CN114820919A - Method and system for constructing human body full breathing passage model conforming to real anatomical structure - Google Patents
Method and system for constructing human body full breathing passage model conforming to real anatomical structure Download PDFInfo
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Abstract
The invention discloses a method and a system for constructing a human body full respiratory tract model conforming to a real anatomical structure, which comprises the following steps: acquiring CT (computed tomography) tomography image data of the upper half of a target object, performing threshold segmentation to obtain a respiratory tract mask, and performing three-dimensional reconstruction to obtain a real respiratory tract model; generating a bronchial tree center line skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles, and building an idealized bronchial tree model conforming to an anatomical structure by subdivision modeling; generating random point cloud according to the size of the alveolus, generating a three-dimensional Thiessen polygon by using the random point cloud, and constructing an alveolus path in the three-dimensional Thiessen polygon by adopting an slime mold growth algorithm to obtain an idealised polyhedral alveolus model of the tail end of the respiratory tract; and splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract tail end idealized polyhedral alveolar model according to the anatomical structure to obtain the human body full respiratory tract model. The model construction method provided by the invention has the advantages of short modeling period, high reusability and good extensibility.
Description
Technical Field
The invention relates to the field of biomedical engineering, in particular to a method and a system for constructing a human body full respiratory tract model conforming to a real anatomical structure.
Background
The novel coronavirus pneumonia (Corona Virus Disease 2019, COVID-19) is pneumonia caused by 2019 infection of the novel coronavirus, and is an acute respiratory infectious Disease. The new coronavirus can be directly transmitted by sneezing, coughing, droplets and the like, and the aerosol formed by inhalation of the droplets mixed in the air can also cause infection, and can also cause infection by the re-transmission of contaminated object surfaces to oral, nasal and eye mucosae through hands. The constant spread and variation of viruses presents new challenges to vaccine development and improvement efforts. Inhalation of atomized medicine is the first choice for treating respiratory diseases at present, and inhalation type vaccine is expected to become an effective way for treating respiratory diseases, so that the inoculation cost can be reduced, and the medication compliance can be improved. The way in which the inhaled vaccine exerts its greatest effect can be demonstrated and optimized using Computational Fluid Dynamics (CFD) to assess the inhalation pattern and timing of inhalation vaccine inhalation.
In the respiratory tract numerical simulation and in vitro experiments, a large number of models and devices are available, however, the modeling and manufacturing processes of the models and devices are particularly complex, and the modeling and generation of the full respiratory tract are a difficult problem which is not completely solved at present.
Although the real respiratory tract geometry can be reconstructed from the CT tomographic image data through a three-dimensional reconstruction algorithm, the reconstruction of the bronchial tubes of the segments above the fifth level (G5) is particularly difficult due to the limitation of the resolution of the CT tomographic image data, and the geometry reconstructed from the CT tomographic image data cannot obtain the bronchial geometries of all levels in the full respiratory tract; respiratory tract geometries covering respiratory tract stages (G0-G23) can be obtained from a Weibel idealized model, but the Weibel idealized model cannot reflect the real anatomical structure of the respiratory tract and cannot obtain the geometries of the upper respiratory tract such as the nasal cavity and the oral cavity; meanwhile, the alveolar region in the Weibel ideal model is obtained by measuring polygonal alveolar cells to obtain the diameter of an alveolar, and the deep lung region (G17-G23) is constructed by combining a bronchial tree with a sphere, so that the model is over simplified. Therefore, in order to develop a research on respiratory mechanics of the full respiratory tract, on the premise of ensuring the complexity of the respiratory tract and accurately evaluating the flow characteristics in the respiratory tract, how to quickly construct a full respiratory tract model which can be used for numerical simulation is particularly necessary.
Accordingly, the prior art is yet to be improved and developed.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a human body full respiratory tract model construction method and system according with a real anatomical structure, and aims to solve the problems that the existing respiratory tract modeling method cannot obtain the geometry of each level of bronchus in the full respiratory tract, cannot reflect the real anatomical structure of the respiratory tract, and has long modeling period and low reusability.
The technical scheme of the invention is as follows:
in a first aspect of the present invention, a method for constructing a full respiratory tract model of a human body conforming to a real anatomical structure is provided, wherein the method comprises the steps of:
acquiring CT (computed tomography) sectional image data of the upper half of a target object, performing threshold segmentation to obtain a respiratory tract mask, and performing three-dimensional reconstruction by using the respiratory tract mask to obtain a real respiratory tract model comprising a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a leaf bronchus and a segmental bronchus;
generating a bronchial tree center line skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles, performing subdivision modeling, and constructing an ideal bronchial tree model conforming to an anatomical structure;
generating random point cloud according to the size of an alveolus, generating a three-dimensional Thiessen polygon by using the random point cloud, and constructing an alveolus path in the three-dimensional Thiessen polygon by adopting an slime mold growth algorithm to obtain an idealised polyhedral alveolus model at the tail end of a respiratory tract;
and splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract tail end idealized polyhedral alveolar model according to the anatomical structure to obtain the human body full respiratory tract model.
Optionally, after performing three-dimensional reconstruction and smoothing with the respiratory tract mask, a real respiratory tract model including nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus, and segmental bronchus is obtained.
Optionally, after performing three-dimensional reconstruction and smoothing treatment by using the respiratory tract mask, the step of obtaining a real respiratory tract model including a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a lobar bronchus, and a segmental bronchus specifically includes:
performing three-dimensional reconstruction by using the respiratory tract mask, and obtaining a respiratory tract triangular patch geometric model after calculation;
segmenting the respiratory tract triangular patch geometric model according to nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus;
after four-side face reconstruction is respectively carried out on the geometry of each part of the triangular surface patches after segmentation, subdivision modeling is respectively carried out to obtain the NURBS geometry of each part;
and splicing and repairing the obtained NURBS geometry of each part to obtain a real respiratory tract model with smooth surface, including nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus.
Optionally, the step of generating a bronchial tree centerline skeleton by using the Weibel model and using a three-dimensional rotation matrix with random angles to perform subdivision modeling, and constructing an idealized bronchial tree model conforming to an anatomical structure specifically includes:
generating a plurality of bronchial tree centerline skeletons in different directions by utilizing the lengths of all levels of respiratory tracts in a Weibel model and utilizing a three-dimensional rotation matrix with random angles according to the position of a terminal centerline of a segment bronchial tube and a terminal plane normal vector;
and comparing the plurality of bronchial tree centerline frameworks with different trends with the trends of the respiratory tract in the CT tomographic image data to obtain bronchial tree centerline frameworks which are consistent with the trends of the respiratory tract in the CT tomographic image data, and generating bronchial tree runners along the bronchial tree centerline frameworks by utilizing the diameters of all levels of respiratory tracts in the Weibel model and by means of subdivision modeling to obtain the ideal bronchial tree model conforming to the anatomical structure.
Optionally, random point cloud is generated according to the size of the pulmonary alveoli, a three-dimensional Thiessen polygon is generated by using the random point cloud, and after an pulmonary alveoli path is constructed in the three-dimensional Thiessen polygon by using an slime growth algorithm, four-side reconstruction and subdivision modeling are used for smoothing treatment to obtain an idealized polyhedral pulmonary alveoli model of the respiratory tract terminal.
Optionally, the generating a random point cloud according to the alveolar size, generating a three-dimensional thiessen polygon by using the random point cloud, and constructing an alveolar path in the three-dimensional thiessen polygon by using an slime growth algorithm specifically includes:
generating a first random point cloud in an area needing to generate an idealized polyhedral alveolar model according to the size of an alveolus, and generating a three-dimensional Thiessen polygon by using the first random point cloud;
calculating the gravity center of each three-dimensional Thiessen polygon, and shrinking the three-dimensional Thiessen polygons to a certain proportion of the original size by taking the gravity center as a datum point;
contracting the area needing to generate the idealized polyhedral alveolar model to the gravity center of the first layer of Thiessen polygons, and generating a second random point cloud in the contracted area needing to generate the idealized polyhedral alveolar model according to the size of alveoli;
and setting the second random point cloud as a food point in the slime growth model, creating the slime growth model, and calculating to obtain an alveolar path after iteration.
Optionally, after obtaining the alveolar path, before performing smoothing processing by using quadrilateral reconstruction and subdivision modeling, the method further includes:
and deleting the polygonal surface passing through the alveolar path and connecting the edges of the two adjacent three-dimensional Thiessen polygons to obtain a flow channel connecting each alveolus, performing geometric repair and creating an ideal polyhedral alveolar model inlet.
Optionally, the step of splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract end idealized polyhedral alveolar model according to the anatomical structure to obtain the human body full respiratory tract model specifically includes:
performing plane segmentation on the real respiratory tract model to construct a segmented bronchial outlet;
constructing a connecting curved surface between the section of bronchial outlet and the idealized bronchial tree model, and connecting the real respiratory tract model and the idealized bronchial tree model;
and moving the respiratory tract tail end idealized polyhedral alveolar model to the center of the plane at the tail end of the idealized bronchial tree model, and constructing a connecting curved surface to connect the respiratory tract tail end idealized polyhedral alveolar model and the idealized bronchial tree model.
In a second aspect of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed, the steps of the method for constructing a full body respiratory tract model conforming to a real anatomical structure are realized.
In a third aspect of the present invention, a system for constructing a full body breathing tract model conforming to a real anatomical structure is provided, wherein the system comprises a memory, a processor and a computer program stored in the memory and operable on the processor, and when the processor executes the computer program, the steps of the method for constructing a full body breathing tract model conforming to a real anatomical structure according to the present invention are implemented.
Has the advantages that: the method for constructing the human body total respiratory tract model conforming to the real anatomical structure comprises the steps of carrying out three-dimensional reconstruction on the basis of CT tomographic image data to obtain a real respiratory tract model, expanding a respiratory tract segment bronchial tree to a deep lung region on the basis of a Weibel model and the anatomical structure to obtain an idealized bronchial tree model conforming to the anatomical structure, generating an idealized polyhedral alveolar model of the deep lung region by using a three-dimensional Thiessen polygon and a slime mold growth algorithm, and splicing and assembling the three models to obtain the human body total respiratory tract model. The method for constructing the human body full respiratory tract model conforming to the real anatomical structure can generate the full respiratory tract geometry which comprises bronchial geometries of all levels and can reflect the real anatomical structure of the respiratory tract aiming at different people, can be used for developing related research of respiratory mechanics, provides a simplified model conforming to the anatomical structure for further researching flow and transport rules in all levels of the respiratory tract, and can be applied to the fields of pulmonary administration, vaccine research and development, multi-scale simulation of respiratory tract flow and the like. The human body full breathing passage model construction method conforming to the real anatomical structure provided by the invention has the advantages of short modeling period, high reusability and good extensibility.
Drawings
Fig. 1 (a) is a schematic diagram of a model of a full respiratory tract of a human body in an embodiment of the present invention, and (b) is a partially enlarged diagram.
Fig. 2 is a real airway model map obtained by three-dimensional reconstruction based on CT tomographic image data in the embodiment of the present invention.
Fig. 3 (a) is a CT tomogram in an embodiment of the present invention, (b) is another CT tomogram in an embodiment of the present invention, (c) is another CT tomogram in an embodiment of the present invention, and (d) is a CT tomogram reconstruction diagram in an embodiment of the present invention.
Fig. 4 is a diagram of a grading mode of the whole respiratory tract of a human body.
Fig. 5 (a) is a schematic diagram of a bronchial tree model in an embodiment of the present invention, (b) is a schematic diagram of another bronchial tree model in an embodiment of the present invention, (c) is a schematic diagram of another bronchial tree model in an embodiment of the present invention, and (d) is a schematic diagram of another bronchial tree model in an embodiment of the present invention.
FIG. 6 is a diagram of an alveolar model construction in an embodiment of the present invention.
FIG. 7 shows (a) a pre-smoothed alveolar model and (b) a post-smoothed alveolar model in an embodiment of the present invention.
Detailed Description
The invention provides a method and a system for constructing a human body full breathing passage model conforming to a real anatomical structure, and the invention is further described in detail below in order to make the purpose, the technical scheme and the effect of the invention clearer and more clear. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
In the prior art, the respiratory tract modeling method cannot obtain the geometry of each level of bronchus in the full respiratory tract and reflect the real anatomical structure of the respiratory tract, and the prior modeling method has long modeling period, low reusability and poor extensibility. Based on the above, the embodiment of the present invention provides a method for constructing a full respiratory tract model of a human body conforming to a real anatomical structure, which is characterized by comprising the following steps:
s1, acquiring CT (computed tomography) tomographic image data of the upper body of the target object, performing threshold segmentation to obtain a respiratory tract mask, and performing three-dimensional reconstruction by using the respiratory tract mask to obtain a real respiratory tract model comprising a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a leaf bronchus and a segmental bronchus;
s2, generating a bronchial tree centerline skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles, performing subdivision modeling, and constructing an idealized bronchial tree model conforming to an anatomical structure;
s3, generating random point cloud according to the size of the alveoli, generating a three-dimensional Thiessen polygon by using the random point cloud, and constructing an alveoli path in the three-dimensional Thiessen polygon by adopting an slime mold growth algorithm to obtain an idealised polyhedral alveoli model at the tail end of the respiratory tract;
and S4, splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract end idealized polyhedral alveolar model according to the anatomical structure to obtain the human body full respiratory tract model (as shown in figure 1, only part of alveoli are shown in the figure).
The embodiment of the invention provides a method for constructing a human body full breathing passage model conforming to a real anatomical structure. Firstly, performing three-dimensional reconstruction based on CT tomographic image data to obtain a real respiratory tract model, then performing extended modeling, specifically, extending a respiratory tract segment bronchial tree to a deep lung region based on a Weibel model and an anatomical structure to obtain an idealized bronchial tree model conforming to the anatomical structure, and generating an idealized polyhedral alveolar model of the deep lung region by using a three-dimensional Thiessen polygon and a slime mold growth algorithm. And splicing and assembling the three models to obtain the human body full respiratory tract model conforming to the real anatomical structure. The construction method solves the problems of long respiratory tract modeling period, low reusability and poor expandability in the prior art.
The method for constructing the human body full respiratory tract model conforming to the real anatomical structure provided by the embodiment of the invention can generate the full respiratory tract geometry which comprises all levels of bronchial geometries and can reflect the real anatomical structure of the respiratory tract aiming at different people, is used for developing related research of respiratory mechanics, provides a simplified model conforming to the anatomical structure for further researching flow and transport rules in all levels of the respiratory tract, and can be applied to the fields of lung administration, vaccine research and development, multi-scale simulation of respiratory tract flow and the like.
In step S1, in one embodiment, the step of obtaining the airway mask by acquiring CT tomographic image data of the upper body of the target object and performing threshold segmentation includes:
s11, scanning the upper body of the current object by using a CT tomography to acquire CT tomography image data of the upper body of the target object; the CT tomographic image data can be specifically shown in fig. 3 (a), (b), and (c);
s12, the CT tomographic image data of the upper body of the target object is interpolated, and then the airway region is segmented by a threshold value to generate an airway mask.
In step S11, in a specific implementation, the CT tomography may be used to scan the upper half body region of the target object (for example, the upper region of the chest of a healthy adult male), and when CT tomography is performed, the target object needs to ensure that the respiratory tract is unobstructed, the two hands hold the head, the mouth is opened to a proper size, and the inspiration state is maintained.
In step S12, in a specific implementation, the CT tomographic image data of the upper body of the target object is rendered as needed, then interpolated and then threshold-segmented to prevent the edge of the obtained respiratory tract mask from being too rough, and if the obtained respiratory tract mask does not correspond to the correct respiratory tract region through manual judgment, the obtained respiratory tract mask needs to be modified to the correct respiratory tract corresponding region, so as to segment the accurate respiratory tract mask. In particular, the resulting airway mask can be manually modified to the correct airway corresponding region.
In step S1, in one embodiment, after performing three-dimensional reconstruction (the reconstructed model can be shown in fig. 3 (d)) by using the respiratory tract mask and performing smoothing treatment, a real respiratory tract model (as shown in fig. 2) including nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus is obtained.
In one embodiment, the step of obtaining a real respiratory tract model including a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a lobar bronchus, and a segmental bronchus after performing three-dimensional reconstruction and smoothing with the respiratory tract mask specifically includes:
s13, performing three-dimensional reconstruction by using the respiratory tract mask, and calculating to obtain a respiratory tract triangular patch geometric model;
s14, segmenting the respiratory tract triangular patch geometric model according to nasal cavities, oral cavities, throats, tracheas, main bronchus, lobar bronchus and segmental bronchus;
s15, after four-side face reconstruction is respectively carried out on the geometry of each triangular patch after segmentation, subdivision modeling is respectively carried out to obtain the NURBS geometry of each part;
and S16, splicing and repairing the obtained NURBS geometry of each part to obtain a real respiratory tract model with a smooth surface and comprising a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a lobar bronchus and a segmental bronchus.
In step S14, in order to further improve the calculation efficiency and the time for importing and exporting the model, the respiratory tract triangular patch geometric model is segmented according to the nasal cavity, the oral cavity, the throat, the trachea, the main bronchus, the lobar bronchus, and the segmental bronchus, and stored in different engineering files. In this step, other dissection may be performed according to actual needs, for example, dissection may be performed according to the nasal cavity, oral cavity, and throat as a whole, then dissection may be performed on the trachea, and finally dissection may be performed on the main bronchus, lobar bronchus, and segmental bronchus as a whole. Of course, no segmentation is also an option.
In step S15, mesh repairing, mesh reconstructing, and multi-curved surface constructing are performed on the geometric models of the triangular patches of each part after being segmented, specifically, the geometric models of the triangular patches of each part after being segmented are respectively imported into Rhino software, and after four-side surface reconstruction, the geometric models of each part after being reconstructed are respectively converted into subdivided modeling objects, so as to realize conversion of the geometric surfaces of each part from a sharp triangular mesh patch to a smooth multi-curved surface, and obtain the NURBS geometry of each part. According to actual needs, multiple curved surfaces of each part geometry can be repaired and adjusted, smoothness among the multiple curved surfaces is improved, and specifically, whether the generated geometric surface is smooth or not can be checked by using zebra stripes. Meanwhile, when the segmentation model object is converted into the subdivision modeling object, the grid boundary is identified so as to ensure that the geometric successions of all the segmented parts can be accurately spliced.
Further, in step S16, the obtained NURBS geometry of each part is spliced and repaired in the three-dimensional modeling software. Specifically, the obtained NURBS geometry of each part is imported into the same engineering file and converted into a subdivided modeling object to realize splicing, a layer of multiple curved surfaces at the geometric connection part of each separated part is deleted, a bridge joint surface is created at the formed exposed edge and is divided once to connect the separated geometries, the separated subdivided surfaces are merged after connection is completed, finally the geometry is repaired and adjusted, a real respiratory tract model with smooth surface, including nasal cavity, oral cavity, throat, trachea, main bronchus, leaf bronchus and segmental bronchus, is obtained (whether the generated geometric surface is smooth or not can be checked by using zebra stripes), and is output in a neutral geometry exchange file form such as IGS and the like so as to be conveniently imported into other modeling software.
In step S2, the idealized bronchial tree model extends from the end of the segmental bronchus to the terminal bronchus.
In one embodiment, the step of generating a bronchial tree centerline skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles to perform subdivision modeling, and constructing an idealized bronchial tree model conforming to an anatomical structure specifically includes:
s21, generating a plurality of bronchial tree centerline skeletons in different directions by using the lengths of respiratory tracts at all levels in the Weibel model and according to the position of a terminal centerline of a segment bronchial tube and a terminal plane normal vector and using a three-dimensional rotation matrix with random angles;
s22, comparing the multiple bronchial tree centerline frameworks in different directions with the directions of the respiratory tracts in the CT tomographic image data to obtain bronchial tree centerline frameworks which are consistent with the directions of the respiratory tracts in the CT tomographic image data, and then generating bronchial tree runners along the bronchial tree centerline frameworks by utilizing the diameters of all levels of respiratory tracts in the Weibel model and by means of subdivision modeling to obtain an ideal bronchial tree model conforming to an anatomical structure.
In step S21, based on the Weibel idealized model and using Python modeling in Rhino Grasshopper to generate a bronchial tree centerline skeleton, the obtained bronchial tree centerline skeleton is the centerline skeleton of the bronchial tree model obtained in step S22, and the shape of the bronchial tree centerline skeleton is controlled by the respiratory tract length and the three-dimensional rotation matrix with random angles. Refreshing the three-dimensional rotation matrix using random numbers may generate a plurality of bronchial tree centerline skeletons in different orientations. Three-dimensional rotation is based on the initial branch base vector Q, the target rotation direction is selected to obtain a rotation matrix R formed by rotation angles on corresponding components of the base vector i (i ═ 1, 2, 3), the starting branch vector V is related to the rotation matrix R with random numbers and corresponding angles α and- α i And R -i Multiplying to obtain a unit vector V along the directions of the three sub-branches t1 、V t2 And then generating sub-branch center lines according to the sub-branch lengths (which can be obtained by a Weibel model) to obtain the bronchial tree center line skeletons with different trends.
Wherein the vector is as follows, R x 、R y 、R z The rotation vectors corresponding to the corresponding angles in the x, y and z directions respectively:
R 1 ＝Q T R x Q (2)
R 2 ＝Q T R y Q (3)
R 3 ＝Q T R Z Q (4)
V t1 ＝R i V＝R i (x,y,z) (8)
V t2 ＝R -i V＝R -i (x,y,z) (9)
the figure 4 shows the grading pattern diagram of the whole respiratory tract of a human body, and the lengths and the diameters of the respiratory tracts at all levels in the Weibel model have corresponding relations with the respiratory tract levels. In one embodiment, the Weibel model relates airway length and diameter at each level to airway number as follows:
wherein z is the respiratory tract order, D is the respiratory tract diameter, and L is the respiratory tract length.
In step S22, the multiple bronchial tree centerline skeletons with different orientations are compared with the orientations of the respiratory tracts in the CT tomographic image data, and bronchial tree centerline skeletons that are consistent with the respiratory tracts in the CT tomographic image data are screened out, and then a subdivision polygon is generated along the bronchial tree centerline skeleton by using the diameters (obtainable from Weibel model) of the branch points through subdivision modeling (Multipipe), and the geometric diameters of the subdivision polygon are controlled to a defined diameter, so as to generate a bronchial tree flow channel, thereby obtaining an idealized bronchial tree model that conforms to an anatomical structure. In addition, smooth transition between branches in the bronchial tree model can be controlled by subdivision modeling, and the diameter of each branch can be defined conveniently and accurately.
After subdivision modeling is performed, star points may exist on the generated subdivision model surface, a mesh is generated by using the subdivision model and is encrypted for the first time, and finally a new subdivision model is generated by using the mesh so as to eliminate the star points and obtain an idealized bronchial tree model with smooth transition between NURBS curved surfaces (as shown in (a) - (d) in FIG. 5).
In step S3, a three-dimensional thiessen polygon is generated by using a RhinoGrasshopper based on a random algorithm, an alveolar region formed by polyhedral cells is simulated by using the three-dimensional thiessen polygon, and an alveolar path is constructed in the three-dimensional thiessen polygon by using an myxomycete growth algorithm, so as to obtain an idealized polyhedral alveolar model at the end of the respiratory tract, which extends outward from the terminal bronchus.
In one embodiment, a random point cloud is generated according to the size of an pulmonary alveolus, a three-dimensional Thiessen polygon (as shown in FIG. 6) is generated by using the random point cloud, and after an alveolar path is constructed in the three-dimensional Thiessen polygon by adopting a slime growth algorithm, the alveolar path is smoothed by utilizing quadrilateral reconstruction and subdivision modeling, so that an idealized polyhedral pulmonary alveolus model of the respiratory tract end is obtained. In the present embodiment, a three-dimensional Thiessen polygon with sharp edges is smoothed, and the alveolar models before and after smoothing are shown in FIG. 7 (a) and (b), respectively.
In one embodiment, the step of generating a random point cloud according to the size of the alveoli, generating a three-dimensional taisen polygon by using the random point cloud, and constructing an alveoli path in the three-dimensional taisen polygon by using an slime growth algorithm specifically includes:
s31, generating a first random point cloud in an area where an idealized polyhedral alveolar model needs to be generated according to the size of an alveolus, and generating a three-dimensional Thiessen polygon by using the first random point cloud;
s32, calculating the gravity center of each three-dimensional Thiessen polygon, and shrinking the three-dimensional Thiessen polygon to a certain proportion of the original size by taking the gravity center as a datum point;
s33, shrinking the area needing to generate the idealized polyhedral alveolar model to the gravity center of the first layer of Thiessen polygons, and generating a second random point cloud in the shrunk area needing to generate the idealized polyhedral alveolar model according to the size of alveoli;
and S34, setting the second random point cloud as a food point in the slime growth model, creating the slime growth model, and calculating to obtain an alveolar path after iteration.
In step S32, in one embodiment, the center of gravity of each three-dimensional thiessen polygon is calculated, and the three-dimensional thiessen polygon is shrunk to 60 to 80% of the original size with the center of gravity as a reference point.
In a further embodiment, the center of gravity of each three-dimensional Thiessen polygon is calculated and the three-dimensional Thiessen polygon is shrunk to 80% of its original size with the center of gravity as a reference point.
In step S33, the number of iterations is 4-8, and other numbers of iterations may be selected according to actual needs.
In one embodiment, after obtaining the alveolar path, before performing smoothing processing by using quadrilateral face reconstruction and subdivision modeling, the method further comprises:
and deleting the polygonal surface passing through the alveolar path and connecting the edges of the two adjacent three-dimensional Thiessen polygons to obtain a flow channel connecting each alveolus, performing geometric repair and creating an ideal polyhedral alveolar model inlet. In this embodiment, an idealized polyhedral alveolar model entry can be created as needed for design.
In step S4, in an embodiment, the step of splicing and assembling the real respiratory tract model, the idealized bronchial tree model, and the respiratory tract end idealized polyhedral alveolar model according to an anatomical structure to obtain the human full respiratory tract model specifically includes:
s41, performing plane segmentation on the real respiratory tract model to construct a segmented bronchial outlet;
s42, constructing a connecting curved surface between the section bronchial outlet and the idealized bronchial tree model, and connecting the real respiratory tract model and the idealized bronchial tree model;
and S43, moving the idealized polyhedral alveolar model at the tail end of the respiratory tract to the center of the plane at the tail end of the idealized bronchial tree model, and constructing a connecting curved surface to connect the idealized polyhedral alveolar model at the tail end of the respiratory tract and the idealized bronchial tree model.
And in the step S41, performing plane segmentation on the real respiratory tract model to construct a segmental bronchial outlet so as to facilitate the splicing of the bronchial tree at the tail end of the segmental bronchial. Of course, in order to facilitate numerical simulation and the like, the real respiratory tract model can be subjected to plane segmentation to construct a nasal cavity inlet, an oral cavity inlet and the like.
Further, when the human full respiratory tract model is used for fluid mechanics calculation, a fluid domain geometry for computer fluid mechanics needs to be created, and specifically, after the splicing of the real respiratory tract model, the idealized bronchial tree model and the respiratory tract end idealized polyhedral alveolar model in step S4 is completed, a shared topology is created to share a connection plane to form a complete fluid calculation domain.
The embodiment of the invention also provides a human body full breathing passage model, wherein the human body full breathing passage model conforming to the real anatomical structure is constructed by adopting the method for constructing the human body full breathing passage model.
The embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium stores a computer program, and when the computer program is executed, the steps of the method for constructing a full body breathing passage model conforming to a real anatomical structure as described in the above embodiment are implemented.
The embodiment of the invention also provides a system for constructing the human body full-breathing channel model conforming to the real anatomical structure, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein when the processor executes the computer program, the steps of the method for constructing the human body full-breathing channel model conforming to the real anatomical structure are realized.
In summary, the invention provides a method and a system for constructing a full respiratory tract model of a human body conforming to a real anatomical structure. Firstly, performing three-dimensional reconstruction based on CT tomographic image data to obtain a real respiratory tract model, simultaneously expanding a respiratory tract segment bronchial tree to a deep lung region based on a Weibel model and an anatomical structure to obtain an idealized bronchial tree model conforming to the anatomical structure, generating an idealized polyhedral alveolar model of the deep lung region by using a three-dimensional Thiessen polygon and a slime mold growth algorithm, and then splicing and assembling the three models to obtain the human body total respiratory tract model. The method for constructing the human body full respiratory tract model conforming to the real anatomical structure can generate the full respiratory tract geometry which comprises bronchial geometries of all levels and can reflect the real anatomical structure of the respiratory tract aiming at different people, can be used for developing related research of respiratory mechanics, provides a simplified model conforming to the anatomical structure for further researching flow and transport rules in all levels of the respiratory tract, and can be applied to the fields of pulmonary administration, vaccine research and development, multi-scale simulation of respiratory tract flow and the like. The human body full breathing passage model construction method conforming to the real anatomical structure provided by the invention has the advantages of short modeling period, high reusability and good extensibility.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A method for constructing a human body full respiratory tract model conforming to a real anatomical structure is characterized by comprising the following steps:
acquiring CT (computed tomography) sectional image data of the upper half of a target object, performing threshold segmentation to obtain a respiratory tract mask, and performing three-dimensional reconstruction by using the respiratory tract mask to obtain a real respiratory tract model comprising a nasal cavity, an oral cavity, a throat, a trachea, a main bronchus, a leaf bronchus and a segmental bronchus;
generating a bronchial tree center line skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles, performing subdivision modeling, and constructing an ideal bronchial tree model conforming to an anatomical structure;
generating random point cloud according to the size of an alveolus, generating a three-dimensional Thiessen polygon by using the random point cloud, and constructing an alveolus path in the three-dimensional Thiessen polygon by adopting an slime mold growth algorithm to obtain an idealised polyhedral alveolus model at the tail end of a respiratory tract;
and splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract tail end idealized polyhedral alveolar model according to the anatomical structure to obtain the human body full respiratory tract model.
2. The method for constructing a full respiratory tract model of human body conforming to real anatomical structure of claim 1 wherein a real respiratory tract model including nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus is obtained after three-dimensional reconstruction and smoothing treatment by using the respiratory tract mask.
3. The method for constructing a full respiratory tract model of a human body conforming to a real anatomical structure according to claim 2, wherein the step of obtaining the real respiratory tract model including the nasal cavity, the oral cavity, the throat, the trachea, the main bronchus, the lobar bronchus, and the segmental bronchus after performing the three-dimensional reconstruction and the smoothing treatment by using the respiratory tract mask specifically comprises:
performing three-dimensional reconstruction by using the respiratory tract mask, and obtaining a respiratory tract triangular patch geometric model after calculation;
segmenting the respiratory tract triangular patch geometric model according to nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus;
after four-side face reconstruction is respectively carried out on the geometry of each part of the triangular surface patches after segmentation, subdivision modeling is respectively carried out to obtain the NURBS geometry of each part;
and splicing and repairing the obtained NURBS geometry of each part to obtain a real respiratory tract model with smooth surface, including nasal cavity, oral cavity, throat, trachea, main bronchus, lobar bronchus and segmental bronchus.
4. The method for constructing a full body respiratory tract model conforming to a real anatomical structure according to claim 1, wherein the step of generating a bronchial tree centerline skeleton by using a Weibel model and using a three-dimensional rotation matrix with random angles to perform subdivision modeling to construct an idealized bronchial tree model conforming to an anatomical structure specifically comprises:
generating a plurality of bronchial tree centerline skeletons in different directions by utilizing the lengths of all levels of respiratory tracts in a Weibel model and utilizing a three-dimensional rotation matrix with random angles according to the position of a terminal centerline of a segment bronchial tube and a terminal plane normal vector;
and comparing the plurality of bronchial tree centerline frameworks with different trends with the trends of the respiratory tract in the CT tomographic image data to obtain bronchial tree centerline frameworks which are consistent with the trends of the respiratory tract in the CT tomographic image data, and generating bronchial tree runners along the bronchial tree centerline frameworks by utilizing the diameters of all levels of respiratory tracts in the Weibel model and by means of subdivision modeling to obtain the ideal bronchial tree model conforming to the anatomical structure.
5. The method for constructing a human body total respiratory tract model conforming to a real anatomical structure according to claim 1, wherein random point clouds are generated according to the sizes of alveoli, three-dimensional Thiessen polygons are generated by using the random point clouds, and after an alveoli path is constructed in the three-dimensional Thiessen polygons by adopting an slime mold growth algorithm, quadrilateral face reconstruction and subdivision modeling are used for smoothing treatment, so that a polyhedral alveoli model with an ideal respiratory tract tail end is obtained.
6. The method for constructing a human body total respiratory tract model conforming to a real anatomical structure according to claim 1, wherein the steps of generating a random point cloud according to the size of the alveoli, generating a three-dimensional Thiessen polygon by using the random point cloud, and constructing an alveoli path in the three-dimensional Thiessen polygon by using an slime growth algorithm specifically comprise:
generating a first random point cloud in an area needing to generate an idealized polyhedral alveolar model according to the size of an alveolus, and generating a three-dimensional Thiessen polygon by using the first random point cloud;
calculating the gravity center of each three-dimensional Thiessen polygon, and shrinking the three-dimensional Thiessen polygons to a certain proportion of the original size by taking the gravity center as a datum point;
contracting the area needing to generate the idealized polyhedral alveolar model to the gravity center of the first layer of Thiessen polygons, and generating a second random point cloud in the contracted area needing to generate the idealized polyhedral alveolar model according to the size of alveoli;
and setting the second random point cloud as a food point in the slime growth model, creating the slime growth model, and calculating to obtain an alveolar path after iteration.
7. The method for constructing a full respiratory tract model of a human body conforming to a real anatomical structure according to claim 6, wherein after obtaining the alveolar path, the method further comprises, before smoothing by quadrilateral face reconstruction and subdivision modeling:
and deleting the polygonal surface passing through the alveolar path and connecting the edges of the two adjacent three-dimensional Thiessen polygons to obtain a flow channel connecting each alveolus, performing geometric repair and creating an ideal polyhedral alveolar model inlet.
8. The method for constructing a full human respiratory tract model conforming to a real anatomical structure according to any one of claims 1 to 7, wherein the step of splicing and assembling the real respiratory tract model, the idealized bronchial tree model and the respiratory tract end idealized polyhedral alveolar model according to the anatomical structure to obtain the full human respiratory tract model specifically comprises:
performing plane segmentation on the real respiratory tract model to construct a segmented bronchial outlet;
constructing a connecting curved surface between the section of bronchial outlet and the idealized bronchial tree model, and connecting the real respiratory tract model and the idealized bronchial tree model;
and moving the respiratory tract tail end idealized polyhedral alveolar model to the center of the plane at the tail end of the idealized bronchial tree model, and constructing a connecting curved surface to connect the respiratory tract tail end idealized polyhedral alveolar model and the idealized bronchial tree model.
9. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program which, when executed, implements the steps of the method for constructing a full body breathing passage model conforming to a real anatomical structure according to any one of claims 1 to 8.
10. A system for constructing a full body breathing tract model conforming to a real anatomical structure, comprising a memory, a processor and a computer program stored in the memory and operable on the processor, wherein the processor executes the computer program to realize the steps of the method for constructing a full body breathing tract model conforming to a real anatomical structure according to any one of claims 1 to 8.
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