Method and device for analyzing force-induced injury of optic nerve after human head is struck

Abstract

Method and device for analyzing the force injury of the optic nerve after the human head is struck, which saves a large amount of modeling time and greatly reduces the possibility of non-convergence of the solution caused by poor mesh generation effect, provides the possibility for later clinical application, is closer to the actual situation of patients, and has the advantages of high credibility and low cost. The method includes: (1) constructing a finite element analysis mesh model of three-dimensional important tissue organs of the human head; (2) building a biomechanical material parameter database of important tissue organs of the head; (3) constructing tissue organ entities according to the mesh model and performing biomechanical calculations on the optic nerve.

Description

Technical Field

[0001] The present invention relates to the technical field of medical images and biomechanical simulation analysis, and particularly relates to a method for analyzing the force and damage of the optic nerve after a human head is struck, and a device for analyzing the force and damage of the optic nerve after a human head is struck. Background Art

[0002] The optic nerve of the human eye is a tissue connecting the eyeball and the human brain, consisting of nerve fiber bundles composed of fibrous connective tissue and glial cells, and has the function of conducting visual impulses. When the skull is hit by an external force, clinically, problems such as visual impairment and visual defects usually occur, which are all related to the damage of the optic nerve.

[0003] Usually clinically, doctors can only analyze the damaged condition of the patient's optic nerve through CT / MR images taken afterwards, and only information such as fractures and organ lesions can be seen in the medical images. It is impossible to accurately observe the compression and damage caused by the stress generated by the elastic deformation of the skull or soft tissues to the optic nerve during the process of the human head being stressed, which poses a great challenge to doctors in choosing treatment plans. Summary of the Invention

[0004] To overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a method for analyzing the force and damage of the optic nerve after a human head is struck, which saves a large amount of modeling time and greatly reduces the possibility of non-convergence of the solution caused by poor mesh generation effect, provides the possibility for later clinical application, is closer to the actual situation of patients, and has the advantages of high credibility and low cost.

[0005] The technical solution of the present invention is: This method for analyzing the force and damage of the optic nerve after a human head is struck includes the following steps:

[0006] (1) Complete the construction of a finite element analysis mesh model of three-dimensional important tissue organs of the human head. Based on medical images, establish a precise model of important tissue organs of the human head. The model needs to clearly show the surface contours of each tissue organ and the mutual adhesion or intersection relationships existing between the organs. Use medical image processing software to label the tissue organs in the CT / MR images. After three-dimensional reconstruction of the labeled tissue organ regions, perform smoothing processing;

[0007] (2) Build a biomechanical material parameter database for important tissue organs of the head to obtain the mass, density, Young's modulus, and Poisson's ratio of important tissue organs of the human head. Among them, Young's modulus represents the ability of the material to resist deformation, and Poisson's ratio reflects the magnitude of the transverse deformation of the material;

[0008] (3) Construct the tissue and organ entities based on the grid model and perform biomechanical calculations on the optic nerve. Use the Gaussian function to simulate the buffering effect of the head skin on the force. The force function is defined as f = 100 * Gauss(t - 30), where Set the force application area on the skull surface according to the actual impact situation of the patient, and apply fixed constraints at the bottom and back of the head model. The force application direction is defined by the vector in the Cartesian coordinate system.

[0009] The present invention constructs the head organ entities through the reverse modeling process of constructing geometric entities from the grid model, omits the step of meshing after importing the 3D model, saves a large amount of modeling time, and greatly reduces the possibility of non-convergence in the solution due to poor mesh generation effect, providing the possibility for later clinical application. In addition, the human organ model is segmented and modeled based on real CT / MR data, and is closer to the actual situation of the patient compared with the simulation results of the existing standard head anatomical model, with the advantages of high credibility and low cost.

[0010] It also provides a device for analyzing the force damage of the optic nerve after the human head is struck, which includes:

[0011] A model construction module configured to complete the construction of the finite element analysis grid model of the three-dimensional important tissue and organs of the human head, establish an accurate model of the important tissue and organs of the human head according to medical images. The model needs to clearly show the surface contours of each tissue and organ and the mutual adhesion or intersection relationships existing between the organs. Use medical image processing software to label the tissue and organs in the CT / MR images, and after three-dimensional reconstruction of the labeled tissue and organ regions, perform smoothing processing;

[0012] A database construction module configured to construct a biomechanical material parameter database of the important tissue and organs of the head, and obtain the mass, density, Young's modulus, and Poisson's ratio of the important tissue and organs of the human head. Among them, Young's modulus represents the ability of the material to resist deformation, and Poisson's ratio reflects the magnitude of the transverse deformation of the material;

[0013] A biomechanical calculation module configured to construct tissue and organ entities based on the grid model and perform biomechanical calculations on the optic nerve. Use the Gaussian function to simulate the buffering effect of the head skin on the force. The force function is defined as f = 100 * Gauss(t - 30), where Set the force application area on the skull surface according to the actual impact situation of the patient, and apply fixed constraints at the bottom and back of the head model. The force application direction is defined by the vector in the Cartesian coordinate system. Description of the Drawings

[0014] Figure 1 It is a schematic diagram for constructing the finite element analysis grid model of the three-dimensional important tissue and organs of the human head.

[0015] Figure 2 Schematic diagram for building a biomechanical material parameter database of important head tissues and organs.

[0016] Figure 3 Schematic diagram for constructing tissue and organ entities based on a mesh model and performing biomechanical calculations on the optic nerve.

[0017] Figure 4 Schematic diagram for labeling tissue and organs in CT / MR medical images.

[0018] Figure 5 Schematic diagram of a mesh adaptive model.

[0019] Figure 6 Schematic diagram of the change of von Mises stress on the optic nerve with the length of the optic nerve when the nasal side is stressed.

[0020] Figure 7 Schematic diagram of the von Mises stress distribution at a certain moment when the upper orbit is stressed.

[0021] Figure 8 Schematic diagram of the skull displacement distribution at a certain moment when the upper orbit is stressed.

[0022] Figure 9 Schematic diagram of the process of a method for analyzing the force and damage of the optic nerve after the human head is struck according to the present invention. Detailed implementation manners

[0023] As Figure 9 shown, this method for analyzing the force and damage of the optic nerve after the human head is struck includes the following steps:

[0024] (1) Complete the construction of a finite element analysis mesh model of the three-dimensional important tissues and organs of the human head. Based on medical images, establish an accurate model of the important tissues and organs of the human head, and the model should clearly show the surface contours of each tissue and organ and the adhesion or intersection relationships between organs. Use medical image processing software to label the tissue and organs in CT / MR images, and after three-dimensional reconstruction of the labeled tissue and organ regions, perform smoothing processing;

[0025] (2) Build a biomechanical material parameter database of important head tissues and organs to obtain the mass, density, Young's modulus, and Poisson's ratio of the important tissues and organs of the human head. Among them, Young's modulus represents the ability of the material to resist deformation, and Poisson's ratio reflects the magnitude of the transverse deformation of the material;

[0026] (3) Construct tissue and organ entities based on the mesh model and perform biomechanical calculations on the optic nerve. Use the Gaussian function to simulate the buffering effect of the head skin on the force, and the force function is defined as f = 100 * Gauss(t - 30), where The force application area is set on the skull surface according to the actual impact situation of the patient, and fixed constraints are applied to the bottom and the back of the head model. The force application direction is defined by a vector in the Cartesian coordinate system.

[0027] In the present invention, the head organ entities are constructed through a reverse modeling process of constructing geometric entities from a mesh model, omitting the step of meshing after importing a 3D model, saving a large amount of modeling time and greatly reducing the possibility of non-convergence of the solution caused by poor mesh meshing effect, providing the possibility for later clinical application. In addition, the human organ model is segmented and modeled based on real CT / MR data. Compared with the simulation results of existing standard head anatomical models, it is closer to the actual situation of patients and has the advantages of high credibility and low cost.

[0028] As Figure 1 shown, preferably, in step (1), the annotation of tissue organs includes the optic nerve, skull, eyeball, extraocular muscle, tendon; during the annotation process, the contours of tissue organs are first annotated by means of threshold segmentation, linear interpolation, manual segmentation, etc., and then opening operation and closing operation are performed to remove unnecessary isolated points, burrs and internal cavities in the annotated area.

[0029] Preferably, in step (1), after smoothing, mesh data files are exported separately for different tissue organs, and the file contains the surface geometry and spatial position relationship of the 3D object.

[0030] Preferably, in step (2), the biomechanical parameters include the mass, density, Young's modulus, thermal conductivity, and constant pressure heat capacity of tissue organs.

[0031] As Figure 3 shown, preferably, step (3) includes the following sub-steps:

[0032] (3.1) Import the reconstructed 3D mesh data file into finite element analysis software, take the union of mutually adhering or intersecting tissue organs to reflect the contact relationship, then it is necessary to construct an entity for the area enclosed by the surface mesh, then perform the meshing of free tetrahedral meshes on the constructed entity, customize the mesh density of each organ, and finally define the closed force application area according to the edge texture of the model surface mesh;

[0033] (3.2) Perform adaptive processing on the mesh, shorten the calculation time while ensuring the available resolution and mesh quality by merging adjacent nodes and adjacent meshes of the mesh;

[0034] (3.3) Import the biomechanical material parameter database into the finite element analysis software, and assign different material properties to the tissue organ geometric entities after mesh adaptation in step (3.2);

[0035] (3.4) Use the Gaussian function to simulate the buffering effect of the head skin on force. The force function is defined as f = 100 * Gauss(t - 30), where And set the force application area on the skull surface according to the actual impact situation of the patient. Fixed constraints are applied at the bottom and back of the head model. The force application direction is defined by a vector in the Cartesian coordinate system;

[0036] (3.5) Set the analysis type to transient analysis, set the output step size to 10 ms, and add a parametric scan item to analyze the influence of different force application directions and different force application areas on the optic nerve; To improve the convergence and calculation speed of the calculation model, the PARDISO direct solver based on LU decomposition is selected;

[0037] (3.6) If the calculation model does not converge during the calculation, it is necessary to return to step (3.2) to adjust the mesh division; After the calculation is completed, select the von Mises stress, the first principal strain, the force application direction, and the displacement of the tissue organs as the analysis indicators. In addition, points are selected at both ends of the optic nerve to define a three-dimensional cross-section, which penetrates the entire optic nerve.

[0038] Preferably, in the step (3.6), the obtained results mainly include: 1) The variation relationships of the von Mises stress, the first principal strain, and the displacement on the optic nerve with the length of the optic nerve at any moment during the head impact process; 2) The influence of different impact areas and different impact directions on the optic nerve and other important tissue organs of the head; 3) The three-dimensional distribution maps of the von Mises stress, direction, and displacement on the skull at any moment; 4) The equivalent plastic deformation distribution map of the important tissue organs of the head.

[0039] Those of ordinary skill in the art can understand that all or part of the steps in implementing the method of the above embodiments can be completed by instructing relevant hardware through a program. The program can be stored in a computer-readable storage medium. When the program is executed, it includes the steps of the method of the above embodiments, and the storage medium can be: ROM / RAM, magnetic disk, optical disk, memory card, etc. Therefore, corresponding to the method of the present invention, the present invention also simultaneously includes a device for analyzing the force damage of the optic nerve after a human head is hit. This device is usually represented in the form of functional modules corresponding to the steps of the method. This device includes:

[0040] A model construction module, which is configured to complete the construction of a finite element analysis mesh model of the three-dimensional important tissue organs of the human head, establish an accurate model of the important tissue organs of the human head according to medical images. The model needs to clearly show the surface contours of each tissue organ and the mutual adhesion or intersection relationships existing between the organs. Use medical image processing software to label the tissue organs in the CT / MR images, and after three-dimensional reconstruction of the labeled tissue organ areas, perform smoothing processing;

[0041] A database construction module, which is configured to construct a biomechanical material parameter database for important head tissues and organs, obtaining the mass, density, Young's modulus, and Poisson's ratio of important head tissues and organs in the human body, where the Young's modulus represents the ability of the material to resist deformation, and the Poisson's ratio reflects the magnitude of the lateral deformation of the material;

[0042] A biomechanical calculation module, which is configured to construct tissue and organ entities according to the mesh model and perform biomechanical calculations on the optic nerve, using the Gaussian function to simulate the buffering effect of the head skin on force, and the force function is defined as f = 100 * Gauss(t - 30), where And set the force application area on the skull surface according to the actual impact situation of the patient, and apply fixed constraints to the bottom and back parts of the head model, and the force application direction is defined by the vector in the Cartesian coordinate system.

[0043] Preferably, in the model construction module, the annotation of tissue and organs includes the optic nerve, skull, eyeball, extraocular muscles, and tendons; during the annotation process, first use methods such as threshold segmentation, linear interpolation, and manual segmentation to annotate the contours of tissue and organs, and then perform opening and closing operations to remove unnecessary isolated points, burrs, and internal holes in the annotation area; after smoothing processing, export mesh data files for different tissue and organs respectively, and this file contains the surface geometry and spatial position relationship of three-dimensional objects.

[0044] Preferably, in the database construction module, the biomechanical parameters include the mass, density, Young's modulus, thermal conductivity, and constant-pressure heat capacity of tissue and organs.

[0045] Preferably, the biomechanical calculation module performs the following sub-steps:

[0046] (3.1) Import the reconstructed three-dimensional mesh data file into the finite element analysis software, take the union of the mutually adhering or intersecting tissue and organs to reflect the contact relationship, then it is necessary to construct entities for the areas surrounded by the surface meshes, and then perform the meshing of free tetrahedral meshes on the constructed entities, customize the mesh density of each organ, and finally define the closed force application area according to the edge texture of the model surface mesh;

[0047] (3.2) Perform adaptive processing on the mesh, by merging adjacent nodes and adjacent meshes of the mesh, shortening the calculation time while ensuring the available resolution and mesh quality;

[0048] (3.3) Import the biomechanical material parameter database into the finite element analysis software, and assign different material properties to the tissue and organ geometric entities after mesh adaptation in step (3.2);

[0049] (3.4) Use the Gaussian function to simulate the buffering effect of the head skin on force. The force function is defined as f = 100 * Gauss(t - 30), where And set the force application area on the skull surface according to the actual impact situation of the patient. Fixed constraints are applied at the bottom and the back of the head model, and the force application direction is defined by the vector in the Cartesian coordinate system;

[0050] (3.5) Set the analysis type to transient analysis, set the output step size to 10 ms, and add parametric scan items to analyze the influence of different force application directions and different force application areas on the optic nerve; To improve the convergence and calculation speed of the calculation model, the PARDISO direct solver based on LU decomposition is selected;

[0051] (3.6) If the calculation model does not converge during the calculation, it is necessary to return to step (3.2) to adjust the mesh division; After the calculation is completed, select von Mises stress, the first principal strain, the force application direction, and the tissue and organ displacement as the analysis indicators. In addition, select points at both ends of the optic nerve to define a three-dimensional cross-section to penetrate the entire optic nerve.

[0052] The above is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for analyzing the force-induced injury of the optic nerve after a human head is struck, characterized in that: It includes the following steps: (1) Complete the construction of a finite element analysis mesh model of the three-dimensional important tissue organs of the human head. Based on medical images, establish an accurate model of the important tissue organs of the human head. The model needs to clearly show the surface contours of each tissue organ and the mutual adhesion or intersection relationships existing between the organs. Use medical image processing software to label the tissue organs in the CT / MR images. After three-dimensional reconstruction of the labeled tissue organ regions, perform smoothing processing; (2) Build a biomechanical material parameter database for the important tissue organs of the head to obtain the mass, density, Young's modulus, and Poisson's ratio of the important tissue organs of the human head. Among them, Young's modulus represents the ability of the material to resist deformation, and Poisson's ratio reflects the magnitude of the lateral deformation of the material; (3)Construct the tissue and organ entities according to the grid model and perform biomechanical calculations on the optic nerve. Use the Gaussian function to simulate the buffering effect of the head skin on the force. The force function is defined as f = 100 * Gauss(t - 30), where And set the force application area on the skull surface according to the actual impact situation of the patient, and apply fixed constraints at the bottom and back of the head model. The force application direction is defined by the vector in the Cartesian coordinate system.

2. The method for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 1, wherein: In step (1), the labeling of tissue organs includes the optic nerve, skull, eyeball, extraocular muscles, and tendons. During the labeling process, first use threshold segmentation, linear interpolation, and manual segmentation methods to label the contours of the tissue organs, and then perform opening and closing operations to remove unnecessary isolated points, burrs, and internal cavities in the labeled areas.

3. The method for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 2, characterized in that: In step (1), after smoothing processing, export mesh data files for different tissue organs respectively. This file contains the surface geometry and spatial position relationships of three-dimensional objects.

4. The method for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 3, characterized in that: In step (2), the biomechanical parameters include the mass, density, Young's modulus, thermal conductivity, and constant-pressure heat capacity of the tissue organs.

5. The method for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 4, characterized in that: Step (3) includes the following sub-steps: (3.1) Import the reconstructed three-dimensional mesh data file into the finite element analysis software. Take the union of the mutually adhered or intersecting tissue organs to reflect the contact relationship. Then, it is necessary to construct a solid for the area surrounded by the surface mesh, and then perform tetrahedral mesh meshing on the constructed solid. Customize the mesh density of each organ. Finally, define the closed stress area according to the edge texture of the model surface mesh; (3.2) Perform adaptive processing on the mesh. By merging adjacent nodes and adjacent meshes of the mesh, shorten the calculation time while ensuring the available resolution and mesh quality; (3.3) Import the biomechanical material parameter database into the finite element analysis software, and assign different material properties to the geometric entities of the tissue organs after mesh adaptation in step (3.2); (3.4) Use the Gaussian function to simulate the buffering effect of the head skin on force. The force function is defined as f = 100 * Gauss(t - 30), where And the force application area is set on the skull surface according to the actual impact situation of the patient. Fixed constraints are applied at the bottom and the back of the head model, and the force direction is defined by the vector in the Cartesian coordinate system; (3.5) Set the analysis type to transient analysis, set the output step size to 10 ms, and add a parametric scan item to analyze the influence of different force directions and different force areas on the optic nerve. To improve the convergence and calculation speed of the calculation model, select the PARDISO direct solver based on LU decomposition; (3.6) If the calculation model does not converge during the calculation, it is necessary to return to step (3.2) to adjust the mesh division. After the calculation is completed, select von Mises stress, the first principal strain, the force direction, and the displacement of the tissue organs as analysis indicators. In addition, select points at both ends of the optic nerve to define a three-dimensional cross-section to penetrate the entire optic nerve.

6. The method for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 5, wherein: In the step (3.6), the obtained results include: 1) the variation relationships of von Mises stress, the first principal strain, and displacement on the optic nerve with the optic nerve length at any moment during the head impact process; 2) the influences of different impact regions and different impact directions on the optic nerve and other important tissue organs of the head; 3) the three-dimensional distribution diagrams of von Mises stress, direction, and displacement on the skull at any moment; 4) the equivalent plastic deformation distribution diagrams of important tissue organs of the head.

7. A device for analyzing the force-induced injury of the optic nerve after the human head is struck, characterized in that: It includes: a model construction module configured to complete the construction of a finite element analysis mesh model of three-dimensional important tissue organs of the human head, establish an accurate model of important tissue organs of the human head based on medical images, the model needs to clearly show the surface contours of each tissue organ and the mutual adhesion or intersection relationships existing between the organs, use medical image processing software to label the tissue organs in CT / MR images, and after three-dimensional reconstruction of the labeled tissue organ regions, perform smoothing processing; A database building module, configured to build a biomechanical material parameter database for important head organs, obtaining the mass, density, Young's modulus, and Poisson's ratio of important head organs in the human body, where the Young's modulus represents the ability of the material to resist deformation, and the Poisson's ratio reflects the magnitude of the lateral deformation of the material; a biomechanical calculation module, configured to construct tissue organ entities based on the mesh model and perform biomechanical calculations on the optic nerve, using the Gaussian function to simulate the buffering effect of the head skin on force, and the force function is defined as f = 100 * Gauss(t - 30), where And the force application area is set on the skull surface according to the actual impact situation of the patient, and fixed constraints are applied to the bottom and back parts of the head model, and the force application direction is defined by the vector in the Cartesian coordinate system.

8. The device for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 7, wherein: In the model construction module, the labeling of tissue organs includes the optic nerve, the skull, the eyeballs, the extraocular muscles, and the tendons; during the labeling process, first use threshold segmentation, linear interpolation, and manual segmentation methods to label the contours of the tissue organs, and then perform opening operation and closing operation to remove unnecessary isolated points, burrs, and internal holes in the labeled regions; after smoothing processing, export mesh data files for different tissue organs respectively, and this file contains the surface geometric shape and spatial position relationship of the three-dimensional object.

9. The device for analyzing the force damage of the optic nerve after the human head is struck according to claim 8, characterized in that: In the database construction module, the biomechanical parameters include the mass, density, Young's modulus, thermal conductivity, and constant pressure heat capacity of the tissue organs.

10. The device for analyzing the force-induced injury of the optic nerve after a human head is struck according to claim 9, wherein: The biomechanical calculation module performs the following sub-steps: (3.1) Import the reconstructed three-dimensional mesh data file into the finite element analysis software, take the union of the mutually adhered or intersected tissue organs to reflect the contact relationship, then it is necessary to construct a solid for the region surrounded by the surface mesh, then perform the meshing of free tetrahedron meshes on the constructed solid, customize the mesh density of each organ, and finally define the closed force-bearing region according to the edge texture of the model surface mesh; (3.2) Perform adaptive processing on the mesh, shorten the calculation time while ensuring the available resolution and mesh quality by merging adjacent nodes and adjacent meshes of the mesh; (3.3) Import the biomechanical material parameter database into the finite element analysis software, and endow the geometric entities of the tissue organs after mesh adaptation in step (3.2) with different material properties; (3.4) Use the Gaussian function to simulate the buffering effect of the head skin on the force. The force function is defined as f = 100 * Gauss(t - 30), where And set the force application area on the skull surface according to the actual impact situation of the patient, and apply fixed constraints at the bottom and back of the head model. The force application direction is defined by the vector in the Cartesian coordinate system; (3.5) Set the analysis type to transient analysis, set the output time step to 10 ms, and add a parametric scanning item to analyze the influences of different force directions and different force regions on the optic nerve; select the PARDISO direct solver based on LU decomposition to improve the convergence and calculation speed of the calculation model; (3.6) If the calculation model does not converge during the calculation, it is necessary to return to step (3.2) to adjust the mesh division; after the calculation is completed, select von Mises stress, the first principal strain, the force direction, and the displacement of the tissue organs as analysis indicators. In addition, select points at both ends of the optic nerve to define a three-dimensional cross-section, so that it penetrates the entire optic nerve.

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