Method for generating a structured hexagonal mesh of an individualized blood vessel wall

Abstract

The application belongs to the technical field of medical image processing, and relates to a structured hexahedral mesh generation method for individualized blood vessel walls, comprising the following steps: s1: when the target aortic blood vessel has no branch, entering the solid construction step of the aortic blood vessel wall, otherwise, performing the solid construction step of the aortic blood vessel wall and the solid construction step of each branch blood vessel wall; s2: giving the mesh seeds of the boundaries of the blood vessel wall solid, and generating the structured hexahedral mesh of the blood vessel wall by lofting or scanning; s3: performing mesh checking by calculating the included angle, the length-width ratio coefficient and the geometric deviation coefficient, so as to ensure that the mesh quality meets the calculation requirements. The method can generate layered structured hexahedral meshes for the blood vessel walls without branches, and can generate regular hexahedral meshes for the complex three-dimensional solids such as the blood vessel walls with holes and branches. The method has weak shape requirements, strong generalization and low calculation cost.

Description

Technical Field

[0001] This invention belongs to the field of medical image processing technology, and in particular relates to a method for generating structured hexahedral meshes for individualized blood vessel walls. Background Technology

[0002] In the field of biomechanics, imaging techniques (such as X-rays, CTA, OCT, and ultrasound) are often used to acquire the in vivo morphology of organisms. After acquiring the morphology, numerical simulation methods (such as the finite element method) can be used to simulate and study the organism. The core of the finite element method is to divide the continuous solution domain into several smaller sub-regions, which are called "elements". Therefore, if mechanical finite element analysis is required, it is necessary to perform three-dimensional modeling of the image and divide the model into individual elements; this process is called mesh generation.

[0003] For mesh generation of 3D solids, based on the mesh shape, it can be divided into tetrahedral meshes and hexahedral meshes: tetrahedral meshes are flexible and can adapt to complex geometries, but their accuracy in finite element analysis (FEM) is lower; hexahedral meshes have higher FEM accuracy and numerical stability, but are only suitable for geometries that can be meshed into regular shapes. Based on mesh structure, they can be divided into unstructured meshes and structured meshes: unstructured meshes have irregular node and element arrangements, but can be flexibly divided according to the geometry; structured meshes have regular node and element arrangements, resulting in high mesh quality and high FEM accuracy, but poor adaptability to geometries, and can only be used for structures with regular geometries. Therefore, if high FEM accuracy and regular node and element arrangements are required, structured hexahedral meshes are a relatively better choice.

[0004] Currently, there are some existing methods for generating 3D solid models of blood vessel walls from CTA images. CTA, or CT angiography, uses CT equipment to image blood vessels throughout the body by injecting contrast agents intravenously. What is seen in the image is the flow area of ​​blood (blood flow domain). Assuming the thickness of the blood vessel wall (1-2 mm), expanding the blood flow domain outward by 1-2 mm yields a 3D solid model of the blood vessel wall. After obtaining the 3D solid model, a mesh needs to be generated before finite element analysis can be performed. Existing mesh generation techniques applied to blood vessel walls all generate tetrahedral meshes (structured or unstructured), resulting in poor accuracy in subsequent finite element calculations. Furthermore, since the blood vessel wall has a layered structure, with the intima, media, and adventitia having different mechanical properties, unstructured meshes make it difficult to distinguish different layers using node and element numbers during calculation, hindering accurate mechanical modeling. Currently used cohesion models and extended finite element method (FEM) simulation techniques all require accurate description of the layered structure of the blood vessel wall. Unstructured meshes cannot obtain the boundary information between layers and cannot describe the layered structure in a regular manner according to the thickness. Structured mesh elements need to be generated before subsequent analysis can be performed.

[0005] Chinese patent application CN202210884754.2, entitled "Finite Element Unstructured Hexahedral Mesh Generation Method," generates unstructured hexahedral meshes from a fully tetrahedral mesh model using a traversal approach. This application can only generate unstructured meshes, not structured ones. Chinese patent application CN201811241872.1, entitled "Actual Stratigraphic Full Hexahedral Mesh Generation Method and Apparatus," generates hexahedral meshes for the solid structure of strata without pores. This application generates hexahedral meshes by regularly resampling the actual stratigraphic layers, generating mesh node coordinates, and then generating the hexahedral mesh according to the rules. It can only be applied to layered entities, exhibiting strong specificity, weak generalization, and high computational cost.

[0006] Chinese patent application CN202311124316.7, entitled "Method, Apparatus, Computer Equipment and Storage Medium for Modeling Blood Vessels", is a method for modeling blood vessel cavities and blood vessel walls, which generates unstructured tetrahedral meshes instead of hexahedral meshes. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a method for generating structured hexahedral meshes for individualized blood vessel walls.

[0008] In view of this, the present invention proposes a method for generating a structured hexahedral mesh for individualized blood vessel walls, the method comprising:

[0009] Step s1: When the target aorta has no branches, proceed to the solid construction step of the aorta wall; otherwise, proceed to the solid construction step of the aorta wall and the solid construction step of each branch wall.

[0010] Step s2: Assign mesh seeds to each boundary of the blood vessel wall entity, and loft to generate a structured hexahedral mesh of the blood vessel wall;

[0011] Step s3: Perform a mesh check by calculating the included angle, aspect ratio coefficient, and geometric deviation coefficient to ensure that the mesh quality meets the calculation requirements.

[0012] Preferably, the solid construction step of the aortic vessel wall in step s1 includes:

[0013] Step 1: Obtain the target aortic blood flow region from the CT image;

[0014] Step 2: Expand the aortic blood flow area outward to generate the aortic vessel wall region;

[0015] Step 3: Divide the aortic vessel wall region into cross sections and obtain the section outline of each cross section;

[0016] Step 4: For each segmentation contour line, obtain at least one feature point according to the same proportion, and output the coordinates of each feature point;

[0017] Step 5: Draw the corresponding guide line using spline curves for each feature point obtained;

[0018] Step 6: Loft the solid structure based on the outline and guide line of the outer wall of the aorta to complete the solid construction of the outer wall of the aorta; Loft cut the inner wall of the aorta based on the outline and guide line to complete the solid construction of the aorta.

[0019] Preferably, step 1 includes:

[0020] Starting from a set of seed points in the blood flow region, the algorithm gradually expands to adjacent pixels based on the similarity of gray levels until it grows to all target blood flow region areas.

[0021] Remove blood basins from non-target areas and fill in the gaps created during generation;

[0022] Smooth the entire area.

[0023] Preferably, step 2 includes:

[0024] The outermost layer of the blood flow domain is expanded outward by a set distance in the thickness direction. The expanded area includes the blood flow domain. A Boolean subtraction operation is performed on the expanded area and the blood flow domain to obtain the blood vessel wall region.

[0025] Preferably, step 3 includes:

[0026] The aortic vessel wall region is divided according to a specified distance and a specified number of segments, generating the outline of the outer wall of the aorta and the outline of the inner wall of the aorta.

[0027] Preferably, the solid construction step of each branch vessel wall in step s1 includes:

[0028] Step 1: Obtain the target aortic blood flow region with branching vessels from the CT image;

[0029] Step 2: Select the blood flow area of ​​the aorta and expand it outward to generate the aortic vessel wall region;

[0030] Step 3: Divide the aortic vessel wall into cross-sections and obtain the cross-sectional outline of each cross-section;

[0031] Step 4: For each segmentation contour line, obtain at least one feature point according to the same proportion, and output the coordinates of each feature point;

[0032] Step 5: Select feature points from each contour line and draw the corresponding guide lines using spline curves;

[0033] Step 6: Loft the solid structure based on the outline and guide lines of the aortic outer wall to complete the solid construction of the aortic vessel wall;

[0034] Step 7: Expand the aortic blood flow area with branched vessels outward to generate the aortic vessel wall region with branched vessels;

[0035] Step 8: Perform steps 9 through 12 sequentially on the wall of each branch vessel:

[0036] Step 9: Divide the branch vessel wall into cross sections and obtain the section outline of each cross section;

[0037] Step 10: Output the coordinates of feature points on the contour line of the branch vessel wall;

[0038] Step 11: Draw the scanning guide line based on the feature points of the branch vessel outline;

[0039] Step 12: Scan according to the outline and guide line of the outer wall of the branch vessel. The scanning start point is the selected outer wall outline, and the scanning end point is the outer wall of the aorta, thus completing the solid construction of the outer wall of the branch vessel; Scan and cut according to the outline and guide line of the inner wall of the branch vessel to complete the solid construction of the branch vessel wall.

[0040] Step 13: Loft the solid structure based on the contour line and guide line of the aortic inner wall to complete the solid construction of the aortic vessel wall.

[0041] Preferably, step s2 includes:

[0042] The thickness, circumferential, and axial boundaries of the vessel wall are assigned a specified number of mesh seeds. When the target aorta has no branches, a layered structured hexahedral mesh is generated by lofting. When the target aorta has branches, a layered hexahedral mesh is generated by aortic lofting, and a layered structured hexahedral mesh is generated by branch scanning.

[0043] Preferably, step s2 further includes: dividing the vascular wall entity whose size and / or structural changes meet the set requirements into multiple sub-regions, and performing lofting or scanning according to the set lofting or scanning boundaries and order.

[0044] Preferably, step s3 includes:

[0045] For each tetrahedral element, calculate the included angle between every two faces to ensure that the included angle is not less than 10° and not greater than 160°.

[0046] Calculate the aspect ratio for each hexahedral element to ensure that the aspect ratio is no greater than 10.

[0047] Calculate the geometric deviation coefficient for each element, which is the ratio of the maximum gap between the element edge and the geometric edge to the element edge length, ensuring that no element has a geometric deviation coefficient exceeding 0.2;

[0048] When all three conditions above are met, the mesh quality of the individualized blood vessel wall meets the computational requirements.

[0049] Compared with the prior art, the advantages of the present invention are:

[0050] 1. The method of the present invention starts from medical imaging and integrates the complete process of generating individualized finite element models of blood vessel walls.

[0051] 2. This method takes into account the layered structural characteristics of the blood vessel wall, and the generated mesh is layered.

[0052] 3. The method of the present invention can generate layered structured hexahedral meshes for unbranched blood vessel walls, and generate regular hexahedral meshes for complex three-dimensional entities such as blood vessel walls with holes and branches. This method has weak shape requirements, strong generalization ability, and low computational cost. Attached Figure Description

[0053] Figure 1(a) is a flowchart of the structured hexahedral mesh generation method for the aorta without branches according to the present invention; Figure 1(b) is a flowchart of the structured hexahedral mesh generation method for the aorta with branches according to the present invention;

[0054] Figure 2 It is the region of the aortic vessel wall;

[0055] Figure 3 It is the sectional outline of the aortic wall and its cross-section;

[0056] Figure 4 It is a guide wire for aortic radiography;

[0057] Figure 5 It is the actual structure of the aortic vessel wall and aortic blood flow area after the layout;

[0058] Figure 6 It is the solid aortic vessel wall after radiographic resection;

[0059] Figure 7 It is a structured hexahedral mesh of the aortic vessel wall;

[0060] Figure 8 It is the aortic blood flow region with branched vessels;

[0061] Figure 9 It is the cross-sectional outline of each section of the branch vessel wall;

[0062] Figure 10 It involves drawing guide lines for scanning based on the outline of branch vessels;

[0063] Figure 11 It is the outer wall of the branch vessel after scanning;

[0064] Figure 12 It is the solid structure of the branch vessel wall after scanning and resection;

[0065] Figure 13 It is the final generated hexahedral mesh of the aorta with branching vessels. Detailed Implementation

[0066] In finite element method (FEM) simulations, a mesh divides a continuum into a finite number of elements interconnected by nodes. The physical behavior of each individual element is described using a mathematical model, thus approximating the physical characteristics of the entire continuum. Therefore, mesh generation is crucial in FEM simulations.

[0067] Because biological tissues such as blood vessels are located within living organisms, they are difficult to observe directly in vivo. Their geometric shape is often obtained through imaging methods such as X-rays, CT scans, and ultrasound. Due to the need to meet various functional requirements of the human body, the geometric shape of biological tissues such as blood vessels is extremely complex. For the aorta, its geometric shape has the following characteristics: (1) the diameter varies at different locations; (2) the degree of curvature varies at different locations; and (3) the aorta is connected to many branch vessels. Therefore, mesh generation is difficult and complex for such a geometrically complex object as the aorta.

[0068] Currently, most meshes generated for blood vessel walls are tetrahedral. However, using tetrahedral meshes for finite element analysis (FEM) results in lower computational accuracy, while using hexahedral meshes offers higher accuracy. Therefore, generating hexahedral meshes for the blood vessel wall is necessary. Furthermore, the blood vessel wall is a layered structure, possessing three distinct mechanical layers—the intima, media, and adventitia—and each layer within the media and adventitia is also layered, connected by elastic fibrous lamellar structures linked by collagen fibers. Therefore, modeling the aorta as a layered structure in FEM calculations not only helps assign different material properties to different membranes to simulate realistic tissue but also facilitates the construction of interlayered structures, playing a crucial role in simulating pathological processes such as the expansion and rupture of aortic dissections.

[0069] Currently, most mesh generation for blood vessel walls produces unstructured meshes. While unstructured meshes offer high flexibility, they are prone to producing low-quality elements with uneven size transitions, leading to insufficient computational accuracy. Furthermore, in unstructured meshes, the size of each element is uncontrolled, and there is no consistent relationship between the numbering of a node (or element) and its adjacent nodes (or elements); the order of node numbers (or element numbers) is random. This makes it difficult to control the mechanical or kinematic behavior of a particular node (or element) through node numbers (element numbers) when writing finite element subroutines, which is extremely detrimental to the secondary development of finite element methods. The structured mesh generated by this patent has an ordered relationship between adjacent nodes (or elements). During secondary development, only the range of nodes (or elements) needs to be specified to control the mechanical or kinematic behavior of a particular node (or element).

[0070] Currently, most methods for generating vascular wall meshes focus only on the aorta, neglecting branch vessels. Blood flow in the aorta extends into branch vessels to supply downstream blood, and the presence of branch vessels also affects the aortic configuration. Branch vessels and the aorta interact directly, maintaining the mechanical stability of the vascular system. Therefore, the influence of branch vessels cannot be ignored in finite element simulations. However, there is currently no method for generating hexahedral meshes for aortas with branch vessels, let alone layered hexahedral meshes. This application develops a method for generating layered hexahedral meshes for aortas with branch vessels, and it can specify the range of node (or element) numbers for each layer of the branch module and aortic module, making it possible to describe the layer-specific behavior in subsequent calculations. The aortic mesh generated using this method can be used in finite element simulations such as constructing cohesion models based on individualized patient vascular configurations and extended finite element methods. These methods require accurate description of the layered structure of the vascular wall; unstructured meshes cannot obtain boundary information between layers and cannot regularly describe the layered structure proportionally to thickness. Structured mesh elements must be generated for subsequent analysis.

[0071] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0072] Example 1

[0073] The embodiments of the present invention propose a method for generating structured hexahedral meshes for individualized blood vessel walls. Figure 1(a) shows a flowchart of the method for generating structured hexahedral meshes for the aorta without branches; it includes the following specific steps:

[0074] Part One:

[0075] 1. Obtain the aortic blood flow region from CT images. CT images distinguish different structures and tissues through grayscale. Starting with a set of seed points in the blood flow region, the region is gradually expanded to adjacent pixels based on grayscale similarity criteria until all target blood flow regions are reached. Afterwards, the blood flow region generation is manually checked, non-target areas are removed, gaps are filled, and finally, the entire region is smoothed.

[0076] 2. For example Figure 2 As shown, the aortic blood flow domain expands outward to form the vessel wall region. For the blood flow domain generated in the previous step, the outermost layer of the blood flow domain is expanded outward along the thickness direction by a certain distance, typically 1-2 mm, although the thickness of the vessel wall varies at different locations. The expanded region contains both the blood flow domain and the vessel wall region. A Boolean subtraction operation needs to be performed on the expanded region and the blood flow domain to obtain the vessel wall region.

[0077] 3. For example Figure 3As shown, the aortic vessel wall is segmented into cross-sections, and the segmentation contour lines of each cross-section are obtained. The target vessel wall is segmented at specified distances and with a specified number of segments to generate the contour lines of the outer and inner walls of the vessel.

[0078] 4. Output the coordinates of feature points on the aortic vessel wall contour line. For each contour line, generate at least one feature point starting from the same point, according to the same proportions. In one embodiment, this is ≥4 points. Output the coordinates of the feature points. It should be noted that the more feature points selected, the better. More feature points result in more guide lines, and the more similar the constructed vessel wall will be to that in CT scans. However, selecting one feature point and constructing one guide line is sufficient to roughly reconstruct the actual tortuous configuration of the aorta.

[0079] 5. For example Figure 4 As shown, guide lines for lofting are drawn based on the coordinates of the feature points. A feature point is selected on each contour, and guide lines are drawn from these feature points using spline curves for subsequent lofting.

[0080] 6. For example Figure 5 As shown, a solid structure is constructed by lofting the outer wall of the aorta based on the outline and guide lines.

[0081] 7. For example Figure 6 As shown, the aortic vessel wall is constructed by lofting and cutting according to the contour line and guide line of the aortic inner wall.

[0082] 8. Assign mesh seeds to the boundaries of the vessel wall entity. Assign a specified number of mesh seeds to the thickness direction, circumferential direction, and axial direction boundaries of the vessel wall entity.

[0083] 9. For example Figure 7 As shown, a structured hexahedral mesh of the blood vessel wall is generated by lofting. Following the mesh seed from the previous step, a structured hexahedral mesh is generated by lofting. When the blood vessel wall model is large and has many structural variations, the mesh cannot be generated all at once. Therefore, the model needs to be partitioned into many sub-regions, and the mesh is generated for each sub-region one by one according to the set scan or lofting boundaries and order. For the aortic wall containing branches, the branches and the aorta need to be separated into two parts, and each part is meshed separately.

[0084] 10. Perform a mesh check to ensure the mesh quality meets the computational requirements. Specifically:

[0085] 1) Calculate the included angle between every two faces of each tetrahedral element, ensuring that the included angle is not less than 10° and not greater than 160°;

[0086] 2) Calculate the aspect ratio for each hexahedral element to ensure that the aspect ratio is not greater than 10;

[0087] 3) Calculate the geometric deviation coefficient of each element, which is the ratio of the maximum gap between the element edge and the geometric edge to the element edge length, to ensure that the geometric deviation coefficient of no element exceeds 0.2;

[0088] When all three conditions above are met, the mesh quality of all units of the individualized blood vessel wall meets the computational requirements.

[0089] The second part involves the generation of a mesh for the aorta containing branch vessels, as shown in Figure 1(b), using the following method:

[0090] 1. Obtain the aortic blood flow region with branching vessels from CT images. Starting from a set of seed points in the blood flow region, expand progressively to adjacent pixels based on grayscale similarity criteria until all target blood flow regions are reached. Afterwards, manually inspect the blood flow region generation, remove non-target areas, fill in gaps generated during generation, and finally smooth the entire region.

[0091] 2. For example Figure 8 As shown, the aortic blood flow domain with branching vessels expands outward to generate the aortic vessel wall region with branching vessels. For the blood flow domain generated in the previous step, the outermost layer of the blood flow domain is expanded outward along the thickness direction by a certain distance. This distance is generally 1-2 mm, but the thickness of the vessel wall varies at different locations. The expanded region contains both the blood flow domain and the vessel wall region. A Boolean subtraction operation needs to be performed on the expanded region and the blood flow domain to obtain the vessel wall region.

[0092] 3. For example Figure 9 As shown, the branch vessel wall is segmented into cross-sections, and the segmentation contour lines of each cross-section are obtained. The target branch vessel wall is segmented at specified distances and with a specified number of segments to generate the contour lines of the outer and inner walls of the vessel.

[0093] 4. Output the coordinates of feature points on the contour lines of the branch vessel walls. For each contour line, generate at least one feature point starting from the same point, according to the same proportions. In one embodiment, at least four feature points are selected, and the coordinates of the feature points are output. It should be noted that the more feature points selected, the better. More feature points result in more guide lines, and the more similar the constructed vessel wall is to that in CT scans. However, even selecting only one feature point and constructing one guide line is sufficient to reflect the tortuous configuration of the aorta.

[0094] 5. For example Figure 10As shown, feature points are generated based on the contour lines of the branch vessels, and guide lines for scanning are drawn. For each contour line on the branch vessels, at least one feature point is generated from the same starting point, according to the same proportion. In one embodiment, at least four feature points are selected, and the coordinates of the feature points are output. A feature point is selected on each contour, and these feature points are used to draw guide lines using spline curves for subsequent scanning.

[0095] Based on the completed solid reconstruction of the aortic lateral wall, the following steps are performed:

[0096] 6. For example Figure 11 As shown, the outer wall of the branch vessel is scanned based on the outline and guide line to complete the construction of the outer wall of the branch vessel.

[0097] 7. For example Figure 12 As shown, the branch vessel wall is constructed by scanning and cutting according to the contour line and guide line of the inner wall of the branch vessel.

[0098] After the above two steps, the aortic inner wall is cut in a tracing manner.

[0099] Finally, a structured hexahedral mesh of the aortic vessel wall, including branching vessels, was generated. Figure 13 As shown, the branching part is structured, while the aortic part is layered and unstructured, that is, generating regular hexahedral meshes for complex three-dimensional entities such as the pore-filled and branched blood vessel walls.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for generating a structured hexahedral mesh for individualized blood vessel walls, the method comprising: Step s1: When the target aorta has no branches, proceed to the solid construction step of the aorta wall; otherwise, proceed to the solid construction step of the aorta wall and the solid construction step of each branch wall. Step s2: Assign mesh seeds to each boundary of the vessel wall entity, and generate a structured hexahedral mesh of the vessel wall by lofting or scanning; Step s3: Perform a mesh check by calculating the included angle, aspect ratio coefficient, and geometric deviation coefficient to ensure that the mesh quality meets the calculation requirements; The solid construction step of the aortic vessel wall in step s1 includes: Step 1: Obtain the target aortic blood flow region from the CT image; Step 2: Expand the aortic blood flow area outward to generate the aortic vessel wall region; Step 3: Divide the aortic vessel wall region into cross sections and obtain the section outline of each cross section; Step 4: For each segmentation contour line, obtain at least one feature point according to the same proportion, and output the coordinates of each feature point; Step 5: Draw the corresponding guide line using spline curves for each feature point obtained; Step 6: Loft the solid structure based on the outline and guide line of the outer wall of the aorta to complete the solid construction of the outer wall of the aorta; Loft cut the inner wall of the aorta based on the outline and guide line to complete the solid construction of the aorta. Step s2 includes: The thickness, circumferential, and axial boundaries of the vessel wall are assigned a specified number of mesh seeds. When the target aorta has no branches, a layered structured hexahedral mesh is generated by lofting. When the target aorta has branches, a layered hexahedral mesh is generated by aortic lofting, and a layered structured hexahedral mesh is generated by branch scanning.

2. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, Step 1 includes: Starting from a set of seed points in the blood flow region, the algorithm gradually expands to adjacent pixels based on the similarity of gray levels until it grows to all target blood flow region areas. Remove blood basins from non-target areas and fill in the gaps created during generation; Smooth the entire area.

3. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, Step 2 includes: The outermost layer of the blood flow domain is expanded outward by a set distance in the thickness direction. The expanded area includes the blood flow domain. A Boolean subtraction operation is performed on the expanded area and the blood flow domain to obtain the blood vessel wall region.

4. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, Step 3 includes: The aortic vessel wall region is divided according to a specified distance and a specified number of segments, generating the outline of the outer wall of the aorta and the outline of the inner wall of the aorta.

5. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, The solid construction step of each branch vessel wall in step s1 includes: Step 1: Obtain the target aortic blood flow region with branching vessels from the CT image; Step 2: Select the blood flow area of ​​the aorta and expand it outward to generate the aortic vessel wall region; Step 3: Divide the aortic vessel wall into cross-sections and obtain the cross-sectional outline of each cross-section; Step 4: For each segmentation contour line, obtain at least one feature point according to the same proportion, and output the coordinates of each feature point; Step 5: Select feature points from each contour line and draw the corresponding guide lines using spline curves; Step 6: Loft the solid structure based on the outline and guide lines of the aortic outer wall to complete the solid construction of the aortic vessel wall; Step 7: Expand the aortic blood flow area with branched vessels outward to generate the aortic vessel wall region with branched vessels; Step 8: Perform steps 9 through 12 sequentially on the wall of each branch vessel: Step 9: Divide the branch vessel wall into cross sections and obtain the section outline of each cross section; Step 10: Output the coordinates of feature points on the contour line of the branch vessel wall; Step 11: Draw the scanning guide line based on the feature points of the branch vessel outline; Step 12: Scan according to the outline and guide line of the outer wall of the branch vessel. The scanning start point is the selected outer wall outline, and the scanning end point is the outer wall of the aorta, thus completing the solid construction of the outer wall of the branch vessel; Scan and cut according to the outline and guide line of the inner wall of the branch vessel to complete the solid construction of the branch vessel wall. Step 13: Loft the solid structure based on the contour line and guide line of the aortic inner wall to complete the solid construction of the aortic vessel wall.

6. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, Step s2 further includes: dividing the vascular wall entity whose size and / or structural changes meet the set requirements into multiple sub-regions, and performing layout and scanning according to the set layout or scanning boundaries and order.

7. The method for generating a structured hexahedral mesh for individualized blood vessel walls according to claim 1, characterized in that, Step s3 includes: For each tetrahedral element, calculate the included angle between every two faces to ensure that the included angle is not less than 10° and not greater than 160°. Calculate the aspect ratio for each hexahedral element to ensure that the aspect ratio is no greater than 10. Calculate the geometric deviation coefficient for each element, which is the ratio of the maximum gap between the element edge and the geometric edge to the element edge length, ensuring that no element has a geometric deviation coefficient exceeding 0.2; When all three conditions above are met, the mesh quality of the individualized blood vessel wall meets the computational requirements.

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