Brain measurement device and brain measurement method

Abstract

To efficiently achieve magnetoencephalographic measurement and MRI measurement.SOLUTION: A brain measuring device M1 includes: a magnetoencephalography including a plurality of optical excitation magnetic sensors 1A for measuring a brain magnetic field, a plurality of correction magnetic sensors 2 for measuring geomagnetism and a variable magnetic field at each position of the plurality of optical excitation magnetic sensors 1A, and a correction coil for correcting the geomagnetism and the variable magnetic field; an MRI device including a static magnetic field coil for applying a static magnetic field, a gradient magnetic field coil for applying a gradient magnetic field, and a transmission / reception coil for transmitting a transmission pulse of a predetermined frequency and detecting a nuclear magnetic-resonance signal generated by the transmission of the transmission pulse; and a control device 4 for controlling an electric current supplied to the correction coil on the basis of a measurement value of the geomagnetism and a measurement value of the variable magnetic field by the plurality of correction magnetic sensors 2 when measuring a brain magnetic field, controlling an electric current supplied to the static magnetic field coil and the gradient magnetic field coil when measuring an MR image, and generating the MR image on the basis of the output of the transmission / reception coil.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a brain measurement apparatus and a brain measurement method. [Background technology]

[0002] Conventionally, superconducting quantum interference devices (SQUIDs) have been used as magnetoencephalographs to measure weak brain magnetic fields. In recent years, magnetoencephalographs using optically excited magnetic sensors have been researched instead of SQUIDs. Optically excited magnetic sensors measure weak magnetic fields by detecting the spin polarization of alkali metal atoms excited by optical pumping. For example, Patent Document 1 discloses a magnetoencephalograph that uses an optically pumped magnetometer. Recently, research has also been conducted to combine a magnetoencephalograph and an MRI (Magnetic Resonance Imaging) device using a SQUID (see Non-Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5823195 [Non-patent literature]

[0004] [Non-Patent Document 1] “SQUIDs in biomagnetism: a roadmap towards improved healthcare”,Supercond. Sci. Technol. 29 (2016) 113001 (30pp) Summary of the Invention [Problem to be solved by the invention]

[0005] Here, measurements using a magnetoencephalograph must be performed in a state where magnetic noise, including geomagnetic field, is reduced to avoid the influence of magnetic noise that is stronger than the brain's magnetic field. On the other hand, measurements using an MRI must be performed in a state where a static magnetic field, a gradient magnetic field, etc. are generated. To realize a device that integrates a magnetoencephalograph and an MRI device, it is necessary to efficiently reduce magnetic noise and apply a static magnetic field, a gradient magnetic field, etc.

[0006] The present embodiment has been made in view of the above circumstances, and aims to provide a brain measurement device and a brain measurement method that can efficiently realize magnetoencephalography and MRI measurement. [Means for solving the problem]

[0007] A brain measuring device according to one aspect of the embodiment includes: a magnetoencephalograph having a plurality of optically excited magnetic sensors for measuring brain magnetic fields, a plurality of corrective magnetic sensors for measuring the geomagnetic field and variable magnetic fields at the positions of the plurality of optically excited magnetic sensors, and a correction coil for correcting the geomagnetic field and variable magnetic fields; an MRI device having a static magnetic field coil for applying a static magnetic field, a gradient magnetic field coil for applying a gradient magnetic field, and a transmit / receive coil for transmitting transmission pulses of a predetermined frequency and detecting nuclear magnetic resonance signals generated by the transmission of the transmission pulses; and a control device that, when measuring the brain magnetic field, controls the current supplied to the correction coil based on the measurement values ​​of the geomagnetic field and the variable magnetic field measured by the plurality of corrective magnetic sensors, and, when measuring MR images, controls the current supplied to the static magnetic field coil and the gradient magnetic field coil to control the static magnetic field and the gradient magnetic field, and generates MR images based on the output of the transmit / receive coil.

[0008] Alternatively, a brain measurement method according to another aspect of the embodiment is a brain measurement method using a magnetoencephalograph having a plurality of optically excited magnetic sensors that measure brain magnetic fields, a plurality of corrective magnetic sensors that measure the geomagnetic field and variable magnetic fields at the positions of each of the plurality of optically excited magnetic sensors, and a correction coil for correcting the geomagnetic field and variable magnetic fields, and an MRI apparatus having a static magnetic field coil for applying a static magnetic field, a gradient magnetic field coil for applying a gradient magnetic field, and a transmit / receive coil that transmits transmit pulses of a predetermined frequency and detects nuclear magnetic resonance signals generated by the transmission of the transmit pulses, wherein, when measuring the brain magnetic fields, the current supplied to the correction coil is controlled based on the measurement values ​​of the geomagnetic field and the variable magnetic field measured by the plurality of corrective magnetic sensors, and when measuring MR images, the static magnetic field and gradient magnetic field are controlled by controlling the current supplied to the static magnetic field coil and the gradient magnetic field coil, and an MR image is generated based on the output of the receive coil.

[0009] According to the above one or other aspects, the geomagnetic field and the variable magnetic field are measured at the respective positions of a plurality of optically excited magnetic sensors that measure the brain magnetic field. Then, when measuring the brain magnetic field, the current flowing through the correction coil is controlled based on the measured values ​​of the geomagnetic field and the variable magnetic field, and a magnetic field is generated in the correction coil. As a result, the geomagnetic field and the variable magnetic field are corrected by the magnetic field generated in the correction coil at the positions of the plurality of optically excited magnetic sensors. By correcting the geomagnetic field and the variable magnetic field at the positions of the plurality of optically excited magnetic sensors, the plurality of optically excited magnetic sensors can measure the brain magnetic field while avoiding the influence of the geomagnetic field and the variable magnetic field.

[0010] On the other hand, according to the above one or other aspects, when measuring an MR image, the static magnetic field and the gradient magnetic field are applied by controlling the currents flowing through the static magnetic field coil and the gradient magnetic field coil, and the nuclear magnetic resonance signals generated by the transmission of the transmission pulses are detected. As a result, the MR image can be measured based on the outputs of the transmit and receive coils.

[0011] With this brain measurement device and method, it is possible to efficiently perform MEG measurement and MRI measurement using the same device. In particular, in MRI measurement, a superconducting static magnetic field coil is not required, and a magnetically shielded room for reducing magnetic noise during MEG measurement is not required. Also, a coolant such as liquid helium, which is required when using SQUID, is not required, making it possible to reduce the size and cost. Furthermore, since MEG measurement and MRI measurement can be performed sequentially on the same subject using the same device, it is possible to reduce registration errors in the results of both measurements.

[0012] The correction coil may include a geomagnetic correction coil for correcting the geomagnetic field and a variable magnetic field correction coil for correcting the variable magnetic field. The control device may determine a current for the geomagnetic correction coil based on a measured value of the geomagnetic field to generate a magnetic field that cancels the geomagnetic field, and may determine a current for the variable magnetic field correction coil based on a measured value of the variable magnetic field to generate a magnetic field that cancels the variable magnetic field. In this configuration, the geomagnetic correction coil and the static magnetic field coil may be used in common in some cases, which may further reduce the size and cost of the device. This configuration enables highly accurate measurement of brain magnetic fields without using a magnetically shielded room. Furthermore, the number of turns of the geomagnetic correction coil for correcting geomagnetic fields with a strength on the order of 10 μT and the number of turns of the variable magnetic field correction coil for correcting variable magnetic fields with a strength on the order of 10 nT can be optimized, respectively, thereby enabling accurate correction of the geomagnetic field and the variable magnetic field.

[0013] The correction coil may include a geomagnetic gradient correction coil for correcting the geomagnetic gradient. The control device may determine the current to the geomagnetic gradient correction coil based on the measured geomagnetic field so as to generate a magnetic field that cancels the geomagnetic gradient. In such a configuration, the geomagnetic gradient correction coil and the gradient magnetic field coil may be shared in some cases, which enables further miniaturization and cost reduction of the device. Furthermore, uniform magnetic field correction (zeroth-order correction) is performed by controlling the current to the correction coil, and further, correction of the geomagnetic gradient taking into account differences in the positions of each optically excited magnetic sensor (first-order correction) is performed by controlling the current to the geomagnetic gradient correction coil. In this way, the geomagnetic field and the geomagnetic gradient are canceled out in stages, allowing for accurate correction of the geomagnetic field.

[0014] The correction coil may include a variable magnetic field gradient correction coil for correcting the gradient of the variable magnetic field. The control device may determine a current for the variable magnetic field gradient correction coil based on the measured value of the variable magnetic field so as to generate a magnetic field that cancels out the gradient of the variable magnetic field. In this case, uniform variable magnetic field correction (zeroth-order correction) is performed by controlling the current for the correction coil, and further, correction of the gradient of the variable magnetic field taking into account the difference in position of each optically excited magnetic sensor (first-order correction) is performed by controlling the current for the variable magnetic field gradient correction coil. In this way, the variable magnetic field and the gradient of the variable magnetic field are canceled out in stages, allowing the variable magnetic field to be corrected with high accuracy.

[0015] The correction coil may be configured by a pair of coils arranged on either side of the plurality of optically excited magnetic sensors. In this case, the geomagnetism and the fluctuating magnetic field at the positions of the plurality of optically excited magnetic sensors sandwiched between the pair of correction coils are effectively corrected. This allows the geomagnetism and the fluctuating magnetic field to be appropriately corrected with a simple configuration.

[0016] The corrective magnetic sensor may be a fluxgate sensor that outputs a measurement value of the geomagnetic field as a DC component and a measurement value of the fluctuating magnetic field as an AC component. The dynamic range of the fluxgate sensor may include a geomagnetic field having a strength on the order of 10 μT and a fluctuating magnetic field of a specific frequency (e.g., a commercial frequency) having a strength on the order of 10 nT. The fluctuating magnetic field of the specific frequency is a particularly strong magnetic field among fluctuating magnetic fields. Such a fluxgate sensor can suitably measure the geomagnetic field and the fluctuating magnetic field of the specific frequency.

[0017] The transmit / receive coil may include a transmit coil for transmitting a transmit pulse and a receive coil for detecting a nuclear magnetic resonance signal. In this case, the receive coil can be placed near the object to be measured, and the transmit coil can be placed in a different location from the receive coil, thereby improving design flexibility. Furthermore, when multiple small receive coils are placed around the object to be measured, the sensitivity of the receive coils can be improved and noise can be reduced.

[0018] The transmit / receive coil may serve both as a coil for transmitting transmit pulses and a coil for detecting nuclear magnetic resonance signals, which allows for further miniaturization and cost reduction of the device.

[0019] The transmit / receive coil may be formed in a spiral shape and arranged to surround the object to be measured. In this case, the transmit / receive coil can be arranged close to the object to be measured, thereby improving the accuracy of MRI measurement.

[0020] The multiple optically excited magnetic sensors may be axial gradiometers with a measurement region and a reference region on the same axis, perpendicular to the object to be measured. In this case, the influence of common mode noise is indicated in both the output result of the measurement region and the output result of the reference region, and the common mode noise can be removed by obtaining the difference between the two output results. This improves the measurement accuracy of the brain magnetic field.

[0021] The device may further include an output coil electrically connected to the transmit / receive coil and configured to output a magnetic signal based on a current flowing through the transmit / receive coil, and another optically excited magnetic sensor that detects the magnetic signal output by the output coil. The control device may generate an MR image based on the magnetic signal detected by the other optically excited magnetic sensor. With this configuration, signals can be received by the other optically excited magnetic sensor with high sensitivity on the order of fT, thereby improving the accuracy of MR image measurement. Furthermore, since the other optically excited magnetic sensor is located away from the transmit / receive coil to which a static magnetic field on the order of mT is applied, the sensitivity band of the sensor can be adjusted without being affected by the static magnetic field.

[0022] The optically excited magnetic sensors may be configured to have a bias magnetic field applied thereto so that they are sensitive to frequencies in the range of 0 to 200 Hz. Another optically excited magnetic sensor may be configured to have a bias magnetic field applied thereto so that it is sensitive to frequencies in the range of 20 kHz to 500 kHz. This configuration can increase the sensitivity of brain magnetic field measurement while also improving the accuracy of MRI measurement.

[0023] The optically excited magnetic sensors, the correction magnetic sensors, and the receiver coil may be fixed to a helmet-type non-magnetic frame worn on the subject's head. With this configuration, the non-magnetic frame worn on the head and the sensors and receiver coils fixed to the non-magnetic frame move in accordance with the subject's head movement. Therefore, even if the subject's head moves, it is possible to appropriately correct the geomagnetic field and fluctuating magnetic fields at the positions of the optically excited magnetic sensors, measure the brain magnetic field, and perform MRI measurement. As a result, registration errors in both measurements can be reduced.

[0024] An electromagnetic shield for blocking high-frequency electromagnetic noise may be further provided. With this configuration, high-frequency electromagnetic noise that is not the target of measurement in the magnetoencephalograph can be prevented from penetrating into the multiple optically excited magnetic sensors. This allows stable operation of the measurement of the brain magnetic field using the multiple optically excited magnetic sensors. On the other hand, in MRI measurement, it is possible to prevent the penetration of noise in the signal range of 20 kHz to 500 kHz. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a brain measuring device and a brain measuring method that can efficiently perform magnetoencephalography and MRI measurement. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing the configuration of a brain-measuring apparatus according to an embodiment. [Figure 2] FIG. 1 is a schematic diagram showing a configuration for connection between a fluxgate sensor and a controller. [Figure 3] FIG. 2 is a schematic diagram showing the configuration of an OPM module 23 according to the embodiment. [Figure 4] 10 is a flowchart showing the operation of the brain-measuring apparatus according to the embodiment. [Figure 5] 10 is a flowchart showing the operation of the brain-measuring apparatus according to the embodiment. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a brain-measuring apparatus according to another embodiment. [Figure 7] FIG. 10 is a schematic diagram showing the configuration of a brain-measuring apparatus according to another embodiment. [Figure 8] 10 is a flowchart showing the operation of a brain-measuring apparatus according to another embodiment. [Figure 9] FIG. 10 is a schematic diagram showing the configuration of a brain-measuring apparatus according to a modified example. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a brain-measuring apparatus according to a modified example. [Figure 11] FIG. 10 is a schematic diagram showing the configuration of a brain-measuring apparatus according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0028] 1 is a schematic diagram showing the configuration of a brain-measuring device M1 according to an embodiment. The brain-measuring device M1 is a device for measuring brain magnetic fields and magnetic resonance (MR) images of a subject. The brain-measuring device M1 includes a magnetoencephalograph module having multiple OPM (optically pumped magnetometer) modules 1, multiple corrective magnetic sensors 2, a non-magnetic frame 3, a pair of geomagnetic field correction coils 6, a pair of geomagnetic field gradient correction coils 7, a pair of variable magnetic field correction coils 8, and a pair of variable magnetic field gradient correction coils 9, and an MRI module (MRI apparatus) having a transmitter coil 21, a receiver coil 22, an OPM module 23, and an output coil 24. The brain-measuring device M1 further includes a control device 4, a coil power supply 5, a pump laser 10, a probe laser 11, amplifiers 12A and 12B, a heater controller 13, an electromagnetic shield 14, and an excitation coil controller 15.

[0029] In the following description, the direction roughly parallel to the central axis of the subject's head is referred to as the Z-axis direction, and directions perpendicular to the Z-axis and perpendicular to each other are referred to as the X-axis and Y-axis directions.

[0030] The OPM module 1 includes an optically excited magnetic sensor 1 A, a heat insulating material 1 B, and a readout circuit 1 C. A plurality of OPM modules 1 are arranged at predetermined intervals along the measurement target (for example, the scalp).

[0031] The optically excited magnetic sensor 1A measures brain magnetic fields using optical pumping and has a sensitivity of, for example, approximately 10 fT to 10 pT. The heat insulating material 1B prevents heat transfer and heat transfer within the optically excited magnetic sensor 1A. The readout circuit 1C is a circuit that acquires the detection results of the optically excited magnetic sensor 1A. The optically excited magnetic sensor 1A excites the alkali metal by irradiating a cell containing alkali metal vapor with pump light. The excited alkali metal is spin-polarized, and when exposed to a magnetic field, the tilt of the spin polarization axis of the alkali metal atoms changes in response to the magnetic field. The tilt of this spin polarization axis is detected by probe light irradiated separately from the pump light. The optically excited magnetic sensor 1A is configured to apply a predetermined bias magnetic field in the direction of the pump light irradiation so that it is sensitive to magnetic fields with frequencies ranging from 0 to 200 Hz. The readout circuit 1C receives the probe light that has passed through the alkali metal vapor using a photodiode and acquires the detection results. The readout circuit 1C outputs the detection results to an amplifier 12A.

[0032] The optically excited magnetic sensor 1A may be, for example, an axial gradiometer. The axial gradiometer has a measurement region and a reference region that are aligned coaxially and perpendicular to the subject's scalp (measurement location). The measurement region is, for example, the location closest to the subject's scalp among the locations where the axial gradiometer measures the brain magnetic field. The reference region is, for example, the location at a predetermined distance (e.g., 3 cm) from the measurement region in the direction away from the subject's scalp among the locations where the axial gradiometer measures the brain magnetic field. The axial gradiometer outputs the measurement results from the measurement region and the reference region to the amplifier 12A. Here, if common mode noise is present, its influence is indicated in the output result from the measurement region and the output result from the reference region. The common mode noise is removed by obtaining the difference between the output result from the measurement region and the output result from the reference region. By removing the common mode noise, the optically excited magnetic sensor 1A can achieve a sensitivity of approximately 10 fT / √Hz when measuring in a magnetic noise environment of, for example, 1 pT.

[0033] The correcting magnetic sensor 2 measures the geomagnetism and the variable magnetic field at a position corresponding to the optically excited magnetic sensor 1A. The correcting magnetic sensor 2 is a fluxgate sensor with a sensitivity of, for example, several pT to 100 μT. The dynamic range of the fluxgate sensor can include the geomagnetism having an intensity on the order of 10 μT and the variable magnetic field of a specific frequency (for example, a commercial frequency of 50 Hz or 60 Hz) having an intensity on the order of 10 nT. The variable magnetic field of a specific frequency is a particularly strong variable magnetic field. The position corresponding to the optically excited magnetic sensor 1A is a position on the periphery (vicinity) of the area where the optically excited magnetic sensor 1A is arranged. The correcting magnetic sensors 2 may be provided in one-to-one correspondence with the optically excited magnetic sensors 1A, or in one-to-multiple correspondence (one correcting magnetic sensor 2 for multiple optically excited magnetic sensors 1A).

[0034] As shown in FIG. 2, the correction magnetic sensor 2 branches the geomagnetic and variable magnetic field measurements and outputs them to the control device 4. The correction magnetic sensor 2 outputs the geomagnetic measurement as a DC (direct current) component and the variable magnetic field measurement as an AC (alternating current) component. The wiring between the correction magnetic sensor 2 and the control device 4 branches to form lines L1 and L2. A capacitor C and an amplifier A are arranged on line L2, in descending order from the correction magnetic sensor 2 side. The capacitor C cuts (blocks) the DC component. The amplifier A amplifies the AC component, from which the DC component has been removed, from the output of the correction magnetic sensor 2. The DC component is output to the control device 4 via line L1. The AC component is amplified on line L2 and then output to the control device 4. Although the AC component remains on line L1, it is weaker than the DC component, so its effect on the DC component is negligible. Alternatively, a low-pass filter that blocks the AC component and passes only the DC component may be provided on line L1. Each measurement value of the correction magnetic sensor 2 can be represented by a vector having a direction and a magnitude in the control device 4. The control device 4 calculates the gradient of the geomagnetic field (hereinafter referred to as "geomagnetic gradient") based on the measurement values ​​of the geomagnetic field by the multiple correction magnetic sensors 2. The control device 4 also calculates the gradient of the variable magnetic field (hereinafter referred to as "variable magnetic field gradient") based on the measurement values ​​of the variable magnetic field by the multiple correction magnetic sensors 2. The correction magnetic sensor 2 may continuously perform measurement and output at predetermined time intervals.

[0035] Returning to FIG. 1 , the non-magnetic frame 3 is a frame that covers the entire scalp of the subject whose brain magnetic field is to be measured. It is made of a non-magnetic material, such as graphite, whose relative permeability is close to 1 and does not disturb the magnetic field distribution. The non-magnetic frame 3 may be, for example, a helmet-type frame that surrounds the entire scalp and is worn on the subject's head. Multiple optically excited magnetic sensors 1A are fixed to the non-magnetic frame 3 so that they are close to the subject's scalp. Furthermore, correction magnetic sensors 2 are fixed to the non-magnetic frame 3 so that they can measure the geomagnetic field and variable magnetic field at each of the multiple optically excited magnetic sensors 1A. Additionally, a receiver coil 22 is fixed to the scalp side of the multiple optically excited magnetic sensors 1A within the non-magnetic frame 3. This receiver coil 22 detects nuclear magnetic resonance signals for MR imaging. This receiver coil 22 detects and converts proton nuclear magnetic resonance signals (described later) into electric current. To improve the detection sensitivity of nuclear magnetic resonance signals, the receiver coil 22 is preferably located on the side of the optically excited magnetic sensor 1A closest to the scalp of the subject's head.

[0036] The transmission coil 21 is a coil that irradiates the subject's head with RF pulses (transmission pulses) of a predetermined frequency (e.g., about 300 kHz) during MR image measurement. This transmission coil 21 is placed, for example, outside the non-magnetic frame 3 and above the subject's head.

[0037] The output coil 24 is electrically connected to both ends of the receiving coil 22 via a cable, receives the current flowing between both ends of the receiving coil 22, converts the current back into a magnetic signal, and outputs it.

[0038] Like the OPM module 1, the OPM module 23 has an optically excited magnetic sensor 23A, a heat insulating material 23B, and a readout circuit 23C. The OPM module 23 is housed together with the output coil 24 in a magnetic shield 25 that shields against a static magnetic field, which will be described later, and is disposed, for example, outside the non-magnetic frame 3. The magnetic shield 25 is made of a material with a relative permeability greater than 1, such as mu metal.

[0039] The optically excited magnetic sensor 23A is a sensor that measures magnetic signals using optical pumping. The optically excited magnetic sensor 23A is configured so that a predetermined bias magnetic field is applied in the direction of irradiation with the pump light so that it is sensitive to magnetic fields with frequencies in the range of 20 kHz to 500 kHz. For example, a bias magnetic field of approximately 40 μT is applied so that it is sensitive to the 300 kHz frequency of electromagnetic waves emitted by protons. The readout circuit 23C outputs the detection result by the optically excited magnetic sensor 23A to the amplifier 12B.

[0040] 3 shows a specific example of the configuration of the OPM module 23. The optically excited magnetic sensor 23A includes a longitudinal cell 26 filled with a gas containing an alkali metal whose polarization direction changes depending on the magnetic field to be measured, a heater 27 that heats the entire cell 26 to a predetermined temperature (e.g., 180°C), a polarizing beam splitter 28, and a photodetector 29. Pump light LP is introduced from the outside into the cell 26 along the longitudinal direction, and probe light LB is branched and irradiated onto each of a plurality of intersection regions 26A (e.g., four) along a direction perpendicular to the longitudinal direction. The magnetic rotation angle of the probe light LB transmitted through these intersection regions 26A is detected by the polarizing beam splitters 28 and photodetectors 29 provided corresponding to each intersection region 26A. That is, the polarizing beam splitter 28 splits the probe light LB into two linearly polarized components that are orthogonal to each other, and the photodetector 29 detects the intensities of the two linearly polarized components using two built-in photodiodes (PDs) and detects the magnetic rotation angle of the probe light LB based on the ratio of the detected intensities. The OPM module 23 is further provided with a circuit board 30, and the magnetic rotation angle of the probe light LB detected for each intersection region 26A is output via a readout circuit 23C within this circuit board 30.

[0041] The output coil 24 is fixed in the magnetic shield 25 so as to face each intersection region 26A of the cells 26 of the OPM module 23 configured as described above. With this configuration, the electromagnetic field B INThe magnetic signal B generated by the output coil 24 based on OUT is detected based on the magnetic rotation angle of the probe light LB, which changes depending on the tilt of the spin polarization axis of the alkali metal atoms. Here, in the example of Fig. 3, the intersection region 26A is divided into four, but this may be changed to any number. Also, a plurality of cells 26 may be provided in parallel, and the intersection regions 26A may be arranged two-dimensionally (for example, 4 x 4 = 16).

[0042] Returning to FIG. 1 , when measuring the brain magnetic field, the control device 4 controls the current supplied to the correction coils based on the geomagnetic field measurement values ​​and the variable magnetic field measurement values ​​obtained by the multiple corrective magnetic sensors 2. That is, the control device 4 determines the current to be supplied to the correction coils based on the geomagnetic field measurement values ​​and the variable magnetic field measurement values ​​so as to generate a magnetic field that cancels out the geomagnetic field and the variable magnetic field, and outputs a control signal corresponding to the determined current to the coil power supply 5. The correction coils are coils for correcting the geomagnetic field and the variable magnetic field. The correction coils include a geomagnetic field correction coil 6, a geomagnetic gradient correction coil 7, a variable magnetic field correction coil 8, and a variable magnetic field gradient correction coil 9.

[0043] Specifically, the control device 4 determines the current for the geomagnetic correction coil 6 so that the average value of the geomagnetic field measured by the multiple correcting magnetic sensors 2 approaches zero (so that a magnetic field is generated that is opposite in direction to and has the same magnitude as the geomagnetic field at the position of the optically excited magnetic sensor 1A). The control device 4 outputs a control signal (a control signal for geomagnetic field correction) corresponding to the determined current for the geomagnetic correction coil 6 to the coil power supply 5.

[0044] The control device 4 also determines the current for the geomagnetic gradient correction coil 7 so that the deviation from the average value of the geomagnetic field measured by the correcting magnetic sensor 2 is minimized (as a result, a magnetic field is generated that is opposite to and has the same magnitude as the geomagnetic gradient at the position of the optically excited magnetic sensor 1A). The control device 4 outputs a control signal (a control signal for geomagnetic gradient correction) corresponding to the determined current for the geomagnetic gradient correction coil 7 to the coil power supply 5.

[0045] Furthermore, the control device 4 determines the current for the variable magnetic field correction coil 8 so that the average value of the measured values ​​of the variable magnetic field by the multiple corrective magnetic sensors 2 approaches zero (as a result, a magnetic field is generated that is opposite in direction to and has the same magnitude as the variable magnetic field at the position of the optically excited magnetic sensor 1A). The control device 4 outputs a control signal (a control signal for variable magnetic field correction) corresponding to the determined current for the variable magnetic field correction coil 8 to the coil power supply 5.

[0046] Furthermore, the control device 4 determines the current for the variable magnetic field gradient correction coil 9 so that the deviation from the average value of the measurement value of the variable magnetic field by the corrective magnetic sensor 2 is minimized (as a result, a magnetic field is generated that is opposite in direction to and has the same magnitude as the variable magnetic field gradient at the position of the optically excited magnetic sensor 1A).The control device 4 outputs a control signal (a control signal for variable magnetic field gradient correction) corresponding to the determined current for the variable magnetic field gradient correction coil 9 to the coil power supply 5.

[0047] Furthermore, the control device 4 obtains information about the magnetism detected by the optically excited magnetic sensor 1A using the signal output from the amplifier 12A. When the optically excited magnetic sensor 1A is an axial gradiometer, the control device 4 may remove common mode noise by obtaining the difference between the output result of the measurement region and the output result of the reference region. The control device 4 may also control the operation of the pump laser 10 and the probe laser 11, such as the irradiation timing and irradiation time.

[0048] Furthermore, during MR image measurement, the control device 4 determines the currents to be supplied to the geomagnetic correction coil 6 and the geomagnetic gradient correction coil 7, which operate as coils for applying a static magnetic field and a gradient magnetic field, respectively, and outputs a control signal for outputting the currents to the coil power supply 5. That is, the control device 4 determines the current to be passed through the geomagnetic correction coil 6 so as to apply a magnetic field in the X-axis direction of a predetermined strength (e.g., 7 mT) to the subject's head as a static magnetic field. Furthermore, the control device 4 selectively determines the X-axis magnetic field gradient (dBx / dX), the Y-axis magnetic field gradient (dBx / dY), and the Z-axis magnetic field gradient (dBx / dZ) as gradient magnetic fields, and determines the current to be passed through the geomagnetic gradient correction coil 7. This allows the position of a slice to be determined in the MR image, and the position within the slice plane to be encoded by phase encoding and frequency encoding. During MR image measurement, the control device 4 outputs a control signal so as not to supply current to the variable magnetic field correction coil 8 and the variable magnetic field gradient correction coil 9, which remove low-frequency noise.

[0049] Furthermore, when measuring an MR image, the control device 4 outputs a control signal to the excitation coil controller 15 to control the power supplied to the transmit coil 21, thereby controlling the excitation coil controller 15 to irradiate the subject's head with a transmit pulse of a predetermined frequency (for example, approximately 300 kHz when the static magnetic field strength is 7 mT). As a result, protons in the slice plane (the plane selected by the static magnetic field and the gradient magnetic field) resonate and the spins tilt. Thereafter, the control device 4 controls the power of the transmit coil 21 to be turned off. This makes it possible to acquire an MR image by measuring the return of the spins based on the output of the OPM module 23. More specifically, the control device 4 measures the nuclear magnetic resonance signals from the protons by encoding their positions with frequency and phase using a known spin echo sequence or gradient echo sequence, and converts the measurement results into an MR image using fast Fourier transform.

[0050] The control device 4 is physically configured to include memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. Examples of such a control device 4 include a personal computer, a cloud server, a smartphone, and a tablet terminal. The control device 4 functions by executing a program stored in the memory with the CPU of the computer system.

[0051] The coil power supply 5 outputs a predetermined current to each of the correction coils in response to a control signal output from the control device 4. Specifically, the coil power supply 5 outputs a current to the geomagnetic correction coil 6 in response to a control signal related to the geomagnetic correction coil 6. The coil power supply 5 outputs a current to the geomagnetic gradient correction coil 7 in response to a control signal related to the geomagnetic gradient correction coil 7. The coil power supply 5 outputs a current to the variable magnetic field gradient correction coil 8 in response to a control signal related to the variable magnetic field gradient correction coil 8. The coil power supply 5 outputs a current to the variable magnetic field gradient correction coil 9 in response to a control signal related to the variable magnetic field gradient correction coil 9.

[0052] The excitation coil controller 15 is electrically connected to the transmission coil 21, and supplies power to the transmission coil 21 in response to a control signal output from the control device 4 so as to irradiate a transmission pulse of a predetermined frequency.

[0053] The geomagnetic correction coil 6 is a coil for correcting the geomagnetic field at the position of the optically excited magnetic sensor 1A. The geomagnetic correction coil 6 generates a magnetic field in response to the current supplied from the coil power supply 5 to cancel the geomagnetic field. The geomagnetic correction coil 6 includes, for example, a pair of geomagnetic field correction coils 6A and 6B. The pair of geomagnetic field correction coils 6A and 6B are arranged on either side of the optically excited magnetic sensor 1A (for example, on the left and right sides of the subject). The pair of geomagnetic field correction coils 6A and 6B generate a magnetic field in the opposite direction to and of approximately the same magnitude as the geomagnetic field at the position of the optically excited magnetic sensor 1A in response to the current supplied from the coil power supply 5. The magnetic field direction is, for example, the X-axis direction, Y-axis direction, and Z-axis direction. The geomagnetic field at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field generated by the geomagnetic field correction coil 6 in the opposite direction and of approximately the same magnitude. In this way, the geomagnetic field correction coil 6 corrects the geomagnetic field at the position of the optically excited magnetic sensor 1A.

[0054] The geomagnetic correction coil 6 also serves as a static magnetic field coil for generating a static magnetic field in the X-axis direction during MR image measurement. The geomagnetic correction coil 6 generates a static magnetic field of a predetermined strength in response to the current supplied from the coil power supply 5.

[0055] The geomagnetic gradient correction coil 7 is a coil for correcting the geomagnetic gradient at the position of the optically excited magnetic sensor 1A. The geomagnetic gradient correction coil 7 generates a magnetic field in response to the current supplied from the coil power supply 5 to cancel the gradient. The geomagnetic gradient correction coil 7 includes, for example, a pair of geomagnetic gradient correction coils 7A and 7B. The pair of geomagnetic gradient correction coils 7A and 7B are arranged on either side of the optically excited magnetic sensor 1A (for example, on the left and right of the subject). The pair of geomagnetic gradient correction coils 7A and 7B generate a magnetic field in response to the current supplied from the coil power supply 5, the magnetic field being opposite in direction to and of approximately the same magnitude as the gradient at the position of the optically excited magnetic sensor 1A. The magnetic field direction is, for example, the X-axis direction, Y-axis direction, and Z-axis direction. The gradient at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field generated by the geomagnetic gradient correction coil 7, which is opposite in direction and of approximately the same magnitude. In this way, the geomagnetic gradient correction coil 7 corrects the gradient at the position of the optically excited magnetic sensor 1A.

[0056] The geomagnetic gradient correction coil 7 also serves as a gradient magnetic field coil for generating a gradient magnetic field during MR image measurement. The geomagnetic gradient correction coil 7 generates a gradient magnetic field having selective gradients in the X-axis, Y-axis, and Z-axis directions according to the current supplied from the coil power supply 5.

[0057] The variable magnetic field correction coil 8 is a coil for correcting a variable magnetic field at the position of the optically excited magnetic sensor 1A. The variable magnetic field correction coil 8 generates a magnetic field in response to the current supplied from the coil power supply 5, thereby canceling the variable magnetic field. The variable magnetic field correction coil 8 includes, for example, a pair of variable magnetic field correction coils 8A and 8B. The pair of variable magnetic field correction coils 8A and 8B are arranged on either side of the optically excited magnetic sensor 1A (for example, on the left and right of the subject). The pair of variable magnetic field correction coils 8A and 8B generate a magnetic field in the opposite direction to and of approximately the same magnitude as the variable magnetic field at the position of the optically excited magnetic sensor 1A in response to the current supplied from the coil power supply 5. The magnetic field direction is, for example, the X-axis direction, Y-axis direction, and Z-axis direction. The variable magnetic field at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field generated by the variable magnetic field correction coil 8 in the opposite direction and of approximately the same magnitude. In this way, the variable magnetic field correction coil 8 corrects the variable magnetic field at the position of the optically excited magnetic sensor 1A.

[0058] The variable magnetic field gradient correction coil 9 is a coil for correcting the variable magnetic field gradient at the position of the optically excited magnetic sensor 1A. The variable magnetic field gradient correction coil 9 generates a magnetic field in response to the current supplied from the coil power supply 5, thereby canceling the variable magnetic field gradient. The variable magnetic field gradient correction coil 9 includes, for example, a pair of variable magnetic field gradient correction coils 9A and 9B. The pair of variable magnetic field gradient correction coils 9A and 9B are arranged on either side of the optically excited magnetic sensor 1A (for example, on the left and right sides of the subject). The pair of variable magnetic field gradient correction coils 9A and 9B generate a magnetic field in the opposite direction and of approximately the same magnitude as the variable magnetic field gradient at the position of the optically excited magnetic sensor 1A in response to the current supplied from the coil power supply 5. The magnetic field direction is, for example, from one variable magnetic field gradient correction coil 9A to the other variable magnetic field gradient correction coil 9B. The variable magnetic field gradient at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field in the opposite direction and of approximately the same magnitude generated by the variable magnetic field gradient correction coil 9. In this way, the variable magnetic field gradient correction coil 9 corrects the variable magnetic field gradient at the position of the optically excited magnetic sensor 1A.

[0059] The pump laser 10 is a laser device that generates pump light. The pump light emitted from the pump laser 10 is incident on each of the plurality of optically excited magnetic sensors 1A and the optically excited magnetic sensor 23A via fiber branching.

[0060] The probe laser 11 is a laser device that generates probe light. The probe light emitted from the probe laser 11 is incident on each of the plurality of photoexcited magnetic sensors 1A and the photoexcited magnetic sensor 23A via a branched fiber.

[0061] The amplifier 12A is a device or circuit that amplifies the signal output from the OPM module 1 (specifically, the readout circuit 1C) and outputs it to the control device 4.

[0062] The amplifier 12B is a device or circuit that amplifies the signal output from the OPM module 23 (specifically, the readout circuit 23C) and outputs the amplified signal to the control device 4.

[0063] The heater controller 13 is a temperature control device connected to heaters for heating the cells of the photoexcited magnetic sensor 1A and the photoexcited magnetic sensor 23A, and to thermocouples (not shown) for measuring the temperatures of the respective cells. The heater controller 13 receives cell temperature information from the thermocouples, and adjusts the heating of the heater based on the temperature information to adjust the temperature of the cells.

[0064] The electromagnetic shield 14 is a shielding member that blocks high-frequency (e.g., 10 kHz or higher) electromagnetic noise and is made of, for example, a mesh woven with metal threads or a nonmagnetic metal plate such as aluminum. The electromagnetic shield 14 is arranged to surround the OPM modules 1 and 23, the transmitter coil 21, the receiver coil 22, the output coil 24, the corrective magnetic sensor 2, the nonmagnetic frame 3, the geomagnetic correction coil 6, the geomagnetic gradient correction coil 7, the variable magnetic field correction coil 8, and the variable magnetic field gradient correction coil 9. This electromagnetic shield 14 prevents noise in the 300 kHz band, which is the measurement frequency, from entering the receiver coil 22 during MR image measurement, which would increase the noise level. It also prevents high-frequency noise from entering the optically excited magnetic sensor 1A and causing unstable operation during brain magnetic field measurement.

[0065] Next, a brain-measuring method using the brain-measuring apparatus M1 according to the embodiment will be described with reference to Figures 4 and 5. Figures 4 and 5 are flowcharts showing the operation of the brain-measuring apparatus M1.

[0066] First, when measurement of the brain magnetic field is started with the non-magnetic frame 3 attached to the subject, the corrective magnetic sensors 2 measure the geomagnetic field (step S11). The corrective magnetic sensors 2 measure the geomagnetic field at each position of the optically excited magnetic sensors 1A and output the measured values ​​of the geomagnetic field to the control device 4. The control device 4 calculates the geomagnetic gradient based on the measured values ​​of the geomagnetic field by the multiple corrective magnetic sensors 2.

[0067] The control device 4 and the coil power supply 5 control the current to the geomagnetic correction coil 6 (step S12). Based on the geomagnetic field measured by the correction magnetic sensor 2, the control device 4 determines the current to be supplied to the geomagnetic correction coil 6 so as to generate a magnetic field of the same magnitude and in the opposite direction to the geomagnetic field at the position of the optically excited magnetic sensor 1A. More specifically, the control device 4 determines the current to be supplied to the geomagnetic correction coil 6 so that, for example, the average value of the geomagnetic field measured by the multiple correction magnetic sensors 2 approaches zero. The control device 4 outputs a control signal corresponding to the determined current to the coil power supply 5. The coil power supply 5 outputs a predetermined current to the geomagnetic correction coil 6 in response to the control signal output by the control device 4. The geomagnetic field 6 generates a magnetic field in response to the current supplied from the coil power supply 5. The geomagnetic field at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field generated by the geomagnetic correction coil 6, which is of the same magnitude and in the opposite direction.

[0068] The control device 4 and the coil power supply 5 control the current to the geomagnetic gradient correction coil 7 (step S13). Based on the geomagnetic field measured by the correcting magnetic sensor 2, the control device 4 determines the current to be supplied to the geomagnetic gradient correction coil 7 so as to generate a magnetic field of the same magnitude and in the opposite direction to the gradient at the position of the optically excited magnetic sensor 1A. More specifically, the control device 4 determines the current to be supplied to the geomagnetic gradient correction coil 7 so as to minimize the deviation from the average value of the geomagnetic field measured by the correcting magnetic sensor 2. The control device 4 outputs a control signal corresponding to the determined current to the coil power supply 5. The coil power supply 5 outputs a predetermined current to the geomagnetic gradient correction coil 7 in response to the control signal output by the control device 4. The geomagnetic gradient correction coil 7 generates a magnetic field in response to the current supplied from the coil power supply 5. The gradient at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field generated by the geomagnetic gradient correction coil 7 of the same magnitude and in the opposite direction.

[0069] The control device 4 determines whether the geomagnetic field measurement value after correction is equal to or less than the reference value (step S14). The geomagnetic field measurement value after correction is the geomagnetic field measurement value obtained by the correcting magnetic sensor 2 after the geomagnetic field has been corrected by the geomagnetic field correction coil 6 and the geomagnetic gradient correction coil 7. The reference value is the magnitude of the magnetic field at which the optically excited magnetic sensor 1A operates normally, and may be, for example, 1 nT. If the geomagnetic field measurement value is not equal to or less than the reference value ("NO" in step S14), the process returns to step S11. If the geomagnetic field measurement value is equal to or less than the reference value ("YES" in step S14), the process proceeds to step S15.

[0070] The corrective magnetic sensor 2 measures the fluctuating magnetic field (step S15). The corrective magnetic sensor 2 measures the fluctuating magnetic field at each position of the optically excited magnetic sensor 1A and outputs the measurement values ​​of the fluctuating magnetic field to the control device 4. The control device 4 calculates the gradient of the fluctuating magnetic field based on the measurement values ​​of the fluctuating magnetic field by the multiple corrective magnetic sensors 2.

[0071] The control device 4 and the coil power supply 5 control the current to the variable magnetic field correction coil 8 (step S16). Based on the measurement value of the variable magnetic field by the corrective magnetic sensor 2, the control device 4 determines the current to be supplied to the variable magnetic field correction coil 8 so as to generate a magnetic field of the same magnitude and in the opposite direction to the variable magnetic field at the position of the optically excited magnetic sensor 1A. More specifically, the control device 4 determines the current to be supplied to the variable magnetic field correction coil 8 so that, for example, the average value of the measurement values ​​of the variable magnetic field by the multiple corrective magnetic sensors 2 approaches zero. The control device 4 outputs a control signal according to the determined current to the coil power supply 5. The coil power supply 5 outputs a predetermined current to the variable magnetic field correction coil 8 in accordance with the control signal output by the control device 4. The variable magnetic field correction coil 8 generates a magnetic field in accordance with the current supplied from the coil power supply 5. The variable magnetic field at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field of the same magnitude and in the opposite direction generated by the variable magnetic field correction coil 8.

[0072] The control device 4 and the coil power supply 5 control the current to the variable magnetic field gradient correction coil 9 (step S17). Based on the variable magnetic field measured by the correcting magnetic sensor 2, the control device 4 determines the current to be supplied to the variable magnetic field gradient correction coil 9 so as to generate a magnetic field of the same magnitude and in the opposite direction to the variable magnetic field gradient at the position of the optically excited magnetic sensor 1A. More specifically, the control device 4 determines the current to be supplied to the variable magnetic field gradient correction coil 9 so as to minimize the deviation from the average value of the variable magnetic field measured by the correcting magnetic sensor 2. The control device 4 outputs a control signal corresponding to the determined current to the coil power supply 5. The coil power supply 5 outputs a predetermined current to the variable magnetic field gradient correction coil 9 in response to the control signal output by the control device 4. The variable magnetic field gradient correction coil 9 generates a magnetic field in response to the current supplied from the coil power supply 5. The variable magnetic field gradient at the position of the optically excited magnetic sensor 1A is canceled out by the magnetic field of the same magnitude and in the opposite direction generated by the variable magnetic field gradient correction coil 9.

[0073] The control device 4 determines whether the measured value of the variable magnetic field after correction is equal to or less than the reference value (step S18). The measured value of the variable magnetic field after correction is the measured value of the variable magnetic field by the corrective magnetic sensor 2 after the variable magnetic field has been corrected by the variable magnetic field correction coil 8. The reference value is the noise level at which the brain magnetic field can be measured, and can be, for example, less than 1 nT, more specifically, 10 pT. If the measured value of the variable magnetic field is not equal to or less than the reference value ("NO" in step S18), the process returns to step S15. If the measured value of the variable magnetic field is equal to or less than the reference value ("YES" in step S18), the process proceeds to step S19.

[0074] The optically excited magnetic sensor 1A measures the brain magnetic field (step S19). The control device 4 outputs the acquired measurement results to a predetermined output destination. The predetermined output destination may be the memory of the control device 4, a storage device such as a hard disk, an output device such as a display, or an external device such as a terminal device connected via a communication interface. Since the geomagnetic field and the fluctuating magnetic field at the position of the optically excited magnetic sensor 1A have been canceled out so that they are below predetermined reference values, the optically excited magnetic sensor 1A can measure the brain magnetic field while avoiding the influence of the geomagnetic field and the fluctuating magnetic field.

[0075] 5, when MR image measurement is initiated while the non-magnetic frame 3 is still attached to the subject, the control device 4 determines the current to be supplied to the geomagnetic correction coil 6 for applying a static magnetic field and outputs a control signal to the coil power supply 5 to control the generation of a static magnetic field in the X-axis direction at the subject's head (step S20). Next, the control device 4 determines the current to be supplied to the geomagnetic gradient correction coil 7 for generating a gradient magnetic field and outputs a control signal to the coil power supply 5 to control the generation of the X-axis magnetic field gradient (dBx / dX) (step S21). At the same time, the control device 4 outputs a control signal to the excitation coil controller 15 to control the power to be supplied to the transmission coil 21, thereby controlling the transmission pulse to be irradiated onto the subject's head (step S22). This excites protons in a predetermined slice plane.

[0076] Furthermore, the control device 4 determines the current to be supplied to the geomagnetic gradient correction coil 7 for generating the gradient magnetic field, and outputs a control signal to the coil power supply 5, thereby controlling the generation of the Y-axis magnetic field gradient (dBx / dY) on the slice surface (step S23). This performs phase encoding. The control device 4 then determines the current to be supplied to the geomagnetic gradient correction coil 7 for generating the gradient magnetic field, and outputs a control signal to the coil power supply 5, thereby controlling the generation of the Z-axis magnetic field gradient (dBx / dZ) on the slice surface (step S24). This performs frequency encoding.

[0077] At the same time, the OPM module 23 detects nuclear magnetic resonance signals from the protons via the receiver coil 22 and the output coil 24 and outputs the detection result, and the control device 4 acquires nuclear magnetic resonance signal data accordingly (step S25). Thereafter, the control device 4 determines whether to acquire nuclear magnetic resonance signal data for other slice planes (step S26). If the determination result indicates that nuclear magnetic resonance signal data for other slice planes will be acquired ("YES" in step S26), the process returns to step S21. On the other hand, if nuclear magnetic resonance signal data for other slice planes will not be acquired ("NO" in step S26), an MR image is acquired by Fourier transforming the nuclear magnetic resonance signal data acquired up to that point (step S27). The control device 4 outputs the acquired MR image to a predetermined output destination. The predetermined output destination may be the memory of the control device 4, a storage device such as a hard disk, an output device such as a display, or an external device such as a terminal device connected via a communication interface.

[0078] 6 is a schematic diagram showing the configuration of a brain-measuring device M2 according to another embodiment. The brain-measuring device M2 differs from the brain-measuring device M1 in that the receive coil 22 is omitted. Furthermore, the brain-measuring device M2 includes a transmit / receive switch SW. In the brain-measuring device M2, the transmit coil 21A is a transmit / receive coil that serves both as a transmit coil for transmitting transmit pulses and as a receive coil for detecting nuclear magnetic resonance signals. In other words, the transmit coil 21A also serves as the receive coil 22.

[0079] The transmit / receive switch SW is electrically connected to the excitation coil controller 15 and the transmitting coil 21A via a wire connecting the excitation coil controller 15 and the transmitting coil 21A. The transmit / receive switch SW is also electrically connected to the output coil 24 via a wire. The transmit / receive switch SW switches the connection destination of the transmitting coil 21A between the excitation coil controller 15 and the output coil 24. Specifically, when the transmit / receive switch SW is switched to the excitation coil controller 15 side, the transmit / receive switch SW electrically connects the excitation coil controller 15 and the transmitting coil 21A. On the other hand, when the transmit / receive switch SW is switched to the output coil 24 side, the transmit / receive switch SW electrically connects the transmitting coil 21A and the output coil 24. The setting of the transmit / receive switch SW is changed by the control device 4.

[0080] When the transmission / reception switch SW is switched to the excitation coil controller 15 side, the excitation coil controller 15 is electrically connected to the transmission coil 21A via the transmission / reception switch SW. The excitation coil controller 15 supplies power (current C1) to the transmission coil 21A so as to irradiate a transmission pulse of a predetermined frequency in accordance with a control signal output from the control device 4. Thereafter, the control device 4 controls the power of the transmission coil 21A to be turned off, and switches the transmission / reception switch SW to the output coil 24 side.

[0081] When the transmit / receive switch SW is switched to the output coil 24 side, the transmit coil 21A is electrically connected to the output coil 24 via the transmit / receive switch SW. The transmit coil 21A detects nuclear magnetic resonance signals of protons and converts them into a current C2. The transmit coil 21A outputs the current C2 to the output coil 24. The output coil 24 receives the current C2 from the transmit coil 21A, converts the current C2 back into a magnetic signal, and outputs it.

[0082] 7 is a schematic diagram showing the configuration of a brain-measuring device M3 according to another embodiment. The brain-measuring device M3 includes a transmitting coil 21B as a transmitting / receiving coil instead of the transmitting coil 21A in the brain-measuring device M2. The transmitting coil 21B is formed in a spiral shape and is arranged so as to surround the measurement subject. The transmitting coil 21B is fixed, for example, to the scalp side of the subject inside the non-magnetic frame 3. The transmitting coil 21B has the same function as the transmitting coil 21A in the brain-measuring device M2.

[0083] Next, a brain measurement method using the brain-measuring device M2 or M3 according to the embodiment will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the operation of the brain-measuring device M2 or M3. The operation of the brain-measuring device M2 or M3 when measuring a brain magnetic field is the same as that of the brain-measuring device M1, and therefore a description thereof will be omitted. Only the differences from the operation of the brain-measuring device M1 will be described.

[0084] Simultaneously with the processing of step S21, the control device 4 switches the transmission / reception switch SW to the excitation coil controller 15 side, and outputs a control signal to the excitation coil controller 15 to control the power (current C1) supplied for transmission and reception, thereby controlling the transmission pulse to be irradiated onto the subject's head (step S32). This excites protons on a predetermined slice plane.

[0085] Simultaneously with the processing of step S24, the control device 4 switches the transmitting / receiving switch SW to the side of the output coil 24. The detection result of the nuclear magnetic resonance signal from the protons is output from the OPM module 23 via the transmitting / receiving coil and the output coil 24, and accordingly the control device 4 acquires data of the nuclear magnetic resonance signal (step S35). [Action and effect] Next, the effects of the brain-measuring apparatus according to the above-described embodiment will be described.

[0086] According to the brain-measuring devices M1, M2, and M3 of this embodiment, the geomagnetic field and the variable magnetic field are measured at the respective positions of the multiple optically excited magnetic sensors 1A that measure the brain magnetic field. Then, when measuring the brain magnetic field, the current flowing through the correction coil is controlled based on the measured values ​​of the geomagnetic field and the variable magnetic field, and a magnetic field is generated in the correction coil. As a result, the geomagnetic field and the variable magnetic field are corrected by the magnetic field generated in the correction coil at the positions of the multiple optically excited magnetic sensors 1A. By correcting the geomagnetic field and the variable magnetic field at the positions of the multiple optically excited magnetic sensors 1A, the multiple optically excited magnetic sensors 1A can measure the brain magnetic field while avoiding the influence of the geomagnetic field and the variable magnetic field.

[0087] On the other hand, according to the above one or other aspects, when measuring an MR image, a static magnetic field and a gradient magnetic field are applied by controlling the currents flowing through the geomagnetic correction coil 6 (static magnetic field coil) and the geomagnetic gradient correction coil 7 (gradient magnetic field coil), and a nuclear magnetic resonance signal generated by transmitting a transmission pulse is detected. As a result, an MR image can be measured based on the output of the transmitting and receiving coils.

[0088] This brain measurement device and method enable efficient implementation of both MEG and MRI measurements using the same device. In particular, the use of an optically excited magnetic sensor in MRI measurements allows for a wider frequency band of sensitivity than SQUIDs, thereby reducing limitations on the strength of the applied static magnetic field, i.e., the proton resonance frequency. This eliminates the need for prepolarization coils, which are necessary because SQUIDs operate only at low resonance frequencies, i.e., low static magnetic fields, and also eliminates the need for coolants such as liquid helium, which are required when using SQUIDs. Furthermore, because the frequency of the signals measured in MRI is relatively high, a magnetically shielded room is not required to reduce magnetic noise during MRI and MEG measurements. This results in a smaller and less costly device. In addition, because the time required for prepolarization is roughly the same as the measurement time, this embodiment can shorten the measurement time by half.

[0089] Furthermore, in this embodiment, the static magnetic field can be easily turned on and off by turning on and off the current flowing through the geomagnetic correction coil 6, so that it is possible to switch between the brain magnetic field measurement and the MRI measurement in a short time. This allows the brain magnetic field measurement and the MRI measurement to be performed sequentially on the same subject using the same device, thereby reducing registration errors in the results of both measurements.

[0090] As described above, according to this embodiment, MRI measurement can be performed in a low magnetic field, eliminating the need for a special room and enhancing the T1 contrast. Furthermore, by using the variable magnetic field correction coil 8, it is not necessary to perform MEG measurement in a magnetically shielded room. Therefore, MEG measurement and MRI measurement can be performed using the same device, and both measurements can be performed sequentially while the subject is seated in a chair or similar. Furthermore, the cost of the device can be reduced, and measurements can be performed while the subject is seated in a vehicle or similar. As a result, this can contribute to the diagnosis of psychiatric disorders such as depression and schizophrenia, as well as neurodegenerative disorders such as dementia.

[0091] Here, the brain-measuring device M1 uses a geomagnetic correction coil 6 for applying a static magnetic field and a geomagnetic gradient correction coil 7 for applying a gradient magnetic field. This allows the geomagnetic correction coil for magnetoencephalography measurement and the coil for MRI measurement to be shared, thereby enabling further miniaturization and cost reduction of the device.

[0092] Furthermore, in this embodiment, during brain magnetic field measurement, the geomagnetic field and the variable magnetic field are canceled out at the positions of the multiple optically excited magnetic sensors 1A, so that the multiple optically excited magnetic sensors 1A can measure the brain magnetic field while reliably avoiding the influence of the geomagnetic field and the variable magnetic field. As a result, the brain magnetic field can be measured with high accuracy without using a magnetically shielded room. This effect can be achieved even if the subject's head moves.

[0093] The correction coils include a geomagnetic correction coil 6 for correcting the geomagnetic field and a variable magnetic field correction coil 8 for correcting the variable magnetic field. Based on the measured geomagnetic field, the control device 4 determines the current to be applied to the geomagnetic correction coil 6 so as to generate a magnetic field that cancels out the geomagnetic field, and based on the measured variable magnetic field, determines the current to be applied to the variable magnetic field correction coil 8 so as to generate a magnetic field that cancels out the variable magnetic field. In this configuration, the geomagnetic correction coil 6 and the static magnetic field coil can be used in some cases, which enables further miniaturization and cost reduction of the device. With this configuration, brain magnetic fields can be measured with high accuracy without using a magnetically shielded room.

[0094] The correction coil includes a geomagnetic gradient correction coil 7 for correcting the geomagnetic gradient. The control device determines the current to be applied to the geomagnetic gradient correction coil 7 based on the measured geomagnetic field so as to generate a magnetic field that cancels out the geomagnetic gradient. In this configuration, the geomagnetic gradient correction coil 7 and the gradient magnetic field coil can be used in common in some cases, which enables further miniaturization and cost reduction of the device. Furthermore, uniform magnetic field correction (zeroth-order correction) is performed by controlling the current to the correction coil. Furthermore, correction of the geomagnetic gradient (first-order correction) is performed by controlling the current to the geomagnetic gradient correction coil 7, taking into account the difference in the positions of the optically excited magnetic sensors 1A. In this way, the geomagnetic field and its gradient are canceled out in stages, allowing for accurate correction of the geomagnetic field.

[0095] The correction coils include variable magnetic field gradient correction coils 9 for correcting the gradient of the variable magnetic field. Based on the measured value of the variable magnetic field, the control device 4 may determine the current to be applied to the variable magnetic field gradient correction coils 9 so as to generate a magnetic field that cancels out the gradient of the variable magnetic field. In this case, uniform variable magnetic field correction (zeroth-order correction) is performed by controlling the current to the correction coils, and further, correction of the gradient of the variable magnetic field (first-order correction) is performed by controlling the current to the variable magnetic field gradient correction coils 9, taking into account the difference in position of each optically excited magnetic sensor 1A. In this way, the variable magnetic field and the gradient of the variable magnetic field are canceled out in stages, allowing the variable magnetic field to be corrected with high accuracy.

[0096] The correction coil is composed of a pair of coils arranged on either side of the multiple optically excited magnetic sensors 1A. In this case, the geomagnetism and the fluctuating magnetic field at the positions of the multiple optically excited magnetic sensors 1A sandwiched between the pair of correction coils are effectively corrected. This allows the geomagnetism and the fluctuating magnetic field to be appropriately corrected with a simple configuration.

[0097] The corrective magnetic sensor 2 is a fluxgate sensor that outputs a measurement value of the geomagnetic field as a DC component and a measurement value of a fluctuating magnetic field as an AC component. The dynamic range of the fluxgate sensor can include a geomagnetic field having a strength on the order of 10 μT and a fluctuating magnetic field of a specific frequency (e.g., a commercial frequency) having a strength on the order of 10 nT. The fluctuating magnetic field of the specific frequency is a particularly strong magnetic field among fluctuating magnetic fields. Such a fluxgate sensor can suitably measure the geomagnetic field and the fluctuating magnetic field of the specific frequency.

[0098] The brain-measuring device M1 has a transmitting coil 21 that transmits a transmission pulse and a receiving coil 22 that detects a nuclear magnetic resonance signal. In this case, the receiving coil 22 can be placed in a location close to the measurement object, and the transmitting coil 21 can be placed in a location different from the receiving coil 22, for example, improving the degree of freedom in design. Furthermore, when a plurality of small receiving coils 22 are placed to surround the measurement object, it is possible to improve the sensitivity of the receiving coils 22 and reduce noise.

[0099] The transmit / receive coils of the brain-measuring devices M2 and M3 serve both as a coil for transmitting transmit pulses and a coil for detecting nuclear magnetic resonance signals, which enables further miniaturization and cost reduction of the devices.

[0100] The transmit / receive coil (transmit coil 21B) is formed in a spiral shape and is arranged to surround the object to be measured. In this case, the transmit / receive coil can be arranged in a location close to the object to be measured, thereby improving the accuracy of MRI measurement.

[0101] The multiple optically excited magnetic sensors 1A are axial gradiometers with a measurement area and a reference area aligned coaxially and perpendicular to the object to be measured. In this case, the influence of common mode noise is reflected in both the output results of the measurement area and the output results of the reference area, and common mode noise can be removed by obtaining the difference between the two output results. This improves the measurement accuracy of the brain magnetic field.

[0102] The brain-measuring device M1 is electrically connected to the transmitting coil 21, and the brain-measuring devices M2 and M3 are electrically connected to the transmitting and receiving coils (transmitting coils 21A and 21B, respectively). The brain-measuring devices M1 and M3 further include an output coil 24 that outputs a magnetic signal based on the current flowing through the receiving coil 22 or the transmitting and receiving coil, and another optically excited magnetic sensor 23A that detects the magnetic signal output by the output coil 24. The control device 4 of the brain-measuring devices M1, M2, and M3 generates an MR image based on the magnetic signal detected by the other optically excited magnetic sensor 23A. With this configuration, signals can be received by the other optically excited magnetic sensor 23A, which has high sensitivity on the order of fT, thereby improving the accuracy of MR image measurement. Furthermore, since the other optically excited magnetic sensor 23A is located away from the transmitting coil to which a static magnetic field on the order of mT is applied, the sensitivity band of the sensor can be adjusted without being affected by the static magnetic field.

[0103] The optically excited magnetic sensors 1A are configured to have a bias magnetic field applied thereto so that they are sensitive to frequencies in the range of 0 to 200 Hz. Another optically excited magnetic sensor 23A is configured to have a bias magnetic field applied thereto so that it is sensitive to frequencies in the range of 20 kHz to 500 kHz. This configuration can increase the sensitivity of brain magnetic field measurement while also improving the accuracy of MRI measurement.

[0104] Furthermore, the multiple optically excited magnetic sensors 1A, the multiple corrective magnetic sensors 2, and the receiving coil 22 are fixed to a helmet-type non-magnetic frame 3 that is worn on the head of the subject. With this configuration, the non-magnetic frame 3 worn on the head and the corrective magnetic sensors 2 and receiving coil 22 fixed to the non-magnetic frame 3 move in accordance with the movement of the subject's head, so that even when the subject's head moves, it is possible to appropriately correct the geomagnetic field and variable magnetic field at the positions of the multiple optically excited magnetic sensors 1A, measure the brain magnetic field, and perform MRI measurement. As a result, registration errors in both measurements can be reduced.

[0105] Furthermore, the brain-measuring devices M1, M2, and M3 further include an electromagnetic shield 14 for blocking high-frequency electromagnetic noise. With this configuration, high-frequency electromagnetic noise that is not the target of measurement by the magnetoencephalograph can be prevented from entering the multiple optically excited magnetic sensors 1A. This allows the multiple optically excited magnetic sensors 1A to stably measure the brain magnetic field. At the same time, it is possible to prevent noise in the 300 kHz band, which is the measurement frequency of MRI, from entering the receiving coil 22 and increasing the noise in the MRI measurement. [Variations] The present disclosure has been described in detail above based on the embodiments. However, the present disclosure is not limited to the above embodiments. Various modifications can be made to the present disclosure without departing from the spirit and scope of the present disclosure.

[0106] In the embodiment, the correction magnetic sensor 2 is configured to branch the measurement value and output it to the control device 4, but the correction magnetic sensor 2 may be configured to output the measurement value to the control device 4 without branching it. In such a configuration, the control device 4 may extract a DC component and an AC component based on the measurement value output from the correction magnetic sensor 2 and acquire the respective components as a measurement value of the geomagnetism and a measurement value of the varying magnetic field. In this case, the wiring for branching can be omitted.

[0107] The corrective magnetic sensor 2 may be a fluxgate sensor that measures the geomagnetism and an optically excited magnetic sensor that measures the fluctuating magnetic field. The optically excited magnetic sensor is a different sensor from the optically excited magnetic sensor 1A that measures the brain magnetic field. The optically excited magnetic sensor has higher sensitivity than a fluxgate sensor or the like, and can measure the fluctuating magnetic field with high accuracy. As a result, the fluctuating magnetic field and the fluctuating magnetic field gradient can be corrected more precisely.

[0108] Although the geomagnetic correction coil 6 has been described as including a pair of geomagnetic correction coils 6A and 6B, it may also be arranged as a three-coil system for each OPM module 1 (optically excited magnetic sensor 1A). In this case, the control device 4 determines the current for the geomagnetic correction coil 6 so as to generate a magnetic field of approximately the same magnitude and in the opposite direction to the three components (x-axis, y-axis, and z-axis) of the geomagnetic field at the position of the optically excited magnetic sensor 1A. The control device 4 outputs a control signal corresponding to the determined current for each of the geomagnetic correction coils 6 arranged as a three-coil system to the coil power supply 5. With this configuration, the power consumption for correcting the geomagnetic field can be relatively small.

[0109] Although the variable magnetic field correction coils 8 have been described as including a pair of variable magnetic field correction coils 8A and 8B, they may be arranged as a three-coil system for each OPM module 1 (optically excited magnetic sensor 1A). In this case, the control device 4 determines the current for the variable magnetic field correction coils 8 so as to generate a magnetic field of approximately the same magnitude and in the opposite direction to the three-directional (x-axis, y-axis, and z-axis) components of the variable magnetic field at the position of the optically excited magnetic sensor 1A. The control device 4 outputs a control signal corresponding to the determined current for each of the variable magnetic field correction coils 8 arranged as a three-coil system to the coil power supply 5. With this configuration, the power consumption for correcting the variable magnetic field can be made relatively small.

[0110] The optically excited magnetic sensor 1A may have multiple measurement points within one housing, which allows the distance between the measurement points to be narrowed, enabling the brain magnetic field to be measured with high spatial resolution.

[0111] Furthermore, the control device 4 may set the current flowing through the geomagnetic gradient correction coil 7 so as to correct the geomagnetic gradient when measuring MR images, or may set it so as not to correct the geomagnetic gradient. Because the magnitude of the gradient magnetic field is about several μT, which is about two orders of magnitude smaller than the static magnetic field, high accuracy can be maintained when acquiring MR images without performing correction.

[0112] Furthermore, the brain-measuring device M1 of the above embodiment may be configured so that the optically excited magnetic sensor 23A is omitted, and the control device 4 directly detects the output from the receiving coil 22 via an amplifier.

[0113] Furthermore, the optically excited magnetic sensor 1A is not limited to a pump-and-probe type that uses pump light and probe light, but may be a zero-field type optically excited magnetic sensor that uses circularly polarized light that serves as both pump light and probe light. In this zero-field type, light is irradiated onto the cell and a periodic bias magnetic field is applied to perform lock-in detection of the magnetic field, and the deviation from the zero magnetic field can be measured as the brain magnetic field.

[0114] Furthermore, in the brain-measuring device M1 of the above embodiment, the position of the non-magnetic frame 3 may be optically measurable. For example, markers may be attached to the lower end of the non-magnetic frame 3 at 120-degree intervals around the circumference, and a camera facing the non-magnetic frame 3 may be provided to measure helmet positional fluctuations. These measurement results can be used during MRI measurement. For example, the control device 4 can use the measurement results to calculate the relative position of the geomagnetic gradient correction coil 7 and the receiver coil 22 and calibrate the MR image. As a result, high-resolution MR images can be obtained even if the subject's head moves. This configuration is useful for MRI measurement of subjects whose heads are difficult to fix, such as young children. Note that during MEG measurement, even if the head position is shifted, the magnetic field at the position of the optically excited magnetic sensor 1A is corrected to zero, so there is little need to measure the position of the non-magnetic frame 3. However, position information about the non-magnetic frame 3 may be used to generate a zero magnetic field.

[0115] 9 to 11 are diagrams showing brain-measuring devices M4 to M6 according to modifications. The brain-measuring devices M4 to M6 differ from the brain-measuring devices M1 to M3, respectively, in that the variable magnetic field correction coil 8 and the variable magnetic field gradient correction coil 9 are omitted. The geomagnetic field correction coil 6 may correct the geomagnetic field with a DC current and also correct the variable magnetic field by superimposing an AC current component. That is, the geomagnetic field correction coil 6 may also function as the variable magnetic field correction coil 8. Similarly, the geomagnetic field gradient correction coil 7 may correct the magnetic field gradient with a DC current and also correct the variable magnetic field gradient by superimposing an AC current component. That is, the geomagnetic field gradient correction coil 7 may also function as the variable magnetic field gradient correction coil 9. For the same reasons as the brain-measuring devices M1 to M3, such brain-measuring devices M4 to M6 can efficiently perform MEG measurement and MRI measurement using the same device. Furthermore, since an increase in the number of correction coils can be suppressed, the geomagnetic field and variable magnetic field can be appropriately corrected with a simple configuration. [Explanation of symbols]

[0116] M1 to M6...brain measurement device, 1A, 23A...optically excited magnetic sensor, 2...correction magnetic sensor, 3...non-magnetic frame, 4...control device, 5...coil power supply, 6...geomagnetic correction coil, 7...geomagnetic gradient correction coil, 8...variable magnetic field correction coil, 9...variable magnetic field gradient correction coil, 14...electromagnetic shield, 21, 21A, 21B...transmitting coil, 22...receiving coil, 24...output coil.

Claims

1. a plurality of optically excited magnetic sensors for measuring brain magnetic fields; a plurality of correcting magnetic sensors for measuring the geomagnetism and the fluctuating magnetic field at the respective positions of the plurality of optically excited magnetic sensors; a magnetoencephalograph having a correction coil for correcting the geomagnetism and the fluctuating magnetic field; a static magnetic field coil for applying a static magnetic field; a gradient coil for applying a gradient magnetic field; a transmission / reception coil that transmits a transmission pulse of a predetermined frequency and detects a nuclear magnetic resonance signal generated by the transmission of the transmission pulse; an output coil electrically connected to the transmitting / receiving coil, which outputs a magnetic signal based on a current flowing in the transmitting / receiving coil; an MRI apparatus having another optically excited magnetic sensor housed in a magnetic shield together with the output coil and configured to detect the magnetic signal output by the output coil; an electromagnetic shield for blocking high-frequency electromagnetic noise; When measuring the brain magnetic field, the current supplied to the correction coil is controlled based on the measurement values ​​of the geomagnetic field and the measurement values ​​of the fluctuating magnetic field obtained by the plurality of corrective magnetic sensors; a control device that controls the static magnetic field and the gradient magnetic field by controlling currents supplied to the static magnetic field coil and the gradient magnetic field coil when measuring an MR image, and generates an MR image based on the magnetic signal detected by the other optically excited magnetic sensor; No magnetically shielded room Brain measurement device.

2. the correction coils include a geomagnetic correction coil for correcting the geomagnetic field and a variable magnetic field correction coil for correcting the variable magnetic field, the control device determines a current for the geomagnetic correction coil based on the measurement value of the geomagnetic field so as to generate a magnetic field that cancels out the geomagnetic field, and determines a current for the variable magnetic field correction coil based on the measurement value of the variable magnetic field so as to generate a magnetic field that cancels out the variable magnetic field. The brain measuring apparatus according to claim 1 .

3. the correction coil includes a geomagnetic gradient correction coil for correcting the gradient of the geomagnetic field, the control device determines, based on the measured value of the geomagnetic field, a current for the geomagnetic gradient correction coil so as to generate a magnetic field that cancels the gradient of the geomagnetic field. The brain measuring apparatus according to claim 1 or 2.

4. the correction coil includes a variable magnetic field gradient correction coil for correcting the gradient of the variable magnetic field, the control device determines, based on the measurement value of the variable magnetic field, a current for the variable magnetic field gradient correction coil so as to generate a magnetic field that cancels the gradient of the variable magnetic field. The brain measuring apparatus according to any one of claims 1 to 3.

5. 5. The brain measuring apparatus according to claim 1, wherein the correction coil is composed of a pair of coils arranged to sandwich the plurality of optically excited magnetic sensors.

6. The brain measuring device according to any one of claims 1 to 5, wherein the corrective magnetic sensor is a fluxgate sensor that outputs the measurement value of the geomagnetic field as a DC component and outputs the measurement value of the fluctuating magnetic field as an AC component.

7. 7. The brain measuring device according to claim 1, wherein the transmission / reception coil comprises a transmission coil that transmits the transmission pulse and a reception coil that detects the nuclear magnetic resonance signal.

8. 7. The brain measuring device according to claim 1, wherein the transmission / reception coil serves both as a coil for transmitting the transmission pulse and as a coil for detecting the nuclear magnetic resonance signal.

9. The brain measurement apparatus according to claim 8 , wherein the transmit / receive coil is formed in a spiral shape and is disposed so as to surround the measurement subject.

10. 10. The brain measurement device according to claim 1, wherein the plurality of optically excited magnetic sensors are axial gradiometers having a measurement region and a reference region coaxially in a direction perpendicular to the object to be measured.

11. the plurality of optically excited magnetic sensors are configured to have a bias magnetic field applied thereto so as to have sensitivity to frequencies in the range of 0 to 200 Hz; The other optically excited magnetic sensor is configured to have a bias magnetic field applied thereto so as to have sensitivity to frequencies in the range of 20 kHz to 500 kHz. The brain measuring apparatus according to any one of claims 1 to 10.

12. 8. The brain measurement apparatus according to claim 7, wherein the plurality of optically excited magnetic sensors, the plurality of corrective magnetic sensors, and the receiving coil are fixed to a helmet-type non-magnetic frame that is worn on the head of the subject.

13. a plurality of optically excited magnetic sensors for measuring brain magnetic fields; a plurality of correcting magnetic sensors for measuring the geomagnetism and the fluctuating magnetic field at the respective positions of the plurality of optically excited magnetic sensors; a magnetoencephalograph having a correction coil for correcting the geomagnetism and the fluctuating magnetic field; a static magnetic field coil for applying a static magnetic field; a gradient coil for applying a gradient magnetic field; a transmission / reception coil that transmits a transmission pulse of a predetermined frequency and detects a nuclear magnetic resonance signal generated by the transmission of the transmission pulse; an output coil electrically connected to the transmitting / receiving coil, which outputs a magnetic signal based on a current flowing in the transmitting / receiving coil; an MRI apparatus having another optically excited magnetic sensor housed in a magnetic shield together with the output coil and configured to detect the magnetic signal output by the output coil; A brain measurement method using an electromagnetic shield for blocking high-frequency electromagnetic noise and not using a magnetically shielded room, When measuring the brain magnetic field, the current supplied to the correction coil is controlled based on the measurement values ​​of the geomagnetic field and the measurement values ​​of the fluctuating magnetic field obtained by the plurality of corrective magnetic sensors; When measuring an MR image, the static magnetic field and the gradient magnetic field are controlled by controlling the currents supplied to the static magnetic field coil and the gradient magnetic field coil, and an MR image is generated based on the magnetic signal detected by the separate optically excited magnetic sensor. Brain measurement methods.

14. the correction coils include a geomagnetic correction coil for correcting the geomagnetic field and a variable magnetic field correction coil for correcting the variable magnetic field, determining a current for the geomagnetic correction coil based on the measured value of the geomagnetic field so as to generate a magnetic field that cancels out the geomagnetic field, and determining a current for the variable magnetic field correction coil based on the measured value of the variable magnetic field so as to generate a magnetic field that cancels out the variable magnetic field; The brain measurement method according to claim 13.

15. the correction coil includes a geomagnetic gradient correction coil for correcting the gradient of the geomagnetic field, determining, based on the measured geomagnetic field, a current for the geomagnetic gradient correction coil so as to generate a magnetic field that cancels the gradient of the geomagnetic field; The brain measurement method according to claim 13 or 14.

16. the correction coil includes a variable magnetic field gradient correction coil for correcting the gradient of the variable magnetic field, determining, based on the measured value of the variable magnetic field, a current for the variable magnetic field gradient correction coil so as to generate a magnetic field that cancels the gradient of the variable magnetic field; The brain measurement method according to any one of claims 13 to 15.

17. The brain measurement method according to any one of claims 13 to 16, wherein the corrective magnetic sensor is a fluxgate sensor that outputs the measurement value of the geomagnetic field as a DC component and the measurement value of the fluctuating magnetic field as an AC component.

18. The brain measurement method according to any one of claims 13 to 17, wherein the transmission / reception coil has a transmission coil that transmits the transmission pulse and a reception coil that detects the nuclear magnetic resonance signal.

19. The brain measurement method according to any one of claims 13 to 17, wherein the transmission / reception coil serves both as a coil for transmitting the transmission pulse and as a coil for detecting the nuclear magnetic resonance signal.

20. 20. The brain measurement method according to claim 19, wherein the transmit / receive coil is formed in a spiral shape and is arranged so as to surround the measurement subject.

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