Non-invasive cervical electrical stimulation electrode placement method based on individual cervical physiological curvature

Abstract

The application discloses a non-invasive cervical electrical stimulation electrode arrangement method based on individual cervical physiological curvature. The method obtains individual cervical segment information, neck surface information, region of interest information and electric field calculation data; a local anatomical plane is constructed according to a target cervical spinal cord segment, and intersects with the individual surface to generate a surface contour, and then candidate electrode points are obtained according to an arc length rule; after attachment screening, an electrode combination is constructed, electric field distribution or time interference modulation distribution is calculated, and whether the electric field intensity, modulation intensity or electric field vector in the region of interest meets the preset electric field target condition is determined to determine the recommended layout. The application can improve the spatial correspondence of the electrode layout and the target cervical spinal cord segment, and provide an individualized, repeatable and convenient cervical electrical stimulation electrode arrangement determination method.

Description

Technical Field

[0001] This invention belongs to the field of brain-computer interface technology, and further relates to a non-invasive method for deploying cervical electrical stimulation electrodes based on the physiological curvature of an individual's cervical spine in the field of medical data processing technology. This invention can be used in scenarios such as cervical AC stimulation, transcutaneous spinal cord stimulation, and four-electrode dual-channel time-interference stimulation. The placement of the cervical electrical stimulation electrodes is determined based on the subject's cervical spine segmental pathways, the surface attachment areas, and the electric field distribution of the region of interest. Background Technology

[0002] The cervical spinal cord and its surrounding nerve structures are closely related to sensory conduction, pain modulation, motor function, and autonomic nervous activity. Non-invasive electrical stimulation of the neck region via surface electrodes is a primary technique for neuromodulation, pain intervention, and rehabilitation. In cervical electrical stimulation, electrode placement directly affects the conduction path of the current after it enters the body, further influencing the electric field strength, stimulation range, and spatial selectivity within the cervical spinal cord target area. Especially for temporal interference stimulation, the intensity, direction, angle, and spatial overlap of the electric fields from two channels within the region of interest affect the final low-frequency modulation envelope. Therefore, electrode placement is not simply a matter of external patching, but a crucial factor determining whether stimulation can effectively act on the target cervical spinal cord segment. Common methods include percutaneous spinal cord stimulation (PCS), cervical alternating current stimulation (AC), cervical direct current stimulation (DC), and temporal interference stimulation. Current electrode placement for cervical electrical stimulation or PCS often employs fixed height, fixed horizontal planes, external surface landmarks, or operator experience. The actual human cervical spine exhibits individualized physiological curvature; the length, degree of lordosis, vertebral alignment, neck surface morphology, and head-neck connection structures all vary among different subjects. Therefore, using a fixed horizontal height or empirical surface positioning can easily lead to inconsistencies between the electrode placement and the actual cervical spine segments, thus affecting the electric field distribution and stimulation selectivity in the target area. Electrode placement schemes based on surface landmarks or human experience, electrode candidate point generation schemes based on fixed horizontal levels, electrode combination evaluation schemes based on finite element electric field simulation, and multi-electrode optimization schemes for the head or other body parts are all proposed. While these schemes can achieve basic electrode placement or electric field calculations, the candidate electrode positions are often still determined by human experience, template positions, or fixed horizontal levels, failing to fully consider the individual physiological curvature of the cervical spine when generating candidate electrode points.

[0003] The Institute of Psychology, Chinese Academy of Sciences, disclosed a closed-loop percutaneous spinal cord stimulation analgesia system and method based on physiological feedback in its patent application, "A Closed-Loop Percutaneous Spinal Cord Stimulation Analgesia System and Method Based on Physiological Feedback" (application date 2026-03-20, application number 202610348329.X, publication number CN121971802 A). The system includes an electrode patch, a physiological signal acquisition module, a stimulator, and a control module. At least one pair of electrode units are integrated on the flexible substrate of the electrode patch for attachment to the corresponding spinal cord segment on the subject's body surface. The control module assesses the subject's pain state based on the acquired physiological signals and generates control commands to perform closed-loop adjustment of the stimulator's output state. In the section related to electrode layout, the method discloses multi-site electrode patches and their electrode unit arrangements, such as different electrode units like A1-A6, B1-B6, C1-C6, D1-D6, and E1-E6. Stimulation of one or more spinal cord segments can be achieved by selecting two electrode units from C1-C6, two electrode units from both sides of the spinal cord, or combinations of multiple electrode units. However, this technical solution still has shortcomings. Although it discloses setting multiple electrode units on flexible electrode patches and achieving percutaneous stimulation of one or more spinal cord segments by selecting different combinations of electrode units, its electrode layout is based on preset multi-site patches and electrode unit combinations, assuming that the electrode unit arrangement on the patch corresponds to the spinal cord segment projection area on the body surface. For cervical percutaneous stimulation, different subjects have significant differences in cervical physiological curvature, segment tilt direction, neck length, head and neck posture, and body surface morphology. The same patch number or the same body surface height does not necessarily correspond to the same actual cervical segment. Therefore, relying solely on preset patch arrangements or manually selected electrode unit combinations can easily lead to inconsistencies between the actual electrode action level and the target cervical spinal cord segment. This results in stimulation hotspots deviating from the region of interest, with adjacent non-target segments or superficial tissues receiving excessive stimulation, thus affecting stimulation focus and the reliability of electrode combination evaluation. The reason for this problem lies in the fact that this method focuses on closed-loop regulation of stimulation parameters and electrode unit activation states, without establishing rules for determining candidate electrode levels based on the spatial correspondence between individual cervical spine segmental pathways and neck surface morphology.

[0004] In summary, the existing technology has the following shortcomings:

[0005] First, the fixed Z-axis horizontal section is inconsistent with the actual cervical segment plane, which may cause the candidate electrode point of the same nominal segment to deviate from the actual local anatomical plane of the cervical spine, resulting in the actual action plane of the electrode shifting upward, downward or deviating towards the adjacent non-target segment.

[0006] Secondly, the electrode placement relies on surface landmarks or operator experience, resulting in poor repeatability. This makes it difficult to maintain a consistent electrode placement among different operators or subjects, thus affecting the repeatability and comparability of the electric field results.

[0007] Third, differences in neck morphology, head and neck posture, and attachable areas can lead to the problem that candidate electrode points cannot be attached or deviate from the actual target segment.

[0008] Fourth, judging the quality of the layout solely based on geometric location or target area intensity may lead to the selection of electrode combinations with high overall field strength but relatively high stimulation in non-target areas, making it difficult to distinguish between the issues of "target area enhancement" and "overall diffusion".

[0009] Fifth, for multi-channel stimulation modes such as time-interference stimulation, existing methods often lack the process of further calculating the time-interference modulation distribution based on the electric field distribution of different channels and determining the recommended electrode layout accordingly. This makes it difficult for the recommended electrode layout to fully reflect the electric field requirements of the target cervical spinal cord region. Summary of the Invention

[0010] The purpose of this invention is to address the shortcomings of existing technologies by proposing a non-invasive cervical electrical stimulation electrode placement method based on the individual's cervical spine physiological curvature. This method aims to solve three core problems in existing cervical electrical stimulation electrode placement: First, fixed horizontal planes or empirical placement are difficult to adapt to individual cervical spine physiological curvature, resulting in inaccurate correspondence between candidate electrode planes and actual cervical spine segments; Second, candidate electrode points mainly rely on operator experience or fixed templates, lacking a regularized and repeatable candidate electrode point generation method jointly determined by individual cervical spine segments and body surface contours; Third, existing electrode placement methods typically lack a placement determination mechanism that combines individualized candidate electrode points, preset stimulation modes, and the electric field requirements of the region of interest, making it difficult to ensure that the recommended electrode placement better serves the effective stimulation and concentrated electric field effect of the target cervical spinal cord region while meeting electrode adhesion and stimulation mode requirements.

[0011] The technical approach to achieving the objective of this invention is to construct a local anatomical plane that varies with the physiological curvature of the individual cervical spine, and then combine this plane with the individual's neck surface contour to generate candidate electrode points. This provides an individualized electrode layout basis for addressing the aforementioned segmental mismatch problem. Because this invention employs a candidate electrode level determination technique based on the individual's local anatomical plane of the cervical spine, the candidate electrode level is no longer determined by a globally fixed Z-axis horizontal plane, but rather by the actual segmental course reflected by the subject's own C1-C7 cervical spine segment reference points, vertebral body centers, intervertebral disc centers, or cervical spinal cord centerlines. The key feature of this technique is that the center position and normal direction of the local anatomical plane are derived from the individual's cervical spine segmental spatial information, and can change with the subject's cervical lordosis, segmental tilt direction, and head and neck posture. Therefore, this technique overcomes the shortcomings of existing fixed horizontal planes that are inconsistent with the actual cervical spine segment planes, making the candidate electrode level closer to the actual anatomical location of the target cervical spine segment. Because this invention further employs a candidate electrode point generation technique that combines local anatomical planes with the individual's neck surface contour, candidate electrode points are not estimated by the operator based on experience with surface landmarks, nor are they directly given by a uniform template. Instead, they are generated along the individual's neck surface contour according to arc length rules after the individual's neck surface contour is cut from the local anatomical plane. The key feature of this technique is that candidate electrode points are simultaneously constrained by the individual's cervical spine segment level and individual surface morphology, possessing both a clear anatomical correspondence and repeatable geometric generation rules. Therefore, this technique overcomes the shortcomings of existing electrode point placement methods, such as reliance on operator experience, poor repeatability, and inaccurate correspondence between candidate electrode points and the individual's attachable surface area, improving the individual adaptability and reproducibility of candidate electrode point generation. Furthermore, this invention also screens candidate electrode points according to electrode attachment requirements and layout rules, constructs candidate electrode combinations according to preset stimulation modes, and further calculates the electric field distribution corresponding to the candidate electrode combinations. When the preset stimulation mode is time-interference stimulation, the time-interference modulation distribution is also calculated based on the electric field distribution of different channels and stimulation frequency parameters. The key feature of this technology is that the recommended electrode layout is not simply determined based on the geometric location of candidate electrode points. Instead, it is determined by considering whether the electric field distribution or temporal interference modulation distribution within the region of interest meets the preset electric field target conditions, while also satisfying the individual's cervical segment correspondence, surface adhesion constraints, and stimulation pattern requirements. Therefore, this technology can provide an electrode layout scheme for cervical electrical stimulation that simultaneously meets individual anatomical structure, surface adhesion requirements, and the electric field requirements of the region of interest.

[0012] To achieve the above objectives, the specific implementation steps of the present invention include the following:

[0013] Step 1: Obtain individual cervical spine segment information, neck surface information, region of interest information, and data required for electric field calculation;

[0014] Step 2: Construct the local anatomical plane of the corresponding cervical vertebral segment based on the segmental reference center and the local axial direction;

[0015] Step 3: Generate candidate electrode points according to the preset arc length rules;

[0016] Step 4: Screen candidate electrode points according to electrode attachment requirements and layout rules;

[0017] Step 5: Construct candidate electrode combinations according to the preset stimulation mode, and calculate the electric field distribution or time interference modulation distribution;

[0018] Step 6: Determine the recommended electrode layout from the candidate electrode combinations;

[0019] Step 7: Output the candidate electrode point number, cervical segment to which it belongs, three-dimensional spatial coordinates, left and right side positions, upper and lower layer positions and channel allocation relationship of each electrode point in the recommended electrode layout, and generate a report containing recommended electrode layout parameters, candidate electrode point information, electric field calculation results and visualization results.

[0020] Furthermore, the steps for obtaining the individual cervical spine segment information of the subject are as follows:

[0021] The first step is to obtain image annotations, segmentation labels, centerline data, or model data for the C1-C7 cervical vertebrae of the subjects;

[0022] The second step is to extract at least one segmental reference point from the image annotation, segmentation label, centerline data or model data, including the vertebral body center, intervertebral disc center, cervical spinal cord centerline point or spinal canal centerline point;

[0023] The third step is to convert or record the segment reference points in a spatial coordinate system consistent with the neck surface information and electric field calculation data to form cervical segment information for constructing local anatomical planes.

[0024] Furthermore, the steps for obtaining the neck surface information are as follows:

[0025] The first step is to read the data of the subject's neck skin surface, head and neck outer surface mesh, 3D point cloud or attachable surface area; and extract the neck surface area corresponding to the target cervical vertebra segment.

[0026] The second step is to convert or record the neck surface area in a spatial coordinate system consistent with the cervical vertebral segment information to form individual neck surface information that is calculated by intersecting with the local anatomical plane.

[0027] Furthermore, the steps for obtaining the region of interest information are as follows:

[0028] The first step is to read the spatial extent of the region of interest, the target cervical spinal cord segment identifier, or the pre-defined target area;

[0029] The second step is to determine whether the region of interest, the target cervical spinal cord segment identifier, or the preset target area definition is in the same spatial coordinate system as the electric field calculation data or has a spatial correspondence. If so, proceed to the fourth step; otherwise, proceed to the third step.

[0030] The third step is to perform spatial transformation, registration, mapping, interpolation, or nearest neighbor correspondence processing on the region of interest when the region of interest, the target cervical spinal cord segment identifier, or the preset target area definition is not in the same spatial coordinate system as the electric field calculation data or there is no spatial correspondence. This will establish a spatial correspondence between the region of interest and the electric field calculation data before proceeding to the fifth step.

[0031] The fourth step is to directly read the correspondence between the region of interest and the electric field calculation data when they are in the same spatial coordinate system or have a spatial correspondence.

[0032] The fifth step involves determining, based on the spatial correspondence between the region of interest and the electric field calculation data, the grid nodes, grid cells, or sampling points falling within the region of interest in the electric field calculation data, thus forming a set of calculation points for the region of interest.

[0033] Furthermore, the segment reference center and local axial direction are obtained through the following steps:

[0034] The first step is to determine the target cervical segment corresponding to the target stimulation area based on the spatial location of the region of interest, the target cervical spinal cord segment identifier, or the pre-defined target area.

[0035] The second step involves using the target cervical vertebrae as the center, determining one or more cervical vertebrae to participate in the generation of candidate electrode points based on the preset range of adjacent segments, electrode size, stimulation mode, and safety constraints, and determining the candidate electrode search range based on the spatial location of the determined cervical vertebrae.

[0036] The third step is to read one or more segmental reference points, such as the vertebral body center, intervertebral disc center, cervical spinal cord centerline point, or spinal canal centerline point, for each cervical vertebral segment involved in generating candidate electrode points.

[0037] The fourth step is to calculate the segmental reference center P0_k of the corresponding cervical vertebral segment based on the segmental reference point. The segmental reference center P0_k is determined by the midpoint of the center of the adjacent intervertebral disc above and below the segment, the center of the vertebral body, the center line point of the cervical spinal cord, the center line point of the spinal canal, or a combination thereof.

[0038] The fifth step involves calculating the local axial direction of the corresponding cervical vertebral segment based on one or more of the following: the direction of the line connecting the reference points of adjacent segments, the direction of the line connecting the centers of adjacent intervertebral discs, the direction of the line connecting the centers of adjacent vertebral bodies, the tangent vector of the cervical spinal cord centerline, or the tangent vector of the spinal canal centerline. The local axial direction is then normalized to obtain the local axial unit vector n_k.

[0039] Furthermore, the local anatomical plane of the cervical vertebral segment is constructed by the segment reference center P0_k and the local axial unit vector n_k, wherein the segment reference center P0_k is used as the plane reference point of the local anatomical plane, and the local axial unit vector n_k is used as the normal vector of the local anatomical plane. The local anatomical plane allows the level of the candidate electrode point to be determined by the spatial information of the individual cervical spine segment, and to change with the physiological curvature of the individual cervical spine.

[0040] Furthermore, the step of generating candidate electrode points according to the preset arc length rule is as follows:

[0041] The first step is to represent the local anatomical plane as follows: And calculate the signed distances of each surface point, mesh node, or patch boundary point in the individual neck body surface or the outer surface of the head and neck model relative to the local anatomical plane;

[0042] The second step is to determine the body surface edges, body surface patches, or body surface points that intersect with the local anatomical plane based on the signed distance; for body surface edges located on both sides of the local anatomical plane, the intersection point of the body surface edge and the local anatomical plane is calculated by linear interpolation; and body surface points located within a preset distance threshold are selected as candidate contour points.

[0043] The third step is to connect the intersection points or candidate contour points according to spatial adjacency, contour continuity or arc length order to obtain the body surface contour formed after the individual's neck surface is cut out by the local anatomical plane.

[0044] The fourth step is to determine the center reference point or the middle candidate electrode point on the body surface contour.

[0045] Fifth step: Taking the rear center reference point or the middle candidate electrode point as the starting point, calculate the arc length distance along the body surface contour to the left and right respectively;

[0046] Step 6: Based on the preset arc length interval, electrode size, or number of candidate electrode points, sample sequentially on both sides of the body surface contour to generate multiple candidate electrode points;

[0047] Step 7: Record the cervical vertebral segment to which the candidate electrode point belongs, the candidate electrode point number, and determine the corresponding three-dimensional spatial coordinates.

[0048] Furthermore, the step of screening candidate electrode points according to electrode attachment requirements and layout rules is as follows:

[0049] The first step is to aggregate the candidate electrode points generated according to the preset arc length rules into a candidate electrode point set, and obtain the three-dimensional spatial coordinates, the cervical vertebra segment to which each candidate electrode point belongs, the candidate electrode point number, the body surface contour position to which it belongs, and the corresponding body surface area information for each candidate electrode point.

[0050] The second step is to determine the position of the candidate electrode points according to the preset attachable area: when a candidate electrode point is located outside the preset attachable area or within the preset exclusion area, the candidate electrode point is removed from the candidate electrode point set; the preset attachable area is determined by one or more of the following: neck surface label, body surface contour range, spatial coordinate range, attachable area boundary or exclusion area boundary.

[0051] The third step involves filtering the segment range of candidate electrode points based on the target segment location and the candidate electrode search range; reading the cervical segment to which the candidate electrode point belongs, the candidate electrode point number, and the position of the candidate electrode point on the corresponding body surface contour; determining whether the candidate electrode point belongs to one or more cervical segments involved in the generation of candidate electrode points; and determining whether the candidate electrode point is within the preset candidate electrode search range; if the candidate electrode point does not belong to the cervical segment involved in the generation of candidate electrode points, or is not within the preset candidate electrode search range, then the candidate electrode point is removed from the candidate electrode point set.

[0052] The fourth step is to determine the spacing between candidate electrode points based on the preset minimum electrode spacing: when the spacing between two candidate electrode points is less than the preset minimum electrode spacing, at least one candidate electrode point is eliminated, or the combination of candidate electrode points consisting of the two candidate electrode points is eliminated; the spacing is determined by the arc length of the candidate electrode point on the body surface contour, or by one or more of the Euclidean distance between the three-dimensional coordinates of the candidate electrode points and the geodesic distance of the body surface.

[0053] The fifth step involves combining and constraining the remaining candidate electrode points according to the preset stimulation mode and layout rules. The layout rules are preset based on the number of electrodes, the number of channels, electrode attachment requirements, and the stimulation mode, including one or more of the following: left-right distribution rules, upper-lower layer distribution rules, channel pairing rules, electrode number rules, or electrode spacing rules. Among them, the left-right distribution rules are determined based on the body surface contour position of the candidate electrode point relative to the posterior midline reference point or the middle candidate electrode point; the upper-lower layer distribution rules are determined based on the cervical vertebral segment to which the candidate electrode point belongs or the upper-lower layer number; the channel pairing rules are determined based on the number of channels, electrode polarity, and channel composition relationship in the preset stimulation mode; and the electrode spacing rules are determined based on the arc distance, Euclidean distance, or geodesic distance between candidate electrode points.

[0054] Furthermore, the step of constructing candidate electrode combinations according to a preset stimulation pattern and calculating the electric field distribution or time-interference modulation distribution includes:

[0055] The first step is to read the candidate electrode points that have been screened and retained, and to use the candidate electrode points as the set of candidate electrode points after screening. Based on the preset stimulation mode, the number of electrodes, number of channels, electrode polarity, current amplitude and stimulation frequency parameters required for the candidate electrode combination are determined.

[0056] The second step is to select candidate electrode points from the set of candidate electrode points after screening, according to the number of electrodes, the number of channels, the electrode polarity and the preset combination rules, and to define the selected candidate electrode points and their corresponding channel allocation relationship, electrode polarity and current parameters as a candidate electrode combination.

[0057] The third step is to perform leadfield pre-calculation on the candidate electrode points in the selected candidate electrode point set to obtain the unit current electric field distribution corresponding to each candidate electrode point.

[0058] The fourth step is to linearly superimpose the leadfield, electrode polarity, current amplitude and channel allocation relationship of each candidate electrode point in the candidate electrode combination to obtain the electric field distribution under the corresponding candidate electrode combination.

[0059] Fifth step: When the preset stimulation mode is time interference stimulation, the time interference modulation distribution under the corresponding candidate electrode combination is further calculated based on the electric field distribution and stimulation frequency parameters corresponding to different channels.

[0060] Furthermore, the step of determining the recommended electrode layout from the candidate electrode combinations is as follows:

[0061] The first step is to determine the set of calculation points for the region of interest based on the spatial correspondence between the region of interest information and the electric field calculation data;

[0062] The second step is to extract the electric field intensity value, time interference modulation intensity value, or electric field vector value corresponding to the candidate electrode combination within the set of calculation points in the region of interest.

[0063] The third step is to determine whether the candidate electrode combination meets the preset electric field target condition based on the electric field intensity value, time interference modulation intensity value, or electric field vector value.

[0064] The fourth step is to determine the candidate electrode combinations that meet the preset electric field target conditions as recommended electrode layouts; when there are multiple candidate electrode combinations that meet the preset electric field target conditions, one or more recommended electrode layouts are determined from them according to preset selection rules.

[0065] Compared with the prior art, the present invention has the following advantages:

[0066] First, because the present invention uses a technique to construct a local anatomical plane based on the spatial information of individual cervical vertebrae segments, the plane where the candidate electrode point is located no longer depends on a preset fixed reference plane or a uniform horizontal plane, but is determined by the spatial information of the individual cervical vertebrae segments and is adjusted according to the individual's cervical physiological curvature, segment tilt direction and head and neck posture changes. This overcomes the defect that the existing fixed reference plane is inconsistent with the actual cervical vertebrae segment plane, thereby improving the spatial correspondence accuracy between the candidate electrode point and the target cervical vertebrae segment.

[0067] Secondly, because this invention uses the intersection of a local anatomical plane and the surface of an individual's neck or head and neck model to obtain the surface contour, and generates candidate electrode points along the surface contour according to a preset arc length rule, it overcomes the shortcomings of existing technologies where electrode point placement mainly relies on surface landmarks, operator experience, or uniform templates, resulting in poor repeatability. This ensures that the generation of candidate electrode points has clear anatomical basis and geometric rules. Furthermore, this invention further combines electrode size, preset attachable areas, preset exclusion areas, minimum electrode spacing, left-right distribution rules, upper-lower layer distribution rules, and channel pairing rules to screen candidate electrode points or combinations of candidate electrode points. This ensures that the candidate electrode points not only correspond to the target cervical vertebral segments but also better meet the actual requirements for neck surface attachment. Attached Figure Description

[0068] Figure 1 This is a flowchart of the present invention;

[0069] Figure 2 This is a schematic diagram illustrating the difference between the fixed Z horizontal plane and the curve local anatomical plane of the present invention;

[0070] Figure 3 This is a schematic diagram illustrating the generation of candidate electrode points based on local anatomical planes and the contour of an individual's neck surface according to the present invention. Detailed Implementation

[0071] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or modifications made to the construction method of the local anatomical plane, the number of candidate electrode points, the selection conditions of candidate electrode points, the electric field evaluation index, or the stimulation mode under the technical concept disclosed in the present invention should be included within the scope of protection of the present invention.

[0072] The embodiments of the present invention are illustrated using the cervical electrical stimulation electrode layout of the target segment of the cervical spinal cord as an application scenario. The preset stimulation mode may include single-channel electrical stimulation, multi-channel electrical stimulation, or time-interference stimulation; in one specific embodiment, the preset stimulation mode may be four-electrode dual-channel time-interference stimulation.

[0073] Specifically, the target stimulation region can be set as a region of interest within a specific cervical spinal cord segment, such as the dorsal region of the C4 segment, the posterior horn region, or other cervical spinal cord regions of interest that require modulation. The region of interest can be determined by its spatial extent, the target cervical spinal cord segment identifier, or a preset target area definition, and a spatial correspondence is established with the electric field calculation data to form a set of calculation points for the region of interest. The stimulation methods described in this embodiment include, but are not limited to, cervical alternating current stimulation, percutaneous spinal cord stimulation, and temporal interference stimulation.

[0074] Referring to Figure 1, the method of the present invention includes data input, local anatomical plane construction, generation of candidate electrode points on the body surface, screening of candidate electrode points, construction of candidate electrode combinations, calculation of electric field distribution or temporal interference modulation distribution, determination of recommended electrode layout, and result output. The core of this technical solution lies in: instead of directly using a fixed horizontal height or preset patch number to determine the electrode position, it first determines a local anatomical plane based on the individual cervical spine segment progression of the subject, then generates candidate electrode points together with the individual's body surface contour from this local anatomical plane, and finally determines the recommended electrode layout from the candidate electrode combinations based on whether the electric field distribution or temporal interference modulation distribution within the region of interest meets the preset electric field target conditions.

[0075] First, acquire or import the subject's individual data. This individual data includes individual subject images or existing head and neck models, C1-C7 cervical vertebrae segment information, neck surface information, region of interest (ROI) information, and electric field calculation data. Individual images may include T1-weighted MRI images, T2-weighted MRI images, CT images, or other images reflecting the anatomical structure of the head and neck; existing head and neck models may be finite element models or surface mesh models built from the aforementioned images. C1-C7 cervical vertebrae segment information may include vertebral body centers, intervertebral disc centers, cervical spinal cord centerlines, spinal canal centerlines, or other reference points reflecting the spatial location of the cervical vertebrae. Neck surface information may include the neck skin surface, triangular meshes of the head and neck outer surface, 3D point clouds, or attachable surface areas. ROI information is used to define the regions of interest that require focused analysis or action, including the spatial extent of the ROI, target cervical spinal cord segment identifiers or predefined target area definitions, and is used to determine the target cervical vertebrae and the set of calculation points belonging to the ROI in the electric field calculation data.

[0076] In embodiments of the present invention, medical image segmentation and head and neck model construction can be used as input acquisition methods. The present invention does not limit the specific sources of C1-C7 segment information and body surface information, as long as individual cervical segment spatial information and body surface information for constructing local anatomical planes and candidate electrode points can be obtained. Therefore, medical image segmentation, finite element modeling, or skin surface extraction are not the core improvement points of the present invention. The core improvement of the present invention lies in how to subsequently utilize this input information to determine candidate electrode layers, generate and screen candidate electrode points, construct candidate electrode combinations, and determine the recommended electrode layout based on whether the electric field distribution or temporal interference modulation distribution within the region of interest meets preset electric field target conditions.

[0077] Secondly, the local anatomical plane of the individual cervical spine is constructed. For the k-th cervical vertebral segment, the reference center P0_k and the local axial unit vector n_k of that segment are determined, and the local anatomical plane Plane_k is constructed, whose expression is:

[0078] ;

[0079] Where X is any point in space, "·" denotes the vector dot product, P0_k represents the local reference center of the k-th cervical vertebral segment, and n_k represents the local axial unit vector of that segment. P0_k can be determined by the midpoint of the centers of the adjacent intervertebral discs above and below the segment, or by the center of the vertebral body, the centerline of the cervical spinal cord, the centerline of the spinal canal, or a combination thereof. n_k can be obtained by normalizing the line connecting the centers of adjacent intervertebral discs, the line connecting the centers of adjacent vertebral bodies, the tangent vector of the centerline of the cervical spinal cord, or the tangent vector of the centerline of the spinal canal.

[0080] For example, when constructing a local plane for the C4 segment using the centers of adjacent intervertebral discs, we can define the center of the C3 / C4 intervertebral disc as D_k^upper and the center of the C4 / C5 intervertebral disc as D_k^lower. Then, P0_k can be taken as the midpoint between the two, and n_k can be taken as the unit direction vector pointing from D_k^upper to D_k^lower. The resulting Plane_k passes through the reference center of the C4 segment and is perpendicular to the local course of the C4 segment. This local plane is not a fixed global horizontal plane but varies with the degree of cervical lordosis, segmental tilt direction, and head and neck posture of the subject.

[0081] In one comparative embodiment, the preset fixed reference plane can be a fixed Z-axis horizontal section, that is, using the global Z-axis direction as the normal vector of the candidate electrode plane, and generating candidate electrode points at a fixed horizontal height corresponding to the target segment. Unlike this fixed Z-axis horizontal section, this invention determines the segment reference center and local axial direction based on individual cervical segment reference points, and constructs a local anatomical plane that varies with the individual's cervical physiological curvature accordingly.

[0082] Reference Figure 2 , Figure 2 The differences between the fixedZ horizontal section and the curved local anatomical plane of this invention are illustrated in an abstract manner. In the fixedZ horizontal section method, the candidate electrode layer is determined by a preset fixed reference layer; in the curved local anatomical plane method of this invention, the candidate electrode layer is determined by the local anatomical plane of the individual cervical spine, and its center position and normal direction change with the course of the subject's cervical spine segments. When the subject's cervical spine has physiological curvature or changes in head and neck posture, the fixed horizontal section may have angular deviations and spatial offsets from the actual cervical spine segment plane. This invention helps to improve the spatial correspondence between the candidate electrode layer and the actual target cervical spine segment.

[0083] Local orientation coordinates can be established within Plane_k. The left-right direction u_k and the back-right direction v_k within Plane_k can be determined based on an individual head and neck model or cervical segment information, where u_k and v_k are both located within Plane_k and orthogonal to n_k. Auxiliary points can also be set for geometric quality control. and , where L is the preset length. P1_k and P2_k can be used to display the left-right and rear directions of the local plane, helping to determine whether the local anatomical plane conforms to the anatomical course of the segment.

[0084] Reference Figure 3The process generates candidate electrode points on the body surface. For each cervical segment to be searched, the corresponding local anatomical plane Plane_k intersects with the individual neck surface or the outer surface of the head and neck model to obtain the corresponding surface contour or polyline. Specifically, when the body surface is represented by a triangular mesh, it can be determined one by one whether Plane_k intersects with the triangular facets of the body surface; for intersecting triangular facets, the intersection points between Plane_k and the boundary of the triangular facet are calculated, and intersection line segments are formed by adjacent intersection points; then, according to the adjacency relationship or spatial distance relationship between the endpoints of the intersection line segments, multiple intersection line segments are connected into a continuous surface contour or polyline. When multiple contours exist, the main contour used for generating candidate electrode points can be selected according to the contour length, continuity, whether it is located in the main neck region, and whether it is located in the attachable region.

[0085] After obtaining the body surface contour, the intermediate candidate electrode point Ck_5 for that segment is determined. The intermediate candidate electrode point Ck_5 can be determined based on the posterior direction v_k within Plane_k: starting from the reference center P0_k, pointing along the posterior direction v_k towards the posterior neck surface, a point on the body surface contour corresponding to the intersection of this direction is selected; alternatively, the point on the body surface contour closest to the posterior position indicated by P0_k + L·v_k is selected as the intermediate candidate electrode point Ck_5 for that segment. This intermediate candidate electrode point is used to determine the reference position for numbering candidate electrode points within the same segment, ensuring a unified geometric meaning for the candidate electrode point numbers.

[0086] like Figure 3 As shown, using Ck_5 as a reference, samples are taken along the body surface contour at preset arc length intervals to generate candidate electrode points for that segment. In one embodiment, nine candidate electrode points are generated at the source of each cervical vertebra segment, denoted as Ck_1, Ck_2, ..., Ck_9, where Ck_5 is the middle candidate electrode point, and Ck_1-Ck_4 and Ck_6-Ck_9 are located on the body surface contour on both sides of the middle candidate electrode point. Specifically, starting from Ck_5 on the body surface contour, Ck_4, Ck_3, Ck_2, and Ck_1 are obtained sequentially along one side of the contour at preset arc length intervals, and Ck_6, Ck_7, Ck_8, and Ck_9 are obtained sequentially along the other side of the contour at the same or preset arc length intervals. The arc length intervals can be determined based on electrode size, body surface curvature, target search range, or experimental design. During subsequent combination searches, some of the candidate electrode points can be selected to participate in electrode combinations according to specific stimulation patterns and constraints.

[0087] The aforementioned method for generating candidate electrode points is characterized by the fact that these points are not subjectively estimated by the operator based on surface landmarks, nor are they directly assigned using a uniform template or preset patch numbers. Instead, they are determined jointly by the local anatomical plane and the individual's surface contour. Since Plane_k originates from the individual's cervical spine segment spatial information, and the surface contour originates from the individual's outer neck surface, the candidate electrode points are simultaneously constrained by both the individual's cervical spine segment alignment and surface morphology. Under the same input conditions, candidate electrode points can be repeatedly generated according to the same rules, thereby improving the repeatability and individual adaptability of candidate electrode point generation.

[0088] After candidate electrode points are generated, they are screened for attachability. Screening criteria may include electrode size, minimum electrode spacing, attachment space, left-right pairing, upper-lower layer relationship, body surface location, safety constraints, and whether they are located in a preset attachable area. Specifically, when the body surface distance or three-dimensional distance between candidate electrode points is less than the preset minimum electrode spacing, candidate electrode points or combinations that do not meet the spacing requirements are excluded; when candidate electrode points are located in non-target body surface areas, areas that are obviously unsuitable for attachment, or do not meet the preset attachment area requirements such as the posterior neck, left posterolateral, or right posterolateral, they are excluded; when candidate electrode points do not meet the preset left-right pairing, upper-lower layer relationship, or four-electrode combination constraints, they are not included in subsequent combination searches. Through this step, candidate electrode points can be made to correspond to the local anatomical plane of the target cervical spine segment and meet the actual cervical electrode attachment requirements.

[0089] After screening candidate electrode points, leadfield pre-calculation is performed. A unit current is applied to each retained candidate electrode point, and its electric field distribution within the individual head and neck finite element model is calculated to obtain the corresponding leadfield. Unit current simulation can use a candidate electrode point as the injection electrode and set a reference electrode or return boundary to obtain the electric field distribution generated by that candidate electrode point under unit current conditions. For any electrode combination, its electric field distribution can be obtained by linearly superimposing the leadfields of relevant candidate electrode points according to electrode polarity and current amplitude. Leadfield pre-calculation avoids repeatedly performing complete finite element simulations for every candidate electrode combination, thereby improving the efficiency of four-electrode combination search.

[0090] In the four-electrode dual-channel time-interference stimulation implementation, each candidate electrode combination includes four candidate electrode points, where two candidate electrode points constitute channel A and the other two candidate electrode points constitute channel B. Each channel includes a pair of electrodes and can apply alternating currents with different or slightly different frequencies. For each candidate electrode combination, the electric fields of channel A and channel B can be calculated by linearly superimposing the leadfield, electrode polarity, current amplitude, and channel allocation relationship of each candidate electrode point, thus obtaining the electric field distribution under the corresponding candidate electrode combination. When the preset stimulation mode is time-interference stimulation, the time-interference modulation distribution corresponding to the candidate electrode combination can be further calculated based on the electric fields of channel A and channel B and the stimulation frequency parameters. Subsequently, the electric field intensity value, time-interference modulation intensity value, or electric field vector value can be extracted from the set of calculation points in the region of interest corresponding to the region of interest to determine whether the candidate electrode combination meets the preset electric field target condition.

[0091] During the combination search process, search constraints can be set. For example, the four electrodes can be required to be located in preset upper and lower layers or left and right sides; channels A and B can be required to meet preset channel configuration rules; the minimum distance between electrodes can be limited; and the geometric deviation of the electrode points relative to the target segment can be limited. Candidate combinations that meet the above constraints will proceed to the subsequent electric field calculation and recommended electrode layout determination process, while combinations that do not meet the constraints will be excluded. The above constraints can be adjusted according to specific stimulation modes, electrode attachment requirements, safety requirements, and experimental design.

[0092] After obtaining the electric field distribution or temporal interference modulation distribution corresponding to the candidate electrode combination, a set of calculation points belonging to the region of interest (ROI) is determined based on the spatial correspondence between the ROI information and the electric field calculation data. Then, the electric field intensity value, temporal interference modulation intensity value, or electric field vector value corresponding to the candidate electrode combination is extracted from this set of ROI calculation points to determine whether the candidate electrode combination meets the preset electric field target conditions. The preset electric field target conditions can be set according to the specific stimulus purpose, the spatial range of the ROI, safety requirements, or experimental design. These conditions include the electric field intensity value within the ROI reaching a preset threshold, the temporal interference modulation intensity value reaching a preset threshold, the electric field vector value meeting preset amplitude or direction requirements, the electric field statistical value within the ROI meeting a preset range, or the electric field effect result of the candidate electrode combination within the ROI meeting one or more preset sorting rules.

[0093] When a candidate electrode combination meets the preset electric field target condition, that candidate electrode combination is determined as the recommended electrode layout. When multiple candidate electrode combinations meet the preset electric field target condition, one or more recommended electrode layouts can be determined from them according to preset selection rules. Finally, a recommended electrode layout and visualization report are output. The output content may include the candidate electrode point number, the cervical vertebral segment to which it belongs, the three-dimensional spatial coordinates, the left and right side positions, the upper and lower layer positions, the channel allocation relationship, the current parameters, the electric field calculation results, and the visualization results for each electrode point in the recommended electrode layout.

[0094] Through the above embodiments, the present invention can determine the candidate electrode layer based on the individual's cervical spine segment information, neck surface information, region of interest information and electric field calculation data, and generate candidate electrode points with clear geometric rules and repeatability along the individual's body surface contour. Combined with the preset stimulation mode, the electric field distribution or time interference modulation distribution corresponding to the candidate electrode combination, and the preset electric field target conditions, the present invention can determine a cervical electrical stimulation electrode layout scheme suitable for actual attachment, stimulation scheme design or further simulation verification.

[0095] It should be noted that the focus of this invention is on the method for determining the layout of cervical electrical stimulation electrodes, rather than on the hardware structure of the electrical stimulator, the closed-loop stimulation control system, or the head and neck finite element model construction system itself. The individual images, head and neck model, cervical segment information, body surface information, and electric field calculation data can be obtained from existing equipment, software, or other modeling processes and used as input data for this method. The recommended electrode coordinates, candidate electrode point numbers, channel allocation relationships, current parameters, and electric field calculation results output by this method can be used to guide subsequent electrode attachment, stimulation scheme design, or finite element simulation verification.

[0096] The effectiveness of this invention can be further demonstrated through the following simulation experiments.

[0097] 1. Simulation experimental conditions.

[0098] The software platform for the simulation experiment of this invention is: Windows 10 operating system, Python 3.x, SimNIBS finite element electric field calculation software, and a self-written program for local anatomical plane construction, generation of candidate electrode points on the body surface, leadfield pre-calculation, four-electrode dual-channel combination search, and simulation result comparison and analysis.

[0099] The input data used in the simulation experiment of this invention includes a finite element model of the subject's head and neck, C1-C7 cervical vertebrae segment information, neck surface information, regions of interest (ROIs), and regions of non-interest (NOIs) used for comparative analysis of simulation results. The ROI is denoted as the region of interest, and the NOIs used for comparative analysis are denoted as nonROIs. The C1-C7 cervical vertebrae segment information includes data reflecting the spatial location of individual cervical vertebrae segments, such as the vertebral body center, intervertebral disc center, cervical spinal cord centerline, or spinal canal centerline. The neck surface information includes the outer surface of the head and neck model or the skin surface of the neck. The ROI is the area within the target cervical spinal cord segment that needs to be stimulated, and the NOIs are areas outside the ROI used to analyze the relative electric field distribution of the NOIs.

[0100] The stimulation method used in the simulation experiment of this invention is four-electrode dual-channel time-interference stimulation. The four electrodes are divided into channel A and channel B, and each channel includes a pair of electrodes. Alternating currents with different or slightly different frequencies are applied to channels A and B, respectively, forming a time-interference modulation distribution in the region of interest.

[0101] The comparison method used in the simulation experiment of this invention is the fixedZ fixed horizontal section method. This method uses the global Z-axis direction as the normal vector of the candidate layer, and cuts the neck surface contour at a fixed horizontal height corresponding to the target segment to generate candidate electrode points. The method of this invention is the curve local anatomical plane method. This method determines the reference center P0_k and the local axial unit vector n_k of the k-th cervical vertebra segment based on the reference points of the individual C1-C7 cervical vertebrae, and constructs... The local anatomical plane is then intersected with the individual's neck surface contour, and candidate electrode points are generated along the surface contour according to the arc length rule.

[0102] In the simulation experiment, the fixedZ fixed horizontal section method and the curve local anatomical plane method of the present invention use the same subject head and neck finite element model, the same region of interest, the same nonROI region for result comparison analysis, the same current parameters, the same four-electrode dual-channel combination rules, and the same simulation result comparison indexes to ensure that the simulation results mainly reflect the differences in the candidate electrode level determination method and the candidate electrode point generation method.

[0103] 2. Simulation content and result analysis.

[0104] The simulation experiments of this invention are three.

[0105] Simulation Experiment 1 simulates and visualizes the geometric differences of candidate electrode planes between the fixedZ fixed horizontal section method and the curve local anatomical plane method of this invention.

[0106] Simulation Experiment 1 uses the C1-C7 cervical vertebral segment information and neck surface information of the same subject. Candidate electrode layers and candidate electrode points under the same cervical vertebral segment are obtained by using the fixedZ fixed horizontal section method and the curve local anatomical plane method of the present invention, respectively. The cervical spine-Z mean angle is calculated as a comparison index of the geometric deviation between the fixedZ fixed horizontal section and the individual cervical vertebral segment course. The candidate electrode layers generated by the two methods are then drawn into a comparison diagram as shown in Figure 2.

[0107] The effects of simulation experiment 1 are further described below with reference to Figure 2. In Figure 2, the left side represents the fixed Z-axis horizontal section method, and the right side represents the curve local anatomical plane method of this invention. In the fixed Z-axis horizontal section method, the candidate electrode layers are determined by the global horizontal section, and the normal direction of each candidate layer is consistent with the global Z-axis direction; in the curve local anatomical plane method of this invention, the candidate electrode layers are determined by the local anatomical plane of the individual cervical spine, and its center position and normal direction change with the course of the subject's cervical spine segments.

[0108] Among representative subjects, the average cervical Z-angles for Sub01, Sub02, and Sub03 were 12.37°, 12.52°, and 12.68°, respectively. These geometric comparisons indicate a certain angular deviation between the actual cervical segmental course of the subjects and the fixed horizontal section of the global Z-axis. When the subjects' cervical spine exhibits physiological curvature, segmental tilt, or differences in head and neck posture, the fixed horizontal section of the Z-axis may have angular deviations and spatial offsets from the local anatomical plane of the actual cervical segment, resulting in incomplete correspondence between the candidate electrode points and the target cervical segment. The method of this invention constructs a local anatomical plane based on individual cervical segment reference points and generates candidate electrode points on the intersection of this local anatomical plane and the individual's body surface contour. This allows the candidate electrode layers to adjust according to changes in the individual's cervical segmental course, thereby improving the spatial correspondence between the candidate electrode layers and the actual target cervical segment.

[0109] Simulation Experiment 2 is a simulation comparison of the differences in electric field distribution obtained by the fixedZ fixed horizontal section method and the curve local dissection plane method of the present invention.

[0110] The simulation experiment 2 of this invention uses the same subject head and neck finite element model, the same region of interest, the same nonROI region for result comparison and analysis, the same candidate electrode search range, and the same four-electrode dual-channel combination rule. Candidate electrode points are generated using the fixedZ fixed horizontal section method and the curve local anatomical plane method of this invention, respectively, and leadfield pre-calculation and four-electrode dual-channel combination search are performed.

[0111] The specific steps of simulation experiment 2 of this invention are as follows:

[0112] A. The fixedZ method is used to generate candidate electrode points for the comparison scheme, and the curve local anatomical plane method of this invention is used to generate candidate electrode points for the experimental scheme.

[0113] B. Adhesion screening is performed on the candidate electrode points generated by the two methods respectively, and the candidate electrode points that meet the requirements of electrode size, minimum electrode spacing, left and right side distribution rules, upper and lower layer distribution rules, channel pairing rules and safety requirements are retained.

[0114] C. Calculate the electric field per unit current for each candidate electrode point after screening to obtain the corresponding leadfield.

[0115] D. Construct candidate electrode combinations according to the four-electrode dual-channel time interference stimulation rule, and calculate the electric field distribution or time interference modulation distribution under different candidate electrode combinations based on leadfield linear superposition.

[0116] E. Extract the simulation results comparison indicators of the candidate electrode combinations obtained by the fixedZ fixed horizontal section method and the curve local anatomical plane method of the present invention in the region of interest and the nonROI region used for result comparison analysis, and compare the results of the two methods.

[0117] The simulation results comparison metrics used in simulation experiment 2 of this invention include ROI mean, nonROI / ROI%, Top 10 high TI centroid distance ROI, and Top 10 hit ratio within ROI. Here, ROI mean represents the average electric field intensity or average time-interference modulation intensity within the region of interest; nonROI / ROI% represents the ratio of stimulus intensity between the non-interested region and the region of interest, reflecting the relative stimulus situation of the non-interested region; Top 10 high TI centroid distance ROI represents the spatial distance between the centroid of the high-intensity region and the region of interest, reflecting whether the high-intensity region is closer to the region of interest; and Top 10 hit ratio within ROI represents the proportion of the high-intensity region falling within the region of interest, reflecting the spatial overlap between the high-intensity region and the region of interest. These metrics are used in the simulation experiment to compare and analyze the results of the fixedZ fixed horizontal section method and the curve local anatomical plane method of this invention, and do not imply that all of the above metrics must be used simultaneously in the actual implementation of this invention. Some simulation results are shown in Table 1. Among them, ROI mean, nonROI / ROI%, Top10 high TI centroid distance from ROI and Top10 hit ratio within ROI are used to compare the electric field distribution effect in simulation experiment 2, and E-field angle is used to analyze the directional differences in simulation experiment 3.

[0118] Table 1 Comparison of partial simulation results between the fixedZ method and the curve method of this invention.

[0119]

[0120] The effects of simulation experiment 2 are further described below with reference to Table 1.

[0121] As shown in Table 1, in Sub01, the difference in ROImean between the curve method of this invention and the fixedZ method is -0.069V / m, indicating that the curve method does not simply increase the average intensity of the ROI; however, its nonROI / ROI% decreases by 6.398 percentage points, the centroid distance of the Top 10 high TI regions from the ROI is shortened by 3.741 mm, and the Top 10 hit rate within the ROI increases by 5.738 percentage points. These results demonstrate that, under this simulation setting, the curve method of this invention can still reduce the relative stimulation in non-interest regions and bring high-intensity regions closer to the region of interest, even with a slightly lower ROImean.

[0122] Table 1 also shows that in Sub03, the difference in ROI mean between the curve method of this invention and the fixedZ method is -0.048 V / m, the nonROI / ROI% decreases by 4.619 percentage points, the distance between the centroids of the Top 10 high-TI regions and the ROI is shortened by 2.066 mm, and the Top 10 hit rate within the ROI increases by 13.245 percentage points. These results further demonstrate that the method of this invention, by altering the spatial position of candidate electrode points through the local anatomical plane of the individual cervical spine, can change the electric field distribution of the region of interest and its surrounding areas, and improve the spatial correspondence between high-intensity regions and the region of interest.

[0123] As can be seen from Simulation Experiment 2, the method of this invention does not simply improve the ROI mean. Instead, it demonstrates the effectiveness of the curve local anatomical plane method compared to the fixed Z fixed horizontal plane method by comparing simulation results such as nonROI / ROI%, Top 10 high TI centroid distance ROI, and Top 10 hit ratio within ROI, in terms of the relative stimuli in non-interest areas and the spatial location of high-intensity areas. The above indicators are used for the results analysis of this simulation experiment and do not limit the actual implementation of this invention to using all of the above indicators simultaneously.

[0124] Simulation Experiment 3 simulates the four-electrode dual-channel combined search and E-field direction differences between the fixedZ fixed horizontal section method and the curve local anatomical plane method of this invention.

[0125] Simulation Experiment 3 of this invention uses the same subject head and neck finite element model, region of interest, non-ROI region for result comparison and analysis, current parameters, and four-electrode dual-channel combination rules as Simulation Experiment 2. The difference lies in that Simulation Experiment 3 focuses on analyzing the differences in the E-field direction of the candidate electrode combinations obtained by the two methods within the region of interest, and explains the process of completing the four-electrode dual-channel combination search through leadfield pre-calculation.

[0126] The specific steps of simulation experiment 3 of this invention are as follows:

[0127] S1, calculate the electric field of each candidate electrode point in the candidate electrode point set by unit current, and obtain Leadfield_1, Leadfield_2, ..., Leadfield_N.

[0128] S2, select four electrode points from the candidate electrode point set, and form channel A and channel B according to preset rules.

[0129] S3. Based on the leadfield and channel relationship corresponding to each candidate electrode point, perform linear superposition to calculate the electric field of channel A, the electric field of channel B, and the corresponding E-field distribution or TI modulation distribution.

[0130] S4. Calculate the average included angle and vertical component of the E-field within the region of interest, and compare the directional results of the fixedZ fixed horizontal section method and the curve local anatomical plane method of the present invention.

[0131] The directional result comparison indices used in simulation experiment 3 of this invention include the average E-field angle and the vertical component of the E-field. In embodiments where the target direction is set laterally or perpendicular to the cervical spinal cord axis, the average E-field angle represents the degree of deflection of the electric field direction within the region of interest relative to the cervical spinal cord axis, and the vertical component of the E-field represents the proportion of the electric field component perpendicular to the cervical spinal cord axis within the region of interest. Under this target direction setting, an increase in the average E-field angle or an increase in the vertical component of the E-field indicates that the electric field direction is closer to the preset target direction. For four-electrode dual-channel temporal interference stimulation, the relationship between the electric field directions of channels A and B within the region of interest affects the temporal interference modulation distribution. Therefore, the E-field directional result comparison index can be used in simulation experiments to analyze the differences in the electric field directions generated by the two methods within the region of interest.

[0132] The effects of simulation experiment 3 are further described below with reference to Table 1. Simulation experiment 3 is used to verify the effectiveness of constructing candidate electrode combinations based on the candidate electrode point set according to the four-electrode dual-channel time interference stimulation method, and selecting recommended electrode layouts based on the electric field distribution or time interference modulation distribution in the region of interest. Specifically, four electrodes are first selected from the candidate electrode points of each segment, and A and B channels are constructed according to the preset channel rules; then, the leadfield of each candidate electrode point is obtained based on the unit current electric field calculation results corresponding to the candidate electrode points. Subsequently, the corresponding leadfields are linearly superimposed according to the positive and negative polarity relationship of the A and B channels to obtain the E-field distribution or TI modulation distribution under the corresponding candidate electrode combination. Finally, the recommended electrode combination, channel allocation, and current parameters are determined according to the preset electric field target conditions such as the field strength level, nonROI / ROI%, hotspot spatial location, and E-field direction in the region of interest. Table 1 shows the simulation evaluation results of the fixedZ comparison method and the curve layout method of the present invention in representative subjects.

[0133] As shown in Table 1, in Sub01, the E-field angle of the curve method of the present invention increases by 8.874° compared to the fixedZ method. In Sub02, the E-field angle of the curve method of the present invention increases by 12.759° compared to the fixedZ method. In Sub03, the E-field angle of the curve method of the present invention increases by 17.564° compared to the fixedZ method. These results demonstrate that, in embodiments where the target direction is set laterally or perpendicular to the cervical spinal axis, the method of the present invention, by allowing the candidate electrode layer to vary with the individual cervical vertebral segment, can alter the E-field orientation relationship within the region of interest and improve the spatial superposition direction of the four-electrode dual-channel temporal interference stimulation within the region of interest.

[0134] Combining simulation experiments 1, 2, and 3, it can be seen that the fixedZ fixed horizontal section method mainly generates candidate electrode points based on the global horizontal height. When the subject has significant cervical lordosis, segmental tilt, or head and neck posture differences, the candidate electrode points may spatially mismatch with the actual target cervical vertebral segments. The method of this invention utilizes individual cervical vertebral segment reference points to construct a local anatomical plane, and combines this local anatomical plane with the individual's body surface contour to generate candidate electrode points, which can improve the spatial correspondence between candidate electrode points and target cervical vertebral segments. In the simulation experiments, by comparing results such as ROI mean, nonROI / ROI%, spatial location of high-intensity regions, and E-field direction, the differences in effectiveness between the method of this invention and the fixedZ fixed horizontal section method in terms of electric field effect in the region of interest, relative stimulation in the non-interested region, spatial location of the high-intensity region, and electric field direction can be further illustrated.

[0135] The simulation experiments above demonstrate that the method of this invention, utilizing a local anatomical plane construction technique based on the individual's cervical spine physiological curvature, can overcome the inconsistency between the fixedZ horizontal section and the actual local anatomical plane of the cervical spine segment. The candidate electrode point generation technique, combining the local anatomical plane with the individual's body surface contour, improves the regularity, repeatability, and surface adaptability of candidate electrode point generation. By employing leadfield pre-computation and a four-electrode dual-channel combined search technique, E-field distributions or TI modulation distributions under different candidate combinations can be obtained. Indicators such as nonROI / ROI%, high-intensity region spatial location, and E-field direction are used as comparative indicators in the simulation experiments to demonstrate the difference in effectiveness between the method of this invention and the fixedZ horizontal section method, but do not limit the actual implementation of this invention to using all of the above indicators simultaneously.

Claims

1. A method for deploying non-invasive cervical electrical stimulation electrodes based on the individual's cervical spine physiological curvature, characterized in that, The deployment method includes the following steps: Step 1: Obtain individual cervical spine segment information, neck surface information, region of interest information, and data required for electric field calculation; Step 2: Construct the local anatomical plane of the corresponding cervical vertebral segment based on the segmental reference center and the local axial direction; Step 3: Generate candidate electrode points according to the preset arc length rules; Step 4: Screen candidate electrode points according to electrode attachment requirements and layout rules; Step 5: Construct candidate electrode combinations according to the preset stimulation mode, and calculate the electric field distribution or time interference modulation distribution; Step 6: Determine the recommended electrode layout from the candidate electrode combinations; Step 7: Output the candidate point number, cervical segment to which each electrode point belongs, three-dimensional spatial coordinates, left and right side positions, upper and lower layer positions and channel allocation relationship of each electrode point in the recommended electrode layout, and generate a report containing recommended electrode layout parameters, candidate electrode point information, electric field calculation results and visualization results.

2. The non-invasive neck electrical stimulation electrode placement method according to claim 1, characterized in that, The steps for obtaining individual cervical spine segment information of the subject in step 1 are as follows: The first step is to obtain image annotations, segmentation labels, centerline data, or model data for the C1-C7 cervical vertebrae of the subjects; The second step is to extract at least one segmental reference point from the image annotation, segmentation label, centerline data or model data, including the vertebral body center, intervertebral disc center, cervical spinal cord centerline point or spinal canal centerline point; The third step is to convert or record the segment reference points in a spatial coordinate system consistent with the neck surface information and electric field calculation data to form cervical segment information for constructing local anatomical planes.

3. The non-invasive neck electrical stimulation electrode placement method according to claim 1, characterized in that, The steps for obtaining neck surface information in step 1 are as follows: The first step is to read the data of the subject's neck skin surface, head and neck outer surface mesh, 3D point cloud or attachable surface area; and extract the neck surface area corresponding to the target cervical vertebra segment. The second step is to convert or record the neck surface area in a spatial coordinate system consistent with the cervical vertebral segment information to form individual neck surface information that is calculated by intersecting with the local anatomical plane.

4. The non-invasive neck electrical stimulation electrode placement method according to claim 1, characterized in that, The steps for obtaining the region of interest information in step 1 are as follows: The first step is to read the spatial extent of the region of interest, the target cervical spinal cord segment identifier, or the pre-defined target area; The second step is to determine whether the region of interest, the target cervical spinal cord segment identifier, or the preset target area definition is in the same spatial coordinate system as the electric field calculation data or has a spatial correspondence. If so, proceed to the fourth step; otherwise, proceed to the third step. The third step is to perform spatial transformation, registration, mapping, interpolation, or nearest neighbor correspondence processing on the region of interest when the region of interest, the target cervical spinal cord segment identifier, or the preset target area definition is not in the same spatial coordinate system as the electric field calculation data or there is no spatial correspondence. This will establish a spatial correspondence between the region of interest and the electric field calculation data before proceeding to the fifth step. The fourth step is to directly read the correspondence between the region of interest and the electric field calculation data when they are in the same spatial coordinate system or have a spatial correspondence. The fifth step involves determining, based on the spatial correspondence between the region of interest and the electric field calculation data, the grid nodes, grid cells, or sampling points falling within the region of interest in the electric field calculation data, thus forming a set of calculation points for the region of interest.

5. The method for non-invasive neck electrical stimulation electrode placement according to claim 1, characterized in that, The segment reference center and local axial direction mentioned in step 2 are obtained through the following steps: The first step is to determine the target cervical segment corresponding to the target stimulation area based on the spatial location of the region of interest, the target cervical spinal cord segment identifier, or the pre-defined target area. The second step involves using the target cervical vertebrae as the center, determining one or more cervical vertebrae to participate in the generation of candidate electrode points based on the preset range of adjacent segments, electrode size, stimulation mode, and safety constraints, and determining the candidate electrode search range based on the spatial location of the determined cervical vertebrae. The third step is to read one or more segmental reference points, such as the vertebral body center, intervertebral disc center, cervical spinal cord centerline point, or spinal canal centerline point, for each cervical vertebral segment involved in generating candidate electrode points. The fourth step is to calculate the segmental reference center P0_k of the corresponding cervical vertebral segment based on the segmental reference point. The segmental reference center P0_k is determined by the midpoint of the center of the adjacent intervertebral disc above and below the segment, the center of the vertebral body, the center line point of the cervical spinal cord, the center line point of the spinal canal, or a combination thereof. The fifth step involves calculating the local axial direction of the corresponding cervical vertebral segment based on one or more of the following: the direction of the line connecting the reference points of adjacent segments, the direction of the line connecting the centers of adjacent intervertebral discs, the direction of the line connecting the centers of adjacent vertebral bodies, the tangent vector of the cervical spinal cord centerline, or the tangent vector of the spinal canal centerline. The local axial direction is then normalized to obtain the local axial unit vector n_k.

6. The non-invasive neck electrical stimulation electrode placement method according to claim 5, characterized in that, In step 2, the local anatomical plane of the cervical vertebral segment is constructed by the segment reference center P0_k and the local axial unit vector n_k. Specifically, the segment reference center P0_k is used as the plane reference point of the local anatomical plane, and the local axial unit vector n_k is used as the normal vector of the local anatomical plane. The local anatomical plane allows the level of the candidate electrode point to be determined by the spatial information of the individual cervical spine segment, and to change with the physiological curvature of the individual cervical spine.

7. The non-invasive neck electrical stimulation electrode placement method according to claim 6, characterized in that, The steps in step 3 for generating candidate electrode points according to the preset arc length rule are as follows: The first step is to represent the local anatomical plane as follows: And calculate the signed distances of each surface point, mesh node, or patch boundary point in the individual neck body surface or the outer surface of the head and neck model relative to the local anatomical plane; The second step is to determine the body surface edges, body surface patches, or body surface points that intersect with the local anatomical plane based on the signed distance; for body surface edges located on both sides of the local anatomical plane, the intersection point of the body surface edge and the local anatomical plane is calculated by linear interpolation; and body surface points located within a preset distance threshold are selected as candidate contour points. The third step is to connect the intersection points or candidate contour points according to spatial adjacency, contour continuity or arc length order to obtain the body surface contour formed after the individual's neck surface is cut out by the local anatomical plane. The fourth step is to determine the center reference point or intermediate candidate point on the body surface contour. Fifth step: Taking the rear center reference point or the middle candidate point as the starting point, calculate the arc length distance along the body surface contour to the left and right respectively; Step 6: Based on the preset arc length interval, electrode size, or number of candidate points, sample sequentially on both sides of the body surface contour to generate multiple candidate electrode points; The seventh step is to record the cervical vertebral segment to which the candidate electrode point belongs, the candidate point number, and determine the corresponding three-dimensional spatial coordinates.

8. The non-invasive neck electrical stimulation electrode placement method according to claim 7, characterized in that, The steps for screening candidate electrode points based on electrode attachment requirements and layout rules in step 4 are as follows: The first step is to aggregate the candidate electrode points generated according to the preset arc length rules into a candidate electrode point set, and obtain the three-dimensional spatial coordinates, the cervical vertebra segment to which each candidate electrode point belongs, the candidate point number, the location of the corresponding body surface contour, and the corresponding body surface area information for each candidate electrode point. The second step is to determine the position of the candidate electrode points according to the preset attachable area: when a candidate electrode point is located outside the preset attachable area or within the preset exclusion area, the candidate electrode point is removed from the candidate electrode point set; the preset attachable area is determined by one or more of the following: neck surface label, body surface contour range, spatial coordinate range, attachable area boundary or exclusion area boundary. The third step is to filter the segment range of candidate electrode points based on the target segment location and the candidate electrode search range; read the cervical segment to which the candidate electrode point belongs, the candidate point number, and the position of the candidate point on the corresponding body surface contour, determine whether the candidate electrode point belongs to one or more cervical segments involved in the generation of candidate electrode points, and determine whether the candidate electrode point is within the preset candidate electrode search range. If a candidate electrode point does not belong to the cervical segment involved in the generation of candidate electrode points, or is not within the preset candidate electrode search range, then the candidate electrode point is removed from the candidate electrode point set. The fourth step is to determine the spacing between candidate electrode points based on the preset minimum electrode spacing: when the spacing between two candidate electrode points is less than the preset minimum electrode spacing, at least one candidate electrode point is eliminated, or the candidate point combination composed of the two candidate electrode points is eliminated; the spacing is determined by the arc length of the candidate electrode point on the body surface contour, or by one or more of the Euclidean distance between the three-dimensional coordinates of the candidate electrode points and the geodesic distance of the body surface. The fifth step involves combining and constraining the remaining candidate electrode points according to the preset stimulation mode and layout rules. The layout rules are preset based on the number of electrodes, the number of channels, electrode attachment requirements, and the stimulation mode, including one or more of the following: left-right distribution rules, upper-lower layer distribution rules, channel pairing rules, electrode number rules, or electrode spacing rules. Among them, the left-right distribution rules are determined based on the body surface contour position of the candidate electrode point relative to the posterior midline reference point or the middle candidate point; the upper-lower layer distribution rules are determined based on the cervical vertebral segment to which the candidate electrode point belongs or the upper-lower layer number; the channel pairing rules are determined based on the number of channels, electrode polarity, and channel composition relationship in the preset stimulation mode; and the electrode spacing rules are determined based on the arc distance, Euclidean distance, or geodesic distance between the candidate electrode points.

9. The method for non-invasive neck electrical stimulation electrode placement according to claim 8, characterized in that, Step 5, which involves constructing candidate electrode combinations according to a preset stimulation pattern and calculating the electric field distribution or time-interference modulation distribution, includes: The first step is to read the candidate electrode points that have been screened and retained, and to use the candidate electrode points as the set of candidate electrode points after screening. Based on the preset stimulation mode, the number of electrodes, number of channels, electrode polarity, current amplitude and stimulation frequency parameters required for the candidate electrode combination are determined. The second step is to select candidate electrode points from the set of candidate electrode points after screening, according to the number of electrodes, the number of channels, the electrode polarity and the preset combination rules, and to define the selected candidate electrode points and their corresponding channel allocation relationship, electrode polarity and current parameters as a candidate electrode combination. The third step is to perform leadfield pre-calculation on the candidate electrode points in the selected candidate electrode point set to obtain the unit current electric field distribution corresponding to each candidate electrode point. The fourth step is to linearly superimpose the leadfield, electrode polarity, current amplitude and channel allocation relationship of each candidate electrode point in the candidate electrode combination to obtain the electric field distribution under the corresponding candidate electrode combination. Fifth step: When the preset stimulation mode is time interference stimulation, the time interference modulation distribution under the corresponding candidate electrode combination is further calculated based on the electric field distribution and stimulation frequency parameters corresponding to different channels.

10. The method for non-invasive neck electrical stimulation electrode placement according to claim 9, characterized in that, The steps for determining the recommended electrode layout from the candidate electrode combinations in step 6 are as follows: The first step is to determine the set of calculation points for the region of interest based on the spatial correspondence between the region of interest information and the electric field calculation data; The second step is to extract the electric field intensity value, time interference modulation intensity value, or electric field vector value corresponding to the candidate electrode combination within the set of calculation points in the region of interest. The third step is to determine whether the candidate electrode combination meets the preset electric field target condition based on the electric field intensity value, time interference modulation intensity value, or electric field vector value. The fourth step is to determine the candidate electrode combinations that meet the preset electric field target conditions as the recommended electrode layout; When there are multiple candidate electrode combinations that meet the preset electric field target conditions, one or more recommended electrode layouts are determined from them according to preset selection rules.

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