Compound fresnel acoustic lens, design method, and related devices

Abstract

The application relates to the technical field of Fresnel acoustic lens application, and provides a composite Fresnel acoustic lens, a design method and related equipment. The composite Fresnel acoustic lens comprises at least two groups of coaxial multi-focus Fresnel zone plates, the at least two groups of coaxial multi-focus Fresnel zone plates are stacked after being radially translated by a set distance, at least three non-coaxial ultrasonic focal points are generated in a three-dimensional space, and the composite Fresnel acoustic lens can be used for transcranial ultrasonic stimulation or treatment; wherein the coaxial multi-focus Fresnel zone plate comprises a multi-layer lens structure which is nested together, and the multi-layer lens structure comprises a frame area and an ultrasonic transmission medium area. The method of stacking multiple groups of coaxial multi-focus Fresnel zone plates is used to simultaneously focus multiple different-axis and different-depth ultrasonic target points, and the limitation of a limited coverage range of a traditional single-focus or coaxial double-focus is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of Fresnel acoustic lens application technology, and in particular to a composite Fresnel acoustic lens, a design method and related equipment. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Transcranial focused ultrasound (TcFUS) is a technology that uses ultrasound focusing in the skull to complete treatment, and is widely used in the research of diseases such as Alzheimer's disease, epilepsy, Parkinson's syndrome, etc. Due to the special structure of the skull, the ultrasound is prone to acoustic attenuation and phase distortion during penetration, which limits the treatment effect. Various methods have been proposed in the prior art to compensate for the phase error and energy loss of the ultrasound, such as phased array method, time reversal method and acoustic lens, etc. However, these methods are usually complex to calculate, or have problems such as insufficient mechanical stability and low focusing efficiency.

[0004] In addition, most brain disease treatments and brain regulation often require the synergistic action of multiple brain regions, i.e. ultrasound stimulation needs to be applied to multiple brain regions simultaneously. In the design of planar acoustic lenses, the existing Fresnel acoustic lens structure can usually only produce one focal point, making it difficult to achieve flexible coverage of multiple target points in space. SUMMARY

[0005] To solve the technical problems in the background art, the present application provides a composite Fresnel acoustic lens, a design method and related equipment. The present application realizes simultaneous focusing of multiple non-coaxial ultrasound focal points of different axes and depths by superimposing multiple groups of coaxial multi-focus Fresnel zone plates, overcomes the limitation of limited coverage range of traditional single-focus lenses, and allows customized design according to the ultrasound frequency and the location of the brain region involved in the treatment, thereby improving the applicability, individualization and effect of transcranial ultrasound treatment.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] The first aspect of the present application provides a composite Fresnel acoustic lens.

[0008] A composite Fresnel acoustic lens, comprising: at least two groups of coaxial multi-focus Fresnel zone plates, which are superimposed by translating the coaxial multi-focus Fresnel zone plates radially, to generate at least three non-coaxial ultrasound focal points in three-dimensional space, which can be used for transcranial ultrasound stimulation or treatment of the brain;

[0009] The coaxial multi-focus Fresnel zone plate comprises a plurality of nested lens structures, and the plurality of lens structures comprise a frame area and an ultrasonic transmission medium area.

[0010] Further, the superimposed composite Fresnel acoustic lens is generated by stacking at least two groups of coaxial multi-focal Fresnel zone plates in a superimposed manner, and the overlapping area is reserved during stacking.

[0011] Further, the superimposed composite Fresnel acoustic lens comprises a first border area and a first ultrasonic transmission medium area, and the first border area is stacked by at least two groups of the same coaxial multi-focal Fresnel zone plates in a radial translation manner.

[0012] Further, the alternating segmented composite Fresnel acoustic lens is generated by stacking at least two groups of coaxial multi-focal Fresnel zone plates in a manner of removing the overlapping area and setting a rectangular support structure at some positions.

[0013] Further, the alternating segmented composite Fresnel acoustic lens comprises a second border area, a second ultrasonic transmission medium area and a rectangular support structure.

[0014] The second aspect of the present application provides a design method of a composite Fresnel acoustic lens.

[0015] The design method of the composite Fresnel acoustic lens of the first aspect comprises:

[0016] Selecting a coaxial focal point in the preset focal point to obtain a plurality of coaxial multi-focal point groups to construct a coaxial multi-focal Fresnel zone plate; the process of constructing the coaxial multi-focal Fresnel zone plate comprises:

[0017] Arranging the focal points in each coaxial multi-focal point group in order of increasing focal length: each focal point corresponds to a layer of lens structure, and the lens structure with a small focal length is located in the inner layer, and the lens structure with a large focal length is located in the outer layer;

[0018] Based on the ultrasonic wavelength and the preset focal length of each focal point, the radius of each Fresnel waveband corresponding to each focal point is calculated by using the Fresnel half-waveband theory, and the radius of the Fresnel waveband comprises the radius corresponding to the odd waveband number and the radius corresponding to the even waveband number; the radius corresponding to the odd waveband number is set as the inner diameter of the corresponding lens structure border area, and the radius corresponding to the even waveband number is set as the outer diameter of the corresponding lens structure border area;

[0019] The lens structure corresponding to each focal point is nested, and the number of Fresnel wavebands of each layer of lens structure is selected under the principle of ensuring that the outer diameter of the border area corresponding to the maximum waveband number of the inner layer lens structure is smaller than the inner diameter of the border area corresponding to the minimum waveband number of the outer layer lens structure, so as to construct the coaxial multi-focal Fresnel zone plate capable of generating coaxial multi-focal points.

[0020] At least two groups of coaxial multi-focal Fresnel zone plates capable of generating coaxial multi-focal points are radially translated by a set distance and then superimposed to construct a composite Fresnel acoustic lens; the superimposed processing methods include: retaining the overlapping area during superimposition to generate a superimposed composite Fresnel acoustic lens; and removing the overlapping area after superimposition and setting a rectangular support structure at certain positions to generate an alternating segmented composite Fresnel acoustic lens.

[0021] The third aspect of the present application provides a cranial window replacement system.

[0022] The cranial window replacement system replaces part of the skull with the composite Fresnel acoustic lens of the first aspect, and plane ultrasound forms at least three focal spots in the skull through the composite Fresnel acoustic lens.

[0023] Further, the composite Fresnel acoustic lens is fixed on the edge of the cranial window by a biocompatible adhesive, replaces the missing skull, one side of the composite Fresnel acoustic lens is close to the brain area, and the other side is connected to the plane ultrasonic transducer.

[0024] Further, the materials of the first frame area, the second frame area, the first ultrasonic transmission medium area, the second ultrasonic transmission medium area and the rectangular support structure in the composite Fresnel acoustic lens are biocompatible materials.

[0025] The fourth aspect of the present application provides a plane ultrasonic transducer accessory.

[0026] The plane ultrasonic transducer accessory comprises the composite Fresnel acoustic lens of the first aspect, and the composite Fresnel acoustic lens is symmetrically provided with a secondary support clamp module and a main support clamp base on both sides of the composite Fresnel acoustic lens, the main support clamp base is internally provided with a rectangular clamping cavity, the contour of the rectangular clamping cavity matches the outer dimensions of the secondary support clamp module, the secondary support clamp module is rigidly locked by being axially embedded into the rectangular clamping cavity, the main support clamp base and the transducer-base connecting column adopt an integrated connection structure, the transducer-base connecting column is sleeved around the outer periphery of the plane ultrasonic transducer and is in interference fit with the plane ultrasonic transducer, and the composite Fresnel acoustic lens is nested on the transducer-base connecting column.

[0027] Further, the inner diameter tolerance of the transducer-base connecting column and the outer diameter tolerance of the plane ultrasonic transducer meet the interference fit requirements.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] In view of the technical problem that the existing Fresnel acoustic lens structure can usually only generate one focal point or two coaxial focal points, the application provides a composite Fresnel acoustic lens, which realizes the simultaneous focusing of multiple different axial and different depth ultrasonic target points in a three-dimensional space by superimposing multiple groups of coaxial multi-focal Fresnel zone plates, and overcomes the limitation of the limited coverage range of the traditional single focal lens.

[0030] In view of the technical problem that due to the special structure of the skull, ultrasonic waves are prone to acoustic attenuation and phase distortion during penetration, resulting in limited treatment effect, the application uses a composite Fresnel acoustic lens skull window to replace part of the skull, replacing the irregular material and large acoustic impedance skull with a regular skull window with small acoustic impedance, reducing the distortion and attenuation of the skull to the ultrasonic signal.

[0031] In view of the technical problem that the conventional phased array method and time reversal method have large calculation amount and high price, the application uses a composite Fresnel acoustic lens to replace the skull or as a planar ultrasonic transducer accessory to realize comprehensive, efficient and personalized ultrasonic brain function regulation and treatment, and utilizes the regular geometric shape of the composite Fresnel acoustic lens skull window structure to reduce the calculation complexity and hardware cost. BRIEF DESCRIPTION OF DRAWINGS

[0032] The drawings accompanying the specification of the application serve to provide a further understanding of the application, and the schematic embodiments of the application and the description thereof serve to explain the application and do not constitute an improper limitation on the application.

[0033] Figure 1 A structure schematic diagram of a coaxial double-focal Fresnel zone plate shown in the application;

[0034] Figure 2 A structure schematic diagram of a superimposed composite Fresnel acoustic lens shown in the application;

[0035] Figure 3 A structure schematic diagram of an alternating segmented composite Fresnel acoustic lens shown in the application;

[0036] Figure 4 A simulation sound field diagram of a superimposed composite Fresnel acoustic lens shown in the application;

[0037] Figure 5A simulation sound field diagram of the alternative segmentation type composite Fresnel acoustic lens shown in the present application;

[0038] Figure 6 A schematic diagram of the composite Fresnel acoustic lens shown in the present application as a skull window to replace the skull;

[0039] Figure 7 A schematic diagram of the composite Fresnel acoustic lens shown in the present application as a flat ultrasonic transducer accessory;

[0040] Legend: 1, inner lens structure; 2, outer lens structure; 3, boundary line of the inner lens and the outer lens; 4, frame area; 5, ultrasonic transmission medium area; 6, first frame area; 7, first ultrasonic transmission medium area; 8, second frame area; 9, second ultrasonic transmission medium area; 10, rectangular support structure; 11, flat ultrasonic transducer; 12, ultrasonic coupling agent; 13, composite Fresnel acoustic lens; 14, focal spot generated after the flat ultrasonic transducer passes through the multi-focal Fresnel acoustic lens; 15, cerebral cortex area; 16, deep brain nucleus area; 17, superimposed composite Fresnel acoustic lens; 18, alternative segmentation type composite Fresnel acoustic lens; 19, auxiliary support clamp module; 20, main support clamp base; 21, transducer-base connecting column. DETAILED DESCRIPTION

[0041] The present application is further described below in conjunction with the accompanying drawings and examples.

[0042] It should be noted that the following detailed description is merely illustrative in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0043] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments consistent with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0044] In the present embodiments, "first", "second", and the like can refer to different or the same objects. Unless the context clearly indicates otherwise, the definition of one term is consistent throughout the description.

[0045] Example One

[0046] This embodiment provides a composite Fresnel acoustic lens, comprising: at least two sets of coaxial multifocal Fresnel plates, which are superimposed after radial translation of the coaxial multifocal Fresnel plates to generate at least three non-coaxial ultrasound focal points in three-dimensional space, which can be used for transcranial ultrasound stimulation or treatment of the brain; wherein, the coaxial multifocal Fresnel plates include nested multilayer lens structures, the multilayer lens structures including a frame area and an ultrasound transmission medium area.

[0047] The requirement of at least three non-coaxial ultrasound focal points refers to either all focal points being non-coaxial, or some focal points being coaxial and others being non-coaxial.

[0048] In some embodiments, the design method for the composite Fresnel acoustic lens to realize multiple ultrasonic focal points in three-dimensional space includes two methods: (1) a superimposed composite Fresnel acoustic lens can be generated by superimposing the above two sets of coaxial multifocal Fresnel plates, retaining the overlapping area during superposition; (2) the overlapping area can be removed by superimposing the above two sets of coaxial multifocal Fresnel plates, and a rectangular support structure can be set to generate an alternating segmented composite Fresnel acoustic lens. The setting of the rectangular support follows the following standard: to ensure the overall stability and load-bearing capacity of the structure, the length of each set of rectangular support is not shorter than the radius of the corresponding coaxial multifocal Fresnel plate.

[0049] In one possible implementation, a composite Fresnel acoustic lens is designed, taking a coaxial dual-focal Fresnel zone plate as an example, such as... Figure 1 As shown, structurally, the coaxial bifocal Fresnel zone plate includes: an inner lens structure 1, an outer lens structure 2, and a dividing line 3 between the inner and outer lenses (in practical applications, the dividing line does not actually exist; it is only used here to distinguish the inner and outer lens structures). Both the inner lens structure 1 and the outer lens structure 2 are existing lens structures. In terms of material composition, the coaxial bifocal Fresnel zone plate includes: a frame region 4 and an ultrasonic transmission medium region 5.

[0050] It should be noted that the number of layers in the multi-layer lens structure described in this embodiment is determined by the number of focal points belonging to the same axis. Figure 1 The diagram shows a double-layer lens structure constructed when the two focal points are coaxial. The multi-layer lens structure described in this embodiment also includes a three-layer lens structure, a four-layer lens structure, etc., all of which fall within the protection scope of this invention.

[0051] In some embodiments, the spatial characteristics of the multifocal points generated by the composite Fresnel acoustic lens are: it can simultaneously realize at least three coaxial and non-axial ultrasonic focal points in three-dimensional space.

[0052] In some embodiments, the composite Fresnel acoustic lens generates multiple foci with simultaneity, stability, and robustness.

[0053] In some embodiments, the composite Fresnel acoustic lens generates multiple foci with a number of ≥3.

[0054] In some embodiments, the composite Fresnel acoustic lens is used in scenarios including but not limited to brain ultrasound stimulation or treatment, and other scenarios requiring multi-focal ultrasound focusing.

[0055] In some embodiments, the composite Fresnel acoustic lens is used in scenarios including but not limited to brain ultrasound stimulation or treatment, and other scenarios requiring multi-focal ultrasound focusing.

[0056] In some embodiments, the composite Fresnel acoustic lens is used in scenarios including but not limited to brain ultrasound stimulation or treatment, and other scenarios requiring multi-focal ultrasound focusing.

[0057] Referring to Figure 1 , the coaxial dual-focal Fresnel zone plate is composed of an inner lens structure 1 and an outer lens structure 2. The radii of the inner lens structure 1 and the outer lens structure 2 satisfy the formula:

[0058]

[0059] wherein r n is the radius of the nth annular Fresnel zone plate, λ is the wavelength of the ultrasound, and F is the corresponding lens focal length. The inner lens structure 1 and the outer lens structure 2 are calculated according to the above formula with different lens focal lengths to generate two foci with different focal lengths on the axis of the coaxial dual-focal Fresnel zone plate.

[0060] Referring to Figure 2 , the superimposed Fresnel acoustic lens is composed of a first border region 6 and a first ultrasound transmission medium region 7. The first border region 6 structure is composed of two groups of coaxial dual-focal Fresnel zone plates with the same structure, which are radially translated and superimposed. The transmitted acoustic field intensity satisfies the Rayleigh-Sommerfeld diffraction integral formula:

[0061]

[0062] wherein, I(x, y, z) is the acoustic intensity at the target (x, y, z) in the three-dimensional space coordinates, and λ is the wavelength of the ultrasound. p iE(x,y) is the amplitude of the incident field distribution before the superimposed composite Fresnel acoustic lens, τ i (x',y') is a transmission function, which satisfies In the formula, Z1 is the acoustic impedance of the background medium, and Z2 is the acoustic impedance of the material of the first frame area 6.

[0063] Referring to Figure 3 , the alternating split type composite Fresnel acoustic lens is composed of a second frame area 8, a second ultrasonic transmission medium area 9 and a rectangular support structure 10. The transmitted acoustic field intensity also satisfies the Rayleigh-Sommerfeld diffraction integral formula.

[0064] In some embodiments, the thickness of the rectangular support is the same as the thickness of the frame area to ensure sufficient bending strength; the width is as small as possible while maintaining stability, and in this embodiment, the width can be 4mm. In this embodiment, the number of rectangular supports is 4, which are uniformly distributed at an interval of 90° in the circumferential direction. All rectangular supports are made of the same material as the frame area and are integrally connected with the frame area.

[0065] Referring to Figure 4 , the focusing focal spot of the superimposed composite Fresnel acoustic lens is ellipsoidal and forms four foci at different positions. Referring to Figure 5 , the focusing focal spot of the alternating split type composite Fresnel acoustic lens is also ellipsoidal and forms four foci at different positions.

[0066] This embodiment takes a coaxial double-focus Fresnel area plate as an example to construct a composite Fresnel acoustic lens. In application, a coaxial three-focus Fresnel area plate or a coaxial four-focus Fresnel area plate can also be used to construct a composite Fresnel acoustic lens. The specific principle is as shown above, and will not be repeated here.

[0067] The present application realizes simultaneous focusing of multiple different axis and different depth ultrasonic target points by superimposing multiple groups of coaxial multi-focus Fresnel area plates, overcoming the limitation of limited coverage range of traditional single-focus lenses.

[0068] The present application provides two design schemes of superimposed composite Fresnel acoustic lens and alternating split type composite Fresnel acoustic lens, which can be selected according to specific application requirements, enhancing the flexibility and applicability of the design.

[0069] Embodiment two

[0070] The present embodiment provides a design method of a composite Fresnel acoustic lens, comprising:

[0071] Selecting a coaxial focus point in the preset focus point to obtain multiple coaxial multi-focus groups to construct a coaxial multi-focus Fresnel area plate; the process of constructing the coaxial multi-focus Fresnel area plate comprises:

[0072] For each coaxial multi-focal group, arrange the focal points in order from small to large focal length: each focal point corresponds to a layer of lens structure, the lens structure with small focal length is located in the inner layer, and the lens structure with large focal length is located in the outer layer;

[0073] Based on the ultrasonic wavelength and the preset focal length of each focal point, the radius of each Fresnel zone corresponding to each focal point is calculated by using the Fresnel half-wave zone theory, and the radius of the Fresnel zone includes the radius corresponding to the odd wave zone number and the radius corresponding to the even wave zone number; the radius corresponding to the odd wave zone number is set as the inner diameter of the frame area corresponding to the lens structure, and the radius corresponding to the even wave zone number is set as the outer diameter of the frame area corresponding to the lens structure;

[0074] The lens structure corresponding to each focal point is nested, and the number of Fresnel zones of each layer of lens structure is selected under the principle that the outer diameter of the frame area corresponding to the maximum wave zone number of the inner layer lens structure is smaller than the inner diameter of the frame area corresponding to the minimum wave zone number of the outer layer lens structure, thereby constructing a coaxial multi-focal Fresnel zone plate capable of generating coaxial multi-focal points;

[0075] At least two groups of coaxial multi-focal Fresnel zone plates capable of generating coaxial multi-focal points are stacked after being radially translated by a set distance, thereby constructing a composite Fresnel acoustic lens; the stacking processing mode includes: retaining the overlapping area during stacking to generate a stacked composite Fresnel acoustic lens; or removing the overlapping area after stacking and setting a rectangular support structure at some positions to generate an alternating segmented composite Fresnel acoustic lens.

[0076] The design method described in the embodiment is described in detail below by taking an example:

[0077] Step S1: the ultrasonic wavelength λ is 1.5 mm, and the preset focal lengths of the focal points with different focal lengths are F1=10 mm and F2=30 mm respectively; based on the Fresnel half-wave zone theory, the radius of each Fresnel zone corresponding to each focal point is calculated by using the following formula:

[0078]

[0079] wherein n is the wave zone order, and the number of Fresnel zones corresponding to each focal point is obtained through this step;

[0080] Step S2: the preset focal point group is divided into two types of coaxial multi-focal group and non-coaxial multi-focal group, and a coaxial dual-focal Fresnel zone plate capable of generating coaxial dual-focal points is first constructed: first, for the coaxial multi-focal group, arrange the focal points in order from small to large focal length, determine the focal point corresponding to the focal length F1=10 mm of the inner layer lens structure, and the focal point corresponding to the focal length F2=30 mm of the outer layer lens structure; the Fresnel zone number n of the inner layer lens structure ranges from 1 to 11, and the Fresnel zone number n of the outer layer lens structure ranges from 5 to 18; the inner diameter of each Fresnel zone plate is the radius r corresponding to the odd Fresnel zone number (odd wave zone number)2n-1 The outer diameter of each Fresnel zone plate is the radius r corresponding to the even Fresnel zone number (even zone number) 2n Wherein n is a positive integer. Secondly, the inner lens structure and the outer lens structure are implemented in a nested structure, while ensuring that the outer diameter of the frame area corresponding to the maximum zone number of the inner lens structure (15.5 mm) is less than the inner diameter of the frame area corresponding to the minimum zone number of the outer lens structure (15.7 mm), forming a coaxial bifocal Fresnel zone plate (see Figure 1 );

[0081] Step S3: Constructing a composite Fresnel acoustic lens capable of generating multiple focal points: The coaxial bifocal Fresnel zone plate generating coaxial multiple focal points is translated radially by a set distance and then stacked. The processing method after stacking includes:

[0082] Method one: Keep the overlapping area when stacking to generate a stacked composite Fresnel acoustic lens (see Figure 2 );

[0083] Method two: Remove the overlapping area when stacking and set a rectangular support structure at some positions to generate an alternating segmented composite Fresnel acoustic lens (see Figure 3 )。

[0084] In this embodiment, the set distance is related to the distance between different focal points, which can be 10 mm. It should be noted that this embodiment only provides an implementation manner, and the set distance should not be understood as a specific limitation. In other embodiments, the set distance can also take other values.

[0085] Embodiment three

[0086] As shown in Figure 6 , this embodiment provides a composite Fresnel acoustic lens skull window replacement system, which uses the composite Fresnel acoustic lens 13 described in embodiment one to replace part of the skull. Plane ultrasound forms at least three focal spots (two focal spots in the cerebral cortex area 15 and the deep brain nucleus area 16 respectively) at the target position in the skull through the composite Fresnel acoustic lens 13, which can simultaneously stimulate the left and right cerebral cortex 15 and the deep brain nucleus area 16 for ultrasonic combined stimulation. Its application scenarios include but are not limited to sleep aid brain function regulation and ultrasonic treatment of brain diseases such as brain epilepsy and Alzheimer's disease.

[0087] In this embodiment, plane ultrasound can be emitted by introducing a plane ultrasonic transducer 11.

[0088] It should be noted that the composite Fresnel acoustic lens 13 used to replace the skull window must meet the biological compatibility.

[0089] In some embodiments, the composite Fresnel acoustic lens 13 is fixed to the edge of the missing cranial window by a biocompatible adhesive, the outer side (towards the planar ultrasonic transducer) surface is coated with an ultrasonic coupling agent 12, and is tightly attached to the planar ultrasonic transducer 11 to form an acoustic wave transmission path. In this embodiment, the composite Fresnel acoustic lens 13 and the planar ultrasonic transducer 11 can also be connected without the ultrasonic coupling agent 12, and can be directly connected.

[0090] In this embodiment, the materials of the first frame area 6, the second frame area 8, and the rectangular support structure 10 are titanium alloy TC4, which are prepared by 3D printing technology to improve the printing accuracy and enhance the pressure resistance of the cranial window. The materials of the first frame area 6, the second frame area 8, and the rectangular support structure 10 are only exemplary and are not limited thereto. Any related material that has biocompatibility and can realize the functions of the first frame area 6, the second frame area 8, and the rectangular support structure 10 should belong to the protection scope of the present application.

[0091] In this embodiment, the materials of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 are polydimethylsiloxane (PDMS), and the mass ratio of the base polymer to the curing agent is 10:1, so as to utilize the good acoustic transmission performance to enhance ultrasonic transmission and reduce energy attenuation. The materials of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 are only exemplary and are not limited thereto. Any other material that has biocompatibility and can realize the functions of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 should belong to the protection scope of the present application.

[0092] In this embodiment, the first frame area 6, the second frame area 8, the first ultrasonic transmission medium area 7, the second ultrasonic transmission medium area 9, and the rectangular support structure 10 of the composite Fresnel acoustic lens can be prepared by various methods such as 3D printing technology, casting technology, and demolding technology.

[0093] The composite Fresnel acoustic lens cranial window structure of the present application provides a feasible path for a more comprehensive and efficient treatment scheme for brain multi-lesion areas, effectively reduces the attenuation and distortion of acoustic signals by the skull, reduces the calculation cost of ultrasonic excitation signal generation, and has a wide application prospect.

[0094] Embodiment Four

[0095] As shown in Figure 7 The present embodiment provides a detachable composite Fresnel acoustic lens assembly suitable for a planar ultrasonic transducer, which comprises a superimposed composite Fresnel acoustic lens 17, a planar ultrasonic transducer 11, an alternating segmented composite Fresnel acoustic lens 18, a main support clamp base 20, a vice support clamp module 19, and a transducer-base connecting column 21.

[0096] Specifically, the superimposed composite Fresnel acoustic lens 17 and the two sides of the alternating split composite Fresnel acoustic lens 18 are symmetrically provided with a secondary support clamp module 19. The main support clamp base 20 is internally provided with a rectangular clamping cavity, the inner contour of which matches the outer dimensions of the secondary support clamp module 19, and the secondary support clamp module 19 is rigidly locked by being axially embedded in the rectangular clamping cavity. The main support clamp base 20 and the transducer-base connecting column 21 adopt an integrated connection structure, and the inner diameter tolerance of the transducer-base connecting column 21 and the outer diameter tolerance of the planar ultrasonic transducer 11 meet the interference fit requirements. When assembling, the transducer-base connecting column 21 is sleeved on the outer periphery of the planar ultrasonic transducer 11 through the interference fit, and the quick installation of the overall assembly is completed.

[0097] The embodiment significantly improves the flexibility and functionality of the ultrasonic focusing system through modular structure design. The quick disassembly and assembly of the lens assembly are realized through the rigid locking of the main support clamp base 20 and the secondary support clamp module 19, which effectively guarantees the spatial consistency of the multi-focus acoustic field. The structure can dynamically switch the lens and simultaneously generate at least three non-coaxial ultrasonic focal points in three-dimensional space, providing an efficient and reliable hardware solution for transcranial multi-target point treatment.

[0098] In the embodiment, the planar ultrasonic transducer 11 can be used as a standard accessory of an ultrasonic transducer, widening the application scenarios of a single planar ultrasonic transducer and improving the applicability and effectiveness of transcranial ultrasonic treatment.

[0099] In another embodiment, the planar ultrasonic transducer 11, especially the composite Fresnel acoustic lens therein, can be customized according to the ultrasonic frequency and the position of the brain area involved in treatment, providing personalized accessories for users and improving the personalization and effectiveness of transcranial ultrasonic treatment.

[0100] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A compound Fresnel acoustic lens, characterized in that, The application relates to a composite Fresnel acoustic lens, which comprises at least two groups of coaxial multi-focus Fresnel zone plates, and the at least two groups of coaxial multi-focus Fresnel zone plates are stacked after being radially translated by a set distance to generate at least three non-coaxial ultrasonic focal points in a three-dimensional space, and the composite Fresnel acoustic lens can be used for transcranial ultrasonic stimulation or treatment of the brain. The coaxial multi-focus Fresnel zone plate comprises a multi-layer lens structure which is nested together, and the multi-layer lens structure comprises a frame area and an ultrasonic transmission medium area. The coaxial multi-focus Fresnel zone plate uses a Fresnel half-wave band theory to calculate the radius of each Fresnel wave band corresponding to each focal point. n is the wave band series, and the number of Fresnel wave bands corresponding to each focal point is obtained through the step. The definition of ultrasonic wavelength is λ, and the preset focal lengths of the focal points with different focal lengths are , Based on the Fresnel half-wave band theory, the following formula is used to calculate the Fresnel band radius corresponding to each focal point: The stacked composite Fresnel acoustic lens comprises a first frame area and a first ultrasonic transmission medium area, and the first frame area is formed by radially stacking at least two groups of the same coaxial multi-focus Fresnel zone plates. The preset focal point group is divided into coaxial multi-focal point group and non-coaxial multi-focal point group, and a coaxial bifocal Fresnel zone plate capable of generating coaxial bifocal points is first constructed; first, for the coaxial multi-focal point group, arranging each focal point in ascending order of focal length, determining the focal points corresponding to the focal length of the inner lens structure and the focal points corresponding to the focal length of the outer lens structure ; the number n of the Fresnel wave bands of the inner lens structure ranges from 1 to 11, and the number n of the Fresnel wave bands of the outer lens structure ranges from 5 to 18, the inner diameter of each Fresnel wave band piece is the radius corresponding to the odd wave band number , and the outer diameter of each Fresnel wave band piece is the radius corresponding to the even wave band number , wherein n is a positive integer; secondly, the inner lens structure and the outer lens structure are implemented to be nested, while ensuring that the outer diameter of the frame area corresponding to the maximum wave band number of the inner lens structure is smaller than the inner diameter of the frame area corresponding to the minimum wave band number of the outer lens structure, to form a coaxial bifocal Fresnel zone plate; the coaxial bifocal Fresnel zone plate capable of generating coaxial multi-focal points is translated along the radial direction by a set distance and then superimposed to construct a composite Fresnel acoustic lens capable of generating multi-focal points; at least two groups of coaxial multi-focal point Fresnel zone plates are stacked to generate a stacked composite Fresnel acoustic lens, and the overlapping area is reserved during stacking. The application relates to a composite Fresnel acoustic lens, which comprises at least two groups of coaxial multi-focus Fresnel zone plates, and the at least two groups of coaxial multi-focus Fresnel zone plates are stacked after being radially translated by a set distance to generate at least three non-coaxial ultrasonic focal points in a three-dimensional space, and the composite Fresnel acoustic lens can be used for transcranial ultrasonic stimulation or treatment of the brain.

2. Compound Fresnel acoustic lens, characterized in that, The coaxial multi-focus Fresnel zone plate comprises a multi-layer lens structure which is nested together, and the multi-layer lens structure comprises a frame area and an ultrasonic transmission medium area. The coaxial multi-focus Fresnel zone plate uses a Fresnel half-wave band theory to calculate the radius of each Fresnel wave band corresponding to each focal point. n is the wave band series, and the number of Fresnel wave bands corresponding to each focal point is obtained through the step. The application relates to a composite Fresnel acoustic lens, which comprises at least two groups of coaxial multi-focus Fresnel zone plates, and the at least two groups of coaxial multi-focus Fresnel zone plates are stacked after being radially translated by a set distance to generate at least three non-coaxial ultrasonic focal points in a three-dimensional space, and the composite Fresnel acoustic lens can be used for transcranial ultrasonic stimulation or treatment of the brain. The definition of ultrasonic wavelength is λ, and the preset focal lengths of the focal points with different focal lengths are respectively , Based on the Fresnel half-wave band theory, the following formula is used to calculate the Fresnel band radius corresponding to each focal point: The composite Fresnel acoustic lens comprises a second frame area, a second ultrasonic transmission medium area and a rectangular support structure. The preset focal point group is divided into coaxial multi-focal point group and non-coaxial multi-focal point group, a coaxial bifocal Fresnel zone plate capable of generating coaxial bifocal points is constructed first: first, for the coaxial multi-focal point group, arrange the focal points in ascending order of focal length, determine the focal points corresponding to the focal length of the inner lens structure and the focal points corresponding to the focal length of the outer lens structure ; the number n of the Fresnel wave bands of the inner lens structure ranges from 1 to 11, and the number n of the Fresnel wave bands of the outer lens structure ranges from 5 to 18, the inner diameter of each Fresnel wave band piece is the radius corresponding to the odd wave band number , and the outer diameter of each Fresnel wave band piece is the radius corresponding to the even wave band number , wherein n is a positive integer; secondly, the inner lens structure and the outer lens structure are implemented to be nested, while ensuring that the outer diameter of the frame area corresponding to the maximum wave band number of the inner lens structure is smaller than the inner diameter of the frame area corresponding to the minimum wave band number of the outer lens structure, to form the coaxial bifocal Fresnel zone plate; the coaxial bifocal Fresnel zone plate capable of generating coaxial multi-focal points is translated along the radial direction by a set distance and then superimposed to construct a composite Fresnel acoustic lens capable of generating multi-focal points; 3. A design method of the composite Fresnel acoustic lens according to any one of claims 1-2, comprising: selecting coaxial focal points in preset focal points to obtain a plurality of coaxial multi-focus groups to construct coaxial multi-focus Fresnel zone plates; the process of constructing the coaxial multi-focus Fresnel zone plates comprises: arranging the focal points in each coaxial multi-focus group in order from small to large focal length: each focal point corresponds to a layer of lens structure, the lens structure with small focal length is located in the inner layer, and the lens structure with large focal length is located in the outer layer; based on the ultrasonic wavelength and the preset focal length of each focal point, the radius of each Fresnel wave band corresponding to each focal point is calculated by using the Fresnel half-wave band theory, the radius of the Fresnel wave band comprises the radius corresponding to the odd wave band number and the radius corresponding to the even wave band number; the radius corresponding to the odd wave band number is set as the inner diameter of the corresponding lens structure frame area, and the radius corresponding to the even wave band number is set as the outer diameter of the corresponding lens structure frame area; nesting the lens structure corresponding to each focal point, and selecting the number of Fresnel wave bands of each layer of lens structure to construct the coaxial multi-focus Fresnel zone plate capable of generating coaxial multi-focus under the principle of ensuring that the outer diameter of the frame area corresponding to the maximum wave band number of the inner layer lens structure is smaller than the inner diameter of the frame area corresponding to the minimum wave band number of the outer layer lens structure. ​ ​ At least two groups of coaxial multi-focal Fresnel zone plates capable of generating coaxial multi-foci are radially translated by a set distance and then superimposed to construct a composite Fresnel acoustic lens; the processing method after superposition includes: retaining the overlapping area during superposition to generate a superimposed composite Fresnel acoustic lens; removing the overlapping area after superposition and setting a rectangular support structure at certain positions to generate an alternating segmented composite Fresnel acoustic lens.

4. A planar ultrasound transducer assembly, characterized by Comprise: The composite Fresnel acoustic lens of any one of claims 1-2, wherein a vice support clamp module and a main support clamp base are symmetrically arranged on both sides of the composite Fresnel acoustic lens, the main support clamp base is internally provided with a rectangular clamping cavity, the contour of which matches the outer dimensions of the vice support clamp module, rigid locking is achieved by axially embedding the vice support clamp module into the rectangular clamping cavity, the main support clamp base and a transducer-base connecting column adopt an integrated connection structure, the transducer-base connecting column is sleeved around the outer periphery of a planar ultrasonic transducer and is in interference fit with the planar ultrasonic transducer, and the composite Fresnel acoustic lens is nested on the transducer-base connecting column.

5. The planar ultrasonic transducer assembly of claim 4, wherein, The inner diameter tolerance of the transducer-base connecting column and the outer diameter tolerance of the planar ultrasonic transducer meet the interference fit requirements.

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