Positioning method for assisting temporomandibular joint cone beam CT scanning through body surface marks

Abstract

The invention provides a body surface mark assisted temporomandibular joint cone beam CT scanning positioning method. The method comprises the following steps: acquiring temporomandibular joint large-view cone beam CT image data of a plurality of testees; based on the CT image data, performing three-dimensional reconstruction and head position correction to obtain head projection views corresponding to a plurality of testees; based on body surface mark points and temporal-mandibular joint bone mark points in a plurality of head projection views, the moving distance of a positioning line of large-view or small-view cone-beam CT scanning relative to the body surface mark points in a corresponding coordinate axis is obtained through statistics, and cone-beam CT scanning is positioned based on the moving distance. And positioning the positioning line of the large-view or small-view cone beam CT scanning to the corresponding optimal position. The problems that in the prior art, due to the fact that an accurate and rapid positioning mode is lacked during cone beam CT scanning positioning, shooting time is long, working efficiency is low, and the shooting failure probability caused by double artifacts due to movement of a patient is increased are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of medical devices, and in particular relates to a positioning method for cone beam CT scanning of a temporomandibular joint assisted by body surface landmarks. Background Art

[0002] Temporomandibular disorders (TMD) refer to a group of diseases that involve the temporomandibular joint (TMJ) and / or the masticatory muscles and have some common related clinical problems (such as pain, clicking, limited mouth opening, etc.). TMD is a common and frequently occurring disease in stomatology, and is the fourth most common oral disease after caries, periodontal disease, etc. TMD can occur at any age, with the highest visit rate among young and middle-aged people. Medical imaging examinations are of great value in the diagnosis and differential diagnosis of TMD. Among them, cone beam CT can clearly display the bone structure of the temporomandibular joint. Currently, it is the preferred method for examining the bone structure of the temporomandibular joint and has been widely used in the clinical examination of TMD.

[0003] The selection of the field of view (FOV) of cone beam CT scanning of the temporomandibular joint depends on different brands and models. A large-field cone beam CT can be used to scan bilateral TMJs, with one-time imaging, short scanning time, and convenient bilateral comparison and observation of the image; a small-field cone beam CT can also be used to project the left and right sides separately, with clearer images. However, the smaller the cone beam CT irradiation field, the greater the risk that the area of ​​interest falls outside the acquisition area, so the operator who shoots the cone beam CT has higher positioning accuracy requirements. At present, the method of using the exploration view to locate the temporomandibular joint before the formal shooting is usually used in clinical practice, but this method increases the shooting time, which not only reduces the work efficiency, but also increases the probability of double artifacts caused by patient movement, resulting in shooting failure. Technicians with rich experience in shooting often skip the exploration view step and refer to the temporomandibular joint tomography fixed-point method to roughly locate the temporomandibular joint. However, this method relies on the operator's experience and the positioning effect cannot be guaranteed. Moreover, for models that cannot skip the exploration view, if body surface landmarks are not used to assist in positioning before shooting, the cone beam CT machine scanning bed or scanning chair will need to be moved significantly due to inaccurate initial positioning. Therefore, there is an urgent need for an accurate scanning positioning method to accurately position the temporomandibular joint before performing cone beam CT scanning. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a positioning method for cone beam CT scanning of the temporomandibular joint with the assistance of body surface landmarks, so as to solve the problem that the existing technology lacks a quick and accurate positioning method when positioning cone beam CT scanning, resulting in a long shooting time, which not only reduces work efficiency, but also causes double artifacts due to patient movement, thereby increasing the probability of shooting failure.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] In one aspect, the present invention provides a method for positioning a temporomandibular joint using body surface landmarks in cone beam CT scanning, the method comprising:

[0007] Acquire the wide-field cone-beam CT imaging data of the temporomandibular joint of multiple subjects;

[0008] Perform three-dimensional reconstruction and head position correction based on the CT image data to obtain a plurality of head projection views corresponding to the subjects;

[0009] Based on the body surface landmarks and the bony landmarks of the temporomandibular joint in the head projection view, obtaining the distance between the optimal position of the three-axis positioning line of the small-field cone beam CT and the body surface landmarks or the bony landmarks of the temporomandibular joint in the corresponding axial direction;

[0010] Based on the mean and standard deviation of the distances corresponding to multiple subjects, the moving distance of the positioning line of the large field of view or small field of view cone beam CT scan relative to the body surface landmark point in the corresponding coordinate axis is obtained, and the moving distance is used to position the cone beam CT scan, and the positioning line of the large field of view or small field of view cone beam CT scan is positioned to the corresponding optimal position.

[0011] Furthermore, the three-axis positioning line includes an X-axis laser positioning line in front view and Y-axis and Z-axis laser positioning lines in side view;

[0012] The distance between the optimal position of the three-axis positioning line of the small-field cone-beam CT and the body surface landmark point or the temporomandibular joint bony landmark point of the corresponding axis includes:

[0013] The distance between the optimal position of the X-axis laser positioning line in the front view and the first body surface landmark is used to determine the moving distance between the X-axis laser positioning line in the front view of the small field of view cone beam CT and the first body surface landmark;

[0014] The distance between the best position of the Y-axis laser positioning line in the lateral view and the two upper and lower bony landmarks in the Y-axis direction of the temporomandibular joint is used to determine the moving distance between the Y-axis laser positioning line in the lateral view of the cone beam CT with a large or small field of view and the second body surface landmark;

[0015] The distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark is used to determine the moving distance between the Z-axis laser positioning line in the lateral view of a large or small field of view cone beam CT and the second body surface landmark.

[0016] The first body surface landmark is the outer canthus of the eye, and the second body surface landmark is the most convex point of the posterior edge of the tragus;

[0017] The two upper and lower bony landmarks of the temporomandibular joint in the Y-axis direction include the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch.

[0018] Furthermore, the optimal position of the positioning line of the small field of view cone beam CT scanning includes: the optimal position of the X-axis laser positioning line in the front view is a vertical line passing through the center point of the condyle in the X-axis direction; the optimal position of the Y-axis laser positioning line in the lateral view is a horizontal line passing through the most convex point of the posterior edge of the tragus; the optimal position of the Z-axis laser positioning line in the lateral view is a vertical line passing through the center point of the condyle in the Z-axis direction;

[0019] The optimal positions of the positioning lines for cone-beam CT scanning with a large field of view include: the optimal position of the X-axis laser positioning line in the frontal view is the midline of the face; the optimal positions of the Y-axis and Z-axis laser positioning lines in the lateral view are the same as the corresponding optimal positions of the laser positioning lines in cone-beam CT with a small field of view.

[0020] Furthermore, the distance between the optimal position of the frontal view X-axis laser positioning line and the first body surface landmark is measured by the following method:

[0021] The projection point of the lateral canthus of the eye on the same side of the measured condyle on the anteroposterior projection view of the skull is defined as the E-lat point; the outermost point and the innermost point in the X-axis direction of the condyle are defined as the C-lat point and the C-med point respectively; the projection point of the C-med point on the horizontal line passing through the C-lat point is defined as C-med';

[0022] Draw a vertical line a perpendicular to the horizontal line through the midpoint M of the C-med' point and the C-lat point. The vertical line a is the optimal position of the X-axis laser positioning line of the small field of view cone beam CT.

[0023] The distance between point E-lat and vertical line a is the distance between the outer canthus of the eye on the X-axis and the optimal position of the X-axis laser positioning line, expressed as d x .

[0024] Furthermore, the distance between the best position of the Y-axis laser positioning line in the lateral view and the bony landmark of the temporomandibular joint includes: the vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the uppermost point of the temporomandibular joint fossa, expressed as d y1 The vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the lowest point of the temporomandibular sigmoid notch is expressed as d y2 ;

[0025] The distance d y1 and d y2 Obtained by the following method:

[0026] On the lateral head projection view, the projection point of the most convex point of the posterior edge of the tragus on the same side of the measured condyle on the lateral head view is defined as the T point, the uppermost point of the temporomandibular joint fossa is defined as the RG point, and the lowermost point of the temporomandibular sigmoid notch is defined as the Sn point;

[0027] Draw a straight line b through point T parallel to the horizontal reference plane, and the straight line b is the optimal position of the Y-axis laser positioning line in the cone beam CT lateral view; the distance between point RG and straight line b is the distance d y1 ;

[0028] The distance between point Sn and straight line b is the distance d y2 .

[0029] Furthermore, the distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark point is measured by the following method:

[0030] The projection points of the most anterior and most posterior points of the condyle in the Z-axis direction on the lateral head projection view are defined as C-ant point and C-pos point respectively;

[0031] Draw perpendicular lines l through points C-ant and C-pos respectively and perpendicular to the horizontal reference plane C-ant and l C-pos ;

[0032] Take the equal part C-ant and l C-pos The vertical line of the distance between them is l, and the vertical line l is the best position of the Z-axis laser positioning line when shooting cone beam CT of the temporomandibular joint;

[0033] The distance between the most convex point T on the posterior edge of the tragus on the same side and the vertical line l is the distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark point, expressed as d z .

[0034] Furthermore, the moving distance of the positioning line of the small field of view cone beam CT scan relative to the body surface landmark point in the corresponding coordinate axis includes:

[0035] The X-axis laser positioning line in the frontal view takes the outer canthus of the eye as the body surface landmark and moves along the X-axis toward the outside of the eye. is the distance d corresponding to multiple subjects x The average value of

[0036] The Y-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark and coincides with the most convex point of the posterior edge of the tragus;

[0037] The Z-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark, and moves along the Z-axis direction toward the front of the nose. is the distance d corresponding to multiple subjects z The average value of .

[0038] Furthermore, when the large-field cone-beam CT is scanned, the X-axis laser positioning line in the front view is set at the midline of the face, and the moving distance of the Y-axis and Z-axis laser positioning lines in the side view relative to the body surface landmarks in the corresponding coordinate axes is the same as the moving distance of the small-field cone-beam CT.

[0039] Furthermore, the moving distance between the X-axis laser positioning line and the first body surface landmark in the front view of the small field of view cone beam CT is 8.59 mm, the moving distance between the Z-axis laser positioning line and the second body surface landmark in the lateral view of cone-beam CT with a large or small field of view It is 11.73mm.

[0040] Furthermore, based on the three-dimensional reconstructed view of the head, the anatomical landmark method is used to perform head position correction, including:

[0041] The orbito-auricular plane is established with the midpoint between the bilateral infraorbital points and the upper points of the bilateral bony external auditory canals. The orbito-auricular plane is a horizontal reference plane parallel to the ground plane. The median sagittal plane perpendicular to the horizontal plane and the coronal plane perpendicular to both the horizontal reference plane and the median sagittal plane are established to complete the head position correction.

[0042] Beneficial effects of this technical solution:

[0043] The present invention is based on a large amount of cone-beam CT three-dimensional reconstructed image data, accurately measures and analyzes the quantitative relationship between the tragus, outer canthus and other body surface landmarks and the bony key points of the temporomandibular joint in three-dimensional spatial position, determines the optimal positioning position of the temporomandibular joint during cone-beam CT scanning, and achieves more convenient and accurate positioning of the temporomandibular joint during cone-beam CT examination, opens up a new direction for the positioning of cone-beam CT scanning of the temporomandibular joint, and improves the efficiency and accuracy of cone-beam CT scanning positioning.

[0044] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0046] Figure 1 It is a flow chart of a method for positioning the temporomandibular joint using cone beam CT scanning assisted by body surface landmarks according to an embodiment of the present invention;

[0047] Figure 22 is a schematic diagram of measuring the position of the X-axis laser positioning line of the cone beam CT front view of the right temporomandibular joint according to an embodiment of the present invention;

[0048] Figure 3 2 is a schematic diagram of measuring the position of the Y-axis laser positioning line of the cone beam CT lateral view of the right temporomandibular joint according to an embodiment of the present invention;

[0049] Figure 4 It is a schematic diagram of measuring the position of the Z-axis laser positioning line of the cone beam CT lateral view of the right temporomandibular joint according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the implementation cases of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0051] One embodiment of the present invention provides a method for positioning the temporomandibular joint using cone beam CT scanning assisted by body surface landmarks, such as Figure 1 As shown, the method comprises the following steps:

[0052] Step S1: Acquire wide-field cone-beam CT image data of the temporomandibular joint of multiple subjects;

[0053] Specifically, the temporomandibular joint is composed of the mandibular condyle, the articular surface of the temporal bone (including the fossa and articular tubercle), the articular disc, the joint capsule and the articular ligament. Cone-beam CT is mainly used to observe the bony structure and joint space of the temporomandibular joint. The shooting range needs to reach the top of the fossa and the plane of the mandibular sigmoid notch. There are many types of cone-beam CT machines currently used in clinical practice. The scanning field of view (FOV) of different models is different. Even the same model has different scanning fields of view to choose from. The FOV of cone-beam CT is mostly cylindrical, expressed as cylinder diameter × height (cm). Due to the cone-beam effect, images near the edge of the scanning field of view are prone to deformation, streak artifacts and noise. Placing the target region of interest in the center of the FOV can reduce the impact of the cone-beam effect on image quality. The spatial resolution of cone-beam CT is position-dependent. The spatial resolution of the middle area of ​​the field of view and the rotation center (i.e., the center of the FOV) is high. Therefore, when positioning the cone-beam CT, the region of interest should be placed in the center of the FOV as much as possible. In order to achieve the above-mentioned purpose, the present embodiment collects wide-field cone-beam CT image data of the temporomandibular joint of multiple subjects for statistical analysis of the distances between the key points of the temporomandibular joint and the selected surface landmarks, so as to realize rapid and accurate positioning of the cone-beam CT scan of the temporomandibular joint based on the surface landmarks.

[0054] Preferably, this embodiment uses a large-field cone-beam CT image data taken at the initial visit of multiple oral patients, and selects the image data of multiple patients who meet the inclusion criteria for the positioning analysis of the cone-beam CT scan of the temporomandibular joint; wherein, the scanning device uses the Newtom 5G (QR Srl, Verona Italy) horizontal cone-beam CT for scanning. During the scan, the patient lies in a supine position, the midsagittal plane of the face is perpendicular to the ground plane, the orbital-auricular plane is perpendicular to the ground, and the mouth is closed. The patient is asked to bite the back teeth, keep them in the intercusp position, and keep still during the scan. The scanning parameters are to use the Regular scan standard dose mode scan, the voltage is 110KV, the current is automatically adjusted by the equipment after the exploration view is collected, the exposure time is 4.8s, and the scanning field of view is 18cm×16cm. The inclusion criteria for imaging data include: the image is clear and can fully display the bilateral temporomandibular joints, tragus and lateral canthus; the bilateral maxillofacial appearance is basically symmetrical; there is no history of orthognathic treatment and maxillofacial trauma; there is no obvious organic lesions such as TMJ tumors and TMJ ankylosis, etc., so as to reduce the impact of special data on the stability of positioning position.

[0055] Step S2: performing three-dimensional reconstruction and head position correction based on the CT image data to obtain a plurality of head projection views corresponding to the subjects;

[0056] Specifically, the original CT image data obtained by scanning is reconstructed by Newtom's own NNT Viewer software and exported as a ".dicom" format file, and the reconstructed voxel is set to 0.3mm. The ".dicom" format image is imported into a third-party software, such as Mimics Medical, to perform head position correction and establish a three-dimensional coordinate system for subsequent measurements. Among them, the head position correction adopts the anatomical landmark point method, and the orbito-auricular plane is established with the midpoint between the bilateral infraorbital points and the bilateral bony external auditory canal upper points. The orbito-auricular plane is a horizontal reference plane parallel to the ground plane; a median sagittal plane perpendicular to the horizontal plane and a coronal plane perpendicular to both the horizontal reference plane and the median sagittal plane are established to complete the head position correction and obtain a head projection view after the head position correction.

[0057] Step S3: based on the body surface landmarks and the bony landmarks of the temporomandibular joint in the head projection view, obtaining the distance between the optimal position of the three-axis positioning line of the small-field cone beam CT and the body surface landmarks or the bony landmarks of the temporomandibular joint in the corresponding axis;

[0058] Specifically, the three-axis positioning line includes the front view X-axis laser positioning line and the lateral view Y-axis and Z-axis laser positioning lines; the distance between the optimal position of the three-axis positioning line of the small field of view cone beam CT for analysis and the corresponding axial surface landmark point or the temporomandibular joint bone landmark point measured in this embodiment includes:

[0059] The distance between the optimal position of the X-axis laser positioning line in the frontal view and the first body surface landmark (i.e., the outer canthus of the eye) is used to determine the moving distance between the X-axis laser positioning line in the frontal view of small field of view cone beam CT and the outer canthus of the eye;

[0060] The distance between the best position of the Y-axis laser positioning line in the lateral view and the two upper and lower bony landmarks in the Y-axis direction of the temporomandibular joint (including the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch) is used to determine the moving distance between the Y-axis laser positioning line in the lateral view of cone beam CT with a large or small field of view and the second body surface landmark (i.e., the most convex point of the posterior edge of the tragus);

[0061] The distance between the optimal position of the Z-axis laser positioning line in the plan view and the most convex point of the posterior edge of the tragus is used to determine the moving distance between the Z-axis laser positioning line in the lateral view of the large or small field of view cone beam CT used in CT scanning.

[0062] Furthermore, in order to make the measured temporomandibular joint as close as possible to the center of the cone beam CT shooting field, the optimal position of the positioning line of the small field of view cone beam CT scanning is set as follows: the optimal position of the X-axis laser positioning line in the front view is the vertical line passing through the center point of the condyle in the X-axis direction; the optimal position of the Y-axis laser positioning line in the lateral view is the horizontal line passing through the most convex point of the posterior edge of the tragus; the optimal position of the Z-axis laser positioning line in the lateral view is the vertical line passing through the center point of the condyle in the Z-axis direction; the optimal positions of the positioning lines of the large field of view cone beam CT scanning include: the optimal position of the X-axis laser positioning line in the front view is the midline of the face; the optimal positions of the Y-axis and Z-axis laser positioning lines in the lateral view are the same as the optimal positions of the corresponding laser positioning lines of the small field of view cone beam CT.

[0063] More specifically, Figure 2 As shown, the distance between the optimal position of the X-axis laser positioning line in the front view and the first body surface landmark point (expressed as d x ) is measured by the following method:

[0064] The projection point of the lateral canthus of the eye on the same side of the measured condyle on the anteroposterior projection view of the skull is defined as the E-lat point; the outermost point and the innermost point in the X-axis direction of the condyle are defined as the C-lat point and the C-med point respectively; the projection point of the C-med point on the horizontal line passing through the C-lat point is defined as C-med';

[0065] Draw a vertical line a perpendicular to the horizontal line through the midpoint M of the C-med' point and the C-lat point. The vertical line a is the optimal position of the X-axis laser positioning line of the small field of view cone beam CT.

[0066] The distance between point E-lat and vertical line a is the distance d between the outer canthus of the eye on the X-axis and the optimal position of the X-axis laser positioning line. x .

[0067] Further, such as Figure 3 As shown in the figure, the distance between the best position of the Y-axis laser positioning line in the lateral view and the bony landmark of the temporomandibular joint includes: the vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the uppermost point of the temporomandibular joint fossa, expressed as d y1 The vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the lowest point of the temporomandibular sigmoid notch is expressed as d y2 ; where the distance d y1 and d y2 Obtained by the following method:

[0068] On the lateral head projection view, the projection point of the most convex point of the posterior edge of the tragus on the same side of the measured condyle on the lateral head view is defined as the T point, the uppermost point of the temporomandibular joint fossa is defined as the RG point, and the lowermost point of the temporomandibular sigmoid notch is defined as the Sn point;

[0069] Draw a straight line b through point T parallel to the horizontal reference plane, and the straight line b is the optimal position of the Y-axis laser positioning line in the cone beam CT lateral view; the distance between point RG and straight line b is the distance d y1 ; The distance between point Sn and straight line b is the distance d y2 .

[0070] It should be noted that, in this embodiment, the optimal position of the Y-axis laser positioning line in the lateral view is initially set to a straight line passing through the most convex point of the posterior edge of the tragus, a body surface landmark. In order to verify the feasibility of the optimal position, the distances from the optimal position positioning line to the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch of a large number of subjects are collected, and statistical analysis is performed to verify the positioning of the Y-axis laser positioning line at the optimal position. When performing a CT scan, whether the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch in the Y-axis direction can be well included in the scanning field of view, if so, the initially set optimal position positioning line is used as the final optimal position; if the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch cannot be included in the scanning field of view, the moving distance of the initially set optimal position positioning line relative to the most convex point of the posterior edge of the tragus can be found through data analysis to locate the Y-axis laser positioning line at the optimal position to ensure the accuracy of the positioning.

[0071] Further, if Figure 4 As shown, the distance between the optimal position of the Z-axis laser positioning line in the side view and the second body surface landmark point (expressed as d z ) is measured by the following method:

[0072] The projection points of the most anterior and most posterior points of the condyle in the Z-axis direction on the lateral head projection view are defined as C-ant point and C-pos point respectively;

[0073] Draw perpendicular lines l through points C-ant and C-pos respectively and perpendicular to the horizontal reference plane C-ant and l C-pos ;

[0074] Take equal parts C-ant and l C-pos The vertical line of the distance between them is l, and the vertical line l is the best position of the Z-axis laser positioning line when shooting cone beam CT of the temporomandibular joint;

[0075] The distance between the most convex point T on the posterior edge of the tragus on the same side and the vertical line l is the distance d between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark point. z .

[0076] In actual application, the corresponding distances between the most convex points of the lateral canthus and the posterior edge of the tragus and the selected relevant bony landmarks of the temporomandibular joint are measured on the frontal and lateral projection views of the head respectively. The patients are numbered according to the measurement order, and all quantitative measurements are completed by the same attending physician to ensure the stability of the measurement data.

[0077] It should be noted that the temporomandibular joint is located deep, that is, the key points of the temporomandibular joint are not visible on the body surface, so surface landmarks are needed for auxiliary positioning. The selection of surface landmarks should be easy to identify and relatively stable; the most convex points of the outer canthus of the eye and the posterior edge of the tragus are easy to identify and are landmarks used in clinical practice. When using laser positioning lines for positioning, most cone beam CT machines have three laser positioning lines for the X-axis, Y-axis and Z-axis; for frontal view scanning, there is a vertical line indicating the center of the cylindrical scanning field of view, which is the X-axis laser positioning line. When using a small field of view cone beam CT to shoot unilateral temporomandibular joint positioning, ideally, the laser positioning line should just coincide with the vertical line passing through the center point of the condyle in the X-axis direction of the frontal view. Therefore, in this embodiment, when viewed from the front, the vertical distance from the outer canthus of the body surface landmark to the line on the frontal projection view is measured to guide the clinical positioning of the small field of view cone beam CT for frontal view; when scanning with a large field of view cone beam CT, the frontal view only needs to place the laser positioning line at the midline of the face. For the lateral view scan, two positioning laser lines can be seen, one is the midline indicating the upper and lower positions, which is the Y-axis laser positioning line. Taking the FOV of 6cm×6cm as an example, the field of view height is 6cm, and the upper and lower horizontal laser positioning lines can each include 3cm high target tissues. This embodiment measures the vertical distances from the most convex point of the posterior edge of the tragus to the horizontal lines where the apex of the fossa and the lowest point of the sigmoid notch are located to guide the adjustment of the upper and lower positions (Y-axis direction); the other is the vertical line indicating the center of the cylindrical scanning field of view in the lateral view, which is the Z-axis laser positioning line. When positioning, whether shooting the temporomandibular joint with a large field of view or a small field of view cone beam CT, ideally the positioning line should coincide with the vertical line passed by the center point of the condyle in the lateral view. Therefore, this embodiment measures the distance from the midpoint of the posterior edge of the tragus, a body surface landmark point, to the vertical line where the center point of the condyle is located to guide the clinical positioning in the Z-axis direction of the lateral view.

[0078] Step S4: Based on the mean and standard deviation of the distances corresponding to multiple subjects, the moving distance of the positioning line of the large field of view or small field of view cone beam CT scan relative to the body surface landmark point in the corresponding coordinate axis is obtained, and the moving distance is used to position the cone beam CT scan, and the positioning line of the large field of view or small field of view cone beam CT scan is positioned to the corresponding optimal position.

[0079] In order to improve the generalization ability of the positioning method of the present invention, when acquiring cone beam CT image data, data of different subjects of different ages, genders, etc. who may have different bone structures of the temporomandibular joints are selected; the measurement results corresponding to the body surface landmarks are shown in Table 1:

[0080] Table 1 Statistical results of quantitative measurement data of body surface landmarks and corresponding temporomandibular joints (mm, )

[0081]

[0082] Based on Table 1, we can see that Represents the statistical results, is the mean value of the measurement results, s is the standard deviation, and d is the measurement results of 224 temporomandibular joints of 112 patients. x The mean and standard deviation were (8.59±3.13) mm, ranging from 0.15 to 17.10 mm, d y1 The mean and standard deviation were (14.80±3.90) mm, ranging from 5.25 to 25.50 mm, d y2 The mean and standard deviation were (6.82±3.95) mm, ranging from 0.00 to 21.75 mm, d z The mean and standard deviation were (11.73±3.16) mm, ranging from 1.80 to 20.25 mm.

[0083] According to the statistical results in Table 1, for small field of view cone beam CT scanning, the X-axis laser positioning line in the frontal view is located at the outer canthus of the eye as the body surface landmark point and moves 8.59 mm (d x The Y-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark and coincides with the most convex point of the posterior edge of the tragus; the Z-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark and moves 11.73 (d z The three-axis positioning line of the small field of view cone beam CT can be positioned to the optimal scanning position by using the average value of the three-axis positioning line of the small field of view cone beam CT.

[0084] For large-field cone-beam CT scanning, the frontal view X-axis laser positioning line is set at the midline of the face, and the side view Y-axis and Z-axis laser positioning lines move relative to the body surface landmarks in the corresponding coordinate axes the same distance as the small-field cone-beam CT.

[0085] In particular, in order to analyze the impact of data of different ages, different genders, and different sides of the temporomandibular joint on CT scanning positioning, this embodiment groups the collected data as follows: the bilateral temporomandibular joints are divided into a left group (112 patients, 112 TMJs) and a right group (112 patients, 112 TMJs) according to the side. According to gender, the patients are divided into a male group (35 cases, 70 TMJs) and a female group (77 cases, 154 TMJs). According to age grouping, 12 to 18 years old are the adolescent group (33 cases, 66 TMJs), and those over 18 years old are the adult group (79 cases, 158 TMJs), and the grouped data are statistically analyzed separately.

[0086] Specifically, the statistical data of the measurement values ​​of different sides are shown in Table 2:

[0087] Table 2 Differences between the left and right body surface landmarks and the quantitative measurement data of the temporomandibular joint on the corresponding side (mm, )

[0088]

[0089] As can be seen from Table 2, the reliability p-value results of each data are all greater than 0.05, and the measurement values ​​d x d y1 d y2 and z There was no statistically significant difference, indicating good consistency and the same data could be used for positioning.

[0090] The statistical data of the measurements for males and females are shown in Table 3:

[0091] Table 3 Analysis of the difference in quantitative relationship measurement data of the temporomandibular joint between different genders (mm, )

[0092]

[0093] From Table 3, we can see that the measured values ​​d of males and females x d y1 d y2 and z There was no statistically significant difference (P>0.05), indicating good consistency and the same data can be used for positioning.

[0094] The statistical data of the measurements for different age groups are shown in Table 4

[0095] Table 4 Difference analysis of quantitative relationship measurement data of temporomandibular joint in different age groups (mm, )

[0096]

[0097] From Table 4, we can see that the measured values ​​of the adult group d x d y2 and z were significantly greater than those of the adolescent group (P<0.05), and the positioning effect needs to be analyzed and verified separately; however, the measured values ​​d y1 There was no statistically significant difference (t=-0.09, P=0.930), and statistical analysis could be performed simultaneously.

[0098] Based on the above statistical data, it can be seen that the measurement values ​​d on the left and right sides of the subjects with no obvious facial deviation or asymmetry are x d y1 d y2 and z There was no statistically significant difference, indicating that the left-right symmetry of the selected body surface landmarks was good.

[0099] Individual measurement values ​​vary greatly between different age groups, and the positioning position needs to be analyzed and verified. Taking the smaller scanning field of view FOV of 6cm×6cm in actual application as an example, for the frontal view X-axis positioning, the measurement results in Table 4 show that the adult group d x The value is significantly greater than that of the adolescent group. When shooting temporomandibular cone beam CT, the X-axis laser positioning line should be marked with the ipsilateral canthus as the landmark point. Adults and adolescents need to move outward by about 9.07mm and 7.43mm respectively. Compared with adolescents, adults should be further away from the canthus. x The range of the condylar diameter (0.15-17.10 mm) was calculated with reference to the maximum diameter (24 mm) of the condylar inner and outer diameters (15-24 mm). x The mean value is 8.59 (see Table 1) as the moving distance. There is still a safe scanning distance of about 1 cm on the inner and outer sides of the condyle. The condyle in the area of ​​interest will not fall outside the acquisition area. Therefore, the positioning method of using the outer canthus as the surface positioning point and moving 8.59 mm outward is accurate and stable.

[0100] For the Y-axis positioning from the side view, the results of this embodiment are d y1 The mean value is 14.80 mm, the maximum value is 25.50 mm, and the d y2 The average value is 6.82mm, and the maximum value is 17.7mm. Taking the scanning field of view FOV of 6cm×6cm as an example, the horizontal laser line (i.e., the Y-axis laser line) that determines the height of the shooting field of view (i.e., it can be moved up and down) is placed on the horizontal plane passing through the most convex point of the posterior edge of the tragus. The upper and lower parts of the horizontal line are 3cm high respectively, which is enough to include the apex of the temporomandibular joint concavity and the lowest point of the sigmoid notch in the extreme case. Therefore, when the temporomandibular positioning is guided by the most convex point of the posterior edge of the tragus, the Y-axis positioning line can be placed on the horizontal plane passing through the most convex point of the posterior edge of the tragus (i.e., the aforementioned optimal position of the Y-axis laser positioning line preliminarily set). No moving distance is required, and this positioning position has good reliability.

[0101] For the Z-axis positioning of the lateral view, according to the results of this embodiment, when shooting the temporomandibular cone beam CT positioning, the laser positioning line in the anterior-posterior direction should be marked with the most convex point of the posterior edge of the tragus on the same side. Adults and adolescents need to move forward 12.07 mm and 10.92 mm respectively (see Table 4). According to the d observed in this embodiment, z The maximum value is 20.25 mm and the minimum value is 1.80 mm (see Table 1). The maximum diameter (10 mm) of the condylar Z-axis anteroposterior diameter (5-10 mm) is used for calculation. For a scanning field of view of 6 cm × 6 cm, the d value of all data is zThe mean value of 11.75 (see Table 1) is used as the moving distance. The front and back sides of the condyle have a safe scanning distance greater than 1 cm. The condyle in the area of ​​interest will not fall outside the collection area. Therefore, the most convex point of the posterior edge of the tragus is used as the surface positioning point, and the mean value of the overall data is used as the moving distance. The positioning effect is accurate and stable.

[0102] Furthermore, this embodiment also verifies the accuracy of the positioning method of the present invention by comparing two different scanning positioning methods, namely, exploration view positioning and surface landmark assisted positioning proposed in the present invention; specifically, by comparing the distance of the condylar center point deviating from the center of the field of view when shooting TMJ small field cone beam CT using exploration view positioning and using surface landmark assisted positioning, the reliability and stability of the surface landmark points obtained in this embodiment are verified. First, patients who visited the stomatology department and took cone beam CT of the temporomandibular joint were included. Without knowing the research results of the present invention, an oral imaging technician used exploration view to shoot 50 sides of the temporomandibular joint small field cone beam CT of 25 patients (aged 24 to 68 years old, 11 males and 14 females), i.e., the exploration view group. Using the scanning positioning result (accurate to mm) data obtained in this embodiment, the body surface landmark points of this embodiment were used to assist in positioning and shoot small-field cone beam CT of bilateral temporomandibular joints, namely the body surface landmark-assisted positioning group, which included 25 adolescents (9 males and 16 females) and 25 adults (10 males and 15 females), for a total of 100 temporomandibular joints.

[0103] SPSS software was used for statistical analysis. One month after the first measurement, data from 30 patients were extracted using a random number table. The same dental imaging technician re-corrected the head position, fixed the points, and measured the data. The intra-class correlation coefficient (ICC) was used to evaluate the reliability of the measurement operator. ICC < 0.40 indicated poor reliability, ICC ≥ 0.40 and < 0.75 indicated moderate reliability, and ICC ≥ 0.75 indicated good reliability. The measurement value d obtained during verification in this embodiment was x d y1 d y2 and z The ICCs were 0.86, 0.99, 0.99, and 0.99, respectively, indicating that the reliability of the measurement operator was good. The Kolmogorov-Smirnov test was used to verify the normality of the measurement data, and the results showed that the data conformed to the normal distribution. The Levene test showed that all data had equal variances, and the numerical results were expressed as " ". Paired t-test was used to compare the differences in the measurement variables of the left and right body surface positioning. Independent sample t-test was used to compare the differences in the measurement variables between men and women and between different age groups. Independent sample t-test was used to compare the difference in the distance of the condylar center point from the center of the visual field between the exploration view group and the body surface landmark auxiliary positioning group. Bilateral P<0.05 was considered statistically significant.

[0104] The validation results showed that both the exploration view positioning and the body surface landmarks assisted positioning of the TMJ small field cone beam CT can fully display the TMJ image. The distance of the condylar center point from the center of the field of view in the exploration view group [(8.84±3.79) mm] was significantly greater than that in the body surface landmarks assisted positioning group [(6.50±2.88) mm], and the eccentricity of the exploration view group was slightly greater than that of the body surface landmarks assisted positioning group (t=4.20, P=0.032). In the validation process, the positioning line was moved strictly according to the established distance based on the body surface landmarks (due to the limitation of accuracy in actual clinical applications, approximate values ​​were used in the validation), so the eccentricity of the body surface landmarks assisted positioning method was smaller in the validation results, which also showed that the body surface landmarks assisted TMJ cone beam CT scanning positioning method had better stability.

[0105] In summary, this embodiment is based on the measurement of the corresponding spatial position relationship between the outer canthus of the eye and the most convex point of the posterior edge of the tragus and the key points of the temporomandibular joint, establishes a quantitative relationship between the two, and verifies the reliability and stability of the result, providing a reference for the subsequent cone beam CT positioning of the temporomandibular joint. When using a small field of view to shoot the temporomandibular joint, the frontal view X-axis laser positioning line can be placed about 8.59mm (9.07mm for adults, 7.43mm for adolescents is better) outside the outer canthus of the eye on the same side of the temporomandibular joint, the side view Y-axis laser positioning line can be placed at the height of the most convex point of the posterior edge of the tragus, and the side view Z-axis laser positioning line is placed at about 11.73mm in front of the most convex point of the posterior edge of the tragus (12.07mm for adults, 10.92mm for adolescents is better); when using a large field of view to simultaneously project bilateral TMJs, the front view aligns the X-axis laser positioning line with the midsagittal plane of the human body, and the side view laser positioning line is the same as the small field of view laser positioning line.

[0106] The method for positioning the temporomandibular joint using cone beam CT scanning assisted by body surface landmarks provided in an embodiment of the present invention accurately measures and analyzes the quantitative relationship between body surface landmarks such as the tragus and the outer canthus and the bony key points of the temporomandibular joint in three-dimensional spatial position based on a large amount of cone beam CT three-dimensional reconstructed image data, thereby determining the optimal positioning position during cone beam CT scanning of the temporomandibular joint, achieving more convenient and accurate positioning of the temporomandibular joint during cone beam CT examination, opening up a new direction for the positioning of cone beam CT scanning of the temporomandibular joint, and improving the efficiency and accuracy of cone beam CT scanning positioning.

[0107] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0108] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for positioning the temporomandibular joint using body surface landmarks in cone beam CT scanning, characterized in that: include: Acquire the wide-field cone-beam CT imaging data of the temporomandibular joint of multiple subjects; Perform three-dimensional reconstruction and head position correction based on the CT image data to obtain a plurality of head projection views corresponding to the subjects; Based on the body surface landmarks and the bony landmarks of the temporomandibular joint in the head projection view, obtaining the distance between the optimal position of the three-axis positioning line of the small-field cone beam CT and the body surface landmarks or the bony landmarks of the temporomandibular joint in the corresponding axial direction; Based on the mean and standard deviation of the distances corresponding to multiple subjects, the moving distance of the positioning line of the large field of view or small field of view cone beam CT scan relative to the body surface landmark point in the corresponding coordinate axis is obtained, and the moving distance is used to position the cone beam CT scan, and the positioning line of the large field of view or small field of view cone beam CT scan is positioned to the corresponding optimal position.

2. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 1, characterized in that: The three-axis positioning line includes an X-axis laser positioning line in front view and Y-axis and Z-axis laser positioning lines in side view; The distance between the optimal position of the three-axis positioning line of the small-field cone-beam CT and the body surface landmark point or the temporomandibular joint bony landmark point of the corresponding axis includes: The distance between the optimal position of the X-axis laser positioning line in the front view and the first body surface landmark is used to determine the moving distance between the X-axis laser positioning line in the front view of the small field of view cone beam CT and the first body surface landmark; The distance between the best position of the Y-axis laser positioning line in the lateral view and the two upper and lower bony landmarks in the Y-axis direction of the temporomandibular joint is used to determine the moving distance between the Y-axis laser positioning line in the lateral view of the cone beam CT with a large or small field of view and the second body surface landmark; The distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark is used to determine the moving distance between the Z-axis laser positioning line in the lateral view of a large or small field of view cone beam CT and the second body surface landmark.

3. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 2, characterized in that: The first body surface landmark is the outer canthus of the eye, and the second body surface landmark is the most convex point of the posterior edge of the tragus; The two upper and lower bony landmarks of the temporomandibular joint in the Y-axis direction include the uppermost point of the temporomandibular joint fossa and the lowermost point of the temporomandibular sigmoid notch.

4. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 3, characterized in that: The best positions of the positioning lines for small field of view cone beam CT scanning include: the best position of the X-axis laser positioning line in the frontal view is the vertical line passing through the center point of the condyle in the X-axis direction; the best position of the Y-axis laser positioning line in the lateral view is the horizontal line passing through the most convex point of the posterior edge of the tragus; the best position of the Z-axis laser positioning line in the lateral view is the vertical line passing through the center point of the condyle in the Z-axis direction; The optimal positions of the positioning lines for cone-beam CT scanning with a large field of view include: the optimal position of the X-axis laser positioning line in the frontal view is the midline of the face; the optimal positions of the Y-axis and Z-axis laser positioning lines in the lateral view are the same as the corresponding optimal positions of the laser positioning lines in cone-beam CT with a small field of view.

5. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 4, characterized in that: The distance between the optimal position of the X-axis laser positioning line in the front view and the first body surface landmark point is measured by the following method: The projection point of the lateral canthus of the eye on the same side of the measured condyle on the anteroposterior projection view of the skull is defined as the E-lat point; the outermost point and the innermost point in the X-axis direction of the condyle are defined as the C-lat point and the C-med point respectively; the projection point of the C-med point on the horizontal line passing through the C-lat point is defined as C-med'; Draw a vertical line a perpendicular to the horizontal line through the midpoint M of the C-med' point and the C-lat point. The vertical line a is the optimal position of the X-axis laser positioning line of the small field of view cone beam CT. The distance between point E-lat and vertical line a is the distance between the outer canthus of the eye on the X-axis and the optimal position of the X-axis laser positioning line, expressed as d x .

6. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 5, characterized in that: The distance between the best position of the Y-axis laser positioning line in the lateral view and the bony landmark of the temporomandibular joint includes: the vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the uppermost point of the temporomandibular joint fossa, expressed as d y1 The vertical distance from the best position of the Y-axis laser positioning line in the lateral view to the lowest point of the temporomandibular sigmoid notch is expressed as d y2 ; The distance d y1 and d y2 Obtained by the following method: On the lateral head projection view, the projection point of the most convex point of the posterior edge of the tragus on the same side of the measured condyle on the lateral head view is defined as the T point, the uppermost point of the temporomandibular joint fossa is defined as the RG point, and the lowermost point of the temporomandibular sigmoid notch is defined as the Sn point; Draw a straight line b through point T parallel to the horizontal reference plane, and the straight line b is the optimal position of the Y-axis laser positioning line in the cone beam CT lateral view; the distance between point RG and straight line b is the distance d y1 ; The distance between point Sn and straight line b is the distance d y2 .

7. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 6, characterized in that: The distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark point is measured by the following method: The projection points of the most anterior and most posterior points of the condyle in the Z-axis direction on the lateral head projection view are defined as C-ant point and C-pos point respectively; Draw perpendicular lines l through points C-ant and C-pos respectively and perpendicular to the horizontal reference plane C-ant and l C-pos ; Take equal parts C-ant and l C-pos The vertical line of the distance between them is l, and the vertical line l is the best position of the Z-axis laser positioning line when shooting cone beam CT of the temporomandibular joint; The distance between the most convex point T on the posterior edge of the tragus on the same side and the vertical line l is the distance between the optimal position of the Z-axis laser positioning line in the lateral view and the second body surface landmark point, expressed as d z .

8. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 7, characterized in that: The moving distance of the positioning line of the small field of view cone beam CT scanning relative to the body surface landmark point in the corresponding coordinate axis includes: The X-axis laser positioning line in the frontal view takes the outer canthus of the eye as the body surface landmark and moves along the X-axis toward the outside of the eye. is the distance d corresponding to multiple subjects x The average value of The Y-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark and coincides with the most convex point of the posterior edge of the tragus; The Z-axis laser positioning line in the lateral view takes the most convex point of the posterior edge of the tragus as the body surface landmark, and moves along the Z-axis direction toward the front of the nose. is the distance d corresponding to multiple subjects z The average value of .

9. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 8, characterized in that: During the large-field cone-beam CT scanning, the X-axis laser positioning line in the frontal view is set at the midline of the face, and the moving distance of the Y-axis and Z-axis laser positioning lines in the side view relative to the body surface landmarks in the corresponding coordinate axes is the same as the moving distance of the small-field cone-beam CT.

10. The method for positioning the temporomandibular joint using body surface landmarks assisted by cone beam CT scanning according to claim 1, characterized in that: Based on the 3D reconstructed view of the head, the head position correction is performed using the anatomical landmark method, including: The orbito-auricular plane is established with the midpoint between the bilateral infraorbital points and the upper points of the bilateral bony external auditory canals. The orbito-auricular plane is a horizontal reference plane parallel to the ground plane. The median sagittal plane perpendicular to the horizontal plane and the coronal plane perpendicular to both the horizontal reference plane and the median sagittal plane are established to complete the head position correction.

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