Data processing method, program, and data processing system

Abstract

To provide a technology for accurately measuring a change in a magnetic field in a subject in the measurement of a magnetic field using a portable magnetic sensor.SOLUTION: A data processing method includes: a step S20 for acquiring an output value of a magnetic field from each of one or more magnetic sensors; a step S30 for specifying a magnetic field attributed to the position when the output value is derived for each of the one or more magnetic sensors; and a step S40 for generating a detection value by removing the magnetic field attributed to the position from the output value for each of the one or more magnetic sensors.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to data processing of portable magnetic sensors. [Background technology]

[0002] There is a known technology that uses multiple electromagnetic sensors placed on the surface of a subject's body to detect activity inside the body. For example, multiple sensors placed on the subject's head measure the brain's magnetic field, generate a magnetoencephalogram (MEG) using the measured brain magnetic field, and analyze the MEG to estimate biological activity.

[0003] Conventionally, a system including a plurality of superconducting quantum interference device (SQUID) sensors, each of which needs to be cooled by liquid helium, has been used to measure brain magnetic fields. Each SQUID sensor is fixed in a dewar filled with liquid helium. The dewar is equipped with 100 to 300 SQUID sensors, and a depression is provided on the helmet for inserting the head. In the measurement, the position of each SQUID sensor in the dewar must correspond to the position of the head. For this reason, the head is fixed in the depression. In the measurement, problems have been that the subject cannot move the head or trunk, and feels discomfort and fatigue.

[0004] In recent years, the development of small portable magnetic sensors that operate at room temperature has been actively carried out. Since magnetic sensors operate at room temperature, cooling with liquid helium is not required for measuring the brain magnetic field. Therefore, when such a sensor is used, if the sensor is fixed to the helmet, measurement is possible without restraining the head wearing the helmet. Regarding the measurement of the brain magnetic field using the above-mentioned portable magnetic sensor, for example, JP 2020-151023 A (Patent Document 1) and Ryan M. Hill, et. al., “Multi-channel whole-head OPM-MEG: Helmet design and a comparison with a conventional system”, Neuroimage, Oct. 01, 2020 (Non-Patent Document 1), various studies have been conducted. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-151023 A [Non-patent literature]

[0006] [Non-Patent Document 1] Ryan M. Hill, et. al., “Multi-channel whole-head OPM-MEG: Helmet design and a comparison with a conventional system”, Neuroimage, Oct. 01, 2020 Summary of the Invention [Problem to be solved by the invention]

[0007] The operating magnetic field range of portable magnetic sensors is relatively narrow, at around 50 nT or less. For this reason, like measurements using conventional SQUID sensors, measurements using portable magnetic sensors require a magnetically shielded room. In addition, measurements using portable magnetic sensors require components such as planar coils to make the magnetic field in the measurement area uniform in order to allow for subject movement (head movement in the case of measuring brain magnetic fields).

[0008] However, it is difficult to create a completely uniform magnetic field. Therefore, the cause of the change in the signal output from the portable magnetic sensor may be not only the change in the actual magnetic field in the subject, but also the change in the background magnetic field due to fluctuation. For this reason, a technology for accurately measuring the change in the magnetic field in the subject when measuring the magnetic field using a portable magnetic sensor is required.

[0009] The present invention has been devised in consideration of the above-mentioned circumstances, and its purpose is to provide a technique for accurately measuring changes in a magnetic field in a subject when measuring the magnetic field using a portable magnetic sensor. [Means for solving the problem]

[0010] A data processing method according to one aspect of the present disclosure is a data processing method for one or more magnetic sensors arranged in a given manner, comprising the steps of obtaining a magnetic field output value from each of the one or more magnetic sensors, determining for each of the one or more magnetic sensors a magnetic field due to the position at which the output value was derived, and generating a detection value for each of the one or more OPM sensors by removing the magnetic field due to the position from the output value. Effect of the Invention

[0011] According to one aspect of the present disclosure, a technique is provided for accurately measuring changes in a magnetic field in a subject using a portable magnetic sensor. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an overall configuration of a data processing system 1 for a portable magnetic sensor. [Diagram 2] 1A to 1C are diagrams showing the configuration of a helmet 20. [Diagram 3] FIG. 2 is a perspective view showing the inside of a magnetically shielded room. [Figure 4] FIG. 2 is a front view showing a schematic view of the inside of a magnetically shielded room. [Diagram 5] 2 is a diagram showing a schematic example of a magnetic field distribution in a measurement region 40. FIG. [Figure 6] 1 is a diagram showing an example of the state of a helmet 20 in a measurement area 40. FIG. [Figure 7] 13 is a diagram showing another example of the state of the helmet 20 in the measurement area 40. FIG. [Figure 8] 4A to 4C are diagrams showing specific examples of output values ​​and detection values ​​of the OPM sensor 2. [Figure 9] 1 is a flowchart of a process performed in a data processing system 1 for generating a magnetoencephalogram. [Figure 10] 10 is a flowchart of a modified example of the process of FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0014] <Embodiment 1> [Data processing system configuration] 1 is a diagram showing a schematic diagram of an overall configuration of a data processing system 1 for a portable magnetic sensor. In this embodiment, a case where an OPM (Optically Pumped Magnetometer) sensor 2, which is a small magnetic sensor that operates at room temperature, is used as an example of the portable magnetic sensor will be described. In addition to the OPM sensor, examples of the portable magnetic sensor include fluxgate sensors, tunnel magnetoresistance (TMR) sensors, and giant magnetoresistance (GMR) sensors. In this embodiment, the measurement of magnetoencephalograms will be described as an example, but the measurement target is not limited to magnetoencephalograms and may be other objects (magnetocardiograms).

[0015] The data processing system 1 includes a plurality of OPM sensors 2, an input device 3, an output device 4, and a processing device 10. The data processing system 1 is configured to estimate the position of a biological activity site (current source) in the subject's brain using the detection results from the plurality of OPM sensors 2.

[0016] Each of the multiple OPM sensors 2 is installed on the helmet 20. When the subject 50 wears the helmet 20 on his / her head, each of the multiple OPM sensors 2 is disposed in a given manner on the head of the subject 50. For convenience of explanation, the number of OPM sensors 2 shown in FIG. 1 is "4", however, the number of OPM sensors 2 used for measurement is not limited to this.

[0017] The input device 3 is, for example, a pointing device such as a keyboard or a mouse, and accepts input information (such as calculation conditions described below) from a user. The information input to the input device 3 is sent to the processing device 10. The output device 4 is, for example, a liquid crystal display (LCD) panel, and is a display that displays information to the user.

[0018] The processing device 10 includes, as main hardware elements, a sensor interface 11, an input interface 12, an output interface 13, a storage device 14, and a calculation device 15. The processing device 10 may be realized, for example, by a general-purpose computer, or may be realized by a computer (such as a server) dedicated to the data processing system 1.

[0019] The sensor interface 11 is an interface for connecting the processing device 10 and the multiple OPM sensors 2, and realizes the input and output of signals between the processing device 10 and the multiple OPM sensors 2. The input interface 12 is an interface for connecting the processing device 10 and the input device 3, and realizes the input and output of signals between the processing device 10 and the input device 3. The output interface 13 is an interface for connecting the processing device 10 and the output device 4, and realizes the input and output of data between the processing device 10 and the output device 4.

[0020] The storage device 14 non-temporarily stores information (programs, etc.) used for processing by the arithmetic device 15. Note that input information (such as calculation conditions described below) input by the user to the input device 3 is stored in the storage device 14.

[0021] [helmet] 2 is a diagram showing a configuration of a helmet 20. A plurality of OPM sensors 2 are attached to the helmet 20. In one implementation example, the arrangement of the plurality of OPM sensors 2 is fixed in the helmet 20.

[0022] [Measurement environment] Fig. 3 is a perspective view typically showing the inside of the magnetically shielded room, and Fig. 4 is a front view typically showing the inside of the magnetically shielded room.

[0023] The measurement of the brain magnetic field is carried out in a magnetically shielded room 30. In the magnetically shielded room 30, boards 31 and 32, each equipped with a planar coil for noise cancellation, are arranged on one side and the other side of a subject 50, respectively.

[0024] In the magnetically shielded room 30, a measurement area 40 is defined as an area in which the head of the subject 50 is expected to be located. The measurement area 40 is, for example, a rectangular parallelepiped of 40 cm square. However, there is no particular limit to the size of the measurement area 40.

[0025] [Spatial magnetic field distribution] FIG. 5 is a diagram showing a schematic example of a magnetic field distribution in the measurement region 40. In FIG. 5, the magnetic fields measured in advance for each of the multiple locations in the measurement region 40 are indicated by arrows. The direction of the arrows represents the direction of the magnetic field in a three-dimensional space defined by three axes (X-axis, Y-axis, and Z-axis). The length of the arrow represents the magnitude of the magnetic field. The direction and magnitude of the magnetic field at each of the multiple locations in the measurement region 40 are stored, for example, in the storage device 14 as a "spatial magnetic field distribution." In one example, the magnetic fields at 125 locations located at 10 cm intervals in a 40 cm square space are stored as a "spatial magnetic field distribution."

[0026] In one implementation example, the magnetic field is measured at each of a plurality of locations in the measurement area 40 without the subject being present in the magnetically shielded room 30. The computing device 15 generates a spatial magnetic field distribution based on the measurement results, and the generated spatial magnetic field distribution is stored in the storage device 14.

[0027] [Background magnetic field] The data processing system 1 generates a magnetoencephalogram of the subject 50 based on the detection values ​​of each of the multiple OPM sensors 2. Note that the position of each OPM sensor 2 may change during measurement of the brain magnetic field. The data processing system 1 identifies the background magnetic field caused by the position of each OPM sensor 2, and generates a detection value by subtracting the background magnetic field from the output value.

[0028] More specifically, when the data processing system 1 acquires the output value from each OPM sensor 2, it generates a detection value from the output value for each OPM sensor 2. In this way, detection values ​​are generated for the multiple OPM sensors 2. Then, the data processing system 1 generates a magnetoencephalogram using the detection values ​​generated for the multiple OPM sensors 2. Below, the change in position of the OPM sensor 2, the identification of the background magnetic field caused by the position, and the derivation of the detection value will be described in more detail.

[0029] (Change in position of OPM sensor 2) In the data processing system 1, the helmet 20 swings in conjunction with the swinging of the head of the subject 50, which may cause the position of each OPM sensor 2 to change. Fig. 6 is a diagram showing an example of the state of the helmet 20 in the measurement area 40. Fig. 7 is a diagram showing another example of the state of the helmet 20 in the measurement area 40. For ease of explanation, in Figs. 6 and 7, three OPM sensors 2 out of the multiple OPM sensors 2 are shown as OPM sensors 2A, 2B, and 2C.

[0030] 6 and 7, when the head of the subject 50 wearing the helmet 20 swings, the position and posture of the helmet 20 change. More specifically, the helmet 20 is located at the upper left of the measurement area 40 in Fig. 6, whereas the helmet 20 is located at the upper left of the measurement area 40 in Fig. 7.

[0031] Furthermore, the posture of helmet 20 changes between Figures 6 and 7, which changes the positional relationship between OPM sensors 2A, 2B, and 2C. More specifically, OPM sensor 2A is located at the lower left relative to OPM sensors 2B and 2C in Figure 6, whereas it is located at the upper right relative to OPM sensors 2B and 2C in Figure 7.

[0032] (Determining the background magnetic field for each OMP sensor2) While the geomagnetic field is on the order of several microT, changes in the brain's magnetic field occur in the range of several femtoT. Even if the magnetoencephalogram is measured inside the magnetically shielded room 30, it is difficult to keep the magnetic field inside the magnetically shielded room 30 constant to an extent that it does not affect the brain's magnetic field. For this reason, it is expected that when the position of the OPM sensor 2 changes, the magnitude of the background magnetic field included in the output value of the OPM sensor 2 changes. Therefore, if the output value of the OPM sensor 2 is used as it is as a detection value to generate the magnetoencephalogram, the magnetoencephalogram may lack accuracy.

[0033] Data processing system 1 identifies a location within measurement region 40 of each OPM sensor 2. Data processing system 1 identifies the magnetic field at the identified location, among the magnetic fields at multiple locations within measurement region 40 registered as a spatial magnetic field distribution, as the background magnetic field of each OPM sensor 2. For example, if magnetic fields at 125 locations are registered as a spatial magnetic field distribution and 20 OPM sensors 2 are attached to helmet 20, data processing system 1 identifies the magnetic field at the location corresponding to each of the 20 OPM sensors 2, among the magnetic fields at the 125 locations, as the background magnetic field of each OPM sensor 2.

[0034] In one implementation, the data processing system 1 utilizes maximum likelihood estimation to determine the background magnetic field of each OPM sensor 2 .

[0035] More specifically, data processing system 1 obtains output values ​​from a first number of OPM sensors 2. In this way, data processing system 1 obtains the first number of output values. Then, data processing system 1 arranges the first number of output values ​​according to the arrangement of the first number of OPM sensors 2 on helmet 20.

[0036] In the spatial magnetic field distribution, the magnetic fields of a second number of locations (greater than the first number) are registered.

[0037] The data processing system 1 searches for a combination of magnetic fields at the first number of locations corresponding to the first number of output values ​​arranged as described above among the magnetic fields at the second number of locations constituting the spatial magnetic field distribution. Maximum likelihood estimation is used for this search. In maximum likelihood estimation, the likelihood functions shown in the following formulas (1) and (2) are defined.

[0038]

number

[0039] In the above formulas (1) and (2), each OPM sensor 2 is represented as sensor=1 to n. Formula (1) represents the actual measurement value y obtained from each magnetic sensor. In formula (1), the magnetic measurement values ​​of each OPM sensor 2 in the three axial directions are represented as fsx, fsy, and fsz. Formula (2) represents the magnetic field V at any sensor arrangement in the magnetic field space G. In formula (2), the magnetic field measurement values ​​of each OPM sensor 2 at coordinates (x, y, z) in the magnetic field space G are represented as fgx, fgy, and fgz. Then, the position of the helmet (head) that changes over time due to head shaking, etc., that is, the background magnetic field of each OPM sensor, is obtained from the minimum value of the square error between the actual measurement value y and the magnetic field V.

[0040] Then, the data processing system 1 selects a first number of magnetic field combinations having the maximum value of the likelihood function from the magnetic fields at a second number of locations registered as the spatial magnetic field distribution as the magnetic field combination corresponding to the combination of the first number of OPM sensors 2.

[0041] The data processing system 1 decomposes the first number of magnetic field combinations selected from the spatial magnetic field distribution into background magnetic fields for each OPM sensor 2 according to the arrangement of the multiple OPM sensors 2 on the helmet 20 .

[0042] For example, if 20 OPM sensors 2 are attached to helmet 20, and brain magnetic fields corresponding to biological activity are generated at positions corresponding to 4 of the OPM sensors 2, while brain magnetic fields corresponding to biological activity are not generated at positions corresponding to the remaining 16 OPM sensors 2, then the output values ​​of the 16 OPM sensors 2 should match the value of the background magnetic field. From this, a combination of the output values ​​of the 20 OPM sensors 2 on helmet 20 can be used by maximum likelihood estimation using the likelihood function shown in equation (1) to select a combination of background magnetic fields for the 20 OPM sensors 2 from a plurality of combinations of magnetic fields registered as a spatial magnetic field distribution.

[0043] In the data processing system 1, the magnetic fields at each of a plurality of locations in the measurement region 40 are stored as a spatial magnetic field distribution. That is, in the data processing system 1, movement of the head of the subject 50 is permitted within the measurement region 40. The wider the measurement region 40, the wider the permitted range of head movement of the subject 50, but the greater the amount of calculation required in maximum likelihood estimation. Therefore, the size of the measurement region 40 may be set based on the amount of calculation permitted in maximum likelihood estimation.

[0044] (Derivation of detection value) Fig. 8 is a diagram showing specific examples of output values ​​and detection values ​​of the OPM sensor 2. In Fig. 8, graph G1 shows output values ​​as line L11, and graph G2 shows detection values ​​as line L21. In graphs G1 and G2, the vertical axis represents the strength of the magnetic field, and the horizontal axis represents time.

[0045] In the graph G1, the line L12 represents the background magnetic field. In the example of Fig. 8, the detection value represented by the line L21 is calculated by subtracting the value of the line L12 from the value of the line L11. That is, the detection value corresponds to the value obtained by removing the background magnetic field from the output value.

[0046] [Processing flow] Fig. 9 is a flowchart of a process for generating a magnetoencephalogram, which is performed in the data processing system 1. In one implementation example, the processing device 15 in the processing device 10 executes a given program to realize the process of Fig. 9.

[0047] In step S10, the arithmetic device 15 determines whether or not an instruction to start magnetoencephalogram measurement has been received. The instruction to start magnetoencephalogram measurement may be input to the arithmetic device 15 from the input device 3, or may be input to the arithmetic device 15 from an external device via a network. The arithmetic device 15 repeats the control of step S10 until it determines that an instruction to start measurement has been received (NO in step S10), and when it determines that an instruction to start measurement has been received (YES in step S10), it proceeds to control to step S20.

[0048] In step S20, the calculation device 15 acquires output values ​​from the multiple OPM sensors 2.

[0049] In step S30, the computing device 15 identifies, from the spatial magnetic field distribution, the background magnetic field components of each of the multiple OPM sensors 2. In one implementation example, the control of step S30 follows the content described above in [Identification of background magnetic field].

[0050] In step S40, the calculation device 15 generates a detection value of each of the multiple OPM sensors 2 by removing the background magnetic field from each of the output values ​​of the multiple OPM sensors 2.

[0051] In step S50, the arithmetic device 15 generates a magnetoencephalogram using the detection values ​​of each of the multiple OPM sensors 2, and outputs the magnetoencephalogram. The output of the magnetoencephalogram is, for example, displayed on the output device 4. After that, the arithmetic device 15 returns control to step S10.

[0052] In the above-described embodiment 1, the calculation device 15 generates detection values ​​of the multiple OPM sensors 2 by removing the background magnetic field from the output values ​​of the multiple OPM sensors 2. Then, the calculation device 15 generates a magnetoencephalogram using the detection values ​​of the multiple OPM sensors 2.

[0053] <Embodiment 2> The computing device 15 may perform correction of the magnetic fields at multiple locations registered as a spatial magnetic field distribution.

[0054] Furthermore, the multiple OPM sensors 2 may be attached to a deformable member such as headgear, instead of to a non-deformable member such as a helmet, and in such a case, the computing device 15 may perform control to specify the arrangement of the multiple OPM sensors 2 on the head of the subject 50 wearing the headgear.

[0055] Fig. 10 is a flowchart of a modified example of the process of Fig. 9. Compared with the process of Fig. 9, the process of Fig. 10 further includes steps S02, S04, and S06.

[0056] With reference to FIG. 10, in step S02, the arithmetic device 15 corrects the spatial magnetic field distribution.

[0057] More specifically, the calculation device 15 measures the magnetic field at one of the locations where the magnetic field is registered in the spatial magnetic field distribution. The calculation device 15 also compares the measured magnetic field at the one location with the magnetic field registered in the spatial magnetic field distribution. The calculation device 15 then adds the difference between the measured magnetic field and the registered magnetic field to the magnetic fields at all the locations registered in the spatial magnetic field distribution. That is, the calculation device 15 detects the magnetic field at one location and corrects the magnetic fields at both the one location and other locations included in the spatial magnetic field distribution using the result of the detection.

[0058] As the above-mentioned "one location," it is preferable to select a location where the OPM sensor 2 is unlikely to be located in the magnetoencephalogram measurement from among the multiple locations defined in the measurement area 40. Note that the detection values ​​of the magnetic fields at two or more locations may be used for the correction.

[0059] In step S04, the computing device 15 acquires an image (eg, a 3D image) of the subject wearing the headgear.

[0060] In step S06, the calculation device 15 analyzes the image acquired in step S04 to identify the arrangement of the multiple OPM sensors 2 on the subject's head. In one implementation, the analysis of the image identifies portions of the image corresponding to each of the multiple OPM sensors 2, and identifies the arrangement of the multiple OPM sensors 2 on the subject's head based on the arrangement of the portions of each OPM sensor 2. Thereafter, the calculation device 15 advances control to step S10.

[0061] According to the process described with reference to Fig. 10, the magnetic fields at a plurality of locations constituting the spatial magnetic field distribution are appropriately corrected. Correction of the spatial magnetic field distribution ensures the accuracy of the value used as the background magnetic field, and thus the accuracy of the detected value of the magnetic field can be ensured.

[0062] 10, even if the subject 50 wears a member made of a flexible material, such as headgear, instead of the helmet 20, the data processing system 1 can recognize the arrangement of the multiple OPM sensors 2 and use it to generate detection values. This allows various modes in which the subject 50 wears the multiple OPM sensors 2.

[0063] The timing (or conditions) for performing the correction of the spatial magnetic field distribution in step S02 and / or the identification of the positions of the multiple OPM sensors 2 in steps S04 and S06 may be set as appropriate. For example, when multiple magnetoencephalograms are continuously measured for the same subject 50, the correction of the spatial magnetic field distribution in step S02 and / or the identification of the positions of the multiple OPM sensors 2 in steps S04 and S06 may be performed for each magnetoencephalogram measurement, or may be performed only once before the multiple magnetoencephalogram measurements.

[0064] [Aspects] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0065] (Clause 1) A data processing method according to one embodiment is a data processing method for one or more portable magnetic sensors arranged in a given manner, and may include the steps of obtaining a magnetic field output value from each of the one or more magnetic sensors, identifying, for each of the one or more magnetic sensors, a magnetic field due to the position when the output value was derived, and generating a detection value for each of the one or more magnetic sensors by removing the magnetic field due to the position from the output value.

[0066] According to the data processing method described in the first aspect, a technique for accurately measuring changes in a magnetic field in a subject when measuring the magnetic field using a magnetic sensor is provided.

[0067] (Clause 2) In the data processing method described in clause 1, the one or more magnetic sensors derive their output values ​​in a measurement area, and a magnetic field distribution is identified for the measurement area, and identifying the magnetic field due to the position may include identifying a combination of magnetic fields corresponding to the combination of the output values ​​of the one or more magnetic sensors from the magnetic field distribution in the measurement area, and identifying a magnetic field corresponding to each position of the one or more magnetic sensors from the identified combination of magnetic fields.

[0068] According to the data processing method described in the second aspect, the magnetic field distribution in the measurement region can be used as the magnetic field corresponding to the respective positions of the one or more magnetic sensors.

[0069] (Clause 3) In the data processing method described in clause 2, identifying the combination of magnetic fields may include calculating, for each of a plurality of combinations of magnetic fields according to the given aspect in the magnetic field distribution, a value of a likelihood function that each combination is a combination of the output values ​​of the one or more magnetic sensors, and identifying, from among the plurality of combinations, a combination for which the value of the likelihood function is maximum.

[0070] According to the data processing method described in section 3, an appropriate magnetic field can be selected for each position of one or more magnetic sensors from among a plurality of magnetic fields that constitute the magnetic field distribution in the measurement region.

[0071] (Clause 4) The data processing method described in clause 3 may further include a step of measuring a magnetic field at at least one point in the measurement area, and a step of correcting the magnetic field distribution based on the magnetic field at the at least one point.

[0072] According to the data processing method described in Section 4, by correcting the magnetic field distribution in the measurement area, more accurate values ​​can be used as the magnetic field corresponding to the respective positions of the one or more magnetic sensors.

[0073] (Clause 5) The data processing method described in any one of clauses 1 to 4 may further include a step of acquiring position information of each of the one or more magnetic sensors when attached to a subject, and a step of identifying the given state based on the position information of each of the one or more magnetic sensors.

[0074] According to the data processing method described in section 5, various modes are acceptable for the subject to wear one or more magnetic sensors.

[0075] (Item 6) A program according to one aspect may cause a computer to implement the data processing method according to any one of items 1 to 5 by being executed by one or more processors of the computer.

[0076] According to the program described in item 6, a technique is provided for accurately measuring changes in a magnetic field in a subject when measuring the magnetic field using a magnetic sensor.

[0077] (Clause 7) A data processing system according to one embodiment includes a computer and one or more portable magnetic sensors, and the computer may include one or more processors and a storage device that stores the program described in clause 6.

[0078] According to the data processing system described in item 7, a technique for accurately measuring changes in a magnetic field in a subject in measuring a magnetic field using a magnetic sensor is provided.

[0079] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims, not by the description of the above-mentioned embodiments, and is intended to include all modifications within the meaning and scope of the claims. In addition, it is intended that each technology in the embodiments can be implemented alone or, if necessary, in combination with other technologies in the embodiments as far as possible. [Explanation of symbols]

[0080] 1 data processing system, 2, 2A, 2B, 2C OPM sensor, 3 input device, 4 output device, 10 processing device, 20 helmet, 30 magnetically shielded room, 31, 32 board, 40 measurement area, 50 subject.

Claims

1. A method for processing data from one or more portable magnetic sensors arranged in a given manner, comprising the steps of: obtaining a magnetic field output value from each of the one or more magnetic sensors; identifying, for each of the one or more magnetic sensors, a magnetic field resulting from a position at which the output value was derived; and generating a detection value for each of the one or more magnetic sensors by removing a magnetic field due to the position from the output value.

2. the one or more magnetic sensors derive the output value in a measurement region; A magnetic field distribution is determined for the measurement region; Identifying the magnetic field due to the location includes: Identifying a combination of magnetic fields corresponding to a combination of the output values ​​of the one or more magnetic sensors from the magnetic field distribution in the measurement area; The data processing method according to claim 1 , further comprising: determining, from the combination of the determined magnetic fields, a magnetic field corresponding to a position of each of the one or more magnetic sensors.

3. Identifying the combination of magnetic fields includes: calculating a value of a likelihood function for each of a plurality of combinations of magnetic fields according to the given aspect in the magnetic field distribution, the value of the likelihood function indicating that each combination is a combination of the output values ​​of the one or more magnetic sensors; The data processing method according to claim 2 , further comprising identifying a combination that maximizes the value of the likelihood function from among the plurality of combinations.

4. measuring a magnetic field at at least one point in the measurement region; The data processing method according to claim 3 , further comprising the step of correcting the magnetic field distribution based on the magnetic field at the at least one point.

5. acquiring position information of each of the one or more magnetic sensors in a state where the magnetic sensors are attached to a subject; The data processing method according to claim 1 or 2, further comprising: identifying the given aspect based on the position information of each of the one or more magnetic sensors.

6. A program that, when executed by one or more processors of a computer, causes the computer to carry out the data processing method according to claim 1 or 2.

7. A computer, one or more portable magnetic sensors; The computer includes: one or more processors; A data processing system comprising: a storage device that stores the program according to claim 6.

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