A skull conforming acoustic interface device for an ultrasound brain-computer interface and a design and preparation method thereof

Abstract

The application discloses a skull conformal acoustic interface device for an ultrasonic brain-computer interface and a design and preparation method, relates to the technical field of ultrasonic brain-computer interfaces, and comprises the following from outside to inside of the skull: a brain-computer interface integrated layer, a transducer coupling layer, a skull conformal adhesion layer, an acoustic compensation functional layer and a mechanical positioning layer; the brain-computer interface integrated layer is used for accommodating a brain-computer interface sensing module; the transducer coupling layer is used for forming acoustic coupling connection with an ultrasonic transducer and limiting the thickness of a coupling medium layer; the skull conformal adhesion layer has a conformal adhesion surface which is used for adhering to the outer surface of the skull; the acoustic compensation functional layer is used for correcting acoustic distortion introduced by the skull; and the mechanical positioning layer is used for limiting the relative position between the device and the skull; the device provides an ultrasonic transmission path with individualized phase compensation for the ultrasonic transducer and provides a stable acoustic input basis which can be calibrated and predicted for a closed-loop ultrasonic brain-computer interface.

Description

Technical Field

[0001] This application relates to the field of ultrasound brain-computer interface technology, and in particular to a cranial conformal acoustic interface device for ultrasound brain-computer interfaces and its design and fabrication method. Background Technology

[0002] Ultrasonic brain-computer interfaces (BCIs) utilize low-intensity focused ultrasound (HIFU) to achieve non-invasive access to deep brain regions, showing significant application potential in scenarios such as sleep regulation, emotional circuit intervention, motor function rehabilitation, and closed-loop control of neurological diseases. Transcranial ultrasound BCIs typically include an ultrasound transducer, a coupling medium, and a head fixation device. In related technologies, to achieve transcranial ultrasound energy transmission, a planar transducer is usually used in conjunction with a water-filled bladder, gel layer, or mechanical scaffold to position the transducer at a specific location on the head, allowing the ultrasound beam to enter the skull at a certain angle and focus on a target point within the brain.

[0003] However, the outer surface of the skull has a unique and complex curvature, not a regular plane or sphere. When a planar transducer is used in conjunction with a water-filled bladder or gel layer, a coupling layer with varying thickness across the individual skull surface inevitably forms between the transducer end face and the individual skull. The thickness of this coupling layer varies significantly at different locations within the acoustic window region, resulting in different coupling layer thicknesses for the ultrasound beam at different lateral positions. This leads to changes in the acoustic path difference between different propagation paths, introducing a non-negligible phase error in addition to skull distortion. Furthermore, the flexible water-filled bladder or gel layer in related technologies is affected by wearing pressure, posture, and filling conditions with each wear, causing its thickness distribution to change accordingly. This results in the phase error introduced by the coupling layer being non-repeatable across multiple wears. When this phase error introduced by the coupling layer is superimposed on the individual skull's uneven thickness, density, and spatial differences in sound velocity, the actual wavefront phase distribution of the ultrasound beam after passing through the skull deviates significantly from the design value. The focal point deviates from the target brain region, and the sound pressure intensity at the focal point decreases and fluctuates violently. Ultimately, this results in the following: when the same subject wears the device at different times, the actual focal position in the brain can deviate by several millimeters to centimeters, and the standard deviation of sound pressure dose exceeds 30%; for closed-loop ultrasound brain-computer interface systems, the instability of acoustic input directly leads to the inability to separate the variation of neural response signals from changes in brain state, the system cannot establish a stable input-output mapping relationship, and closed-loop regulation fails. Summary of the Invention

[0004] The purpose of this application is to provide a cranial conformal acoustic interface device for ultrasound brain-computer interfaces and its design and fabrication method, which can achieve high sound field repeatability of ultrasound brain-computer interfaces during repeated wear and long-term use, and provide a calibrable and predictable stable acoustic input basis for closed-loop ultrasound brain-computer interfaces.

[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a craniosynthetic acoustic interface device for ultrasound brain-computer interfaces, comprising: A brain-computer interface integration layer, wherein the brain-computer interface integration layer is disposed on the side closest to the skull, and is used to accommodate the brain-computer interface sensing module; A transducer coupling layer is disposed on the side of the brain-computer interface integration layer away from the skull. It is used to accommodate the coupling medium layer and form an acoustic coupling connection with the ultrasound transducer through the coupling medium layer. The transducer coupling layer is used to limit the thickness of the coupling medium layer. A cranial conformal fitting layer is disposed on the side of the transducer coupling layer away from the brain-computer interface integration layer. The cranial conformal fitting layer has a conformal fitting surface facing the outer surface of the skull of the target acoustic window area. The curved shape of the conformal fitting surface matches the outer surface shape of the target acoustic window area of ​​the individual skull and is used to fit the outer surface of the skull in the use state. An acoustic compensation functional layer is disposed on the side of the cranial conformal fitting layer away from the transducer coupling layer, and is used to perform phase modulation and wavefront shaping on the ultrasound waves passing through the skull to correct the acoustic distortion introduced by the skull. A mechanical positioning layer, which is connected to at least one of the brain-computer interface integration layer, the transducer coupling layer, the cranial conformal fitting layer, or the acoustic compensation functional layer, is used to cooperate with an external fixation device to define the relative position between the cranial conformal acoustic interface device and the skull. The cranial conformal layer, the acoustic compensation layer, and the transducer coupling layer together constitute the acoustic channel for transcranial ultrasound propagation. The acoustic channel is used to provide an ultrasound transmission path with individualized phase compensation between the ultrasound transducer and the intracranial target area.

[0006] Optionally, the conformal fitting surface is provided with at least one of the following: a limiting edge, a flexible sealing ring, a coupling agent receiving groove, and an exhaust channel; the limiting edge is provided to protrude circumferentially along the conformal fitting surface, the coupling agent receiving groove is recessed in the conformal fitting surface, and the exhaust channel penetrates the cranial conformal fitting layer and communicates the coupling agent receiving groove with the outside.

[0007] Optionally, the acoustic compensation functional layer is a continuous thickness acoustic lens, and the thickness distribution of the continuous thickness acoustic lens is determined according to the compensation phase distribution corresponding to the target brain region; the compensation phase distribution is calculated based on the geometric parameters, sound velocity distribution, density distribution and attenuation coefficient distribution of the individual skull.

[0008] Optionally, the acoustic compensation functional layer is a discrete metasurface acoustic interface, which is composed of multiple discretely arranged phase compensation units. Each phase compensation unit has an independent phase delay, which is determined by the local structural parameters corresponding to the phase compensation unit. The local structural parameters include at least one of unit height, porosity, material acoustic impedance, or local channel length.

[0009] Optionally, the acoustic compensation functional layer is a multi-layer composite acoustic interface, which includes an inner layer adjacent to the cranial conformal fitting layer, an outer layer away from the cranial conformal fitting layer, and an intermediate layer located between the inner layer and the outer layer. The inner layer, the outer layer, and the intermediate layer have different acoustic impedances. The inner layer is used to adjust the focusing position and focusing shape of the sound beam, the outer layer is used to compensate for the phase distribution, and the intermediate layer is used to reduce the acoustic impedance difference between the cranial conformal fitting layer and the transducer coupling layer.

[0010] Optionally, the brain-computer interface sensing module included in the brain-computer interface integration layer includes at least one of an EEG electrode, a functional near-infrared probe, an inertial measurement unit, a temperature sensor, a pressure sensor, and an acoustic coupling status detector; the pressure sensor is disposed between the cranial conformal fitting layer and the brain-computer interface integration layer, and the acoustic coupling status detector is disposed in the cranial conformal fitting layer or the transducer coupling layer.

[0011] Optionally, the mechanical positioning layer is provided with positioning marks for constraining the wearing posture; the mechanical positioning layer is also provided with buckles, slots or threaded interfaces for detachable connection with headbands, straps or helmets.

[0012] Secondly, this application provides a method for designing and fabricating a craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces, including: Acquire head imaging data of the target individual; the head imaging data includes skull region imaging data and brain tissue imaging data; A three-dimensional skull model is reconstructed based on the skull image data, and the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, and the spatial location data of the target brain region are segmented from the three-dimensional skull model. Based on the cranial imaging data, the acoustic parameter distribution of the skull within the target acoustic window region is estimated, including sound velocity distribution, density distribution, thickness distribution, and attenuation coefficient distribution. Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, the preset position of the ultrasound transducer, and the acoustic parameter distribution, the compensation phase distribution for transcranial ultrasound propagation is calculated; the compensation phase distribution is used to enable the ultrasound waves to form a focused sound field of a predetermined shape in the target brain region after passing through the skull. The compensation phase distribution is converted into structural parameters of the cranial conformal acoustic interface device; the structural parameters include at least one of thickness distribution parameters, microstructure array parameters, or multilayer material distribution parameters. Based on the geometric data of the outer surface of the skull, conformal fitting surface data is generated, and based on the structural parameters and the conformal fitting surface data, a three-dimensional manufacturing model of the skull conformal acoustic interface device is generated; the three-dimensional manufacturing model is used to prepare the skull conformal acoustic interface device.

[0013] Optionally, based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, the preset location of the ultrasound transducer, and the acoustic parameter distribution, a compensated phase distribution for transcranial ultrasound propagation is calculated, specifically including: Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, and the preset location of the ultrasound transducer, multiple ultrasound propagation paths are determined. Based on the acoustic parameter distribution and multiple ultrasonic propagation paths, calculate the phase delay, amplitude attenuation, and incident angle offset for each propagation path; The compensated phase distribution is calculated based on the phase delay, amplitude attenuation, and incident angle offset on multiple propagation paths; the compensated phase distribution ensures that the ultrasound waves on each propagation path have a consistent phase when they reach the target brain region.

[0014] Optionally, when the structural parameter is a thickness parameter, the compensation phase distribution is converted into the structural parameters of the cranial conformal acoustic interface device, specifically including: Obtain the preset material sound velocity and preset operating frequency of the cranial conformal acoustic interface device; Based on the compensated phase distribution, the preset material sound velocity, and the preset operating frequency, calculate the structural thickness value of the cranial conformal acoustic interface device at each position within the target acoustic window area; The thickness distribution parameters are generated based on the structural thickness values ​​at each location; the thickness distribution parameters are used to form a phase delay distribution corresponding to the compensation phase distribution in the cranial conformal acoustic interface device.

[0015] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a cranial conformal acoustic interface device for ultrasound brain-computer interfaces and its design and fabrication method. By setting the conformal fitting surface of the cranial conformal fitting layer as a three-dimensional curved surface matching the outer surface morphology of the target acoustic window region of the individual skull, a fixed gap space is formed between the conformal fitting surface and the outer surface of the skull when the device is worn. The thickness of the coupling medium layer between the device's dorsal side and the ultrasound transducer is limited by the transducer coupling layer, ensuring that the spatial distribution of this gap space and the thickness of the coupling layer on the transducer side remain fixed and repeatable across multiple wears. Based on this, an acoustic compensation functional layer pre-fixes a compensated phase distribution according to the individual skull acoustic parameters and the location of the target brain region. This allows ultrasound waves to sequentially pass through the transducer coupling layer, the acoustic compensation functional layer, the cranial conformal fitting layer, and the coupling layer between the conformal fitting surface and the skull, canceling out the propagation path differences at each lateral position. The ultrasound waves then enter the skull with a compensated wavefront phase. The acoustic channel formed by the aforementioned layers is spatially constrained by the mechanical positioning layer in a fixed external posture, ensuring that the relative spatial relationship between the acoustic channel and the skull remains consistent with each wear. Consequently, the additional phase error introduced by changes in the coupling layer thickness with varying wearing posture is eliminated, and the phase distortion introduced by spatial differences in the skull's thickness, density, and sound velocity is offset by the acoustic compensation layer. The focal point position within the brain and the sound pressure intensity at that focal point remain stable across multiple wears. Furthermore, for a closed-loop ultrasound brain-computer interface, acoustic input variation is controlled within a calibrable range, fluctuations in neural response signals can be clearly attributed to changes in brain state rather than interface errors, and the system can establish a stable input-output mapping relationship, enabling reliable operation of acoustic modulation tasks in long-term, repetitive use scenarios. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the cranial conformal acoustic interface device for ultrasound brain-computer interface provided in Embodiment 1 of this application. Figure 2(a) is a schematic diagram of the assembly relationship of the skull conformal acoustic interface device for skull-induced aberration correction; Figure 2(b) is a schematic diagram of the defocusing of the transcranial ultrasound focusing beam when the cranial conformal acoustic interface device is not installed; Figure 2(c) is a schematic diagram showing that after the cranial conformal acoustic interface device is installed, the transcranial ultrasound focusing beam forms a good focus at the target point in the brain; Figure 3This is a schematic flowchart illustrating the design and fabrication method of the cranial conformal acoustic interface device for ultrasound brain-computer interface provided in Embodiment 2 of this application. Figure 4 The image shows a comparison of the simulated acoustic input effects of the cranial conformal acoustic interface device provided in Embodiment 4 of this application under different conditions of ultrasonic transducer operation. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1: Figure 1 This is a schematic diagram of the cranial conformal acoustic interface device for ultrasound brain-computer interface provided in this application embodiment. The cranial conformal acoustic interface device is worn on the head of the subject during use and is located between the skull and the ultrasound transducer to provide a stable, repeatable and individualized phase-compensated acoustic propagation path for transcranial ultrasound.

[0021] Figure 2(a) schematically illustrates the assembly relationship of the cranial conformal acoustic interface device for cranial induced aberration correction; Figure (b) shows a schematic diagram of the defocusing of the transcranial ultrasound focusing beam when the cranial conformal acoustic interface device is not installed, at which time the ultrasound wave cannot form an effective focus at the target point in the brain after passing through the skull; Figure (c) shows a schematic diagram of the good focus of the transcranial ultrasound focusing beam at the target point in the brain after the cranial conformal acoustic interface device is installed.

[0022] like Figure 1 As shown, the cranial conformal acoustic interface device includes, in sequence from the skull outward (i.e., along the direction of ultrasound wave propagation, from the inner surface of the skull to the outer surface of the skull and continuing outward): brain-computer interface integration layer 1, transducer coupling layer 2, cranial conformal fitting layer 3, acoustic compensation functional layer 4, and mechanical positioning layer 5.

[0023] The brain-computer interface integration layer 1 is located on the innermost side of the craniofacial acoustic interface device, i.e., the side closest to the skull. The transducer coupling layer 2 is located on the side of the brain-computer interface integration layer 1 away from the skull. The craniofacial conformal layer 3 is located on the side of the transducer coupling layer 2 away from the brain-computer interface integration layer 1. The acoustic compensation functional layer 4 is located on the side of the craniofacial conformal layer 3 away from the transducer coupling layer 2. The mechanical positioning layer 5 is connected to at least one of the aforementioned layers and is used for connection with an external fixation device (e.g., a headband, strap, or helmet).

[0024] In this embodiment, the cranial conformal fitting layer 3, the acoustic compensation functional layer 4, and the transducer coupling layer 2 together constitute the acoustic channel for transcranial ultrasound propagation. After the ultrasound waves are emitted by the ultrasound transducer, they are sequentially conducted through the coupling medium layer in the transducer coupling layer 2, the cranial conformal fitting layer 3, and the acoustic compensation functional layer 4 to the skull, and then pass through the skull to enter the target area in the brain.

[0025] 1. Brain-computer interface integration layer: The brain-computer interface integration layer 1 is located on the side closest to the skull, i.e., the innermost side of the skull-conforming acoustic interface device. The brain-computer interface integration layer 1 is used to house the brain-computer interface sensing module. The brain-computer interface sensing module includes, but is not limited to, at least one of the following: electroencephalogram (EEG) electrodes, functional near-infrared probes, inertial measurement units, temperature sensors, pressure sensors, or acoustic coupling state detectors, for collecting information on brain function status or wearing status.

[0026] In this embodiment, the pressure sensor can be disposed between the cranial conformal fitting layer 3 and the brain-computer interface integration layer 1 to detect the contact pressure between the cranial conformal fitting layer 3 and the outer surface of the skull during wear, so as to determine whether the wearing posture meets the preset requirements. The acoustic coupling state detector can be disposed in the cranial conformal fitting layer 3 or the transducer coupling layer 2 to monitor the filling state and coupling effect of the coupling medium layer in real time. The EEG electrodes are dry electrodes or wet electrodes, used to collect the subject's EEG signals. The functional near-infrared probe is used to collect blood oxygen level-dependent signals of the brain region. The inertial measurement unit is used to detect head posture and movement state. The temperature sensor is used to detect the temperature of the wearing area to prevent discomfort or overheating of the device due to prolonged wear. The signals collected by these sensing modules can be used in subsequent closed-loop control algorithms, enabling the cranial conformal acoustic interface device to simultaneously acquire brain function state feedback information while providing stable acoustic input.

[0027] 2. Transducer coupling layer: The transducer coupling layer 2 is disposed on the side of the brain-computer interface integration layer 1 away from the skull. The transducer coupling layer 2 is used to accommodate the coupling medium layer and to form an acoustic coupling connection with the ultrasound transducer through the coupling medium layer. At the same time, the transducer coupling layer 2 is also used to define the thickness of the coupling medium layer, so that the coupling medium layer has a defined and consistent thickness distribution each time it is worn.

[0028] It should be noted that the coupling medium layer is an acoustic conductive medium filled inside the transducer coupling layer 2, and its material includes, but is not limited to, one or more combinations of water, acoustic gel, flexible acoustic membrane, or solid acoustic coupling sheet. The function of the coupling medium layer is to form an acoustic impedance-matched acoustic conduction path between the ultrasonic transducer and the cranial conformal fitting layer 3, so that ultrasonic waves can be efficiently conducted from the ultrasonic transducer to the cranial conformal fitting layer 3 with low interface reflection loss.

[0029] In this embodiment, the transducer coupling layer 2 can limit the thickness of the coupling medium layer through its own rigid structure, or it can control the thickness of the coupling medium layer through a limiting structure disposed inside the transducer coupling layer 2. Compared with flexible water bladders or gel layers, whose thickness distribution depends on wearing pressure and filling state during wear, this embodiment, through the rigid or semi-rigid structure of the transducer coupling layer 2, ensures that the thickness of the coupling medium layer remains consistent throughout the target acoustic window area and does not change with wearing operations, thereby eliminating the additional phase error introduced by the change in coupling layer thickness and its non-repeatability between multiple wears.

[0030] 3. Skull conformal fitting layer: The cranial conformal fitting layer 3 is disposed on the side of the transducer coupling layer 2 away from the brain-computer interface integration layer 1. The cranial conformal fitting layer 3 has a conformal fitting surface facing the outer surface of the skull in relation to the target acoustic window region. The curved shape of the conformal fitting surface matches the outer surface shape of the target acoustic window region of the individual skull, and is used to fit the outer surface of the skull in use.

[0031] In this embodiment, when the cranial conformal acoustic interface device is in operation, the ultrasonic wave passes through the cranial region as it propagates from the ultrasonic transducer to the target brain region. The location and extent of the target acoustic window region may vary for different target brain regions and for different individuals. The conformal fitting surface is designed using reverse engineering based on the three-dimensional morphological data of the outer surface of the skull in the target acoustic window region, ensuring a surface-to-surface fit with the outer surface of the skull in the target acoustic window region during wear, with a uniquely determined fitting posture.

[0032] The conformal fitting surface may be provided with at least one of the following: a limiting edge, a flexible sealing ring, a coupling agent receiving groove, and an exhaust channel. The limiting edge protrudes circumferentially along the conformal fitting surface to limit the gap between the conformal fitting surface and the outer surface of the skull during wear, preventing excessive compression. The coupling agent receiving groove is recessed into the conformal fitting surface to accommodate acoustic coupling agent (e.g., ultrasound coupling gel), ensuring no air gap exists between the conformal fitting surface and the outer surface of the skull, guaranteeing the continuity of acoustic transmission. The exhaust channel penetrates the skull conformal fitting layer 3 and connects the coupling agent receiving groove to the outside, allowing air to escape between the conformal fitting surface and the outer surface of the skull during wear, preventing air bubbles from affecting acoustic transmission.

[0033] Through the individualized design of the conformal fitting surface and the setting of the above-mentioned auxiliary structures, the cranial conformal fitting layer 3 can fit the outer surface of the skull in a unique posture each time it is worn, so that the relative position and posture between the coupling medium layer and the skull remain consistent, thereby providing a geometric basis for achieving the repeatability of the sound field.

[0034] 4. Acoustic compensation functional layer: The acoustic compensation layer 4 is disposed on the side of the skull conformal fitting layer 3 away from the transducer coupling layer 2 (i.e., the outermost layer). The acoustic compensation layer 4 is used to perform phase modulation and wavefront shaping on the ultrasound waves passing through the skull to correct the acoustic distortion introduced by the skull.

[0035] It should be noted that the acoustic distortions introduced by the skull include, but are not limited to: phase errors caused by the difference in sound path between different propagation paths due to uneven skull thickness; phase distortion caused by the difference in sound velocity of different paths due to the uneven spatial distribution of skull density and sound velocity; uneven amplitude attenuation caused by the absorption and scattering of ultrasound waves by the skull; and beam deflection caused by the change in the incident angle due to the geometric curvature of the inner and outer surfaces of the skull.

[0036] In this embodiment, the acoustic compensation layer 4 integrates the compensation function for various acoustic distortions introduced by the skull into its physical structure (e.g., thickness distribution, microstructure array, or multilayer material combination). This ensures that when ultrasound waves pass through the acoustic compensation layer 4, they are endowed with a pre-designed compensation phase distribution. This compensation phase distribution precisely cancels out the distortion phase subsequently introduced by the skull, thereby enabling the ultrasound waves passing through the skull to form a focused sound field of the desired shape in the target brain region. The method for determining the compensation phase distribution will be described in detail in the method embodiments.

[0037] In this application, the acoustic compensation functional layer 4 can be implemented in various specific physical forms, including but not limited to the following three implementation methods: The first implementation method: continuous thickness acoustic lens.

[0038] The acoustic compensation layer 4 is a continuous-thickness acoustic lens. The thickness distribution of this continuous-thickness acoustic lens is determined based on the compensation phase distribution corresponding to the target brain region. Specifically, the thickness of the acoustic compensation layer 4 varies across the target acoustic window region; thicker regions produce a larger phase delay for the sound waves, while thinner regions produce a smaller phase delay, thus forming a continuous thickness distribution in space corresponding to the compensation phase distribution. This thickness distribution is determined according to the following relationship: The thickness of the acoustic compensation layer 4 at any location is directly proportional to the required phase compensation at that location and inversely proportional to the sound velocity of the material of the acoustic compensation layer 4 and the preset operating frequency. Specifically, the thickness distribution is determined as follows: First, the required phase compensation for each propagation path is calculated based on the target brain region location, skull geometry, and acoustic parameter distribution; then, the material for fabricating the acoustic compensation layer 4 is selected, and the sound velocity value of the material is obtained; finally, the thickness value of the acoustic compensation layer 4 at each location is calculated based on the phase compensation, the sound velocity of the material, and the preset operating frequency, so that the ultrasound waves on each propagation path have a consistent phase after passing through the acoustic compensation layer 4 and the skull.

[0039] The second implementation method: discrete metasurface acoustic interface.

[0040] The acoustic compensation functional layer 4 is a discrete metasurface acoustic interface. This discrete metasurface acoustic interface consists of multiple discretely arranged phase compensation units. Each phase compensation unit has an independent phase delay, which is determined by the local structural parameters corresponding to that unit. These local structural parameters include at least one of unit height, porosity, material acoustic impedance, or local channel length.

[0041] Specifically, the phase compensation unit can be a micropillar array of different heights, with taller units causing greater phase delays to the sound waves; it can also be a porous structure unit with different porosities, as different porosities lead to different equivalent sound velocities, thus producing different phase delays; or it can be a unit containing internal channels of different lengths, as different channel lengths result in different path lengths for the sound waves to propagate within them, thereby achieving different phase delays. The various phase compensation units are arranged spatially according to the encoded result of the compensated phase distribution, so that the ultrasonic sound waves obtain a preset phase distribution after passing through the discrete metasurface acoustic interface.

[0042] The third implementation method: multi-layer composite acoustic interface.

[0043] The acoustic compensation functional layer 4 is a multi-layer composite acoustic interface. The multi-layer composite acoustic interface includes an inner layer adjacent to the cranial conformal fitting layer 3, an outer layer away from the cranial conformal fitting layer 3, and an intermediate layer located between the inner and outer layers. The inner layer, the outer layer, and the intermediate layer have different acoustic impedances.

[0044] Specifically, the inner layer is disposed adjacent to the cranial conformal fitting layer 3 and is used to adjust the focusing position and focusing shape of the sound beam. The outer layer is disposed on the outermost side of the multi-layer composite acoustic interface (i.e., the side away from the cranial conformal fitting layer 3) and is used to compensate for the phase distribution. The middle layer is located between the inner layer and the outer layer and is used to reduce the acoustic impedance difference between the cranial conformal fitting layer 3 and the transducer coupling layer 2, thereby improving the transmission efficiency of ultrasonic waves between layers and reducing interface reflection loss.

[0045] In one specific embodiment, the acoustic impedance of the inner layer is set to be close to that of the skull to achieve low-reflection transmission of sound waves from the skull conformal layer 3 to the inner layer; the outer layer is a thickness-gradient acoustic lens layer used to achieve phase compensation; the acoustic impedance of the intermediate layer is between that of the inner and outer layers, forming a gradual transition in acoustic impedance, further reducing sound wave reflection at the interlayer interface. The materials of the inner, intermediate, and outer layers can be the same (by adjusting the density or filler to change the acoustic impedance) or different (using acoustic materials with different acoustic impedances).

[0046] 5. Mechanical positioning layer: The mechanical positioning layer 5 is connected to at least one of the brain-computer interface integration layer 1, the transducer coupling layer 2, the craniofacial conformal layer 3, or the acoustic compensation functional layer 4. The mechanical positioning layer 5 is used to cooperate with an external fixation device to define the relative position between the craniofacial conformal acoustic interface device and the skull.

[0047] In this embodiment, the mechanical positioning layer 5 can be implemented in various physical forms: In one embodiment, the mechanical positioning layer 5 is an auxiliary structure disposed on the outside of the craniosynthetic acoustic interface device, such as a buckle for connecting straps, a slot for inserting a bracket, or a threaded interface for connecting a helmet. These connecting structures allow for detachable connection to external fixation devices (e.g., headbands, straps, or helmets), constraining the craniosynthetic acoustic interface device to a preset position and preset posture on the skull.

[0048] In another embodiment, the mechanical positioning layer 5 is a positioning bracket independent of the main body of the craniocontouring acoustic interface device. One end of the positioning bracket is connected to the craniocontouring acoustic interface device, and the other end is connected to an external fixation device. Its rigid structure defines the relative positional relationship between each layer of the craniocontouring acoustic interface device and the skull.

[0049] In another embodiment, the mechanical positioning layer 5 includes positioning marks or positioning sensors disposed on the craniosynthetic acoustic interface device, which are used in conjunction with an external navigation and positioning system to guide the operator to place the craniosynthetic acoustic interface device in the same position and posture as the last time it was worn, each time it is worn.

[0050] With the aforementioned arrangement of the mechanical positioning layer 5, the overall position and posture of the cranial conformal acoustic interface device are precisely defined each time it is worn, and the relative positions between each functional layer and the skull remain consistent across multiple wears, providing structural assurance for the repeatability of the sound field.

[0051] 6. How the acoustic channel works: The transducer coupling layer 2, the cranial conformal fitting layer 3, and the acoustic compensation functional layer 4 together constitute the acoustic channel for transcranial ultrasound propagation. This acoustic channel provides an individualized phase-compensated ultrasound transmission path between the ultrasound transducer and the intracranial target area. During operation, ultrasound waves emitted by the transducer pass through the transducer coupling layer 2, the cranial conformal fitting layer 3, and the acoustic compensation functional layer 4 into the skull, ultimately forming a predetermined focused sound field in the intracranial target area. This structure, through a combination of geometric conformal fitting, stable coupling thickness, individualized phase compensation, and mechanical repetitive positioning, improves the stability and repeatability of transcranial ultrasound input.

[0052] Specifically, when the ultrasonic transducer emits ultrasonic waves, the sound waves first enter the coupling medium layer in the coupling layer 2 of the transducer, where they are homogenized to obtain a consistent wavefront phase. Then, the sound waves pass sequentially through the cranial conformal layer 3 and the acoustic compensation functional layer 4, where a pre-compensated phase is applied. Subsequently, the sound waves enter the skull, and the distortion phase introduced by the skull when passing through it exactly cancels out the pre-compensated phase. Finally, the sound waves form a focused sound field of a predetermined shape (e.g., monofocal, multifocal, deflected focus, or structured wavefront) in the target brain region (i.e., the preset intrabrain target region).

[0053] In the above process, by setting the conformal fitting surface of the cranial conformal fitting layer 3 as a three-dimensional curved surface matching the outer surface morphology of the target acoustic window region of the individual skull, a fixed gap space is formed between the conformal fitting surface and the outer surface of the skull when the device is worn. The thickness of the coupling medium layer between the dorsal side of the device and the ultrasound transducer is limited by the transducer coupling layer 2, so that the spatial distribution of this gap space and the thickness of the coupling layer on the transducer side remain fixed and repeatable between multiple wears. On this basis, the acoustic compensation functional layer 4 pre-fixes the compensation phase distribution according to the individual skull acoustic parameters and the location of the target brain region, so that after the ultrasound waves pass through the transducer coupling layer, the acoustic compensation functional layer, the cranial conformal fitting layer, and the coupling layer between the conformal fitting surface and the skull in sequence, the propagation path difference at each lateral position is canceled out, and the ultrasound waves enter the skull with a compensated wavefront phase. The acoustic channel formed by the above layers is in a fixed external posture constrained by the mechanical positioning layer 5, so that the relative spatial relationship between the acoustic channel and the skull remains consistent with each wear. As a result, the additional phase error introduced by the change in wearing posture due to the thickness of the coupling layer is eliminated, and the phase distortion introduced by the difference in the thickness, density and sound velocity of the skull itself is offset by the acoustic compensation functional layer. The focal position in the brain and the sound pressure intensity at the focal point remain stable between multiple wears. On this basis, for the closed-loop ultrasound brain-computer interface, the variation of the acoustic input end is controlled within the calibrable range, the fluctuation of the neural response signal can be clearly attributed to the change in brain state rather than the interface error, the system can establish a stable input-output mapping relationship, and the acoustic modulation task in long-term repetitive use scenarios can be reliably operated.

[0054] Example 2: This embodiment provides a method for designing and fabricating a cranial conformal acoustic interface device for ultrasound brain-computer interfaces, the method being executed by a computer device. Figure 3 This is a schematic flowchart illustrating the design and fabrication method provided in the embodiments of this application. Figure 3 As shown, the method includes the following steps S1 to S6.

[0055] Step S1: Obtain head image data of the target individual.

[0056] Acquire head imaging data of the target individual. The head imaging data includes imaging data of the skull region and imaging data of brain tissue.

[0057] Step S2: Reconstruct the 3D head model and extract geometric data.

[0058] A three-dimensional skull model is reconstructed based on the skull image data, and the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, and the spatial location data of the target brain region are segmented from the three-dimensional skull model.

[0059] In this step, firstly, the skull tissue is segmented from the head imaging data to obtain three-dimensional voxel data of the skull. Then, a three-dimensional reconstruction algorithm is used to convert the voxel data into a surface mesh model, obtaining a three-dimensional geometric model of the outer and inner surfaces of the skull. Subsequently, based on the spatial location of the target brain region (e.g., motor cortex, prefrontal cortex, cingulate gyrus, nucleus accumbens, thalamus, basal ganglia, hypothalamus, or brainstem-related nuclei), the target acoustic window region for the ultrasound brain-computer interface is determined in the three-dimensional head model. The determination of the target acoustic window region is based on, but is not limited to, the spatial location of the target brain region, skull thickness, skull acoustic transmittance, skull surface curvature, and scalp soft tissue conditions. After determining the target acoustic window region, the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, and the spatial location data of the target brain region are segmented from the three-dimensional head model.

[0060] Step S3: Estimate the distribution of acoustic parameters of the skull.

[0061] Based on the cranial imaging data, the acoustic parameter distribution of the skull within the target acoustic window region is estimated. The acoustic parameter distribution includes sound velocity distribution, density distribution, thickness distribution, and attenuation coefficient distribution.

[0062] In this step, the acoustic parameter distribution of the skull within the target acoustic window region is estimated based on the image grayscale values ​​of the skull image data. The specific method is as follows: First, the skull density distribution is calculated based on the image grayscale values ​​of the skull image data. The skull density and the image grayscale values ​​satisfy a preset linear mapping relationship.

[0063] Then, the sound velocity distribution is calculated based on the skull density distribution. The sound velocity and skull density satisfy a preset mapping relationship, including but not limited to linear mapping, exponential mapping, or lookup table mapping based on empirical data. Generally, the higher the density of the skull region, the higher the sound velocity.

[0064] Finally, the attenuation coefficient distribution is calculated based on the skull density distribution and the preset ultrasound operating frequency. The attenuation coefficient satisfies a preset exponential mapping relationship with the skull density and the ultrasound operating frequency. The attenuation coefficient is used to subsequently calculate the amplitude attenuation along each propagation path.

[0065] Furthermore, the thickness distribution of the skull can be directly calculated from the geometric data of the outer surface and the inner surface of the skull. That is, at the same lateral position, the normal distance between the outer surface and the inner surface of the skull is the thickness of the skull at that point.

[0066] Step S4: Calculate the compensation phase distribution.

[0067] Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, the preset location of the ultrasound transducer, and the acoustic parameter distribution, a compensated phase distribution for transcranial ultrasound propagation is calculated. This compensated phase distribution is used to ensure that the ultrasound waves, after passing through the skull, form a focused sound field of a predetermined shape in the target brain region.

[0068] In this step, the specific method for calculating the compensated phase distribution of transcranial ultrasound propagation is as follows: First, based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, and the preset location of the ultrasound transducer, multiple ultrasound propagation paths are determined.

[0069] Then, based on the acoustic parameter distribution and multiple ultrasound propagation paths, the phase delay, amplitude attenuation, and incident angle offset are calculated for each propagation path. For each propagation path, the cumulative phase delay of the sound wave along the path is calculated based on the sound velocity and thickness distribution of the skull region traversed by the path; the cumulative amplitude attenuation of the sound wave along the path is calculated based on the attenuation coefficient distribution of the skull region traversed by the path; and the incident angle offset is calculated based on the incident and exit angles at the outer and inner surfaces of the skull.

[0070] Finally, a compensated phase distribution is calculated based on the phase delay, amplitude attenuation, and incident angle offset along multiple propagation paths. This compensated phase distribution ensures that the ultrasound waves along each propagation path have a consistent phase when they reach the target brain region.

[0071] Step S5: Convert the compensation phase distribution into structural parameters.

[0072] The compensated phase distribution is converted into structural parameters of the cranial conformal acoustic interface device. These structural parameters include at least one of thickness distribution parameters, microstructure array parameters, or multilayer material distribution parameters.

[0073] In this step, taking thickness as an example, the specific method for converting the compensation phase distribution into the structural parameters of the cranial conformal acoustic interface device is as follows: First, the preset material sound velocity and preset operating frequency of the cranial conformal acoustic interface device are obtained. The preset material sound velocity is the sound velocity value of the material selected in the acoustic compensation functional layer 4, and the preset operating frequency is the center operating frequency of the ultrasonic transducer.

[0074] Then, based on the compensated phase distribution, the preset material sound velocity, and the preset operating frequency, the structural thickness value of the cranial conformal acoustic interface device at each location within the target acoustic window area is calculated. The structural thickness value and the compensated phase distribution satisfy a preset phase-thickness conversion relationship. Finally, the thickness distribution parameters are generated based on the structural thickness values ​​at each location. These thickness distribution parameters are used to form a phase delay distribution in the cranial conformal acoustic interface device that corresponds to the compensated phase distribution; that is, different thicknesses are formed at each location of the acoustic compensation functional layer 4, and the spatial variation in thickness corresponds to the spatial variation in phase.

[0075] When the structural parameters are microstructure array parameters, the compensation phase distribution is discretized into multiple phase levels, each phase level corresponding to a microstructure unit (e.g., a column of a specific height, a porous block with a specific porosity, or a channel unit with a specific channel length). These microstructure units are arranged in space according to the phase levels to form a microstructure array corresponding to the compensation phase distribution.

[0076] When the structural parameters are multi-layer material distribution parameters, the compensation phase distribution is decomposed into the phase contribution required by multiple sub-layers. Each layer uses materials with different sound velocities and acoustic impedances. The preset total phase compensation amount is achieved by combining the thickness and combination order of the materials in each layer.

[0077] Step S6: Generate a 3D manufacturing model.

[0078] Based on the geometric data of the outer surface of the skull, conformal fitting surface data is generated, and based on the structural parameters and the conformal fitting surface data, a three-dimensional manufacturing model of the skull conformal acoustic interface device is generated. The three-dimensional manufacturing model is used to fabricate the skull conformal acoustic interface device.

[0079] In this step, the conformal fitting surface data (i.e., surface data matching the external surface morphology of the individual skull) is first superimposed with the structural parameters (e.g., thickness distribution parameters) to form a solid geometric model of the acoustic compensation functional layer 4 and the skull conformal fitting layer 3. Then, based on the solid geometric model, the accommodating space of the transducer coupling layer 2, the accommodating structure of the brain-computer interface integration layer 1, and the connection structure of the mechanical positioning layer 5 are added respectively to form a complete three-dimensional manufacturing model of the skull conformal acoustic interface device.

[0080] The three-dimensional manufacturing model is output in a three-dimensional computer-aided design file format (e.g., standard triangulation language format or initial graphics exchange specification format) for additive manufacturing (e.g., 3D printing, photopolymerization printing) or subtractive manufacturing (e.g., computer numerical control machining, molding) to prepare the cranial conformal acoustic interface device.

[0081] Once prepared, the cranial conformal acoustic interface device becomes an independent physical entity, with an individualized cranial conformal fitting surface and an individualized phase compensation distribution solidified inside, which can be directly used for subsequent ultrasound brain-computer interface experiments or clinical applications.

[0082] Example 3: Based on Embodiment 1 and Embodiment 2, this embodiment provides an integrated assembly and closed-loop usage method for a cranial conformal acoustic interface device.

[0083] In one specific implementation, step S7 is followed by: First, the prepared cranial conformal acoustic interface device is integrated and assembled with the ultrasonic transducer, wearable fixation device, and neural signal acquisition module to form a wearable ultrasonic brain-computer interface system. Specifically, the ultrasonic transducer is inserted into or installed in the transducer coupling layer 2, so that the emitting surface of the ultrasonic transducer is in contact with the coupling medium layer; the cranial conformal acoustic interface device is connected to the wearable fixation device (e.g., headband, strap, or helmet) through the buckle, slot, or threaded interface on the mechanical positioning layer 5; the brain-computer interface sensing module (e.g., EEG electrodes, functional near-infrared probe, inertial measurement unit, etc.) in the brain-computer interface integration layer 1 is electrically connected to the neural signal acquisition module.

[0084] Then, in an individualized simulation environment or an ex vivo skull model, the assembled wearable ultrasound brain-computer interface system is calibrated to obtain the intracranial focal point location and sound pressure dose distribution corresponding to the cranioconformal acoustic interface device. The sound field calibration can employ hydrophone scanning, sound field simulation verification, or ex vivo experimental measurement methods to confirm that the cranioconformal acoustic interface device can form the expected focused sound field in the target brain region under actual use conditions.

[0085] Finally, in actual use, the wearing status of the craniofacial acoustic interface device is monitored by the pressure sensor or acoustic coupling status detection module in the brain-computer interface integration layer 1, and the output parameters of the ultrasonic transducer are adjusted according to the wearing status and the neural response signals acquired by the neural signal acquisition module. The output parameters include, but are not limited to: ultrasonic frequency, pulse repetition frequency, sound pressure, duty cycle, stimulation duration, or target mode.

[0086] Through the aforementioned closed-loop control, the acoustic input stability of the cranial conformal acoustic interface device enables changes in neural response signals to reliably reflect the true changes in brain state, rather than acoustic interface errors, thus providing a reliable hardware foundation for the closed-loop ultrasound brain-computer interface system.

[0087] Example 4: This embodiment verifies the acoustic performance of the cranial conformal acoustic interface device through simulation and experimentation.

[0088] like Figure 4 As shown, Figure 4Figures (a) to (f) show a comparison of the simulated acoustic input effects of the cranial conformal acoustic interface device under different conditions under the action of the ultrasonic transducer.

[0089] Specifically, Figure 4 Figure (a) shows the comparison between the simulated pressure field and the experimentally measured pressure field in the xz and xy planes when there is no skull interference. Under these conditions, the ultrasonic wave propagates in a homogeneous medium, the wavefront is not distorted, the focal position is accurate, and the sound pressure intensity at the focal point reaches the theoretical maximum value. The simulation results are in high agreement with the experimental results.

[0090] Figure 4 Figure (b) shows the corresponding quantitative comparison results without skull interference, further verifying the consistency between the simulation model and experimental measurements.

[0091] Figure 4 Figures (c) and (d) show the simulated and experimentally measured pressure fields in the xz and xy planes, respectively, when a skull is present but no conformal acoustic interface device is installed. Under these conditions, the ultrasonic waves undergo significant wavefront distortion after passing through the skull, the focal point deviates significantly from the preset target point, the sound pressure intensity at the focal point decreases sharply, and the sound field distribution exhibits an irregular shape.

[0092] Figure 4 Figures (e) and (f) show the simulated and experimentally measured pressure fields in the xz and xy planes when both a skull and a craniofacial conformal acoustic interface device are present. Under these conditions, the acoustic compensation layer 4 of the craniofacial conformal acoustic interface device effectively corrects the acoustic distortion introduced by the skull. The ultrasound waves regain good wavefront consistency after passing through the skull, the focal point is accurately located in the target brain region, and the sound pressure intensity at the focal point recovers to a level close to that under conditions without a skull. The simulation results are in high agreement with the experimental results.

[0093] The above comparative experiments strongly demonstrate that the cranial conformal acoustic interface device can effectively correct acoustic distortions introduced by the skull and achieve stable transcranial ultrasound focusing.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces, characterized in that, The device includes: A brain-computer interface integration layer, wherein the brain-computer interface integration layer is disposed on the side closest to the skull, and is used to accommodate the brain-computer interface sensing module; A transducer coupling layer is disposed on the side of the brain-computer interface integration layer away from the skull. It is used to accommodate the coupling medium layer and form an acoustic coupling connection with the ultrasound transducer through the coupling medium layer. The transducer coupling layer is used to limit the thickness of the coupling medium layer. A cranial conformal fitting layer is disposed on the side of the transducer coupling layer away from the brain-computer interface integration layer. The cranial conformal fitting layer has a conformal fitting surface facing the outer surface of the skull of the target acoustic window area. The curved shape of the conformal fitting surface matches the outer surface shape of the target acoustic window area of ​​the individual skull and is used to fit the outer surface of the skull in the use state. An acoustic compensation functional layer is disposed on the side of the cranial conformal fitting layer away from the transducer coupling layer, and is used to perform phase modulation and wavefront shaping on the ultrasound waves passing through the skull to correct the acoustic distortion introduced by the skull. A mechanical positioning layer, which is connected to at least one of the brain-computer interface integration layer, the transducer coupling layer, the cranial conformal fitting layer, or the acoustic compensation functional layer, is used to cooperate with an external fixation device to define the relative position between the cranial conformal acoustic interface device and the skull. The cranial conformal layer, the acoustic compensation layer, and the transducer coupling layer together constitute the acoustic channel for transcranial ultrasound propagation. The acoustic channel is used to provide an ultrasound transmission path with individualized phase compensation between the ultrasound transducer and the intracranial target area.

2. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The conformal fitting surface is provided with at least one of the following: a limiting edge, a flexible sealing ring, a coupling agent receiving groove, and an exhaust channel; the limiting edge is provided to protrude circumferentially along the conformal fitting surface, the coupling agent receiving groove is recessed in the conformal fitting surface, and the exhaust channel penetrates the cranial conformal fitting layer and connects the coupling agent receiving groove to the outside.

3. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The acoustic compensation functional layer is a continuous thickness acoustic lens, and the thickness distribution of the continuous thickness acoustic lens is determined according to the compensation phase distribution corresponding to the target brain region; the compensation phase distribution is calculated based on the geometric parameters, sound velocity distribution, density distribution and attenuation coefficient distribution of the individual skull.

4. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The acoustic compensation functional layer is a discrete metasurface acoustic interface, which is composed of multiple discretely arranged phase compensation units. Each phase compensation unit has an independent phase delay, which is determined by the local structural parameters corresponding to the phase compensation unit. The local structural parameters include at least one of the following: unit height, porosity, material acoustic impedance, or local channel length.

5. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The acoustic compensation functional layer is a multi-layer composite acoustic interface, which includes an inner layer adjacent to the cranial conformal fitting layer, an outer layer away from the cranial conformal fitting layer, and an intermediate layer located between the inner layer and the outer layer. The inner layer, the outer layer, and the intermediate layer have different acoustic impedances. The inner layer is used to adjust the focusing position and focusing shape of the sound beam, the outer layer is used to compensate for the phase distribution, and the intermediate layer is used to reduce the acoustic impedance difference between the cranial conformal fitting layer and the transducer coupling layer.

6. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The brain-computer interface sensing module included in the brain-computer interface integrated layer includes at least one of the following: electroencephalogram (EEG) electrodes, a functional near-infrared probe, an inertial measurement unit, a temperature sensor, a pressure sensor, and an acoustic coupling state detector; the pressure sensor is disposed between the cranial conformal fitting layer and the brain-computer interface integrated layer, and the acoustic coupling state detector is disposed in the cranial conformal fitting layer or the transducer coupling layer.

7. The craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 1, characterized in that, The mechanical positioning layer is provided with positioning marks, which are used to constrain the wearing posture; the mechanical positioning layer is also provided with buckles, slots or threaded interfaces for detachable connection with headbands, straps or helmets.

8. A method for designing and fabricating a craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces, characterized in that, The method includes: Acquire head imaging data of the target individual; the head imaging data includes skull region imaging data and brain tissue imaging data; A three-dimensional skull model is reconstructed based on the skull image data, and the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, and the spatial location data of the target brain region are segmented from the three-dimensional skull model. Based on the cranial imaging data, the acoustic parameter distribution of the skull within the target acoustic window region is estimated, including sound velocity distribution, density distribution, thickness distribution, and attenuation coefficient distribution. Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, the preset position of the ultrasound transducer, and the acoustic parameter distribution, the compensation phase distribution for transcranial ultrasound propagation is calculated; the compensation phase distribution is used to enable the ultrasound waves to form a focused sound field of a predetermined shape in the target brain region after passing through the skull. The compensation phase distribution is converted into structural parameters of the cranial conformal acoustic interface device; the structural parameters include at least one of thickness distribution parameters, microstructure array parameters, or multilayer material distribution parameters. Based on the geometric data of the outer surface of the skull, conformal fitting surface data is generated, and based on the structural parameters and the conformal fitting surface data, a three-dimensional manufacturing model of the skull conformal acoustic interface device is generated; the three-dimensional manufacturing model is used to prepare the skull conformal acoustic interface device.

9. The design and fabrication method of the craniofacial conformal acoustic interface device for ultrasound brain-computer interfaces according to claim 8, characterized in that, Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, the preset ultrasound transducer position, and the acoustic parameter distribution, the compensated phase distribution for transcranial ultrasound propagation is calculated, specifically including: Based on the geometric data of the outer surface of the skull, the geometric data of the inner surface of the skull, the spatial location data of the target brain region, and the preset location of the ultrasound transducer, multiple ultrasound propagation paths are determined. Based on the acoustic parameter distribution and multiple ultrasonic propagation paths, calculate the phase delay, amplitude attenuation, and incident angle offset for each propagation path; The compensated phase distribution is calculated based on the phase delay, amplitude attenuation, and incident angle offset on multiple propagation paths; the compensated phase distribution ensures that the ultrasound waves on each propagation path have a consistent phase when they reach the target brain region.

10. The design and fabrication method of the cranial conformal acoustic interface device for ultrasound brain-computer interface according to claim 9, characterized in that, When the structural parameter is a thickness parameter, the compensation phase distribution is converted into the structural parameters of the cranial conformal acoustic interface device, specifically including: Obtain the preset material sound velocity and preset operating frequency of the cranial conformal acoustic interface device; Based on the compensated phase distribution, the preset material sound velocity, and the preset operating frequency, calculate the structural thickness value of the cranial conformal acoustic interface device at each position within the target acoustic window area; The thickness distribution parameters are generated based on the structural thickness values ​​at each location; the thickness distribution parameters are used to form a phase delay distribution corresponding to the compensation phase distribution in the cranial conformal acoustic interface device.

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