Individualized transcranial ultrasound focusing correction device and method

Abstract

This invention discloses a personalized transcranial ultrasound focusing correction device and method. The device includes a combined holographic acoustic phase plate for phase modulation of the ultrasonic wavefront emitted by an ultrasonic transducer and a non-fully enclosed shell for fixing and protecting the combined holographic acoustic phase plate. The combined holographic acoustic phase plate includes a first holographic acoustic phase plate and a second holographic acoustic phase plate arranged parallel to each other along the sound wave propagation axis. The first holographic acoustic phase plate has an incident surface facing the ultrasonic transducer and a first holographic surface opposite to it. The second holographic acoustic phase plate has an exit surface facing the outer surface of the target skull and a second holographic surface opposite to it. The first and second holographic surfaces are arranged opposite each other, forming a liquid layer filled with acoustic coupling fluid between them. This invention has a relatively simple structure, low cost, and can achieve personalized phase correction, effectively improving focusing accuracy.

Description

Technical Field

[0001] This invention relates to the field of non-invasive ultrasound correction devices, specifically to a personalized transcranial ultrasound focused correction device and method. Background Technology

[0002] Transcranial ultrasound techniques, such as focused ultrasound, hold significant promise for applications in neuromodulation and tumor treatment. However, the skull, as a medium with high acoustic impedance, non-uniformity, and significant individual variability, severely distorts the wavefront phase of transmitted ultrasound, leading to focal defocusing, displacement, and deformation. This significantly reduces treatment effectiveness and may damage non-target tissues. Current technologies, while using liquid-filled hemispherical ultrasound transducers to achieve coupling, cannot correct the individualized phase distortion caused by the skull. While ultrasound phased array all-electronic focusing systems based on MRI imaging can achieve dynamic correction, they are costly and complex.

[0003] Therefore, there is an urgent need for a passive device with a relatively simple structure, low cost, and the ability to achieve individualized phase correction, in order to improve the transcranial focusing accuracy of existing conventional single-element or planar transducer systems. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a personalized transcranial ultrasound focusing correction device and method.

[0005] The objective of this invention is achieved through the following technical solution: A first aspect of this invention provides a personalized transcranial ultrasound focusing correction device, comprising: A combined holographic acoustic phase plate is used for phase modulation of the ultrasonic wavefront emitted by an ultrasonic transducer; and A non-fully enclosed housing for securing and protecting the combined holographic acoustic phase plate; The combined holographic acoustic phase plate includes a first holographic acoustic phase plate and a second holographic acoustic phase plate arranged parallel to each other along the sound wave propagation axis. The first holographic acoustic phase plate has an incident surface facing the ultrasonic transducer and a first holographic surface disposed opposite to it. The incident surface is a smooth plane or a smooth arc surface, and the first holographic surface is an uneven surface with a specific uneven distribution processed according to individualized calculation data. The second holographic acoustic phase plate has an exit surface facing the outer surface of the skull of the target object and a second holographic surface disposed opposite to it. The exit surface is a smooth plane, and the second holographic surface is an uneven surface with a specific uneven distribution processed according to individualized calculation data. The first holographic surface and the second holographic surface are arranged opposite each other, and a liquid layer filled with acoustic coupling liquid is formed between them.

[0006] Furthermore, the first holographic acoustic phase plate is made of a material with an acoustic impedance similar to that of the ultrasonic transducer matching layer; the second holographic acoustic phase plate is made of a material with an acoustic impedance similar to that of the soft tissue of the head.

[0007] Furthermore, both the first and second holographic surfaces are composed of multiple three-dimensional structural units arranged closely together. Each three-dimensional structural unit has the same thickness at all points, and the thicknesses of different three-dimensional structural units are different.

[0008] Furthermore, the first holographic acoustic phase plate and the second holographic acoustic phase plate are fixed at their distance by positioning buckles on the outer shell.

[0009] A second aspect of this invention provides a design method for the aforementioned individualized transcranial ultrasound focusing correction device, comprising the following steps: S1. Acquire individualized anatomical data and preset target location data: Obtain three-dimensional geometric model data of the skull of the target object through medical imaging; determine the position coordinates of the preset target points in the same three-dimensional coordinate system, and determine the expected placement and orientation of the ultrasound transducer; at the same time, adopt a coordinate system fusion method based on stereotactic frame and marker registration to establish a unified spatial benchmark from image space to physical space, so as to achieve a one-to-one correspondence between the ultrasound transducer and the preset target points in space. S2. Calculate the target wavefront phase distribution: Based on the individualized anatomical data and preset target location data obtained in step S1, construct a non-uniform medium acoustic model, and use the principle of sound field reverse propagation to solve the ideal wavefront phase distribution required to focus the ultrasound at the preset target point T. S3. Joint design of holographic acoustic phase plates: Jointly design the thickness distribution of the first and second holographic acoustic phase plates so that the phase distribution generated by the exit surface of the correction device is equal to the ideal wavefront phase distribution. S4. Device fabrication and integration: The first and second holographic acoustic phase plates are fabricated using the thickness distribution data of the first and second holographic acoustic phase plates, and installed in the housing using positioning buckles. After injecting acoustic coupling liquid through the injection hole, the device is sealed to obtain the correction device.

[0010] Furthermore, the coordinate system fusion method based on the registration of the stereo orientation frame and the marker points specifically includes the following sub-steps: (a1) Three non-collinear high-density metal head mold markers are placed on the scalp of the target object to establish a spatial reference base for the skull; wherein the three head mold markers form an equilateral triangle or an isosceles triangle, the distance between any two head mold markers is greater than or equal to 3cm, and the diameter of the head mold markers is 3-5mm. (a2) Set three non-collinear metal probe markers on the fixed support of the ultrasonic transducer, and the plane where the three probe markers are located is perpendicular to the acoustic axis of the ultrasonic transducer to establish a spatial reference for the transducer. (a3) Simultaneously acquire image data of skull structure, preset target point T, head mold marker point and probe marker point in the same medical image, and extract the three-dimensional coordinates of skull structure contour, preset target point T, head mold marker point and probe marker point in image space; wherein, the head mold marker point and probe marker point are automatically identified by threshold segmentation based on the high brightness characteristics of their high-density metallic material in CT images; the preset target point T is manually calibrated in the image; (a4) Measure the three-dimensional coordinates of the head model marker point and the probe marker point in the physical space using an optical navigation system or a mechanical positioning arm. Use the corresponding three-dimensional coordinates of the head model marker point and the probe marker point in the image space and the physical space as input. Calculate the rigid transformation matrix M from the virtual image space to the real physical space using a point set registration algorithm as a unified spatial reference. The point set registration algorithm uses singular value decomposition.

[0011] Further, step S2 specifically includes: First, based on the unified spatial reference established in step S1, the outer surface of the target area to which the exit surface of the correction device is expected to fit is mapped to the three-dimensional geometric model of the skull. The CT gray value of the outer surface of the target area is extracted, the porosity at the corresponding position is calculated based on the gray value, and the density, sound velocity and attenuation coefficient at the corresponding position are calculated based on the porosity. Then, the preset target point T is set as a single-pole virtual sound source point, and the finite element analysis is used to simulate the ultrasonic wave propagating backward from the preset target point T to the outer surface of the target area, and the phase distribution of the outer surface of the target area is obtained as the desired ideal wavefront phase distribution.

[0012] Furthermore, the porosity is calculated according to the following formula: In the formula, r is a point on the outer surface of the target region. Let r be the porosity at point r on the outer surface of the target region. The CT gray value at point r is... The CT grayscale value of water. The CT grayscale value of compact bone; The density is calculated according to the following formula: In the formula, Let r be the density at point r on the outer surface of the target region. The density of water, The density of compact bone; The speed of sound is calculated according to the following formula: In the formula, Let r be the speed of sound at point r on the outer surface of the target region. The speed of sound in water. The speed of sound in compact bone; The attenuation coefficient is calculated according to the following formula: In the formula, f is the ultrasonic operating frequency. Let r be the attenuation coefficient of a point r on the outer surface of the target region at frequency f. This is the baseline attenuation coefficient.

[0013] Furthermore, the thickness distribution of the first holographic acoustic phase plate and the second holographic acoustic phase plate is obtained specifically through the following method: The total phase modulation amount required at point r on the exit surface of the correction device for: In the formula, The ideal wavefront phase distribution at point r on the outer surface of the target region. The initial phase of the incident wave, Here, n is the phase winding term, and n is the adjustment coefficient. For any coordinate point r on the holographic surface of the holographic acoustic phase plate, the acoustic wave phase delay With thickness satisfy: In the formula, To distinguish the labels of the two holographic acoustic phase plates, For the acoustic wave phase delay of the j-th holographic acoustic phase plate, The wavelength of the sound wave in the acoustic coupling liquid at the ultrasonic operating frequency. Let be the acoustic refractive index of the j-th holographic acoustic phase plate. Let be the acoustic refractive index of the acoustic coupling liquid. Let r be the thickness distribution at point r on the j-th holographic acoustic phase plate; Set a fixed value Q such that the thickness distribution at any coordinate point r on the holographic surface of the two holographic acoustic phase plates satisfies Solving the system of equations and combining it with the least squares phase expansion method yields a continuous thickness distribution. and ,in and The thickness distributions at point r on the first and second holographic acoustic phase plates are respectively, and the fixed value Q is selected based on the principle that Q ≥ λ / 2.

[0014] Furthermore, following step S4, a normal alignment calibration step is also included: Extract the 3D point cloud data of the outer surface of the target area to be fitted by the exit surface of the correction device, and calculate the average normal vector: In the formula, Let S be the normalized average normal vector, and S be the set of three-dimensional point clouds on the outer surface of the target region to be fitted by the exit surface of the correction device. Let be the local normal vector of the i-th grid point or voxel. The weight coefficient for the i-th grid point or voxel; Using the rigid transformation matrix M to transform the average normal vector Transform to the transducer local coordinate system to obtain the target attitude vector. : In the formula, R is the rotation matrix, which is obtained by extracting the rotation components from the rigid transformation matrix M; Adjust the mounting bracket of the ultrasonic transducer probe so that the acoustic axis direction is aligned with the target attitude vector. Strictly collinear and opposite in direction.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention achieves precise pre-compensation for individual skull phase distortion through a combination structure of a dual-phase plate and a liquid layer, significantly improving the focusing accuracy of transcranial ultrasound; this invention can passively pre-modulate the incident ultrasound waves based on the patient's specific skull anatomy, compensating for the phase distortion generated when the waves pass through the individual's skull, thereby enabling precise focusing of the ultrasound waves at a preset target point within the skull; this invention uses individualized acoustic parameter modeling based on CT data (porosity, density, sound velocity, attenuation coefficient) for more accurate compensation; the device structure is simple, can be integrated with conventional transducers and skull target surfaces, has controllable costs, and is easy to integrate clinically; this invention reduces energy loss caused by oblique ultrasound incidence through normal alignment calibration, greatly improving the efficiency of sound wave focusing and thus improving treatment efficiency; this invention is suitable for transcranial ultrasound treatment of brain diseases, improving focusing accuracy by compensating for ultrasound phase distortion caused by the skull through individualized design. Attached Figure Description

[0016] Figure 1 This is a schematic cross-sectional view of the individualized transcranial ultrasound focusing correction device of the present invention; Figure 2 This is a schematic diagram of the structure of the first holographic acoustic phase plate and the second holographic acoustic phase plate of the present invention; Figure 3 This is a flowchart of the individualized transcranial ultrasound focused correction method of the present invention.

[0017] In the figure, the outer shell 1, the injection hole 11, the first holographic acoustic phase plate 2, the incident surface 21, the first holographic surface 22, the second holographic acoustic phase plate 3, the exit surface 31, the second holographic surface 32, and the acoustic coupling liquid 4 are shown. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0020] It should be understood that although the terms first, second, third, etc., may be used in this invention to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of this invention, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0021] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0022] Example 1: Personalized transcranial ultrasound focused correction device The individualized transcranial ultrasound focusing correction device of the present invention can perfectly fit with a conventional ultrasound transducer and the outer surface of the target area of ​​the patient's skull. In use, the two side surfaces of the correction device can directly fit with the conventional ultrasound transducer and the outer surface of the target area, greatly improving the efficiency of sound wave focusing.

[0023] See Figure 1The correction device includes a combined holographic acoustic phase plate and a non-fully enclosed shell 1. The combined holographic acoustic phase plate is the core functional component of the correction device, used to modulate the phase of the wavefront of ultrasonic waves (such as plane waves or spherical waves) emitted by the ultrasonic transducer. The shell 1 is used to fix and protect the combined holographic acoustic phase plate.

[0024] like Figure 1 and Figure 2 As shown, the combined holographic acoustic phase plate is a combined focusing acoustic lens structure composed of two holographic acoustic phase plates (i.e., the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3) with fixed relative positions. It is used to focus the ultrasonic wavefront emitted by the ultrasonic transducer after phase modulation, so that it acts on the target object. The combined holographic acoustic phase plate includes the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 arranged parallel to each other along the sound wave propagation axis. Among them, the first holographic acoustic phase plate 2 adopts a flat plate structure. The first holographic acoustic phase plate 2 has an incident surface 21 facing the ultrasonic transducer and a first holographic surface 22 arranged opposite to it. The incident surface 21 is a smooth plane or a smooth arc surface, and the first holographic surface 22 is an uneven surface with a specific concave-convex distribution processed according to individualized calculation data. The second holographic acoustic phase plate 3 adopts a flat plate structure. The second holographic acoustic phase plate 3 has an exit surface 31 facing the outer surface of the target object's skull and a second holographic surface 32 arranged opposite to it. The exit surface 31 is a smooth plane that fits the outer surface of the target object's skull. The second holographic surface 32 is an uneven surface with a specific uneven distribution processed according to individualized calculation data. The first holographic surface 22 and the second holographic surface 32 are arranged opposite to each other, and a liquid layer filled with acoustic coupling liquid 4 is formed between them.

[0025] Furthermore, the first holographic acoustic phase plate 2 is made of a material with an acoustic impedance similar to that of the matching layer of the ultrasonic transducer, that is, the acoustic impedance of the first holographic acoustic phase plate 2 is matched with the matching layer material of the ultrasonic transducer; the second holographic acoustic phase plate 3 is made of a material with an acoustic impedance similar to that of the soft tissue of the head, that is, the acoustic impedance of the second holographic acoustic phase plate 3 is matched with the soft tissue material of the head, so as to ensure that the ultrasonic waves are efficiently transmitted to the skull.

[0026] Furthermore, the uneven surfaces of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3, namely the first holographic surface 22 and the second holographic surface 32, are both composed of multiple three-dimensional structural units arranged closely together. Each three-dimensional structural unit has the same thickness at all points, and the thickness of different three-dimensional structural units may vary. The multiple three-dimensional structural units are arranged in an array, closely together, without gaps or overlaps.

[0027] Furthermore, the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 are fixed at their distance by positioning clips on the outer shell 1. The first holographic surface 22 and the second holographic surface 32 are arranged opposite each other, while the incident surface 21 and the exit surface 31 are arranged outwards, respectively facing the ultrasonic transducer and adhering to the outer surface of the target object's skull. An acoustic coupling liquid 4 is filled between the first holographic surface 22 and the second holographic surface 32 to form a liquid layer. This liquid layer is used for sound wave transmission, and the thickness distribution of the liquid layer is determined by the concave and convex structures of the first holographic surface 22 and the second holographic surface 32 and the relative distance between them defined by the positioning clips on the outer shell 1, and the thickness of the liquid layer is non-uniformly distributed.

[0028] Furthermore, the acoustic coupling liquid 4 has the characteristics of low acoustic attenuation coefficient, good sound transmission, moderate moisturizing and viscosity, high appearance transparency, no bubbles, good uniformity, no particles or impurities, good stability, and non-irritating to the skin.

[0029] Furthermore, the outer shell 1 is a non-fully enclosed structure used to fix and protect the combined holographic acoustic phase plate, maintain the precise distance between the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3, and form a cavity to accommodate the acoustic coupling liquid 4. The outer shell 1 is provided with an injection hole 11 for injecting the acoustic coupling liquid 4 and discharging air bubbles in the acoustic coupling liquid 4 to ensure that there are no air bubbles in the acoustic coupling liquid 4.

[0030] Example 2: Design Method of Individualized Transcranial Ultrasound Focused Correction Device See Figure 3 The design method of the individualized transcranial ultrasound focusing correction device of the present invention is based on the core principle of sound field back propagation calculation and phase conjugate compensation, and specifically includes the following steps: S1. Acquire individualized anatomical data and pre-defined target location data: Obtain three-dimensional geometric model data of the target object's skull through medical imaging; determine the position coordinates of the pre-defined target point (i.e., intracranial stimulation target point or treatment target point) T in the same three-dimensional coordinate system. The expected placement and orientation of the ultrasonic transducer are determined to ensure that the center of the ultrasonic transducer and the center of the correction device are coaxial. At the same time, a coordinate system fusion method based on stereoscopic orientation frame and marker point registration is adopted to establish a unified spatial reference from image space to physical space, so as to achieve a precise one-to-one correspondence between the ultrasonic transducer and the preset target point in space.

[0031] Furthermore, when acquiring the three-dimensional geometric model data of the skull of the target object through medical imaging, high-resolution computed tomography (CT) images of the head of the target object, i.e., the patient to be treated, are first acquired. Then, medical image processing software (such as 3D Slicer, Mimics, etc.) is used to segment the CT images and extract the three-dimensional geometric model of the skull of the target object.

[0032] Furthermore, within the same three-dimensional coordinate system, and in conjunction with the clinical treatment plan, the three-dimensional spatial coordinates of the pre-defined target point (i.e., the intracranial stimulation target point or treatment target point) T are determined. On the outer surface of the three-dimensional geometric model of the skull, based on the expected treatment position (i.e., the preset target point) and the expected placement of the ultrasound transducer, a flat or head-shape-adapted area is determined as the outer surface of the target area that the emission surface 31 of the corrective device described in this invention needs to closely conform to. .

[0033] Furthermore, the coordinate system fusion method based on the registration of the stereoscopic frame and marker points specifically includes: (a1) Establishing a spatial reference base for the skull: Before acquiring medical images, three non-collinear high-density metal head mold markers are placed on the epidermis of the target subject's head to establish a spatial reference base for the skull. The three head mold markers form an equilateral or isosceles triangle, with a distance of at least 3 cm between any two markers, and a diameter of 3-5 mm. These head mold markers are clearly visible in medical images and are used to establish a set of spatial reference points corresponding to the anatomical structures of the target subject in the image space.

[0034] (a2) Establishing a transducer spatial reference datum: According to the treatment plan, the ultrasound transducer is installed in a specific rigid area of ​​a fixed support. The mechanical structure design of this fixed support ensures the initial coaxial relationship between the center of the ultrasound transducer and the geometric center of the corrective device described in this invention. Three non-collinear metal probe markers are set at appropriate positions on the fixed support of the ultrasound transducer (i.e., positions that are identifiable in imaging and subsequent operations), and the plane containing the three probe markers is perpendicular to the acoustic axis of the ultrasound transducer to establish a transducer spatial reference datum. The acoustic axis is the main axis of the ultrasound beam propagation, coinciding with the geometric center of the ultrasound transducer and perpendicular to its emission surface. By setting the plane containing the probe markers perpendicular to the acoustic axis, a reference datum orthogonal to the acoustic beam direction can be established in the imaging space, which is the transducer spatial reference datum, thereby accurately describing the spatial orientation of the acoustic beam. This acoustic axis direction serves as the reference input for the incident direction of the sound wave in subsequent back-propagation calculations of the sound field, used to determine the path and incident angle of transcranial ultrasound propagation.

[0035] (a3) Image Acquisition and Target Localization: Image data of the skull structure, the pre-defined target point T, the head model marker, and the probe marker are simultaneously acquired within the same medical image (such as CT or MRI image). Using medical image processing technology, image segmentation, threshold segmentation, edge detection, and 3D reconstruction are performed sequentially to identify and extract the skull structure contour, the pre-defined target point T, and the 3D coordinates of the head model marker and probe marker in the image space. The head model marker and probe marker are automatically identified using threshold segmentation based on the significant high-brightness characteristics of their high-density metallic material in CT images; the pre-defined target point T is manually marked in the image by the clinician according to the treatment plan.

[0036] (a4) Coordinate System Transformation and Spatial Alignment: In image space, the head model marker points and probe marker points are already in the same coordinate system. To achieve accurate mapping from image space to physical space, the three-dimensional coordinates of the head model marker points and probe marker points in physical space are measured using an optical navigation system or a mechanical positioning arm. Specifically, a coordinate system for the head model marker points is established with the geometric center of the plane formed by the three head model marker points as the origin, the plane containing the three head model marker points as the reference plane (such as the XY plane), and the normal direction of the reference plane as the Z-axis. Then, the three-dimensional coordinates of the head model marker points and probe marker points are obtained by combining coordinate acquisition methods such as optical navigation systems. Using the corresponding three-dimensional coordinates of the two sets of marker points, namely the head model marker points and probe marker points, in image space and physical space as input, the rigid transformation matrix M from virtual image space to real physical space is calculated by the point set registration algorithm as a unified spatial reference, thereby achieving a precise one-to-one correspondence between the ultrasonic transducer and the preset target point in space. Among them, the point set registration algorithm adopts the singular value decomposition method. The rigid transformation matrix M establishes a mapping relationship between the virtual image space and the real physical space, so that the planned intracranial pre-target point T, the skull geometry, and the correction device and the area attached to the skull described in this invention can be accurately converted to the physical space, providing a unified spatial reference for subsequent operations.

[0037] S2. Calculate the target wavefront phase distribution: Based on the individualized anatomical data and preset target point location data obtained in step S1, construct a non-uniform medium acoustic model. Utilize the principle of sound field back propagation to solve for the ideal wavefront phase distribution required for precise focusing of ultrasound waves at the preset target point T, and apply it to the outer surface of the target area of ​​the skull. This allows the ultrasonic energy to be perfectly focused at the preset target point T.

[0038] Specifically, firstly, based on the coordinate system fusion relationship (i.e., unified spatial reference) established in step S1, the outer surface of the target area to which the exit surface 31 of the correction device described in this invention is expected to fit is... Mapped to a 3D geometric model of the skull, the CT grayscale values ​​(Hounsfield Unit, HU) of the outer surface of the target region are extracted. Based on these grayscale values, the porosity at the corresponding location is calculated, and then the density, sound velocity, and attenuation coefficient at that location are calculated based on the porosity. A preset target point T is then set as a unipolar virtual sound source point, and finite element analysis is used to simulate the reverse propagation of ultrasonic waves (such as spherical waves) from the preset target point T to the outer surface of the target region of the skull. The phase distribution of the outer surface of the target region of the skull is obtained. This serves as the desired ideal wavefront phase distribution.

[0039] Furthermore, porosity is calculated using the following formula: In the formula, r is a point on the outer surface of the target region. Let r be the porosity at point r on the outer surface of the target region. The CT gray value at point r; The CT grayscale value of water is 0; This refers to the CT grayscale value of compact bone, which is set to 1000, or adaptively selected based on the individual peak value of the target object. The value of .

[0040] Furthermore, the density is calculated using the following formula: In the formula, Let r be the density at point r on the outer surface of the target region; The density of water is taken as 1000 kg / m³. 3 ; The density of compact bone is measured in the range of 1900~2000 kg / m³. 3 .

[0041] Furthermore, the speed of sound is calculated using the following formula: In the formula, Let r be the speed of sound at point r on the outer surface of the target region; The speed of sound in water is 1500 m / s; The velocity of sound in compact bone is 3000~3500 m / s.

[0042] Furthermore, the attenuation coefficient is calculated according to the following formula: In the formula, f is the ultrasonic operating frequency (MHz). The attenuation coefficient of a point r on the outer surface of the target region at frequency f; The reference attenuation factor is 1.2 dB / cm / MHz. 1.5 The first item Dominant fluid absorption, second term Characterize solid-state framework scattering.

[0043] Furthermore, the phase distribution on the outer surface of the target region Specifically, it is obtained through the following method: First, the preset target point T is set as a single-pole virtual sound source point, and its sound pressure expression can be simplified to: ,in For source strength, For the Dirac function, The coordinates of the preset target point T are given. Then, finite element analysis is used to simulate the reverse propagation of ultrasound waves from the preset target point T, passing through the brain parenchyma, skull, and superficial soft tissue in sequence, and finally reaching the outer surface of the target area of ​​the skull. The steady-state sound field. Specifically, first, the generated sound field includes... , and The individualized acoustic parameter field and the individualized three-dimensional geometric model of the skull were imported into the finite element analysis software COMSOL Multiphysics to ensure that the three-dimensional coordinates of the model and the preset target point T were accurately aligned in the same coordinate system. Average acoustic parameters were assigned to the soft tissue and brain parenchyma, such as the density of the soft tissue being 1500 kg / m³. 3 The speed of sound is 1540 m / s, and the attenuation coefficient is 0.5 dB / cm / MHz; the density of brain parenchyma is 1030 kg / m³. 3 The sound velocity is 1560 m / s, and the attenuation coefficient is 0.7 dB / cm / MHz. Adaptive mesh generation is then performed using a free tetrahedral mesh, covering the skull and the outer surface of the target area. The minimum unit size is set to 0.1 mm, and the maximum unit size for brain parenchyma and soft tissue regions is set to 1 mm; and the outer surface of the target area of ​​the skull where the sound speed changes drastically is also considered. Local encryption is applied to the vicinity. Then, the Generalized Minimal Residual (GMRES) method is used to iteratively solve the steady-state Helmholtz equations: In the formula, For the Laplace operator, For complex sound pressure, For complex wave number, i is the imaginary unit. For the sound source term. Set the convergence threshold to... By iteratively solving the above steady-state Helmholtz equation, it is ensured that the iterative results converge to a stable state. Therefore, after starting the simulation, the finite element analysis software COMSOL Multiphysics simulates the sound wave propagating backward from the virtual point sound source (preset target point T), passing through the brain parenchyma, skull, and soft tissue in sequence, and finally reaching the outer surface of the target area of ​​the skull. The steady-state sound field. This process is mathematically equivalent to the backpropagation calculation in the time reversal principle. After the simulation is completed, the outer surface of the target region is extracted. Complex sound pressure at all computational nodes This allows us to obtain the complete complex acoustic field distribution of the reverse-propagating ultrasound waves on the outer surface of the target area of ​​the skull, which includes amplitude information. and phase information Phase information This refers to the phase distribution on the outer surface of the target region. It can be obtained from the following formula: In the formula, This represents the phase angle (principal value) when taken as a complex number. This phase distribution... This refers to the ideal wavefront phase distribution required to accurately focus ultrasound waves at a preset target point T.

[0044] S3. Joint Design of Holographic Acoustic Phase Plates: The thickness distribution of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 is jointly designed so that the phase distribution generated by the exit surface 31 of the correction device described in this invention is equal to the ideal wavefront phase distribution. This step aims to design two cascaded holographic acoustic phase plates that can modulate the uniform ultrasonic wavefront emitted by the planar ultrasonic transducer, ultimately generating the ideal wavefront phase distribution calculated in step S2 at the exit surface 31 of the correction device. .

[0045] Specifically, the correction device is modeled as a cascaded system comprising three regions: a first holographic acoustic phase plate 2, a liquid layer formed by acoustic coupling liquid 4, and a second holographic acoustic phase plate 3. The wavefront of the incident surface 21 (i.e., the ultrasonic transducer side) is defined as a plane wave, and its phase... This is a constant (usually set to zero reference). The phase modulation distribution of the first holographic acoustic phase plate 2 needs to be found. Phase modulation distribution of the second holographic acoustic phase plate 3 This makes the total transmission phase function satisfy: In the formula, The wave number in the acoustically coupled liquid 4. , The velocity of sound in the acoustically coupled liquid 4. The thickness of the liquid layer formed by the acoustic coupling liquid 4. For the original phase difference The continuous, physically realizable phase distribution obtained after phase unrolling typically maps to [0, 2π) or a continuous interval. This allows us to obtain the total phase modulation required at point r on the exit surface 31 of the correction device. for: In the formula, The initial phase of the incident wave, Let n be the phase winding term, and n be the adjustment coefficient. Since the phase has 2π periodic equivalence, the actual physical modulation amount only needs to be within the principal value range of [0, 2π).

[0046] Based on the additional phase delay introduced when ultrasound passes through two holographic acoustic phase plates Thickness distribution of the two holographic acoustic phase plates and The conversion formula between them is as follows: For any coordinate point r on the holographic surface of the holographic acoustic phase plate (i.e., the first holographic surface 22 or the second holographic surface 32), the phase delay of the sound wave caused by its concave and convex structure is... With thickness satisfy: In the formula, The labels are used to distinguish the two holographic acoustic phase plates; For the acoustic wave phase delay of the j-th holographic acoustic phase plate, and These are the acoustic wave phase delays of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3, respectively. The wavelength of the acoustic wave in the acoustic coupling liquid 4 at the ultrasonic working frequency; Let be the acoustic refractive index of the j-th holographic acoustic phase plate. and The acoustic refractive indices of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 are respectively. The acoustic refractive index of the acoustic coupling liquid 4; The thickness distribution at point r on the j-th holographic acoustic phase plate. and The thickness distributions at point r on the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 are respectively.

[0047] To reduce fabrication difficulty and ensure the structural strength of the holographic acoustic phase plates, a constraint is applied, and a fixed value Q is set so that the thickness distribution at any coordinate point r on the holographic surface of the two holographic acoustic phase plates satisfies... Solving the system of equations and combining it with the least squares phase expansion method eliminates the entanglement phenomenon of the original phase difference, resulting in a continuous and physically realizable thickness distribution. and .

[0048] Furthermore, the fixed value Q is the sum of the thicknesses of the two holographic acoustic phase plates. The principle for selecting the fixed value Q is Q≥λ / 2, where λ is the wavelength of the sound wave in the acoustic coupling liquid 4, and it is adjusted according to the material structure strength of the two holographic acoustic phase plates.

[0049] Subsequently, to ensure that the design of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 meets the phase modulation requirements, simulation verification was performed. A cascaded system model of "ultrasonic transducer → first holographic acoustic phase plate 2 → liquid coupling layer 4 → second holographic acoustic phase plate 3" was established in the software COMSOL Multiphysics, and the obtained thickness distribution was imported. and Assign corresponding acoustic parameters to each component; set the incident wave as a plane wave (phase=0), run steady-state sound field simulation, and extract the phase distribution of the exit surface 31 of the correction device. ;calculate Phase distribution of the ideal wavefront The standard deviation of the phase difference is required to be ≤5°. If this is not met, the value of the fixed value Q or the phase expansion parameter is adjusted until the requirement is met.

[0050] S4. Device fabrication and integration: Utilizing the thickness distribution data of the first holographic acoustic phase plate 2 and the second holographic acoustic phase plate 3 obtained in step S3. and High-precision CNC machining or 3D printing technology is used to obtain the thickness distribution data obtained in step S3. and Using a high-precision CNC machine tool or a photopolymer 3D printer, and employing acoustically stable and biocompatible polymer materials (such as polymethyl methacrylate PMMA), a first holographic acoustic phase plate 2 and a second holographic acoustic phase plate 3 are manufactured. The vertical resolution of the processed surface must be better than 1 / 10 of the working wavelength, and the horizontal resolution must meet the holographic surface feature size requirements. The two holographic acoustic phase plates are arranged with their holographic surfaces facing each other—that is, the first holographic surface 22 of the first holographic acoustic phase plate 2 and the second holographic surface 32 of the second holographic acoustic phase plate 3 are opposite each other—and precisely installed inside the housing 1 using positioning clips, ensuring that the distance between them meets the design value. The acoustic coupling liquid 4 (which can be degassed deionized water or medical ultrasound coupling agent) is injected through the injection hole 11, and air bubbles are completely removed by vacuum or centrifugation. Finally, the injection hole 11 is sealed to obtain the correction device described in this invention.

[0051] In other embodiments, to address the issue of ultrasonic intensity attenuation caused by incident angle mismatch, a normal alignment calibration step is performed before integrating the ultrasonic transducer probe into the correction device. Specifically, after step S4, a normal alignment calibration step is included: First, the three-dimensional point cloud data of the outer surface of the target area of ​​the skull to which the correction device's exit surface 31 is expected to fit is extracted. This data originates from the reconstructed three-dimensional geometric model of the skull in step S1 and is located under an established unified spatial reference. Then, the average normal vector of the outer surface of the target area is calculated. (Or use a weighted average normal for areas with large curvature): In the formula, Here, S is the normalized average normal vector, and S is the set of three-dimensional point clouds of the outer surface of the target area of ​​the skull of the target object to be fitted by the exit surface 31 of the correction device. Let be the local normal vector of the i-th grid point or voxel. This is the weighting coefficient for the i-th grid point or voxel, which is either the sound intensity contribution weight or a confidence level related to curvature. Then, using the rigid transformation matrix M established in step S1, the average normal vector is... Transform to the transducer local coordinate system to obtain the target attitude vector. : In the formula, R is the rotation matrix from the fused coordinate system (i.e., the unified spatial reference) to the transducer's local coordinate system. The rotation matrix R is obtained by extracting the rotation component (ignoring the translation component) from the rigid transformation matrix M. Specifically, if... Then R is the required rotation matrix, and t is the translation vector. The transducer's local coordinate system is defined as follows: with the geometric center of the ultrasonic transducer as the origin, the normal direction of the ultrasonic transducer's emitting surface (i.e., the acoustic axis direction) as the Z-axis, and the preset direction within the plane where the probe marker point is located as the X-axis, the Y-axis is determined according to the right-hand rule. Through the above transformation, the desired alignment direction of the correction device is mapped to the transducer's own coordinate system for subsequent phase calculations or mechanical attitude adjustments. Subsequently, the mounting bracket of the ultrasonic transducer probe (which has multi-degree-of-freedom fine-tuning capabilities) is adjusted so that the probe's acoustic axis direction (i.e., the Z-axis of the transducer's local coordinate system) aligns with the calculated target attitude vector. Strictly collinear and in opposite directions (i.e., the probe's emission surface is perpendicular to the average cross-section of the skull, and the ultrasound waves are directed at the skull at an almost perpendicular angle).

[0052] This operation ensures that the ultrasound waves pass through the skull interface at a near-vertical angle, minimizing mode conversion (longitudinal wave to transverse wave) and refraction and reflection losses caused by oblique incidence, and ensuring that the preset phase compensation effect is fully reproduced in actual propagation.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A personalized transcranial ultrasound focusing correction device, characterized in that, include: A combined holographic acoustic phase plate is used to modulate the phase of the ultrasonic wavefront emitted by an ultrasonic transducer. as well as A non-fully enclosed housing (1) is used to fix and protect the combined holographic acoustic phase plate; The combined holographic acoustic phase plate includes a first holographic acoustic phase plate (2) and a second holographic acoustic phase plate (3) arranged in parallel along the sound wave propagation axis. The first holographic acoustic phase plate (2) has an incident surface (21) facing the ultrasonic transducer and a first holographic surface (22) opposite to it. The incident surface (21) is a smooth plane or a smooth arc surface, and the first holographic surface (22) is an uneven surface with a specific uneven distribution processed according to individualized calculation data. The second holographic acoustic phase plate (3) has an exit surface (31) facing the outer surface of the skull of the target object and a second holographic surface (32) arranged opposite to it. The exit surface (31) is a smooth plane, and the second holographic surface (32) is an uneven surface with a specific uneven distribution processed according to individualized calculation data. The first holographic surface (22) and the second holographic surface (32) are arranged opposite each other, and a liquid layer filled with acoustic coupling liquid (4) is formed between them.

2. The personalized transcranial ultrasound focusing correction device according to claim 1, characterized in that, The first holographic acoustic phase plate (2) is made of a material with an acoustic impedance similar to that of the ultrasonic transducer matching layer; the second holographic acoustic phase plate (3) is made of a material with an acoustic impedance similar to that of the soft tissue of the head.

3. The personalized transcranial ultrasound focusing correction device according to claim 1, characterized in that, The first holographic surface (22) and the second holographic surface (32) are both composed of multiple three-dimensional structural units arranged closely together. Each three-dimensional structural unit has the same thickness at all points, and the thicknesses of different three-dimensional structural units are different.

4. The personalized transcranial ultrasound focusing correction device according to claim 1, characterized in that, The first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3) are fixed at a distance by the positioning buckle of the outer shell (1).

5. A design method for a personalized transcranial ultrasound focusing correction device according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Obtain individualized anatomical data and pre-set target location data: Obtain three-dimensional geometric model data of the target object's skull through medical imaging; Under the same three-dimensional coordinate system, the position coordinates of the preset target point are determined, and the expected placement and orientation of the ultrasonic transducer are determined. At the same time, a coordinate system fusion method based on stereoscopic frame and marker point registration is adopted to establish a unified spatial reference from image space to physical space, so as to achieve a one-to-one correspondence between the ultrasonic transducer and the preset target point in space. S2. Calculate the target wavefront phase distribution: Based on the individualized anatomical data and preset target location data obtained in step S1, construct a non-uniform medium acoustic model, and use the principle of sound field reverse propagation to solve the ideal wavefront phase distribution required to focus the ultrasound at the preset target point T. S3. Joint design of holographic acoustic phase plates: Jointly design the thickness distribution of the first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3) so that the phase distribution generated by the exit surface (31) of the correction device is equal to the ideal wavefront phase distribution; S4. Device processing and integration assembly: The first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3) are processed and manufactured using the thickness distribution data of the first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3), and installed in the housing (1) by positioning buckles. After injecting acoustic coupling liquid (4) through the injection hole (11), the device is sealed to obtain the correction device.

6. The design method according to claim 5, characterized in that, The coordinate system fusion method based on the registration of stereoscopic frames and marker points specifically includes the following sub-steps: (a1) Three non-collinear high-density metal head mold markers are placed on the scalp of the target object to establish a spatial reference base for the skull; wherein the three head mold markers form an equilateral triangle or an isosceles triangle, the distance between any two head mold markers is greater than or equal to 3cm, and the diameter of the head mold markers is 3-5mm. (a2) Set three non-collinear metal probe markers on the fixed support of the ultrasonic transducer, and the plane where the three probe markers are located is perpendicular to the acoustic axis of the ultrasonic transducer to establish a spatial reference for the transducer. (a3) Simultaneously acquire image data of skull structure, preset target point T, head mold marker point and probe marker point in the same medical image, and extract the three-dimensional coordinates of skull structure contour, preset target point T, head mold marker point and probe marker point in image space; wherein, the head mold marker point and probe marker point are automatically identified by threshold segmentation based on the high brightness characteristics of their high-density metallic material in CT images; the preset target point T is manually calibrated in the image; (a4) Measure the three-dimensional coordinates of the head model marker point and the probe marker point in the physical space using an optical navigation system or a mechanical positioning arm. Use the corresponding three-dimensional coordinates of the head model marker point and the probe marker point in the image space and the physical space as input. Calculate the rigid transformation matrix M from the virtual image space to the real physical space using a point set registration algorithm as a unified spatial reference. The point set registration algorithm uses singular value decomposition.

7. The design method according to claim 5, characterized in that, Step S2 specifically includes: First, based on the unified spatial reference established in step S1, the outer surface of the target area to which the corrective device's output surface (31) is expected to fit is mapped to the three-dimensional geometric model of the skull. The CT gray value of the outer surface of the target area is extracted, the porosity of the corresponding position is calculated based on the gray value, and the density, sound velocity and attenuation coefficient of the corresponding position are calculated based on the porosity. Then, the preset target point T is set as a single-pole virtual sound source point, and the finite element analysis is used to simulate the ultrasonic wave propagating backward from the preset target point T to the outer surface of the target area, and the phase distribution of the outer surface of the target area is obtained as the desired ideal wavefront phase distribution.

8. The design method according to claim 7, characterized in that, The porosity is calculated according to the following formula: In the formula, r is a point on the outer surface of the target region. Let r be the porosity at point r on the outer surface of the target region. The CT gray value at point r is... The CT grayscale value of water. The CT grayscale value of compact bone; The density is calculated according to the following formula: In the formula, Let r be the density at point r on the outer surface of the target region. The density of water, The density of compact bone; The speed of sound is calculated according to the following formula: In the formula, Let r be the speed of sound at point r on the outer surface of the target region. The speed of sound in water. The speed of sound in compact bone; The attenuation coefficient is calculated according to the following formula: In the formula, f is the ultrasonic operating frequency. Let r be the attenuation coefficient of a point r on the outer surface of the target region at frequency f. This is the baseline attenuation coefficient.

9. The design method according to claim 5, characterized in that, The thickness distribution of the first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3) is obtained through the following method: The total phase modulation amount required at point r on the exit surface (31) of the correction device for: In the formula, The ideal wavefront phase distribution at point r on the outer surface of the target region. The initial phase of the incident wave, Here, n is the phase winding term, and n is the adjustment coefficient. For any coordinate point r on the holographic surface of the holographic acoustic phase plate, the acoustic wave phase delay With thickness satisfy: In the formula, To distinguish the labels of the two holographic acoustic phase plates, For the acoustic wave phase delay of the j-th holographic acoustic phase plate, The wavelength of the acoustic wave in the acoustic coupling liquid (4) at the ultrasonic working frequency. Let be the acoustic refractive index of the j-th holographic acoustic phase plate. Let be the acoustic refractive index of the acoustic coupling liquid (4). Let r be the thickness distribution at point r on the j-th holographic acoustic phase plate; Set a fixed value Q such that the thickness distribution at any coordinate point r on the holographic surface of the two holographic acoustic phase plates satisfies Solving the system of equations and combining it with the least squares phase expansion method yields a continuous thickness distribution. and ,in and The thickness distributions at point r on the first holographic acoustic phase plate (2) and the second holographic acoustic phase plate (3) are respectively. The fixed value Q is selected according to the principle that Q≥λ / 2.

10. The design method according to claim 5, characterized in that, Following step S4, a normal alignment calibration step is also included: Extract the three-dimensional point cloud data of the outer surface of the target area to be fitted by the exit surface (31) of the correction device, and calculate the average normal vector: In the formula, S is the normalized average normal vector, and S is the three-dimensional point cloud set of the outer surface of the target area to be fitted by the exit surface (31) of the correction device. Let be the local normal vector of the i-th grid point or voxel. The weight coefficient for the i-th grid point or voxel; Using the rigid transformation matrix M to transform the average normal vector Transform to the transducer local coordinate system to obtain the target attitude vector. : In the formula, R is the rotation matrix, which is obtained by extracting the rotation components from the rigid transformation matrix M; Adjust the mounting bracket of the ultrasonic transducer probe so that the acoustic axis direction is aligned with the target attitude vector. Strictly collinear and opposite in direction.

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