Method and system for magnetic field timing control of ulf-mri and opm-meg

Abstract

The application relates to a magnetic field timing control method and system of ULF-MRI and OPM-MEG. The method comprises the following steps: performing magnetic field initialization on a brain imaging device in a magnetic shielding environment, so that an OPM-MEG sensor array works in a near-zero magnetic field state; a first time interval is used for applying a pre-polarization magnetic field, so that a target imaging area enters a polarization enhancement state; a second time interval is used for terminating the pre-polarization magnetic field, so that the target imaging area enters a magnetic field decay state; a third time interval is used for applying a measurement magnetic field and a gradient magnetic field, so that the target imaging area enters an imaging magnetic field state, and ULF-MRI structural imaging signals are collected; after the collection is completed, a fourth time interval is used for stopping the gradient magnetic field switching and maintaining the measurement magnetic field, so that the target imaging area returns to the near-zero magnetic field state, and OPM-MEG brain magnetic signals are collected. The application solves the problem that ULF-MRI and OPM-MEG cannot be compatibly and cooperatively operated in a unified magnetic environment in the prior art.

Description

Technical Field

[0001] This application relates to the field of magnetic field timing control technology, and in particular to a magnetic field timing control method and system for ULF-MRI and OPM-MEG. Background Technology

[0002] Ultra-low field magnetic resonance imaging (ULF-MRI) and optically pumped magnetometer magnetoencephalography (OPM-MEG) are important development directions in the field of brain imaging. ULF-MRI can acquire nuclear magnetic resonance signals in measurement magnetic fields on the order of microtesla to nanotesla, and has the potential to share the magnetic environment with high-sensitivity magnetic sensors; OPM-MEG utilizes an optically pumped magnetometer to perform highly sensitive detection of the weak magnetic fields generated by brain neural electrical activity under near-zero magnetic field conditions. Integrating these two technologies into a single system to achieve simultaneous or quasi-simultaneous acquisition of structural and functional imaging is of great value for improving the spatiotemporal resolution of brain science research and achieving precise fusion of structure and function, and has become a research focus in this field.

[0003] In integrating ULF-MRI and OPM-MEG, existing technologies primarily employ post-processing fusion to achieve joint analysis of the two modalities. These existing technologies acquire MRI structural data and MEG functional data separately using methods such as laser scanning, and then perform spatial registration and joint analysis at the data layer. By operating ULF-MRI and OPM-MEG as independent, separate devices, there is no physical interaction or control between them during acquisition; spatial alignment is only achieved through post-processing after data acquisition. Therefore, these technologies fail to address the physical electromagnetic compatibility issue when the two devices operate in the same space: ULF-MRI requires the application of a pre-polarization magnetic field, a measurement magnetic field, and rapidly switching gradient magnetic fields. The presence of these magnetic fields significantly interferes with the OPM-MEG sensor array, preventing the OPM-MEG from operating stably in its required near-zero magnetic field environment, thus affecting the quality of functional signal acquisition.

[0004] There is currently no effective solution to the technical problem that ULF-MRI and OPM-MEG cannot be compatible and operate in a unified magnetic environment. Summary of the Invention

[0005] This application provides a method and system for controlling the magnetic field timing of ULF-MRI and OPM-MEG to solve the problem in related technologies that ULF-MRI and OPM-MEG cannot be operated in a unified magnetic environment.

[0006] In the first aspect, this application provides a magnetic field timing control method for ULF-MRI and OPM-MEG, applicable to a brain imaging device, which includes a pre-polarized magnetic field coil, a measuring magnetic field coil, a gradient magnetic field coil, an OPM-MEG sensor array, and a target imaging region.

[0007] The method includes:

[0008] The brain imaging device is initialized with a magnetic field in a magnetically shielded environment, so that the OPM-MEG sensor array operates in a near-zero magnetic field state.

[0009] During the first time interval, the pre-polarized magnetic field coil is controlled to apply a pre-polarized magnetic field to the target imaging region, so that the target imaging region enters a polarization enhancement state.

[0010] During the second time interval, the application of the pre-polarized magnetic field is terminated, causing the target imaging region to enter a magnetic field decay state.

[0011] During the third time interval, the measuring magnetic field coil is controlled to apply a measuring magnetic field to the target imaging region, and the gradient magnetic field coil is controlled to apply a gradient magnetic field to the target imaging region, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals.

[0012] After the ULF-MRI structural imaging signal acquisition is completed, the switching of the gradient magnetic field coil is stopped in the fourth time interval, the measurement magnetic field is maintained, and the target imaging area is restored to the near-zero magnetic field state in order to acquire OPM-MEG brain magnetic signals.

[0013] In some embodiments, the OPM-MEG sensor array is provided with a built-in compensation coil;

[0014] The step of performing magnetic field initialization processing on the brain imaging device in a magnetically shielded environment, so that the OPM-MEG sensor array operates in a near-zero magnetic field state, includes:

[0015] Low-frequency alternating currents with decreasing amplitudes and alternating directions are sequentially applied to the prepolarized magnetic field coil, the measuring magnetic field coil, and the gradient magnetic field coil;

[0016] With all active magnetic field sources turned off, background magnetic field data of the target imaging area is acquired through the OPM-MEG sensor array.

[0017] Based on the background magnetic field data, the current of the built-in compensation coil is adjusted through closed-loop feedback to compensate for the residual magnetic field in the target imaging area, so that the net magnetic field strength at each position in the target imaging area is lower than the preset near-zero magnetic field determination threshold.

[0018] In further embodiments, the step of controlling the pre-polarized magnetic field coil to apply a pre-polarized magnetic field to the target imaging region during the first time interval, so that the target imaging region enters a polarization enhancement state, includes:

[0019] When the net magnetic field strength at each location within the target imaging area is lower than the near-zero magnetic field determination threshold, power is supplied to the pre-polarized magnetic field coil during the first time interval to generate a pre-polarized magnetic field in the target imaging area.

[0020] The intensity of the prepolarized magnetic field is within a first preset intensity range.

[0021] In further embodiments, the step of terminating the application of the pre-polarized magnetic field during the second time interval, causing the target imaging region to enter a magnetic field attenuation state, includes:

[0022] During the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease based on a preset decay curve, and a reverse pulse current is injected into the pre-polarized magnetic field coil when the current decreases, so that the intensity of the pre-polarized magnetic field decreases from the first preset intensity interval to below the second preset intensity.

[0023] The total duration of the second time interval is less than the first time threshold.

[0024] In further embodiments, the step of controlling the current of the pre-polarized magnetic field coil to decrease based on a preset decay curve during the second time interval, and injecting a reverse pulse current into the pre-polarized magnetic field coil when the current decreases, includes:

[0025] During the first period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease by the first decrease rate in the preset decay curve, while a reverse pulse current is injected into the pre-polarized magnetic field coil.

[0026] During the second time interval of the second time interval, the current of the pre-polarized magnetic field coil continues to decrease according to the second decrease rate in the preset decay curve; the second decrease rate is less than the first decrease rate.

[0027] During the third period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to drop to zero by the third rate of decrease in the preset decay curve, wherein the third rate of decrease is less than the second rate of decrease.

[0028] In some embodiments, during the third time interval, controlling the measuring magnetic field coil to apply a measuring magnetic field to the target imaging region and controlling the gradient magnetic field coil to apply a gradient magnetic field to the target imaging region, so that the target imaging region enters the imaging magnetic field state, to acquire ULF-MRI structural imaging signals, includes:

[0029] The measuring magnetic field coil is controlled to apply the measuring magnetic field with a third preset strength to the target imaging area, and the magnetic field strength of the measuring magnetic field is maintained within the third time interval;

[0030] Based on a preset imaging sequence, the following operations are performed repeatedly within the third time interval:

[0031] An excitation pulse is emitted toward the target imaging region to control the gradient magnetic field coil to apply a gradient magnetic field to the target imaging region, and the magnetic resonance signal generated in the target imaging region is received accordingly.

[0032] During a single reception of the magnetic resonance signal, the gradient magnetic field maintains a constant frequency-coded gradient.

[0033] Prior to a single emission of the excitation pulse, the phase-encoded gradient of the gradient magnetic field undergoes a step change;

[0034] Each received magnetic resonance signal is recorded as data for a corresponding phase encoding line;

[0035] In each iteration, the magnitude of the applied phase-encoded gradient is different.

[0036] In some further embodiments, the acquisition of ULF-MRI structural imaging signals includes:

[0037] Within the third time interval, the magnetic resonance signals corresponding to multiple cycles are used as the raw data of the ULF-MRI structural imaging signal; the raw data corresponds to multiple phase coding lines in K-space, which are used to reconstruct the structural image of the target imaging region;

[0038] For each acquisition time corresponding to the magnetic resonance signal, a first time base label generated based on a clock source is matched; the first time base label is used to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

[0039] In some further embodiments, after the ULF-MRI structural imaging signal acquisition is completed, during the fourth time interval, the switching of the gradient magnetic field coil is stopped, the measurement magnetic field is maintained, and the target imaging area is restored to the near-zero magnetic field state, including:

[0040] The current of the gradient magnetic field coil is controlled to return to zero within a preset time by the dynamic braking circuit, and the switching current applied to the gradient magnetic field coil is stopped, so that the gradient magnetic field coil is in a zero current state or a constant current state.

[0041] The power supply to the measuring magnetic field coil is switched to linear operating mode to maintain the strength of the measuring magnetic field stable within a preset fluctuation range corresponding to the third preset strength; the preset fluctuation range is a sub-μT threshold.

[0042] The net magnetic field strength of the target imaging area is monitored in real time, and the net magnetic field strength is kept below a fourth preset threshold; the fourth preset threshold is an nT level threshold.

[0043] In some further embodiments, the acquisition of OPM-MEG magnetoencephalogram (MEG) signals includes:

[0044] During the fourth time interval, when the net magnetic field strength of the target imaging area is lower than the fourth preset threshold, the magnetic signal generated by the subject's brain nerve activity in the target imaging area is continuously collected by the OPM-MEG sensor array at a preset sampling frequency, and used as the OPM-MEG brain magnetic signal.

[0045] For each acquisition time corresponding to the magnetic signal, a second time base tag generated based on the clock source is matched.

[0046] In some embodiments, the method further includes:

[0047] Based on the preset timing configuration of the first time interval, the second time interval, the third time interval, and the fourth time interval, the target imaging area is made to enter the magnetic field state suitable for ULF-MRI acquisition and the magnetic field state suitable for OPM-MEG acquisition in a unified magnetic environment.

[0048] The execution loop is repeated multiple times based on a preset imaging protocol, with each preset timing sequence constituting an execution loop.

[0049] Within a single execution loop, the acquired ULF-MRI structural imaging signal corresponds to a portion of the phase encoding line in the K-space, and the ULF-MRI structural imaging signals acquired in multiple execution loops are combined for three-dimensional structural reconstruction;

[0050] For all operations within a single execution loop, corresponding absolute timestamps are generated based on the same clock source to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

[0051] In some of these embodiments, the magnetic field strength of the measured magnetic field is from 1 μT to 100 μT;

[0052] The magnetic field strength of the prepolarized magnetic field is 10 mT to 100 mT.

[0053] Secondly, this application provides a magnetic field timing control system for ULF-MRI and OPM-MEG, which is suitable for brain imaging devices. The brain imaging device includes a pre-polarized magnetic field coil, a measuring magnetic field coil, a gradient magnetic field coil, an OPM-MEG sensor array, and a target imaging region.

[0054] The system includes a memory and a processor;

[0055] The processor is connected to the prepolarized magnetic field coil, the measurement magnetic field coil, the gradient magnetic field coil, and the OPM-MEG sensor array, respectively, to execute the steps of the magnetic field timing control method of ULF-MRI and OPM-MEG as described in any one of the first aspects.

[0056] Compared with the prior art, the embodiments of this application have the following beneficial effects:

[0057] This embodiment divides the acquisition process of ULF-MRI and OPM-MEG into sequentially connected time intervals. First, a pre-polarization magnetic field is applied in the first time interval to enhance nuclear spin signals. Then, in the second time interval, the pre-polarization magnetic field is rapidly terminated, allowing the system to transition to an ultra-low field measurement environment. Next, in the third time interval, a stable measurement magnetic field is applied, and gradient magnetic field switching is controlled to complete the acquisition of ULF-MRI structural imaging signals. Finally, in the fourth time interval, gradient magnetic field switching is stopped, and the measurement magnetic field is maintained, providing a stable near-zero magnetic field environment for OPM-MEG to acquire brain magnetoencephalography (MEG) signals. This timing control method achieves compatible operation of structural and functional imaging within the same magnetically shielded environment, effectively avoiding interference from the pre-polarization magnetic field and gradient magnetic field on the OPM-MEG sensor array and ensuring the purity of the MEG signal. Simultaneously, the acquisition of ULF-MRI and OPM-MEG data within a unified time frame provides a precise time alignment basis for subsequent multimodal image fusion, solving the technical problem in existing technologies where ULF-MRI and OPM-MEG cannot work collaboratively in the same physical environment.

[0058] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0059] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0060] Figure 1 This is a flowchart of a magnetic field timing control method for ULF-MRI and OPM-MEG provided in an embodiment of this application;

[0061] Figure 2 This is a flowchart of a magnetic field initialization process provided in an embodiment of this application;

[0062] Figure 3 This is a flowchart of controlling the target imaging region to enter a magnetic field attenuation state within a second time interval, provided by an embodiment of this application;

[0063] Figure 4 This is a flowchart of the current decrease of the pre-polarized magnetic field coil based on a preset attenuation curve, provided in one embodiment of this application;

[0064] Figure 5 This is a flowchart of an embodiment of the present application providing a process for bringing the target imaging region into an imaging magnetic field state;

[0065] Figure 6 This is a flowchart of an embodiment of the present application for restoring the target imaging region to a near-zero magnetic field state;

[0066] Figure 7 This is a hardware structure block diagram of the magnetic field timing control system for ULF-MRI and OPM-MEG provided in one embodiment of this application;

[0067] Figure 8 This is a schematic diagram of the magnetic field timing control system of the brain imaging device and ULF-MRI and OPM-MEG provided in an embodiment of this application.

[0068] In the diagram: 102, Processor; 104, Memory; 106, Transmission device; 108, Input / output device; 201, Magnetic shielding chamber; 202, Pre-polarized magnetic field coil; 203, Measurement magnetic field coil; 204, Gradient magnetic field coil; 205, Radio frequency transmission and reception coil; 206, OPM-MEG sensor array; 207, Subject support platform; 208, Unified control unit; 209, Data acquisition and processing system; 210, Environmental monitoring sensor. Detailed Implementation

[0069] To better understand the purpose, technical solution, and advantages of this application, the application is described and explained below in conjunction with the accompanying drawings and embodiments.

[0070] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order.

[0071] This embodiment provides a magnetic field timing control method for ULF-MRI and OPM-MEG, applicable to brain imaging devices. The brain imaging device includes a pre-polarized magnetic field coil, a measurement magnetic field coil, a gradient magnetic field coil, an OPM-MEG sensor array, and a target imaging region. The aforementioned brain imaging device can achieve coordinated acquisition of brain structural imaging and brain functional signals within the same magnetically shielded environment. Specifically, it can be applied to human or animal brain imaging research scenarios in fields such as brain science research, clinical neurological disease diagnosis, and cognitive neuroscience.

[0072] Figure 1 This is a flowchart of the magnetic field timing control method for ULF-MRI and OPM-MEG provided in this embodiment. Please refer to it. Figure 1 The process includes the following steps:

[0073] Step S110: Perform magnetic field initialization processing on the brain imaging device in a magnetically shielded environment to make the OPM-MEG sensor array work in a near-zero magnetic field state.

[0074] In this step, the magnetic shielding environment refers to an environment that can effectively attenuate the Earth's magnetic field and external magnetic field interference, which can be achieved through a magnetic shielding structure in practical scenarios. The near-zero magnetic field state refers to the magnetic field conditions under which the OPM-MEG sensor array can enter the high-sensitivity linear operating region, such as a magnetic field level below the nT level, ensuring that the OPM-MEG sensor array has sufficient detection sensitivity for the weak magnetic signals generated by brain neural activity. This step establishes a highly sensitive operating starting point for the OPM-MEG sensor array by performing magnetic field preprocessing on the brain imaging device.

[0075] Step S120: During the first time interval, control the pre-polarized magnetic field coil to apply a pre-polarized magnetic field to the target imaging region, so that the target imaging region enters a polarization enhancement state.

[0076] In this step, the polarization enhancement state refers to the physical state in which the nuclear spins within the target imaging region experience a significant increase in macroscopic magnetization under the influence of an external enhanced magnetic field. Compared to the extremely low nuclear spin polarization rate in the ultra-low field measurement magnetic field under thermal equilibrium conditions, nuclear spins in the polarization enhancement state can generate sufficiently strong magnetic resonance signals. This step, by bringing the target imaging region into the polarization enhancement state within the first time interval, provides a sufficient signal-to-noise ratio basis for subsequent ULF-MRI signal acquisition, thus addressing the problem of insufficient signal intensity caused by the weak measurement magnetic field in ultra-low field magnetic resonance.

[0077] In step S130, during the second time interval, the application of the pre-polarized magnetic field is terminated, causing the target imaging area to enter a magnetic field attenuation state.

[0078] In this step, the magnetic field decay state refers to the transition state where the pre-polarized magnetic field rapidly decreases from its operating intensity. This step shortens the waiting time and ensures a smooth transition of the magnetic field to the measurement level required for subsequent ULF-MRI structural imaging signal acquisition by actively controlling the rapid decrease of the pre-polarized magnetic field coil current and limiting its rapid decay within the second time interval.

[0079] In step S140, during the third time interval, the measurement magnetic field coil is controlled to apply a measurement magnetic field to the target imaging region, and the gradient magnetic field coil is controlled to apply a gradient magnetic field to the target imaging region, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals.

[0080] In this step, the measured magnetic field refers to the stable bias magnetic field used to establish nuclear magnetic resonance conditions during ultra-low field magnetic resonance imaging (ULF-MRI), and its intensity is typically controlled on the order of μT. The gradient magnetic field refers to the magnetic field used for spatial encoding of magnetic resonance signals, and typically includes components in multiple spatial directions. The corresponding imaging magnetic field state refers to the composite magnetic field distribution formed by the superposition of the measured magnetic field and the gradient magnetic field in the target imaging region, which satisfies the basic physical conditions for magnetic resonance spatial encoding. This step establishes a magnetic field distribution suitable for spatial encoding in the target imaging region by maintaining a stable output of the measured magnetic field within the third time interval and controlling the application and variation of the gradient magnetic field according to a preset imaging sequence. Simultaneously, the radio frequency system transmits excitation pulses to the target imaging region and receives magnetic resonance signals generated by nuclear spins, thereby acquiring raw data for reconstructing structural images and realizing the acquisition of ULF-MRI structural imaging signals.

[0081] In step S150, after the ULF-MRI structural imaging signal acquisition is completed, the switching of the gradient magnetic field coil is stopped in the fourth time interval, the measurement magnetic field is maintained, and the target imaging area is restored to a near-zero magnetic field state in order to acquire OPM-MEG brain magnetic signals.

[0082] In this step, the switching of the gradient magnetic field coil refers to the process of the current direction or amplitude changing during the operation of the gradient magnetic field coil, which causes dynamic changes in the magnetic field within the target imaging area. The mention of restoring to a near-zero magnetic field state refers to the net magnetic field environment of the target imaging area returning to the magnetic field conditions suitable for the high-sensitivity operation of the OPM-MEG sensor array, consistent with step S110. This step, by stopping the switching control of the gradient magnetic field coil after the ULF-MRI structural imaging signal acquisition is completed, stops it from generating dynamically changing magnetic fields while maintaining the stability of the measurement magnetic field, allowing the net magnetic field environment of the target imaging area to return to a near-zero magnetic field state. This creates stable operating conditions for the OPM-MEG sensor array, enabling it to continuously acquire weak magnetic signals generated by brain neural activity within the fourth time interval, thus realizing the acquisition of OPM-MEG brain magnetic signals.

[0083] Through the above steps, this embodiment achieves compatible operation of structural imaging and functional imaging within the same magnetically shielded environment. This effectively avoids interference from pre-polarized magnetic fields and gradient magnetic fields on the OPM-MEG sensor array, ensuring the purity of the OPM-MEG magnetoencephalogram (MEG) signal. Simultaneously, acquiring ULF-MRI structural imaging signals and OPM-MEG MEG signals within a unified timeframe provides a precise temporal alignment basis for subsequent multimodal image fusion. Based on the above technical means and corresponding effects, this embodiment solves the problem in related technologies where compatible and collaborative operation of ULF-MRI and OPM-MEG cannot be achieved under a unified magnetic environment.

[0084] In some embodiments, the OPM-MEG sensor array is equipped with a built-in compensation coil for finely adjusting the local magnetic field of the target imaging area to counteract the influence of residual environmental magnetic fields on sensor sensitivity.

[0085] Figure 2 This is a flowchart of the magnetic field initialization process provided in this embodiment. Please refer to it. Figure 2 In this embodiment, step S110, which is to perform magnetic field initialization processing on the brain imaging device in a magnetically shielded environment to make the OPM-MEG sensor array work in a near-zero magnetic field state, specifically includes the following steps:

[0086] Step S111: Apply low-frequency alternating currents with decreasing amplitudes and alternating directions sequentially to the pre-polarized magnetic field coil, the measuring magnetic field coil, and the gradient magnetic field coil.

[0087] The low-frequency alternating current mentioned in this step has a clear definition in the field. It is an alternating current with a frequency lower than the power frequency that can effectively penetrate the coil inductance and generate an alternating magnetization field in ferromagnetic materials. Its amplitude gradually decreases over time and its direction periodically reverses.

[0088] This step involves applying low-frequency alternating currents with decreasing amplitude and alternating directions to all magnetic field coils that may generate residual magnetism. This causes the coils and the surrounding ferromagnetic materials to gradually demagnetize during the alternating magnetization process, thereby eliminating the residual magnetism accumulated due to previous energization or environmental interference. This establishes the initial conditions for low remanent magnetism for subsequent zero magnetic field calibration.

[0089] Step S112: Turn off all active magnetic field sources and acquire background magnetic field data of the target imaging area through the OPM-MEG sensor array.

[0090] The active magnetic field source mentioned in this step refers to a coil system powered by an external power source that can generate a controllable magnetic field in the target imaging area, including but not limited to pre-polarized magnetic field coils, measurement magnetic field coils, gradient magnetic field coils, etc.; the background magnetic field data mentioned refers to the residual magnetic field distribution information in the target imaging area composed of geomagnetic leakage, residual magnetism and other environmental factors when no active magnetic field is applied.

[0091] This step involves directly measuring the magnetic field of the target imaging area using a high-sensitivity OPM-MEG sensor array while all active magnetic field sources are turned off. This acquires spatial data that reflects the true residual magnetic field distribution, providing accurate input for subsequent closed-loop compensation and avoiding compensation deviations caused by unknown environmental magnetic fields.

[0092] Step S113: Based on the background magnetic field data, the current of the built-in compensation coil is adjusted through closed-loop feedback to compensate for the residual magnetic field in the target imaging area, so that the net magnetic field strength at each position in the target imaging area is lower than the preset near-zero magnetic field judgment threshold.

[0093] The closed-loop feedback method mentioned in this step refers to an automatic control method that dynamically adjusts the output parameters based on real-time measurement results. Specifically, it involves continuously adjusting the compensation current until the deviation is eliminated, based on the deviation between the current magnetic field measurement value and the target value. The residual magnetic field mentioned refers to the non-eliminable magnetic field that still exists in the target imaging area after the demagnetization process in step S111. The near-zero magnetic field judgment threshold mentioned refers to a pre-set criterion for judging whether the OPM-MEG sensor array can enter a high-sensitivity working state. In specific scenarios, a threshold on the order of nT can be selected, such as 5nT or 10nT. The specific value is determined according to the sensor performance and measurement requirements.

[0094] This step uses the background magnetic field data obtained in step S112 as input and adopts a closed-loop feedback control strategy to dynamically adjust the driving current of the built-in compensation coil. This generates a compensation magnetic field in the target imaging area that is equal in magnitude and opposite in direction to the residual magnetic field, thereby achieving active cancellation of the residual magnetic field. This suppresses the net magnetic field intensity at each location in the area to below the preset near-zero magnetic field judgment threshold, thus establishing a stable, uniform, and highly sensitive working environment for the OPM-MEG sensor array.

[0095] Through the above sub-steps, this embodiment performs initialization processing on the magnetic field of the target imaging area within a magnetically shielded environment, combining active demagnetization and closed-loop compensation. Compared to implementation schemes that rely solely on passive shielding, this embodiment can more thoroughly eliminate the influence of the system's own residual magnetism and the residual magnetic field of the environment on the OPM-MEG sensor array, ensuring that the sensor array operates within its optimal sensitivity range in all subsequent acquisition stages, laying the foundation for acquiring high-quality magnetoencephalography (MEG) signals.

[0096] In some further embodiments, step S120, which is the step of controlling the pre-polarized magnetic field coil to apply a pre-polarized magnetic field to the target imaging region within the first time interval, so that the target imaging region enters a polarization enhancement state, specifically includes the following steps:

[0097] Step S121: When the net magnetic field strength at each location within the target imaging area is lower than the near-zero magnetic field determination threshold, power is supplied to the pre-polarized magnetic field coil within the first time interval to generate a pre-polarized magnetic field in the target imaging area; the strength of the pre-polarized magnetic field is the first preset strength interval.

[0098] In this step, the net magnetic field strength refers to the total magnetic field size that actually exists in the target imaging area after the magnetic field initialization process in step S110. This value reflects the combined effect of demagnetization and zero magnetic field calibration and is used to determine whether the OPM-MEG sensor array has the working conditions. The first preset intensity range refers to the pre-set range of pre-polarized magnetic field strength used to achieve enhanced nuclear spin polarization. Within this intensity range, the macroscopic magnetization intensity of nuclear spin can be increased to the level that supports subsequent ULF-MRI signal acquisition, which usually corresponds to a magnetic field strength on the order of mT.

[0099] This step, after confirming that the net magnetic field environment of the target imaging region meets the near-zero magnetic field determination threshold, supplies power to the pre-polarized magnetic field coil to generate a pre-polarized magnetic field within a first preset intensity range. This ensures that the application of the pre-polarized magnetic field will not interfere with the high-sensitivity working state already established by the OPM-MEG sensor array. At the same time, by controlling the pre-polarized magnetic field within an intensity range that can effectively enhance the nuclear spin polarization rate, the nuclear spins in the target imaging region enter a polarization enhancement state, providing a sufficient signal intensity basis for the subsequent acquisition of ULF-MRI structural imaging signals, thereby further solving the problem of insufficient signal-to-noise ratio caused by weak measurement magnetic fields in ultra-low field magnetic resonance.

[0100] In some further embodiments, step S120, which is the step of controlling the pre-polarized magnetic field coil to apply a pre-polarized magnetic field to the target imaging region within the first time interval, so that the target imaging region enters a polarization enhancement state, specifically includes the following parameter design:

[0101] In step S122, the intensity of the pre-polarization magnetic field is 10 mT to 100 mT, and the duration of the first time interval is 50 ms to 500 ms. It should be understood that selecting a pre-polarization magnetic field intensity range of 10 mT to 100 mT can increase the nuclear spin polarization from its thermal equilibrium state by approximately three orders of magnitude, ensuring a sufficient signal-to-noise ratio magnetic resonance signal can still be obtained under ultra-low field measurement magnetic fields. The first time interval is the pre-polarization duration set based on the longitudinal relaxation characteristics of the nuclear spin, selected as 50 ms to 500 ms. Within this time range, the nuclear spin magnetization intensity can reach or approach saturation levels. Within this time window, the nuclear spin has sufficient time to establish polarization without excessive waiting leading to an extended cycle period, thus achieving an optimized balance between signal-to-noise ratio and acquisition speed.

[0102] In some further embodiments, Figure 3 This is a flowchart provided in this embodiment for controlling the target imaging region to enter the magnetic field attenuation state within the second time interval. Please refer to it. Figure 3Step S130, which is the step of terminating the application of the pre-polarization magnetic field during the second time interval, causing the target imaging region to enter a magnetic field attenuation state, specifically includes the following steps:

[0103] Step S131: During the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease based on the preset decay curve, and a reverse pulse current is injected into the pre-polarized magnetic field coil when the current decreases, so that the intensity of the pre-polarized magnetic field decreases from the first preset intensity range to below the second preset intensity; the total duration of the second time interval is less than the first time threshold.

[0104] In this step, the preset attenuation curve refers to a set of control parameters pre-set to guide the relationship between the pre-polarized magnetic field coil current and time. This curve defines the specific path of the current decreasing from its initial value to its target value, and may include linear decrease, exponential decrease, or a combination thereof, to ensure the smoothness and controllability of the magnetic field attenuation process. The reverse pulse current refers to an instantaneous current pulse injected into the coil during the decrease of the main current of the pre-polarized magnetic field coil, which is opposite to the direction of the main current. Its function is to counteract the freewheeling effect caused by the coil inductance, accelerate the current attenuation, and suppress voltage spikes or electromagnetic interference that may be caused by rapid changes in the magnetic field. The first time threshold refers to the maximum allowable attenuation time preset to ensure the overall timing efficiency of the system. Completing the magnetic field attenuation within this time range can avoid the overall acquisition cycle being prolonged due to excessive transition time. The second preset intensity refers to the target magnetic field level that should be reached after the pre-polarized magnetic field attenuates, which usually corresponds to the measurement magnetic field range or its vicinity required for subsequent ULF-MRI structural imaging signal acquisition.

[0105] This step achieves active and rapid shutdown of the prepolarized magnetic field by controlling the current decrease of the prepolarized magnetic field coil according to the preset decay curve within the second time interval, combined with the injection of reverse pulse current. This allows the magnetic field strength to decay smoothly and rapidly from the first preset strength range to below the second preset strength. At the same time, by controlling the total duration of the second time interval within the first time threshold, the ineffective waiting time of the system during the magnetic field transition phase is effectively shortened, providing more effective working time for the subsequent acquisition of ULF-MRI structural imaging signals. This improves the overall time efficiency of the system while ensuring the smoothness of the magnetic field transition.

[0106] In some further embodiments, step S130, which is the step of terminating the application of the pre-polarization magnetic field during the second time interval to allow the target imaging region to enter a magnetic field attenuation state, specifically includes the following parameter design:

[0107] In step S132, the first preset intensity refers to a specific value within the first preset intensity range, such as 50 mT. Correspondingly, the total duration of the second time interval is less than 100 ms, and can be 80 ms. The second preset intensity refers to the measurement magnetic field level required for subsequent ULF-MRI structural imaging signal acquisition, such as 50 μT; the mentioned reverse pulse current refers to the instantaneous current pulse injected in the early stage of decay that is opposite to the direction of the main current, and its amplitude is set to 10% of the steady-state current.

[0108] In some further embodiments, in step S130, the current of the pre-polarized magnetic field coil is controlled to decrease based on a preset decay curve, using an exponential decay method. Specifically, during the second time interval, the supply current of the pre-polarized magnetic field coil is controlled according to an exponential function. The regular decay, among which, For the initial current, It is a time constant. This corresponds to the moment within the second time interval. By selecting an appropriate time constant, the prepolarized magnetic field strength is made to decay rapidly and smoothly to the target level within the second time interval.

[0109] In some further embodiments, step S130, during the process of terminating the application of the prepolarized magnetic field, also includes magnetic field monitoring and trigger control.

[0110] Specifically, during the second time interval, the magnetic field attenuation curve of the target imaging area is monitored in real time by environmental monitoring sensors. When the magnetic field strength is detected to have attenuated to a preset proportion of the target measurement magnetic field, such as attenuating to 110% of the target measurement magnetic field, the system is triggered to enter the third time interval ahead of schedule or on time to begin acquiring ULF-MRI structural imaging signals. This step, through real-time magnetic field monitoring and trigger control, ensures that subsequent acquisition starts as soon as the magnetic field attenuates to near the target level, thereby optimizing the efficiency of timing control while ensuring the smoothness of the magnetic field transition.

[0111] In some further embodiments, Figure 4 This is a flowchart of the current decrease of the pre-polarized magnetic field coil controlled by a preset attenuation curve, provided in this embodiment. Please refer to it. Figure 4 Step S131, which is the step of controlling the current of the pre-polarized magnetic field coil to decrease based on the preset decay curve during the second time interval, and injecting a reverse pulse current into the pre-polarized magnetic field coil when the current decreases, specifically includes the following steps:

[0112] Step S131.1: During the first time period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease by the first decrease rate in the preset decay curve, while a reverse pulse current is injected into the pre-polarized magnetic field coil.

[0113] In this step, by using a higher first decline rate in the first time period to control the rapid decline of the current in the prepolarized magnetic field coil, and combined with the injection of reverse pulse current, the active suppression of the coil inductance freewheeling effect is achieved in the early stage of decay, thereby accelerating the initial decay process of the prepolarized magnetic field.

[0114] Step S131.2: During the second time period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to continue to decrease by the second decrease rate in the preset decay curve; the second decrease rate is less than the first decrease rate.

[0115] In this step, the current continues to decrease by using a second decrease rate that is less than the first decrease rate in the second time period. This reduces the rate of change of the magnetic field while maintaining the decay process, thereby reducing the induced voltage surge that may be generated in the coil and surrounding circuits due to the rapid change of current.

[0116] In step S131.3, during the third time period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to drop to zero by the third rate of decrease in the preset decay curve, and the third rate of decrease is less than the second rate of decrease.

[0117] In this step, the current is gradually reduced to zero by using a third rate of decrease that is less than the second rate of decrease in the third time period, so that the prepolarized magnetic field is completely removed in the smoothest way at the end of the decay period, avoiding residual magnetic field fluctuations caused by the sudden change of the current to zero.

[0118] In some further embodiments, step S131, which is the step of controlling the current of the pre-polarized magnetic field coil to decrease based on a preset decay curve during the second time interval, and injecting a reverse pulse current into the pre-polarized magnetic field coil when the current decreases, specifically includes the following design:

[0119] In the first period, from 0ms to 20ms, the current of the prepolarized magnetic field coil is controlled to decrease linearly from the rated value to 50% at the first decreasing rate. At the same time, a reverse pulse current with an amplitude of 10% of the steady-state current is injected into the coil to counteract the freewheeling effect of the coil inductance and accelerate the current decay.

[0120] In the second period, from 20ms to 60ms, the control current continues to decrease linearly to 10% at a second decreasing rate. The second decreasing rate is less than the first decreasing rate to reduce the induced voltage surge caused by rapid changes in the magnetic field.

[0121] In the third period, from 60ms to 80ms, the control current decreases linearly to zero at a third rate of decrease. The third rate of decrease is less than the second rate of decrease, ensuring that the magnetic field smoothly transitions to a zero-current state.

[0122] This step, by strictly controlling the second time interval within 100ms and combining a piecewise linear decay and reverse pulse injection active shutdown strategy, allows the prepolarized magnetic field strength to decay rapidly and smoothly from 50mT to below 50μT, thereby minimizing the system's ineffective waiting time and ensuring a smooth transition of the magnetic field to the ultra-low field measurement level. This provides a stable magnetic field environment for the subsequent acquisition of ULF-MRI structural imaging signals and avoids interference with the operation of the OPM-MEG sensor array.

[0123] In some of these embodiments, Figure 5 This is a flowchart of the process of bringing the target imaging region into the imaging magnetic field state provided in this embodiment. Please refer to it. Figure 5 Step S140, which involves controlling the measurement magnetic field coil to apply a measurement magnetic field to the target imaging region and controlling the gradient magnetic field coil to apply a gradient magnetic field to the target imaging region within the third time interval, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals, specifically includes the following steps:

[0124] Step S141: Control the measuring magnetic field coil to apply a measuring magnetic field with a third preset strength to the target imaging area, and maintain the magnetic field strength of the measuring magnetic field within the third time interval.

[0125] In this step, by controlling the output of a stable and sufficiently strong measurement magnetic field from the measurement magnetic field coil and maintaining the magnetic field strength constant throughout the entire third time interval, a unified Larmor frequency reference is established for the nuclear spins in the target imaging region, ensuring that the frequencies of all subsequent magnetic resonance signals are consistent.

[0126] Step S142, based on the preset imaging sequence, repeatedly perform the following operations in the third time interval:

[0127] Step S142.1: An excitation pulse is emitted toward the target imaging region, and the gradient magnetic field coil is controlled to apply a gradient magnetic field to the target imaging region, thereby receiving the magnetic resonance signal generated in the target imaging region.

[0128] In this step, by emitting an excitation pulse toward the target imaging region in each cycle, the nuclear spins in the enhanced polarization state undergo resonant transitions and generate free induction decay signals or echo signals; at the same time, by applying a gradient magnetic field to spatially encode the signal, the receiving system acquires the magnetic resonance signal containing spatial location information, realizing the K-space data line corresponding to a single acquisition.

[0129] In step S142.2, during a single reception of a magnetic resonance signal, the gradient magnetic field maintains a constant frequency-coded gradient.

[0130] In this step, by keeping the frequency encoding gradient in the gradient magnetic field constant during signal readout, the nuclear spins at different spatial locations generate frequency shifts in the frequency dimension corresponding to their positions, thereby encoding spatial information into the frequency of the magnetic resonance signal and achieving spatial dimension resolution.

[0131] In step S142.3, before the single emission of the excitation pulse, the phase-encoded gradient of the gradient magnetic field undergoes a step change.

[0132] In this step, by performing a step change on the phase encoding gradient in the gradient magnetic field before each excitation pulse is emitted, the phase encoding step amount corresponding to this acquisition is changed, so that the signals acquired in different cycles carry different spatial encoding information in the phase dimension, thereby gradually covering multiple phase encoding lines in K space.

[0133] Step S142.4: Record the magnetic resonance signal received each time the operation is performed as the data for the corresponding phase encoding line.

[0134] In this step, the magnetic resonance signals received in each loop are marked and stored according to their corresponding phase encoding step, forming the original dataset corresponding to the K-space phase encoding line, which provides complete input data for subsequent reconstruction algorithms such as Fourier transform to generate structural images.

[0135] In each iteration, the amplitude of the applied phase-encoded gradient differs. The preset imaging sequence mentioned in step S142 refers to a pre-defined set of instructions used to control the timing of the radio frequency pulse and the gradient magnetic field, such as a gradient echo sequence, a spin echo sequence, or a variant thereof. This sequence specifies parameters such as the emission time of the excitation pulse, the application timing of the gradient magnetic field, and the signal reception window. The purpose of repeatedly executing step S142 within the third time interval is to acquire magnetic resonance signals covering different phase-encoded lines in K-space through multiple repeated acquisitions, thereby accumulating sufficient raw data for subsequent reconstruction of the complete structural image.

[0136] In some embodiments, step S140, which involves controlling the measurement magnetic field coil to apply a measurement magnetic field to the target imaging region and controlling the gradient magnetic field coil to apply a gradient magnetic field to the target imaging region during the third time interval, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals, specifically includes the following parameter design:

[0137] In step S141, the third preset intensity is set to 50 μT, and the corresponding third time interval duration is set to 200 ms. By controlling the output of the measuring magnetic field coil to a measuring magnetic field with an intensity of 50 μT, and maintaining the magnetic field intensity within a fluctuation range of ±0.1 μT throughout the entire 200 ms third time interval, a unified Larmor frequency reference is established for the nuclear spins in the target imaging region.

[0138] In step S142, the preset imaging sequence is a two-dimensional gradient echo sequence, which specifies the timing coordination between the radio frequency excitation pulse and the gradient magnetic field. Step S142 is executed cyclically within a third time interval of 200ms. Through multiple repeated acquisitions, magnetic resonance signals covering different phase encoding lines in K-space are obtained. Specifically, the repetition time is set to 25ms, and 8 cycles can be completed within 200ms, acquiring data from 8 phase encoding lines.

[0139] In step S142.1, a 90-degree radio frequency excitation pulse is emitted to the target imaging region in each cycle to induce a resonant transition of the nuclear spin in the enhanced polarization state and generate a free induction decay signal; at the same time, the signal is spatially encoded by applying a gradient magnetic field and the receiving system acquires a magnetic resonance signal containing spatial location information.

[0140] In step S142.2, the gradient magnetic field maintains a constant frequency-coded gradient during a single reception of the magnetic resonance signal.

[0141] In step S142.3, before the single emission of the excitation pulse, the phase-encoded gradient of the gradient magnetic field undergoes a step change.

[0142] In step S142.4, the magnetic resonance signals received in each loop are marked and stored according to their corresponding phase encoding step size to form the original dataset corresponding to the K-space phase encoding lines. Within the third time interval of 200ms, data from 8 phase encoding lines are acquired through 8 loops, providing partial K-space data for subsequent reconstruction algorithms such as Fourier transform to generate structural images.

[0143] In some further embodiments, after the sub-step of acquiring ULF-MRI structural imaging signals in step S140, the following steps are also included:

[0144] Step S143: Within the third time interval, the magnetic resonance signals corresponding to multiple cycles are used as the raw data of the ULF-MRI structural imaging signal; the raw data corresponds to multiple phase coding lines in the K space, which are used to reconstruct the structural image of the target imaging region.

[0145] In this step, the K-space refers to the spatial frequency domain used to store raw data in magnetic resonance imaging (MRI). Each data point corresponds to the amplitude and phase of a specific spatial frequency component. By performing a Fourier transform on the K-space data, the real-space structural image of the target imaging region can be reconstructed. This step combines the MRI signals acquired in multiple iterations in step S142 into a complete raw dataset. This dataset covers a preset phase encoding step range in K-space, providing complete input data for subsequent generation of high-resolution brain structure images using reconstruction algorithms such as Fourier transform, thus achieving the transition from raw signals to reconstructable images.

[0146] Step S144: For each acquisition time corresponding to a magnetic resonance signal, a first time base label generated based on a clock source is matched; the first time base label is used to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

[0147] In this step, the clock source refers to a highly stable clock generator that provides a unified time reference for the entire system, such as a 10MHz temperature-compensated crystal oscillator. This step generates a first time base tag based on the same clock source by acquiring each magnetic resonance signal at the same time, including the excitation pulse emission time, gradient switching time, and signal reception window. These tags are then associated with and stored with the magnetic resonance signals, achieving precise positioning of ULF-MRI structural imaging signals on a unified time axis.

[0148] In some further embodiments, Figure 6 This is a flowchart illustrating how to restore the target imaging region to a near-zero magnetic field state, provided in this embodiment. Please refer to it. Figure 6 In step S150, after the ULF-MRI structural imaging signal acquisition is completed, the switching of the gradient magnetic field coil is stopped within the fourth time interval, and the measurement magnetic field is maintained to restore the target imaging area to a near-zero magnetic field state. This sub-step specifically includes the following steps:

[0149] Step S151: Based on the dynamic braking circuit, the current of the gradient magnetic field coil is controlled to return to zero within a preset time, and the switching current applied to the gradient magnetic field coil is stopped, so that the gradient magnetic field coil is in a zero current state or a constant current state.

[0150] In this step, the energy stored in the gradient magnetic field coil is rapidly dissipated through a dynamic braking circuit, causing the coil current to drop rapidly to zero within a preset time window. This completely eliminates the dynamic magnetic field changes caused by gradient magnetic field switching, creating an interference-free magnetic field environment for the OPM-MEG sensor array. The dynamic braking circuit may include an energy-dissipating resistor or an active switching device connected in parallel with the coil, which converts the energy stored in the coil inductance into heat energy for rapid release when it needs to be turned off.

[0151] Step S152: Switch the power supply of the measuring magnetic field coil to the linear working mode, i.e., the low-noise linear mode, so as to maintain the strength of the measuring magnetic field within the preset fluctuation range corresponding to the third preset strength; the preset fluctuation range is the sub-μT threshold.

[0152] In this step, under the aforementioned linear operating mode, power supply output ripple and noise are suppressed to a minimum, typically achieved through linear regulation or active filtering, to prevent power supply noise from coupling into the measured magnetic field and causing magnetic field fluctuations. The mentioned sub-μT threshold refers to a quantitative indicator of magnetic field stability; within this range, fluctuations in the measured magnetic field are controlled within the acceptable range for the OPM-MEG sensor array, and magnetic field drift will not affect the sensor's zero-bias stability. This step, by switching the power supply to linear operating mode, ensures that the measured magnetic field remains highly stable within the fourth time interval, providing a stable and predictable background field for the OPM-MEG sensor array.

[0153] Step S153: Monitor the net magnetic field strength of the target imaging area in real time, and make the net magnetic field strength lower than the fourth preset threshold; the fourth preset threshold is an nT level threshold.

[0154] In this step, the nT threshold refers to the upper limit of the magnetic field that allows the OPM-MEG sensor array to enter its high-sensitivity operating range. Below this threshold, the sensor can stably output a linear response. Real-time monitoring refers to continuously measuring the magnetic field of the target imaging area using environmental monitoring sensors or the OPM-MEG sensor array itself, and comparing it to a preset threshold. This step ensures that the magnetic field environment meets the requirements before MEG acquisition by continuously monitoring the net magnetic field strength, and maintains this state throughout the entire fourth time interval. This guarantees that the OPM-MEG sensor array always operates within its optimal sensitivity range, acquiring high-quality magnetoencephalography (MEG) signals.

[0155] In some further embodiments, step S150, after the ULF-MRI structural imaging signal acquisition is completed, involves stopping the switching of the gradient magnetic field coils within the fourth time interval, maintaining the measurement magnetic field, and restoring the target imaging area to a near-zero magnetic field state. This sub-step specifically includes the following parameter design:

[0156] Step S151: Based on the energy-consuming resistor and switching device connected in parallel with the gradient coil, control the current of the gradient magnetic field coil to return to zero within 2ms, stop applying the switching current to the gradient magnetic field coil, and make the gradient magnetic field coil in a zero current state or a constant current state.

[0157] Step S152: Switch the power supply of the measuring magnetic field coil to the linear working mode to maintain the strength of the measuring magnetic field at 50μT, which is within the corresponding preset fluctuation range, i.e., 50μT plus or minus 0.1μT.

[0158] Step S153: Monitor the net magnetic field strength of the target imaging area in real time, and make the net magnetic field strength lower than the fourth preset threshold; the fourth preset threshold is 2nT.

[0159] In this step, the 2nT threshold mentioned is based on the upper limit of the linear operating range given in the OPM-MEG sensor array datasheet. Below this threshold, the sensor can stably output a linear response. The net magnetic field strength of the target imaging area is monitored in real time at a sampling frequency of 1kHz using an environmental monitoring sensor. Once it is confirmed that the magnetic field is below 2nT, the OPM-MEG sensor array is activated to start acquisition; and monitoring continues throughout the entire fourth time interval to ensure that the magnetic field always meets the requirements.

[0160] In some further embodiments, step S150, which involves acquiring OPM-MEG magnetoencephalogram (MEG) signals, specifically includes the following steps:

[0161] In step S154, when the net magnetic field strength of the target imaging area is lower than the fourth preset threshold during the fourth time interval, the magnetic signals generated by the subject's brain nerve activity in the target imaging area are continuously collected by the OPM-MEG sensor array at a preset sampling frequency and used as OPM-MEG brain magnetic signals.

[0162] In this step, the magnetic field environment within the fourth time interval is strictly controlled below the fourth preset threshold to ensure that the OPM-MEG sensor array operates within its linear high-sensitivity region. Based on this, continuous acquisition of the target imaging area is performed at a preset sampling frequency to capture weak magnetic signals generated by brain neural electrical activity. This enables high-fidelity acquisition of brain functional signals in an interference-free magnetic field environment, ensuring the purity and temporal resolution of the OPM-MEG brain magnetic signals.

[0163] Step S155: For each magnetic signal acquisition time, match the second time base tag generated based on the clock source.

[0164] In this step, a second time base label based on the same clock source is generated for each magnetic signal sampling point, and this label is associated with and stored with the sampling data, enabling precise positioning of the OPM-MEG magnetoencephalogram (MEG) signal on a unified time axis. These second time base labels are generated based on the same clock source as the first time base labels of the OPM-MEG MEG signal in the third time interval, thus ensuring that the two types of data can be precisely aligned on the time axis.

[0165] In some further embodiments, step S150, which involves acquiring OPM-MEG magnetoencephalogram (MEG) signals, specifically includes the following parameter design:

[0166] In step S154, when the net magnetic field strength of the target imaging area is below 2nT within 1720ms, the target imaging area is continuously sampled at a sampling frequency of 2kHz using an OPM-MEG sensor array to capture weak fT-level magnetic signals generated by brain neural electrical activity, which are then used as OPM-MEG brain magnetic signals. A cognitive task (such as the Oddball auditory paradigm) is presented to the subject through an audiovisual stimulation system, achieving task-phase-locked OPM-MEG brain magnetic signal acquisition. This step achieves high-fidelity, high-temporal-resolution acquisition of brain functional signals in an interference-free magnetic field environment.

[0167] In step S155, for the magnetic signal acquired at each sampling moment, a second time base tag is matched using the same clock source generated based on a 10MHz temperature-compensated crystal oscillator. This clock source has a timing accuracy at the nanosecond level; therefore, for each sampling point, at 0.5ms intervals, an absolute time stamp with nanosecond-level accuracy can be obtained and stored in association with the sampling data. These second time base tags originate from the same clock source as the first time base tags generated when acquiring ULF-MRI structural imaging signals in the third time interval, thereby ensuring that the data acquired by ULF-MRI and the data acquired by OPM-MEG are precisely aligned at the nanosecond level on the time axis.

[0168] In some embodiments, the method further includes the following steps, which may be performed after step S110 and before step S120, or as the basis for configuring the overall process after step S150:

[0169] Based on the preset time sequence configuration of the first time interval, the second time interval, the third time interval and the fourth time interval, the target imaging area enters the magnetic field state suitable for ULF-MRI acquisition and the magnetic field state suitable for OPM-MEG acquisition in a unified magnetic environment.

[0170] This step, by pre-setting the duration and sequence of each time interval, forms a standardized timing template, ensuring that structural imaging and functional imaging can be carried out in an orderly alternation within the same magnetically shielded environment, avoiding magnetic field state conflicts, and providing a unified timing framework for subsequent cyclic execution.

[0171] The execution loop is executed repeatedly based on a preset imaging protocol, with each preset timing sequence constituting an execution loop.

[0172] This step uses the configured timing sequence as the basic unit and automatically repeats the loop according to a preset imaging protocol, such as according to the scan duration, the number of K-space lines covered, etc., thereby gradually acquiring all the signals required for complete imaging.

[0173] Within a single execution loop, the acquired ULF-MRI structural imaging signals correspond to a portion of the phase encoding lines in the K-space. The ULF-MRI structural imaging signals acquired through multiple execution loops are combined for three-dimensional structural reconstruction.

[0174] This step involves acquiring partial phase-encoded lines in the K-space during each loop and combining the data from multiple loops into a complete K-space dataset. This provides complete raw data for subsequent generation of 3D brain structure images using reconstruction algorithms such as Fourier transform, thus achieving a transition from local acquisition to overall reconstruction.

[0175] For all operations within a single execution loop, corresponding absolute timestamps are generated based on the same clock source to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

[0176] This step achieves precise alignment of the two types of data on the time axis by assigning an absolute timestamp generated based on the same highly stable clock source to each magnetic resonance signal acquired by ULF-MRI and each sampling point acquired by OPM-MEG in each execution loop, providing sub-millisecond or even nanosecond-level time synchronization accuracy for subsequent multimodal image fusion.

[0177] In some embodiments, the method further includes: the first time interval, the second time interval, the third time interval, and the fourth time interval are executed in a time-overlapping sequence.

[0178] Specifically, while ensuring the normal operation of the OPM-MEG sensor array, the third time interval and the fourth time interval are allowed to have some overlap in timing.

[0179] For example, during the intervals between ULF-MRI sequences where the gradient magnetic field is kept constant or completely off, such as the signal readout interval after the radio frequency excitation pulse is emitted, the OPM-MEG sensor array can be activated simultaneously to perform quasi-synchronous acquisition of brain magnetic signals; or when using a specific ULF-MRI sequence that causes minimal interference to the OPM-MEG sensor array, such as a sequence in which only a static measurement magnetic field is applied without gradient switching, simultaneous acquisition of structural and functional imaging can be achieved.

[0180] This step, through partially overlapping timing arrangement, further shortens the overall time interval between structural and functional acquisition while ensuring that the OPM-MEG sensor array is not affected by gradient magnetic field switching. This makes the functional activity moment more closely related to the structural imaging moment, thereby improving the temporal resolution of multimodal data.

[0181] In some embodiments, the magnetic field strength of the measurement magnetic field is 1 μT to 100 μT; the magnetic field strength of the pre-polarization magnetic field is 10 mT to 100 mT. Through the above parameter design, this embodiment ensures that the nuclear spin polarization is increased by approximately three orders of magnitude from the thermal equilibrium state, providing a sufficient signal-to-noise ratio basis for ULF-MRI. Simultaneously, setting the measurement magnetic field within the range of 1 μT to 100 μT satisfies the bias field requirements of ultra-low field magnetic resonance imaging while ensuring that the field strength is within the acceptable background field range of the OPM-MEG sensor array, avoiding interference with functional acquisition. Within the above range, the pre-polarization magnetic field strength can be specific values ​​such as 10 mT, 50 mT, and 100 mT, and the measurement magnetic field strength can be specific values ​​such as 1 μT, 50 μT, and 100 μT. The two are not strictly corresponding; the key is that the pre-polarization magnetic field is sufficient to achieve effective nuclear spin polarization, and the measurement magnetic field can maintain magnetic resonance conditions without exceeding the linear operating region of the OPM-MEG sensor array. By reasonably selecting specific values ​​within this range, this embodiment can be flexibly optimized according to the actual system configuration and imaging requirements, ensuring the image signal-to-noise ratio while also taking into account the purity of functional acquisition.

[0182] This embodiment also provides a magnetic field timing control system for ULF-MRI and OPM-MEG, which is suitable for brain imaging devices. The brain imaging device includes a pre-polarized magnetic field coil, a measuring magnetic field coil, a gradient magnetic field coil, and a target imaging region.

[0183] Figure 7 This is a hardware block diagram of the magnetic field timing control system for ULF-MRI and OPM-MEG provided in this embodiment. Figure 7 As shown, the system may include one or more ( Figure 7 (Only one is shown in the diagram) Processor 102 and memory 104, wherein processor 102 may be a processing device including but not limited to a microprocessor MCU or a programmable logic device FPGA. Processor 102 is connected to a pre-polarized magnetic field coil, a measurement magnetic field coil, and a gradient magnetic field coil, respectively, to execute the steps of the magnetic field timing control method of ULF-MRI and OPM-MEG of any of the foregoing embodiments and their preferred embodiments.

[0184] In some of these embodiments, further reference is made to Figure 7 The system may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 7 The structure shown is for illustrative purposes only and does not limit the structure of the terminal described above. For example, the terminal may also include components that are larger than... Figure 7 The more or fewer components shown, or having the same Figure 7 The different configurations shown are illustrated.

[0185] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the ULF-MRI and OPM-MEG magnetic field timing control system in this embodiment. The processor 102 executes various functional applications and data processing by running the computer programs stored in the memory 104, thus implementing the methods described above. The memory 104 may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0186] The transmission device 106 is used to receive or send data via a network. This network includes a wireless network provided by the terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 can be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0187] In some embodiments, the system is implemented collaboratively by a unified control unit and environmental monitoring sensors. The unified control unit includes an FPGA timing board with nanosecond-level synchronization accuracy. This timing board generates a unified clock source based on a 10MHz temperature-compensated crystal oscillator and is connected to the power supplies for the pre-polarized magnetic field coil, the measurement magnetic field coil, the gradient magnetic field coil, and the OPM-MEG data acquisition system. This synchronizes the switching timing of each coil and the sampling clock of the data acquisition system. The environmental monitoring sensors include a triaxial Fluxgate magnetometer and a temperature sensor, deployed at key locations within the magnetically shielded chamber. These sensors monitor changes in the background magnetic field and ambient temperature drift in the target imaging area in real time. During the magnetic field initialization phase, the environmental monitoring sensors provide feedback data for closed-loop compensation. In the fourth time interval, the environmental monitoring sensors continuously monitor the net magnetic field strength to ensure that the magnetic field conditions meet the operating requirements of the OPM-MEG sensor array. Throughout the acquisition process, data from the temperature sensor is used to compensate for sensor zero drift caused by temperature changes. Through precise timing control of the unified control unit and real-time feedback from environmental monitoring sensors, this embodiment achieves coordinated scheduling of various magnetic field sources and closed-loop monitoring of the magnetic field environment, providing hardware-level assurance for the synchronous acquisition of structural and functional signals, and significantly improving the automation level of the system and the reliability of the acquired data.

[0188] In some of these embodiments, Figure 8 This is a schematic diagram of the brain imaging device and the magnetic field timing control system of ULF-MRI and OPM-MEG provided in this embodiment. Please refer to it. Figure 8 The brain imaging device can be integrated within the magnetically shielded chamber 201, including a pre-polarized magnetic field coil 202, a measuring magnetic field coil 203, a gradient magnetic field coil 204, a radio frequency transmitting and receiving coil 205, an OPM-MEG sensor array 206, and a subject support platform 207. Furthermore, the brain imaging device can also integrate a unified control unit 208, a data acquisition and processing system 209, and an environmental monitoring sensor 210 outside the magnetically shielded chamber 201. The subject support platform 207 is made of non-magnetic material, and its height and angle are adjustable to support the subject and maintain a stable posture during data acquisition. The subject wears a flexible helmet made of lightweight, non-magnetic, and deformable material. The inner surface of the helmet integrates the OPM-MEG sensor array 206, which adaptively conforms to the shape of the subject's head. The flexible helmet contains sensor mounting bases and wiring channels. The built-in compensation coils of the OPM-MEG sensor array 206 are connected to the unified control unit 208 via flexible circuitry.

[0189] In this embodiment, the unified control unit 208 coordinates and controls each subsystem to perform the following operations according to a preset timing sequence:

[0190] During the first time interval, the unified control unit 208 controls the pre-polarized magnetic field coil 202 to apply a pre-polarized magnetic field to the target imaging area where the subject's head is located, so that the target imaging area enters the first magnetic field state.

[0191] During the second time interval, the unified control unit 208 controls the pre-polarized magnetic field coil 202 to terminate the application of the pre-polarized magnetic field, and achieves rapid and smooth shutdown through a preset attenuation curve and reverse pulse injection, so that the target imaging area transitions to the second magnetic field state.

[0192] During the third time interval, the unified control unit 208 controls the measuring magnetic field coil 203 to apply and maintain the measuring magnetic field to the target imaging area, controls the gradient magnetic field coil 204 to apply the gradient magnetic field according to the preset imaging sequence, and simultaneously triggers the radio frequency transmitting and receiving coil 205 to transmit excitation pulses and receive magnetic resonance signals, so that the target imaging area enters the third magnetic field state and acquires ULF-MRI structural imaging signals.

[0193] During the fourth time interval, the unified control unit 208 stops the switching of the gradient magnetic field coil 204 and maintains the measurement magnetic field, so that the target imaging area enters the fourth magnetic field state, and at the same time activates the OPM-MEG sensor array 206 to collect the magnetic signals generated by brain nerve activity.

[0194] Environmental monitoring sensor 210 monitors the magnetic field strength and temperature inside the magnetic shielding chamber 201 in real time and feeds the monitoring data back to unified control unit 208 for closed-loop control. Data acquisition and processing system 209 simultaneously records ULF-MRI structural imaging signals and OPM-MEG magnetoencephalography signals, and generates an absolute timestamp based on the same clock source for the acquisition time of each signal, achieving precise alignment of the two types of data on the time axis.

[0195] With the above configuration, this embodiment sequentially acquires ULF-MRI structural imaging signals and OPM-MEG magnetoencephalography (MEG) signals within the same magnetically shielded environment. Because the subject's head is fixed by a non-magnetic support platform and a flexible helmet, and the magnetic field environment alternates within the same system rather than being acquired separately by separate devices, the two types of data naturally reside in the same spatial coordinate system. This eliminates the need for complex post-processing spatial registration, enabling the fusion of structural and functional information. This embodiment provides an integrated technical solution for brain science research, clinical neurological disease diagnosis, and cognitive function atlas construction.

[0196] Furthermore, in conjunction with the magnetic field timing control methods for ULF-MRI and OPM-MEG provided in the above embodiments, this embodiment can also provide a storage medium for implementation. This storage medium stores a computer program; when executed by a processor, the computer program implements any one of the magnetic field timing control methods for ULF-MRI and OPM-MEG in the above embodiments.

[0197] It should be noted that all information and data involved in this application are authorized by the user or fully authorized by all parties and will be used legally.

[0198] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0199] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0200] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0201] The above embodiments merely illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application.

Claims

1. A method for controlling the magnetic field timing of ULF-MRI and OPM-MEG, characterized in that, Suitable for brain imaging devices, the brain imaging devices include pre-polarized magnetic field coils, measuring magnetic field coils, gradient magnetic field coils, OPM-MEG sensor arrays, and target imaging regions; The method includes: The brain imaging device is initialized with a magnetic field in a magnetically shielded environment, so that the OPM-MEG sensor array operates in a near-zero magnetic field state. During the first time interval, the pre-polarized magnetic field coil is controlled to apply a pre-polarized magnetic field to the target imaging region, so that the target imaging region enters a polarization enhancement state. During the second time interval, the application of the pre-polarized magnetic field is terminated, causing the target imaging region to enter a magnetic field decay state. During the third time interval, the measuring magnetic field coil is controlled to apply a measuring magnetic field to the target imaging region, and the gradient magnetic field coil is controlled to apply a gradient magnetic field to the target imaging region, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals. After the ULF-MRI structural imaging signal acquisition is completed, the switching of the gradient magnetic field coil is stopped in the fourth time interval, the measurement magnetic field is maintained, and the target imaging area is restored to the near-zero magnetic field state in order to acquire OPM-MEG brain magnetic signals.

2. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 1, characterized in that, The OPM-MEG sensor array is equipped with a built-in compensation coil; The step of performing magnetic field initialization processing on the brain imaging device in a magnetically shielded environment, so that the OPM-MEG sensor array operates in a near-zero magnetic field state, includes: Low-frequency alternating currents with decreasing amplitudes and alternating directions are sequentially applied to the prepolarized magnetic field coil, the measuring magnetic field coil, and the gradient magnetic field coil; With all active magnetic field sources turned off, background magnetic field data of the target imaging area is acquired through the OPM-MEG sensor array. Based on the background magnetic field data, the current of the built-in compensation coil is adjusted through closed-loop feedback to compensate for the residual magnetic field in the target imaging area, so that the net magnetic field strength at each position in the target imaging area is lower than the preset near-zero magnetic field determination threshold.

3. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 2, characterized in that, During the first time interval, controlling the pre-polarized magnetic field coil to apply a pre-polarized magnetic field to the target imaging region, causing the target imaging region to enter a polarization enhancement state, includes: When the net magnetic field strength at each location within the target imaging area is lower than the near-zero magnetic field determination threshold, power is supplied to the pre-polarized magnetic field coil during the first time interval to generate a pre-polarized magnetic field in the target imaging area. The intensity of the prepolarized magnetic field is within a first preset intensity range.

4. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 3, characterized in that, During the second time interval, terminating the application of the pre-polarized magnetic field, causing the target imaging region to enter a magnetic field attenuation state, includes: During the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease based on a preset decay curve, and a reverse pulse current is injected into the pre-polarized magnetic field coil when the current decreases, so that the intensity of the pre-polarized magnetic field decreases from the first preset intensity interval to below the second preset intensity. The total duration of the second time interval is less than the first time threshold.

5. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 4, characterized in that, The step of controlling the current decrease of the pre-polarized magnetic field coil based on a preset decay curve during the second time interval, and injecting a reverse pulse current into the pre-polarized magnetic field coil when the current decreases, includes: During the first period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to decrease by the first decrease rate in the preset decay curve, while a reverse pulse current is injected into the pre-polarized magnetic field coil. During the second time interval of the second time interval, the current of the pre-polarized magnetic field coil continues to decrease according to the second decrease rate in the preset decay curve; the second decrease rate is less than the first decrease rate. During the third period of the second time interval, the current of the pre-polarized magnetic field coil is controlled to drop to zero by the third rate of decrease in the preset decay curve, wherein the third rate of decrease is less than the second rate of decrease.

6. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 1, characterized in that, During the third time interval, the measurement magnetic field coil is controlled to apply a measurement magnetic field to the target imaging region, and the gradient magnetic field coil is controlled to apply a gradient magnetic field to the target imaging region, so that the target imaging region enters the imaging magnetic field state to acquire ULF-MRI structural imaging signals, including: The measuring magnetic field coil is controlled to apply the measuring magnetic field with a third preset strength to the target imaging area, and the magnetic field strength of the measuring magnetic field is maintained within the third time interval; Based on a preset imaging sequence, the following operations are performed repeatedly within the third time interval: An excitation pulse is emitted toward the target imaging region to control the gradient magnetic field coil to apply a gradient magnetic field to the target imaging region, and the magnetic resonance signal generated in the target imaging region is received accordingly. During a single reception of the magnetic resonance signal, the gradient magnetic field maintains a constant frequency-coded gradient. Prior to a single emission of the excitation pulse, the phase-encoded gradient of the gradient magnetic field undergoes a step change; Each received magnetic resonance signal is recorded as data for a corresponding phase encoding line; In each iteration, the magnitude of the applied phase-encoded gradient is different.

7. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 6, characterized in that, The acquisition of ULF-MRI structural imaging signals includes: Within the third time interval, the magnetic resonance signals corresponding to multiple cycles are used as the raw data of the ULF-MRI structural imaging signal; the raw data corresponds to multiple phase coding lines in K-space, which are used to reconstruct the structural image of the target imaging region; For each acquisition time corresponding to the magnetic resonance signal, a first time base label generated based on a clock source is matched; the first time base label is used to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

8. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 7, characterized in that, After the ULF-MRI structural imaging signal acquisition is completed, during the fourth time interval, the switching of the gradient magnetic field coil is stopped, the measurement magnetic field is maintained, and the target imaging area is restored to the near-zero magnetic field state, including: The current of the gradient magnetic field coil is controlled to return to zero within a preset time by the dynamic braking circuit, and the switching current applied to the gradient magnetic field coil is stopped, so that the gradient magnetic field coil is in a zero current state or a constant current state. The power supply to the measuring magnetic field coil is switched to linear operating mode to maintain the strength of the measuring magnetic field stable within a preset fluctuation range corresponding to the third preset strength; the preset fluctuation range is a sub-μT threshold. The net magnetic field strength of the target imaging area is monitored in real time, and the net magnetic field strength is kept below a fourth preset threshold; the fourth preset threshold is an nT level threshold.

9. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 8, characterized in that, The acquisition of OPM-MEG magnetoencephalogram (MEG) signals includes: During the fourth time interval, when the net magnetic field strength of the target imaging area is lower than the fourth preset threshold, the magnetic signal generated by the subject's brain nerve activity in the target imaging area is continuously collected by the OPM-MEG sensor array at a preset sampling frequency, and used as the OPM-MEG brain magnetic signal. For each acquisition time corresponding to the magnetic signal, a second time base tag generated based on the clock source is matched.

10. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 1, characterized in that, The method further includes: Based on the preset timing configuration of the first time interval, the second time interval, the third time interval, and the fourth time interval, the target imaging area is made to enter the magnetic field state suitable for ULF-MRI acquisition and the magnetic field state suitable for OPM-MEG acquisition in a unified magnetic environment. The execution loop is repeated multiple times based on a preset imaging protocol, with each preset timing sequence constituting an execution loop. Within a single execution loop, the acquired ULF-MRI structural imaging signal corresponds to a portion of the phase encoding line in the K-space, and the ULF-MRI structural imaging signals acquired in multiple execution loops are combined for three-dimensional structural reconstruction; For all operations within a single execution loop, corresponding absolute timestamps are generated based on the same clock source to align the ULF-MRI structural imaging signal and the OPM-MEG magnetoencephalogram signal on the same time axis.

11. The magnetic field timing control method for ULF-MRI and OPM-MEG according to claim 1, characterized in that, The magnetic field strength of the measured magnetic field is from 1 μT to 100 μT; The magnetic field strength of the prepolarized magnetic field is 10 mT to 100 mT.

12. A magnetic field timing control system for ULF-MRI and OPM-MEG, characterized in that, Suitable for brain imaging devices, the brain imaging devices include pre-polarized magnetic field coils, measuring magnetic field coils, gradient magnetic field coils, OPM-MEG sensor arrays, and target imaging regions; The system includes a memory and a processor; The processor is connected to the prepolarized magnetic field coil, the measurement magnetic field coil, the gradient magnetic field coil, and the OPM-MEG sensor array, respectively, to execute the steps of the magnetic field timing control method of ULF-MRI and OPM-MEG according to any one of claims 1 to 11.

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