A focused transcranial magnetoacoustic coupling stimulation device

Abstract

The present invention relates to a focused transcranial magnetoacoustic coupling stimulation device and method. The stimulation device includes: an ultrasonic focusing module for emitting and adjusting focused ultrasonic waves; a stimulation object fixing module for fixing the stimulation object; a stimulation current detection module for monitoring the current density at the focal point in real time; a control module connected to the ultrasonic focusing module, the stimulation object fixing module, and the stimulation current detection module, for controlling the ultrasonic emission and waveform output of the ultrasonic focusing module, for controlling the multi-directional movement of the stimulation object, and for controlling the real-time detection and current density reconstruction of the stimulation current detection module. The above device and method in the present invention can achieve non-invasive brain electrical stimulation with high spatial resolution.

Description

Technical Field

[0001] The present invention relates to the field of transcranial stimulation, and particularly to a focused transcranial magnetoacoustic coupling stimulation device and method. Background Art

[0002] Transcranial magnetoacoustic coupling neuromodulation technology is a new type of brain stimulation technology, that is, using the coupling effect of magnetic field and ultrasonic wave to generate an electric field, and then regulating nerve activities. Different from pure electrical, magnetic, optical, and acoustic regulation means, transcranial magnetoacoustic coupling neuromodulation is a composite nerve stimulation technology that combines sound field and magnetic field, and realizes precise electrical regulation of nerve tissue by means of the high penetration depth and high focusing property of low-intensity focused ultrasound on the brain. Common transcranial nerve stimulations such as transcranial direct current stimulation and transcranial magnetic stimulation currently cannot achieve millimeter-level high-resolution focusing and are difficult to achieve stimulation of deep brain regions. Transcranial magnetoacoustic coupling stimulation has the advantages of both stimulation focusing and stimulation depth. Since the electric field strength of the focused electric field in transcranial magnetoacoustic coupling stimulation is jointly determined by the ultrasonic sound pressure at the focal point and the magnetic induction intensity of the static magnetic field, the magnetoacoustic coupling focused magnetic field intensity in transcranial magnetoacoustic technology is relatively low. Summary of the Invention

[0003] The purpose of the present invention is to provide a focused transcranial magnetoacoustic coupling stimulation device and method for realizing non-invasive electrical stimulation of the brain with high spatial resolution.

[0004] To achieve the above purpose, the present invention provides the following solutions:

[0005] A focused transcranial magnetoacoustic coupling stimulation device, the stimulation device includes:

[0006] An ultrasonic focusing module for emitting and regulating focused ultrasonic waves;

[0007] A stimulation object fixing module for fixing the stimulation object;

[0008] A stimulation current detection module for monitoring the current density at the focal point in real time;

[0009] A control module connected to the ultrasonic focusing module, the stimulation object fixing module, and the stimulation current detection module, for controlling the ultrasonic emission and waveform output of the ultrasonic focusing module, and also for controlling the multi-directional movement of the stimulation object, and also for controlling the real-time detection and current density reconstruction of the stimulation current detection module.

[0010] Optionally, the ultrasonic focusing module includes:

[0011] An annular phased array for emitting focused ultrasonic waves;

[0012] An ultrasonic transmitting and receiving subsystem connected to the annular phased array for regulating the waveform of the focused ultrasonic waves.

[0013] Optionally, the stimulation object fixing module includes:

[0014] A rat fixing frame for fixing the experimental rat;

[0015] A three-dimensional control subsystem, connected to the rat fixing frame, for performing three-dimensional control on the rat fixing frame.

[0016] Optionally, the stimulation current detection module includes:

[0017] A detection coil for receiving the induced electric field signal generated by the motional current;

[0018] A signal processing subsystem, connected to the detection coil, for determining the current density at the monitoring focus point based on the induced electric field signal.

[0019] Based on the above method in the present invention, the present invention further provides a focused transcranial magnetoacoustic coupling stimulation method, and the stimulation method includes:

[0020] Obtaining the magnetic vector potential, the electric scalar potential, and the eddy current density;

[0021] Performing spatio-temporal separation on the magnetic vector potential, the electric scalar potential, and the eddy current density to obtain a Poisson equation satisfied by the spatial component of the electric field scalar potential;

[0022] Based on the Poisson equation, determining the spatial component equation of the induced current density in the reciprocity process;

[0023] Solving the spatial component equation to obtain the current density at the target point in a specific brain region.

[0024] Optionally, the expression of the Poisson equation is as follows:

[0025]

[0026] ▽ represents the divergence operator, respectively represent the magnetic vector potential The spatial component of the electric scalar potential u2(r,t).

[0027] Optionally, the expression of the spatial component equation of the induced current density in the reciprocity process is as follows:

[0028]

[0029] where σ is the conductivity of the target point in a specific brain region.

[0030] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0031] The present invention provides a focused transcranial magnetoacoustic coupling stimulation device, which includes: an ultrasonic focusing module for emitting and adjusting focused ultrasonic waves; a stimulation object fixing module for fixing the stimulation object; a stimulation current detection module for real-time monitoring of the current density at the focal point; and a control module connected to the ultrasonic focusing module, the stimulation object fixing module, and the stimulation current detection module, for controlling the ultrasonic emission and waveform output of the ultrasonic focusing module, for controlling the multi-directional movement of the stimulation object, and for controlling the real-time detection and current density reconstruction of the stimulation current detection module. The device in the present invention can achieve non-invasive brain stimulation with high spatial resolution by setting the above modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a schematic structural diagram of a focused transcranial magnetoacoustic coupling stimulation device according to an embodiment of the present invention.

[0034] Symbol Explanation:

[0035] 1 - Static magnetic field; 2 Ring phased array; 3 - Rat fixing frame; 4 - Three-dimensional control subsystem; 5 - Computer control subsystem; 6 - Detection coil; 7 - Signal processing subsystem; 8 - Ultrasonic transmission and reception subsystem. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0037] The purpose of the present invention is to provide a focused transcranial magnetoacoustic coupling stimulation device and method for achieving non-invasive brain electrical stimulation with high spatial resolution.

[0038] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0039] The principle of transcranial magnetoacoustic coupling stimulation in the present invention is as follows: The object to be stimulated is placed in a static magnetic field 1. The focused ultrasonic waves emitted by the annular phased array 2 and the static magnetic field 1 act on the stimulation object together. Utilizing the concentric focusing characteristics of the annular phased array 2, it has the advantages of excellent focusing ability and low sidelobes at the center point, achieving focused stimulation of specific brain region targets of the stimulated object. At the same time, the detection coil 6 is used to receive the induced electrical signals generated by the motional electrostimulation in the region where the focused ultrasonic waves and the static magnetic field 1 act together, realizing real-time monitoring of the motional current signals at the focus point. The prominent advantages of this method are as follows: First, the static magnetic field 1 for stimulation can be a halbach magnet or a U-shaped permanent magnet, or it can also be a superconducting magnet for magnetic resonance. The magnetic field intensity of the superconducting magnet for magnetic resonance can be 1.5T, 3T, or 9.4T; Second, the detection coil 6 is used to realize real-time monitoring of the stimulation current and stimulation position of the focused transcranial magnetoacoustic coupling stimulation; Third, the inherent focusing characteristics of the annular phased array 2 are used to achieve focused magnetoacoustic coupling stimulation. To achieve stimulation at different specific positions, the three-dimensional control subsystem 4 is used to control the fixed position of the stimulation object to achieve stimulation at different specific positions. The annular phased array 2 in the present invention is non-magnetic and can be directly applied in the static magnetic field 1 of magnetic resonance, is compatible with the magnetic resonance system, and is easy to realize the integration of detection imaging and stimulation treatment. The above-mentioned device and scheme in the present invention will be introduced in detail with reference to the accompanying drawings as follows:

[0040] Figure 1 FIG. is a schematic structural diagram of a focused transcranial magnetoacoustic coupling stimulation device according to an embodiment of the present invention, as Figure 1 shown, the device includes: an ultrasonic focusing module, a stimulation object fixing module, a stimulation current detection module, and a control module;

[0041] The control module mainly refers to the computer control subsystem 5, whose function is to control the ultrasonic emission and waveform output of the ultrasonic focusing module, control the multi-directional movement of the stimulation object, and control the real-time detection and current density reconstruction of the stimulation current detection module. Therefore, the control module is connected to the ultrasonic focusing module, the stimulation object fixing module, and the stimulation current detection module.

[0042] The ultrasonic focusing module includes a circular phased array 2 and an ultrasonic transmitting and receiving subsystem 8. The ultrasonic focusing module utilizes the inherent focusing characteristics of the circular phased array 2. The size of a single array element of the circular phased array 2 can be autonomously set according to the size of the stimulation target and the focusing focal spot. The frequency range of a single array element is within 0.5 MHz - 5 MHz, and the focal length is within 50 mm - 200 mm. The waveform emitted by the circular array is adjusted by the ultrasonic transmitting and receiving subsystem 8 under the control of the computer control subsystem 5. The waveform can be a quasi-continuous pulse train or a single pulse, and the amplitude is adjustable from 1 V to 200 V. The ultrasonic wave emitted by the circular phased array 2 is orthogonal to the static magnetic field 1. The ultrasonic focusing module and the stimulation object fixing module are coupled through an ultrasonic coupling agent, and the coupling agent can be a solid coupling agent or a liquid coupling agent.

[0043] The stimulation object fixing module includes a rat fixing frame 3 and a three-dimensional control subsystem 4. In the present invention, the rat transcranial stimulation is used as an implementation mode for description. The function of this module is to achieve precise stimulation of any brain region of the rat located on the rat fixing frame. In this application, the focusing target of the circular phased array has been determined. To achieve precise stimulation of any brain region, the three-dimensional control of the rat fixing frame 3 is realized by the three-dimensional control subsystem 4 under the control of the computer control subsystem 5 under the guidance of the rat brain region localization spectrogram. The stimulation object, such as a rat, is first fixed at the central position of the rat fixing frame 3, and it is ensured that the position between the stimulated object rat and the rat fixing frame 3 remains unchanged while the rat fixing frame 3 is moving. The stimulated object rat on the rat fixing frame 3 and the circular phased array 2 are coupled through a coupling agent.

[0044] The static magnetic field 1 for stimulation can be provided by a halbach magnet or a U-shaped permanent magnet, or can be provided by a magnetic resonance superconducting magnet. The magnetic field intensity of the magnetic resonance superconducting magnet can be 1.5 T, 3 T, or 9.4 T. The stimulation object is placed in the static magnetic field 1 and the circular phased array 2, and the static magnetic field 1 is orthogonal to the ultrasonic wave emitted by the circular phased array 2.

[0045] The stimulation current detection module includes a detection coil 6 and a signal processing subsystem 7. First, under the coupled stimulation of the circular phased array 2 and the static magnetic field 1, the detection coil 6 receives the induced electric field signal generated by the motional current, and the received induced electric field signal directly obtains the target current density of the specific brain region of the stimulation object through the conductivity inversion algorithm. The method for real-time monitoring of the current density is as follows:

[0046] When solving the reciprocal current density forward problem, the magnetic field generated by passing a current through the coil in the surrounding space is called the primary magnetic field, and the magnetic field in the space excited by the induced eddy current in the stimulation object is called the secondary magnetic field. For biological tissues, the secondary magnetic field is much smaller than the primary magnetic field and can be ignored. According to Faraday's law of electromagnetic induction, the vortex electric field can be approximately expressed as:

[0047]

[0048] Among them, ▽ represents an operator, E2 represents the vortex electric field intensity, μ represents the magnetic permeability of the stimulated object, t represents time, H represents the primary magnetic field generated by the external current in the coil in vacuum, and for biological tissues, it can be expressed as the total magnetic field intensity in space. According to Ampere's circuital law, H can be expressed as:

[0049] ▽×H = J e2 (2)

[0050] J e2 represents the current density. According to the current continuity theorem, and by separating the magnetic vector potential, electric scalar potential, and eddy current density in space and time, the Poisson equation satisfied by the spatial component of the electric field scalar potential is obtained

[0051]

[0052] where ▽ is the divergence operator, respectively represent the magnetic vector potential the spatial components of the electric scalar potential u2(r,t), then the spatial component of the induced current density in the reciprocity process can be expressed as:

[0053]

[0054] When solving the inverse problem of reciprocity current density, the spatial component of the electric scalar potential calculated in formula (4) is used to discretize it, and the initial conductivity is repeatedly iterated using finite differences to obtain the conductivity σ of the target point in a specific brain region. Further, the current density at the target point in the specific brain region is obtained from the conductivity and the static magnetic field 1.

[0055] When the transcranial focused magnetoacoustic coupling stimulation device is operating inside the magnetic resonance magnet, the current density monitoring of the target point in a specific brain region can be directly achieved using the magnetic resonance electrical property imaging method. One implementation method is as follows:

[0056] First, the transverse magnetic field intensity component H of the magnetic resonance radiofrequency field is obtained in combination with the stimulated object x and H y , then a differential equation of the magnetic field intensity of the radiofrequency field and the total current density of the target point in the specific brain region to be measured is established, and by introducing a vector function, an integral weak form of the magnetic field intensity of the radiofrequency field and the total current density is established. At the same time, using the condition that the divergence of the magnetic field intensity is zero, the total current density of the target point in the specific brain region is obtained through a bi-variational method. This method does not require an additional detection coil to receive the induced electric field of the target point in the specific brain region to be measured, and directly uses the B1-mapping imaging technology of the nuclear magnetic resonance imaging method to actually measure H x and H yAfter the components, by combining Gauss' magnetic flux theorem and Ampere's law, first establish the longitudinal component of the total current density, and respectively obtain the current density distribution of the target points in specific brain regions based on the double variational of the two transverse components of the magnetic field strength, realizing the real-time performance of stimulation and detection imaging, and simplifying the system.

[0057] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts among the various embodiments, reference can be made to each other.

[0058] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A focused transcranial magnetoacoustic coupling stimulation device, characterized in that The stimulation device includes: An ultrasonic focusing module for emitting and adjusting focused ultrasonic waves; the ultrasonic focusing module includes: An annular phased array for emitting focused ultrasonic waves; An ultrasonic transmitting and receiving subsystem connected to the annular phased array for adjusting the waveform of the focused ultrasonic waves; A stimulation object fixing module for fixing the stimulation object; the stimulation object fixing module includes: A rat fixing rack for fixing experimental rats; A three-dimensional control subsystem connected to the rat fixing rack for performing three-dimensional control on the rat fixing rack; A stimulation current detection module for monitoring the current density at the focal point in real time; A control module connected to the ultrasonic focusing module, the stimulation object fixing module, and the stimulation current detection module for controlling the ultrasonic emission and waveform output of the ultrasonic focusing module, for controlling the multi-directional movement of the stimulation object, and for controlling the real-time detection and current density reconstruction of the stimulation current detection module; The current density reconstruction specifically includes the following steps: Obtaining the magnetic vector potential, electric scalar potential, and eddy current density; Performing spatio-temporal separation on the magnetic vector potential, the electric scalar potential, and the eddy current density to obtain a Poisson equation satisfied by the spatial component of the electric field scalar potential; the expression of the Poisson equation is as follows: where ▽ represents the divergence operator, respectively represent the magnetic vector potential the spatial components of the electric scalar potential u2(r,t); Based on the Poisson equation, determining the spatial component equation of the induced current density in the reciprocity process; the expression of the spatial component equation of the induced current density in the reciprocity process is as follows: where σ is the conductivity of the target in a specific brain region; Solving the spatial component equation to obtain the current density at the target in a specific brain region.

2. The focused transcranial magnetoacoustic coupling stimulation device according to claim 1, wherein The stimulation current detection module includes: A detection coil for receiving the induced electric field signal generated by the motional current; A signal processing subsystem connected to the detection coil for determining the current density at the monitored focal point based on the induced electric field signal.

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