CN114972239A - Method and system for generating oral panoramic image based on oral CBCT (cone beam computed tomography) image - Google Patents
Method and system for generating oral panoramic image based on oral CBCT (cone beam computed tomography) image Download PDFInfo
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Abstract
The invention provides a method and a system for generating an oral panoramic image based on an oral CBCT image, wherein the method comprises the following steps: acquiring a CBCT image of the oral cavity; obtaining a tooth projection image according to the oral CBCT image; obtaining a dental arch curve according to the tooth projection image; sampling according to the dental arch curve to obtain an oral three-dimensional curved surface; and obtaining the panoramic image of the oral cavity according to the three-dimensional curved surface of the oral cavity. The invention can obtain three-dimensional oral cavity panoramic images, thereby effectively avoiding the overlapping of tooth structures to obtain the oral cavity panoramic images containing clear tooth structures, and carrying out special positioning on the skull of a patient in the CBCT scanning process, thereby avoiding extra and unnecessary radiation dose brought by multiple times of scanning.
Description
Technical Field
The invention relates to the technical field of image processing, in particular to a method for generating an oral cavity panoramic image based on an oral cavity CBCT image and a system for generating the oral cavity panoramic image based on the oral cavity CBCT image.
Background
The oral panoramic imaging is specially used for X-ray examination of the skull and maxillofacial region, and can develop the upper and lower jaws, teeth and temporomandibular joints at one time, so that doctors can obtain panoramic images of the oral dental system, thereby carrying out correct diagnosis and treatment. However, the current panoramic image has certain limitations, because most of two-dimensional projection images, such as teeth, vertebras and other bone tissues are overlapped together, so that the tooth structure is fuzzy and difficult to distinguish; in addition, the existing oral panoramic imaging has higher requirements on positioning of the skull of a patient, the panoramic image is fuzzy and has artifacts and no clinical diagnosis value because of inaccurate skull positioning, and therefore, data needs to be collected again for the patient, and extra and unnecessary radiation dose is brought to the patient.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for generating an oral cavity panoramic image based on an oral cavity CBCT image, which can obtain a three-dimensional oral cavity panoramic image, thereby effectively avoiding the overlapping of tooth structures to obtain the oral cavity panoramic image containing clear tooth structures, and specially positioning the skull of a patient in the CBCT scanning process, thereby avoiding extra and unnecessary radiation dose brought by multiple times of scanning.
The technical scheme adopted by the invention is as follows:
a method for generating an oral cavity panoramic image based on an oral cavity CBCT image comprises the following steps: acquiring a CBCT image of the oral cavity; obtaining a tooth projection image according to the oral CBCT image; obtaining a dental arch curve according to the tooth projection image; sampling according to the dental arch curve to obtain an oral three-dimensional curved surface; and obtaining an oral cavity panoramic image according to the oral cavity three-dimensional curved surface.
According to an embodiment of the present invention, the obtaining of the tooth projection image according to the oral cavity CBCT image comprises the following steps: obtaining a head projection image of the head of the patient in the vertical direction according to the oral CBCT image; acquiring an image segmentation threshold; and segmenting the head projection image according to the image segmentation threshold value to obtain a tooth projection image of the patient tooth in the vertical direction.
According to an embodiment of the invention, said deriving an arch curve from said tooth projection images comprises the steps of: acquiring two-dimensional coordinates of all projection pixels of all teeth in the tooth projection image; and obtaining the dental arch curve according to the two-dimensional coordinates of the projection pixels by adopting a first polynomial formula.
According to an embodiment of the invention, the sampling process according to the dental arch curve to obtain the oral three-dimensional curved surface comprises the following steps: setting a plurality of sampling points on the dental arch curve, wherein a normal direction is also set corresponding to each sampling point; screening out a plurality of two-dimensional planes according to the plurality of sampling points and the corresponding normal directions, wherein each two-dimensional plane at least passes through one sampling point and the corresponding normal direction; segmenting each two-dimensional plane according to the image segmentation threshold value to obtain a tooth plane image of the patient tooth in the two-dimensional plane; obtaining a fitted curve according to the tooth plane image, wherein the fitted curve passes through the teeth of the patient and the middle of a root canal; and obtaining the oral three-dimensional curved surface according to the fitting curve.
According to an embodiment of the present invention, the obtaining of the fitted curve from the tooth plane image includes the following steps: acquiring two-dimensional coordinates of all plane pixels of all teeth in the tooth plane image; and obtaining the fitting curve according to the two-dimensional coordinates of the plane pixels by adopting a second polynomial formula.
According to an embodiment of the present invention, the obtaining the three-dimensional curved surface of the oral cavity according to the fitted curve includes the following steps: acquiring all the fitted curves of all the two-dimensional planes; and combining all the fitted curves of all the two-dimensional planes to obtain the oral three-dimensional curved surface.
According to an embodiment of the invention, the obtaining of the panoramic image of the oral cavity according to the three-dimensional curved surface of the oral cavity comprises the following steps: setting a plurality of secondary sampling points on the oral three-dimensional curved surface, wherein a secondary normal direction is also set corresponding to each secondary sampling point; calculating the image value integral of the oral three-dimensional curved surface according to the secondary sampling points and the corresponding secondary normal directions; and constructing the oral panoramic image according to the image value integral of the oral three-dimensional curved surface.
A system for generating an oral panoramic image based on an oral CBCT image, comprising: the first acquisition module is used for acquiring oral CBCT images; the screening module is used for obtaining a tooth projection image according to the oral CBCT image; a first processing module for deriving an arch curve from the tooth projection image; the second processing module is used for sampling according to the dental arch curve to obtain an oral three-dimensional curved surface; and the construction module is used for obtaining the oral panoramic image according to the oral three-dimensional curved surface.
The invention has the following beneficial effects:
1) the oral cavity panoramic image is a three-dimensional image, and the overlapping of tooth structures can be effectively avoided by optimizing the projection direction and the projection length, so that the oral cavity panoramic image containing clear tooth structures is obtained;
2) the skull of the patient is specially positioned in the CBCT scanning process, so that extra and unnecessary radiation dose caused by multiple times of scanning can be avoided;
3) according to the invention, a plurality of oral panoramic images are obtained by moving the dental arch curve, so that information of different depths can be obtained, and medical diagnosis is facilitated.
Drawings
FIG. 1 is a flow chart of a method for generating an oral panoramic image based on an oral CBCT image according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating the steps of sampling according to the dental arch curve to obtain the three-dimensional curved surface of the oral cavity according to one embodiment of the present invention;
FIG. 3 shows the projection direction and the projection length corresponding to the sampling point on the three-dimensional curved surface of the oral cavity according to an embodiment of the present invention;
FIG. 4 is a flowchart of a method for generating a panoramic image of the oral cavity based on CBCT images of the oral cavity according to an embodiment of the present invention;
FIG. 5 is a schematic representation of a secondary arch curve at various locations in accordance with an embodiment of the present invention;
FIG. 6(a) is a panoramic image of the oral cavity according to the quadratic arch curve corresponding to position 1 in one embodiment of the present invention;
FIG. 6(b) is a panoramic image of the oral cavity according to the second arch curve corresponding to position 2 in an embodiment of the present invention;
FIG. 6(c) is a panoramic image of the oral cavity according to the quadratic arch curve corresponding to position 3 in an embodiment of the present invention;
FIG. 7 is a block diagram of a system for generating a panoramic image of an oral cavity based on CBCT images of the oral cavity according to an embodiment of the present invention;
fig. 8 is a block diagram of a system for generating an oral panoramic image based on an oral CBCT image according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a flowchart of a method for generating an oral cavity panoramic image based on an oral cavity CBCT image according to an embodiment of the present invention.
As shown in fig. 1, the method for generating an oral cavity panoramic image based on an oral cavity CBCT image according to an embodiment of the present invention includes the following steps:
and S1, acquiring oral CBCT images.
Specifically, the patient may be scanned via oral CBCT to acquire oral CBCT images of the patient.
And S2, obtaining a tooth projection image according to the oral CBCT image.
Specifically, a head projection image of the head of the patient in the vertical direction can be obtained according to the oral cavity CBCT image, then an image segmentation threshold, namely an image segmentation threshold of the tooth projection image and other tissue structure projection images in the oral cavity CBCT image, can be obtained, and then the head projection image can be segmented according to the image segmentation threshold so as to obtain the tooth projection image of the teeth of the patient in the vertical direction. It should be noted that, since the projection value of the tooth structure has a significant difference from the projection values of other tissue structures, the head projection image may be segmented by setting an image segmentation threshold to obtain the tooth projection image.
More specifically, when a head projection image of the patient's head in the vertical direction is obtained from the oral CBCT images, the oral CBCT images may be added in the vertical direction to obtain a projection image of the patient's head in the vertical direction.
And S3, obtaining an arch curve according to the tooth projection image.
Specifically, all projection pixel two-dimensional coordinates of all teeth in the tooth projection image may be acquired, and then the arch curve may be obtained from the projection pixel two-dimensional coordinates using the first polynomial formula.
In one embodiment of the present invention, the first polynomial formula may be:
wherein (x, y) represents a tooth projection pixel two-dimensional coordinate, c j Denotes a coefficient, j is 1, 2, 3 …, R denotes a constant (for example, 2), and x denotes j Representing the j-th power of the coordinate x.
In one embodiment of the invention, c j The coefficient c of the F (c) equation when the F (c) equation is minimum can be obtained by solving and optimizing the F (c) equation j As in the first polynomial formulaCorresponding valuation, specifically, the expression of the equation f (c) is:
wherein (x) i ，y i ) Representing the two-dimensional coordinates of the projection pixel of the ith tooth,
denotes the coordinate x i To the power of j, i is 1, 2, 3 …, and N, N represents the number of projected pixels.
And S4, sampling according to the dental arch curve to obtain the oral three-dimensional curved surface.
Specifically, as shown in fig. 2, the step S4 includes the following steps:
s401, setting a plurality of sampling points on the dental arch curve, wherein a normal direction is also set corresponding to each sampling point.
In one embodiment of the present invention, the plurality of sampling points set on the dental arch curve may be given by x i I × dx (dx represents the pixel size in the CBCT image of the oral cavity), and the coordinates of the sampling points on the dental arch curve (x) can be obtained by combining the first polynomial equation i ,y i ) Where i is 1, 2, 3 …, P.
Further, the normal direction of the corresponding sampling point can be obtained by adopting the following formula:
s402, screening out a plurality of two-dimensional planes according to the plurality of sampling points and the corresponding normal directions, wherein each two-dimensional plane at least passes through one sampling point and the corresponding normal direction.
In particular, a two-dimensional plane passing through the sampling point and the corresponding normal direction, i.e. perpendicular to the dental arch curve, may be generated based on the coordinates of each sampling point and the corresponding normal direction.
And S403, segmenting each two-dimensional plane according to the image segmentation threshold value to obtain a tooth plane image of the patient tooth in the two-dimensional plane.
And S404, obtaining a fitting curve according to the tooth plane image, wherein the fitting curve passes through the teeth of the patient and the middle of the root canal.
Specifically, all plane pixel two-dimensional coordinates of all teeth in the tooth plane image may be obtained first, and then a fitting curve may be obtained according to the plane pixel two-dimensional coordinates by using the second polynomial formula.
In one embodiment of the present invention, the second polynomial formula may be:
wherein z represents a fitted curve, b j Denotes a coefficient, j is 1, 2, 3 …, T, and T denotes a constant (for example, may be 4).
In one embodiment of the invention, b j The coefficient b of the G (b) equation at the minimum value can be obtained by solving and optimizing the G (b) equation j As the corresponding valuation in the first polynomial equation above, specifically, the expression of the g (b) equation is:
wherein (x) i ,z i ) Representing two-dimensional coordinates of planar pixels, where i is 1, 2, 3 …, M represents the number of planar pixels, w i A weight parameter (which may be 1 in particular) is represented.
In one embodiment of the invention, the fitting range may be set, i.e. x may be set i I x dx (dx represents the pixel size in the oral CBCT image), which in turn can be combined with a second polynomial formula to derive fitted curve coordinates (x ×) i ,z i ) Where i is 1, 2, 3 …, Q. It should be noted that the fitted curve may pass through the tooth and the middle of the root canal.
And S405, obtaining the oral three-dimensional curved surface according to the fitting curve.
Specifically, all the fitting curves of all the two-dimensional planes may be obtained first, and then all the fitting curves of all the two-dimensional planes may be combined to obtain the three-dimensional oral surface.
It should be noted that, corresponding to each sampling point on the dental arch curve, a fitting curve with Q sampling points may be generated, so that all the fitting curves may generate P × Q sampling points, and therefore, the three-dimensional oral surface obtained by combining all the fitting curves also has P × Q sampling points, and the three-dimensional oral surface will pass through each tooth and the middle of the root canal.
And S5, obtaining the oral panoramic image according to the oral three-dimensional curved surface.
Specifically, a plurality of secondary sampling points can be arranged on the oral cavity three-dimensional curved surface, wherein a secondary normal direction is also arranged corresponding to each secondary sampling point, then, the image value integral of the three-dimensional curved surface can be calculated according to the plurality of secondary sampling points and the corresponding secondary normal direction, and finally, the oral cavity panoramic image can be constructed according to the image value integral of the three-dimensional curved surface. It should be noted that the secondary sampling points on the oral three-dimensional curved surface are sampling points on each fitting curve in the oral three-dimensional curved surface, that is, sampling points on the corresponding dental arch curve, and therefore, the oral three-dimensional curved surface has P × Q secondary sampling points.
More specifically, the normal direction corresponding to each secondary sampling point on the oral three-dimensional curved surface may be re-determined with reference to the above-mentioned determination process of the normal direction of the sampling point on the dental arch curve, and then, from each secondary sampling point, the image value integral of the oral three-dimensional curved surface may be calculated with the re-determined normal direction as the projection direction, so as to obtain the oral panoramic image corresponding to the oral three-dimensional curved surface (refer to fig. 3). As shown in fig. 3, when calculating the integral of the image value of the oral cavity three-dimensional curved surface, it is further required to introduce a projection length, which is a constant, for example, 4 × dx (dx is the pixel size of the oral cavity CBCT image).
Of course, in other embodiments of the present invention, the projection length may be adjusted according to clinical requirements, and the adjustment range may be [1 × dx, 100 × dx ], wherein the contrast of the root canal of the tooth may be increased by decreasing the projection length, so that the overlapping rate may be decreased to avoid the non-interested regions such as the spine, and in addition, the obtained image may be ensured to include more tooth structures by increasing the projection length.
Further, as shown in fig. 4, the method for generating an oral cavity panoramic image based on an oral cavity CBCT image according to an embodiment of the present invention further includes the following steps:
s6, obtaining a curve displacement parameter;
s7, moving the dental arch curve according to the curve displacement parameter to obtain a plurality of secondary dental arch curves;
s8, repeating the steps S4-S5 according to the plurality of secondary dental arch curves to obtain a plurality of oral panoramic images.
In one embodiment of the present invention, a third polynomial equation may be used to shift the dental arch curve according to the curve displacement parameter to obtain a plurality of secondary dental arch curves, wherein the third polynomial equation is as follows:
wherein s represents a curve displacement parameter, including s-15 × 2 × dx, -14 × 2 × dx, …, 14 × 2 × dx (dx represents the pixel size of the oral CBCT image), for 30 curve displacement parameters.
For example, as shown in fig. 5, the position 1 may correspond to a secondary arch curve at S-15 × 2 × dx, according to which the oral panoramic image shown in fig. 6(a) can be obtained by performing steps S4-S5; position 2 may correspond to a secondary arch curve when S is 0, from which the oral panoramic image shown in fig. 6(b) may be obtained by performing steps S4-S5; the position 2 may correspond to a secondary arch curve of S14 × 2 × dx, and the oral cavity panoramic image shown in fig. 6(c) may be obtained by performing steps S4 to S5 based on the secondary arch curve, so that a three-layered oral cavity panoramic image having different depths may be obtained, thereby obtaining different depth information and facilitating medical diagnosis.
Of course, in other embodiments of the present invention, noise reduction processing may be performed on the panoramic images of the oral cavity at different depths to improve the contrast of the panoramic images of the oral cavity.
The invention has the following beneficial effects:
1) the oral cavity panoramic image is a three-dimensional image, and the overlapping of tooth structures can be effectively avoided by optimizing the projection direction and the projection length, so that the oral cavity panoramic image containing clear tooth structures is obtained.
2) The invention performs special positioning on the skull of the patient in the CBCT scanning process, thereby avoiding extra and unnecessary radiation dose brought by multiple times of scanning.
3) According to the invention, a plurality of oral panoramic images are obtained by moving the dental arch curve, so that information of different depths can be obtained, and medical diagnosis is facilitated.
Corresponding to the method for generating the oral cavity panoramic image based on the oral cavity CBCT image in the embodiment, the invention further provides a system for generating the oral cavity panoramic image based on the oral cavity CBCT image.
As shown in fig. 7, the system for generating an oral cavity panoramic image based on an oral cavity CBCT image according to an embodiment of the present invention includes a first acquiring module 10, a screening module 20, a first processing module 30, a second processing module 40, and a constructing module 50. The first acquisition module 10 is used for acquiring oral CBCT images; the screening module 20 is used for obtaining a tooth projection image according to the oral CBCT image; the first processing module 30 is used for obtaining an arch curve according to the tooth projection image; the second processing module 40 is used for sampling according to the dental arch curve to obtain the oral three-dimensional curved surface; the construction module 50 is used for obtaining the panoramic image of the oral cavity according to the three-dimensional curved surface of the oral cavity.
In one embodiment of the present invention, the first acquisition module 10 may scan the patient through oral CBCT to acquire oral CBCT images of the patient.
In an embodiment of the present invention, the screening module 20 may obtain a head projection image of the head of the patient in the vertical direction according to the oral CBCT image, and then may obtain an image segmentation threshold, i.e., an image segmentation threshold of the tooth projection image and the other tissue structure projection images in the oral CBCT image, and further may segment the head projection image according to the image segmentation threshold, so as to obtain the tooth projection image of the teeth of the patient in the vertical direction. It should be noted that, since the projection value of the tooth structure has a significant difference from the projection values of other tissue structures, the head projection image may be segmented by setting an image segmentation threshold to obtain the tooth projection image.
More specifically, when a head projection image of the patient's head in the vertical direction is obtained from the oral CBCT images, the oral CBCT images may be added in the vertical direction to obtain a projection image of the patient's head in the vertical direction.
In one embodiment of the present invention, the first processing module 30 may be configured to obtain all projected pixel two-dimensional coordinates of all teeth in the projected tooth image, and then may obtain the arch curve from the projected pixel two-dimensional coordinates using the first polynomial equation.
In one embodiment of the present invention, the first polynomial formula may be:
wherein (x, y) represents a tooth projection pixel two-dimensional coordinate, c j Denotes a coefficient, j is 1, 2, 3 …, R denotes a constant (for example, 2), and x denotes j Representing the j-th power of the coordinate x.
In one embodiment of the invention, c j The coefficient c of the F (c) equation when the F (c) equation is minimum can be obtained by solving and optimizing the F (c) equation j As the corresponding valuation in the above first polynomial equation, specifically, the expression of the f (c) equation is:
wherein (x) i ，y i ) Representing the two-dimensional coordinates of the projection pixel of the ith tooth,
denotes the coordinate x i To the power of j, i is 1, 2, 3 …, and N, N represents the number of projected pixels.
In an embodiment of the present invention, the second processing module 40 may be configured to set a plurality of sampling points on the dental arch curve, wherein a normal direction is further set corresponding to each sampling point, and then a plurality of two-dimensional planes may be screened according to the plurality of sampling points and the corresponding normal direction, wherein each two-dimensional plane passes through at least one sampling point and the corresponding normal direction, and then each two-dimensional plane may be segmented according to an image segmentation threshold to obtain a tooth plane image of a patient's tooth in the two-dimensional plane, and then a fitting curve may be obtained according to the tooth plane image, wherein the fitting curve passes through the middle of the patient's tooth and a root canal, and finally an oral cavity three-dimensional curved surface may be obtained according to the fitting curve.
In one embodiment of the present invention, the plurality of sampling points set on the dental arch curve may be given by x i I × dx (dx represents the pixel size in the CBCT image of the oral cavity), and the coordinates of the sampling points on the dental arch curve (x) can be obtained by combining the first polynomial equation i ,y i ) Where i is 1, 2, 3 …, P.
Further, the normal direction of the corresponding sampling point can be obtained by adopting the following formula:
thus, a two-dimensional plane passing through the sampling point and the corresponding normal direction, i.e. perpendicular to the dental arch curve, can be generated based on the coordinates of each sampling point and the corresponding normal direction.
In one embodiment of the present invention, in the process of obtaining the fitting curve according to the tooth plane image, the two-dimensional coordinates of all plane pixels of all teeth in the tooth plane image may be obtained first, and then the fitting curve may be obtained according to the two-dimensional coordinates of the plane pixels by using the second polynomial formula.
Wherein the second polynomial formula may be:
wherein z represents a fitted curve, b j Denotes a coefficient, j is 1, 2, 3 …, T, and T denotes a constant (for example, may be 4).
In one embodiment of the invention, b j The coefficient b of the G (b) equation at the minimum value can be obtained by solving and optimizing the G (b) equation j As the corresponding valuation in the first polynomial equation above, specifically, the expression of the g (b) equation is:
wherein (x) i ,z i ) Representing two-dimensional coordinates of planar pixels, where i is 1, 2, 3 …, M represents the number of planar pixels, w i A weight parameter (which may be 1 in particular) is represented.
Further, a fitting range may be set, i.e., x may be set i I x dx (dx represents the pixel size in the oral CBCT image), which in turn can be combined with a second polynomial formula to derive fitted curve coordinates (x ×) i ,z i ) Where i is 1, 2, 3 …, Q, and the fitted curve may pass through the tooth and the root canal center.
In one embodiment of the present invention, in the process of obtaining the oral three-dimensional curved surface according to the fitted curves, all the fitted curves of all the two-dimensional planes may be obtained first, and then all the fitted curves of all the two-dimensional planes may be combined to obtain the oral three-dimensional curved surface.
It should be noted that, corresponding to each sampling point on the dental arch curve, a fitting curve with Q sampling points may be generated, so that all the fitting curves may generate P × Q sampling points, and therefore, the three-dimensional oral surface obtained by combining all the fitting curves also has P × Q sampling points, and the three-dimensional oral surface will pass through each tooth and the middle of the root canal.
In an embodiment of the present invention, the constructing module 50 may be configured to set a plurality of secondary sampling points on the oral cavity three-dimensional curved surface, wherein a secondary normal direction is further set for each secondary sampling point, and then an image value integral of the three-dimensional curved surface may be calculated according to the plurality of secondary sampling points and the corresponding secondary normal direction, and finally an oral cavity panoramic image may be constructed according to the image value integral of the three-dimensional curved surface. It should be noted that the secondary sampling points on the oral three-dimensional curved surface are sampling points on each fitting curve in the oral three-dimensional curved surface, that is, sampling points on the corresponding dental arch curve, and therefore, the oral three-dimensional curved surface has P × Q secondary sampling points.
More specifically, the building module 50 may refer to the above-mentioned process of determining the normal direction of the sampling points on the dental arch curve, re-determine the corresponding normal direction for each secondary sampling point on the oral three-dimensional curved surface, and then may calculate the image value integral of the oral three-dimensional curved surface from each secondary sampling point by using the re-determined normal direction as the projection direction, so as to obtain the oral panoramic image corresponding to the oral three-dimensional curved surface (refer to fig. 3). As shown in fig. 3, when calculating the integral of the image value of the oral cavity three-dimensional curved surface, it is further required to introduce a projection length, which is a constant, for example, 4 × dx (dx is the pixel size of the oral cavity CBCT image).
Of course, in other embodiments of the present invention, the projection length may be adjusted according to clinical requirements, and the adjustment range may be [1 × dx, 100 × dx ], wherein the contrast of the root canal of the tooth may be increased by decreasing the projection length, so that the overlapping rate may be decreased to avoid the non-interested regions such as the spine, and in addition, the obtained image may be ensured to include more tooth structures by increasing the projection length.
Further, as shown in fig. 8, the method for generating an oral cavity panoramic image based on an oral cavity CBCT image according to an embodiment of the present invention further includes a second acquiring module 60, a third processing module 70, and a fourth processing module 80. The second obtaining module 60 may be configured to obtain a curve displacement parameter; the third processing module 70 may be configured to move the dental arch curve according to the curve displacement parameter to obtain a plurality of secondary dental arch curves; fourth processing module 80 may be configured to obtain a plurality of panoramic images of the oral cavity from the plurality of secondary arch curves via second processing module 40 and construction module 50.
In an embodiment of the present invention, the third processing module 70 may move the dental arch curve according to the curve displacement parameter by using a third polynomial equation to obtain a plurality of secondary dental arch curves, wherein the third polynomial equation is as follows:
wherein s represents a curve displacement parameter, including s-15 × 2 × dx, -14 × 2 × dx, …, 14 × 2 × dx (dx represents the pixel size of the oral CBCT image), for 30 curve displacement parameters.
For example, as shown in fig. 5, the position 1 may correspond to a secondary arch curve at S-15 × 2 × dx, according to which the oral panoramic image shown in fig. 6(a) can be obtained by performing steps S4-S5; position 2 may correspond to a secondary arch curve when S is 0, from which the oral panoramic image shown in fig. 6(b) may be obtained by performing steps S4-S5; the position 2 may correspond to a secondary arch curve of S14 × 2 × dx, and the oral cavity panoramic image shown in fig. 6(c) may be obtained by performing steps S4 to S5 based on the secondary arch curve, so that a three-layered oral cavity panoramic image having different depths may be obtained, thereby obtaining different depth information and facilitating medical diagnosis.
Of course, in other embodiments of the present invention, noise reduction processing may also be performed on the panoramic images of the oral cavity at different depths to improve the contrast of the panoramic images of the oral cavity.
The invention has the following beneficial effects:
1) the oral cavity panoramic image is a three-dimensional image, and the overlapping of tooth structures can be effectively avoided by optimizing the projection direction and the projection length, so that the oral cavity panoramic image containing clear tooth structures is obtained.
2) The invention performs special positioning on the skull of the patient in the CBCT scanning process, thereby avoiding extra and unnecessary radiation dose brought by multiple times of scanning.
3) According to the invention, a plurality of oral panoramic images are obtained by moving the dental arch curve, so that information of different depths can be obtained, and medical diagnosis is facilitated.
In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. The meaning of "plurality" is two or more unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Claims (8)
1. A method for generating an oral panoramic image based on an oral CBCT image is characterized by comprising the following steps:
acquiring a CBCT image of the oral cavity;
obtaining a tooth projection image according to the oral CBCT image;
obtaining a dental arch curve according to the tooth projection image;
sampling according to the dental arch curve to obtain an oral three-dimensional curved surface;
and obtaining an oral panoramic image according to the oral three-dimensional curved surface.
2. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 1, wherein the step of obtaining the projection image of the tooth according to the CBCT image of the oral cavity comprises the following steps:
obtaining a head projection image of the head of the patient in the vertical direction according to the oral CBCT image;
acquiring an image segmentation threshold;
and segmenting the head projection image according to the image segmentation threshold value to obtain a tooth projection image of the patient tooth in the vertical direction.
3. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 2, wherein the arch curve is obtained according to the projection image of the teeth, comprising the following steps:
acquiring two-dimensional coordinates of all projection pixels of all teeth in the tooth projection image;
and obtaining the dental arch curve according to the two-dimensional coordinates of the projection pixels by adopting a first polynomial formula.
4. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 3, wherein the sampling process is performed according to the dental arch curve to obtain the three-dimensional curved surface of the oral cavity, comprising the following steps:
setting a plurality of sampling points on the dental arch curve, wherein a normal direction is also set corresponding to each sampling point;
screening out a plurality of two-dimensional planes according to the plurality of sampling points and the corresponding normal directions, wherein each two-dimensional plane at least passes through one sampling point and the corresponding normal direction;
segmenting each two-dimensional plane according to the image segmentation threshold value to obtain a tooth plane image of the patient teeth in the two-dimensional plane;
obtaining a fitted curve from the dental plane image, wherein the fitted curve passes through the teeth of the patient and the middle of the root canal;
and obtaining the oral three-dimensional curved surface according to the fitting curve.
5. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 4, wherein the step of obtaining the fitted curve according to the tooth plane image comprises the following steps:
acquiring two-dimensional coordinates of all plane pixels of all teeth in the tooth plane image;
and obtaining the fitting curve according to the two-dimensional coordinates of the plane pixels by adopting a second polynomial formula.
6. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 5, wherein the step of obtaining the three-dimensional curved surface of the oral cavity according to the fitted curve comprises the following steps:
acquiring all the fitted curves of all the two-dimensional planes;
and combining all the fitted curves of all the two-dimensional planes to obtain the oral three-dimensional curved surface.
7. The method for generating the panoramic image of the oral cavity based on the CBCT image of the oral cavity as claimed in claim 6, wherein the step of obtaining the panoramic image of the oral cavity according to the three-dimensional curved surface of the oral cavity comprises the following steps:
setting a plurality of secondary sampling points on the oral three-dimensional curved surface, wherein a secondary normal direction is also set corresponding to each secondary sampling point;
calculating the image value integral of the oral three-dimensional curved surface according to the secondary sampling points and the corresponding secondary normal directions;
and constructing the oral panoramic image according to the image value integral of the oral three-dimensional curved surface.
8. A system for generating an oral panoramic image based on an oral CBCT image, comprising:
the first acquisition module is used for acquiring an oral CBCT image;
the screening module is used for obtaining a tooth projection image according to the oral CBCT image;
a first processing module for deriving an arch curve from the tooth projection image;
the second processing module is used for sampling according to the dental arch curve to obtain an oral three-dimensional curved surface;
and the construction module is used for obtaining the oral panoramic image according to the oral three-dimensional curved surface.
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