Method and device for generating panoramic curved surface fault film based on CBCT (cone beam computed tomography) image shot in simulated manner

Abstract

The invention relates to a method and a device for generating a panoramic curved-surface fault film based on a CBCT image shot in a simulated manner. The method comprises the following steps: S1, extracting a dental arch line for representing the dentition condition of a patient based on the CBCT image; s2, calculating parameters of simulation shooting; s3, simulating an X-ray rotation shooting process in an actual scene, and obtaining original data for panoramic curved surface tomography reconstruction from the CBCT image; and S4, reconstructing the original data used for panoramic curved surface fault reconstruction to obtain a panoramic curved surface fault slice. According to the method, the complete oral cavity panoramic image can be extracted from the CBCT image, the definition of the panoramic image can be improved through the characteristics of low dosage and high resolution of the three-dimensional image, and the radiation absorption of a panoramic curved surface fault piece additionally shot by a patient can be reduced. Various requirements of doctors on three-dimensional space images and two-dimensional plane images are met, and the diagnosis and treatment efficiency is improved. According to the method, the problem of data loss caused by improper slicing algorithm design or data processing errors can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oral image processing, and in particular to a method and device for generating panoramic curved surface tomograms based on simulated CBCT images. Background Art

[0002] CBCT (Cone Beam Computed Tomography) has an extremely low radiation dose, but can provide high-resolution images that clearly display the fine structure of teeth, jaws, and surrounding soft tissues. It is a patient-friendly oral examination method that greatly helps doctors. Oral panoramic curved surface tomography plays an irreplaceable role in routine oral examinations, examining tooth development, and judging deformities. Oral panoramic curved surface tomography based on CBCT images can obtain both three-dimensional spatial images and two-dimensional plane images based on a single shot, meeting doctors' various film reading needs in different diagnosis and treatment scenarios.

[0003] However, due to the problem of data loss caused by improper design or data processing errors in existing 3D slice algorithms, the generated panoramic curved slices will have the problem of detail loss, and the dentition morphology of different patients is different, which cannot be compensated by automatic calculation. The manual adjustment method not only requires a high level of medical skills, but also requires a certain understanding of the characteristics of panoramic generation, which is time-consuming and labor-intensive. Summary of the invention

[0004] The technical problem to be solved by the present invention is to design a method and device for generating panoramic curved surface tomograms based on simulated CBCT images, which can extract complete oral panoramic images from CBCT images, improve the clarity of panoramic images through the low-dose and high-resolution characteristics of three-dimensional images, and reduce the radiation absorption of patients by additional panoramic curved surface tomograms, thereby solving the existing technical problems.

[0005] In order to solve the above technical problems, the present invention provides a method for generating panoramic curved tomographic slices based on simulated CBCT images, comprising the following steps:

[0006] Step S1: extracting a dental arch line for representing the patient's dentition based on the CBCT image;

[0007] Step S2: Calculating parameters for simulated shooting based on the extracted dental arch line;

[0008] Step S3: simulating the process of X-ray rotation shooting in an actual scene, and obtaining raw data for panoramic curved surface tomographic reconstruction from the CBCT image;

[0009] Step S4: reconstructing the original data for panoramic curved surface tomographic reconstruction to obtain a panoramic curved surface tomographic slice.

[0010] Furthermore, step S1 specifically includes the following steps:

[0011] Step S11: performing a maximum intensity projection (MIP) on the coronal plane of the CBCT image to obtain a coronal plane MIP image;

[0012] Step S12: Mapping image pixel values ​​and performing histogram statistics;

[0013] Step S13: binarizing the coronal MIP image with the help of histogram statistics;

[0014] Step S14: Counting the pixel distribution in the binary image to determine the upper and lower jaw boundary;

[0015] Step S15: Take an image with a thickness of 4 cm at the boundary between the upper and lower jaws in the CBCT image to generate a cross-sectional MIP image;

[0016] Step S16: Binarizing the cross-sectional MIP image;

[0017] Step S17: dilate, erode and thin the binary image of the cross section to obtain a candidate dental arch line region;

[0018] Step S18: Identify endpoints and bifurcation points in the dental arch line;

[0019] Step S19: traverse from the endpoint to obtain all branch paths;

[0020] Step S20: Screen all branch paths to obtain the final dental arch line.

[0021] Furthermore, step S2 specifically includes the following steps:

[0022] Step S21: setting the shooting frame number, the distance between the ray source and the detector and the rotation axis, the imaging magnification, and the length and width of the shot image;

[0023] Step S22: performing spline interpolation on the dental arch line control points to make the number of points on the dental arch line consistent with the number of shooting frames;

[0024] Step S23: calculating different imaging depths of teeth at different positions;

[0025] Step S24: Calculate the shooting angle rotateAngle of each frame image i ;

[0026] Step S25: Calculate the rotation center rotateCenter for each frame shot i (x,y).

[0027] Furthermore, step S23 specifically includes the following steps:

[0028] Locate the point in the middle of the dental arch line, traverse from this point to both sides of the dental arch line, and calculate the distance from each point to the midpoint of the central incisor; then set the shooting depth at the incisor and the shooting depth at the molar, set the shooting depth of the point within three times the incisor width from the midpoint of the central incisor as the incisor shooting depth, and set the shooting depth of the point outside six times the incisor width from the midpoint of the central incisor as the molar shooting depth; the shooting depth of the point between three and six times the distance is calculated by spline interpolation

[0029] Furthermore, in step S24, when photographing, the photographing is performed in a direction perpendicular to the dental arch line, and the calculation formula is as follows:

[0030] rotateAngle i =cos -1 (Dot(yAxis,rayDir i ));

[0031] rayDir i =Cross(zAxis,archDir i );

[0032] archDir i =normalize(arch i+1 -arch i );

[0033] in,

[0034] rotateAngle i is the angle with the positive semi-axis of the Y axis, Dot(·) is the dot product operation, and yAxis is the unit vector in the positive direction of the Y axis;

[0035] rayDir i is the shooting direction, Cross(·) is the cross product operation, and zAxis is the unit vector in the positive direction of the Z axis;

[0036] archDir i is the tangent direction of the i-th point on the dental arch line, normalize(·) is the normalization operation, arch i is the i-th point on the dental arch line.

[0037] Furthermore, step S25 specifically includes the following steps:

[0038] rotateCenter i (x,y)={arch i (x)+o2t*sin(rotateAngle i ),arch i (y)-o2t*cos(rotateAngle i )};

[0039]

[0040] in,

[0041] arch i (x), arch i (y) is the X value and Y value of the current dental arch point;

[0042] o2t is the distance from the rotation center to the tooth;

[0043] rotateCenter i (x,y) is the coordinate of the rotation center;

[0044] s2d is the distance from the ray source to the detector;

[0045] zoomScale is the shooting magnification;

[0046] s2o is the distance from the ray source to the center of rotation.

[0047] Furthermore, step S3 specifically includes the following steps:

[0048] Step S31: Calculate the ray source position source(x,y) and the detector position detect(x,y) when the current frame image is captured;

[0049] Step S32: Acquire a simulated photographed image. The specific method is as follows:

[0050] The size of the detector is set according to the length and width of the captured image; the points on the detector are traversed, connected with the ray source, and the current light direction is calculated; starting from the ray source, stepping along the light direction, if the point is within the shooting depth range, the pixel of the point is accumulated, if not, the traversal is continued until it reaches the detector, and the accumulated value is used as the pixel value of the point; after the traversal is completed, a frame of captured image is obtained.

[0051] Furthermore, step S4 specifically includes the following steps:

[0052] Step S41: Calculate the panoramic stitching coefficient stitchPara i ;

[0053] Step S42: using the stitching coefficients, stitching the simulated images to obtain a single-layer panoramic curved surface tomogram;

[0054] Step S43: generating a multi-layer panoramic curved surface tomogram, adjusting the stitching coefficient according to the magnification, enlarging and reducing each n layer according to the ratio, and generating a total of 2n+1 layers of panoramic curved surface tomograms focused on different positions;

[0055] Step S44: processing the multi-layer panoramic curved surface slices into a uniform size;

[0056] Step S45: taking the clearest image blocks in each layer and stitching them into a final panoramic image;

[0057] Step S46: performing post-processing of noise reduction and enhancement on the image, and finally generating a clear panoramic curved surface tomogram.

[0058] Furthermore, step S42 specifically includes the following steps:

[0059] Step S421: Calculate the size of the panoramic curved surface slice. The height panoHeight of the panoramic curved surface slice is the height picHeight of the simulated captured image. The width panoWidth of the panoramic curved surface slice is calculated as follows:

[0060]

[0061] Among them, picWidth is the width of the simulated captured image;

[0062] Step S422: Place the center line of the first frame of simulated image at the picWidth / 2th column of the panoramic curved slice, and the center lines of the remaining simulated images at the position placeCenterLine i The calculation formula is:

[0063]

[0064] The present invention also provides a device for generating panoramic curved surface tomographic slices based on simulated CBCT images, comprising:

[0065] at least one processor; and

[0066] at least one memory in communication with the processor;

[0067] The memory stores instructions that can be executed by the processor, and the instructions are executed by the processor to enable the device to perform the aforementioned method of generating panoramic curved surface tomography based on simulated CBCT images.

[0068] Beneficial effects of the present invention:

[0069] The method and device for generating panoramic curved surface tomography based on simulated CBCT images provided by the present invention can extract complete oral panoramic images from CBCT images, which can not only improve the clarity of panoramic images through the low-dose and high-resolution characteristics of three-dimensional images, but also reduce the radiation absorption of patients by additional panoramic curved surface tomography. It can meet the various needs of doctors for three-dimensional space images and two-dimensional plane images and improve the efficiency of diagnosis and treatment.

[0070] Compared with the existing algorithm for performing slice calculations to obtain panoramic curved tomographic slices from CBCT, the present invention can effectively solve the problem of data loss caused by improper slice algorithm design or data processing errors. By locating the focus layer of each part of the oral cavity through multi-layer panoramic positioning, the clarity of the image can be effectively improved and more anatomical details can be captured. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The specific implementation of the present invention will be further explained below in conjunction with the accompanying drawings.

[0072] Figure 1 A flow chart of a method for generating panoramic curved tomographic slices based on simulated CBCT images of the present invention;

[0073] Figure 2 A flow chart of the method for extracting the dental arch wire in the present invention;

[0074] Figure 3 A flow chart of a method for calculating parameters of simulated shooting in the present invention;

[0075] Figure 4 A flow chart of the method for reconstructing data to obtain a panoramic curved surface tomogram in the present invention;

[0076] Figure 5 It is a demonstration diagram of calculating the splicing coefficient in the present invention. DETAILED DESCRIPTION

[0077] Example 1

[0078] Combination Figure 1 The method of generating a panoramic curved surface tomogram based on simulated CBCT images of this embodiment includes the following steps:

[0079] Step S1: Based on the CBCT image, extract the dental arch line used to represent the patient's dentition.

[0080] In this embodiment, preferably, Figure 2 As shown, step S1 specifically includes the following steps:

[0081] Step S11: Perform a coronal maximum intensity projection (MIP) on the CBCT image to obtain a coronal MIP image.

[0082] Step S12: Map the image pixel values ​​and perform histogram statistics.

[0083] Step S13: binarizing the coronal MIP image with the help of histogram statistics.

[0084] In this embodiment, according to statistics, the physical area of ​​the tooth is set to 20 cm 2 , use this value to calculate the area occupied by the tooth in the coronal projection image, and then accumulate the number of pixels from the highest intensity to the lowest intensity of the histogram until the tooth area is covered, and use the current pixel intensity as the threshold to binarize the coronal MIP image.

[0085] Step S14: Counting the pixel distribution in the binary image to determine the upper and lower jaw boundary.

[0086] Specifically, in this embodiment, the binary image of the coronal plane is projected onto the Y axis to generate a Y axis histogram to determine the distribution of teeth on the Y axis. The highest peak in the Y axis histogram is identified as the boundary between the upper and lower jaws.

[0087] Step S15: Take an image with a thickness of 4 cm at the boundary between the upper and lower jaws in the CBCT image to generate a cross-sectional MIP image.

[0088] Step S16: Binarize the cross-sectional MIP image.

[0089] In this embodiment, according to statistics, the physical area of ​​the tooth is set to 20 cm 2 , use this value to calculate the area occupied by the tooth in the cross-sectional projection image, and then accumulate the number of pixels from the highest intensity to the lowest intensity of the histogram until the tooth area is covered, and use the current pixel intensity as the threshold to binarize the cross-sectional MIP image.

[0090] Step S17: dilate, erode and thin the binary image of the cross section to obtain a candidate dental arch line region.

[0091] Step S18: Identify endpoints and bifurcation points in the dental arch line.

[0092] Specifically, in this embodiment, each point on the dental arch line is traversed, and the points in its eight-connected domain that are also dental arch lines are stored. If only one point is stored in the eight-connected domain, the point is an endpoint; if three or more points are stored in the eight-connected domain, the point is defined as a bifurcation point.

[0093] Step S19: Traverse from the endpoint to obtain all branch paths.

[0094] Specifically, in this embodiment, starting from the leftmost endpoint, walk down along the neighborhood points stored in the eight-connected domain, and iterate continuously. If a bifurcation point is encountered, walk down from different neighborhood directions respectively; if an endpoint is encountered, the traversal of the current path ends. Repeat the above process until all endpoints have been traversed.

[0095] Step S20: Screen all branch paths to obtain the final dental arch line.

[0096] Specifically, in this embodiment, among all the branches obtained, if the starting and ending points are the same, only the longest one is selected; if the starting and ending points are different, they are saved and stored in ascending order of the X value of the starting point. Finally, the stored branches are connected as the final dental arch line.

[0097] The dental arch line is sampled at intervals to obtain the dental arch line control points.

[0098] Step S2: Calculating parameters for simulated photography based on the extracted dental arch line.

[0099] In this embodiment, preferably, Figure 3 As shown, step S2 specifically includes the following steps:

[0100] Step S21: setting the shooting frame number, the distance between the ray source and the detector and the rotation axis, the imaging magnification, and the length and width of the shot image.

[0101] Step S22: performing spline interpolation on the dental arch line control points to make the number of points on the dental arch line consistent with the number of shooting frames.

[0102] Step S23: Calculate different imaging depths of teeth at different positions.

[0103] In this embodiment, preferably, step S23 specifically includes the following steps:

[0104] Locate the point in the middle of the dental arch line, which is generally the midpoint of the central incisor. Start from this point and traverse both sides of the dental arch line to calculate the distance from each point to the midpoint of the central incisor. Then set the shooting depth at the incisor and the shooting depth at the molar. Set the shooting depth of the point within three times the incisor width from the midpoint of the central incisor as the incisor shooting depth, and set the shooting depth of the point outside six times the incisor width from the midpoint of the central incisor as the molar shooting depth. The shooting depth of the points between three and six times the distance is calculated by spline interpolation.

[0105] Step S24: Calculate the shooting angle rotateAngle of each frame image i .

[0106] In this embodiment, preferably, in step S24, in order to reduce tooth overlap in the panoramic curved surface tomography, the shooting is performed in a direction perpendicular to the dental arch line, and the calculation formula is as follows:

[0107] rotateAngle i =cos -1 (Dot(yAxis,rayDir i ));

[0108] rayDir i =Cross(zAxis,archDir i );

[0109] archDir i =normalize(arch i+1 -arch i );

[0110] in,

[0111] rotateAngle i is the angle with the positive semi-axis of the Y axis, Dot(·) is the dot product operation, and yAxis is the unit vector in the positive direction of the Y axis;

[0112] rayDir i is the shooting direction, Cross(·) is the cross product operation, and zAxis is the unit vector in the positive direction of the Z axis;

[0113] archDir i is the tangent direction of the i-th point on the dental arch line, normalize(·) is the normalization operation, arch i is the i-th point on the dental arch line.

[0114] Step S25: Calculate the rotation center rotateCenter for each frame shot i (x,y).

[0115] In this embodiment, preferably, step S25 specifically includes the following steps:

[0116] rotateCenter i (x,y)={arch i (x)+o2t*sin(rotateAngle i ),arch i (y)-o2t*cos(rotateAngle i )};

[0117]

[0118] in,

[0119] arch i (x), arch i (y) is the X value and Y value of the current dental arch point;

[0120] o2t is the distance from the rotation center to the tooth;

[0121] rotateCenter i (x,y) is the coordinate of the rotation center;

[0122] s2d is the distance from the ray source to the detector;

[0123] zoomScale is the shooting magnification;

[0124] s2o is the distance from the ray source to the center of rotation.

[0125] Step S3: Simulate the process of X-ray rotation shooting in an actual scene to obtain raw data for panoramic curved surface tomographic reconstruction from the CBCT image.

[0126] In this embodiment, preferably, step S3 specifically includes the following steps:

[0127] Step S31: Calculate the ray source position source(x,y) and the detector position detect(x,y) when the current frame image is captured.

[0128] Specifically, in the present embodiment, in actual shooting, the ray source is a device that emits X-rays, and the detector is a device that receives X-rays. In simulated shooting, the ray source represents the starting point for taking values ​​from the CBCT image, and the detector is the end point for taking values. Since X-rays are divergent, the detector receives light within an area. When calculating the detector position, its center position is calculated. The calculation formula is as follows:

[0129] source(x,y)={rotateCenter(x)+s2o*sin(rotateAngle),rotateCenter(y)-s2o*cos(rotateAngle)};

[0130] detect(x,y)={rotateCenter(x)-o2d*sin(rotateAngle),rotateCenter(y)+o2d*cos(rotateAngle)};

[0131] in,

[0132] rotateCenter(x) and rotateCenter(y) are the X and Y values ​​of the current rotation center coordinates;

[0133] s2o is the distance from the ray source to the rotation center;

[0134] rotateAngle is the shooting angle of the current frame image;

[0135] o2d is the distance from the detector to the center of rotation.

[0136] Step S32: Acquire a simulated photographed image. The specific method is as follows:

[0137] The size of the detector is set according to the length and width of the captured image; the points on the detector are traversed, connected with the ray source, and the current light direction is calculated; starting from the ray source, stepping along the light direction, if the point is within the shooting depth range, the pixel of the point is accumulated, if not, the traversal is continued until it reaches the detector, and the accumulated value is used as the pixel value of the point; after the traversal is completed, a frame of captured image is obtained.

[0138] Step S4: reconstructing the original data for panoramic curved surface tomographic reconstruction to obtain a panoramic curved surface tomographic slice.

[0139] In this embodiment, preferably, Figure 4 As shown, step S4 specifically includes the following steps:

[0140] Step S41: Calculate the panoramic stitching coefficient stitchPara i .

[0141] Specifically, in this embodiment, the stitching coefficient refers to the distance that the imaging position of an object captured at the center position of the previous frame of image in the next frame of image deviates from the center line. During the simulation shooting, a small area centered on the currently photographed point on the dental arch line is shot. Figure 5 As shown in the figure, when the point A1 on the dental arch line is photographed, the point is located at the center A1' in Pic1; when the point A2 on the dental arch line is photographed, A1 will deviate from the center line by a certain distance in the Pic2 image and be located at A1", and the distance from A1" to A2' is the stitching coefficient. The calculation process is as follows:

[0142] Step 1: Calculate the position of the ray source when shooting point A2.

[0143] source2=rotateCenter2-s2o*rayDir2;

[0144] Step 2: Calculate the connection direction between source2 and A1.

[0145] rayDir 21 =A1-source2;

[0146] Step 3: Use the law of cosines to calculate the angle between the current light and the line connecting A1-source2.

[0147]

[0148] Step 4: Calculate the length of source2-A1″

[0149] len = s2d / cosθ;

[0150] Step 5: Calculate A1″ coordinates

[0151] A1''=source2+len*rayDir 21 ;

[0152] Step 6: Calculate the distance A1″-A2′ to obtain the splicing coefficient

[0153] stitchPara2=distance(A2′,A1'').

[0154] Step S42: Using the stitching coefficients, the simulated images are stitched together to obtain a single-layer panoramic curved surface tomogram.

[0155] In this embodiment, preferably, step S42 specifically includes the following steps:

[0156] Step S421: When stitching, first calculate the size of the panoramic curved surface slice. The height panoHeight of the panoramic curved surface slice is the height picHeight of the simulated captured image. The calculation formula of the width panoWidth of the panoramic curved surface slice is as follows:

[0157]

[0158] Among them, picWidth is the width of the simulated captured image;

[0159] Step S422: Place the center line of the first frame of simulated image in the picWidth / 2th column of the panoramic curved slice. The center line of the second frame of image is stitchPara1 away from the center line of the first frame of image, so place the center line of the second frame of image at picWidth / 2+stitchPara1. Similarly, the center lines of the remaining simulated images are placed at placeCenterLine i The calculation formula is:

[0160]

[0161] Step S43: Generate multi-layer panoramic curved surface tomography. Since the teeth are tilted in the alveolar socket, the distances from the cusps and roots to the radiation source are different, and the actual magnification of the imaging on the detector is also different, resulting in the inability to clearly image both on the same layer of panoramic curved surface tomography at the same time. Adjust the stitching coefficient according to the magnification, enlarge and reduce each n layer according to the ratio, and generate a total of 2n+1 layers of panoramic curved surface tomography focused on different positions. The length of permanent teeth in Chinese adults is in the range of 2-3 cm, and the angle between the long axis of the maxillary anterior teeth and the maxillary plane is usually 108 degrees. It can be calculated that the projection width of the maxillary teeth on the occlusal plane is in the range of 0.6-1.0 cm. In order to avoid errors caused by individual differences, the projection width is set to 0.5-1.1 cm. Therefore, the relationship between the zoom ratio and the number of shooting layers is:

[0162] scale = (1.1-0.5) / 2n.

[0163] Step S44: Process the multi-layer panoramic curved surface slices into a uniform size.

[0164] Specifically, in this embodiment, due to different stitching coefficients, the sizes of the panoramic curved surface slices obtained by stitching are also different. The size of the single-layer panoramic curved surface slice is used as a standard to adjust the size of the multi-layer panoramic curved surface slice.

[0165] Step S45: Take the clearest image blocks in each layer and stitch them into a final panoramic image.

[0166] Specifically, in this embodiment, the multi-layer panoramic curved surface tomograms are divided into m*n small blocks, and then the clarity of the small blocks at the same position in the multi-layer panoramic curved surface tomograms is compared.

[0167] In this embodiment, the clarity calculation takes the Brenner gradient method as an example, and the calculation formula is as follows:

[0168] D(f)=∑ x,y [(f(x+1,y)-f(x,y)) 2 +(f(x,y+1)-f(x,y)) 2 ];

[0169] Where D(f) is the result of image clarity calculation, and f(x,y) represents the grayscale value of the pixel point (x,y) corresponding to image f.

[0170] The greater the change in pixel value in the image, the clearer the image. The image blocks with the highest clarity in each position are stitched together to form the final result image.

[0171] Step S46: performing post-processing of noise reduction and enhancement on the image, and finally generating a clear panoramic curved surface tomogram.

[0172] Example 2

[0173] The device of this embodiment for generating panoramic curved tomographic slices based on simulated CBCT images includes:

[0174] at least one processor; and

[0175] at least one memory in communication with the processor;

[0176] The memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the device to execute the method of generating panoramic curved surface tomography based on simulated CBCT images in Example 1.

[0177] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for generating panoramic curved tomographic slices based on simulated CBCT images, characterized in that: The steps include: Step S1: extracting a dental arch line for representing the patient's dentition based on the CBCT image; Step S2: Calculating parameters for simulated shooting based on the extracted dental arch line; Step S3: simulating the process of X-ray rotation shooting in an actual scene, and obtaining raw data for panoramic curved surface tomographic reconstruction from the CBCT image; Step S4: reconstructing the original data for panoramic curved surface tomographic reconstruction to obtain a panoramic curved surface tomographic slice.

2. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 1, characterized in that: Step S1 specifically includes the following steps: Step S11: performing coronal maximum intensity projection on the CBCT image to obtain a coronal MIP image; Step S12: Mapping image pixel values ​​and performing histogram statistics; Step S13: binarizing the coronal MIP image with the help of histogram statistics; Step S14: Counting the pixel distribution in the binary image to determine the upper and lower jaw boundary; Step S15: Take an image with a thickness of 4 cm at the boundary between the upper and lower jaws in the CBCT image to generate a cross-sectional MIP image; Step S16: Binarizing the cross-sectional MIP image; Step S17: dilate, erode and thin the binary image of the cross section to obtain a candidate dental arch line region; Step S18: Identify endpoints and bifurcation points in the dental arch line; Step S19: traverse from the endpoint to obtain all branch paths; Step S20: Screen all branch paths to obtain the final dental arch line.

3. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 1, characterized in that: Step S2 specifically includes the following steps: Step S21: setting the shooting frame number, the distance between the ray source and the detector and the rotation axis, the imaging magnification, and the length and width of the shot image; Step S22: performing spline interpolation on the dental arch line control points to make the number of points on the dental arch line consistent with the number of shooting frames; Step S23: calculating different imaging depths of teeth at different positions; Step S24: Calculate the shooting angle rotateAngle of each frame image i ; Step S25: Calculate the rotation center rotateCenter for each frame shot i (x,y).

4. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 3, characterized in that: Step S23 specifically includes the following steps: Locate the point in the middle of the dental arch line, traverse from this point to both sides of the dental arch line, and calculate the distance from each point to the midpoint of the central incisor; then set the shooting depth at the incisor and the shooting depth at the molar, set the shooting depth of the point within three times the incisor width from the midpoint of the central incisor as the incisor shooting depth, and set the shooting depth of the point outside six times the incisor width from the midpoint of the central incisor as the molar shooting depth; the shooting depth of the points between three and six times the distance is calculated by spline interpolation.

5. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 3, characterized in that: In step S24, when photographing, the photographing is performed in a direction perpendicular to the dental arch line, and the calculation formula is as follows: rotateAngle i =cos -1 (Dot(yAxis,rayDir i )); rayDir i =Cross(zAxis,archDir i ); archDir i =normalize(arch i+1 -arch i ); in, rotateAngle i is the angle with the positive semi-axis of the Y axis, Dot(·) is the dot product operation, and yAxis is the unit vector in the positive direction of the Y axis; rayDir i is the shooting direction, Cross(·) is the cross product operation, and zAxis is the unit vector in the positive direction of the Z axis; archDir i is the tangent direction of the i-th point on the dental arch line, normalize(·) is the normalization operation, arch i is the i-th point on the dental arch line.

6. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 3, characterized in that: Step S25 specifically includes the following steps: rotateCenter i (x,y)={arch i (x)+o2t*sin(rotateAngle i ),arch i (y)-o2t*cos(rotateAngle i )}; in, arch i (x), arch i (y) is the X value and Y value of the current dental arch point; o2t is the distance from the rotation center to the tooth; rotateCenter i (x,y) is the coordinate of the rotation center; s2d is the distance from the ray source to the detector; zoomScale is the shooting magnification; s2o is the distance from the ray source to the center of rotation.

7. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 1, characterized in that: Step S3 specifically includes the following steps: Step S31: Calculate the ray source position source(x,y) and the detector position detect(x,y) when the current frame image is captured; Step S32: Acquire a simulated photographed image. The specific method is as follows: The size of the detector is set according to the length and width of the captured image; the points on the detector are traversed, connected with the ray source, and the current light direction is calculated; starting from the ray source, stepping along the light direction, if the point is within the shooting depth range, the pixel of the point is accumulated, if not, the traversal is continued until it reaches the detector, and the accumulated value is used as the pixel value of the point; after the traversal is completed, a frame of captured image is obtained.

8. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 1, characterized in that: Step S4 specifically includes the following steps: Step S41: Calculate the panoramic stitching coefficient stitchPara i ; Step S42: using the stitching coefficients, stitching the simulated images to obtain a single-layer panoramic curved surface tomogram; Step S43: generating a multi-layer panoramic curved surface tomogram, adjusting the stitching coefficient according to the magnification, enlarging and reducing each n layer according to the ratio, and generating a total of 2n+1 layers of panoramic curved surface tomograms focused on different positions; Step S44: processing the multi-layer panoramic curved surface slices into a uniform size; Step S45: taking the clearest image blocks in each layer and stitching them into a final panoramic image; Step S46: performing post-processing of noise reduction and enhancement on the image, and finally generating a clear panoramic curved surface tomogram.

9. The method for generating panoramic curved tomographic slices based on simulated CBCT images according to claim 8, characterized in that: Step S42 specifically includes the following steps: Step S421: Calculate the size of the panoramic curved surface slice. The height panoHeight of the panoramic curved surface slice is the height picHeight of the simulated captured image. The width panoWidth of the panoramic curved surface slice is calculated as follows: Among them, picWidth is the width of the simulated captured image; Step S422: Place the center line of the first frame of simulated image at the picWidth / 2th column of the panoramic curved slice, and the center lines of the remaining simulated images at the position placeCenterLine i The calculation formula is:

10. A device for generating panoramic curved tomographic slices based on simulated CBCT images, characterized in that: include: at least one processor; as well as at least one memory in communication with the processor; The memory stores instructions executable by the processor, and the instructions are executed by the processor so that the device executes the method for generating panoramic curved tomograms based on simulated CBCT images as described in any one of claims 1 to 9.

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