Methods, apparatus, equipment, and media for calculating the mainstream direction vector based on the centerline.

Abstract

This application provides a method for calculating the mainstream direction vector based on the centerline, comprising: dividing a three-dimensional model of a blood vessel into a mesh to obtain a mesh structure corresponding to the blood vessel; the mesh structure includes multiple mesh cells; the three-dimensional model includes a model obtained by three-dimensional reconstruction of a blood vessel image; for any mesh cell, traversing multiple centerline nodes extracted based on the three-dimensional model to determine a target centerline node matching the mesh cell; the target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh cell is less than a preset distance; obtaining a first tangent vector and a second tangent vector; and determining the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector. This application also provides an apparatus, device, and storage medium for calculating the mainstream direction vector based on the centerline.

Description

Technical Field

[0001] This application relates to, but is not limited to, the field of next-generation information technology, and in particular to a method, apparatus, device, and storage medium for calculating the mainstream direction vector based on a centerline. Background Technology

[0002] In the field of bioengineering, especially in the context of the integration of medicine and artificial intelligence, research on cardiovascular diseases can reduce certain symptoms to physical phenomena. Analyzing such problems often requires obtaining various parameters of the blood vessels and then using computer numerical simulations to analyze the pathological conditions.

[0003] For example, in related technologies, before analyzing pathological conditions using computer numerical simulation, it is necessary to determine the mainstream direction of the blood vessel wall; this application provides a method for calculating the mainstream direction vector based on the centerline. Summary of the Invention

[0004] This application provides a method, apparatus, device, and storage medium for calculating the mainstream direction vector based on a centerline.

[0005] The technical solution of this application embodiment is implemented as follows:

[0006] The 3D model of the blood vessel is meshed to obtain the corresponding mesh structure; the mesh structure includes multiple mesh elements; the 3D model includes the model obtained by 3D reconstruction of the blood vessel image;

[0007] For any given mesh cell, traverse multiple centerline nodes extracted from the 3D model to determine the target centerline node that matches the mesh cell; wherein, the target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh cell is less than a preset distance;

[0008] Obtain the first tangent vector and the second tangent vector; wherein, the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node;

[0009] Based on the first and second tangent vectors, the mainstream direction vector of the mesh element is determined.

[0010] A device for calculating the mainstream direction vector based on the centerline, the device comprising:

[0011] The processing module is used to mesh the 3D model of blood vessels to obtain the mesh structure corresponding to the blood vessels; wherein, the mesh structure includes multiple mesh units; the 3D model includes the model obtained by 3D reconstruction of the blood vessel image;

[0012] The traversal module is used to traverse multiple centerline nodes extracted from the 3D model for any given mesh cell to determine the target centerline node that matches the mesh cell. The target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh cell is less than a preset distance.

[0013] The processing module is used to obtain a first tangent vector and a second tangent vector; wherein the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node;

[0014] The processing module is used to determine the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector.

[0015] This application provides a device for calculating the mainstream direction vector based on the centerline. The device for calculating the mainstream direction vector based on the centerline includes: a processor, a memory, and a communication bus.

[0016] The communication bus is used to implement communication connections between the processor and memory;

[0017] The processor executes a program stored in memory that calculates the main direction vector based on the centerline, in order to implement the steps of the method described above for calculating the main direction vector based on the centerline.

[0018] This application provides a storage medium that stores one or more programs, which can be executed by one or more processors to implement the steps of the above-described method for calculating the mainstream direction vector based on the centerline.

[0019] This application provides a method, apparatus, device, and storage medium for calculating the mainstream direction vector based on the centerline. The method involves meshing a 3D model of a blood vessel to obtain a corresponding mesh structure. The mesh structure includes multiple mesh elements. The 3D model includes a model obtained by 3D reconstruction of a blood vessel image. For any mesh element, multiple centerline nodes extracted from the 3D model are traversed to determine a target centerline node matching the mesh element. The target centerline node has the same region value as the mesh element, and is the node whose distance to the mesh element is less than a preset distance among the multiple centerline nodes. A first tangent vector and a second tangent vector are obtained. The first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. Based on the first and second tangent vectors, the mainstream direction vector of the mesh element is determined. In other words, this application, by using the centerline of the blood vessel, searches for the tangent vectors of the nodes forming the centerline corresponding to the surface mesh of the mesh structure to complete the calculation of the mainstream direction vector based on the centerline. Attached Figure Description

[0020] Figure 1 An exemplary schematic diagram illustrating the mismatch between the surface mesh and the centerline node at a bifurcation point, provided for this application;

[0021] Figure 2 An exemplary schematic diagram illustrating the mismatch between the surface mesh and the centerline node at a branch with a larger branch angle, provided for this application;

[0022] Figure 3 A schematic diagram of the region affected by the correction when matching the mainstream direction vector of the surface mesh at the Y-shaped bifurcation provided in this application;

[0023] Figure 4 A schematic diagram illustrating the correction of the direction vector at the Y-shaped bifurcation provided in this application;

[0024] Figure 5 A flowchart illustrating the method for calculating the mainstream direction vector based on the centerline, provided in an embodiment of this application;

[0025] Figure 6 This is a schematic diagram of the model preprocessing process provided in the embodiments of this application;

[0026] Figure 7 This is a schematic diagram of model mesh generation - surface mesh provided in an embodiment of this application;

[0027] Figure 8 A schematic diagram of the centerline node provided in the embodiments of this application;

[0028] Figure 9 This is a schematic diagram of segmentation markers and regions provided in the embodiments of this application;

[0029] Figure 10 This is a schematic diagram of a vascular model reconstructed from CT scans, provided as an embodiment of this application.

[0030] Figure 11 This is a schematic diagram illustrating the modulus traversal and shortest modulus node search provided in the embodiments of this application;

[0031] Figure 12 A schematic diagram of the matching vectors for the centerline nodes of the surface mesh provided in this application embodiment;

[0032] Figure 13 This is a schematic diagram of a loop provided in an embodiment of this application;

[0033] Figure 14 This is a schematic diagram of parent node loop and branch node search provided in an embodiment of this application;

[0034] Figure 15 This is a schematic diagram of intravascular APS calculation provided in an embodiment of this application;

[0035] Figure 16 A schematic diagram of the main direction vectors provided in the embodiments of this application;

[0036] Figure 17 A schematic diagram of the bifurcation region mainstream direction vector before optimization, provided in an embodiment of this application;

[0037] Figure 18 A schematic diagram showing the optimized mainstream direction vector of the bifurcation region provided in an embodiment of this application;

[0038] Figure 19 This is a schematic diagram of the APS results of a certain coronary artery branch provided in an embodiment of this application;

[0039] Figure 20 A schematic diagram of the device for calculating the mainstream direction vector based on the centerline provided in this application embodiment;

[0040] Figure 21 This application provides a schematic diagram of the structure of a device for calculating the mainstream direction vector based on the centerline. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0042] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0043] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0044] The device for calculating the mainstream direction vector based on the centerline provided in this application embodiment can be implemented as any device that calculates the mainstream direction vector based on the centerline, such as a laptop, tablet, desktop computer, mobile device (e.g., personal digital assistant, dedicated messaging device), or intelligent robot, or as a server. The following will describe exemplary applications of the device for calculating the mainstream direction vector based on the centerline.

[0045] For example, the flow of blood in blood vessels can be reduced to a typical fluid dynamics problem. After obtaining the parameters and defining the initial conditions, commercial computational fluid dynamics (CFD) software can usually be used to obtain and analyze data that are of interest to doctors and researchers.

[0046] In related technologies, classical flow problems often require the acquisition of various physical quantities. Most physical quantities in fluid mechanics are vectors (such as pressure and velocity). For a given physical quantity of interest, due to its vector nature, its magnitude and direction need to be calculated separately. While the magnitude and direction of some physical quantities are standardized, for some special quantities that require manual definition, additional vectors may be needed to assist in the calculation.

[0047] This application provides a method for calculating the mainstream direction vector based on the centerline, which involves searching and matching the vessel wall micro-units with the centerline nodes. Using the calculated mainstream direction vector, it can be conveniently applied to the calculation of other physical quantities of interest in the medical field, such as axial plaque stress (APS). This algorithm is typically affected by the geometric features of the blood vessel; see [link to relevant documentation]. Figure 1 and Figure 2 As shown, inaccurate matching occurs in certain areas at the branch points, where N1 is a normally matching node, N1' is a node with an abnormal match, and TAN1 and TAN1' are the tangent vectors of the centerline nodes, respectively. The inventors of this application discovered this during experiments, see [link to relevant documentation]. Figure 3 As shown, the mainstream direction of calculation may appear at the Y-shaped bifurcation of the blood vessel. To address the issue of uneven transition, this application further refines the direction vector at the Y-shaped bifurcation of the blood vessel during the determination of the mainstream direction of the vessel wall, thereby smoothing the mainstream direction vector in a specific region. The corrected effect is as follows: Figure 4 As shown.

[0048] This application provides a method for calculating the mainstream direction vector based on a centerline. This method is applied to devices that calculate the mainstream direction vector based on a centerline. (See also...) Figure 5 As shown, the method includes:

[0049] Step 101: Mesh the 3D model of the blood vessel to obtain the mesh structure corresponding to the blood vessel.

[0050] The mesh structure includes multiple mesh units; the 3D model includes a model obtained by 3D reconstruction of the blood vessel image.

[0051] In this application embodiment, the vascular image includes, but is not limited to, images obtained by means of: images acquired by computed tomography (CT) technology, such as 4D-Computed Tomography (4D-CT) and Magnetic Resonance Imaging (MRI).

[0052] Here, the blood vessels in the vascular image can be reconstructed in three dimensions. This reconstruction can be performed using 3D reconstruction software, including but not limited to MITK, Mimics, Simpleware, and 3D-DOCTOR.

[0053] Once a 3D model of the blood vessel is obtained, a model preprocessing workflow is executed, which involves meshing the 3D model of the blood vessel to obtain the corresponding mesh structure. After receiving the preprocessing data, relevant information about the centerline nodes can also be obtained.

[0054] In a feasible scenario involving preprocessing and relevant information acquisition, see [link to relevant documentation]. Figure 6 As shown, the process of reconstructing a 3D model of blood vessels from vascular images such as CT images is further illustrated by meshing the 3D model to obtain a 3D mesh for fluid computation. Figure 7 As shown, this is used to replace the micro-units of the vessel wall in actual calculations. Furthermore, the vessel centerline is extracted based on the three-dimensional model of the blood vessel. See also... Figure 8 As shown, the centerline consists of several centerline nodes, which are discrete three-dimensional points. The relevant information for each centerline node includes node coordinates, tangent vector, region value variables, parent node number, and node position. For example, this relevant information is stored in a centerline information matrix A, which is m×n in size, where m is the number of nodes and n is the number of variables. During calculation, it is converted into a one-dimensional array. Accessing the array through the centerline node number allows retrieval of the relevant information for the matched node. For segmentation of the 3D blood vessel model and centerline, see [reference needed]. Figure 9 As shown, the model is divided into main branches and branches. A region value variable M_B is assigned to the segmented geometric model and centerline. M_B distinguishes between the main branches and branches (e.g., main branch is 1 and branch is 2). In subsequent processes, the region value variable M_B is used to handle mismatches between individual face meshes and centerline nodes. Figure 9 Nodes 5 and 23 are branch nodes; nodes 5, 7, 9, 11, and 15 are divided into one branch; nodes 23, 25, 27, 29, 31, 33, and 35 are divided into another branch; and the other nodes, including nodes 5 and 23, are divided into the main branch.

[0055] Here, for a given node, also called a child node, its parent node is the node closest to the child node along the direction opposite to blood flow. Specifically, the direction of blood flow refers to the direction from the proximal end of the blood vessel to the distal end. Each node on the centerline has a number, and the parent node index is the parent node's number. Each child node has a unique parent node index. For example, in this application, there are four node position values, each corresponding to a different position: 1 corresponds to the exit, 2 to the entrance, 3 to the bifurcation point, and 0 to the intermediate position. The remaining nodes outside the entrance and bifurcation points are considered intermediate positions.

[0056] In a feasible scenario, based on the acquired CT data, a stereolithography (STL) model of the coronary artery is reconstructed. The reconstructed model is as follows: Figure 10 As shown, after mesh generation and preprocessing, boundary conditions are set, initialization is performed, and CFD analysis is conducted in Computational Fluid Dynamics (CFD) software to obtain the flow field inside the coronary artery and the distribution of pressure and wall shear stress.

[0057] Step 102: For any mesh cell, traverse multiple centerline nodes extracted from the 3D model to determine the target centerline node that matches the mesh cell.

[0058] Among them, the target centerline node and the grid cell have the same area value, and the target centerline node is the node among multiple centerline nodes whose distance from the grid cell is less than a preset distance.

[0059] In this embodiment of the application, when the mesh structure corresponding to the blood vessel is obtained, for any mesh cell, also known as a surface mesh, multiple centerline nodes extracted based on the three-dimensional model are traversed to determine the target centerline node that matches the mesh cell. This step is regarded as the matching process between the surface mesh and the centerline node. The purpose of matching is to find the node with the same area value as the mesh cell and the distance between the node and the mesh cell is less than a preset distance from all centerline nodes, and use it as the target centerline node that matches the mesh cell.

[0060] Step 103: Obtain the first tangent vector and the second tangent vector.

[0061] Wherein, the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. In this embodiment, the node coordinates of the target centerline node are labeled N1, and the first tangent vector is labeled N1TAN; the node coordinates of the parent node of the target centerline node are labeled N2, and the second tangent vector is labeled N2TAN.

[0062] Step 104: Determine the mainstream direction vector of the mesh element based on the first tangent vector and the second tangent vector.

[0063] In this embodiment of the application, for any grid cell, if the target centerline node matching the grid cell is determined, the mainstream direction vector of the grid cell can be determined based on the first tangent vector and the second tangent vector.

[0064] The method for calculating the mainstream direction vector based on the centerline provided in this application involves dividing a three-dimensional model of a blood vessel into a mesh to obtain a mesh structure corresponding to the blood vessel. The mesh structure includes multiple mesh units. The three-dimensional model includes a model obtained by reconstructing a blood vessel image. For any mesh unit, multiple centerline nodes extracted from the three-dimensional model are traversed to determine a target centerline node matching the mesh unit. The target centerline node has the same region value as the mesh unit, and the target centerline node is the node among the multiple centerline nodes whose distance to the mesh unit is less than a preset distance. A first tangent vector and a second tangent vector are obtained, where the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. Based on the first and second tangent vectors, the mainstream direction vector of the mesh unit is determined. In other words, this application, by using the centerline of the blood vessel, searches for the tangent vectors of the nodes forming the centerline corresponding to the surface mesh of the mesh structure to complete the calculation of the mainstream direction vector based on the centerline.

[0065] In some embodiments of this application, step 104, based on the first tangent vector and the second tangent vector, determines the mainstream direction vector of the mesh element, which can be achieved through the following steps:

[0066] A11. Based on the node coordinates of the target centerline node, the node coordinates of the parent node, and the center coordinates of the mesh cell, generate the first weight coefficient corresponding to the first tangent vector and the second weight coefficient corresponding to the second tangent vector.

[0067] In this embodiment, the center coordinates of the grid cell are denoted as FN = (xfn, yfn, zfn), where xfn, yfn, and zfn are the three components of the coordinate. The first weighting coefficient is denoted as h1, and the second weighting coefficient is denoted as h2.

[0068] In this embodiment, based on the node coordinates N1 of the target centerline node, the node coordinates N2 of the parent node, and the center coordinates FN of the mesh cell, the first weight coefficient h1 corresponding to the first tangent vector and the second weight coefficient h2 corresponding to the second tangent vector are generated, which can be achieved by the following formula:

[0069] First, calculate the first vector FNN1, FNN1 = N1 - FN; calculate the second vector FNN2, FNN2 = N2 - FN;

[0070] Secondly, the modulus of FNN1 is denoted as ||FNN1|| and the size of ||FNN1|| is calculated; the modulus of FNN2 is denoted as ||FNN2|| and the size of ||FNN2|| is calculated.

[0071] Finally, h1 = ||FNN1|| / (||FNN1||+||FNN2||), h2 = ||FNN2|| / (||FNN1||+||FNN2||).

[0072] A12. Based on the first tangent vector, the first weight coefficient, the second tangent vector, and the second weight coefficient, determine the mainstream direction vector.

[0073] In this embodiment, the mainstream direction vector is labeled FNTAN. Based on the first tangent vector N1TAN, the first weight coefficient h1, the second tangent vector N2TAN, and the second weight coefficient h2, the mainstream direction vector FNTAN is determined using the following formula:

[0074] FNTAN=N1TAN×h1+N2TAN×h2.

[0075] It can be seen that the mainstream direction vector FNTAN is a linear combination of N1TAN, N2TAN, h1 and h2. Among them, h1 and h2 are relaxation factors, which can make the numerical calculation results of the tangent vector more reasonable.

[0076] In some embodiments of this application, step 102, which involves traversing multiple centerline nodes extracted from the 3D model for any given mesh cell, to determine the target centerline node that matches the mesh cell, can be achieved through the following steps:

[0077] B21. Set the initial distance.

[0078] In this embodiment of the application, the initial distance is marked as min_d, also known as the initial shortest distance.

[0079] B22. During the traversal, for the current centerline node to be matched among multiple centerline nodes, if the current centerline node to be matched has the same region value as the grid cell, the target distance between the grid cell and the current centerline node to be matched is obtained based on the node coordinates of the current centerline node to be matched and the center coordinates of the grid cell.

[0080] In this embodiment, during the aforementioned matching process, the principle for matching the face mesh with the centerline node is to find the centerline node that is closest to the current face mesh and has the same region value. The following parameters are initialized: min_d, i, and note. Here, min_d stores the shortest distance between the face mesh and the centerline node, i is the centerline node number read during the traversal, note stores the centerline node number closest to the current face mesh, and the number of iterations is controlled by the number of centerline nodes m. Using any face mesh as the matching reference target, the centerline nodes are traversed for matching, see [link to relevant documentation]. Figure 11 As shown, perform a modulo-length traversal and a search for the shortest modulo-length node. Figure 12In this context, FN represents the vector representation of the center coordinates of the surface grid.

[0081] In this embodiment of the application, the target distance is the length of a vector, which is usually measured by the vector norm of the vector space. For example, the p-norm (e.g., the 2-norm) can be used. Understandably, when this application involves distance calculation, the 2-norm can be used for measurement, which is the distance in the usual sense (i.e., the magnitude).

[0082] B23. If the target distance is less than the initial distance, assign the target distance to the initial distance, search for the next matching centerline node among multiple centerline nodes until the traversal of multiple centerline nodes is completed, and determine the centerline node with the smallest distance from the grid cell as the target centerline node.

[0083] Here, if the target distance is less than the initial distance, the target distance is assigned to the initial distance, and the centerline node to be matched is determined to be the centerline node closest to the grid cell among all the centerline nodes currently traversed. The next centerline node to be matched among multiple centerline nodes is searched until the traversal of multiple centerline nodes is completed, and the centerline node with the smallest distance from the grid cell is determined as the target centerline node.

[0084] In this embodiment, during the traversal, for the current centerline node to be matched, it is first determined whether the region value of the mesh cell and the current centerline node to be matched are the same (i.e., M_B1 = M_B2?). If they are the same, the coordinates N1 of the current centerline node to be matched are read, the vector FNN1 (FNN1 = N1 - FN) is defined, and the magnitude ||FNN1|| is calculated. If ||FNN1|| is less than min_d, ||FNN1|| is assigned to min_d, and the number i of the current centerline node to be matched is assigned to note. If the region values ​​are different, the centerline node is skipped, and the next centerline node is searched directly. Until the traversal is completed, the coordinates of the centerline node with the same region value closest to the current face mesh are read through note and recorded as N1.

[0085] Furthermore, this application can also correct the mainstream direction vector for problems that may occur in areas with complex geometric features. In the embodiments of this application, the correction targets include the mainstream direction vector of the surface mesh at the bifurcation point, such as the mainstream direction vector of the mesh cells within a preset distance range downstream of the bifurcation at a Y-shaped bifurcation point, thereby improving the accuracy of matching in certain areas at the branch.

[0086] In some embodiments of this application, after step 104 determines the mainstream direction vector of the mesh element based on the first tangent vector and the second tangent vector, the following steps may also be performed:

[0087] If the grid cell is a grid cell located within a preset distance downstream of the bifurcation among multiple grid cells, the corrected mainstream direction vector of the grid cell is obtained based on the tangent vector of the centerline node at the bifurcation and the mainstream direction vector.

[0088] In some embodiments of this application, the corrected mainstream direction vector of the mesh element is obtained based on the tangent vector and mainstream direction vector of the centerline node at the bifurcation point, which can be achieved by the following formula:

[0089] The corrected mainstream direction vector is denoted as VECT, where VECT = the original mainstream direction vector FNTAN × the third weight coefficient + the tangent vector VECT_A at the bifurcation point × the fourth weight coefficient.

[0090] The sum of the third and fourth weighting coefficients is 1.

[0091] Here, the closer the target centerline node of the mesh cell is to the centerline node at the bifurcation, the larger the fourth weight coefficient.

[0092] Furthermore, the third weighting coefficient can be calculated using the following formula:

[0093] The third weight coefficient is labeled fac1, where fac1 = count / (max_count + 1); or;

[0094] fac1 = a + (1-a) × count / (max_count + 1); where count is the number of nodes traversed when shortening the distance along multiple centerline nodes from the target centerline node to the center node of the bifurcation, max_count is the preset maximum number of restricted nodes traversed when shortening the distance along multiple centerline nodes, and a is a reference coefficient.

[0095] As described above, this application can correct the mainstream direction vector of the mesh cells in two stages during the correction process: Stage 1, limiting the optimization range; Stage 2, correcting the mainstream direction vector. The following examples further illustrate these two stages:

[0096] Phase 1, Limiting the Optimization Scope: See [link / reference] Figure 13The diagram shows the process of optimizing the mainstream direction vector of the surface mesh at the Y-shaped bifurcation. Here, taking the optimization of the tangent vector of the surface mesh within a certain range downstream of the bifurcation as an example, the limitation of the optimization range is achieved through iterative looping. After determining the aforementioned mainstream direction vector FNTAN, the loop is initialized: for the aforementioned current surface mesh, the centerline node it matches is denoted as N1; the flag value is set to 1, where flag is a variable that controls the end of the loop; the count is set to 0, where count is the number of iterations; the maximum number of iterations, max_count, is set; the iteration begins after initialization.

[0097] In each iteration, firstly, the node information array is accessed using the current point N1's index to obtain the node's position value (position values ​​include 0, 1, 2, and 3). The current node's position is then determined, and different operations are performed based on the position: ① If the node is the entry point, the loop ends; ② If the node is a bifurcation point, its tangent vector VECT_A is read from the node information array, the loop ends, and the flag is set to 0; ③ If the node is the middle position, the parent node's index is read from the node information array, and N1 is updated with the parent node's index (i.e., the parent node of this iteration is set as the current node of the next iteration), while the iteration count is incremented by 1. If operation ③ is performed continuously during the iteration process, the iteration count continues to accumulate. When the iteration count exceeds the maximum iteration count max_count, the loop ends. Figure 14 As shown. After the loop ends, the flag value is used to determine whether to optimize the tangent vector of the face mesh: if the flag value is 0, the mainstream direction vector is optimized according to the number of iterations; if the flag value is 1, no optimization is performed. From the above iterative process, it can be seen that optimization is only performed on the mainstream direction vector of the mesh cells located within a preset distance downstream of the bifurcation when the number of nodes between nodes is less than the maximum number of nodes, max_count. This approach limits the optimization area to a certain range.

[0098] Phase Two: Correcting the Mainstream Direction Vector: This application aims to optimize the mainstream direction components of the surface mesh at the Y-shaped bifurcation, making the vector changes of the surface mesh at the Y-shaped bifurcation smoother. A weighted average is calculated using the tangent vector at the bifurcation point and the mainstream direction vector of the current surface mesh. In addition to selecting surface meshes within a suitable range, the iteration count after the loop ends also reflects the distance of the current surface mesh from the bifurcation. The applicant found in experiments that the closer to the bifurcation point, the greater the influence of the bifurcation, and the larger the weighting coefficient of the tangent vector at the bifurcation point should be. Therefore, the iteration count can be used to calculate the weighting coefficient.

[0099] After Phase 1 execution is complete and flag = 0, the weighting coefficient fac1 and the fourth weight coefficient, labeled fac2, are calculated based on the iteration count. The final corrected vector expression is: VECT = FNTAN × fac1 + VECT_A × fac2. The calculation of fac1 and fac2 has the following two constraints: the larger count is, the larger fac1 is; fac1 and fac2 are both positive numbers and their sum equals 1; for example: fac1 = count / (max_count + 1), fac2 = 1 - fac1. To further enhance the influence of the bifurcation point tangent vector, the weighting coefficients can be equal to: fac1 = a + (1 - a) × count / (max_count + 1), fac2 = 1 - fac1, where the reference coefficient a ∈ (0, 1).

[0100] In a feasible scenario where the mainstream direction vector can be calculated based on the centerline, acute coronary syndrome (ACS) is one of the critical medical conditions, and coronary atherosclerotic plaque rupture is the leading cause of ACS. Studies on coronary plaque rupture have revealed that the location of high wall shear stress (WSS) does not completely coincide with the rupture site, implying that WSS is not the primary factor causing plaque rupture. According to equation (1), in a laminar flow state, the surface force on the fluid particles of blood flow... It can be decomposed into normal stress. And tangential stress (where the normal stress is relatively small and can usually be ignored).

[0101]

[0102] See Figure 15 As shown, Projected onto the axial flow direction Obtain new feature parameters (vectors)

[0103]

[0104] Related studies have found that the sum of surface stresses (APS) along the axis in the flow field may be the main factor in plaque fracturing. According to equation (2), solving for APS requires obtaining two parameters. and Among them, surface force It can be obtained through commonly used CFD software by meshing, defining boundaries, and iterative calculation; while for the surface of the blood vessel wall... The main direction vector is obtained by discretizing the model to obtain a computational grid to replace the arbitrary tiny surface of the blood vessel wall. Then, using the algorithm of this application, the tangent vector of the node that makes up the center line of the corresponding blood vessel is searched to complete the calculation.

[0105] Due to the inherent bifurcation and geometric features of the blood vessel model, such as the concavity and convexity of the wall, a mismatch may occur in the tangent vectors of the centerline nodes corresponding to the search surface mesh. This can be effectively resolved using the correction methods in the algorithm. It is more accurate and reduces the error in the final calculated APS.

[0106] Using the method provided in this application, the coronary artery APS calculation process is as follows:

[0107] Step 1: Reconstruct an STL model of the cardiovascular system (e.g., coronary arteries) from the obtained CT data, such as... Figure 10 As shown, after mesh generation and preprocessing, setting boundary conditions, initialization, and computational fluid dynamics analysis in commercial CFD software, the flow field inside the blood vessel can be obtained, and the distribution of pressure and wall shear stress can be obtained.

[0108] Step 2: After the fluid calculation is completed, load and execute the mainstream direction vector calculation program. For a certain surface mesh, determine the centerline node matched each time, exclude the mismatched node, and return the centerline node number with the shortest modulus.

[0109] Step 3: Using the returned node numbers, read the tangent vectors of the centerline node and its parent node, calculate the magnitude of each, and then calculate the corresponding mainstream direction vector of the mesh surface using a weighted average. like Figure 16 As shown.

[0110] Step 4: Use a loop to determine if the node is close to the centerline bifurcation point and whether further optimization is necessary. If it is within the affected range, correct the direction vector calculated in Step 3 using the correction coefficient and the tangent vector of the bifurcation point. Otherwise, no operation will be performed, such as Figure 17 and Figure 18 As shown.

[0111] The corresponding mainstream direction vector is obtained after searching and correcting the matching of each face mesh. Size and its components are stored in custom variables specific to the CFD software.

[0112] In the CFD software, read the normal vector *nor* of the surface mesh and normalize *nor*. Read the pressure *p* of the surface mesh, and multiply the two to obtain the pressure vector *NORS*. Read the wall shear force, divide it by the area to obtain the wall shear stress *wss*, and sum the pressure vector and the wall shear stress vector to obtain the resultant force vector *SUMNS* of the surface mesh. According to the definition of APS (2), combine the mainstream direction vector of the surface mesh obtained from Step 2 (if necessary) and Step 4 (if necessary). The magnitude of APS is the dot product of SUMNS and this vector. The direction is the calculated mainstream direction. At this point, the APS calculation is complete. Repeat the above steps for all surface meshes to obtain the entire blood vessel APS vector field. Alternatively, dedicated post-processing software, such as CFDPOST, can be used to import the final fluid calculation results for visualization post-processing. Figure 19 As shown, the quantity and shape of APS vectors can be easily observed.

[0113] Embodiments of this application provide a device for calculating the mainstream direction vector based on the centerline. Figure 20 The apparatus 500 shown for calculating the main direction vector based on the centerline includes:

[0114] The processing module 501 is used to perform mesh generation on the three-dimensional model of the blood vessel to obtain the mesh structure corresponding to the blood vessel; wherein, the mesh structure includes multiple mesh units; the three-dimensional model includes the model obtained by three-dimensional reconstruction of the blood vessel image;

[0115] The traversal module 502 is used to traverse multiple centerline nodes extracted from the 3D model for any mesh cell to determine the target centerline node that matches the mesh cell; wherein, the target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh cell is less than a preset distance;

[0116] Processing module 501 is used to obtain a first tangent vector and a second tangent vector; wherein, the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node;

[0117] The processing module 501 is used to determine the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector.

[0118] In some embodiments of this application, the processing module 501 is used to generate a first weight coefficient corresponding to the first tangent vector and a second weight coefficient corresponding to the second tangent vector based on the node coordinates of the target centerline node, the node coordinates of the parent node, and the center coordinates of the grid cell.

[0119] The mainstream direction vector is determined based on the first tangent vector, the first weight coefficient, the second tangent vector, and the second weight coefficient.

[0120] In some embodiments of this application, the processing module 501 is used to obtain the corrected mainstream direction vector of the grid cell if the grid cell is a grid cell located within a preset distance range downstream of the bifurcation among multiple grid cells. This is based on the tangent vector and mainstream direction vector of the centerline node at the bifurcation.

[0121] In some embodiments of this application, the processing module 501 is used to modify the mainstream direction vector as follows: the mainstream direction vector before modification × the third weight coefficient + the tangent vector of the bifurcation point × the fourth weight coefficient.

[0122] The sum of the third and fourth weighting coefficients is 1.

[0123] In some embodiments of this application, the closer the target centerline node of the mesh cell is to the centerline node at the bifurcation, the larger the fourth weighting coefficient.

[0124] In some embodiments of this application, the third weighting coefficient can be calculated using the following formula:

[0125] The third weight coefficient is labeled fac1, where fac1 = count / (max_count + 1); or;

[0126] fac1 = a + (1-a) × count / (max_count + 1); where count is the number of nodes traversed when shortening the distance along multiple centerline nodes from the target centerline node to the center node of the bifurcation, max_count is the preset maximum number of restricted nodes traversed when shortening the distance along multiple centerline nodes, and a is a reference coefficient.

[0127] In some embodiments of this application, the traversal module 502 is used to set an initial distance; during the traversal process, for the current centerline node to be matched among multiple centerline nodes, if the current centerline node to be matched has the same area value as the grid cell, the target distance between the grid cell and the current centerline node to be matched is obtained based on the node coordinates of the current centerline node to be matched and the center coordinates of the grid cell.

[0128] If the target distance is less than the initial distance, the target distance is assigned to the initial distance. The next centerline node to be matched among multiple centerline nodes is searched until the traversal of multiple centerline nodes is completed. The centerline node with the smallest distance from the grid cell is determined as the target centerline node.

[0129] The device for calculating the mainstream direction vector based on the centerline provided in this application involves dividing a three-dimensional model of a blood vessel into a mesh to obtain a mesh structure corresponding to the blood vessel. The mesh structure includes multiple mesh units. The three-dimensional model includes a model obtained by three-dimensional reconstruction of a blood vessel image. For any mesh unit, multiple centerline nodes extracted from the three-dimensional model are traversed to determine a target centerline node matching the mesh unit. The target centerline node has the same region value as the mesh unit, and the target centerline node is the node among the multiple centerline nodes whose distance to the mesh unit is less than a preset distance. A first tangent vector and a second tangent vector are obtained, where the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. Based on the first and second tangent vectors, the mainstream direction vector of the mesh unit is determined. In other words, this application, by using the centerline of the blood vessel, searches for the tangent vectors of the nodes forming the centerline corresponding to the surface mesh of the mesh structure to complete the calculation of the mainstream direction vector based on the centerline.

[0130] Embodiments of this application provide a device for calculating the mainstream direction vector based on the centerline. Figure 21 The device 600 shown, which calculates the main direction vector based on the centerline, includes a processor 601, a memory 602, and a communication bus 603. The communication bus 603 is used to establish a communication connection between the processor 601 and the memory 602. The processor 601 executes the program stored in the memory 602 for calculating the main direction vector based on the centerline, to achieve... Figure 1 The corresponding embodiment provides a method for calculating the mainstream direction vector based on the centerline.

[0131] A processor can be an integrated circuit chip with signal processing capabilities, such as a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, a general-purpose processor can be a microprocessor or any conventional processor.

[0132] The device for calculating the mainstream direction vector based on the centerline provided in this application embodiment obtains the corresponding mesh structure of the blood vessel by dividing the three-dimensional model of the blood vessel into a mesh. The mesh structure includes multiple mesh units. The three-dimensional model includes a model obtained by three-dimensional reconstruction of the blood vessel image. For any mesh unit, multiple centerline nodes extracted based on the three-dimensional model are traversed to determine the target centerline node that matches the mesh unit. The target centerline node has the same region value as the mesh unit, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh unit is less than a preset distance. A first tangent vector and a second tangent vector are obtained, where the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. Based on the first tangent vector and the second tangent vector, the mainstream direction vector of the mesh unit is determined. In other words, this application can complete the calculation of the mainstream direction vector based on the centerline by searching for the tangent vectors of the nodes that make up the centerline corresponding to the surface mesh of the mesh structure using the centerline of the blood vessel.

[0133] It should be noted that the specific implementation process of the steps executed by the processor in this embodiment can be referred to Figure 1 The implementation process of the method for calculating the mainstream direction vector based on the centerline provided in the corresponding embodiment will not be described in detail here.

[0134] The description of the apparatus in this application is similar to that of the method embodiments described above, and has similar beneficial effects, therefore, it will not be repeated. For technical details not disclosed in this apparatus embodiment, please refer to the description of the method embodiments of this application for understanding.

[0135] This application provides a storage medium storing executable instructions. When these executable instructions are executed by a processor, they cause the processor to perform the method provided in this application, for example... Figure 1 The method shown.

[0136] The storage medium provided in this application provides a mesh structure corresponding to a blood vessel by meshing a three-dimensional model of the blood vessel. The mesh structure includes multiple mesh units. The three-dimensional model includes a model obtained by reconstructing a blood vessel image. For any mesh unit, multiple centerline nodes extracted from the three-dimensional model are traversed to determine a target centerline node matching the mesh unit. The target centerline node has the same region value as the mesh unit, and the target centerline node is the node among the multiple centerline nodes whose distance from the mesh unit is less than a preset distance. A first tangent vector and a second tangent vector are obtained, where the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node. Based on the first and second tangent vectors, the mainstream direction vector of the mesh unit is determined. In other words, this application, by using the centerline of the blood vessel, searches for the tangent vectors of the nodes forming the centerline corresponding to the surface mesh of the mesh structure to complete the calculation of the mainstream direction vector based on the centerline.

[0137] In some embodiments, the storage medium may be a computer-readable storage medium, such as a ferromagnetic random access memory (FRAM), a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), flash memory, magnetic surface memory, optical disc, or a compact disk-read-only memory (CD-ROM); or it may be a device that includes one or any combination of the above-mentioned memories.

[0138] In some embodiments, executable instructions may take the form of a program, software, software module, script, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0139] As an example, executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file containing other programs or data, for example, in one or more scripts within a Hyper Text Markup Language (HTL) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files storing one or more modules, subroutines, or code sections). As an example, executable instructions may be deployed to execute on a single computing device, or on multiple computing devices located in one location, or on multiple computing devices distributed across multiple locations and interconnected via a communication network.

[0140] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A method for calculating the mainstream direction vector based on the centerline, characterized in that, The method includes: A three-dimensional model of a blood vessel is meshed to obtain a mesh structure corresponding to the blood vessel; wherein, the mesh structure includes multiple mesh elements; the three-dimensional model includes a model obtained by three-dimensional reconstruction of a blood vessel image; For any given mesh cell, multiple centerline nodes extracted from the 3D model are traversed to determine a target centerline node that matches the mesh cell. The target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance to the mesh cell is less than a preset distance. The region value is a region variable value assigned to the segmented 3D model and centerline nodes by dividing them into main branches and sub-branches. Obtain a first tangent vector and a second tangent vector; wherein, the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node; Based on the first tangent vector and the second tangent vector, the mainstream direction vector of the mesh cell is determined; The step of determining the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector includes: Based on the node coordinates of the target centerline node, the node coordinates of the parent node, and the center coordinates of the grid cell, a first weight coefficient corresponding to the first tangent vector and a second weight coefficient corresponding to the second tangent vector are generated. The mainstream direction vector is determined based on the first tangent vector, the first weight coefficient, the second tangent vector, and the second weight coefficient. After determining the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector, the method further includes: If the grid cell is a grid cell located within a preset distance range downstream of the bifurcation among the plurality of grid cells, the corrected mainstream direction vector of the grid cell is obtained based on the tangent vector of the centerline node at the bifurcation and the mainstream direction vector.

2. The method according to claim 1, characterized in that, The process of obtaining the corrected mainstream direction vector of the mesh element based on the tangent vector of the centerline node at the bifurcation and the mainstream direction vector includes: The corrected mainstream direction vector = the original mainstream direction vector × the third weighting coefficient + the tangent vector at the bifurcation point × the fourth weighting coefficient; The sum of the third weighting coefficient and the fourth weighting coefficient is 1.

3. The method according to claim 2, characterized in that, The closer the target centerline node matched by the grid cell is to the centerline node at the bifurcation, the larger the fourth weighting coefficient.

4. The method according to claim 2, characterized in that, The third weighting coefficient can be calculated using the following formula: The third weight coefficient is labeled fac1, where fac1 = count / (max_count + 1); or; fac1 = a + (1-a) × count / (max_count + 1); where count is the number of nodes traversed when shortening the distance along the multiple centerline nodes from the target centerline node to the center node of the bifurcation, max_count is a preset maximum number of nodes traversed when shortening the distance along the multiple centerline nodes, and a is a reference coefficient.

5. The method according to any one of claims 1 to 4, characterized in that, The step of traversing multiple centerline nodes extracted from the 3D model for any given mesh cell to determine the target centerline node matching the mesh cell includes: Set the initial distance; During the traversal, for the current centerline node to be matched among the multiple centerline nodes, if the current centerline node to be matched has the same region value as the grid cell, the target distance between the grid cell and the current centerline node to be matched is obtained based on the node coordinates of the current centerline node to be matched and the center coordinates of the grid cell. If the target distance is less than the initial distance, the target distance is assigned to the initial distance, and the next centerline node to be matched among the plurality of centerline nodes is searched until the traversal of the plurality of centerline nodes is completed. The centerline node with the smallest distance from the grid cell is determined as the target centerline node.

6. A device for calculating the mainstream direction vector based on the centerline, characterized in that, The device includes: The processing module is used to perform mesh generation on the three-dimensional model of the blood vessel to obtain the mesh structure corresponding to the blood vessel; wherein, the mesh structure includes multiple mesh elements; the three-dimensional model includes a model obtained by three-dimensional reconstruction of the blood vessel image; The traversal module is used to traverse multiple centerline nodes extracted from the 3D model for any given mesh cell to determine a target centerline node that matches the mesh cell. The target centerline node has the same region value as the mesh cell, and the target centerline node is the node among the multiple centerline nodes whose distance to the mesh cell is less than a preset distance. The region value is a region variable value assigned to the segmented 3D model and centerline nodes by dividing them into main branches and sub-branches. The processing module is used to obtain a first tangent vector and a second tangent vector; wherein the first tangent vector is the tangent vector of the target centerline node, and the second tangent vector is the tangent vector of the parent node of the target centerline node; The processing module is used to determine the mainstream direction vector of the mesh cell based on the first tangent vector and the second tangent vector; The processing module is used to generate a first weight coefficient corresponding to the first tangent vector and a second weight coefficient corresponding to the second tangent vector based on the node coordinates of the target centerline node, the node coordinates of the parent node, and the center coordinates of the grid cell. The mainstream direction vector is determined based on the first tangent vector, the first weight coefficient, the second tangent vector, and the second weight coefficient. The processing module is configured to, if the grid cell is a grid cell located within a preset distance range downstream of the bifurcation among the plurality of grid cells, obtain the corrected mainstream direction vector of the grid cell based on the tangent vector of the centerline node at the bifurcation and the mainstream direction vector.

7. A device for calculating the mainstream direction vector based on the centerline, characterized in that, The device for calculating the mainstream direction vector based on the centerline includes: Memory, used to store executable instructions; A processor is configured to execute executable instructions stored in the memory to implement the method for calculating the mainstream direction vector based on the centerline as described in any one of claims 1 to 5.

8. A storage medium, characterized in that, The device stores executable instructions that, when executed, cause the processor to perform the method for calculating the mainstream direction vector based on the centerline as described in any one of claims 1 to 5.

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