An integrated beat frequency ultrasonic neuromodulation system and a driving method thereof

Abstract

The application relates to an integrated beat frequency ultrasonic neuromodulation system and a driving method thereof, and belongs to the technical field of neuromodulation and ultrasonic engineering. The application comprises a focused ultrasonic transducer module, a double-frequency signal generation module, a power amplification module, an impedance matching module, a control module, a power supply module and a neural electrophysiological acquisition module. The double-frequency signal generation module is electrically connected with the power amplification module, the power amplification module is electrically connected with the focused ultrasonic transducer module through the impedance matching module, the control module is in communication connection with the double-frequency signal generation module, the power amplification module and the neural electrophysiological acquisition module, and the power supply module provides working electric energy for each module. The application integrates double-frequency signal generation, power driving, impedance matching, transduction emission, signal acquisition and parameter control into the same system, adopts multiple ultrasonic carriers with different frequencies to share the same ultrasonic transducer of an acoustic aperture, makes focused sound spots located in the same area, and forms a stable beat frequency modulation field in the same physical aperture.

Description

Technical Field

[0001] This invention belongs to the field of neuromodulation and ultrasound engineering technology, and relates to an integrated beat-frequency ultrasound system for transcranial nerve modulation and its driving method. Background Technology

[0002] Transcranial ultrasound neuromodulation, due to its non-invasive nature, deep penetration, and high spatial resolution, has become an important technical approach for the intervention of neurological diseases and the regulation of brain function. For deep brain region modulation, achieving precise intervention on specific brain regions typically requires a small ultrasound focal zone to avoid collateral stimulation of surrounding non-target brain regions. Generally, to achieve millimeter-level focusing capability, the ultrasound carrier frequency usually needs to be in the hundreds of kilohertz range or higher. For example, when the sound wave frequency is approximately 300 kHz and the speed of sound in brain tissue is approximately 1500 m / s, the wavelength is approximately 5 mm, theoretically capable of forming a focused sound field with a diameter on the order of several millimeters, thus providing a means for precise stimulation of deep, small-volume brain regions.

[0003] However, existing research indicates that the effective frequencies truly relevant to neural rhythm regulation are often in the lower frequency range, such as a few hertz to tens of hertz, which are closer to brain rhythms, evoked rhythms, or other low-frequency neural activity characteristics. Compared to high-frequency ultrasound carrier waves, this type of low-frequency mechanical modulation is more conducive to matching the rhythmic response of the target neural network and is therefore considered to have greater potential for neuromodulation. The problem is that if low-frequency sound waves of a few hertz or tens of hertz are directly used to stimulate brain regions, their wavelengths will be much larger than the size of the target brain region (for example, the wavelength of a 10Hz sound wave in brain tissue will reach about 150m), making it impossible to focus the sound field within a few millimeters, thus failing to meet the needs of precise regulation of deep brain regions.

[0004] Therefore, how to obtain low-frequency rhythmic effects within the target area while maintaining the good focusing ability of high-frequency ultrasound has always been a key problem that urgently needs to be solved in the field of transcranial ultrasound neuromodulation. In other words, researchers hope to use high-frequency sound beams to achieve precise spatial delivery, while also hoping to create a low-frequency modulation effect within the focal zone to enhance the neuromodulation effect. However, there is an inherent contradiction in the frequency requirements of the two: high frequency is conducive to focusing, but does not directly correspond to the target low-frequency rhythm; low frequency is more conducive to rhythm modulation, but it is difficult to achieve focusing in small volumes.

[0005] To address the aforementioned contradictions, researchers proposed using beat-frequency ultrasound technology to achieve low-frequency mechanical effects with focused light in small volumes. However, the proposed scheme employs two or more transducers, aiming them at the same target brain region for irradiation. Because the multiple transducers emit ultrasound at different frequencies, the sound waves interfere within the same target brain region, forming a difference-frequency envelope. Theoretically, this approach attempts to resolve the aforementioned contradictions by utilizing the focusing capability of high-frequency carrier waves and the modulation capability of low-frequency difference-frequency envelopes. However, in engineering implementation, it faces unavoidable complex problems: First, multiple transducers need to cross the skull to achieve spatial co-focusing in a small, unseen deep brain region. Transducer installation angles, positional deviations, and individual skull geometric differences significantly reduce the accuracy of focal zone overlap. Second, to form stable interference in the target region, the sound waves emitted by each transducer must meet strict time synchronization and phase consistency requirements. However, differences in sound path length, thickness at different skull entry points, and the resulting reflections, scattering, attenuation, and phase distortions make it difficult to accurately calculate the arrival time and phase relationship of the sound waves, placing extremely high demands on the time delay and phase control of the excitation circuit system. This results in problems such as large system size, high installation space occupation, complex debugging process, insufficient repeatability, and high sensitivity to individual differences, which seriously restricts its engineering feasibility and clinical portability. Summary of the Invention

[0006] To address the problems of structural complexity, integration difficulties, and insufficient control stability caused by existing beat frequency ultrasound systems that rely on multiple transducers, multi-channel synchronization, and complex navigation, this invention provides an integrated beat frequency ultrasound neuromodulation system and its driving method. It integrates dual-frequency signal generation, power driving, impedance matching, transducer transmission, signal acquisition, and parameter control into the same system architecture, and uses a single focused ultrasound transducer to complete dual-frequency sound beam transmission, forming a stable beat frequency modulation field within the same physical aperture.

[0007] The objective of this invention is achieved through the following technical solution.

[0008] The present invention discloses an integrated beat-frequency ultrasound neuromodulation system, comprising a focused ultrasound transducer module, a dual-frequency signal generation module, a power amplification module, an impedance matching module, a control module, a power supply module, and an optional neurophysiological acquisition module.

[0009] The dual-frequency signal generation module is electrically connected to the power amplification module. The power amplification module is electrically connected to the focused ultrasound transducer module via the impedance matching module. The control module is communicatively connected to the dual-frequency signal generation module, the power amplification module, and the neurophysiological acquisition module. The power supply module provides working power to each module.

[0010] The focused ultrasonic transducer module preferably comprises a piezoelectric ceramic vibrator, upper and lower electrode plates, a backing layer, and an acoustic matching layer. The piezoelectric ceramic can be PZT-4, PZT-8, or an equivalent high electromechanical coupling material, with its thickness satisfying the thickness vibration equivalence relationship h=c / (2f) according to the center operating frequency f, where c is the longitudinal wave velocity in the piezoelectric material. To simultaneously stabilize dual-carrier signals radiating frequencies f1 and f2, the effective bandwidth coverage of the transducer should satisfy B≥|f1-f2|+Δf, where Δf is the frequency margin reserved to account for impedance drift and processing errors.

[0011] The impedance matching module employs a series-parallel inductor-capacitor network or a broadband transformer network to ensure that the equivalent reflection coefficients of the transducer at f1 and f2 simultaneously satisfy |Γ(f1)|≤Γ and |Γ(f2)|≤Γ, where Γ is a preset reflection threshold.

[0012] Furthermore, it can be integrated into a headband, headband, or fixed support structure. The geometric focal length, aperture, and installation angle of the focused ultrasound transducer are determined according to the depth range of the preset target brain region. The transducer focal length F and aperture D preferably satisfy F / D of 0.8 to 2.5 to balance the penetration depth and focal area size.

[0013] This invention also discloses a method for driving an integrated beat-frequency ultrasound neuromodulation system, comprising the following steps:

[0014] Step S1: Set the target carrier frequencies f1 and f2, carrier amplitudes A1 and A2, pulse width PW, pulse repetition frequency PRF, and duration T, where the difference frequency Δf=|f1-f2| is set as the target neural modulation frequency.

[0015] Step S2: A composite excitation signal is generated by a dual-frequency signal generation module driven by the same clock reference. This composite excitation signal is amplified by a power amplifier module, input to an impedance matching module, and then fed to a single focused ultrasound transducer. Because f1 and f2 share the same reference clock and the same power link, inter-channel time base drift and phase error can be reduced.

[0016] Step S3: A single focused ultrasonic transducer synchronously radiates two ultrasonic carrier waves with frequencies f1 and f2, respectively, at the same aperture. The ultrasonic carrier waves form an equivalent sound pressure p(t) = P1 cos(2πf1 t + θ1) + P2 cos(2πf2 t + θ2) at the focal region. When P1≈P2, the envelope term of p(t) is expressed as penv(t) = 2Pcos[π(f1-f2)t + Δθ / 2], where Δθ = θ1-θ2. At this time, a low-frequency beat frequency envelope is formed by superposition on the high-frequency focused sound field, realizing the control mechanism of "high-frequency focused transmission and low-frequency rhythmic effect".

[0017] Step S4: Pre-adjust A1 and A2 according to the envelope depth index M of the target focal region to obtain the initial amplitude ratio ρ = A1 / A2. The envelope depth index can be expressed as M = 2√(I1I2) / (I1+I2), where I1 and I2 are the sound intensities of f1 and f2 in the focal region, respectively. The control module optimizes the amplitude ratio ρ = A1 / A2 with the goal of maximizing M, so that the dual carriers maintain an effective difference frequency modulation depth under the conditions of transducer bandwidth limitation and skull attenuation difference.

[0018] Step S5: The control module calculates the control error based on the real-time acquired measured rhythm characteristic values, where R(k) is the target rhythm reference value and Y(k) is the current measured rhythm characteristic value, i.e., EEG, evoked potentials, or other neural activity indicators. It then corrects at least one of Δf, A1, A2, PW, or PRF according to the parameter update law. In the parameter update law, u(k) represents the stimulation parameter being adjusted at the current moment, such as any one of Δf, A1, A2, PW, or PRF, and u(k+1) represents the new value of that parameter at the next moment. The control module calculates the correction increment based on the error and directly adds it to the current parameter value, thereby changing the output characteristics of the ultrasound stimulation and achieving closed-loop control.

[0019] Step S6: The control module outputs updated control commands to the dual-frequency signal generation module and the power amplification module to complete the next cycle of stimulus parameter iteration. When the sound intensity, temperature rise, or neural feedback exceeds the safety threshold, the system automatically reduces the output duty cycle or stops transmitting.

[0020] Furthermore, in step S1, f1 and f2 are located in the range of 200 kHz to 5 MHz, and Δf is located in the range of 0.1 Hz to 100 Hz.

[0021] Furthermore, the frequency interval between f1 and f2 in step S1 is no greater than 60% of the transducer's -6 dB bandwidth.

[0022] Furthermore, the amplitude ratio of A1 to A2 in step S1 is 0.6 to 1.4.

[0023] Furthermore, the pulse width in step S1 is 0.1 ms to 50 ms.

[0024] Furthermore, the pulse repetition frequency in step S1 is 1 Hz to 5 kHz.

[0025] Furthermore, the rhythmic characteristic value Y(k) mentioned in step S5 is the target frequency band power, coherence, peak-to-peak value, or abnormal discharge event rate.

[0026] Beneficial effects:

[0027] 1. The present invention discloses an integrated beat frequency ultrasound neuromodulation system and its driving method, which uses multiple ultrasonic carriers of different frequencies to share an ultrasonic transducer with the same acoustic aperture, realizes high-frequency multi-carrier transmission within the same acoustic aperture, and makes the focused acoustic spot located in the same area, avoiding the time and space alignment problems faced by using multiple transducers, and its focused acoustic spot can reach the millimeter level.

[0028] 2. This invention discloses an integrated beat-frequency ultrasound neuromodulation system and its driving method. It achieves dual-frequency synchronous radiation using a single focused ultrasound transducer, and forms a low-frequency difference envelope in the target region through multiple ultrasound carriers of different frequencies. This reduces system size and alignment complexity while achieving a neuromodulation effect combining small-volume focusing in the high-frequency region with mechanical stimulation in the low-frequency region. This invention avoids the problems of large installation space and complex alignment errors associated with multi-transducer arrangements, significantly improving system integration and engineering feasibility.

[0029] 3. The present invention discloses an integrated beat frequency ultrasound neuromodulation system and its driving method, which optimizes the transducer bandwidth, impedance matching network and dual-frequency amplitude ratio in a coordinated manner, so that a single transducer maintains effective acoustic output at f1 and f2, thereby ensuring that a stable low-frequency difference frequency envelope can be formed in the focal zone and improving the consistency of modulation.

[0030] 4. The present invention discloses an integrated beat frequency ultrasound neuromodulation system and its driving method, which constructs an envelope depth index, a parameter optimization target, and a closed-loop parameter update law, so that there is a clear input, output, and control logic between dual-frequency transmission, feedback acquisition, and control commands, which can reduce the uncertainty brought about by purely functional descriptions.

[0031] 5. The integrated beat-frequency ultrasound neuromodulation system and its driving method disclosed in this invention, based on achieving the above-mentioned beneficial effects, are suitable for integration into a head-mounted or portable device, which is helpful for clinical, rehabilitation and home applications. Attached Figure Description

[0032] Figure 1 This is a schematic block diagram of the integrated beat frequency ultrasound neuromodulation system in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the principle of dual-frequency transmission and focal zone beat frequency formation using a single focused ultrasonic transducer in an embodiment of the present invention.

[0034] Figure 3 This is a closed-loop flowchart of parameter acquisition, control decision-making, and dual-frequency drive in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram illustrating the correspondence between the high-frequency carrier peak and the low-frequency difference envelope in an embodiment of the present invention.

[0036] Wherein: 1—Focused ultrasound transducer module, 2—Dual-frequency signal generation module, 3—Power amplification module, 4—Impedance matching module, 5—Control module, 6—Power supply module, 7—Neuro-electrophysiological acquisition module, 8—First carrier f1, 9—Second carrier f2, 10—Difference frequency envelope. Detailed Implementation

[0037] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0038] Example 1:

[0039] like Figure 1 As shown, the integrated beat-frequency ultrasound neuromodulation system provided in this embodiment includes a focused ultrasound transducer module 1, a dual-frequency signal generation module 2, a power amplification module 3, an impedance matching module 4, a control module 5, a power supply module 6, and a neurophysiological acquisition module 7. The dual-frequency signal generation module 2 generates composite drive signals with frequencies f_1 and f_2 based on the same crystal oscillator clock; the power amplification module 3 amplifies the composite drive signals; the impedance matching module 4 performs joint matching of the transducer's input impedance at the two operating frequencies; and the focused ultrasound transducer module 1 is responsible for converting the electrical signals into dual-frequency ultrasound signals and radiating them to the target brain region.

[0040] In a preferred embodiment, the focused ultrasound transducer module 1 employs a unit-type focused transducer with a center frequency of 800 kHz, using PZT-4 piezoelectric ceramic material, an aperture of 20 mm, and a focal length of 25 mm. The first carrier frequency f_1 is set to 800 kHz, the second carrier frequency f2 is set to 800.04 kHz, and the corresponding difference frequency Δf is 40 Hz. The impedance matching module 4, through a combination of series inductors and parallel capacitors, maintains the standing wave ratio (SWR) of the transducer at f1 and f2 simultaneously within a preset threshold.

[0041] Example 2:

[0042] like Figure 2 and Figure 3 As shown, control module 5 first receives the target frequency band power characteristics uploaded by neurophysiological acquisition module 7, and determines the difference frequency Δf according to the preset control target. Subsequently, dual-frequency signal generation module 2 outputs a composite signal s(t) = A1 cos(2πf1 t) + A2 cos(2πf2 t), which drives focused ultrasound transducer module 1 to transmit the first carrier wave 8 and the second carrier wave 9 after passing through power amplification module 3 and impedance matching module 4. The two carrier waves are superimposed in the focal region to form a difference frequency envelope 10, which generates rhythmic modulation on the target brain region.

[0043] When the target frequency band power is detected to be lower than the set threshold in real time, the control module 5 performs incremental correction on the parameter vector u=[A1,A2,Δf,PW,PRF] based on the error e(k)=R(k)-Y(k). Specifically, if the envelope depth index M decreases, the amplitude ratio of A1 to A2 is adjusted first; if the target rhythm deviates significantly, Δf is corrected first; if there is a risk of overstimulation, the duty cycle is reduced or the duration T is shortened. Through the above control logic, the system can maintain a relatively stable focal envelope output under different individual and coupling states.

[0044] Example 3:

[0045] like Figure 4 As shown, in the frequency domain, the system output is represented by two carrier peaks in the high-frequency region and their corresponding low-frequency difference envelope. The high-frequency carrier peaks are used to provide focusing transmission capability, while the low-frequency difference envelope is used to match the target neural rhythm, thereby achieving a control effect that combines high-frequency region recognition with low-frequency region action.

[0046] It should be noted that the transducer materials, structural dimensions, frequency parameters, closed-loop control strategies, and acquisition indicators in the above embodiments can be equivalently replaced or optimized according to the target brain region, application scenario, and safety standards. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the protection scope of this invention. The specific descriptions above further illustrate the purpose, technical solutions, and beneficial effects of the invention. It should be understood that the above descriptions are merely specific embodiments of this invention and are not intended to limit the protection scope of this invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. An integrated beat-frequency ultrasound neuromodulation system, characterized in that: It includes a focused ultrasound transducer module, a dual-frequency signal generation module, a power amplification module, an impedance matching module, a control module, a power supply module, and a neurophysiological acquisition module; The dual-frequency signal generation module is electrically connected to the power amplification module. The power amplification module is electrically connected to the focused ultrasound transducer module via the impedance matching module. The control module is communicatively connected to the dual-frequency signal generation module, the power amplification module, and the neurophysiological acquisition module. The power supply module provides working power to each module. The focused ultrasonic transducer module is composed of a piezoelectric ceramic vibrator, upper and lower electrode plates, a backing layer, and an acoustic matching layer. The piezoelectric ceramic is selected from PZT-4, PZT-8, or equivalent high electromechanical coupling materials. Its thickness satisfies the thickness vibration equivalence relationship h=c / (2f) according to the center working frequency f, where c is the longitudinal wave velocity in the piezoelectric material. In order to simultaneously stabilize the radiation of dual carrier signals with frequencies f1 and f2, the effective bandwidth coverage of the transducer should satisfy B≥|f1-f2|+Δf, where Δf is the frequency margin reserved to account for impedance drift and processing errors. The impedance matching module uses a series-parallel inductor-capacitor network or a broadband transformer network to ensure that the equivalent reflection coefficients of the transducer at f1 and f2 simultaneously satisfy |Γ(f1)|≤Γ and |Γ(f2)|≤Γ, where Γ is a preset reflection threshold.

2. The system as described in claim 1, characterized in that: It can be integrated into a headband, headband, or fixed bracket structure; the geometric focal length, aperture, and installation angle of the focused ultrasound transducer are determined according to the depth range of the preset target brain region, wherein the transducer focal length F and aperture D satisfy F / D of 0.8 to 2.5 to take into account both penetration depth and focal area size.

3. A method for driving the system as described in claim 1 or 2, characterized in that: Includes the following steps, Step S1: Set the target carrier frequencies f1 and f2, carrier amplitudes A1 and A2, pulse width PW, pulse repetition frequency PRF, and duration T, where the difference frequency Δf=|f1-f2| is set as the target neural modulation frequency; Step S2: The dual-frequency signal generation module is driven by the same clock reference to generate a composite excitation signal. The composite excitation signal is amplified by the power amplifier module and then input to the impedance matching module before being fed to a single focused ultrasound transducer. Since f1 and f2 share the same reference clock and the same power link, the time base drift and phase error between channels are reduced. Step S3: A single focused ultrasonic transducer synchronously radiates two ultrasonic carrier waves with frequencies of f1 and f2 on the same aperture. The ultrasonic carrier waves form an equivalent sound pressure p(t) = P1 cos(2πf1 t + θ1) + P2 cos(2πf2 t + θ2) at the focal region. When P1≈P2, the envelope term of p(t) is expressed as penv(t) = 2Pcos[π(f1-f2)t + Δθ / 2], where Δθ = θ1-θ2. At this time, a low-frequency beat frequency envelope is formed by superposition on the high-frequency focused sound field, realizing the control mechanism of "high-frequency focused transmission and low-frequency rhythmic effect". Step S4: Pre-adjust A1 and A2 according to the envelope depth index M of the target focal area to obtain the initial amplitude ratio ρ=A1 / A2; the envelope depth index can be expressed as M=2√(I1I2) / (I1+I2), where I1 and I2 are the sound intensities of f1 and f2 in the focal area, respectively; the control module optimizes the amplitude ratio ρ=A1 / A2 with the goal of maximizing M, so that the dual carriers maintain an effective difference frequency modulation depth under the conditions of transducer bandwidth limitation and skull attenuation difference; Step S5: The control module calculates the control error based on the real-time acquired current measured rhythm characteristic values. Where R(k) is the target rhythm reference value, and Y(k) is the current measured rhythm characteristic value, i.e., EEG, evoked potential, or other neural activity indicators; and the rhythm is updated according to the parameters. At least one of Δf, A1, A2, PW, or PRF is corrected; in the parameter update law, u(k) represents the stimulation parameter being adjusted at the current moment, such as any one of Δf, A1, A2, PW, or PRF, and u(k+1) represents the new value of the parameter at the next moment; the control module calculates the correction increment based on the error and directly adds it to the current parameter value, thereby changing the output characteristics of the ultrasound stimulation and realizing closed-loop control; Step S6: The control module outputs the updated control command to the dual-frequency signal generation module and the power amplification module to complete the next cycle of stimulation parameter iteration; when the sound intensity, temperature rise or neural feedback exceeds the safety threshold, the system automatically reduces the output duty cycle or stops transmitting.

4. The method as described in claim 3, characterized in that: In step S1, f1 and f2 are located in the range of 200 kHz to 5 MHz, and Δf is located in the range of 0.1 Hz to 100 Hz.

5. The method as described in claim 3, characterized in that: The frequency interval between f1 and f2 in step S1 is no greater than 60% of the transducer's -6 dB bandwidth.

6. The method as described in claim 3, characterized in that: The amplitude ratio of A1 to A2 in step S1 is 0.6 to 1.

4.

7. The method as described in claim 3, characterized in that: The pulse width in step S1 is 0.1 ms to 50 ms.

8. The method as described in claim 3, characterized in that: The pulse repetition frequency in step S1 is 1 Hz to 5 kHz.

9. The method as described in claim 3, characterized in that: The rhythmic characteristic value Y(k) mentioned in step S5 is the target frequency band power, coherence, peak-to-peak value, or abnormal discharge event rate.

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