CN107993277B - priori knowledge-based reconstruction method of artificial bone repair model of damaged part - Google Patents
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Abstract
the invention discloses a reconstruction method of an artificial bone repair model of a damaged part based on prior knowledge. Firstly, extracting the outline of the outer layer of a bone from a medical tomography image, introducing a repairing template and resampling the outline from the repairing template according to the thickness of a tomography layer; secondly, searching a template layer which is most matched with the layer to be repaired in the repairing template by using a characteristic value method and establishing alignment transformation of the template layer and the layer to be repaired; then, obtaining points isomorphic with the break points of the layer to be repaired on the template layer by a common included angle method, calculating a fitting equation between the isomorphic points, and reversely substituting the fitting equation to obtain the interpolation point coordinates of the layer to be repaired; then, generating an inner layer outline according to the given thickness of the inner layer and the outer layer of the skeleton; and finally, obtaining an artificial bone repairing model by VTK three-dimensional reconstruction. The invention is applied to the actual operation that the skull is seriously cracked and can not be directly repaired by the operation after the frontal bone, the parietal bone and other parts of the human body are seriously injured, and the individualized artificial bone needs to be implanted.
Description
Technical Field
The invention belongs to the technical field of computer graphics, and particularly relates to a three-dimensional design of an artificial bone repairing model for repairing a skull damaged part.
background
the method for repairing the skull injury part by using the artificial bone is suitable for clinical operations in which the skull is seriously damaged by crushing and can not be spliced directly through the existing crushed bones. The design of the three-dimensional artificial bone repair model must be consistent with the position and size of the focus, and for the cases of comminuted damage, doctors cannot obtain the approximate shape through the repair of the comminuted bone as a reference for the design of the artificial bone. The template is often used as an auxiliary tool in three-dimensional reconstruction, and the template may be a reconstruction result of an existing healthy bone or an averaged virtual reconstruction result. Many documents at home and abroad aim to repair the outline of the damaged bone by using a template in an auxiliary way, such as automatically identifying intersection points and breakpoint, and then repairing the extracted fracture contour line into a closed contour by using the existing template as a reference and combining a shortest diagonal linear connection method. Because there are differences between the template and the current research case, a deformation mechanism is also introduced in some documents to ensure that the extracted contour line is not distorted, for example, in the three-dimensional reconstruction aiming at the spine, a set of statistical models is proposed to represent an average parameterization result, the template and the current research case are aligned through affine, and then the template is deformed to obtain a real three-dimensional reconstruction result according with the current research case. In addition, some documents start from a template in the process of acquiring the skull three-dimensional model, and continuously deform the skull three-dimensional model by iteration to directly approach the current research case, so that the complete skull three-dimensional model with the characteristics of the current research case is finally obtained.
the existing bones of the same type are used as priori knowledge together, and the contour lines of the bones of the same type which are most matched with the current layer need to be found according to a feature description function. Contour starting point registration is a very effective method, and the most similar one of different contour starting point matches can be obtained through cyclic shift. The alignment transformation can realize the transformation of the space coordinates of the feature point image and establish the corresponding relation between the current layer and the contour lines of the bones of the same type.
Disclosure of Invention
Aiming at the conditions that the frontal bone, parietal bone and other parts of the human skull are subjected to severe trauma and then are subjected to comminuted fracture, and the skull is seriously cracked and cannot be directly repaired by an operation, different human skull bones can be utilized to have global similarity; the medical tomographic images have sequence and local similarity; the extracted skeleton contour has the characteristics of continuity and the like, the existing average skeleton is used as priori knowledge to automatically obtain a skeleton three-dimensional model of a fracture part, and a data basis is provided for the later personalized artificial skeleton repair operation. Compared with the existing broken bone splicing technology, the method has the advantages that the repair accuracy and the repair timeliness are improved.
in order to solve the technical problems, the invention provides a priori knowledge-based reconstruction method of an artificial bone repair model of a damaged part, which takes the profile of the existing repair template as the guidance of the priori knowledge to automatically obtain the artificial bone repair model for repairing the damaged part of the human bone, and the specific process is as follows:
(1) preprocessing a bone contour extracted from a medical tomographic image, and searching bone contours of all non-closed faults, wherein the steps comprise the following steps:
step S01: sequentially reading in medical tomograms, obtaining a skeleton contour map of the medical tomograms by using a Canny method, and obtaining a plurality of closed or non-closed skeleton contour lines of each medical tomogram by combining a boundary tracking algorithm;
step S02: recording the layer where the unclosed skeleton contour line appears for the first time, marking the layer as A, and similarly marking the layer where the unclosed skeleton contour line appears for the last time as Z;
(2) establishing a corresponding relation between the repaired template and the unclosed contour line, wherein the steps comprise the following steps:
step S03: the coordinates of break P, Q in recording layer a;
Step S04: setting the contour line spacing of the repairing template, and resampling to obtain a group of closed skeleton contours;
Step S05: finding a patching template layer A' -1 which is most matched with the closed contour line layer A-1 in the patching template;
(3) the method comprises the following steps of acquiring an artificial bone contour curve used for repairing a human bone injury part at a fault by using a repairing template as priori knowledge, wherein the steps comprise:
step S06: obtaining an optimal matching layer A ' which is the best matched with the layer A according to the optimal matching obtained by the calculation in the step S05, constructing an alignment transformation equation of the optimal matching layer A ' and the layer A, and then aligning the layer A, A ' by using the alignment transformation equation;
step S07: obtaining a point P ' coordinate isomorphic with the breakpoint P in the optimal matching layer A ' by utilizing the common included angle, obtaining an isomorphic point Q ' coordinate of another breakpoint Q in the same way, and calculating a fitting equation X from the sequence points P ' to Q ';
step S08: calculating the coordinates of interpolation points in the layer A by using the fitting equation X obtained in the step S07;
Step S09: calculating an inner layer outline coordinate point of the artificial bone outline according to the given bone thickness d;
step S10: layer a +1 is denoted as a;
Step S11: repeating steps S03 through S10 until A and Z coincide,
(4) Three-dimensionally reconstructing an artificial bone repair model, the steps comprising:
Step S12: and obtaining an artificial bone repairing model by VTK three-dimensional reconstruction.
in step S01, the closed or non-closed skeleton line means that the skeleton line on the cross-section is in a closed or open state.
In step S02, the layer where the unclosed skeleton line appears for the first time is recorded and marked as a, and the layer where the unclosed skeleton line appears for the last time is marked as Z in the same way, which specifically includes the steps of:
step i 01: searching from the topmost layer, calculating the degree d (v) of each vertex v on each layer in a non-directional edge mode, and if d (v) <2 indicates that the point is a suspension point, indicating that the layer has a non-closing phenomenon and is marked as A;
step i 02: starting the searching from the bottommost layer, calculating the degree d (v) of each vertex v on each layer in an undirected edge mode, and if d (v) <2 indicates that the point is a suspension point, the layer has a non-closing phenomenon and is marked as Z.
In step S03, the coordinates of break point P, Q in layer a are recorded, which specifically includes the following steps:
Step q 01: searching and positioning to the layer where the contour line marked as A is located from the topmost layer;
step q 02: pairs of vertices in the layer with vertex degrees less than 2 are labeled as breakpoints P, Q.
in step S04, the patch template is the same average bone data as the current medical tomographic image region, and the average bone data can represent the complete feature information of the current lesion region; the contour line refers to the interval of resampling by taking the scanning interval of the medical tomographic image as a repairing template; the resampling refers to sampling the repairing template according to the scanning distance and direction of the medical tomography image, and the obtained skeleton contour line is called as a repairing template layer.
In step S05, a repairing template layer a' -1 that matches the closed contour line layer a-1 best is found in the repairing template, and the specific steps are as follows:
step p 01: a closed profile line layer A-1 positioned above and adjacent to layer A;
step p 02: utilizing a characteristic value method to carry out similarity judgment between the layer A-1 and the repairing template layer, thereby finding the repairing template layer which is most matched with the layer A-1 and marked as A' -1; otherwise, the sampling start point is adjusted, and step S04 is executed again to obtain new sampling data.
in step S06, a point P 'coordinate isomorphic with the break point P is obtained in the layer a' using the common included angle, and the specific steps are as follows:
Step l 01: the barycentric coordinates of layer A, A 'are represented by R, R', respectively, and P, Q is the A break point;
Step l 02: calculating an included angle theta formed by a connecting line PR from the P to the center of gravity R and a horizontal line;
step l 03: and (3) making a ray with an included angle theta with the horizontal line from the R ', wherein the ray and the layer A' are intersected at a point P ', and the point P' is a point isomorphic with the breakpoint P.
In step S07, the fitting equation is to construct an analytic function from the data set (P ', P + 1', P +2 ', …, P + i', …, Q-j ', …, Q-2', Q-1 ', Q') at the discrete points by using the least square curve fitting principle, and to make the curve of the analytic function approach the discrete points infinitely.
In step S08, calculating coordinates of interpolation points in layer a using fitting equation X, which specifically includes the steps of:
step w 01: inserting n evenly distributed points X on X-axis coordinates of P and Q1,x2,…,xn；
step w 02: x is to be1,x2,…,xnis substituted into a fitting equation X, and y is obtained by calculation1,y2,…,ynThe n coordinate points (x)i,yi) Namely the contour points of the artificial bone.
In step S09, an inner layer contour coordinate point is calculated according to the given bone thickness d, and the specific steps are as follows:
Step h 01: let (x, y), (x ', y') be coordinate points on the outer and inner contours, respectively, and (x, y) be known, requirement (x ', y');
step h 02: measuring the average thickness d of the inner layer and the outer layer of each skull according to the contour map;
step h 03: let dx and dy be x-x 'and y-y' respectively;
step h 04: substituting d into the equationwherein, let dx be dy, i.e. the value of the coordinate (x ', y') can be calculated;
step h 05: and (5) repeating the steps h 01-h 04, and calculating to obtain the coordinate values of all the inner-layer artificial bone contour points of each layer.
the invention achieves the following beneficial technical effects: the invention provides a priori knowledge-based reconstruction method of an artificial skeleton repair model of an injury part, aiming at the conditions that comminuted fracture occurs after frontal bones, parietal bones and other parts of human skull are subjected to re-injury, and the skull is seriously cracked and can not be directly repaired by an operation, different human skull bones can be utilized to have global similarity; the medical tomographic images have sequence and local similarity; the extracted skeleton contour has the characteristics of continuity and the like, the existing average skeleton is used as priori knowledge to automatically obtain a skeleton three-dimensional model of a fracture part, and a data basis is provided for the later personalized artificial skeleton repair operation. Compared with the existing broken bone splicing technology, the method has the advantages that the repair accuracy and the repair timeliness are improved.
drawings
FIG. 1 is a flowchart of the reconstruction method of the artificial bone repair model of the damaged part based on the priori knowledge in the present invention;
FIG. 2 is a schematic diagram of the process of extracting a bone contour by using the Canny algorithm in the present invention;
FIG. 3 is a graph illustrating the degree of a vertex in the present invention;
FIG. 4 is a schematic diagram illustrating the positional relationship between a current layer and a repairing template layer according to the present invention;
FIG. 5 is a flow chart of the search best match algorithm of the present invention;
FIG. 6 is a diagram of the optimal matching and its characterization function in the present invention;
FIG. 7 is a diagram illustrating the alignment transformation of a patch template based on a current layer according to the present invention;
FIG. 8 is a schematic diagram of the present invention using isomorphic points to obtain a fitted curve;
FIG. 9 is a schematic diagram of the generation of an inner layer profile in the present invention;
FIG. 10 is a schematic diagram of a reconstruction model for repairing an artificial bone at a damaged part according to the present invention.
Detailed Description
The invention is further described with reference to specific examples. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
the invention is further described with reference to the following figures and examples.
As shown in fig. 1, the method for reconstructing the artificial bone repair model of the damaged part based on the prior knowledge is characterized in that: the process of automatically obtaining the artificial bone repairing model for repairing the parts with larger bone damage degree of the human body by using the prior knowledge as the guide of the prior repairing template contour.
firstly, preprocessing all bone contours extracted from medical tomograms to search all bone contours of non-closed tomograms, wherein the method comprises the following steps:
Step S01: sequentially reading in medical tomograms, obtaining a skeleton contour map of the medical tomograms by using a Canny method, and obtaining a plurality of closed or non-closed skeleton contours of each medical tomogram by combining a boundary tracking algorithm;
step S02: recording the layer where the unclosed skeleton contour line appears for the first time, marking the layer as A, and similarly marking the layer where the unclosed skeleton contour line appears for the last time as Z;
secondly, establishing a corresponding relation between the patching template and the current unclosed contour line, wherein the steps comprise the following steps:
step S03: break point coordinates P, Q in recording layer a;
step S04: setting the contour line spacing of the repairing template, and resampling to obtain a group of closed skeleton contours;
Step S05: finding a repair template layer A' -1 in the repair template that best matches the closed contour line layer A-1 adjacent to layer A;
Then, using the repair template as prior knowledge to obtain an artificial bone contour curve of the fault for repair, wherein the steps comprise the following steps:
step S06: according to the optimal matching obtained by the calculation in the step S05, the layer A ' which is optimally matched with the layer A is known as the layer A ', an alignment transformation equation of the layer A and the layer A is constructed, and then the layer A, A ' is aligned by using the alignment transformation equation;
step S07: obtaining a point P ' coordinate isomorphic with the breakpoint P in the layer A ' by utilizing the common included angle, obtaining an isomorphic point Q ' coordinate of another breakpoint Q in the same way, and calculating a fitting equation X from the sequence points P ' to Q ';
step S08: calculating the coordinates of interpolation points in the layer A by using the fitting equation X obtained in the step S07;
Step S09: calculating an inner layer contour coordinate point according to the given skeleton thickness d;
Step S10: layer a +1 is denoted as a;
Step S11: steps S03 through S10 are repeated until a and Z coincide.
Finally, reconstructing the artificial bone repair model in three dimensions, the steps comprising:
step S12: and obtaining an artificial bone repairing model by VTK three-dimensional reconstruction.
The process of obtaining the outer contour line of the medical tomographic image is shown in fig. 2. FIG. 2-r is a medical tomogram; FIG. 2-2 shows the remaining skeleton pixels after the skin, brain tissue, eyes and ears and other organ pixels in the original image are filtered out after the binarization threshold is set for the medical tomographic image; FIG. 2-C is a bone contour map obtained using the Canny edge detection method, including the contour of the inner layer of the bone; fig. 2-4 are diagrams for obtaining the outline of the outer layer bone by using a boundary tracking algorithm.
As shown in FIG. 3, degree d (v) refers to the number of edges associated with the vertex v. As an embodiment of the present invention, the 25 th layer of the outer skeleton contour is shown in FIG. 3-r, which is the layer where the first non-closed contour appears, and the point v thereofjdegree d (v) as a continuous pointj) 2; point vi、vkrespectively, a break point, degree d (v)i)＝d(vk) 2; as shown in fig. 3-c, a 74 th skeleton outer layer contour line, and a dotted line frame shows a partial enlargement, wherein a point vm、vnRespectively, are the points of intersection of the lines,Degree d (v)m)＝d(vn)＝3。
as shown in FIG. 4, the positional relationship between the current layer and the repair template layer is shown. FIGS. 4-phi and 4-phi show the layer A (25) where the first non-closed skeleton contour line appears and the adjacent closed layer A-1(24), respectively; FIGS. 4-78 and 4-77 show the A '(78) th layer and the A' -1(77) th layer of the repair template, respectively.
as shown in FIG. 5, the step of finding the Patch template layer A' -1 that best matches layer A-1 in the Patch template comprises:
Step p 01: a closed profile line layer a-1 positioned above and adjacent to layer a;
step p 02: utilizing a characteristic value method to carry out similarity judgment between the layer A-1 and the repairing template, thereby finding the repairing template layer which is most matched with the layer A-1 and marked as A' -1; otherwise, the sampling start point is adjusted, and step S04 is executed again to obtain new sampling data.
as shown in FIG. 6, FIG. 6-is layer A-1; FIG. 6- ② shows layer A' -1 of the patch template that best matches layer A-1; FIG. 6-C and FIG. 6-C are the characteristic describing functions of the layer A-1 and the repairing template layer A' -1 calculated by the characteristic value method: f. ofM(n) and f(A-1)(n), which comprises the following specific steps:
step u 01: aggregating the contour points on the repaired template and the repaired template with the average error minimum method to obtain the non-significant feature points, and reserving the same number of feature points on the two templates by using a threshold value;
Step u 02: obtaining a matching starting point of the two by using a characteristic value method;
step u 03: if the optimal matching can be obtained, finding the repairing template contour which is most matched with the adjacent non-repairing template contour in the same direction; otherwise, adjusting the sampling starting point of the contour line of the repaired template, and continuing to the step S04;
Step u 04: repeating the steps t01 to t03 to find all the patching templates that can match with the non-patching templates.
As shown in fig. 7, layer a is aligned with the repair template layer a' using an alignment transformation. FIG. 7-is layer A' -1; FIG. 7-is a diagram showing the result of clockwise rotation of layer A '-1 by α around the center of gravity R'; FIG. 7-is a graph showing the results of translating the layer A' -1 by d (dx, dy); FIG. 7-d is a plot of layer A, wherein the center of gravity R is a vertical mapping of the center of gravity coordinate R of layer A' -1; FIG. 7-a-is a graph showing the result of rotating layer A 'clockwise about center of gravity R' by the same angle α; FIG. 7-is a graph showing the results after translating layer A' by d (dx, dy). The specific steps of rotation and translation are as follows:
step k 01: and (3) calculating barycentric coordinates of the layers A-1 and A' -1: r, R';
step k 02: recording the matching starting point pair coordinates obtained according to step u 02: s, S';
step k 03: calculating an included angle theta between the line segment RS and the horizontal line and an included angle theta ' between R ' S ' and the horizontal line;
step k 04: calculating the displacement difference dx and dy between R and R';
Step k 04: and substituting alpha to theta-theta' into the rotation matrix, and substituting dx and dy into the translation matrix to obtain an alignment transformation equation.
As shown in fig. 8, the fitting curve is obtained using isomorphic points.
FIG. 8-phi represents the affine alignment result of layer A, A ', where black is layer A where the outline of the unclosed bone is located, gray is a certain layer A ' in the patch template, and layer A ' is the best match to layer A. P, Q is A breaking point, P ' and Q ' are points in A ' which are isomorphic with P, Q, and the calculation steps are as follows:
Step l 01: the barycentric coordinates of layer A, A 'are represented by R, R', respectively, and P, Q is the A break point;
step l 02: calculating an included angle theta formed by a connecting line PR from the P to the center of gravity R and a horizontal line;
step l 03: and a ray which forms an included angle theta with the horizontal line is emitted from the R ', the ray and the layer A' are intersected at a point P ', and the point P' is a point isomorphic with the breakpoint P.
in FIG. 8-II, the curve between the vertices P 'and Q' is a fitting curve X, and the specific implementation method is as follows: the data sets (P ', P + 1', P +2 ', …, P + i', …, Q-j ', …, Q-2', Q-1 ', Q' at the discrete points are constructed as analytical functions such that the curve of the function is as close as possible to the original discrete points.
In fig. 8-c, curve PQ is the coordinate of the interpolation point in layer a calculated by fitting the equation of curve X, and the specific steps are as follows:
step w 01: inserting n evenly distributed points X on X-axis coordinates of P and Q1,x2,…,xn；
step w 02: x is to be1,x2,…,xnIs substituted into a fitting equation X, and y is obtained by calculation1,y2,…,ynthe value of (c). The n coordinate points (x)i,yi) Namely the repair artificial bone contour points.
As shown in fig. 9, inner layer contour coordinate points are calculated based on a given bone thickness d.
in FIG. 9-phi, sequence points P, …, P + m, …, Q-n, …, Q, m < n are the interpolation point sets obtained by fitting equations according to steps w 01-w 02;
Fig. 9-is a diagram showing the result of calculating the inner contour coordinate point according to the existing outer contour coordinate point and the given bone thickness, and the calculation comprises the following specific steps:
step h 01: let (x, y), (x ', y') be coordinate points on the outer and inner contours, respectively, and (x, y) be known, requirement (x ', y');
Step h 02: measuring the average thickness d of the inner layer and the outer layer of the skull of the layer according to the contour map;
step h 03: let dx and dy be x-x 'and y-y' respectively;
Step h 04: substituting d into the equationwherein let dx be dy, the value of the coordinates (x ', y') is calculated;
step h 05: and (5) repeating the step h01 to the step h04, and calculating to obtain coordinate values of all inner layer repairing contour points of the layer.
fig. 9-c is an effect diagram of embedding the obtained inner and outer contours of the artificial bone into layer a.
the process of reconstructing the artificial bone repair model of the damaged part is based on the prior knowledge by the method.
the first embodiment is as follows:
as shown in FIG. 10, FIG. 10-is a three-dimensional reconstruction effect diagram of the damaged skull; FIG. 10-is a three-dimensional reconstruction effect diagram of the artificial bone repair model obtained by the method of the present invention; fig. 10-c and 10-d are different perspective views of the artificial bone repair model embedded into the damaged portion.
the present invention has been disclosed in terms of the preferred embodiment, but is not intended to be limited to the embodiment, and all technical solutions obtained by substituting or converting equivalents thereof fall within the scope of the present invention.
Claims (10)
1. the method for reconstructing the artificial bone repair model of the damaged part based on the priori knowledge is characterized by comprising the following steps of: the method takes the prior knowledge of the contour of the existing repairing template as a guide to automatically obtain an artificial bone repairing model for repairing the damaged part of the human bone, and comprises the following specific processes:
(1) preprocessing a skeleton contour extracted from a medical tomography image, searching all damaged parts, namely obtaining a fracture-shaped contour, and defining the contour with the damage as an unclosed skeleton contour, wherein the method comprises the following steps:
Step S01: sequentially reading in medical tomograms, obtaining a skeleton contour map of the medical tomograms by using a Canny method, and obtaining a plurality of closed or non-closed skeleton contour lines of each medical tomogram by combining a boundary tracking algorithm;
step S02: recording the layer where the unclosed skeleton contour line appears for the first time, marking the layer as A, and similarly marking the layer where the unclosed skeleton contour line appears for the last time as Z;
(2) Establishing a corresponding relation between the repaired template and the unclosed contour line, wherein the steps comprise the following steps:
step S03: the coordinates of break P, Q in recording layer a;
Step S04: setting the contour line spacing of the repairing template, and resampling to obtain a group of closed skeleton contours;
Step S05: finding a patching template layer A' -1 which is most matched with the closed contour line layer A-1 in the patching template;
(3) the method comprises the following steps of obtaining an artificial bone repair model contour curve used for repairing a human bone injury part at a fault by using a repair template as prior knowledge, wherein the steps comprise:
Step S06: obtaining an optimal matching layer A ' which is the best matched with the layer A according to the optimal matching obtained by the calculation in the step S05, constructing an alignment transformation equation of the optimal matching layer A ' and the layer A, and then aligning the layer A, A ' by using the alignment transformation equation;
Step S07: obtaining a point P ' coordinate isomorphic with the breakpoint P in the optimal matching layer A ' by utilizing the common included angle, obtaining an isomorphic point Q ' coordinate of another breakpoint Q in the same way, and calculating a fitting equation X from the sequence points P ' to Q ';
Step S08: calculating the coordinates of interpolation points in the layer A by using the fitting equation X obtained in the step S07;
step S09: calculating an inner layer contour coordinate point of a contour curve of the artificial bone repairing model according to the given bone thickness d;
step S10: layer a +1 is denoted as a;
step S11: repeating steps S03 through S10 until A and Z coincide;
(4) three-dimensionally reconstructing an artificial bone repair model, the steps comprising:
Step S12: and obtaining an artificial bone repairing model by VTK three-dimensional reconstruction.
2. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: the closed or non-closed bone contour in step S01 means that the bone contour on the fracture is in a closed or open state.
3. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S02, the layer where the first unclosed skeleton line appears is recorded and marked as a, and the layer where the last unclosed skeleton line appears is marked as Z in the same way, which includes the following specific steps:
Step i 01: searching from the topmost layer, calculating the degree d (v) of each vertex v on each layer in a non-directional edge mode, and if d (v) <2 indicates that the point is a suspension point, indicating that the layer has a non-closing phenomenon and is marked as A;
Step i 02: starting the searching from the bottommost layer, calculating the degree d (v) of each vertex v on each layer in an undirected edge mode, and if d (v) <2 indicates that the point is a suspension point, the layer has a non-closing phenomenon and is marked as Z.
4. The method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S03, the coordinates of break point P, Q in layer a are recorded, which specifically includes the steps of:
Step q 01: searching and positioning to the layer where the contour line marked as A is located from the topmost layer;
Step q 02: pairs of vertices in the layer with vertex degrees less than 2 are labeled as breakpoints P, Q.
5. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S04, the patch template is the same average bone data as the current medical tomographic image region and the average bone data can represent the complete feature information of the current lesion region; the contour line refers to the interval of resampling by taking the scanning interval of the medical tomographic image as a repairing template; the resampling refers to sampling the repairing template according to the scanning distance and direction of the medical tomography image, and the obtained skeleton contour line is called as a repairing template layer.
6. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S05, a repairing template layer a' -1 that matches the closed contour line layer a-1 best is found in the repairing template, which comprises the following specific steps:
step p 01: a closed profile line layer A-1 positioned above and adjacent to layer A;
step p 02: utilizing a characteristic value method to carry out similarity judgment between the layer A-1 and the repairing template layer, thereby finding the repairing template layer which is most matched with the layer A-1 and marked as A' -1; otherwise, the sampling start point is adjusted, and step S04 is executed again to obtain new sampling data.
7. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S06, using the common included angle to obtain the coordinate of point P 'isomorphic with the break point P in the layer a', the specific steps are:
step l 01: the barycentric coordinates of layer A, A 'are represented by R, R', respectively, and P, Q is the A break point;
step l 02: calculating an included angle theta formed by a connecting line PR from the P to the center of gravity R and a horizontal line;
step l 03: and (3) making a ray with an included angle theta with the horizontal line from the R ', wherein the ray and the layer A' are intersected at a point P ', and the point P' is a point isomorphic with the breakpoint P.
8. The method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S07, the fitting equation is to construct an analytic function from the data set (P ', P + 1', P +2 ', …, P + i', …, Q-j ', …, Q-2', Q-1 ', Q') at the discrete points by using the least square curve fitting principle, and to make the curve of the analytic function approach the discrete points infinitely.
9. the method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 1, wherein: in step S08, calculating coordinates of interpolation points in layer a using fitting equation X, which specifically includes the steps of:
step w 01: inserting n evenly distributed points X on X-axis coordinates of P and Q1,x2,…,xn；
step w 02: x is to be1,x2,…,xnis substituted into a fitting equation X, and y is obtained by calculation1,y2,…,ynthe n coordinate points (x)i,yi) I.e. points on the contour curve of the artificial bone.
10. The method for reconstructing the a priori knowledge-based damaged part artificial bone repair model according to claim 9, wherein: in step S09, an inner layer contour coordinate point is calculated according to the given bone thickness d, which specifically includes the steps of:
step h 01: let (x, y), (x ', y') be coordinate points on the outer and inner contours, respectively, and (x, y) be known, requirement (x ', y');
Step h 02: measuring the average thickness d of the inner layer and the outer layer of each skull according to the contour map;
step h 03: let dx and dy be x-x 'and y-y' respectively;
Step h 04: substituting d into the equationWherein, let dx be dy, i.e. the value of the coordinate (x ', y') can be calculated;
Step h 05: and (5) repeating the steps h 01-h 04, and calculating to obtain the coordinate values of all the inner-layer artificial bone contour points of each layer.
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