A cephalogram target point distance measurement method and system based on pixel coordinate transformation and geometric modeling

Abstract

The application provides a cephalogram target point distance measuring method and system based on pixel coordinate transformation and geometric modeling, which comprises the following steps: obtaining a to-be-measured cephalogram image containing at least three preset anatomical landmark points, and obtaining pixel coordinates of each anatomical landmark point; selecting at least two anatomical landmark points other than a target anatomical landmark point to construct an initial reference coordinate system; defining a target rotation angle, performing spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark point to obtain a corrected standardized calculation coordinate system and standardized calculation coordinates of each anatomical landmark point; and calculating a vertical pixel distance of each target anatomical landmark point to the corrected standardized calculation coordinate system according to the standardized calculation coordinates of each anatomical landmark point, and converting to obtain an actual physical measurement distance of each target anatomical landmark point.

Description

Technical Field

[0001] This invention belongs to the field of medical image processing, specifically relating to a method and system for calculating the distance to target points in cephalometric lateral radiographs based on pixel coordinate transformation and geometric modeling. Background Technology

[0002] Cephalometric analysis is an indispensable basic diagnostic tool in fields such as orthodontics, orthognathic surgery, and biomedical engineering. Since Broadbent pioneered lateral cephalometric radiography in 1931, this technique has provided quantitative evidence for the diagnosis, treatment planning, and prognostic assessment of dentofacial deformities by extracting key anatomical landmarks from two-dimensional X-ray images and constructing measurement items such as points, lines, angles, and planes. Its core diagnostic logic lies in objectively evaluating the developmental status and degree of abnormality of craniofacial morphology by accurately quantifying the spatial relationships between specific anatomical structures.

[0003] With the popularization of digital medical imaging technology, the traditional manual methods of tracing with tracing paper and measuring with vernier calipers have been replaced by computer-aided fixed-point distance measurement. However, the digitization of technology has not fundamentally solved a key problem in surveying—the geometric distortion and pose normalization of two-dimensional planar images. Currently, whether in commercial cephalometric software or through semi-automatic point positioning using general image viewers, after the marker points are calibrated, most systems directly use the Euclidean distance formula to simply calculate the pixel distance between two points, and then perform proportional conversion using the scale attached to the image. This direct linear measurement method implies an idealized premise: the anatomical structure to be measured is exactly located in a standard plane that is strictly perpendicular to the X-ray centerline, and the patient's head is not rotated or tilted during image acquisition.

[0004] However, in clinical practice, this ideal condition is almost impossible to meet. Lateral cephalometric radiographs require the patient's head to be fixed in place by a cranial locator, but slight postural deviations are unavoidable during the procedure. The patient's head pitching, lateral flexion, or rotation, as well as minute angular deviations during subsequent digital scanning, all cause varying degrees of perspective distortion and positional shift of the target anatomical structure on the two-dimensional projection plane. In this case, if the distance is measured directly using the image's pixel grid as a reference, the resulting distance will be an oblique projection in a tilted coordinate system, rather than the orthogonal projection distance on the standard anatomical reference plane required for clinical diagnosis. This measurement error caused by the inconsistency between the coordinate system and the standard anatomical reference axis is systematic and directly reduces the reliability of measurements such as the SNA angle, SNB angle, mandibular plane angle, and line distance, affecting the consistency of longitudinal comparisons and multicenter studies. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies in direct distance measurement under image tilt conditions, this invention provides a method and system for calculating the distance of target points in cephalometric images based on pixel coordinate transformation and geometric modeling. After the marker point is located in the image, a standard reference coordinate system is reconstructed using mathematical methods. The spatial relationship between the target point and the reference point is converted into digital coordinate information and geometric calculation is performed, thereby achieving high-precision distance measurement.

[0006] According to one aspect of the present invention, a method for calculating the distance to a target point in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling is provided, comprising the following steps:

[0007] Acquire a lateral cephalometric radiograph containing at least three preset anatomical landmarks, and obtain the pixel coordinates of each anatomical landmark;

[0008] Select at least two anatomical landmarks other than the target anatomical landmark to construct an initial reference coordinate system;

[0009] Define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark to obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark;

[0010] Based on the standardized calculated coordinates of each anatomical landmark, the vertical pixel distance from each target anatomical landmark to the corrected standardized calculated coordinate system is calculated, and the actual physical measurement distance of each target anatomical landmark is obtained.

[0011] As a further technical solution, the pixel coordinates of each anatomical landmark are obtained from the basic image pixel coordinate system; wherein, the basic image pixel coordinate system takes any corner point in the lateral view of the cephalogram to be tested as the origin, takes the horizontal rightward direction as the positive X-axis direction, and takes the vertical upward direction as the positive Y-axis direction.

[0012] As a further technical solution, the initial reference coordinate system is a polar coordinate system, and the construction process includes:

[0013] Select at least two anatomical landmarks as reference points. Using one of the reference points as the center, construct the initial reference coordinate system by using the line segment connecting the reference point as the center and the selected other reference point as the baseline line segment of the initial reference coordinate system.

[0014] As a further technical solution, the target rotation angle is the angle between the initial reference coordinate system and its preset standard posture.

[0015] As a further technical solution, the process of spatially transforming the initial reference coordinate system and the pixel coordinates of each anatomical landmark includes:

[0016] A two-dimensional planar rotation matrix is ​​constructed based on the target rotation angle. The center of the circle in the initial reference coordinate system is used as the rotation center reference. The pixel coordinates of each anatomical landmark are translated and rotated using the two-dimensional planar rotation matrix to obtain the standardized calculated coordinates of each anatomical landmark.

[0017] Based on the standardized calculated coordinates of the center of the initial reference coordinate system and the other endpoint of the baseline segment, the spatial position of the baseline segment after spatial transformation is determined, thereby constructing a corrected standardized calculated coordinate system.

[0018] As a further technical solution, the mathematical representation of a two-dimensional planar rotation matrix is:

[0019]

[0020] In the formula, Represents a two-dimensional planar rotation matrix; Rotate by the target angle.

[0021] As a further technical solution, the vertical pixel distance from the target anatomical landmark to the corrected standardized computational coordinate system is calculated based on the principles of analytical geometry, and mathematically expressed as:

[0022]

[0023] In the formula, This represents the vertical pixel distance from the target anatomical landmark to the corrected, normalized computational coordinate system: The standardized calculated coordinates of the target anatomical landmark A are represented.

[0024] According to another aspect of this specification, a system for calculating the distance to target points in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling is provided, comprising:

[0025] The data preparation layer is used to acquire cephalometric images containing at least three preset anatomical landmarks and to obtain the pixel coordinates of each anatomical landmark.

[0026] The reference system establishment layer is used to select at least two anatomical landmarks other than the target anatomical landmarks to construct an initial reference coordinate system.

[0027] The core transformation layer is used to define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark, and obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark.

[0028] The geometric quantization layer is used to calculate the vertical pixel distance from each target anatomical landmark to the calibrated standardized calculation coordinate system based on the standardized calculation coordinates of each anatomical landmark, and then convert it into the actual physical measurement distance of each target anatomical landmark.

[0029] According to another aspect of this specification, an electronic device is provided, including a memory and a processor, the memory storing program instructions executed by the processor, the processor invoking the program instructions to execute a method for calculating the distance to a target point in a cephalometric montage based on pixel coordinate transformation and geometric modeling.

[0030] According to another aspect of this specification, a non-transitory computer-readable storage medium is provided, the non-transitory computer-readable storage medium storing computer instructions that cause the computer to execute a method for calculating the distance to a target point in a cephalometric lateral view based on pixel coordinate transformation and geometric modeling.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention provides a spatial geometric measurement framework independent of the original pixel grid of the image, capable of orienting and correcting the reference coordinate system. This framework should not rely on specific software or automated algorithms, but rather serve as a general mathematical modeling process. After obtaining point coordinates generated in any way, it can eliminate the interference of image tilt and pose errors through standardized rotation matrix transformations, uniformly mapping all marker points to a standardized computational coordinate system defined by stable anatomical landmarks before distance measurement. The engineering implementation of this approach will effectively overcome the accuracy deficiencies of existing point-to-point direct distance measurement techniques, providing a more rigorous and reproducible digital analysis foundation for cephalometric measurement. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart illustrating a method for calculating the distance to a target point in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling, provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram illustrating the geometric principles of coordinate transformation and distance calculation in a specific embodiment of the present invention;

[0036] Figure 3 This is an example of the effect of calculating the coordinates of each point for coordinate correction and calculating the perpendicular distance to the target point in this invention;

[0037] Figure 4This is a schematic diagram of the structure of a target point distance calculation system for cephalometric lateral view film based on pixel coordinate transformation and geometric modeling, provided in an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0039] It should be noted that:

[0040] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be decomposed, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0043] like Figure 1 As shown, a method for calculating the distance to target points in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling includes the following steps:

[0044] Step 1: Obtain a lateral cephalometric radiograph containing at least three preset anatomical landmarks, and obtain the pixel coordinates of each anatomical landmark;

[0045] Step 2: Select at least two anatomical landmarks other than the target anatomical landmark to construct an initial reference coordinate system;

[0046] Step 3: Define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark to obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark.

[0047] Step 4: Based on the standardized calculation coordinates of each anatomical landmark, calculate the vertical pixel distance from the target anatomical landmark to the corrected standardized calculation coordinate system, and convert it to obtain the actual physical measurement distance of each target anatomical landmark.

[0048] In step 1, the pixel coordinates of each anatomical landmark are obtained from the basic image pixel coordinate system; wherein, the basic image pixel coordinate system takes any corner point in the lateral view of the cephalogram to be tested as the origin, the horizontal rightward direction as the positive X-axis direction, and the vertical upward direction as the positive Y-axis direction.

[0049] Optionally, in step 1, the corner point can be selected as the lower left corner edge point of the basic image pixel coordinate system as the origin, thus establishing the basic image pixel coordinate system. The two-dimensional coordinate values ​​of each preset marker point in the image under this image pixel coordinate system are obtained through manual marking or computer-aided recognition, and used as pixel coordinates.

[0050] In step 1, the pre-defined anatomical landmarks refer to specific anatomical structures of bones or teeth on the lateral cephalometric radiograph that have clear anatomical significance and can be accurately identified, including but not limited to: the sella point (S, the center point of the sella image), the nasal root point (N, the anterior point of the nasofrontal suture), the auricular point (P, the superior edge of the external auditory canal), the orbital point (Or, the lowest point of the lower edge of the orbit), and the skull base point (Ba, the midpoint of the anterior edge of the foramen magnum).

[0051] In a specific embodiment, step 1 includes: acquiring a digital image of a lateral cephalometric radiograph taken by X-ray. The lower left corner pixel of the image is set as the origin (0,0), with the horizontal direction to the right being the positive X-axis and the vertical direction upwards being the positive Y-axis. The operator records the pixel coordinates of key landmarks S (saddle point) and N (root of the nose) using image viewing software (or manual reading). For example, the coordinates are recorded as follows: S point: (887; 967), N point: (1349; 1042).

[0052] In step 2, the initial reference coordinate system is a polar coordinate system, and the construction process includes:

[0053] Select at least two anatomical landmarks as reference points. Using one of the reference points as the center, construct the initial reference coordinate system by using the line segment connecting the reference point as the center and the selected other reference point as the baseline line segment of the initial reference coordinate system.

[0054] Preferably, in step 2, two anatomical landmarks with substantial significance are selected, such as: selecting the line connecting points S and N, with the baseline segment representing the anterior skull base plane (SN plane), or selecting the line connecting points Or and P, with the baseline segment representing the orbitoauricular plane (FH plane). In this embodiment, the baseline segment is the line connecting points S and N.

[0055] In step 3, the target rotation angle The angle between the initial reference coordinate system and its preset standard posture is used to eliminate angular tilt caused by image acquisition or patient posture.

[0056] Furthermore, step 3, the process of spatial transformation of the initial reference coordinate system and the pixel coordinates of each anatomical landmark, includes:

[0057] A two-dimensional planar rotation matrix is ​​constructed based on the target rotation angle. The center of the circle in the initial reference coordinate system is used as the rotation center reference. The pixel coordinates of each anatomical landmark are translated and rotated using the two-dimensional planar rotation matrix to obtain the standardized calculated coordinates of each anatomical landmark.

[0058] Based on the standardized calculated coordinates of the center of the initial reference coordinate system and the other endpoint of the baseline segment, the spatial position of the baseline segment after spatial transformation is determined, thereby constructing the corrected standardized calculated coordinate system.

[0059] Specifically, the initial reference coordinate system is characterized by its baseline segment, and the standard orientation of the initial reference coordinate system is defined as the ideal position in space of the anatomical reference plane (such as the SN plane) represented by its baseline segment. During the coordinate transformation, the baseline segment is rotated clockwise around one endpoint as the center of rotation. After rotation, the baseline segment of the initial reference coordinate system coincides with or is parallel to the preset anatomical standard position.

[0060] The mathematical representation of the two-dimensional planar rotation matrix is ​​as follows:

[0061]

[0062] In the formula, Represents a two-dimensional planar rotation matrix; Rotate by the target angle.

[0063] Specifically, let the coordinates of point S be... The coordinates of point N are With point S as the center, rotate the baseline segment SN clockwise. The degree involves spatial transformation calculations. Taking point A as an example, the standardized calculated coordinates of the rotated point are mathematically represented as follows:

[0064]

[0065] In the formula, ( , ) represents the standardized calculated coordinates of point N.

[0066] In one specific embodiment, the coordinates of point S remain unchanged after the transformation, while point N moves to... Location, S This forms the corrected reference axis. Point S is selected as the center of the rotation reference circle, and the vector from point S to point N is calculated: To correct the SN line to the horizontal standard position (this example assumes the standard position needs to be rotated clockwise to the horizontal plane to conform to clinical measurement habits), a two-dimensional planar rotation matrix is ​​constructed. (See attached...) Figure 2 As shown, N is the nasal root point, S is the saddle point, the upper tooth socket point (A), and the lower tooth socket point (B). The SN plane is the original baseline, which is rotated by 7° to obtain the corrected reference axis. The coordinates of the rotated point N are shown below. Its standardized calculation coordinates ( , The calculation process can be expanded as follows:

[0067]

[0068]

[0069] The spatial transformation shown in this formula updates the initial reference coordinates of all anatomical landmarks using the same rotation matrix to maintain the consistency of the spatial topology.

[0070] In step 4, the vertical pixel distance from the target anatomical landmark to the corrected standardized computational coordinate system is calculated based on the principles of analytical geometry, and is mathematically expressed as:

[0071]

[0072] In the formula, This represents the vertical pixel distance from the target anatomical landmark to the corrected, normalized computational coordinate system: The standardized calculated coordinates of the target anatomical landmark A are represented.

[0073] Preferably, step 4 involves converting the actual physical distance using a scale: obtaining the scale information contained in the image (the ratio of the known physical size of the target object to its pixel size in the image). The vertical pixel distance calculated in step 4 is multiplied by the scale coefficient to finally output the actual physical distance of the target point, mathematically expressed as:

[0074]

[0075]

[0076] In the formula, The known actual physical dimensions of the calibration object; is the pixel size of the object in the image; scale is the actual physical scale corresponding to a unit pixel; D represents the actual physical distance.

[0077] In one specific embodiment, the actual distance represented by each pixel is calculated based on the scale attached to the edge of the lateral cephalometric image (e.g., a 10mm long metal sphere occupies 50 pixels in the image).

[0078]

[0079] The final actual distance is:

[0080]

[0081] This completes the precise calculation of the distance from image pixels to clinical anatomy, such as... Figure 3 The image shown is an example of coordinate correction and vertical distance calculation of the target point in a specific embodiment of the present invention, which is an example of constructing an initial reference coordinate system with points S and N.

[0082] The implementation of the various embodiments of the present invention is based on programmed processing through a system with processor functionality. Therefore, in practical engineering, the technical solutions and functions of the various embodiments of the present invention are encapsulated into various modules. Based on this reality, and building upon the above embodiments, the embodiments of the present invention provide a system for calculating the distance to a target point in a cephalometric lateral view based on pixel coordinate transformation and geometric modeling. This system is used to execute a method for calculating the distance to a target point in a cephalometric lateral view based on pixel coordinate transformation and geometric modeling from the above method embodiments.

[0083] See Figure 4 The system includes:

[0084] The data preparation layer is used to acquire cephalometric images containing at least three preset anatomical landmarks and to obtain the pixel coordinates of each anatomical landmark.

[0085] The reference system establishment layer is used to select at least two anatomical landmarks other than the target anatomical landmarks to construct an initial reference coordinate system.

[0086] The core transformation layer is used to define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark, and obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark.

[0087] The geometric quantization layer is used to calculate the vertical pixel distance from each target anatomical landmark to the calibrated standardized calculation coordinate system based on the standardized calculation coordinates of each anatomical landmark, and then convert it into the actual physical measurement distance of each target anatomical landmark.

[0088] It should be noted that the system embodiments provided by the present invention are used not only to implement the methods in the above method embodiments, but also to implement the methods in other method embodiments provided by the present invention. The only difference is that corresponding functional modules are set. The principle is basically the same as that of the above system embodiments provided by the present invention. As long as those skilled in the art can improve the modules in the above system embodiments by referring to the specific technical solutions in other method embodiments and combining technical features to obtain corresponding technical means and technical solutions composed of these technical means, on the basis of the above system embodiments, and on the premise of ensuring the practicality of the technical solutions, they can obtain corresponding system-like embodiments for implementing the methods in other method-like embodiments.

[0089] The method described in this invention is implemented using an electronic device; therefore, it is necessary to introduce the relevant electronic device. For this purpose, embodiments of this invention provide an electronic device, such as... Figure 5 As shown, the electronic device includes: at least one processor, a communication interface, at least one memory, and a communication bus, wherein the at least one processor, the communication interface, and the at least one memory communicate with each other via the communication bus. The at least one processor invokes logical instructions stored in the at least one memory to execute all or part of the steps of the methods provided in the foregoing method embodiments.

[0090] Furthermore, when the logical instructions in at least one of the aforementioned memories are implemented as software functional units and sold or used as independent products, they are stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, is embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (a personal computer, server, or network device) to execute all or part of the steps of the methods described in the various method embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks—various media for storing program code.

[0091] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, located in one place, or distributed across multiple network units. The purpose of this embodiment is achieved by selecting some or all of the modules according to actual needs. Those skilled in the art will understand and implement this without any inventive effort.

[0092] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0093] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0094] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0095] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0096] Based on the same technical concept as the foregoing embodiments, the present invention provides a non-transitory computer-readable storage medium that stores computer instructions that cause the computer to execute a method for calculating the distance to a target point in a cephalometric lateral view based on pixel coordinate transformation and geometric modeling.

[0097] In summary, this invention provides a method for calculating the distance to a target point in a lateral headshot image based on pixel coordinate transformation and geometric modeling. The method includes the following steps: 1) acquiring an image to be measured containing preset marker points and determining the pixel coordinates of each marker point; 2) selecting reference marker points to establish a reference coordinate system; 3) correcting the spatial orientation of the coordinate system using a rotation matrix to construct a standardized computational coordinate system; 4) calculating the pixel distance to the target point based on the spatial geometric relationship between the target point and the computational coordinate system; 5) converting the image scale to obtain the actual physical distance to the target point. This method does not rely on dedicated automated tools and software. By converting the spatial positional relationships in the image into digital coordinate information, it achieves accurate distance measurement using geometric transformation and mathematical modeling. It effectively eliminates measurement errors caused by differences in shooting angle and image placement, improves the accuracy and consistency of headshot distance calculation, and has good application and promotion prospects.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the distance to target points in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling, characterized in that, Includes the following steps: Acquire a lateral cephalometric radiograph containing at least three preset anatomical landmarks, and obtain the pixel coordinates of each anatomical landmark; Select at least two anatomical landmarks other than the target anatomical landmark to construct an initial reference coordinate system; Define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark to obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark; Based on the standardized calculated coordinates of each anatomical landmark, the vertical pixel distance from each target anatomical landmark to the corrected standardized calculated coordinate system is calculated, and the actual physical measurement distance of each target anatomical landmark is obtained.

2. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that, The pixel coordinates of each anatomical landmark are obtained from the basic image pixel coordinate system; wherein, the basic image pixel coordinate system takes any corner point in the lateral view of the cephalogram to be tested as the origin, takes the horizontal rightward direction as the positive X-axis direction, and takes the vertical upward direction as the positive Y-axis direction.

3. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that... The initial reference coordinate system is a polar coordinate system, and the construction process includes: Select at least two anatomical landmarks as reference points. Using one of the reference points as the center, construct the initial reference coordinate system by using the line segment connecting the reference point as the center and the selected other reference point as the baseline line segment of the initial reference coordinate system.

4. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that... The target rotation angle is the angle between the initial reference coordinate system and its preset standard posture.

5. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that, The process of spatial transformation of the initial reference coordinate system and the pixel coordinates of each anatomical landmark includes: A two-dimensional planar rotation matrix is ​​constructed based on the target rotation angle. The center of the circle in the initial reference coordinate system is used as the rotation center reference. The pixel coordinates of each anatomical landmark are translated and rotated using the two-dimensional planar rotation matrix to obtain the standardized calculated coordinates of each anatomical landmark. Based on the standardized calculated coordinates of the center of the initial reference coordinate system and the other endpoint of the baseline segment, the spatial position of the baseline segment after spatial transformation is determined, thereby constructing a corrected standardized calculated coordinate system.

6. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that, The mathematical representation of the two-dimensional plane rotation matrix is: ； In the formula, Represents a two-dimensional planar rotation matrix; Rotate by the target angle.

7. The method for calculating the distance to target points in a lateral headshot image based on pixel coordinate transformation and geometric modeling as described in claim 1, characterized in that, The vertical pixel distance from the target anatomical landmark to the calibrated normalized computational coordinate system is calculated based on analytical geometry principles and mathematically expressed as: ； In the formula, This represents the vertical pixel distance from the target anatomical landmark to the corrected, normalized computational coordinate system: The standardized calculated coordinates of the target anatomical landmark A are represented.

8. A system for calculating the distance to target points in a lateral cephalometric image based on pixel coordinate transformation and geometric modeling, characterized in that, include: The data preparation layer is used to acquire cephalometric images containing at least three preset anatomical landmarks and to obtain the pixel coordinates of each anatomical landmark. The reference system establishment layer is used to select at least two anatomical landmarks other than the target anatomical landmarks to construct an initial reference coordinate system. The core transformation layer is used to define the target rotation angle, perform spatial transformation on the initial reference coordinate system and the pixel coordinates of each anatomical landmark, and obtain the corrected standardized calculation coordinate system and the standardized calculation coordinates of each anatomical landmark. The geometric quantization layer is used to calculate the vertical pixel distance from each target anatomical landmark to the calibrated standardized calculation coordinate system based on the standardized calculation coordinates of each anatomical landmark, and then convert it into the actual physical measurement distance of each target anatomical landmark.

9. An electronic device, characterized in that, The method includes a memory and a processor, the memory storing program instructions that are executed by the processor, the processor invoking the program instructions to perform the method according to any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium stores computer instructions that cause the computer to perform the method described in any one of claims 1 to 7.

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