Method for automatically selecting and reconstructing central layer

Abstract

The invention provides a method for automatically selecting and reconstructing a central layer, which comprises the following steps of: performing an automatic layer selection step on at least one plane of an x plane, a y plane and a z plane of a cone beam computed tomography system, namely performing rotary scanning on a measured object to obtain at least one original projection drawing, and obtaining a target projection drawing according to the original projection drawing; a preset number of target rows and columns are selected from a pixel point matrix of the target projection drawing, reconstruction rows and columns are obtained according to the target rows and columns and serve as reconstruction center layers of the corresponding planes, and the preset number is a natural number larger than or equal to 1. Through the method provided by the invention, the problem that in the prior art, only manual adjustment can be carried out, and the reconstruction center layer cannot be automatically selected is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of CT imaging, and in particular to a method for automatically selecting and reconstructing a central layer. Background Art

[0002] Cone-beam computed tomography (CBCT) systems typically consist of a flat-panel detector and an X-ray tube mounted on a C-arm. Cone-beam backprojection is a key image reconstruction technique in CBCT systems. Image reconstruction using cone-beam backprojection requires the geometry of the scanning trajectory; errors in this trajectory can lead to geometric artifacts in the reconstructed image. Therefore, geometric correction of the trajectory in the CBCT system is necessary before image reconstruction.

[0003] Unlike pre-scanning a specific geometric phantom and performing geometric correction based on geometric relationships, Kingston, AM, et al. proposed a real-time geometric correction method in their 2010 paper, "An auto-focus method for generating sharp 3D tomographic images." This method involves reconstructing a fixed center layer, for example, the center layer of the z plane or a layer at a fixed distance from the center layer. However, in reality, fixed layers may not necessarily contain objects, resulting in insufficient information in the reconstructed image and certain errors in calculating clarity. In this case, manual adjustment of the reconstructed center layer is required. Given this, how to automatically select the reconstruction center layer has become a technical problem that those skilled in the art are eager to solve.

[0004] It should be noted that the above technical background is merely provided to provide a clear and complete description of the technical solutions of the present invention and to facilitate understanding by those skilled in the art. Simply because these solutions are described in the technical background section of the present invention, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a method for automatically selecting and reconstructing a central layer, so as to solve the problem in the prior art that the central layer can only be manually adjusted and cannot be automatically selected and reconstructed.

[0006] To achieve the above and other related objectives, the present invention provides a method for automatically selecting a reconstruction center layer, the method comprising:

[0007] Performing an automatic layer selection step on at least one of an x-plane, a y-plane, and a z-plane of a cone-beam computed tomography system, wherein the automatic layer selection step comprises:

[0008] Performing rotational scanning on the object to be measured to obtain at least one original projection image, and thereby obtaining a target projection image;

[0009] A preset number of target rows and columns are selected from the pixel matrix of the target projection image, and reconstructed rows and columns are obtained as the reconstructed central layer of the corresponding plane, wherein the preset number is a natural number greater than or equal to 1.

[0010] Optionally, when performing the automatic layer selection step for the x-plane:

[0011] If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image;

[0012] If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on the plurality of original projection images to obtain a plurality of corrected projection images; processing pixels corresponding to each pixel point in the plurality of corrected projection images to obtain target pixels corresponding to each pixel point, and thereby obtaining the target projection image;

[0013] and / or,

[0014] If the preset number is one, the method for obtaining the reconstructed central layer includes: traversing each column of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each column, and taking the column corresponding to the maximum value as the reconstructed central layer of the x-plane;

[0015] If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval columns corresponding to each column from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval columns corresponding to each column are respectively recorded as each interval group; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval columns in the interval group corresponding to the maximum value as each target column, and then obtaining a reconstructed column based on each target column and using it as the reconstructed center layer of the x-plane.

[0016] Optionally, when performing the automatic layer selection step for the y plane:

[0017] If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image;

[0018] If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on each of the plurality of original projection images to obtain a plurality of corrected projection images; selecting a corrected projection image corresponding to a target rotation angle from the plurality of corrected projection images as the target projection image, wherein the target rotation angle differs from the initial rotation angle by a preset angle, and the preset angle is greater than 0° and less than 360°;

[0019] and / or,

[0020] If the preset number is one, the method for obtaining the reconstructed center layer includes: traversing each column of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each column, and taking the column corresponding to the maximum value as the reconstructed center layer of the y plane;

[0021] If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval columns corresponding to each column from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval columns corresponding to each column are respectively recorded as interval groups; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval columns in the interval group corresponding to the maximum value as each target column, and then obtaining a reconstructed column based on each target column and using it as the reconstructed center layer of the y plane.

[0022] Optionally, when performing the automatic layer selection step for the z-plane:

[0023] If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image;

[0024] If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on the plurality of original projection images to obtain a plurality of corrected projection images; processing pixels corresponding to each pixel point in the plurality of corrected projection images to obtain target pixels corresponding to each pixel point, and thereby obtaining the target projection image;

[0025] and / or,

[0026] If the preset number is one, the method for obtaining the reconstructed center layer includes: traversing each row of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each row, and taking the row corresponding to the maximum value as the reconstructed center layer of the z plane;

[0027] If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval rows corresponding to each row from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval rows corresponding to each row are respectively recorded as each interval group; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval rows in the interval group corresponding to the maximum value as each target row, and then obtaining a reconstructed row based on each target row and using it as the reconstructed center layer of the z plane.

[0028] Optionally, in the method for obtaining the target projection image:

[0029] If the number of the original projection images is one, the method for obtaining the corrected projection image includes: performing a rotation scan in the absence of a measured object to obtain an air projection image, and performing air correction on the original projection image based on the air projection image to obtain the corrected projection image, wherein the rotation angles corresponding to the air projection image and the original projection image are equal;

[0030] If the number of the original projection images is greater than one, the method for obtaining several corrected projection images includes:

[0031] When there is no object to be measured, a rotation scan is performed to obtain several air projection images, including several air projection images and several original projection images. Figure 1 One to one correspondence, and the rotation angles of the corresponding air projection image and the original projection image are equal;

[0032] Based on the several air projection images, air correction is performed on the several original projection images respectively to obtain several corrected projection images; or, the several air projection images are processed to obtain multiplexed projection images, and based on the multiplexed projection images, air correction is performed on the several original projection images to obtain several corrected projection images.

[0033] Optionally, the method for obtaining the multiplexed projection image includes: processing pixels corresponding to each pixel point in a plurality of air projection images respectively to obtain air pixels corresponding to each pixel point, and thereby obtaining the multiplexed projection image.

[0034] Optionally, when the original projection image is air-corrected based on the air projection image: the corrected projection image = -logn (original projection image / air projection image); when the original projection image is air-corrected based on the multiplexed projection image: the corrected projection image = -logn (original projection image / multiplexed projection image).

[0035] Optionally, in the method for obtaining a target projection image executed on at least one of the x-plane and the z-plane, if the number of the original projection images is greater than one, the target pixel corresponding to each pixel point is obtained by averaging the pixels corresponding to each pixel point in several corrected projection images, and the target projection image is obtained thereby; in the method for obtaining a reconstructed central layer executed on at least one of the x-plane, the y-plane and the z-plane, if the preset number is greater than one, the reconstructed row and column are obtained by averaging the row and column numbers corresponding to each target row and column and used as the reconstructed central layer of the corresponding plane; in the method for obtaining a multiplexed projection image, the air pixel corresponding to each pixel point is obtained by averaging the pixels corresponding to each pixel point in several air projection images, and the multiplexed projection image is obtained thereby.

[0036] Optionally, in the method for obtaining the reconstructed center layer executed on at least one of the x-plane and the y-plane, the preset interval value is less than half of the total number of columns in the pixel matrix; in the method for obtaining the reconstructed center layer executed on the z-plane, the preset interval value is less than half of the total number of rows in the pixel matrix.

[0037] Optionally, at least one original projection image is obtained by performing rotational scanning based on a cone-beam computed tomography system, wherein:

[0038] If the number of the original projection images is one, then, in the method for obtaining the original projection images performed on at least one of the x-plane and the z-plane, the cone-beam computed tomography system photographs the object under test at any rotation angle to obtain the original projection images; in the method for obtaining the original projection images performed on the y-plane, the cone-beam computed tomography system rotates by a preset angle starting from the initial rotation angle and then photographs the object under test to obtain the original projection images;

[0039] If the number of the original projection images is greater than one, then, in the method for obtaining the original projection images, the cone-beam computed tomography system takes the initial rotation angle as the starting point and performs rotation scanning based on the interval angle, and photographs the object under test at different rotation angles to obtain several original projection images.

[0040] As described above, the method of automatically selecting the reconstructed center layer of the present invention obtains the target projection image based on the original projection image of the object to be measured, and selects a preset number of rows or columns with the largest pixel density as target rows and columns in the pixel matrix of the target projection image, and then obtains the reconstructed rows and columns as the reconstructed center layer based on the preset number of target rows and columns; it can not only provide sufficient reconstructed image information to improve accuracy, but also avoid manual adjustment to achieve automatic layer selection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1Shown is a structural schematic diagram of a CBCT system in an embodiment of the present invention.

[0042] Figure 2 Shown is a flow chart of the automatic layer selection steps in an embodiment of the present invention.

[0043] Figure 3 Shown is a schematic diagram of an original projection image corresponding to an embodiment of the present invention when the object to be measured is a lithium battery.

[0044] Figure 4 Display as Figure 3 The corrected projection image corresponding to the original projection image is shown.

[0045] Figure 5 Shown is a schematic diagram of a target projection diagram corresponding to an embodiment of the present invention when the object to be measured is a lithium battery.

[0046] Figure 6 Another schematic diagram of the target projection diagram corresponding to the case where the object to be measured is a lithium battery in an embodiment of the present invention is shown.

[0047] Component number description

[0048] 100 CBCT system

[0049] 101 C-arm

[0050] 102 X-ray tube

[0051] 103 Flat Panel Detector DETAILED DESCRIPTION

[0052] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0053] See also Figures 1 to 6 It should be noted that the illustrations provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the form, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0054] The cone beam computed tomography (CBCT) system 100 includes a C-arm 101, an X-ray tube 102, and a flat panel detector 103, wherein the X-ray tube 102 and the flat panel detector 103 are respectively fixed at both ends of the C-arm 101. Figure 1In practical applications, for the CBCT system 100, the line from the focus of the X-ray tube 102 to the center of the flat panel detector 103 is usually denoted as the y-axis, the x-axis is horizontally perpendicular to the y-axis, and the z-axis is vertically perpendicular to the y-axis. The x-axis and the y-axis together define the x-plane, the y-axis and the z-axis together define the y-plane, and the x-axis and the z-axis together define the z-plane.

[0055] This embodiment provides a method for automatically selecting a reconstruction center layer, including performing an automatic layer selection step on at least one of the x-plane, the y-plane, and the z-plane, so that in a related method requiring the reconstruction of the center layer (for example, a geometric trajectory real-time correction method, or a 3D image reconstruction method), the automatic layer selection of the reconstruction center layer is realized on the corresponding plane, thereby solving the technical problem of the prior art requiring manual adjustment of the reconstruction center layer; wherein, Figure 2 As shown, the automatic layer selection step of this embodiment specifically includes the following, namely, step S1 and step S2.

[0056] In step S1, a rotational scan is performed on the object to obtain at least one original projection image, and a target projection image is obtained from the original projection image. The number of original projection images can be one or more than one. In practical applications, the original projection images are typically obtained by rotationally scanning the object using the CBCT system 100.

[0057] When performing the automatic layer selection step for the x-plane:

[0058] In one embodiment, when the number of original projection images is one, then:

[0059] The method for obtaining the original projection image includes: the CBCT system 100 images the object under test at any rotation angle to obtain the original projection image. For example, the object under test is placed on the stage of the CBCT system 100, and the rotation angle is adjusted to any desired angle. The X-ray tube 102 emits a cone-shaped X-ray beam to irradiate the object under test, and the flat-panel detector 103 captures the cone-shaped X-ray beam that passes through the object under test and generates the original projection image. It should be noted that the selection of the arbitrary rotation angle should be based on actual needs and is not subject to excessive restrictions.

[0060] The method for obtaining a target projection image includes: performing air correction on an original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image. In one example, the method for obtaining a corrected projection image includes: performing a rotation scan in the absence of a test object to obtain an air projection image, and performing air correction on the original projection image based on the air projection image to obtain a corrected projection image, wherein the rotation angles corresponding to the air projection image and the original projection image are equal. In conjunction with the above, after removing the test object placed on the stage of the CBCT system 100, an air projection image is obtained by photographing the CBCT system 100 at the same rotation angle; wherein the corrected projection image = -logn(original projection image / air projection image).

[0061] In another embodiment, when the number of original projection images is greater than one, then:

[0062] The method for obtaining the original projection images includes: the CBCT system 100 performs rotational scanning based on an initial rotation angle and interval angles, photographing the object under test at different rotation angles to obtain a plurality of original projection images. For example, the object under test is placed on the stage of the CBCT system 100, the X-ray tube 102 emits a cone-shaped X-ray beam to irradiate the object under test, the flat-panel detector 103 captures the cone-shaped X-ray beam passing through the object under test and generates an original projection image, and the C-arm 101 synchronously rotates the X-ray tube 102 and the flat-panel detector 103 to obtain original projection images of the object under test at different rotation angles, thereby obtaining a plurality of original projection images.

[0063] In practical applications, when a plurality of original projection images are obtained based on the CBCT system 100, the total rotation angle of the CBCT system 100 can be set to be greater than or equal to 180°, and the interval angle can be set to be less than or equal to 1°. For example, the total rotation angle is 360°, and the interval angle is 0.6°. That is, the CBCT system 100 obtains an original projection image every time it rotates 0.6°, and a total of 600 original projection images are obtained during the 360° rotation scanning process. For example, the object to be measured is a lithium battery and the initial rotation angle is 0°. Figure 3 It is the first of the 600 original projection images, that is, the original projection image corresponding to the rotation angle of 0°.

[0064] It should be noted that the resolution of the original projection image determines the resolution of subsequent projection images (e.g., correction projection images, target projection images, etc.), and the resolution of the original projection image is generally determined by the resolution of the flat-panel detector 103 in the CBCT system 100. The specific design should be based on actual needs and no excessive restrictions are imposed on this. In this embodiment, the resolution of the flat-panel detector 103 is 2496*3008. Thus, the resolution of each projection image is 2496*3008, that is, the pixel matrix of each projection image includes 2496 columns and 3008 rows.

[0065] The method for obtaining the target projection image specifically includes the following, namely, step S11a and step S12a.

[0066] In step S11a, air correction is performed on the plurality of original projection images to obtain a plurality of corrected projection images. In this embodiment, the plurality of corrected projection images can be obtained based on different methods, as detailed in the specific examples.

[0067] In one example, a method for obtaining a plurality of corrected projection images specifically includes the following: performing a rotation scan without a measured object to obtain a plurality of air projection images, wherein the plurality of air projection images and the plurality of original projection images are Figure 1 One to one, and the corresponding rotation angles of the air projection images and the original projection images are equal; in combination with the above, after the object placed on the stage of the CBCT system 100 is removed, a rotation scan is performed based on the CBCT system 100 to obtain several air projection images, wherein the total rotation angle and interval angle of the CBCT system 100 remain unchanged; for example, the total rotation angle is 360°, the projection interval angle is 0.6°, and the CBCT system 100 obtains an air projection image every time it rotates 0.6°. A total of 600 air projection images are obtained during the 360° rotation scan. Based on the several air projection images, air correction is performed on the several original projection images to obtain several corrected projection images; the several air projection images and the several original projection images are corrected. Figure 1 One-to-one correspondence, that is, any rotation angle corresponds to an air projection image and an original projection image. The original projection image is air-corrected by the air projection image to obtain the corrected projection image at the corresponding rotation angle, wherein at any rotation angle, the corrected projection image = -logn (original projection image / air projection image).

[0068] In another example, a method for obtaining a plurality of corrected projection images specifically includes the following: performing a rotation scan in the absence of a measured object to obtain a plurality of air projection images, wherein the plurality of air projection images and the plurality of original projection images are Figure 1One to one correspondence, and the corresponding rotation angles of the corresponding air projection image and the original projection image are equal; for details, please refer to the relevant content of the previous example and will not be repeated here. Several air projection images are processed to obtain a reused projection image, and several original projection images are air-corrected based on the reused projection image to obtain several corrected projection images; wherein, the method for obtaining the reused projection image includes: separately processing the pixels corresponding to each pixel point in the several air projection images, obtaining the air pixels corresponding to each pixel point, and thereby obtaining the reused projection image; specifically, by averaging the pixels corresponding to each pixel point in the several air projection images, the air pixels corresponding to each pixel point are obtained, and thereby obtaining the reused projection image. For example, first take the average of the 600 pixels corresponding to the pixel point in the first row and first column of the 600 air projection images to obtain the air pixel corresponding to the pixel point, then take the average of the 600 pixels corresponding to the pixel point in the first row and second column of the 600 air projection images to obtain the air pixel corresponding to the pixel point, and so on, obtain the air pixel corresponding to the pixel point in the 3008th row and 2496th column, and then generate a multiplexed projection image based on the air pixels corresponding to each pixel point. In addition, at any rotation angle, the corrected projection image = -logn (original projection image / multiplexed projection image), where, Figure 4 It is based on the reuse of projection images Figure 3 The corrected projection image is obtained after air correction is performed on the original projection image shown.

[0069] Step S12a, respectively process the pixels corresponding to each pixel point in a number of corrected projection images to obtain the target pixel corresponding to each pixel point, and thereby obtain the target projection image; specifically, by taking the average of the pixels corresponding to each pixel point in a number of corrected projection images, the target pixel corresponding to each pixel point is obtained, and thereby obtain the target projection image. For example, first take the average of the 600 pixels corresponding to the pixel point in the 1st row and 1st column of 600 corrected projection images to obtain the target pixel corresponding to the pixel point, then take the average of the 600 pixels corresponding to the pixel point in the 1st row and 2nd column of 600 corrected projection images to obtain the target pixel corresponding to the pixel point, and so on, obtain the target pixel corresponding to the pixel point in the 3008th row and 2496th column, and finally, generate the target projection image based on the target pixels corresponding to each pixel point, wherein, Figure 5 It is the target projection image obtained based on 600 correction projection images.

[0070] When performing the automatic layer selection step on the y plane:

[0071] In one embodiment, when the number of original projection images is one, then:

[0072] The method for obtaining an original projection image includes: rotating the CBCT system 100 by a preset angle starting from an initial rotation angle, and then photographing the object under test to obtain the original projection image; wherein the preset angle is greater than 0° and less than 360°, and as an optional solution, the preset angle is 90°. For example, the object under test is placed on the stage of the CBCT system 100, and after adjusting the rotation angle to 90°, the X-ray tube 102 emits a cone-shaped X-ray beam to irradiate the object under test, and the flat-panel detector 103 captures the cone-shaped X-ray beam that passes through the object under test and generates the original projection image.

[0073] The method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image; wherein the specific method is the same as the method for obtaining the target projection image based on an original projection image in the x-plane. The relevant content can be found above and will not be repeated here.

[0074] In another embodiment, when the number of original projection images is greater than one, then:

[0075] The method for obtaining the original projection images includes: the CBCT system 100 uses an initial rotation angle as a starting point and rotates based on interval angles, photographing the object under test at different rotation angles to obtain a plurality of original projection images. The specific method is the same as the method for obtaining a plurality of original projection images in the x-plane, and the relevant content can be found above and will not be repeated here.

[0076] The method for obtaining the target projection image specifically includes the following, namely, step S11b and step S12b.

[0077] In step S11b, air correction is performed on the original projection images to obtain corrected projection images. The specific method is the same as the method for obtaining corrected projection images in the x-plane (i.e., step S11a). The relevant content can be found above and will not be repeated here.

[0078] Step S12b, selecting a correction projection image corresponding to the target rotation angle from a plurality of correction projection images as the target projection image, wherein the target rotation angle differs from the initial rotation angle by a preset angle; taking the initial rotation angle as 0° and the preset angle as 90° as an example, the target rotation angle is 90°, that is, selecting the correction projection image with a rotation angle of 90° from the 600 correction projection images as the target projection image, that is, selecting the 151st correction projection image from the 600 correction projection images as the target projection image, wherein, Figure 6 This is the selected target projection.

[0079] When performing the automatic layer selection step on the z plane:

[0080] In one embodiment, when the number of original projection images is one, then:

[0081] The method for obtaining the original projection image includes: the CBCT system 100 photographs the object under test at any rotation angle to obtain the original projection image; wherein the specific method is the same as the method for obtaining an original projection image in the x-plane, and the relevant content can be found above and will not be repeated here.

[0082] The method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image; wherein the specific method is the same as the method for obtaining the target projection image based on an original projection image in the x-plane. The relevant content can be found above and will not be repeated here.

[0083] In another embodiment, when the number of original projection images is greater than one, then:

[0084] The method for obtaining the original projection images includes: the CBCT system 100 uses an initial rotation angle as a starting point and rotates based on interval angles, photographing the object under test at different rotation angles to obtain a plurality of original projection images. The specific method is the same as the method for obtaining a plurality of original projection images in the x-plane, and the relevant content can be found above and will not be repeated here.

[0085] The method for obtaining the target projection image specifically includes the following, namely, step S11c and step S12c.

[0086] In step S11c, air correction is performed on the original projection images to obtain corrected projection images. The specific method is the same as the method for obtaining corrected projection images in the x-plane (i.e., step S11a). The relevant method can be found in the above text and will not be repeated here.

[0087] In step S12c, the pixels corresponding to each pixel point in the several corrected projection images are processed separately to obtain the target pixels corresponding to each pixel point, and thereby obtain the target projection image; wherein, the specific method is the same as the method for obtaining the target projection image based on several corrected projection images in the x-plane (i.e., step S12a), and the relevant content can be found in the above, which will not be repeated here.

[0088] Step S2, selecting a preset number of target rows and columns in the pixel matrix of the target projection image, and obtaining the reconstructed rows and columns as the reconstructed center layer of the corresponding plane; wherein the preset number is a natural number greater than or equal to 1. As an optional solution, the preset number is a natural number greater than 1.

[0089] When performing the automatic layer selection step for the x-plane:

[0090] In one embodiment, when the preset number is one, then:

[0091] The method for obtaining the reconstructed central layer includes: traversing each column of the pixel matrix of the target projection image, and obtaining the sum of the pixels corresponding to all the pixels in each column, and taking the column corresponding to the maximum value as the reconstructed central layer of the x plane. For example, for a pixel matrix with 2496 columns and 3008 rows, obtain the sum of the pixels corresponding to all the pixels in each column from the 1st column to the 2496th column, and take the column with the largest sum of pixels as the reconstructed central layer of the x plane.

[0092] In another embodiment, for the case where the preset number is greater than one, then:

[0093] The method for obtaining the reconstructed central layer specifically includes the following, that is, steps S21a to step S23a.

[0094] Step S21a, obtain the preset number of spaced columns corresponding to each column from the pixel matrix of the target projection image based on the preset interval value, and respectively record the preset number of spaced columns corresponding to each column as each spaced group; wherein, the preset interval value is less than half of the total number of columns in the pixel matrix. It should be noted that when performing this step, there is no need to obtain the preset number of spaced columns corresponding to all columns in the pixel matrix, only need to obtain the preset number of spaced columns corresponding to the 1st column to the i-th (1 < i < total number of columns) column, where, in the preset number of spaced columns corresponding to the i-th column, the maximum number of columns is exactly the last column of the pixel matrix.

[0095] For example, the preset interval value is 1 / 8 of the total number of columns in the pixel matrix. For a pixel matrix with 2496 columns and 3008 rows, the preset interval value is 312; taking the preset number as 3 as an example, in this pixel matrix, the 3 spaced columns corresponding to the 1st column are the 1st column, the 313th column, and the 625th column respectively, and these three columns are recorded as the 1st spaced group, the 3 spaced columns corresponding to the 2nd column are the 2nd column, the 314th column, and the 626th column respectively, and these three columns are recorded as the 2nd spaced group, the 3 spaced columns corresponding to the 3rd column are the 3rd column, the 315th column, and the 627th column respectively, and these three columns are recorded as the 3rd spaced group, and so on, until the 3 spaced columns corresponding to the 1872nd column are the 1872nd column, the 2184th column, and the 2496th column respectively, and these three columns are recorded as the 1872nd spaced group; since the maximum number of columns (i.e., the 2496th column) in the 3 spaced columns corresponding to the 1872nd column is exactly the last column of the pixel matrix, there is no need to obtain the spaced columns corresponding to the 1873rd column and its subsequent columns.

[0096] Step S22a: Obtain the sum of the pixels corresponding to all pixels in each interval group, and use a preset number of interval columns in the interval group corresponding to the maximum value as each target column. For example, the sum of the pixels corresponding to all pixels in columns 1, 313, and 625 of the first interval group is calculated; the sum of the pixels corresponding to all pixels in columns 2, 314, and 626 of the second interval group is calculated; the sum of the pixels corresponding to all pixels in columns 3, 315, and 627 of the third interval group is calculated, and so on, until the sum of the pixels corresponding to all pixels in columns 1872, 2184, and 2496 of the 1872th interval group is calculated, and the three interval columns in the interval group with the largest pixel sum are used as the three target columns; at this point, the pixel density corresponding to the three target columns is the highest.

[0097] Step S23a: Based on each target column, a reconstructed column is obtained and used as the reconstructed center layer of the x-plane. Specifically, the reconstructed column is obtained by taking the average of the column numbers corresponding to each target column and used as the reconstructed center layer of the x-plane. For example, in the 904th interval group, the sum of the pixels corresponding to all pixels in columns 904, 1216, and 1528 is the largest. In this case, columns 904, 1216, and 1528 are used as the three target columns. The average of 904, 1216, and 1528 is 1216, and column 1216 is used as the reconstructed center layer of the x-plane.

[0098] When performing the automatic layer selection step on the y plane:

[0099] In one embodiment, when the preset number is one, then:

[0100] The method for obtaining the reconstructed center layer includes: traversing each column of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each column, and taking the column corresponding to the maximum value as the reconstructed center layer of the y plane.

[0101] In another embodiment, if the preset number is greater than one, then:

[0102] The method for obtaining the reconstructed central layer specifically includes the following, namely, step S21b to step S23b.

[0103] In step S21b, a preset number of interval columns corresponding to each column in the pixel matrix of the target projection image is obtained based on a preset interval value, and each of the preset number of interval columns corresponding to each column is recorded as an interval group. The preset interval value is less than half the total number of columns in the pixel matrix. The specific method is the same as the method for obtaining interval groups when the preset number of x-planes is greater than one (i.e., step S21a). The relevant details are described above and will not be repeated here.

[0104] Step S22b: Obtain the sum of pixels corresponding to all pixel points in each interval group, and use a preset number of interval columns in the interval group corresponding to the maximum value as each target column. Specifically, the method is the same as the method for obtaining each target column when the preset number is greater than one in the x-plane (i.e., Step S22a). For relevant content, please refer to the above, and it will not be elaborated here.

[0105] Step S23b: Obtain the reconstructed column based on each target column and use it as the reconstructed central layer of the y-plane. Specifically, obtain the reconstructed column by taking the average of the column numbers corresponding to each target column and use it as the reconstructed central layer of the y-plane. The specific method is the same as the method for obtaining the reconstructed central layer when the preset number is greater than one in the x-plane (Step S23a). For relevant content, please refer to the above, and it will not be elaborated here.

[0106] When performing the automatic layer selection step on the z-plane:

[0107] In one implementation, for the case where the preset number is one, then:

[0108] The method for obtaining the reconstructed central layer includes: traversing each row of the pixel point matrix of the target projection map, obtaining the sum of pixels corresponding to all pixel points in each row, and using the row corresponding to the maximum value as the reconstructed central layer of the z-plane. For example, for a pixel point matrix with 2496 columns and 3008 rows, obtain the sum of pixels corresponding to all pixel points in each row from the 1st row to the 3008th row, and use the row with the largest sum of pixels as the reconstructed central layer of the z-plane.

[0109] In another implementation, for the case where the preset number is greater than one, then:

[0110] The method for obtaining the reconstructed central layer specifically includes the following, that is, Step S21c to Step S23c.

[0111] Step S21c: Based on a preset interval value, obtain a preset number of interval rows corresponding to each row from the pixel point matrix of the target projection map, and respectively record the preset number of interval rows corresponding to each row as each interval group. The preset interval value is less than half of the total number of rows in the pixel point matrix. It should be noted that when performing this step, there is no need to obtain the preset number of interval rows corresponding to all rows in the pixel point matrix, and only the preset number of interval rows corresponding to the 1st row to the jth row (1 < j < total number of rows) needs to be obtained. Among the preset number of interval rows corresponding to the jth row, the maximum number of rows is exactly the last row of the pixel point matrix.

[0112] For example, the preset interval value is 1 / 8 of the total number of rows in the pixel matrix. For a pixel matrix with 2496 columns and 3008 rows, the preset interval value is 376. Taking the preset number of 3 as an example, in the pixel matrix, the 3 interval rows corresponding to the 1st row are the 1st row, the 377th row and the 753rd row, and these three rows are recorded as the first interval group. The 3 interval rows corresponding to the 2nd row are the 2nd row, the 378th row and the 754th row, and these three rows are recorded as the second interval group. The 3 interval rows corresponding to the 3rd row are The alternate rows are the 3rd row, the 379th row, and the 755th row, which are recorded as the 3rd interval group, and so on, until the three interval rows corresponding to the 2256th row are the 2256th row, the 2632nd row, and the 3008th row, which are recorded as the 2256th interval group; because the maximum number of rows (i.e., the 3008th row) among the three interval rows corresponding to the 2256th row happens to be the last row of the pixel matrix, there is no need to obtain the interval rows corresponding to the 2257th row and subsequent rows.

[0113] Step S22c: Obtain the sum of the pixels corresponding to all pixels in each interval group, and use a preset number of interval rows in the interval group corresponding to the maximum value as each target row. For example, the sum of the pixels corresponding to all pixels in rows 1, 377, and 753 of the first interval group is calculated; the sum of the pixels corresponding to all pixels in rows 2, 378, and 754 of the second interval group is calculated; the sum of the pixels corresponding to all pixels in rows 3, 379, and 755 of the third interval group is calculated; and so on, until the sum of the pixels corresponding to all pixels in rows 2256, 2632, and 3008 of the 2256th interval group is calculated, and the three interval rows in the interval group with the largest pixel sum are used as the three target rows; at this point, the pixel density corresponding to the three target rows is the highest.

[0114] In step S23c, a reconstructed row is obtained based on each target row and used as the reconstructed center layer of the z plane. Specifically, the reconstructed row is obtained by taking the average of the row numbers corresponding to each target row and used as the reconstructed center layer of the z plane. For example, in the 2256th interval group, the sum of the pixels corresponding to all pixels in rows 2256, 2632, and 3008 is the largest. In this case, rows 2256, 2632, and 3008 are used as the three target rows. The average of 2256, 2632, and 3008 is 2632, and row 2632 is used as the reconstructed center layer of the z plane.

[0115] In actual applications, when automatically selecting the reconstructed center layer based on the method of this embodiment, the automatic layer selection step is usually performed on one of the x-plane, y-plane and z-plane. For example, the automatic layer selection step is performed on the z-plane. Of course, it is also feasible to perform the automatic layer selection step on two or more of the three planes, which should be determined by actual needs. In addition, when performing the automatic layer selection step on two or more planes, the number of original projection images corresponding to each plane, the preset number, and even the preset interval value can be the same or different, and there are no excessive restrictions on this.

[0116] In summary, the present invention provides a method for automatically selecting a reconstruction center layer. This method obtains a target projection image based on the original projection image of the object being measured. Within the pixel matrix of the target projection image, a predetermined number of rows or columns with the highest pixel density are selected as target rows and columns. Reconstructed rows and columns are then obtained based on the predetermined number of target rows and columns, serving as the reconstruction center layer. This method not only provides sufficient reconstructed image information, thereby improving accuracy, but also eliminates manual adjustments, achieving automatic layer selection. Therefore, the present invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0117] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for automatically selecting a reconstruction center layer, characterized in that: The method comprises: Performing an automatic layer selection step on at least one of an x-plane, a y-plane, and a z-plane of a cone-beam computed tomography system, wherein the automatic layer selection step comprises: Performing rotational scanning on the object to be measured to obtain at least one original projection image, and thereby obtaining a target projection image; A preset number of target rows and columns are selected from the pixel matrix of the target projection image, and reconstructed rows and columns are obtained as the reconstructed central layer of the corresponding plane, wherein the preset number is a natural number greater than or equal to 1.

2. The method for automatically selecting a reconstruction center layer according to claim 1, characterized in that: When performing the automatic layer selection step for the x-plane: If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image; If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on the plurality of original projection images to obtain a plurality of corrected projection images; processing pixels corresponding to each pixel point in the plurality of corrected projection images to obtain target pixels corresponding to each pixel point, and thereby obtaining the target projection image; and / or, If the preset number is one, the method for obtaining the reconstructed central layer includes: traversing each column of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each column, and taking the column corresponding to the maximum value as the reconstructed central layer of the x-plane; If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval columns corresponding to each column from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval columns corresponding to each column are respectively recorded as each interval group; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval columns in the interval group corresponding to the maximum value as each target column, and then obtaining a reconstructed column based on each target column and using it as the reconstructed center layer of the x-plane.

3. The method for automatically selecting a reconstruction center layer according to claim 1, characterized in that: When performing the automatic layer selection step on the y plane: If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image; If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on each of the plurality of original projection images to obtain a plurality of corrected projection images; selecting a corrected projection image corresponding to a target rotation angle from the plurality of corrected projection images as the target projection image, wherein the target rotation angle differs from the initial rotation angle by a preset angle, and the preset angle is greater than 0° and less than 360°; and / or, If the preset number is one, the method for obtaining the reconstructed center layer includes: traversing each column of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each column, and taking the column corresponding to the maximum value as the reconstructed center layer of the y plane; If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval columns corresponding to each column from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval columns corresponding to each column are respectively recorded as interval groups; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval columns in the interval group corresponding to the maximum value as each target column, and then obtaining a reconstructed column based on each target column and using it as the reconstructed center layer of the y plane.

4. The method for automatically selecting a reconstruction center layer according to claim 1, characterized in that: When performing the automatic layer selection step on the z plane: If the number of the original projection images is one, the method for obtaining the target projection image includes: performing air correction on the original projection image to obtain a corrected projection image, and using the corrected projection image as the target projection image; If the number of the original projection images is greater than one, the method for obtaining the target projection image includes: performing air correction on the plurality of original projection images to obtain a plurality of corrected projection images; processing pixels corresponding to each pixel point in the plurality of corrected projection images to obtain target pixels corresponding to each pixel point, and thereby obtaining the target projection image; and / or, If the preset number is one, the method for obtaining the reconstructed center layer includes: traversing each row of the pixel matrix of the target projection image, obtaining the sum of pixels corresponding to all pixels in each row, and taking the row corresponding to the maximum value as the reconstructed center layer of the z plane; If the preset number is greater than one, the method for obtaining the reconstructed center layer includes: obtaining a preset number of interval rows corresponding to each row from the pixel point matrix of the target projection image based on a preset interval value, wherein the preset number of interval rows corresponding to each row are respectively recorded as each interval group; obtaining the sum of the pixels corresponding to all pixel points in each interval group, and taking the preset number of interval rows in the interval group corresponding to the maximum value as each target row, and then obtaining a reconstructed row based on each target row and using it as the reconstructed center layer of the z plane.

5. The method for automatically selecting a central layer for reconstruction according to any one of claims 2 to 4, characterized in that: In the method of obtaining the target projection map: If the number of the original projection images is one, the method for obtaining the corrected projection image includes: performing a rotation scan in the absence of a measured object to obtain an air projection image, and performing air correction on the original projection image based on the air projection image to obtain the corrected projection image, wherein the rotation angles corresponding to the air projection image and the original projection image are equal; If the number of the original projection images is greater than one, the method for obtaining several corrected projection images includes: Performing a rotation scan when there is no object to be measured to obtain a plurality of air projection images, wherein the plurality of air projection images correspond to the plurality of original projection images one by one, and the rotation angles corresponding to the corresponding air projection images and the original projection images are equal; Based on the several air projection images, air correction is performed on the several original projection images respectively to obtain several corrected projection images; or, the several air projection images are processed to obtain multiplexed projection images, and based on the multiplexed projection images, air correction is performed on the several original projection images to obtain several corrected projection images.

6. The method for automatically selecting a reconstruction center layer according to claim 5, characterized in that: The method for obtaining a multiplexed projection image comprises: processing pixels corresponding to each pixel point in a plurality of air projection images respectively, obtaining air pixels corresponding to each pixel point, and thereby obtaining the multiplexed projection image.

7. The method for automatically selecting a reconstruction center layer according to claim 5, characterized in that: When the original projection image is air-corrected based on the air projection image: the corrected projection image = -logn (original projection image / air projection image); when the original projection image is air-corrected based on the multiplexed projection image: the corrected projection image = -logn (original projection image / multiplexed projection image).

8. The method for automatically selecting a central layer for reconstruction according to any one of claims 2 to 4 and 6, characterized in that: In a method for obtaining a target projection image executed on at least one of the x-plane and the z-plane, if the number of the original projection images is greater than one, the target pixels corresponding to each pixel point in several corrected projection images are averaged to obtain the target pixels corresponding to each pixel point, and thereby obtain the target projection image; in a method for obtaining a reconstructed central layer executed on at least one of the x-plane, the y-plane, and the z-plane, if the preset number is greater than one, the reconstructed rows and columns are obtained by averaging the row and column numbers corresponding to each target row and column and used as the reconstructed central layer of the corresponding plane; in a method for obtaining a multiplexed projection image, the air pixels corresponding to each pixel point in several air projection images are averaged to obtain the air pixels corresponding to each pixel point, and thereby obtain the multiplexed projection image.

9. The method for automatically selecting a central layer for reconstruction according to any one of claims 2 to 4, characterized in that: In the method for obtaining the reconstructed center layer executed on at least one of the x-plane and the y-plane, the preset interval value is less than half of the total number of columns in the pixel matrix; in the method for obtaining the reconstructed center layer executed on the z-plane, the preset interval value is less than half of the total number of rows in the pixel matrix.

10. The method for automatically selecting a central layer for reconstruction according to claim 1, wherein: At least one original projection image is obtained by performing rotational scanning based on a cone-beam computed tomography system, wherein: If the number of the original projection images is one, then, in the method for obtaining the original projection images performed on at least one of the x-plane and the z-plane, the cone-beam computed tomography system photographs the object under test at any rotation angle to obtain the original projection images; in the method for obtaining the original projection images performed on the y-plane, the cone-beam computed tomography system rotates by a preset angle starting from the initial rotation angle and then photographs the object under test to obtain the original projection images; If the number of the original projection images is greater than one, then, in the method for obtaining the original projection images, the cone-beam computed tomography system takes the initial rotation angle as the starting point and performs rotation scanning based on the interval angle, and photographs the object under test at different rotation angles to obtain several original projection images.

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