Method, apparatus and device for establishing a three-dimensional model of the spine by X-ray imaging

Abstract

The present invention discloses a method, apparatus and device for establishing a three-dimensional model of the spine for X-ray imaging, which is applied to a biplane X-ray imaging system and includes obtaining biplane X-ray images of the human torso in different weight-bearing postures; calibrating the positions of each vertebral body feature point in the X-ray images; performing spatial calibration on the biplane X-ray imaging system; converting the positions of the feature points on the two-dimensional images into three-dimensional space coordinates distributed in the biplane X-ray imaging space; reconstructing the fitting ellipse of the endplate and the spatial position of the transverse process of the vertebral body according to the positions of multiple feature points and the spatial position relationship of the biplane X-ray imaging system, that is, calculating the position of the vertebral body structure in the three-dimensional space; setting the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulating the geometric body formed by the upper and lower endplates, and constructing each vertebral body as a cylinder-like body, thereby completing the establishment of the three-dimensional model of the spine, improving the construction efficiency of the three-dimensional model of the spine, and reducing the deviation of the clinical parameters of the spine measured in two dimensions.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging technology, and particularly to a method, device and equipment for establishing a three-dimensional model of the spine by X-ray imaging. Background Art

[0002] Spinal deformity is a common disease, mainly including scoliosis, kyphosis, rotational deformity, etc. Due to the complexity of its lesions, the surgical correction is difficult. At present, the traditional DR images relied on for spinal deformity assessment will lose information in one dimension, and CT and MR cannot be taken in the standing weight-bearing position. Therefore, there is a clinical need for a three-dimensional reconstruction method that can quickly understand the spinal deformity of patients in the weight-bearing position, help doctors formulate surgical plans in advance, and judge the postoperative efficacy.

[0003] Currently, the mainstream method for reconstructing the three-dimensional model of the spine is to use computer tomography (CT) technology. When the patient is in the supine position, the entire length of the patient's spine is tomographically scanned, and the scan layer thickness is set at the millimeter level. During the scanning process, it is always ensured that the scanning plane is perpendicular to the patient's spinal canal, so as to obtain fine-spacing cross-sectional images of the spine. After obtaining the CT images, medical three-dimensional modeling software such as Mimics can be used to segment the vertebral bodies from the CT images, and then interpolation, smoothing and other processes are performed to obtain a three-dimensional model of the spine. There are mainly the following disadvantages in using CT scanning to establish the three-dimensional structure of the spine: 1) The process of establishing the three-dimensional spinal structure from CT images is complex and requires professionals to manually perform operations such as recognition and repair, which is time-consuming and laborious. 2) The radiation dose received by the patient is large. The radiation dose of a single frontal chest X-ray (chest radiograph) is 0.02 mSv, while the average dose of a plain spinal CT scan is about 6 mSv, which is equivalent to taking 300 chest radiographs. 3) There are differences in the spinal structure of the patient in the supine position and the standing position, which may lead to deviations in the measurement of some clinical parameters.

[0004] In summary, it is necessary to propose a method for establishing a three-dimensional model of the spine by X-ray imaging to solve the defects of the existing technology, such as the complexity of establishing the three-dimensional spinal structure, the large radiation dose received by the patient, and the easy deviation of clinical parameters. Summary of the Invention

[0005] The purpose of the present invention is to provide a method, device and equipment for establishing a three-dimensional model of the spine by X-ray imaging, which can quickly establish a 3D model of the spine based on the geometric relationship of projections according to dual-plane X-ray images.

[0006] The present invention provides a method for establishing a three-dimensional model of the spine by X-ray imaging, which is applied to a dual-plane X-ray imaging system and includes the following steps:

[0007] Obtain dual-plane X-ray images of the human torso in different weight-bearing postures;

[0008] Calibrate the positions of each vertebral feature point in the X-ray image, where the feature point positions include corner point positions and transverse process positions;

[0009] Perform spatial calibration on the biplane X-ray imaging system, convert the biplane environment into three-dimensional space coordinates, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver;

[0010] Set the biplane X-ray image in three-dimensional space and convert the feature point positions into three-dimensional space coordinates distributed in the biplane X-ray imaging space;

[0011] Reconstruct the endplate fitting ellipse of the vertebral body and the spatial positions of the transverse processes based on multiple feature point positions, that is, calculate the position of the vertebral body structure in three-dimensional space. The position characteristics of the endplate fitting ellipse include the center positions, normal vectors, major axis vectors, and minor axis vectors of the upper endplate ellipse and the lower endplate ellipse;

[0012] Set the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulate the geometric body formed by the upper endplate and the lower endplate, and construct each vertebral body as a cylinder-like body to complete the establishment of the three-dimensional spine model.

[0013] Preferably, it further includes:

[0014] Establish the local three-dimensional coordinate system of each vertebral body according to the spatial positions of the upper endplate fitting ellipse and the lower endplate fitting ellipse and the transverse processes. For any two local three-dimensional coordinate systems, calculate the rotation matrix and displacement vector of one coordinate system relative to the other coordinate system, so as to obtain the slip degree, vertebral body flexion angle, vertebral body scoliosis angle, and vertebral body axial rotation angle between any two vertebral bodies.

[0015] Preferably, the establishing the local three-dimensional coordinate system of each vertebral body according to the spatial positions of the upper endplate fitting ellipse and the lower endplate fitting ellipse and the transverse processes includes:

[0016] For any vertebral body, define the midpoint of the line connecting the centers of the upper endplate and the lower endplate as the origin of the coordinate system, and establish the local three-dimensional coordinate system of each vertebral body. The formula is as follows:

[0017]

[0018]

[0019]

[0020] Normalize the calculated results to obtain the three-dimensional coordinate system of each vertebral body

[0021] Among them, n1 and n2 are the normal vectors of the upper endplate and the lower endplate respectively, and p1 and p2 are the coordinates of the identified transverse processes in three-dimensional space respectively.

[0022] Preferably, perform spatial calibration on the dual-plane X-ray imaging system, convert the dual-plane environment into three-dimensional space coordinates, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver, including:

[0023] Define the positions and sizes of the first radiation source, the second radiation source, the first X-ray receiver, and the second X-ray receiver in the three-dimensional space coordinate system;

[0024] Set a calibration plate on the X-ray receiver, and use the following optimization method to obtain the rotation matrix R of the calibration plate coordinate system relative to the first X-ray receiver and the second X-ray receiver F1 , R F2 and the displacement vector V F1 , V F2 , the formula is as follows:

[0025]

[0026] Calculate the relative spatial position between the relative position relationships of the first X-ray receiver and the second X-ray receiver according to the coordinate system transformation, and the formula is as follows:

[0027]

[0028] Among them, P pi is the position of the i-th lead point on the calibration plate obtained by photographing the dual-plane X-ray imaging system, and P mi is the true position of the i-th lead point on the calibration plate; denote the coordinates of the second X-ray receiver in the F2 plane coordinate system as P F2 , and the coordinates of the first X-ray receiver in the F1 plane coordinate system as P F1 , and the local coordinates on the calibration plate as P L ; the rotation matrix R2to1 of the first X-ray receiver F1 plane relative to the second X-ray receiver F2 plane is The displacement vector V2to1 is The superscript T represents the transpose matrix.

[0029] Preferably, set the dual-plane X-ray image in three-dimensional space, and convert the characteristic point positions into three-dimensional space coordinates distributed in the dual-plane X-ray imaging space, including:

[0030] Convert the two-dimensional corner point positions (x, y) or transverse process positions (x, y) into three-dimensional space coordinates P distributed on the dual-plane X-ray image through the spatial coordinate conversion relationshipx，y，z , the formula is as follows:

[0031]

[0032]

[0033]

[0034] where h is the height (number of pixels) of the biplane X-ray image, w is its width (number of pixels), respectively represent the coordinates of the upper right, lower right, upper left, and lower left points of the X-ray receiver in the three-dimensional coordinate system, and c1, c2 are calculation parameters.

[0035] Preferably, the reconstructing the spatial position of the endplate fitting ellipse of the vertebral body according to the positions of the plurality of feature points includes:

[0036] Obtain the radiation source coordinate F i =(F ix , F iy , F iz , ) and the radiation vector u i , the straight line where the radiation is located is described as an equation about the variable s:

[0037] L i =F i +s i ·u i ,

[0038] where i = 1, 2, representing two rays of the biplane, then the approximate intersection coordinate p of the two straight lines i =L i1 +s1·u1 = L i2 +s2·u2, and [s1, s2] can be solved by the least squares method T :

[0039] where: After calculating [s1, s2] T , substitute them into the straight line Li expression respectively to obtain the point p1 on the straight line L1 and the point p2 on the straight line L2, then the approximate intersection coordinate p of the two straight lines is:

[0040]

[0041] Assume that the connection vector of the two corner points of the same endplate in the first shooting direction is The connection vector of the same two corner points of the endplate in the second shooting direction is The cross product formula for calculating the connection lines of the two corner points in the first shooting direction and the second shooting direction is as follows, as the normal vector of the approximate ellipse of the vertebral body endplate, with the direction vertically upward;

[0042]

[0043] Define the distance F from the radiation source to the center of the circle i The distance F between O and the midpoint of the line connecting the two angular points of the radiation source to the corresponding plane i Take the ratio ri of C as the scaling factor, define the direction of the line connecting the two angular points of one of the planes as the major axis vector, define the cross product of the normal vector and the major axis vector as the minor axis vector, and the length Li of the major axis or the minor axis is the product of the length CLi of the line connecting the corresponding two angular points and the corresponding scaling factor. The calculation formula is as follows:

[0044]

[0045] L i = CL i × r i .

[0046] Preferably, the reconstruction of the spatial position of the transverse process according to the positions of multiple said feature points includes:

[0047] Obtain the radiation source coordinates F i =(F ix , F iy , F iz ,) and the radiation vector u i , and the straight line where the radiation is located is described as an equation about the variable s:

[0048] L i = F i + s i · u i ,

[0049] where i = 1, 2, representing the two rays of the double plane, then the approximate intersection coordinates p of the two straight lines i = L i1 + s1 · u1 = L i2 + s2 · u2, and [s1, s2] can be solved by the least squares method T :

[0050] where: After calculating [s1, s2] T , substitute them into the straight line Li expression respectively to obtain the point p1 on the straight line L1 and the point p2 on the straight line L2. Then the approximate intersection coordinates p of the two straight lines are:

[0051]

[0052] The present invention also provides an X-ray imaging spinal three-dimensional model establishment device, which is applied to a double-plane X-ray imaging system and includes:

[0053] An image acquisition module for acquiring biplane X-ray images of the human torso in different load-bearing postures;

[0054] A feature point output module for calibrating the positions of each vertebral feature point in the X-ray image, where the feature point positions include corner positions and transverse process positions;

[0055] A spatial calibration module for performing spatial calibration on the biplane X-ray imaging system, converting the biplane environment into three-dimensional space coordinates, and obtaining the relative position relationship between the first X-ray receiver and the second X-ray receiver;

[0056] A feature point conversion module for setting the biplane X-ray image in three-dimensional space and converting the feature point positions into three-dimensional space coordinates distributed on the biplane X-ray image;

[0057] A vertebral body construction module for reconstructing the endplate fitting ellipse of the vertebral body and the spatial position of the transverse process according to multiple feature point positions, that is, calculating the position of the vertebral body structure in three-dimensional space. The position characteristics of the endplate fitting ellipse include the center positions, normal vectors, major axis vectors, and minor axis vectors of the upper endplate ellipse and the lower endplate ellipse;

[0058] A model output module for setting the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulating the geometric body formed by the upper endplate and the lower endplate, and constructing each vertebral body into a cylinder-like body to complete the establishment of a three-dimensional spinal model.

[0059] The present invention also provides a computer device, including:

[0060] A memory for storing a processing program;

[0061] A processor that, when executing the processing program, implements the X-ray imaging spinal three-dimensional model establishment method described in this embodiment.

[0062] The present invention also provides a computer-readable medium, in which a computer program for implementing the X-ray imaging spinal three-dimensional model establishment method described in this embodiment is loaded.

[0063] Regarding the prior art, the present invention has the following beneficial effects:

[0064] The method for establishing a three-dimensional model of the spinal column by X-ray imaging provided by the present invention approximates the vertebral endplates as ellipses. According to the calibrated corner point positions and the principle of point light source projection, the center position, normal vector, major axis vector, and minor axis vector of the ellipse fitting the endplate are calculated using the spatial geometric relationship of double-plane projection. Each vertebra is approximated as a cylinder-like body composed of upper and lower endplates, and thus a three-dimensional model of the spinal column is reconstructed. This model can be used to calculate clinical parameters such as the thickness of the intervertebral disc and the thickness of the vertebra. The three-dimensional positions of the transverse processes are calculated using the relational expressions between lines and planes in three-dimensional space and the approximate intersection points of two lines. Then, based on the positions of the upper and lower endplates of the vertebra and the positions of the transverse processes, a local three-dimensional coordinate system for each vertebra is established. For any two local three-dimensional coordinate systems, the rotation matrix and displacement vector of one coordinate system relative to the other are calculated, so as to obtain the slip degree, vertebral flexion angle, vertebral scoliosis angle, and vertebral axial rotation angle between any two vertebrae, improving the efficiency of constructing the three-dimensional model of the spinal column and reducing the deviation of traditional two-dimensional measurement of spinal clinical parameters.

[0065] By marking the corner point positions and transverse process positions of each vertebra in the X-ray images of the human torso from two perspectives, a 3D model of the spinal column can be quickly established according to the geometric relationship of the projection.

[0066] The present invention only requires the patient to undergo a single double-plane X-ray shooting to complete data acquisition, and the radiation dose received by the patient is much lower than that of a plain spinal CT scan.

[0067] The present invention can establish a three-dimensional model of the spinal column when the patient is in the standing position to ensure the accuracy of subsequent clinical parameter calculations; it can also establish a three-dimensional model of the spinal column under special movements according to the condition and surgical requirements, providing convenience for clinical research. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a schematic diagram of the steps of the method for establishing a three-dimensional model of the spinal column by X-ray imaging in an embodiment of the present invention;

[0069] Figure 2 It is a schematic diagram of the labeling results of the four corner points (black edges and white centers) and transverse processes (white edges and black centers) of the lumbar vertebrae in an embodiment of the present invention;

[0070] Figure 3 It is a schematic diagram of fitting the upper endplate ellipse in a double-plane environment in an embodiment of the present invention;

[0071] Figure 4 It is a schematic diagram of the final automated reconstruction result in an embodiment of the present invention;

[0072] Figure 5 It is a schematic block diagram of the principle of the device for establishing a three-dimensional model of the spinal column by X-ray imaging in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0074] Embodiment 1

[0075] As Figure 1 shown, the present invention provides a method for quickly establishing a three-dimensional model of the spinal column for X-ray imaging, which is applied to a biplane X-ray imaging system and includes the following steps:

[0076] Step S1: Obtain biplane X-ray images of the human torso in different load-bearing postures; different load-bearing postures include at least frontal / lateral shooting, shooting from the front and side angles, and can also be shot at a 45-degree angle. For example, use a biplane X-ray imaging system to shoot X-ray images of the human torso from two perspectives. Here, the two perspectives refer to two orthogonal shooting directions in the biplane X-ray imaging system, that is, the line connecting the first radiation source to the first receiver is perpendicular to the line connecting the second radiation source to the second receiver.

[0077] Step S2: Calibrate the positions of each vertebral characteristic point in the X-ray image. The characteristic point positions include corner point positions and transverse process positions; mark the four corner point positions and two transverse process positions of each vertebral body in the X-ray image. As Figure 2 shown, those skilled in the art can understand that the corner point refers to the sharp corner position of the spinal column in the X-ray image of the human torso.

[0078] Step S3: Perform spatial calibration on the biplane X-ray imaging system, convert the biplane environment into a three-dimensional space coordinate, convert the second X-ray receiver plane coordinate system to the first X-ray receiver plane coordinate system, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver;

[0079] Step S4: Set the biplane X-ray images in the three-dimensional space according to the spatial coordinate conversion relationship between the first X-ray receiver plane coordinate system and the second X-ray receiver plane coordinate system, and convert the characteristic point positions into three-dimensional space coordinates distributed in the biplane X-ray imaging space;

[0080] Step S5: Reconstruct the fitting ellipse of the endplate of the vertebral body and the spatial positions of the transverse processes based on the positions of multiple said feature points, that is, calculate the position of the vertebral body structure in three-dimensional space. The position features of the fitting ellipse of the endplate include the center positions, normal vectors, major axis vectors, and minor axis vectors of the upper endplate ellipse and the lower endplate ellipse. Those skilled in the art can understand that the endplate refers to the bone plates formed on the upper and lower surfaces of the spinal vertebrae, which constitute the upper and lower boundaries of the intervertebral disc.

[0081] Step S6: Set the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, use the Delaunay triangulation algorithm to triangulate the geometric body formed by the upper endplate and the lower endplate, and construct each vertebral body into a cylinder-like body represented by a Delaunay triangular mesh to complete the establishment of the three-dimensional spinal model.

[0082] Step S7: Establish the local three-dimensional coordinate system of each said vertebral body according to the spatial positions of the upper endplate fitting ellipse, the lower endplate fitting ellipse, and the transverse processes. For any two local three-dimensional coordinate systems, calculate the rotation matrix and displacement vector of one coordinate system relative to the other coordinate system, and calculate the slip degree, vertebral body flexion angle, vertebral body scoliosis angle, and vertebral body axial rotation angle between any two vertebral bodies.

[0083] In the present invention, by marking the corner positions and transverse process positions of each vertebral body in the X-ray images of the human torso from two perspectives, and then calculating the spatial positions, normal vectors, and sizes of the upper and lower endplates of each vertebral body through the principle of point light source projection, the endplates are fitted into ellipses, and the vertebral bodies can be fitted into cylinder-like bodies. Then, according to the position of the transverse processes, the rotation direction of the vertebral body is calculated, and thus a three-dimensional spinal model is established. In an embodiment of the present invention, the corner positions and transverse process positions of each vertebral body in the X-ray image can be marked by artificial intelligence recognition technology, or the corner positions and transverse process positions of each vertebral body in the X-ray image can be manually marked.

[0084] By marking the corner positions and transverse process positions of each vertebral body in the X-ray images of the human torso from two perspectives, a 3D model of the spine can be quickly established according to the geometric relationship of the projection; only one double-plane X-ray photograph of the patient is required to complete data collection, and the radiation dose received by the patient is much lower than that of a plain spinal CT scan; a three-dimensional spinal model of the patient in the standing position can be established to ensure the accuracy of subsequent clinical parameter calculations; a three-dimensional spinal model under special movements can also be established according to the condition and surgical needs, providing convenience for clinical research.

[0085] Specifically, in step S2, spatial calibration is performed on the double-plane X-ray imaging system to convert the double-plane environment into three-dimensional space coordinates and convert the second X-ray receiver plane coordinate system to the first X-ray receiver plane coordinate system. The relative position relationship between the first X-ray receiver and the second X-ray receiver obtained includes:

[0086] Define the positions and sizes of the first radiation source, the second radiation source, the first X-ray receiver, and the second X-ray receiver in a three-dimensional space coordinate system; set the plane coordinate system of the first X-ray receiver F1 as the global coordinate system, and the coordinate system of the second X-ray receiver F2 can be transformed onto the first X-ray receiver F1, so as to obtain the relative position of the second X-ray receiver F2 with respect to the first X-ray receiver F1, and complete the spatial calibration process of the dual-plane system. The specific calibration method is as follows:

[0087] Set a calibration plate in front of the X-ray receiver, and use the following optimization method to obtain the rotation matrix R F1 of the calibration plate coordinate system relative to the first X-ray receiver and the second X-ray receiver F2 and the displacement vector V F1 of the calibration plate coordinate system relative to the first X-ray receiver and the second X-ray receiver F2 . The formula is as follows:

[0088]

[0089] where P pi is the position of the i-th lead point on the calibration plate obtained by photographing the dual-plane X-ray imaging system, and P mi is the true position of the i-th lead point on the calibration plate; denote the coordinates in the plane coordinate system of the second X-ray receiver F2 as P F2 , the coordinates in the plane coordinate system of the first X-ray receiver F1 as P F1 , and the local coordinates on the calibration plate as P L ;

[0090] Calculate the relative spatial position between the first X-ray receiver F1 and the second X-ray receiver F2 according to the coordinate system transformation. According to the coordinate system transformation, the formula is as follows:

[0091]

[0092] The rotation matrix R2to1 of the plane of the first X-ray receiver F1 relative to the plane of the second X-ray receiver F2 is The displacement vector V2to1 is The superscript T represents the transpose matrix. In this way, the relative spatial position between the two planes can be calculated. The first X-ray receiver F1 and the second X-ray receiver F2 can be intensifying screens or other detectors, which can be understood as equivalent to a plane.

[0093] Specifically, in step S4, setting the bi-plane X-ray image in the three-dimensional space according to the spatial coordinate conversion relationship between the first X-ray receiver plane coordinate system and the second X-ray receiver plane coordinate system, and converting the feature point positions into three-dimensional space coordinates distributed in the bi-plane X-ray imaging space includes:

[0094] Laying the bi-plane X-ray image flat at the corresponding X-ray receiver position in the three-dimensional space, and converting the two-dimensional corner point position (x, y) or transverse process position (x, y) into the three-dimensional space coordinate P distributed on the bi-plane X-ray image through the above spatial coordinate conversion relationship x，y，z , and the formula is as follows:

[0095]

[0096]

[0097]

[0098] In the formula, h is the height (number of pixels) of the bi-plane X-ray image, w is its width (number of pixels), respectively represent the coordinates of the upper right, lower right, upper left, and lower left corner points of the X-ray receiver in the three-dimensional coordinate system, and c1, c2 are calculation parameters.

[0099] Referring to Figure 3 as shown, in step S5, reconstructing the spatial position of the endplate fitting ellipse of the vertebral body according to the positions of multiple feature points includes:

[0100] Obtaining the radiation source coordinate F i =(F ix , F iy , F iz , ) and the radiation vector u i , and the straight line where the radiation is located is described as an equation about the variable s:

[0101] L i =F i +S i ·u i ,

[0102] where i = 1, 2, representing two rays of the bi-plane, then the approximate intersection coordinate p i =L i1 +s1·u1 = L i2 +s2·u2, and [s1, s2] can be solved by the least squares method T :

[0103] Among them: Calculating [s1, s2] TAfter that, substitute them into the expression of the straight line Li respectively to obtain the point p1 on the straight line L1 and the point p2 on the straight line L2. Then, the approximate intersection coordinates p of the two straight lines are as follows:

[0104]

[0105] Assume that the vector connecting two corner points of the same end plate on the first X-ray receiver plane is The vector connecting two corner points of the same end plate on the second X-ray receiver plane is That is, the vector connecting two corner points of the same end plate on the first X-ray receiver plane is The vector connecting two corner points of the same end plate on the second X-ray receiver plane is are the unit vectors in the X, Y, and Z axis directions respectively. The cross product formula of the two vectors connecting the two corner points in the first shooting direction and the second shooting direction is as follows, which is used as the normal vector of the approximate ellipse of the vertebral end plate, and the direction is vertically upward;

[0106]

[0107] According to the point light source projection principle and the side length ratio relationship of similar triangles, define the distance F from the radiation source to the center of the circle i The distance F from O to the midpoint of the line connecting the radiation source to the two corner points of the corresponding plane i C. Define the ratio ri as the scaling factor, define the direction of the line connecting the two corner points of one plane as the major axis vector, which is perpendicular to the normal vector, define the cross product of the normal vector and the major axis vector as the minor axis vector, and the length Li of the major axis or the minor axis is the product of the corresponding line length CLi connecting the two corner points and the corresponding scaling factor. The calculation formula is as follows:

[0108]

[0109] L i =CL i ×r i ,

[0110] Specifically, the reconstruction of the spatial position of the transverse process according to the positions of multiple said feature points in step S5 includes:

[0111] Obtain the radiation source coordinates F i =(F ix , F iy , F iz , ) and the radiation vector u i . The straight line where the radiation is located is described as an equation about the variable s:

[0112] L i =F i +s i ·u i ,

[0113] where \(i = 1, 2\) represents two rays of the biplane, and the approximate intersection coordinates \(p\) of the two lines i = L i1 + s1·u1 = L i2 + s2·u2, and \([s1, s2]\) can be solved by the least squares method T :

[0114] where: Calculate \([s1, s2]\) T After that, substitute them into the expressions of the straight lines \(Li\) respectively, and obtain the points \(p1\) on the straight line \(L1\) and the points \(p2\) on the straight line \(L2\). Then the approximate intersection coordinates \(p\) of the two lines are:

[0115]

[0116] Specifically, establishing the local three-dimensional coordinate system of each vertebral body according to the spatial positions of the ellipse fitted by the upper endplate, the ellipse fitted by the lower endplate and the transverse process described in step S7 includes:

[0117] For any vertebral body, define the midpoint of the line connecting the centers of the upper endplate and the lower endplate as the origin \(O\) of the coordinate system, and establish the local three-dimensional coordinate system of each vertebral body. The formula is as follows:

[0118]

[0119]

[0120]

[0121] where \(n1\) and \(n2\) are the normal vectors of the upper endplate and the lower endplate respectively, and \(p1\) and \(p2\) are the coordinates of the identified transverse processes in three-dimensional space. Taking the standing posture of the photographer as a reference, the direction of the vector \(Y\)-axis is vertically upward, the direction of the vector \(X\)-axis is forward, and the direction of the vector \(Z\)-axis is to the right.

[0122] Normalize the calculated results to obtain the three-dimensional coordinate system of each vertebral body

[0123] Use the transformation of the three-dimensional space coordinate system to calculate the slip degree, vertebral body flexion angle, vertebral body scoliosis angle and vertebral body axial rotation angle of any two vertebral bodies, so as to measure clinical parameters such as the Cobb angle of scoliosis and the apical vertebral rotation angle. The final reconstruction result refers to Figure 4As shown. Those skilled in the art can understand that the transformation method of the three-dimensional space coordinate system adopted in this embodiment is as follows: for any two local three-dimensional coordinate systems, calculate the rotation matrix and displacement vector of one coordinate system relative to the other coordinate system, so as to obtain the slip degree, vertebral body flexion angle, vertebral body scoliosis angle, and vertebral body axial rotation angle of any two vertebral bodies. Among them, the Cobb angle is the included angle between the perpendicular line of the upper edge of the cephalad end vertebra and the perpendicular line of the lower edge of the caudal end vertebra, and the apical vertebra is the vertebra that is the most horizontal, has the most severe rotation, and deviates the farthest from the midline in the curvature.

[0124] Embodiment Two

[0125] As Figure 5 shown, the present invention also provides an X-ray imaging three-dimensional spine model establishment device, which is applied to a biplane X-ray imaging system and includes:

[0126] An image acquisition module 100, configured to acquire biplane X-ray images of the human torso in different weight-bearing positions;

[0127] A feature point output module 200, configured to mark the position of each vertebral body feature point in the X-ray image, and the feature point position includes the corner point position and the transverse process position;

[0128] A space correction module 300, configured to perform space correction on the biplane X-ray imaging system, convert the biplane environment into a three-dimensional space coordinate, convert the second X-ray receiver plane coordinate system to the first X-ray receiver plane coordinate system, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver;

[0129] A feature point conversion module 400, configured to set the biplane X-ray image in the three-dimensional space according to the space coordinate conversion relationship between the first X-ray receiver plane coordinate system and the second X-ray receiver plane coordinate system, and convert the feature point position into three-dimensional space coordinates distributed on the biplane X-ray image;

[0130] A vertebral body construction module 500, configured to reconstruct the endplate fitting ellipse of the vertebral body and the spatial position of the transverse process according to multiple feature point positions, that is, calculate the position of the vertebral body structure in the three-dimensional space, and the position characteristics of the endplate fitting ellipse include the center position, normal vector, major axis vector, and minor axis vector of the upper endplate ellipse and the lower endplate ellipse;

[0131] A model output module 600, configured to set the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulate the geometric body formed by the upper endplate and the lower endplate using a triangulation algorithm, and construct each vertebral body into a cylinder-like body represented by a Delaunay triangulation network to complete the establishment of the three-dimensional spine model.

[0132] The X-ray imaging spinal three-dimensional model establishment device provided by the present invention improves the efficiency of establishing the spinal three-dimensional model. By marking the corner point positions and transverse process positions of each vertebral body in the X-ray images of the human torso from two perspectives, a 3D model of the spine can be quickly established according to the geometric relationship of the projections; only one double-plane X-ray photograph of the patient is required to complete data acquisition, and the radiation dose received by the patient is much lower than that of a plain spinal CT scan; a spinal three-dimensional model of the patient in the standing position can be established to ensure the accuracy of subsequent clinical parameter calculations; a spinal three-dimensional model under special movements can also be established according to the condition and surgical needs, providing convenience for clinical research.

[0133] Furthermore, this embodiment further includes: a clinical parameter output module, which is used to establish a local three-dimensional coordinate system of each vertebral body according to the spatial positions of the upper endplate fitting ellipse, the lower endplate fitting ellipse and the transverse process, and calculate the slip degree, vertebral body flexion angle, vertebral body scoliosis angle and vertebral body axial rotation angle between any two vertebral bodies by using the transformation of the three-dimensional space coordinate system, so as to measure clinical parameters such as the Cobb angle of scoliosis and the apical vertebral rotation angle.

[0134] The specific contents and implementation methods of the above image acquisition module 100, feature point output module 200, spatial correction module 300, feature point conversion module 400, vertebral body construction module 500, model output module 600 and clinical parameter output module are all as described in Embodiment 1, and will not be elaborated here.

[0135] Finally, in order to apply the above X-ray imaging spinal three-dimensional model establishment method to an image acquisition and generation system, device or equipment with relevant hardware conditions, the present application also provides a computer-readable storage medium, in which a computer program is loaded, and when the computer program is executed by a computer, it realizes the functions of the corresponding method embodiment as described above.

[0136] Similarly, the present application also protects a computer-readable storage medium loaded with a computer program for implementing the X-ray imaging spinal three-dimensional model establishment method.

[0137] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program. The computer program includes one or more computer programs. When the computer program is loaded and executed on a computer, the processes or functions described in the embodiments of the present disclosure are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer program can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer program can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (such as coaxial cable, optical fiber, DDL (Digital Dub DDriver Line, digital subscriber line)) or wirelessly (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that the computer can access or a data storage device such as a server or data center that includes one or more integrated available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, magnetic tape), an optical medium (such as a high-density DVD (Digital Video Disc)), or a semiconductor medium (such as a DDD (Solid State Disk, solid-state drive)), etc.

[0138] It should be noted that in the above embodiments, the terms used herein are merely for describing specific exemplary embodiments and are not intended to be restrictive. As used herein, the singular forms "a", "an", and "the or said" may also be intended to include the plural forms, unless the context clearly indicates otherwise. The terms "comprising", "including", and "having" are inclusive and thus specify the presence of the stated features, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or groups thereof. The method steps, processes, and operations described herein should not be construed as necessarily requiring the method steps, processes, and operations to be executed in the specific order discussed or shown, unless specifically specified to be executed in a set order. It should also be understood that additional or alternative steps may be employed.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for establishing a three-dimensional model of the spine for X-ray imaging, characterized in that, Applied to a biplane X-ray imaging system, it includes the following steps: Obtain biplane X-ray images of the human torso in different weight-bearing postures; Calibrate the positions of each vertebral characteristic point in the X-ray image, and the characteristic point positions include corner positions and transverse process positions; Perform spatial calibration on the biplane X-ray imaging system, convert the biplane environment into three-dimensional space coordinates, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver; Set the biplane X-ray image in three-dimensional space, and convert the characteristic point positions into three-dimensional space coordinates distributed in the biplane X-ray imaging space; Reconstruct the endplate fitting ellipse of the vertebral body and the spatial position of the transverse process according to multiple characteristic point positions, that is, calculate the position of the vertebral body structure in three-dimensional space. The position characteristics of the endplate fitting ellipse include the center positions, normal vectors, major axis vectors, and minor axis vectors of the upper endplate ellipse and the lower endplate ellipse; Set the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulate the geometric body formed by the upper endplate and the lower endplate, and construct each vertebral body as a cylinder-like body to complete the establishment of the three-dimensional spine model.

2. The method for establishing a three-dimensional model of the spine for X-ray imaging according to claim 1, wherein, It further includes: Establish the local three-dimensional coordinate system of each vertebral body according to the spatial positions of the upper endplate fitting ellipse, the lower endplate fitting ellipse, and the transverse process. For any two local three-dimensional coordinate systems, calculate the rotation matrix and displacement vector of one coordinate system relative to the other coordinate system, so as to obtain the slip degree, vertebral body flexion angle, vertebral body scoliosis angle, and vertebral body axial rotation angle between any two vertebral bodies.

3. The method for establishing a three-dimensional model of the spinal column for X-ray imaging according to claim 2, characterized in that The establishment of the local three-dimensional coordinate system of each vertebral body according to the spatial positions of the upper endplate fitting ellipse, the lower endplate fitting ellipse, and the transverse process includes: For any vertebral body, define the midpoint of the connection line between the centers of the upper endplate and the lower endplate as the origin of the coordinate system, and establish the local three-dimensional coordinate system of each vertebral body. The formula is as follows: Normalize the calculated results to obtain the three-dimensional coordinate system of each vertebral body Where, n1 and n2 are the normal vectors of the upper endplate and the lower endplate respectively, and p1 and p2 are the coordinates of the identified transverse processes in three-dimensional space.

4. The method for establishing a three-dimensional model of the spine for X-ray imaging according to claim 1, wherein Performing spatial calibration on the biplane X-ray imaging system, converting the biplane environment into three-dimensional space coordinates, and obtaining the relative position relationship between the first X-ray receiver and the second X-ray receiver includes: Define the positions and sizes of the first radiation source, the second radiation source, the first X-ray receiver, and the second X-ray receiver in the three-dimensional space coordinate system; A correction plate is arranged in front of the X-ray receiver, and the rotation matrix R of the coordinate system of the correction plate relative to the first X-ray receiver and the second X-ray receiver is obtained by using the following optimization method F1 , R F2 and the displacement vector V F1 , V F2 , and the formula is as follows: Calculate the relative spatial position between the first X-ray receiver and the second X-ray receiver according to coordinate transformation. The formula is as follows: where P pi is the position of the i-th lead point on the calibration plate obtained by the dual-plane X-ray imaging system, and P mi is the true position of the i-th lead point on the calibration plate; denote the coordinates in the plane coordinate system of the second X-ray receiver F2 as P F2 , and the coordinates in the plane coordinate system of the first X-ray receiver F1 as P F1 , and the local coordinates on the calibration plate as P L ; the rotation matrix R2to1 of the plane of the first X-ray receiver F1 relative to the plane of the second X-ray receiver F2 is and the displacement vector V2to1 is The superscript T represents the transpose matrix.

5. The method for establishing a three-dimensional model of the spine for X-ray imaging according to claim 1, wherein Setting the biplane X-ray image in three-dimensional space, and converting the characteristic point positions into three-dimensional space coordinates distributed in the biplane X-ray imaging space includes: Convert the two-dimensional corner position (x, y) or transverse process position (x, y) into the three-dimensional space coordinates P distributed on the bi-plane X-ray image through the spatial coordinate conversion relationship x，y，z , and the formula is as follows: where h is the height (number of pixels) of the dual-plane X-ray image, and w is its width (number of pixels). They respectively represent the coordinates of the upper-right, lower-right, upper-left, and lower-left corner points of the X-ray receiver in the three-dimensional coordinate system. c1 and c2 are calculation parameters.

6. The method for establishing a three-dimensional model of the spine for X-ray imaging according to claim 1, characterized in that, The reconstruction of the spatial position of the endplate fitting ellipse of the vertebral body according to multiple characteristic point positions includes: Obtain the coordinates F of the radiation source i =(F ix , F iy , F iz , ) and the radiation vector u i , and the straight line where the radiation is located is described as an equation about the variable s: L i = F i + s i · u i , where \(i = 1, 2\) represents two rays of the biplane, then the approximate intersection coordinates \(p\) of the two lines i = L i1 + s1·u1 = L i2 + s2·u2, and \([s1, s2]\) can be solved by the least squares method T : Wherein: After calculating [s1, s2] T Substitute them into the straight line L i expression respectively, to obtain the point p1 on the straight line L1 and the point p2 on the straight line L2. Then the approximate intersection coordinate p of the two straight lines is: Assume that the vector connecting the two corner points of the same endplate in the first shooting direction is The vector connecting the two corner points of the same endplate in the second shooting direction is The cross product formula for the line connecting the two corner points in the first shooting direction and the second shooting direction is as follows, which is used as the normal vector of the approximate ellipse of the vertebral endplate, with the direction vertically upward; Define the distance F from the radiation source to the center of the circle i The distance F from O to the midpoint of the line connecting the two angular points of the radiation source to the corresponding plane i The ratio r of C i As the scaling factor, define the direction of the line connecting the two angular points of one of the planes as the major axis vector, and define the cross product of the normal vector and the major axis vector as the minor axis vector. The length L of the major axis or the minor axis i Is the length CL of the line connecting the corresponding two angular points i The product with the corresponding scaling factor, and the calculation formula is as follows: L i = CL i × r i 。 7. The method for establishing a three-dimensional model of the spine for X-ray imaging according to claim 1, characterized in that, The reconstruction of the spatial position of the transverse process according to multiple characteristic point positions includes: Obtain the coordinates of the radiation source F i =(F ix , F iy , F iz ,) and the radiation vector u i , The straight line where the radiation is located is described as an equation about the variable s: L i = F i + s i · u i , where \(i = 1, 2\) represents two rays of the biplane, then the approximate intersection coordinates \(p\) of the two lines i = L i1 + s1·u1 = L i2 + s2·u2, and \([s1, s2]\) can be solved by the least squares method T : Wherein: Calculate [s1, s2] T After that, substitute them into the linear expression of Li respectively, and obtain the point p1 on the straight line L1 and the point p2 on the straight line L2. Then the approximate intersection coordinate p of the two straight lines is:

8. An X-ray imaging three-dimensional spinal model establishment device, characterized in that, Applied to a biplane X-ray imaging system, it includes: An image acquisition module for obtaining biplane X-ray images of the human torso in different weight-bearing postures; A feature point output module, configured to calibrate the positions of each vertebral feature point in the X-ray image, where the feature point positions include corner positions and transverse process positions; A spatial correction module, configured to perform spatial correction on the biplane X-ray imaging system, convert the biplane environment into three-dimensional space coordinates, and obtain the relative position relationship between the first X-ray receiver and the second X-ray receiver; A feature point conversion module, configured to set the biplane X-ray image in three-dimensional space and convert the feature point positions into three-dimensional space coordinates distributed in the biplane X-ray imaging space; A vertebral body construction module, configured to reconstruct the endplate fitting ellipse of the vertebral body and the spatial positions of the transverse processes according to multiple feature point positions, that is, calculate the position of the vertebral body structure in three-dimensional space, and the position features of the endplate fitting ellipse include the center positions, normal vectors, major axis vectors, and minor axis vectors of the upper endplate ellipse and the lower endplate ellipse; A model output module, configured to set the upper endplate fitting ellipse and the lower endplate fitting ellipse as point sets, triangulate the geometric body formed by the upper endplate and the lower endplate, and construct each vertebral body as a cylinder-like body to complete the establishment of the three-dimensional spine model.

9. A computer device, characterized in that, Comprising: A memory, which is used to store a processing program; A processor, when the processor executes the processing program, implements the X-ray imaging three-dimensional spine model establishment method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, A computer program for implementing the X-ray imaging three-dimensional spine model establishment method according to any one of claims 1-7 is loaded in the readable storage medium.

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