. In the detection principle, a ferromagnetic material is used, the external magnetic field is converged in the material to increase the magnetic flux density, and the phenomenon that the easy magnetization axis of the ferromagnetic material rotates as described in detail below. Basic. The aforementioned Non-Patent Document 1 is an application example of the magneto-impedance element to living body magnetic measurement, but does not have the above-described features of the present embodiment.

  First, the rotation of the easy axis will be described. As shown in FIG. 10, the ferromagnetic material 101 such as amorphous metal (CoNbZr) is formed by sputtering or the like as shown in FIG. 10 (in FIG. 9, the substrate used for film formation is peeled off). However, when heated and cooled in the magnetic field 104, the magnetic easy axes 102 and 103 can be set with the same magnetic moment. When the easy magnetization axes 102 and 103 are arranged in a direction orthogonal to the external magnetic field B to be detected, the easy magnetization axes rotate in the direction along the external magnetic field B as indicated by reference numerals 102 ′ and 103 ′. .

  Due to this phenomenon, in the magnetic impedance type element, the external magnetic field B is detected from the change in circuit impedance due to the change in magnetic permeability of the magnetic field generated in the high-frequency current I. FIG. 9 shows a system in which a high-frequency current I is passed through the ferromagnetic material 101, but there is also a system in which a ferromagnetic thin film is insulated and pasted on the circuit separately from the high-frequency circuit. In this case as well, a weak external magnetic field B is detected as the induced electromotive force changes and the high-frequency current fluctuates due to rotation of the easy magnetization axes 102 and 103 of the ferromagnetic body 101 by the external magnetic field B. In addition, the impedance change is detected not by directly measuring the impedance but by detecting the phase shift of the high-frequency current I in a heterodyne manner, thereby improving the detection sensitivity. In either case, the sensitivity is highest when the easy magnetization axes 102 and 103 are arranged in a direction orthogonal to the external magnetic field B and the external magnetic field B is detected.

  A tunnel magnetoresistive element is formed by laminating a ferromagnetic material with a fixed magnetization direction on a ferromagnetic material having an easy axis of magnetization through an insulating layer with a thickness of several nanometers such as magnesium oxide and alumina. When a voltage is applied between the ferromagnets, the tunnel current passing through the insulating layer varies greatly according to the angle formed by the magnetization fixed axis and the easy magnetization axis, and a minute external magnetic field can be detected by this current. Regarding the angle formed between the easy axis and the fixed axis, the tunnel current is the largest when the two directions coincide with each other, and the tunnel current is the smallest when the directions are opposite to each other. The tunnel current changes. Therefore, when the direction of the easy magnetization axis is orthogonal to the fixed magnetization axis, it can be understood with the highest sensitivity as the change in the tunnel current. In these magneto-impedance element and tunnel magneto-resistive element, the cross section of the ferromagnetic material having a plate-like shape serves as an opening of the transmitted magnetic flux.

  However, although room temperature magnetic detection elements using these ferromagnetic materials are small and have high sensitivity, they do not reach detection sensitivity as high as SQUID. It cannot be used for detection. Therefore, reducing noise such as geomagnetism and environmental magnetic field is particularly important for relatively increasing detection sensitivity, and a device for reducing noise is inevitable in actual use. Therefore, a method for removing an external noise magnetic field in the room temperature and high sensitivity magnetic detection element of the present embodiment will be described in detail below.

  FIG. 10 is a perspective view showing a configuration of one element of the magnetic sensor element in the case of the tunnel magnetoresistive element or the magnetoimpedance element. The magnetic sensor element according to the present embodiment uses a pair of mutually equivalent magnetic detection elements 301 and 302 having a ferromagnetic material, and the pair of magnetic detection elements 301 and 302 is parallel to the detection magnetic flux B and further easily magnetized. The axes 3011 and 3021 are arranged at intervals in the direction of the detected magnetic flux B so that the directions of the easy magnetic axes 3011 and 3021 are orthogonal to the detected magnetic flux B. Furthermore, the fixed magnetization axes 3012 and 3022 are orthogonal to the easy magnetization axes 3011 and 3021 in order to detect the detected magnetic flux B with the highest sensitivity, that is, the fixed magnetization axes 3012 and 3022 are detected magnetic flux B. Are provided in parallel. In FIG. 10, the directions of the magnetization fixed axes 3012 and 3022 are opposite to each other, but may be the same direction.

  In this way, the magnetic detection elements 301 and 302 are arranged substantially parallel to the detection magnetic flux B, and the magnetization fixed axes 3012 and 3022 are also arranged substantially parallel to the detection magnetic flux B. If there is an environmental magnetic field (external magnetic flux) BN that uniformly arrives, approximately equal numbers of magnetic fluxes (five in the figure) are input to the ferromagnetic bodies with fixed magnetization of both magnetic detection elements 301 and 302, respectively. Here, as described above, the directions of the magnetization fixed axes 3012 and 3022 coincide with each other, but the directions are reversed, so that the amount of change in the induced electromotive current and the tunnel current is reversed between the respective detection elements. It becomes the same size. Therefore, if two magnetic detection elements 301 and 302 are connected in series to the sensor output terminal and the outputs are added, the average resistance value becomes substantially constant and the output current hardly changes. If the directions of the magnetization fixed axes 3012 and 3022 are the same, current changes due to the external noise magnetic field BN of both the magnetic detection elements 301 and 302 appear in the same direction. In this case, the outputs of the magnetic detection elements 301 and 302 are the same. If the current difference is taken as the detection current, it becomes zero and the influence of the external noise magnetic field BN can be canceled.

  On the other hand, the signal magnetic flux BS to be detected is absorbed by the magnetic detection element 301 closer to the living body (9 in the figure) and diverges at the exit of the magnetic permeability path. Immediately after that, the magnetic detection element 302 far from the living body absorbs only a part of the diverged magnetic flux (one in the figure), so the output current between the magnetic detection elements 301 and 302 is large. Make a difference. Therefore, even if these additions are taken or differentials are taken, they can be detected as signal currents.

  The magnetic sensitivity can be maximized by arranging the magnetic flux input surfaces (magnetization fixed axes 3012 and 3022) perpendicularly between the magnetic detection elements 301 and 302. That is, in the magnetic detection element 302 far from the living body, the weak magnetic flux BS from the living body does not reach the portion that does not overlap the near magnetic detection element 301 because there is no member that forms a magnetic path, and the magnetic detection This is because a difference from the element 301 appears remarkably.

  With this configuration, the environmental magnetic field BN (noise) can be efficiently reduced at the first input stage to improve the SN ratio, and a weak magnetic flux BS can be measured with low cost and high sensitivity. Further, the shielding of the external magnetic field BN can be eliminated or simplified, and the cost and space can be significantly reduced as compared with the configuration in which the entire room is magnetically shielded such as the SQUID.

  Moreover, it is preferable that the space | interval of the detection magnetic flux B direction in the two magnetic detection elements 301 and 302 is 0.5-20 mm. This is because, when the magnetic detection elements 301 and 302 are tunnel magnetoresistive elements or magnetoimpedance elements, the detected magnetic flux B passes through the ferromagnetic material, so that it is attenuated compared to when passing through a vacuum such as SQUID. This is because the detected magnetic flux passing through the two magnetic detection elements 301 and 302 becomes substantially equal when the two magnetic detection elements 301 and 302 are too close to each other. Therefore, by setting the distance between the two magnetic detection elements 301 and 302 in the direction of the detection magnetic flux B to 0.5 to 20 mm, the magnetic detection elements 301 and 302 further Good sensitivity can be obtained.

  In this manner, tunnel magnetoresistive elements can be used as the magnetic detection elements 301 and 302 capable of performing weak magnetic measurement in a normal temperature range without performing cooling with a liquefied gas. By using the element, the structure can be simplified.

  And when the magnetic detection elements 301 and 302 using the tunnel magnetoresistive element or the magnetic impedance element are applied to the actual magnetic sensor element, as shown in FIG. The flexible support member 31 made of a non-magnetic material is laminated and embedded so as to be orthogonal to each other. A plurality of pairs of magnetic detection elements 301 and 302 of several mm square are appropriately combined to constitute the magnetic sensor array module 321.

  FIG. 12 is a flowchart for explaining a measurement method of the biomagnetic measurement apparatus 1 configured as described above. First, in step S <b> 1, the sensor unit 3 is placed on the head 21 of the subject 2, so that the sensor surfaces of the plurality of sensor platform boards 32 supported by the support member 31 are in close contact with the scalp. In step S <b> 2, the relative positional relationship between the sensor platform boards 32 attached to the head 21 of the subject 2 is measured by the three-dimensional measuring device 8. In step S3, magnetic field detection is performed by each magnetic sensor element. In step S4, based on the relative positional relationship of the magnetic sensor elements in each sensor platform board 32 obtained by the three-dimensional measurement apparatus 8, the arithmetic unit 5 calculates the measurement results of the magnetic sensor elements as described above. A magnetoencephalogram with a weak current generated in the head 21 is created by analyzing the magnetic field. The measurement of the positional relationship in step S2 is preferably performed before the magnetoencephalogram measurement in step S3 as described above. However, if the measurement method has no problem in terms of magnetic noise after the magnetoencephalogram measurement, It may be performed during the magnetic measurement.

  As described above, in the magnetic measurement device 1 of the present embodiment, in order to collect information on the weak current generated in the measurement target such as a living body, the magnetic sensor element includes, for example, a tunnel magnetoresistive element, a giant magnetoresistive element. A magnetic sensor element that can measure the magnetic field due to the weak current is used without cooling or simply cooling the element or the magnetic impedance element. Then, a plurality of the magnetic sensor elements are attached to the measurement object, and before or after the magnetic measurement, the relative positional relationship between the magnetic sensor elements is measured by the three-dimensional measuring device 8, and based on the obtained relative positional relationship. Then, the arithmetic unit 5 collects (draws) information on the weak current generated in the measurement target (distribution status of the generation source of the magnetic field (weak current)) by performing a magnetic field analysis on the measurement result of each magnetic sensor element. To do.

  By configuring in this way, even if a plurality of magnetic sensor elements are not fixed sensors like SQUID, and there is a possibility of positional deviation at every measurement, the deviation is accurately detected. Since the analysis can be performed, for example, in the magnetoencephalogram obtained as an analysis result when the measurement target is a living body, it is possible to suppress the generation of a ghost due to a positional shift and perform a highly accurate analysis.

(Embodiment 2)
FIG. 13: is a front view which shows typically the use condition of biomagnetic measuring device 1 'which concerns on the 2nd Embodiment of this invention. The biomagnetism measuring apparatus 1 ′ of the present embodiment measures magnetism emitted from the chest 26 and abdomen 27 of the subject 2. When the part to be measured is the chest part 26, the biomagnetic measurement device 1 ′ can measure the myoelectric potential (contraction pulse) of the heart 28 and confirm whether there is an abnormality in the operation of the heart 28. When the measurement target is the abdomen 27, the biomagnetism measuring device 1 'can measure the magnetic field generated from the heart of the pregnant woman's fetus at rest, knows the movement of the heart of the fetus, and can be used for prenatal examinations. Can be used, or spinal cord damage can be confirmed.

  Therefore, the sensor unit 3 ′ is configured by arranging a large number of sensor platform boards 32 at predetermined intervals on either the front or back surface of the belly-wrapped support member 31 ′ that is a cylindrical body that covers the trunk. The When measurement is performed by raising the upper body of the subject 2 such as sitting in a chair or standing, the support member 31 ′ is provided with a shoulder strap-like fixture 34 so as not to slide down. Thus, it is preferable to improve the adhesion with the living body. The configuration of the sensor unit 3 ′ is the same as that of the sensor unit 3 described above. In this way, a magnetocardiogram or the like can be created. In the measurement of the chest part 26 and the abdominal part 27, a sensor unit 3 ′ is simply formed by fixing a large number of sensor platform boards 32 on a plate and pressed against the chest part 26 or the abdominal part 27. You may make it stick.

  In such a biomagnetic measurement device 1 ′, a device 89 for detecting a heartbeat cycle is connected to the arithmetic device 5 in order to create the magnetocardiogram, and each sensor platform board 32 is connected to the arithmetic device 5 from the arithmetic device 5. It is preferable to provide a signal that defines the measurement timing. This is because the change in the magnetic field emitted from the heart 28 to be measured is weak and needs to be integrated, whereas the information from the measurement object with a large shape change like the heart 28 is integrated as it is. This is because the obtained image becomes an average value of signals in the respective sizes, and detailed image information cannot be obtained.

  Here, the function of the pump that sends the blood flow of the heart 28 is obtained by periodically changing its size and position, and in particular, the left ventricle that is working to send blood to the whole body is the maximum The normal value shows a change of 30 to 50% between the diastole and the minimum systole. However, when creating the magnetocardiogram, the arithmetic unit 5 can obtain information in a state of approximately the same size by capturing and integrating magnetic signals in synchronization with the heartbeat period of the heart 28, Clear image information can be obtained. The synchronization may be any timing in the operation cycle of the heart 28, such as the timing at which the heart 28 is most expanded, contracted, or arbitrarily offset from those timings. A magnetocardiogram can be created.

  Here, as a specific method of synchronizing the motion of the heart 28 and the magnetic image as described above, there are a method of synchronizing with an electrocardiogram signal, synchronizing with vertical movement of the skin near the heart 28, and the like. The propagation of the electrocardiogram is very fast, and no matter what position of the body is measured, an extreme phase shift does not occur with respect to the pulsation of the heart 28, which is preferable. In that case, the wiring for taking the electrocardiogram is likely to have an adverse effect on the magnetocardiogram measurement. Therefore, it is preferable to use the left arm or the left arm as shown in FIG. In addition to mechanically measuring the top and bottom of the skin, the measurement results can be adversely affected by taking measures that do not affect the magnetic field to be measured, such as light reflected by a laser displacement meter, sound reflection time, and phase shift. Can be avoided.

(Embodiment 3)
FIG. 14 and FIG. 15 are cross-sectional views schematically showing use states of the biomagnetic measurement devices 1a and 1a ′ according to the third embodiment of the present invention. These biomagnetism measuring devices 1a and 1a ′ are similar to the biomagnetism measuring devices 1 and 1 ′ described above, and can obtain a magnetoencephalogram and a magnetocardiogram, respectively. In the biomagnetic measuring devices 1a and 1a ′ according to the present embodiment, the sensor unit 3 and 3 ′ are mounted on the head 21 and the chest 26 of the subject 2 as described above, and the covering member 4 that performs magnetic shielding is provided. 4 'is mounted and measurement is executed. A magnetic shield chamber may be formed so as to surround the subject 2 in combination with the covering members 4 and 4 ′. However, the magnetic shield room in that case is not a large-scale one used for the above-described SQUID, and may be a simple one.

  The covering member 4 covers at least one of the cheek, the nose, the mouth, the eyes, the jaw, and the neck in addition to the forehead, the occipital region, and the temporal region. In the example of FIG. 14, it is assumed that the covering member 4 has a shape of a so-called full-face helmet (a protective cap worn to protect the head from an impact or the like) covering all of them. The eyes and mouth correspond to the openings 33 of the support 31 described above.

  On the other hand, corresponding to the sensor unit 3 ′, the covering member 4 ′ is formed in a cylindrical shape suitable for the chest part 26 and the abdominal part 27. The configuration of the remaining calculation device 5 and the like is the same as that of the biomagnetic measurement devices 1 and 1 'described above, and a description thereof is omitted. In particular, the sensor platform board 32 is lined on the covering member 4 '. The covering member 4 ′ is composed of an outer cylindrical body that performs magnetic shielding, and the cushioning inner body filled therein becomes the support body 31 ′. Further, the sensor unit 3 ′ is composed of two members 3a ′ and 3b ′. For example, as shown in FIG. 15, the sensor unit 3 ′ can be divided by a long diameter line of an elliptical cross section perpendicular to the axis, that is, before and after the subject 2. It has become. The two divided members 3a 'and 3b' may be connected at one end side by a hinge or the like and fastened at the other end side by a hook or the like, or both ends may be fastened by a hook or the like.

  Therefore, when the subject 2 wears these covering members 4 and 4 ′ as necessary, the covering members 4 and 4 ′ can more reliably block the disturbance magnetic flux BN and improve the measurement accuracy. Further, the covering members 4 and 4 'do not magnetically shield the entire room like the SQUID which is a conventional measurement apparatus for weak current in a living body, but shield only the periphery of the measured part. The cost can be remarkably reduced and the degree of freedom related to the measurement can be improved. Furthermore, when the measured part is the head 21, the covering member 4 has a so-called helmet shape, so that the subject 2 can perform magnetic shielding only by covering the covering member 4. The covering member 4 can be easily mounted. Further, like the covering member 4 ′ in FIG. 15, the sensor platform board 32 may be attached inside the covering member 4 in FIG. 14.

  As the covering members 4 and 4 ′, a shield covered with a material having high magnetic permeability such as permalloy or mu metal generally used is suitable. In the case of the permalloy, a thin layer is formed by casting, and a plurality of layers in which distortion is removed by annealing in a hydrogen atmosphere are laminated to form the covering members 4 and 4 ′. For this reason, the covering members 4 and 4 ′ are formed by assembling parts formed in a half-cracked state on the left and right or separated into the upper and lower sides into the helmet shape or the like by bonding or another support. Alternatively, instead of such a shield that is in close contact with a living body, a simple magnetic silence room may be formed, and then the subject 2 may be made to wear a detachable shield in the shape of a lion or a plate armor.

(Embodiment 4)
FIG. 16 is a block diagram showing an electrical configuration of a biomagnetic measurement apparatus 1 ″ according to the fourth embodiment of the present invention. This biomagnetism measuring apparatus 1 ″ is similar to the biomagnetism measuring apparatus 1 shown in FIG. 5 described above, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. In the biomagnetism measuring device 1 ″ of the present embodiment, a tomography device 9 is further connected to the arithmetic device 5 ″ that is the main body of the measuring device together with the three-dimensional measuring device 8 ″. The tomographic apparatus 9 is composed of CT, MRI, or the like that captures a three-dimensional tomographic image of a living body, and the arithmetic unit 5 '' includes feature points in the three-dimensional tomographic image obtained by the tomographic apparatus 9, By matching the feature points obtained by the three-dimensional measuring device 8 ″, the magnetoencephalogram obtained by the arithmetic device 5 ″ is combined with the three-dimensional tomographic image obtained by the tomography device 9. .

  For this reason, in the position measuring unit 83 ″ of the three-dimensional measuring apparatus 8 ″, the feature point extracting unit 831 ″ extracts each sensor platform board 32 from each captured image and also covers the sensor unit 3. Characteristic points of the human body that do not hide even when worn, such as eyeballs or ear holes, or markers that are consciously attached to the subject 2 are extracted, and the position measuring unit 832 determines the position of the position between the images. The positional information is determined from the deviation based on the triangle method. Also, the feature point matching unit 842 ″ of the synthesis unit 84 ″ organizes information for each of the feature points, and then the position information integration unit 841 synthesizes the information, and the position information of each sensor platform board 32. Are integrated and output to the arithmetic unit 5 ''.

  On the other hand, the tomography apparatus 9 can measure the positions of the sensor platform boards 32 and the feature points by capturing a three-dimensional tomographic image of the head 21. Thereby, the position measurement of each sensor platform board 32, that is, each magnetic sensor element and the living body can be performed. FIG. 17 shows the marking position by the position marker superimposed on the MRI image of the head 21.

  Then, as described above, the arithmetic device 5 ″ performs magnetic field analysis on the measurement results of the magnetic sensor elements based on the relative positional relationship between the magnetic sensor elements obtained by the three-dimensional measurement device 8 ″. After collecting (drawing) information on the weak current generated in the head 21 (distribution status of the generation source of the magnetic field (weak current)), the feature points in the three-dimensional tomographic image obtained by the tomography apparatus 9 The information about the weak current is combined with the three-dimensional tomographic image obtained by the tomography device 9 by matching the feature points obtained by the three-dimensional measuring device 8.

  Here, an approach of attaching a large number of sensors to the human body and observing the inside of the human body is performed by optical topography on the brain, EEG (Electroencephalogram) or the like. However, in general, the resolution obtained by these approaches is limited to the number of sensors to be attached, and the sensor interval is about several centimeters away. It was far from the required resolution of 3 mm, and there was no necessity to obtain sensor position information. Furthermore, in the case of optical topography, signals are scattered due to the influence of the brain and skull, resulting in a very blurred image.

  On the other hand, magnetic sensor elements that can be measured without cooling or only with simple cooling, such as tunnel magnetoresistive elements and magneto-impedance elements as the magnetic sensor elements, can be reduced in size and passively output magnetic signals. Since it is received, the signal between the sensors is not contaminated, and it is possible to improve the resolution by laying a lot. For this reason, the arithmetic device 5 ″ examines information obtained in combination with detailed position information such as the function of the brain, thereby making it possible to give meaning to the information obtained with higher resolution. It is effective to use the three-dimensional measuring device 8 ″ as a method for obtaining the position information of the measured portion simultaneously with the position information of the sensor.

  FIG. 18 is a flowchart for explaining a measurement method of the biomagnetic measurement device 1 ″ configured as described above. In step S01, a marker is attached to the head 21 of the subject 2, and in step S02, a three-dimensional tomographic image of the head 21 of the subject 2 is captured by the tomography apparatus 9 such as MRI, and the captured image is analyzed. To detect feature points. Subsequently, in step S1, the sensor unit 3 is placed on the head 21 of the subject 2, and in step S2 ′, each sensor platform board attached to the head 21 of the subject 2 by the three-dimensional measuring device 8. 32 and the relative positional relationship between feature points (markers) are measured.

  Thereafter, if necessary, the marker is removed in step S5, and the magnetic field is detected by each magnetic sensor element in step S3. In step S4, based on the relative positional relationship of the magnetic sensor elements in each sensor platform board 32 obtained by the three-dimensional measuring apparatus 8, the arithmetic unit 5 '' measures each magnetic sensor element as described above. A magnetoencephalogram with a weak current generated in the head 21 is created by magnetic field analysis of the result.

  In the present embodiment, subsequently, in step S6, the calculation device 5 ″ uses the feature point (marker) in the three-dimensional tomographic image obtained by the tomography device 9 and the three-dimensional measurement device 8 ″. By matching the obtained feature points (markers), the magnetoencephalogram obtained by the arithmetic device 5 ″ is synthesized with the three-dimensional tomographic image obtained by the tomography device 9.

  With this configuration, in addition to the relative positional relationship between the magnetic sensor elements, the relative positional relationship between the living body and the magnetic sensor element, for example, the spatial position information of the magnetic sensor element with respect to the brain model can be obtained. Accurate measurement enables high-definition magnetic measurement. This is particularly effective in the case of magnetoencephalography, because the shape of the brain is also important when assigning functions. For example, in the case where the measurement site is the brain, in order to know the actual state of the brain, it is required to measure the spatial resolution with an accuracy of 3 mm. Instead, this accuracy can be achieved because a three-dimensional tomographic image of the actual subject 2 using CT scan or MRI is used.

  In FIG. 18, steps S01 and S02 may be performed after performing steps S1 and S2 '. In that case, the position of each sensor platform board 32 can be measured also by tomography. Further, without using the optical three-dimensional measuring device 8 '', the position of the magnetic sensor element and the position of the subject 2 are simultaneously measured by the tomography apparatus 9 such as a CT scan, so that the CT scan information can include the magnetic sensor element or Since the information of the sensor platform board 32 is obtained, the position measurement between the magnetic sensor element and the human body and the biomagnetism measurement can be continuously performed, and the information can be linked as accurate three-dimensional information. Further, the three-dimensional image captured by the optical three-dimensional measuring device 8 '' may be further synthesized.

  In the above-described example, an optical three-dimensional measuring device using the stereo camera 81 is used as the three-dimensional measuring device 8, 8 ″ for measuring the relative position between the sensor platform boards 32, which is preferable. However, the method is not limited to this, and for example, there is a method using laser scanning or magnetism.

  First, in the optical three-dimensional measuring device 8, 8 ″, the shape of each sensor platform board 32 is used to discriminate between each sensor platform board 32 to be imaged and the living body (head 21). Since the outer shape of each sensor platform board 32 is a rectangular parallelepiped, the position of each sensor platform board 32 is specified from the four apexes facing outward. In that case, as a method for assisting in distinguishing between each sensor platform board 32 and a living body, a spherical marker, a color, a fluorescent paint, or a marker having a different reflectance is attached to the back of each sensor platform board 32. For example, it is shown in the literature (KONICA MINOLTA TECHNOLOGY REPORT VOL.6 (2009) Abe, Yamaguchi, Kono, Mukai non-contact 3D digitizer RANGE7 core technology).

  On the other hand, also in the laser scanning, by providing a marker on each sensor platform board 32 and detecting the marker, position measurement can be performed easily and / or precisely. In this case, it is also possible to attach a marker to the subject himself / herself.

  Another method for measuring the position of each sensor platform board 32 is to use magnetism. In this method, a measurer installs an arbitrary magnetic source in a magnetic silence space shielded by a magnetic field with a magnetic shield, measures the ratio of the magnetic strength with each sensor platform board 32, and the like. The relative positions of the sensor platform boards 32 are measured by calculating the relative positions of the sensor platform boards 32. There are various variations in this method, those having multiple magnetic sources, those that move the magnetic source, those that rotate the magnetic source at the same location, those that turn the magnetic field on and off with an electromagnet, etc. A combination method may be mentioned, but in this embodiment, measurement may be performed by any of these methods.

  Furthermore, each sensor platform board 32 is not necessarily fixed at the same place due to the shape of the head 21 of the subject 2, the convenience of measurement, etc., so that the relative position is set by the three-dimensional measuring devices 8, 8 '' as described above. Is measured, but the support members 31 and 31 'are made of a material such as rubber having a predetermined thickness and hardness, and the relative positional relationship between the sensor platform boards 32 is unlikely to be distorted. It is not always necessary to measure the positional relationship of all sensor platform boards 32.

  Moreover, each sensor platform board 32 may not be mounted on the support members 31 and 31 ′ but may be individually attached to a living body. In that case, a method of sticking the sensor platform board 32 itself to a living body through an adhesive sheet, a method of sticking with a suction cup, or the like can be considered. Also, as the sensor units 3 and 3 ′, adapters and holders are provided on the support members 31 and 31 ′, and the sensor platform board 32 is attached after the subject 2 covers the support members 31 and 31 ′. Good. Thus, the method for attaching the sensor platform board 32 to the living body is not particularly limited.

  When using the adapter or holder, instead of measuring the position of the sensor platform board 32 itself, the position of the adapter or holder is measured, and the position of the sensor platform board 32 is substantially the same as the position of the adapter or holder. The estimated position may be shifted from the position of the adapter or holder by a predetermined value.

  In the present embodiment, it is not only important to completely measure the positional relationship between all the positions of the magnetic sensor elements and the subject 2, but high sensitivity by using a magnetic sensor element that can be in close contact with a living body, The object is to achieve high accuracy and easy reading of the magnetoencephalogram by fixing the magnetic sensor element and acquiring relative position information between the magnetic sensor element and the subject 2. Therefore, in this embodiment, not all positions of the magnetic sensor element are measured, and it is not denied that the estimated position of the magnetic sensor element is used as described above for the positional relationship with the subject 2.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless a modification or improvement implemented by a person skilled in the art is at a level that significantly departs from the scope of the claims recited in the claims, the modification or the improvement is not entitled to the claims. It is interpreted as encompassing the scope.

1, 1 ′; 1a, 1a ′; 1 ″ Biomagnetic measuring device 2 Subject 21 Head 22 Eye 26 Chest 27 Abdomen 28 Heart 3, 3 ′ Sensor units 301, 302 Magnetic detection elements 3011 and 3021 Easy magnetization axis 3012 3022 Magnetization fixed shaft 31, 31 'Support member 32 Sensor platform board 321 TMR array module 322 Controller 323 RAM
324 Amplification / Conversion Circuit 34 Fixture 3a ', 3b' Member 4, 4 'Cover Member 5, 5''Arithmetic Unit 6 Interface 61 PCI Bus Controller 62 Command Conversion Buffer Controller 63 SRAM
64 Serial interface driver 7 Cable 71 Power line 72 Signal line 8, 8 ″ Three-dimensional measuring device 81 Stereo camera 82 I / F
83, 83 ″ position measuring unit 831, 831 ″ feature point extracting unit 832 position measuring unit 84, 84 ″ combining unit 841 position information integrating unit 842, 842 ″ feature point collating unit 89 device for detecting heartbeat period 9 Tomography equipment

Claims (8)

A plurality of magnetic sensors that are attached to the object to be measured and whose positions between the magnetic sensors are not fixed;
A three-dimensional measurement device that measures the relative positional relationship between the magnetic sensors attached to the measurement object;
Measurement that collects information on the weak current generated in the measurement object by performing magnetic field analysis of the measurement results of the magnetic sensors based on the relative positional relationship between the magnetic sensors obtained by the three-dimensional measurement apparatus. Including the device body,
The magnetic sensor is
A magnetic sensor using a ferromagnetic material and having a pair of mutually equal magnetic detection elements and an output end,
The pair of magnetic detection elements are arranged at intervals in the direction of the detection magnetic flux so that the direction of the easy magnetization axis is orthogonal to the detection magnetic flux and the mutual easy magnetization axes are orthogonal to each other,
The output terminal obtains a difference between detection results of the pair of magnetic detection elements . It further comprises a tomography apparatus that images a three-dimensional tomographic image of the living body to be measured,
The measurement apparatus body is obtained by the measurement apparatus body by matching the feature points in the three-dimensional tomographic image obtained by the tomography apparatus with the feature points obtained by the three-dimensional measurement apparatus. The magnetic measurement apparatus according to claim 1, wherein information relating to the weak current is synthesized with a three-dimensional tomographic image obtained by the tomography apparatus.   The magnetic measurement apparatus according to claim 2, wherein the plurality of magnetic sensors are mounted on a support member made of a flexible material.   The magnetic measurement apparatus according to claim 1, wherein the magnetic sensor is a tunnel magnetoresistive element, a giant magnetoresistive element, or a magnetoimpedance element.   The magnetic measurement apparatus according to claim 3, wherein the support member is a cylindrical body that covers the body portion.   6. The magnetic measurement apparatus according to claim 5, wherein the timing of taking in the signal from the magnetic sensor by the measurement apparatus main body is the same phase timing in the heartbeat cycle.   The magnetic measurement device according to claim 2, further comprising a covering member that covers the magnetic sensor attached to the living body and shields the magnetic sensor from an external magnetic field. In the biomagnetism measurement method for collecting information on the weak current generated in the living body,
Capturing a three-dimensional tomographic image of the living body with a tomographic apparatus and detecting a feature point from the captured image;
Detecting a magnetic field due to the weak current and attaching a plurality of magnetic sensors whose positions between the magnetic sensors are not fixed to the living body;
Measuring a relative positional relationship between the magnetic sensors attached to the living body by the three-dimensional measuring device and the feature points;
Detecting the magnetic field by each of the magnetic sensors;
Based on the relative positional relationship between the magnetic sensors obtained by the three-dimensional measuring device, the measuring device main body performs magnetic field analysis on the measurement results of the magnetic sensors, thereby providing information on the weak current generated in the living body. Collecting steps,
By matching the feature points in the three-dimensional tomographic image obtained by the tomography device with the feature points obtained by the three-dimensional measurement device, the measurement device body is obtained by the measurement device body. Synthesizing information on weak current with a three-dimensional tomographic image obtained by the tomography apparatus,
The magnetic sensor is a magnetic sensor using a ferromagnetic material and having a pair of mutually equivalent magnetic detection elements and an output end, and the pair of magnetic detection elements has a direction of an easy magnetization axis as a detection magnetic flux. The output ends are arranged to be spaced apart from each other in the direction of the detection magnetic flux so as to be orthogonal to each other and the axes of easy magnetization are orthogonal to each other, and the output end obtains a difference between detection results of the pair of magnetic detection elements. A biomagnetic measurement method characterized by the above.