Method and system for resolving optimal positioning parameters of X-ray bulb tube during dental apical film projection

Abstract

The invention discloses an X-ray bulb tube optimal positioning parameter resolving method and system during dental apical film projection, a dental three-dimensional model of a patient is constructed based on dental three-dimensional image data of the patient, scenes of the patient during apical film shooting under actual conditions are simulated based on the dental three-dimensional model, and the optimal positioning parameters of the X-ray bulb tube during projection of different tooth apical films are accurately measured. And the optimal positioning parameters of the X-ray bulb tube are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of dental examination, and in particular relates to a method and system for calculating optimal positioning parameters of an X-ray tube during dental periapical radiography. Background Art

[0002] Plain X-ray is the most commonly used examination method in current dental clinical applications, and periapical film is the most commonly used dental plain X-ray. A commonly used projection technique when taking periapical films is the angled projection technique.

[0003] When using the angle line technique to take periapical films, the operator first places the imaging plate on the lingual or palatal side of the tooth to be filmed, and then adjusts the position and angle of the X-ray tube so that the center line of the X-ray is perpendicular to the angle bisector plane of the angle formed by the long axis plane of the tooth and the imaging plate plane. Only in this way can a high-quality periapical film be projected.

[0004] However, humans generally have 28 to 32 teeth, including upper and lower incisors, canines, premolars, and molars. When projecting different types and positions of teeth, the optimal placement and angle of the X-ray tube are also different. This involves two sets of key parameters to be measured: the inclination angle of the X-ray tube involved in projecting different tooth positions and the position on the human body surface that the center of the X-ray tube needs to be aligned with.

[0005] The tilt angle of the X-ray tube is usually obtained by experience or by measuring with a cadaver skull specimen; the position of the human body surface that the center of the X-ray tube is aligned with is concluded by experience. It can be seen that the previous methods for obtaining these two parameters in the prior art are inaccurate and highly subjective. The measurement using a cadaver skull specimen is difficult to operate, cannot measure a large sample size, and has certain ethical concerns.

[0006] Therefore, in view of the above problems existing in the prior art, the present invention discloses a method and system for calculating the optimal positioning parameters of an X-ray tube when taking dental periapical radiographs. Summary of the invention

[0007] The purpose of the present invention is to provide a method and system for calculating the optimal positioning parameters of an X-ray tube when taking dental periapical films, to construct a dental three-dimensional model of the patient based on the patient's dental three-dimensional imaging data, to simulate the scene of the patient taking periapical films under actual circumstances based on the dental three-dimensional model, and to accurately measure the optimal positioning parameters of the X-ray tube when taking periapical films of different tooth positions.

[0008] The present invention is achieved through the following technical solutions:

[0009] A method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography is provided. The patient's dental three-dimensional imaging data is obtained, a dental three-dimensional model of the patient is generated based on the dental three-dimensional imaging data, and crown alignment and tooth position adjustment are performed based on the dental three-dimensional model. A digital imaging plate model and a digital X-ray centerline model are established. The digital imaging plate model is placed according to the tooth position projection requirements, a feature surface is established based on the positional relationship between the tooth position and the digital imaging plate model, and the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface are calculated through the positional relationship between the feature surface and the digital X-ray centerline model.

[0010] In order to better implement the present invention, further, the following steps are specifically included:

[0011] Step 1, obtaining dental 3D image data of the patient, wherein the dental 3D image data includes 3D scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue, as well as intraoral optical scanning data of the upper and lower jaws of the dentition, gums, and mucosal tissues in the mouth;

[0012] Step 2: Generate three-dimensional surface data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue based on the three-dimensional scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue; create a digital imaging plate model and a digital X-ray centerline model;

[0013] Step 3: Using the three-dimensional surface data of the dentition as a fixed reference, floating adjustment is performed on the optical scanning data of the dentition in the mouth to achieve model registration of the crown part;

[0014] Step 4: Based on different tooth positions, the median sagittal plane of the craniomaxillofacial bone tissue is established through the three-dimensional surface data of the craniomaxillofacial bone tissue, and the median sagittal plane of the craniomaxillofacial bone tissue is made perpendicular to the horizontal plane; then the dentition position is adjusted so that the upper dentition occlusal plane is parallel to the horizontal plane or the lower dentition occlusal plane is parallel to the horizontal plane;

[0015] Step 5: Place the digital imaging plate model and the digital X-ray centerline model according to the projection requirements of different tooth positions, and establish a feature surface based on the positional relationship between the tooth position and the digital imaging plate model. Calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface through the positional relationship between the feature surface and the digital X-ray centerline model.

[0016] In order to better implement the present invention, further, the step 5 of calculating the inclination angle parameter of the X-ray tube specifically includes:

[0017] Step S1, obtaining an image plate feature plane A parallel to a side plane of the digital image plate model close to the teeth based on contact characteristics fitting between a side plane of the digital image plate model close to the teeth and the teeth;

[0018] Step S2, selecting feature points on the teeth at the current tooth position, and obtaining the tooth long axis plane B at the current tooth position by fitting the feature points;

[0019] Step S3, generating an angle bisector plane C formed by an angle between the characteristic plane of the image plate and the long axis plane of the tooth;

[0020] Step S4, based on the world coordinate system, establish a first reference plane D perpendicular to the Z axis of the world coordinate system, and establish a second reference plane E perpendicular to the X axis of the world coordinate system;

[0021] Step S5, measuring the first angle between the angle bisector plane C and the first reference plane D, and measuring the second angle between the tooth long axis plane B and the second reference plane E; calculating the vertical inclination angle of the X-centerline model based on the first angle, and calculating the horizontal inclination angle of the X-centerline model based on the second angle.

[0022] In order to better implement the present invention, further, the step 5 of calculating the position parameters of the X-ray tube center aligned with the human body surface specifically includes:

[0023] Step K1, obtaining an image plate feature plane A parallel to a side plane of the digital image plate model close to the teeth based on contact feature fitting between a side plane of the digital image plate model close to the teeth and the teeth;

[0024] Step K2, selecting feature points on the teeth at the current tooth position, and obtaining the tooth long axis plane B at the current tooth position by fitting the feature points;

[0025] Step K3, generating an angle bisector plane C formed by the angle between the feature plane of the image plate and the long axis plane of the tooth;

[0026] Step K4, based on the world coordinate system, establish a first reference plane D perpendicular to the Z axis of the world coordinate system, and establish a second reference plane E perpendicular to the X axis of the world coordinate system;

[0027] Step K5, moving the X-ray centerline model so that the axis of the X-ray centerline model is perpendicular to the angle bisector plane C and passes through the middle of the root of the tooth being projected; extracting the focus where the axis of the X-ray centerline model intersects with the facial soft tissue;

[0028] Step K6, using the points beside the nose wings, inner canthus points, and outer canthus points in the three-dimensional surface data of the facial soft tissue as reference points, measure the horizontal distance and vertical distance between the focus and each reference point, and calculate the position parameters of the X-ray tube center aligned with the human body surface based on the horizontal distance and the vertical distance.

[0029] In order to better implement the present invention, further, placing the digital imaging plate model according to the projection requirements of different tooth positions in step 5 specifically includes:

[0030] Step T1, placing the digital imaging plate model close to the lingual side or palatal side of the tooth to be imaged;

[0031] Step T2: When projecting the front teeth, place the digital imaging plate model vertically so that the edge of the digital imaging plate model is 5-7 mm higher than the incisal edge of the projected teeth;

[0032] Step T3: When projecting the posterior teeth, place the digital imaging plate model horizontally so that the edge of the digital imaging plate model is 10-12 mm higher than the occlusal surface of the projected teeth.

[0033] In order to better implement the present invention, further, in step 3, the root mean square distance of the morphological difference between the partial registration model of the crown and the clinical optimal registration model of the crown is calculated so that the root mean square distance is less than or equal to 0.5 mm.

[0034] The invention discloses a system for calculating the optimal positioning parameters of an X-ray tube during dental periapical film projection, which is used to realize a method for calculating the optimal positioning parameters of an X-ray tube during dental periapical film projection, and comprises a data acquisition module, a model construction module and a parameter measurement module. The data acquisition module is used to collect dental three-dimensional image data of a patient and send the dental three-dimensional image data to the model construction module; the model construction module is used to convert the three-dimensional image data into a dental three-dimensional model and establish a digital image plate model and a digital X-center line model in the dental three-dimensional model; the parameter measurement module is used to align, move and adjust the dental three-dimensional model, and calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface based on the positional relationship between the digital image plate model, the digital X-center line model and the dental three-dimensional model.

[0035] In order to better implement the present invention, further, the parameter measurement module includes a registration module, and the registration module registers the crown part in the dental three-dimensional model based on the clinical crown optimal registration model.

[0036] In order to better implement the present invention, further, the parameter measurement module includes an object movement module, and the object movement module is used to move and adjust the relative positions among the dental three-dimensional model, the digital imaging plate model, and the digital X-ray centerline model.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] The present invention constructs a dental 3D model of the patient based on the patient's dental 3D imaging data, simulates the scene of the patient taking periapical films under actual conditions based on the dental 3D model, and accurately measures the optimal positioning parameters of the X-ray tube when projecting periapical films of different tooth positions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the steps of the method according to the present invention;

[0040] Figure 2 is a schematic diagram of the characteristic plane A of the image plate;

[0041] Figure 3 It is a schematic diagram of the tooth long axis plane B;

[0042] Figure 4 is a schematic diagram of the angle bisector plane C;

[0043] Figure 5 is a schematic diagram of a first reference plane D;

[0044] Figure 6 is a schematic diagram of the second reference plane E. DETAILED DESCRIPTION

[0045] The following detailed descriptions are all illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0046] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the present invention explicitly states otherwise, singular forms are also intended to include plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0047] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0048] Terminology explanation section: The terms "install", "connect", "connect", "fixed" and the like in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements, or an interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0049] Embodiment 1:

[0050] The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography of the present embodiment obtains dental 3D imaging data of a patient, generates a dental 3D model of the patient based on the dental 3D imaging data, performs crown registration and tooth position adjustment based on the dental 3D model; establishes a digital imaging plate model and a digital X-ray centerline model, places the digital imaging plate model according to tooth position projection requirements, establishes a feature surface based on the positional relationship between the tooth position and the digital imaging plate model, and calculates the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface through the positional relationship between the feature surface and the digital X-ray centerline model.

[0051] like Figure 1 As shown, the specific steps include:

[0052] Step 1, obtaining dental 3D image data of the patient, wherein the dental 3D image data includes 3D scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue, as well as intraoral optical scanning data of the upper and lower jaws of the dentition, gums, and mucosal tissues in the mouth;

[0053] Step 2: Generate three-dimensional surface data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue based on the three-dimensional scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue; create a digital imaging plate model and a digital X-ray centerline model;

[0054] Step 3: Using the three-dimensional surface data of the dentition as a fixed reference, floating adjustment is performed on the optical scanning data of the dentition in the mouth to achieve model registration of the crown part;

[0055] Step 4: Based on different tooth positions, the median sagittal plane of the craniomaxillofacial bone tissue is established through the three-dimensional surface data of the craniomaxillofacial bone tissue, and the median sagittal plane of the craniomaxillofacial bone tissue is made perpendicular to the horizontal plane; then the dentition position is adjusted so that the upper dentition occlusal plane is parallel to the horizontal plane or the lower dentition occlusal plane is parallel to the horizontal plane;

[0056] Step 5: Place the digital imaging plate model and the digital X-ray centerline model according to the projection requirements of different tooth positions, and establish a feature surface based on the positional relationship between the tooth position and the digital imaging plate model. Calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface through the positional relationship between the feature surface and the digital X-ray centerline model.

[0057] Embodiment 2:

[0058] The method for calculating the optimal positioning parameters of the X-ray tube during dental periapical radiography is improved on the basis of Example 1. The step 5 of calculating the inclination angle parameters of the X-ray tube specifically includes:

[0059] Step S1: Figure 2As shown, based on the contact feature fitting between the side plane of the digital image plate model close to the teeth and the teeth, an image plate feature plane A parallel to the side plane of the digital image plate model close to the teeth is obtained;

[0060] Step S2: Figure 3 As shown, feature points are selected on the teeth at the current tooth position, and the tooth long axis plane B at the current tooth position is obtained by fitting the feature points;

[0061] Step S3: Figure 4 As shown, the angle bisector plane C formed by the angle between the characteristic plane of the imaging plate and the long axis plane of the tooth is generated;

[0062] Step S4: Figure 5 As shown, based on the world coordinate system, a first reference plane D perpendicular to the Z axis of the world coordinate system is established, and a second reference plane E perpendicular to the X axis of the world coordinate system is established;

[0063] Step S5: Figure 6 As shown, the first angle between the angle bisector plane C and the first reference plane D is measured, and the second angle between the tooth long axis plane B and the second reference plane E is measured. The step 5 of solving the position parameters of the X-ray tube center aligned with the human body surface specifically includes:

[0064] Step K1, obtaining an image plate feature plane A parallel to a side plane of the digital image plate model close to the teeth based on contact feature fitting between a side plane of the digital image plate model close to the teeth and the teeth;

[0065] Step K2, selecting feature points on the teeth at the current tooth position, and obtaining the tooth long axis plane B at the current tooth position by fitting the feature points;

[0066] Step K3, generating an angle bisector plane C formed by the angle between the image plate feature plane A and the tooth long axis plane B;

[0067] Step K4, based on the world coordinate system, establish a first reference plane D perpendicular to the Z axis of the world coordinate system, and establish a second reference plane E perpendicular to the X axis of the world coordinate system;

[0068] Step K5, moving the X-ray centerline model so that the axis of the X-ray centerline model is perpendicular to the angle bisector plane C and passes through the middle of the root of the tooth being projected; extracting the focus where the axis of the X-ray centerline model intersects with the facial soft tissue;

[0069] Step K6, using the nose wing point, inner canthus point, and outer canthus point in the three-dimensional surface data of the facial soft tissue as reference points, measuring the horizontal distance and vertical distance between the focus and each reference point, and solving the position parameters of the X-ray tube center aligned with the human body surface based on the horizontal distance and vertical distance. Angle; calculate the vertical inclination angle of the X-ray centerline model based on the first angle, and calculate the horizontal inclination angle of the X-ray centerline model based on the second angle.

[0070] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0071] Embodiment 3:

[0072] The method for calculating the optimal positioning parameters of the X-ray tube during dental periapical radiography is improved on the basis of Embodiment 1 or 2, wherein the step 5 of placing the digital imaging plate model according to the projection requirements of different tooth positions specifically includes:

[0073] Step T1, placing the digital imaging plate model close to the lingual side or palatal side of the tooth to be imaged;

[0074] Step T2: When projecting the front teeth, place the digital imaging plate model vertically so that the edge of the digital imaging plate model is 5-7 mm higher than the incisal edge of the projected teeth;

[0075] Step T3: When projecting the posterior teeth, place the digital imaging plate model horizontally so that the edge of the digital imaging plate model is 10-12 mm higher than the occlusal surface of the projected teeth.

[0076] Furthermore, in step 3, the root mean square distance of the morphological difference between the partial registration model of the crown and the clinical optimal registration model of the crown is calculated so that the root mean square distance is less than or equal to 0.5 mm.

[0077] The other parts of this embodiment are the same as those of Embodiment 1 or 2, and thus will not be described in detail.

[0078] Embodiment 4:

[0079] A system for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography is used to implement the method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography as described in any one of Examples 1-3, comprising a data acquisition module, a model construction module, and a parameter measurement module, wherein the data acquisition module is used to collect dental three-dimensional image data of a patient and send the dental three-dimensional image data to the model construction module; the model construction module is used to convert the three-dimensional image data into a dental three-dimensional model, and establish a digital image plate model and a digital X-centerline model in the dental three-dimensional model; the parameter measurement module is used to align, move and adjust the dental three-dimensional model, and calculate the inclination angle parameters of the X-ray tube and the position parameters of the center of the X-ray tube aligned with the human body surface based on the positional relationship between the digital image plate model, the digital X-centerline model, and the dental three-dimensional model.

[0080] Furthermore, the parameter measurement module includes a registration module, and the registration module registers the crown part in the dental three-dimensional model based on the clinical crown optimal registration model.

[0081] Furthermore, the parameter measurement module includes an object movement module, and the object movement module is used to move and adjust the relative positions among the dental three-dimensional model, the digital imaging plate model, and the digital X-ray centerline model.

[0082] The other parts of this embodiment are the same as any one of Embodiments 1-3, so they are not described again.

[0083] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography, characterized in that: Acquire the patient's dental 3D imaging data, generate the patient's dental 3D model based on the dental 3D imaging data, perform crown alignment and tooth position adjustment based on the dental 3D model; establish a digital imaging plate model and a digital X-ray centerline model, place the digital imaging plate model according to the tooth position projection requirements, establish a feature surface based on the positional relationship between the tooth position and the digital imaging plate model, and calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface through the positional relationship between the feature surface and the digital X-ray centerline model.

2. The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to claim 1, characterized in that: The specific steps include: Step 1, obtaining dental 3D image data of the patient, wherein the dental 3D image data includes 3D scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue, as well as intraoral optical scanning data of the upper and lower jaws of the dentition, gums, and mucosal tissues in the mouth; Step 2: Generate three-dimensional surface data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue based on the three-dimensional scanning data of the patient's dentition, craniomaxillofacial bone tissue, and facial soft tissue; create a digital imaging plate model and a digital X-ray centerline model; Step 3: Using the three-dimensional surface data of the dentition as a fixed reference, floating adjustment is performed on the optical scanning data of the dentition in the mouth to achieve model registration of the crown part; Step 4: Based on different tooth positions, the median sagittal plane of the craniomaxillofacial bone tissue is established through the three-dimensional surface data of the craniomaxillofacial bone tissue, and the median sagittal plane of the craniomaxillofacial bone tissue is made perpendicular to the horizontal plane; then the dentition position is adjusted so that the upper dentition occlusal plane is parallel to the horizontal plane or the lower dentition occlusal plane is parallel to the horizontal plane; Step 5: Place the digital imaging plate model and the digital X-ray centerline model according to the projection requirements of different tooth positions, and establish a feature surface based on the positional relationship between the tooth position and the digital imaging plate model. Calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface through the positional relationship between the feature surface and the digital X-ray centerline model.

3. The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to claim 2, characterized in that: The step 5 of calculating the inclination angle parameter of the X-ray tube specifically includes: Step S1, obtaining an image plate feature plane A parallel to a side plane of the digital image plate model close to the teeth based on contact characteristics fitting between a side plane of the digital image plate model close to the teeth and the teeth; Step S2, selecting feature points on the teeth at the current tooth position, and obtaining the tooth long axis plane B at the current tooth position by fitting the feature points; Step S3, generating an angle bisector plane C formed by an angle between the characteristic plane of the image plate and the long axis plane of the tooth; Step S4, based on the world coordinate system, establish a first reference plane D perpendicular to the Z axis of the world coordinate system, and establish a second reference plane E perpendicular to the X axis of the world coordinate system; Step S5, measuring the first angle between the angle bisector plane C and the first reference plane D, and measuring the second angle between the tooth long axis plane B and the second reference plane E; calculating the vertical inclination angle of the X-centerline model based on the first angle, and calculating the horizontal inclination angle of the X-centerline model based on the second angle.

4. The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to claim 3, characterized in that: The step 5 of calculating the position parameters of the X-ray tube center aligned with the human body surface specifically includes: Step K1, obtaining an image plate feature plane A parallel to a side plane of the digital image plate model close to the teeth based on contact feature fitting between a side plane of the digital image plate model close to the teeth and the teeth; Step K2, selecting feature points on the teeth at the current tooth position, and obtaining the tooth long axis plane B at the current tooth position by fitting the feature points; Step K3, generating an angle bisector plane C formed by the angle between the feature plane of the image plate and the long axis plane of the tooth; Step K4, based on the world coordinate system, establish a first reference plane D perpendicular to the Z axis of the world coordinate system, and establish a second reference plane E perpendicular to the X axis of the world coordinate system; Step K5, moving the X-ray centerline model so that the axis of the X-ray centerline model is perpendicular to the angle bisector plane C and passes through the middle of the root of the tooth being projected; extracting the focus where the axis of the X-ray centerline model intersects with the facial soft tissue; Step K6, using the points beside the nose wings, inner canthus points, and outer canthus points in the three-dimensional surface data of the facial soft tissue as reference points, measure the horizontal distance and vertical distance between the focus and each reference point, and calculate the position parameters of the X-ray tube center aligned with the human body surface based on the horizontal distance and the vertical distance.

5. The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to claim 4, characterized in that: Placing the digital imaging plate model according to the projection requirements of different tooth positions in step 5 specifically includes: Step T1, placing the digital imaging plate model close to the lingual side or palatal side of the tooth to be imaged; Step T2: When projecting the front teeth, place the digital imaging plate model vertically so that the edge of the digital imaging plate model is 5-7 mm higher than the incisal edge of the projected teeth; Step T3: When projecting the posterior teeth, place the digital imaging plate model horizontally so that the edge of the digital imaging plate model is 10-12 mm higher than the occlusal surface of the projected teeth.

6. The method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to claim 5, characterized in that: In step 3, the root mean square distance of the morphological difference between the partial registration model of the crown and the clinical optimal registration model of the crown is calculated so that the root mean square distance is less than or equal to 0.5 mm.

7. A system for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography, which is used to implement the method for calculating the optimal positioning parameters of an X-ray tube during dental periapical radiography according to any one of claims 1 to 6, characterized in that: The invention comprises a data acquisition module, a model construction module and a parameter measurement module. The data acquisition module is used to acquire dental three-dimensional image data of the patient and send the dental three-dimensional image data to the model construction module; the model construction module is used to convert the three-dimensional image data into a dental three-dimensional model and establish a digital image plate model and a digital X-ray centerline model in the dental three-dimensional model; the parameter measurement module is used to align, move and adjust the dental three-dimensional model, and calculate the inclination angle parameters of the X-ray tube and the position parameters of the X-ray tube center aligned with the human body surface based on the positional relationship among the digital image plate model, the digital X-ray centerline model and the dental three-dimensional model.

8. The system for calculating the optimal positioning parameters of an X-ray tube when obtaining dental periapical radiographs according to claim 7, characterized in that: The parameter measurement module comprises a registration module, and the registration module registers the crown part in the dental three-dimensional model based on the clinical crown optimal registration model.

9. The system for calculating the optimal positioning parameters of an X-ray tube when obtaining dental periapical radiographs according to claim 7, characterized in that: The parameter measurement module includes an object movement module, and the object movement module is used to move and adjust the relative positions among the dental three-dimensional model, the digital imaging plate model, and the digital X-centerline model.

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