A Fresnel intracranial ultrasound focusing device and method based on microwave-induced acoustics

Abstract

This invention discloses a Fresnel intracranial ultrasound focusing device and method based on microwave-induced acoustics. It combines the principle of microwave acoustics with the focusing technology of multilayer Fresnel microfluidic wavebands to form a Fresnel intracranial ultrasound focusing technique. The device includes a microwave and ultrasound generation module, an ultrasound signal acquisition system, and an image processing and analysis module. This device and method utilize microwave excitation of implanted Fresnel microfluidic wavebands to achieve focused, variable-focus, and adjustable-intensity ultrasound waves in deep brain tissue. Compared with traditional transcranial focused ultrasound and transcranial direct current stimulation techniques, this invention features deep penetration, variable focus, adjustable intensity, high-efficiency excitation, biocompatibility, and low cost, and has significant potential application value in fields such as neuromodulation and precise drug delivery.

Description

Technical Field

[0001] This invention belongs to the field of medical devices and optical medical imaging, specifically relating to a Fresnel intracranial ultrasound focusing device and method based on microwave acoustics. Background Technology

[0002] Neuromodulation technology, as a key component in the treatment of nervous system diseases, is widely used in the field of neuropsychiatry. With the continuous advancement of medical and biomedical engineering technologies, ultrasound therapy, by focusing ultrasound energy on the lesion area, utilizes the thermal, mechanical, and cavitation effects caused by focused ultrasound to achieve direct or adjunctive treatment of the lesion area without damaging normal tissue.

[0003] Currently, neuromodulation generally employs transcranial focused ultrasound (TCU). TCU has gained widespread attention due to its advantages in treating neurological diseases, including low cost, non-invasiveness, and ease of adaptation to closed-loop therapy. However, because of the impedance mismatch between high-frequency ultrasound waves and brain tissue, ultrasound energy attenuates and diffuses during propagation, making it difficult to precisely focus the ultrasound signal in the brain after passing through the skull. More importantly, the accuracy of the focusing target location and the precise control of ultrasound intensity play a crucial role in neuromodulation. Unfortunately, TCU has several drawbacks in terms of precision and control.

[0004] In addition, other modulation methods include transcranial direct current stimulation (TCD) and transcranial magnetic stimulation (TMS). For example, TCD delivers current to a specific target area to induce neuronal excitability, achieving non-invasiveness. However, due to the decrease in focusing characteristics with increasing depth of action and the disadvantage of low spatial resolution, it is difficult to provide stimulation to deep tissues, such as those below the cerebral cortex. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] Traditional transcranial focused ultrasound (TCUS) technology has limitations. Due to the attenuation, high reflection, and diffraction effects of high-frequency ultrasound waves by the human skull, focusing efficiency is generally low. Furthermore, TUS technology struggles to achieve focusing at different depths within the cranium. These factors limit its application in areas such as neuromodulation and precise drug delivery. Based on these shortcomings of existing technology, we propose a Fresnel intracranial ultrasound focusing device and method based on microwave-induced acoustics.

[0007] (II) Technical Solution

[0008] In this invention, the principle of microwave acoustics is utilized by a multilayer Fresnel microfluidic zone sheet implanted within the brain. Due to its implantation method, this invention significantly minimizes the influence of the skull on ultrasound focusing. Within the zone sheet, an electrolyte solution with strong microwave absorption properties is injected into a concentric ring-shaped Fresnel microfluidic channel. Utilizing the strong penetrating power of microwaves and the principle of microwave acoustics, the electrolyte solution in this single-layer Fresnel microfluidic zone sheet is excited by microwaves to generate high-frequency ultrasound waves with the same phase, achieving the conversion of electromagnetic energy into mechanical energy within the brain. More importantly, due to the coherence effect of sound waves and the axial symmetry of each unit ring in the zone sheet, this single-layer Fresnel microfluidic zone sheet will generate a high-resolution ultrasound focusing point along the axial direction.

[0009] Because multilayer Fresnel microfluidic zone sheets are implanted into the inner side of the skull, they can minimize the skull's reflection, scattering, and absorption loss of ultrasound energy. Furthermore, the zone sheets are made of carbon-based or silicon-based polymer materials, which have good biocompatibility and can minimize the invasive effects of the implanted device on biological tissues.

[0010] To address its technical problems, this invention provides a Fresnel intracranial ultrasound focusing device and method based on microwave acoustics.

[0011] A Fresnel intracranial ultrasound focusing device based on microwave acoustics is used to achieve microwave-induced ultrasound focusing at a specific depth in intracranial brain tissue. The device is characterized by comprising:

[0012] Microwave generating module, used to generate microwave output;

[0013] The ultrasound generating module employs a multilayer Fresnel microfluidic waveband, composed of stacked single-layer Fresnel microfluidic wavebands. Each single-layer Fresnel microfluidic waveband consists of microfluidic channels arranged in a concentric Fresnel ring pattern. These channels have fluid inlet and outlet ends, allowing electrolyte solution to be injected from the inlet and recovered from the outlet via a pump or syringe. The lateral dimension of the single-layer Fresnel microfluidic waveband, determined by the radius of the concentric Fresnel rings, is calculated mathematically based on the center frequency and focusing depth of the ultrasound waveband. The longitudinal dimension of the waveband, its thickness, is on the sub-millimeter or millimeter scale. The electrolyte solution absorbs microwaves and generates in-phase ultrasound waves based on microwave acoustics. The single-layer Fresnel microfluidic waveband achieves intracranial ultrasound focusing by radiating sound waves with symmetrical and in-phase characteristics. The concentric Fresnel rings in different layers of the Fresnel microfluidic waveband are used for ultrasound focusing at different depths.

[0014] An ultrasonic signal acquisition system, mainly composed of a unit-type ultrasonic probe or a ring array ultrasonic probe, is used to acquire time-domain ultrasonic signals.

[0015] The image processing and analysis module is used to process and analyze the signals obtained by the ultrasound imaging system to obtain a reconstructed image of brain tissue containing the focal location.

[0016] Preferably, the microwave generating module consists of a microwave source and an antenna. The microwave source operates as a pulsed or modulated continuous wave output with a repetition frequency on the order of kHz to MHz.

[0017] Preferably, the radius of the Fresnel concentric rings is given by the formula Obtain, where r n From the inside out n The radius of each ring, n Let f be a positive integer, and f be the acoustic focal length. The wavelength corresponds to the center frequency of the ultrasound.

[0018] Preferably, the multilayer Fresnel microfluidic waveband sheet has a thickness on the order of millimeters and can be implanted on the inside of the skull and the outside of the brain tissue.

[0019] Preferably, the Fresnel microfluidic waveband sheets with different stacked layers have different Fresnel concentric ring sizes; the number of stacked layers is determined by the number of required focusing depths, and the number does not exceed 5.

[0020] Preferably, the Fresnel intracranial ultrasound focusing device adopts a recyclable electrolyte solution design, in which the electrolyte solution is input or output from the port of a stacked channel of a multilayer Fresnel microfluidic waveband sheet via an air pump or syringe; the Fresnel intracranial ultrasound focusing device achieves focusing of ultrasound waves in different depth regions by injecting the recycled electrolyte solution into the microfluidic channels of other stacked layers.

[0021] Preferably, the antenna of the microwave generating module has an adjustable operating distance. Based on the principle that the microwave field strength received by the multilayer Fresnel microfluidic waveband plate decreases with the distance between the antenna opening and the ultrasonic generating module, a manual adjustment device or a motor control device is provided to change the distance between the antenna and the multilayer Fresnel microfluidic waveband plate to change the intensity of the excited ultrasonic wave, thereby adjusting the intensity of the focused ultrasound.

[0022] Preferably, the multilayer Fresnel microfluidic waveband sheet is made of one or more materials selected from polydimethylsiloxane (PDMS), polyethylene (PE), and polypropylene (PP).

[0023] Preferably, the electrolyte solution includes, but is not limited to, one or more of sodium chloride solution, calcium chloride solution, and magnesium chloride solution.

[0024] This invention also claims protection for a microwave-induced Fresnel intracranial ultrasound focusing method, used to achieve microwave-induced ultrasound focusing at a specific depth in intracranial brain tissue. It operates using the aforementioned microwave-induced Fresnel intracranial ultrasound focusing device. The specific steps of this Fresnel intracranial ultrasound focusing method are as follows:

[0025] Step S1: Place the multilayer Fresnel microfluidic waveband sheet inside the skull and make it adhere to and contact the brain tissue.

[0026] Step S2: Inject the electrolyte solution into the channel of a single-layer Fresnel microfluidic waveband sheet through the fluid input terminal and keep it sealed.

[0027] Step S3: The microwave generation module starts working, and the microwave source generates microwaves and outputs them through the antenna.

[0028] Step S4: The antenna of the microwave generation module irradiates the multilayer Fresnel microfluidic waveband sheet in the forward direction. After the electrolyte solution absorbs the microwave energy, it generates in-phase ultrasound waves. The ultrasound waves are focused in a specific depth region of the brain tissue based on the coherence effect. The ultrasound probe performs a B-scan to acquire time-domain ultrasound signals. The antenna is moved to change the distance between the antenna and the multilayer Fresnel microfluidic waveband sheet, thereby achieving ultrasound focusing of different intensities.

[0029] Step S5, adjust the focusing depth. The specific operation steps include: recovering the previously injected liquid from the channel in a single-layer microfluidic waveband through the fluid output end, and then injecting it into the channel in a single-layer Fresnel microfluidic waveband corresponding to different focusing positions; after the focusing is completed, repeat steps S3-S4 until the desired specific depth and intensity of ultrasonic focusing is achieved.

[0030] In step S6, the image processing and analysis module processes and analyzes the obtained ultrasound signal to obtain a reconstructed image of brain tissue containing the focal location.

[0031] (III) Beneficial Effects

[0032] Compared with the prior art, the present invention has significant positive technical effects, and its beneficial effects are reflected in at least the following six aspects.

[0033] (1) Based on microwave acoustics, high-intensity ultrasound focusing can be achieved by exciting the electrolyte solution or liquid metal in the multilayer Fresnel microfluidic waveband implanted in the cranium with microwaves. Compared with traditional transcranial focused ultrasound technology, this method avoids the problems of energy dissipation and phase shift caused by ultrasound waves penetrating the skull, and uses the deep penetration of microwaves to efficiently excite ultrasound waves in the cranium.

[0034] (2) The stacked multilayer Fresnel microfluidic waveband consists of multiple single-layer Fresnel microfluidic wavebands of different sizes. By injecting electrolyte solution into the channels of the single-layer Fresnel microfluidic wavebands at different levels, and by adjusting the distance between the antenna and the multilayer Fresnel microfluidic waveband, deep-penetrating intracranial ultrasound focusing with adjustable focal length and intensity can be achieved. The focusing depth is greater than 5 cm and the lateral dimension of the focal spot is less than 2 mm. Compared with the traditional transcranial stimulation method of implanting hydrophones, which requires repeated implantation surgeries to adjust the focusing depth, this method is simpler in adjusting the focusing depth and intensity.

[0035] (3) The multilayer Fresnel microfluidic waveband sheet made of one or more of the following materials: polydimethylsiloxane (PDMS), polyethylene (PE), and polypropylene (PP), and the electrolyte solution used to fill the microfluidic channel have good biocompatibility.

[0036] (4) Compared with traditional transcranial direct current stimulation technology, this method can effectively avoid medical safety problems caused by intracranial current stimulation.

[0037] (5) This invention can be applied to fields such as neuromodulation and precise drug delivery, and has the advantage of low cost. The thickness of the single-layer Fresnel microfluidic waveband is only on the sub-millimeter or millimeter scale, and the preparation material is carbon-based and silicon-based polymer. Compared with the traditional transcranial focused ultrasound technology, this method has low preparation technology requirements and low price.

[0038] (6) The liquid source for filling the microfluidic channel in this invention is abundant, and can be sodium chloride solution, calcium chloride solution, magnesium chloride solution and other electrolyte solutions. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the device structure for implementing the present invention.

[0040] Figure 2 This is a schematic diagram of the structure of any layer of a multilayer Fresnel microfluidic waveband sheet.

[0041] Figure 3 This is a physical image of a single-layer Fresnel microfluidic waveband structure, in which fluid can be injected from the input end via an air pump or syringe and recovered at the total output end.

[0042] Figure 4 This is a physical image of a multilayer Fresnel microfluidic zone plate structure (taking two single-layer zone plates stacked as an example).

[0043] Figure 5 This is a sound pressure map of a multilayer Fresnel microfluidic waveband sheet at an ultrasonic center frequency of 1MHz, obtained based on numerical simulation.

[0044] Figure 6This is the waveform of the A-scan signal received by the oscilloscope at the focal point of the ultrasonic target.

[0045] The components shown in the figure are named as follows: microwave source with selectable repetition rate and frequency 1-1, antenna or waveguide 1-2, skull 1-3, multilayer Fresnel microfluidic waveband 1-4, focused ultrasound focal point 1-5, brain tissue 1-6, ultrasound probe 1-7, signal amplifier 1-8, oscilloscope 1-9, computer 1-10, and function generator 1-11. Detailed Implementation

[0046] To address its technical problems, this invention provides a Fresnel intracranial ultrasound focusing device and method based on microwave acoustics. The technical solution of this invention will be further illustrated below through specific embodiments.

[0047] A schematic diagram of the device structure of this invention is shown below. Figure 1 As shown.

[0048] Figure 2 This is a schematic diagram of a single-layer structure in a multilayer Fresnel microfluidic zone plate. The white area represents the electrolyte solution-filled region, i.e., the ultrasonic wave generation region; the black area represents the non-liquid-filled region, i.e., the non-ultrasonic wave generation region. Under the condition that the center frequency of the ultrasonic wave is 1MHz, the geometric parameters of the zone plate are as follows: the ring radii (from the inside out) are... r 1 =8.7mm, r 2 = 12.3mm, r 3 = 15.2mm, r 4 = 17.6mm, r 5 = 19.7mm, r 6 = 21.7mm, r 7 = 23.5mm, r 8 = 25.2mm, r 9 = 26.8mm, thickness is 100μm. The specific formula is as follows:

[0049]

[0050] in, r n For the first n The radius of each ring (from the inside out). f The theoretical focal length, The wavelength corresponds to the center frequency of the ultrasound.

[0051] Figure 3 For the corresponding Figure 2 The image shows a physical example of a single-layer zone plate. The main components include the zone plate itself, input terminals, and output terminals. The fabrication steps of the zone plate include: mixing the polymer and a curing agent, preparing a polymer film, thermosetting the polymer, preparing a photolithography mold for the zone plate, photolithography of the polymer, and separation and bonding of the zone plate. The input and output terminals are constructed using an air pump or a syringe.

[0052] Figure 4 This is a physical diagram of a multi-layer zone plate, which can be achieved by stacking single-layer zone plates concentrically or non-concentrically.

[0053] A multilayer Fresnel microfluidic waveband was implanted into the inner side of the skull. An electrolyte solution was injected into a channel in a single-layer Fresnel microfluidic waveband through a fluid input terminal and kept sealed.

[0054] A microwave acoustic system was constructed using the simplest traditional single-probe scanning system. This system uses a 3GHz pulsed microwave source as the signal excitation source. The generated pulsed microwaves are transmitted to the antenna via a coaxial cable through the center of a rotating motor. The antenna then radiates vertically from above the skull onto a multilayer Fresnel microfluidic waveband in linear, circular, or elliptical polarization.

[0055] Under the irradiation of pulsed or modulated high-power microwaves, the electrolyte solution in a single-layer Fresnel microfluidic waveband channel undergoes highly efficient microwave-to-ultrasound energy conversion. In this process, microwave electromagnetic energy is first converted into heat energy, and then, through the thermoacoustic effect, finally into mechanical energy, propagating outwards in the form of ultrasonic waves. Because the propagation speed of microwaves is much greater than that of ultrasonic waves, the ultrasonic waves generated in this single-layer Fresnel microfluidic waveband channel have the same phase. The in-phase sound waves radiated by this single-layer Fresnel microfluidic waveband are symmetrical about the central axis, ultimately generating an ultrasonic focusing target point along the axial direction at a specific depth. Figure 5 .

[0056] Furthermore, by flexibly switching between different layers of microfluidic channels, the focal length can be adjusted to achieve different depths of focusing; by controlling the distance between the antenna and the multi-layer Fresnel microfluidic waveband, the ultrasonic pressure at the focusing target can be adjusted.

[0057] Subsequently, an A-scan was performed manually using the ultrasonic probe to obtain thermoacoustic signals, as shown below. Figure 6 This system uses an Olympus-supplied immersion non-focused ultrasonic probe to detect thermoacoustic signals. The probe has a diameter of 15.8 mm, an effective response area of ​​12.7 mm, and a center frequency of 2.25 MHz. The signal is amplified by a preamplifier, input to the PCI-5122 data acquisition card, and stored on the computer.

[0058] Finally, an ultrasonic probe is used to accurately locate the ultrasonic focusing target and analyze the signal intensity. Data processing software is then used to process the A-scan signal of the target object.

[0059] The specific embodiments described in this application are merely illustrative examples of the main ideas of the present invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A Fresnel intracranial ultrasound focusing device based on microwave acoustics, used to achieve microwave-induced ultrasound focusing at a specific depth in intracranial brain tissue, characterized in that, The Fresnel intracranial ultrasound focusing device includes, Microwave generating module, used to generate microwave output; The ultrasonic wave generating module employs a multi-layer Fresnel microfluidic zone plate, composed of stacked single-layer Fresnel microfluidic zone plates. Each single-layer Fresnel microfluidic zone plate consists of microfluidic channels arranged in a concentric Fresnel ring pattern. These channels have fluid inlet and outlet ends, allowing electrolyte liquid to be injected from the inlet end and recovered from the outlet end via a pump or syringe. The lateral dimension of the single-layer Fresnel microfluidic zone plate, i.e., the length of the lateral region determined by the radius of the concentric Fresnel rings, is calculated mathematically based on the center frequency and focusing depth of the ultrasonic wave. The longitudinal dimension of the zone plate, i.e., its thickness, is... The electrolyte liquid is used to absorb microwaves and generate in-phase ultrasound waves based on microwave acoustics; the monolayer Fresnel microfluidic waveband achieves intracranial ultrasound focusing by radiating sound waves with symmetrical and in-phase characteristics; Fresnel microfluidic wavebands with different stacked layers have different Fresnel concentric ring sizes; the Fresnel concentric rings in different layers of Fresnel microfluidic wavebands are used for ultrasound focusing at different depths; the Fresnel intracranial ultrasound focusing device achieves ultrasound focusing in different depth regions by injecting the recovered electrolyte liquid into the microfluidic channels of other stacked layers; An ultrasonic signal acquisition system, mainly composed of a unit-type ultrasonic probe or a ring array ultrasonic probe, is used to acquire time-domain ultrasonic signals. The image processing and analysis module is used to process and analyze the signals obtained by the ultrasound signal acquisition system to obtain a reconstructed image of brain tissue containing the focal location.

2. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The microwave generation module consists of a microwave source and an antenna. The microwave source operates as a pulsed or modulated continuous wave output with a repetition frequency on the order of kHz-MHz.

3. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The radius of the Fresnel concentric rings is given by the formula Obtain, where r n Let f be the radius of the nth ring from the inside out, where n is a positive integer, f is the acoustic focal length, and λ is the wavelength corresponding to the center frequency of the ultrasound.

4. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The multilayer Fresnel microfluidic waveband sheet is on the order of millimeters in thickness and can be implanted on the inside of the skull and the outside of the brain tissue.

5. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The number of stacked layers is determined by the number of depths of focus required, and the number shall not exceed 5.

6. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 4, characterized in that: The Fresnel intracranial ultrasound focusing device adopts a recyclable electrolyte liquid design, and the electrolyte liquid is input or output from a port of a stacked layer channel of a multilayer Fresnel microfluidic waveband sheet through an air pump or needle.

7. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The antenna of the microwave generating module has an adjustable operating distance. Based on the principle that the microwave field strength received by the multilayer Fresnel microfluidic waveband plate decreases with the distance between the antenna opening and the ultrasonic generating module, a manual adjustment device or a motor control device is provided to change the distance between the antenna and the multilayer Fresnel microfluidic waveband plate to change the intensity of the excited ultrasonic wave, thereby adjusting the intensity of the focused ultrasound.

8. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The multilayer Fresnel microfluidic waveband sheet is made of one or more materials selected from polydimethylsiloxane (PDMS), polyethylene (PE), and polypropylene (PP).

9. The Fresnel intracranial ultrasound focusing device based on microwave acoustics according to claim 1, characterized in that: The electrolyte liquid includes one or more of sodium chloride solution, calcium chloride solution and magnesium chloride solution.

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