Method for ct beam hardening correction, ct beam hardening correction device, and storage medium

Abstract

A CT beam hardening correction method, a CT beam hardening correction device and a storage medium are disclosed. The CT beam hardening correction method comprises: scanning a phantom to obtain measured projection data of the phantom; calculating estimated theoretical projection data of the phantom based on an initial estimated position of the phantom by using a theoretical projection data calculation model; calculating an actual position of the phantom based on the measured projection data and the estimated theoretical projection data of the phantom; calculating actual theoretical projection data of the phantom by using the theoretical projection data calculation model according to the actual position; calculating a beam hardening correction factor according to a relationship between expected projection data of a scanned object, measured projection data of the scanned object and the beam hardening correction factor based on the actual theoretical projection data of the phantom and the measured projection data of the phantom according to the relationship; and calculating corrected projection data of the measured object based on the measured projection data of the measured object and the beam hardening correction factor according to the relationship based on the calculated beam hardening correction factor.

Description

Technical Field

[0001] This invention relates to the field of CT equipment technology, and in particular to a projection-based CT beam hardening correction method, CT beam hardening correction equipment, and storage medium. Background Technology

[0002] Typically, X-rays are produced by bremsstrahlung and contain a broad spectral component. Because low-energy X-rays have a relatively high attenuation coefficient and are easily absorbed, they attenuate more as they pass through an object, making the X-ray spectrum "harder" after passing through it. This means that the proportion of high-energy X-rays detected by the detector increases, resulting in a smaller projected value. Due to the beam hardening effect, the attenuation coefficient along the X-ray path is not constant, and this can lead to inhomogeneities even in CT images of homogeneous objects.

[0003] To compensate for this effect, beam filters can be used to reduce low-energy X-rays and increase the average energy of the beam. However, beam filters reduce the dose and thus require higher scanning tube power output, and they also increase the average energy of the X-ray beam, affecting low-contrast detectability. Furthermore, it still does not meet the CT image quality requirements of most clinical scenarios.

[0004] Existing beam hardening correction methods for CT equipment typically employ polynomial fitting correction algorithms based on water phantoms. This is because water is a major component of the human body, and most beam hardening correction algorithms require determining polynomial factors for each system. Existing methods for determining polynomial factors mostly involve iteration or determination based on image reconstruction. Since iterative processes and / or image reconstruction are generally inefficient, the entire beam hardening correction process is quite time-consuming. Due to the time cost, it is almost impossible or unattainable to perform the entire correction process for every system.

[0005] Therefore, it is desirable to apply an efficient method to obtain these factors. Summary of the Invention

[0006] In view of this, the present invention proposes a CT beam hardening correction method, a CT beam hardening correction device and a storage medium. One of its objectives is to improve computational efficiency by calculating the beam hardening factor using only the projection data of the scanned object without image reconstruction or iteration before calculating the beam hardening factor. This allows the correction method to be used in the overall calibration process of CT equipment for each system without adding extra time.

[0007] According to one aspect of the present disclosure, a CT beam hardening correction method is provided, comprising: scanning multiple phantoms of different sizes with a scanning beam emitted from a CT device's X-ray source to obtain measurement projection data of the multiple phantoms; calculating estimated theoretical projection data of each phantom based on an initial estimated position of each phantom relative to the X-ray source using a theoretical projection data calculation model; calculating the actual position of each phantom relative to the X-ray source based on the measurement projection data and the estimated theoretical projection data of each phantom; calculating the actual theoretical projection data of each phantom based on the actual position of each phantom relative to the X-ray source using the theoretical projection data model calculation model; and obtaining the beam hardening correction. The beam hardening correction calculation model represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor. Using the beam hardening correction calculation model, the actual theoretical projection data of each phantom is used as the expected projection data of the scanned object, and the measured projection data of each phantom is used as the measured projection data of the scanned object. The beam hardening correction factor is calculated according to the relationship. Based on the calculated beam hardening correction factor, the measured projection data of the measured object is used as the measured projection data of the scanned object, and the corrected projection data of the measured object is used as the expected projection data of the scanned object. The corrected projection data of the measured object is calculated according to the relationship.

[0008] In this way, the beam hardening factor can be calculated using only the projection data of the scanning phantom without the need for image reconstruction before calculating the beam hardening factor or the reconstruction process itself, thereby improving computational efficiency. It can also be used for each system in the CT equipment integration process without adding extra time.

[0009] In one example according to this embodiment, the beam hardening correction calculation model is expressed as the following polynomial expression: ,in ;in, It is the expected projection data of the scanned object. is the measurement projection data of the scanned object, and B is the inherent attenuation value of the wedge filter. It is the beam hardening correction factor.

[0010] In this way, by pre-setting the polynomial expression of the beam hardening correction model, and then obtaining the beam hardening correction factor based on the actual theoretical projection data and the measured projection data of the phantom, compared with the traditional method of obtaining the polynomial factor by using the image obtained by scanning the homogeneous phantom and by iteratively obtaining the polynomial factor, the method of this application can avoid the image reconstruction and iterative process, and can be used for each system in the CT equipment tuning process without adding extra time.

[0011] In one example according to this embodiment, calculating the beam hardening correction factor based on the relationship includes: projecting the actual theoretical data of each phantom... As the expected projection data of the scanning object, and substituting the measured projection data P of each phantom as the measured projection data of the scanning object into the polynomial expression of the beam hardening correction calculation model, the following expression (1) is obtained: (1), where ;make Then expression (1) can be expressed as the following matrix calculation formula: Then, the least squares method is used to solve the matrix formula to calculate the beam hardening correction factor. Where k is the detector pixel index and N is the total amount of pixel data.

[0012] In this way, the beam hardening correction factor can be simplified. The computational complexity is reduced and the determination of the beam hardening correction factor is improved. The accuracy.

[0013] In one example according to this embodiment, calculating the corrected projection data of the object under test based on the relationship includes: using the measured projection data P1 of the object under test as the measured projection data of the scanning object and the corrected projection data of the object under test. Substituting the expected projection data of the scanning object into the polynomial expression of the beam hardening correction calculation model, we obtain the following expression (2): (2) Among them, Then, based on the calculated beam hardening correction factor The measured projection data P1 of the object being measured is used to calculate the corrected projection data of the object being measured using expression (2). .

[0014] In this way, the high-energy and low-energy rays in the X-ray beam emitted by the X-ray source attenuate at approximately the same rate per unit distance along the X-ray path, so that the image reconstructed from the projection data detected by the detector (array) is essentially free of beam hardening artifacts.

[0015] In one example according to this embodiment, the X-ray source is a scanning X-ray tube, and the total amount of pixel data N is equal to the number of phantoms × the number of phantom positions × the number of scanning positions of the scanning X-ray tube × the number of detector pixels.

[0016] In this way, the beam hardening correction method of this application can be made more robust and adaptable to test objects of different sizes, such as adults and children of different heights.

[0017] In one example according to this embodiment, the scanning tube scans at predetermined angular intervals, preferably π / 6.

[0018] This method can save calculation time.

[0019] In one example according to this embodiment, the measurement projection data of the multiple phantoms includes measurement projection data obtained by scanning the multiple phantom positions and multiple tube positions of the various phantoms.

[0020] In this way, the beam hardening correction method of this application can be made more robust.

[0021] In one example according to this embodiment, the theoretical projection data calculation model is represented as follows: ,in, The theoretical projection data of the phantom are represented by µ1 and µ2, which are the attenuation coefficients of the phantom shell and the uniform filler inside the shell, respectively. It is the angle between the scanning beam and the center line of the scanning beam. The path length of the ray in the shell, It is the path length of the ray through the filling material, and and It can be calculated using the following formula: , , Where D is the distance between the source of the scanning beam and the center of the phantom. It is the angle between the line connecting the X-ray source of the scanning beam and the center of the phantom, and the centerline of the scanning beam. It is the angle between the X-ray and the centerline of the scanning beam. It is the radius of the shell of the phantom. d is the radius of the phantom's filling material, and d is the perpendicular distance from the center of the phantom to the ray.

[0022] In this way, the theoretical projection data of the phantom can be determined through a simple calculation process.

[0023] In one example according to this embodiment, the initial estimated position of each phantom relative to the X-ray source of the scanning beam includes an initial estimated distance D′ between the X-ray source of the scanning beam and the center of the phantom, and an initial estimated angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. The theoretical projection data calculation model uses the initial estimated position of each phantom relative to the X-ray source of the scanning beam to calculate the estimated theoretical projection data of each phantom, including: the preset initial estimated distance D′ and the initial estimated angle. ´;The initial estimated distance D′ is taken as the distance D between the ray source of the scanning beam and the center of the phantom, and the initial estimated angle is taken as The angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. Substitute the theoretical projection data into the calculation model to calculate and estimate the theoretical projection data.

[0024] In this way, the initial estimated position of each phantom relative to the X-ray source of the scanning beam can be estimated based on existing experience, and the estimated theoretical projection data can be calculated based on the initial estimated position, which simplifies the calculation process.

[0025] In one example according to this embodiment, the actual position of each phantom relative to the X-ray source of the scanning beam includes the actual distance D″ between the X-ray source of the scanning beam and the center of the phantom, and the actual angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. The calculation of the actual position of each phantom relative to the X-ray source of the scanning beam, based on the measured projection data and the estimated theoretical projection data of each phantom, includes: minimizing the sum of the squared differences between the measured projection data and the calculated estimated theoretical projection data using the simplex multi-parameter optimization method to determine the actual distance D″ and the actual included angle. ″.

[0026] In this way, the initial estimated position of each phantom relative to the X-ray source of the scanning beam can be corrected based on the measurement projection data of each phantom, thus enabling the accurate determination of the actual position of each phantom relative to the X-ray source of the scanning beam.

[0027] In one example according to this embodiment, the actual theoretical projection data of each phantom is calculated using a theoretical projection data model calculation model based on the actual position of each phantom relative to the ray source of the scanning beam. This includes: taking the determined actual distance D″ as the distance D between the ray source of the scanning beam and the center of the phantom, and taking the actual included angle... "The angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam" Substitute the theoretical projection data into the calculation model to calculate the actual theoretical projection data of each model.

[0028] In this way, the actual theoretical projection data of the phantom can be accurately determined with reduced computational complexity.

[0029] According to another aspect of the present disclosure, a CT beam hardening correction device is provided, comprising: an estimated theoretical projection data calculation module, which calculates estimated theoretical projection data of each phantom based on an initial estimated position of each phantom relative to the X-ray source of the scanning beam using a theoretical projection data calculation model; a phantom actual position calculation module, which calculates the actual position of each phantom relative to the X-ray source of the scanning beam based on the measured projection data of each phantom obtained by scanning multiple phantoms of different sizes with a scanning beam emitted by a CT device and the estimated theoretical projection data of each phantom; and an actual theoretical projection data calculation module, which calculates the actual theoretical projection data of each phantom based on the actual position of each phantom relative to the X-ray source of the scanning beam using the theoretical projection data calculation model; and a beam hardening correction calculation model for obtaining the phantom... The system comprises three modules: a beam hardening correction calculation model, which represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor; a beam hardening correction factor calculation module, which uses the beam hardening correction calculation model to take the actual theoretical projection data of each phantom as the expected projection data of the scanned object and the measured projection data of each phantom as the measured projection data of the scanned object, and calculates the beam hardening correction factor according to the relationship; and a measured projection data correction module for the measured object, which, based on the calculated beam hardening correction factor, takes the measured projection data of the measured object as the measured projection data of the scanned object and the corrected projection data of the measured object as the expected projection data of the scanned object, and calculates the corrected projection data of the measured object according to the relationship.

[0030] In this way, the beam hardening factor can be calculated using only the projection data of the scanned object without image reconstruction before calculating the beam hardening factor and without iterative processes during the calculation, thereby improving computational efficiency. This allows this correction method to be used in the overall calibration process of CT equipment for each system without adding extra time.

[0031] According to another aspect of the present disclosure, a storage medium is provided storing a program that, when executed by a processor, causes the processor to perform the CT beam hardening correction method described above.

[0032] As can be seen from the above scheme, in this invention, the beam hardening factor can be calculated using only the projection data of the scanned object without image reconstruction before calculating the beam hardening factor and without iterative process during the calculation, thereby improving the calculation efficiency. This allows the correction method to be used for each system in the CT equipment calibration process without adding extra time. Attached Figure Description

[0033] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which will make the above and other features and advantages of the present invention more apparent to those skilled in the art. In the drawings: Figure 1 This is a flowchart of a CT beam hardening correction method provided according to an embodiment of the present disclosure.

[0034] Figure 2A A schematic diagram showing the positional relationship between the radiation source, phantom, detector, and beam is provided.

[0035] Figure 2B A schematic diagram showing the positional relationship between the phantom and the rays in the beam is shown.

[0036] Figure 3 The graphs showing the measured projection data and the estimated theoretical projection data of the phantom are presented.

[0037] Figure 4 The diagram shows the measurement projection data of 20cm and 30cm water models as the test objects, as well as the graph of the corrected projection data after correcting the measurement projection data of 20cm and 30cm water models as the test objects using the CT beam hardening correction method provided in this embodiment of the present disclosure, and the diagram of the constructed image.

[0038] Figure 5 This is a block diagram of a CT beam hardening correction device provided according to an embodiment of the present disclosure.

[0039] The accompanying figure is labeled as follows: Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments.

[0041] Figure 1 This is a flowchart of a CT beam hardening correction method provided according to an embodiment of this disclosure. Figure 1 As shown, the CT beam hardening correction method according to embodiments of this disclosure includes the following steps: Step S100: Use the scanning beam emitted by the X-ray source of the CT equipment to scan multiple phantoms of different sizes to obtain measurement projection data of multiple phantoms; The X-ray source may include a scanning X-ray tube, which may be spaced at predetermined angles α (e.g., ...). Figure 2AThe phantoms (as shown) can be scanned, for example at π / 6 angular intervals, and each phantom can be scanned at different positions relative to the X-ray source in the CT equipment. For example, the phantom can be scanned at the center of rotation or at an off-center. Therefore, the measurement projection data of multiple phantoms includes the measurement projection data obtained by scanning each phantom at multiple phantom positions and multiple scanning tube positions.

[0042] Step S101: Calculate the model based on the radiation source of each phantom relative to the scanning beam using theoretical projection data (in...). Figure 2A In this process, the X-ray source is an X-ray scanning tube, and the estimated theoretical projection data of each phantom is calculated based on the initial estimated position (represented by its focal point) of the scanning tube. The theoretical projection data calculation model is expressed as follows: , in, The theoretical projection data of the phantom are represented by µ1 and µ2, which are the attenuation coefficients of the phantom shell and the uniform filler inside the shell, respectively. It is the angle between the scanning beam and the center line of the scanning beam. The path length of the ray in the shell, It is the path length of the ray through the filling material, and according to Figure 2A and Figure 2B The positional relationship between the phantom, the ray source, and the beam is shown. and It can be calculated using the following formula: , , , Where D is the distance between the source of the scanning beam and the center of the phantom. It is the angle between the line connecting the X-ray source of the scanning beam and the center of the phantom, and the centerline of the scanning beam. It is the angle between the X-ray and the centerline of the scanning beam. It is the radius of the shell of the phantom. is the radius of the phantom's filler, and d is the perpendicular distance from the center of the phantom to the ray. Here, the phantom can be a water phantom to simulate the human body, wherein the shell of the phantom is made of PMMA material, and the filler inside the shell is water.

[0043] In this paper, the term "projection data" is used to indicate the amount of attenuation.

[0044] The initial estimated position of each phantom relative to the X-ray source of the scanning beam includes the initial estimated distance D′ between the X-ray source of the scanning beam and the center of the phantom, and the initial estimated angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. ´, and the initial estimated distance D′ and the initial estimated angle The initial settings can be configured, and the initial estimated distance D′ can be used as the distance D between the ray source of the scanning beam and the center of the phantom, as well as the initial estimated angle. The angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. Substitution formula Therefore, the perpendicular distance d from the center of the phantom to the ray is obtained, and then the obtained perpendicular distance d is substituted into the formula. The path length of the ray in the filling material is obtained. The path length of the ray in the filling material is then calculated. Substituting the obtained perpendicular distance d into the formula The conclusion is It is the angle between the scanning beam and the center line of the scanning beam. The path length of the ray in the shell Then, the expression of the model is calculated based on the theoretical projection data. Calculate and estimate theoretical projection data.

[0045] Step S102: Calculate the actual position of each phantom relative to the X-ray source of the scanning beam based on the measured projection data and estimated theoretical projection data of each phantom. Specifically, the actual position of each phantom relative to the X-ray source of the scanning beam includes the actual distance D″ between the X-ray source of the scanning beam and the center of the phantom, and the actual angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. "The simplex multi-parameter optimization method can be used to solve problems such as..." Figure 3 The actual distance D″ and the actual angle are determined by minimizing the sum of the squared differences between the measured projection data (measured attenuation) and the calculated estimated theoretical projection data (estimated theoretical attenuation) of the phantom shown. ″.

[0046] Step S103: Calculate the actual theoretical projection data of each phantom based on its actual position relative to the X-ray source of the scanning beam using the theoretical projection data model. Specifically, the actual distance D″ determined above is taken as the distance D between the ray source of the scanning beam and the center of the phantom, and the actual included angle is taken as... "The angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam" Substitute the theoretical projection data into the calculation model to calculate the actual theoretical projection data of each model.

[0047] Repeat steps S100-S103 for each of the multiple phantoms and multiple positions of each phantom (i.e., multiple positions of the phantom relative to the ray tube). In step S104, determine whether steps S100-S103 have been performed for all phantoms and all positions of the phantoms. If yes, proceed to step S105; otherwise, return to step S100.

[0048] Step S105: Obtain the beam hardening correction calculation model, which represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor.

[0049] The beam hardening correction calculation model is expressed as the following polynomial expression: ,in ; in, It is the expected projection data of the scanned object. is the measurement projection data of the scanned object, and B is the inherent attenuation value of the wedge filter. It is the beam hardening correction factor.

[0050] Step S106: Using the beam hardening correction calculation model, the actual theoretical projection data of each phantom is used as the expected projection data of the scanned object, and the measured projection data of each phantom is used as the measured projection data of the scanned object. The beam hardening correction factor is calculated according to the relationship.

[0051] Specifically, the actual theoretical projection data of each phantom As the expected projection data of the scanning object, and substituting the measured projection data P of each phantom as the measured projection data of the scanning object into the polynomial expression of the beam hardening correction calculation model, the following expression (1) is obtained: (1), where ; make Then expression (1) can be expressed as the following matrix calculation formula: , Then, the least squares method is used to solve the matrix formula to calculate the beam hardening correction factor. Where k is the detector pixel index and N is the total amount of pixel data.

[0052] For example, the X-ray source can be a scanning X-ray tube, and the total amount of pixel data N is equal to the number of phantoms × the number of phantom positions × the number of scanning positions of the scanning X-ray tube × the number of detector pixels. Preferably, the scanning X-ray tube can scan at a predetermined angle interval such as π / 6, which can save computation time.

[0053] Step S107: Based on the calculated beam hardening correction factor, the measured projection data of the object under test is used as the measured projection data of the scanning object, and the corrected projection data of the object under test is used as the expected projection data of the scanning object. The corrected projection data of the object under test is calculated according to the relationship.

[0054] Specifically, the measurement projection data P1 of the object under test is used as the measurement projection data of the scanned object and the correction projection data of the object under test. Substituting the expected projection data of the scanning object into the polynomial expression of the beam hardening correction calculation model, we obtain the following expression (2): (2) Among them, , Then, based on the calculated beam hardening correction factor The measured projection data P1 of the object being measured is used to calculate the corrected projection data of the object being measured using expression (2). .

[0055] The CT beam hardening correction method described in this application can be applied to both rotating and static scanning, and it is also applicable to various phantoms with known attenuation coefficients that are equivalent to human tissue.

[0056] Figure 4 The diagram shows measurement projection data for 20cm and 30cm water models as test objects, as well as graphs of corrected projection data after correction using the CT beam hardening correction method provided in this embodiment, and examples of constructed images. As can be seen in the constructed images, the maximum average difference between the peripheral region of interest (ROI) and the central region of interest (ROI) of the 20cm water model is less than 1 Henle unit (HU, used for CT image measurement, also known as the CT value), while the maximum average difference between the peripheral ROI and the central ROI of the 30cm water model is approximately 1 HU, clearly meeting the uniformity requirements of the CT manufacturing system.

[0057] Figure 5 It shows the relationship with Figure 1 The CT beam hardening correction method corresponds to the CT beam hardening correction device 500, which performs... Figure 1The CT beam hardening correction method includes the following steps: a theoretical projection data calculation module 501, which receives the initial estimated position of each phantom relative to the X-ray source of the scanning beam, and calculates the estimated theoretical projection data of each phantom based on the initial estimated position of each phantom relative to the X-ray source of the scanning beam using a theoretical projection data calculation model; a phantom actual position calculation module 502, which receives the measured projection data of each phantom obtained by scanning multiple phantoms of different sizes using the X-ray source emitted by the X-ray source of the CT equipment from the detector (array), and receives the estimated theoretical projection data of each phantom from the theoretical projection data calculation module 501, and calculates the actual position of each phantom relative to the X-ray source of the scanning beam based on the measured projection data and the estimated theoretical projection data of each phantom; and an actual theoretical projection data calculation module 503, which receives the actual position of each phantom relative to the X-ray source of the scanning beam from the actual position calculation module 502, and calculates the actual position of each phantom relative to the X-ray source of the scanning beam based on the measured projection data and the estimated theoretical projection data of each phantom; and an actual theoretical projection data calculation module 503, which receives the actual position of each phantom relative to the X-ray source of the scanning beam from the actual position calculation module 502, and calculates the actual position of each phantom relative to the X-ray source of the scanning beam. The actual theoretical projection data of each phantom is calculated using the theoretical projection data calculation model based on the actual position. The beam hardening correction calculation model acquisition module 504 acquires the beam hardening correction calculation model from an external or internal memory. The beam hardening correction calculation model represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor. The beam hardening correction factor calculation module 505 receives the beam hardening correction calculation model from the beam hardening correction calculation model acquisition module 504, uses the actual theoretical projection data of each phantom as the expected projection data of the scanned object, and uses the measured projection data of each phantom as the measured projection data of the scanned object, and calculates the beam hardening correction factor according to the relationship. Finally, the measured projection data correction module 506, based on the calculated beam hardening correction factor, uses the measured projection data of the measured object as the measured projection data of the scanned object and the corrected projection data of the measured object as the expected projection data of the scanned object, and calculates the corrected projection data of the measured object according to the relationship.

[0058] Furthermore, the beam hardening correction method described above in this application can be stored as a program in a computer storage medium, and the processor can read the program from the computer storage medium and execute the program to perform the beam hardening correction method described above.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A CT beam hardening correction method, characterized in that, include: The scanning beam emitted by the X-ray source of the CT equipment scans multiple phantoms of different sizes to obtain measurement projection data of the multiple phantoms; The theoretical projection data calculation model is used to calculate the estimated theoretical projection data of each phantom based on the initial estimated position of each phantom relative to the X-ray source; The actual position of each phantom relative to the radiation source is calculated based on the measured projection data of each phantom and the estimated theoretical projection data of each phantom. The actual theoretical projection data of each phantom is calculated using the theoretical projection data calculation model based on the actual position of each phantom relative to the radiation source. Obtain a beam hardening correction calculation model, which represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor; Using the aforementioned beam hardening correction calculation model, the actual theoretical projection data of each phantom is used as the expected projection data of the scanned object, and the measured projection data of each phantom is used as the measured projection data of the scanned object. The beam hardening correction factor is then calculated based on the aforementioned relationship. Based on the calculated beam hardening correction factor, the measured projection data of the object under test is used as the measured projection data of the scanned object, and the corrected projection data of the object under test is used as the expected projection data of the scanned object. The corrected projection data of the object under test is calculated according to the relationship.

2. The CT beam hardening correction method according to claim 1, characterized in that, The beam hardening correction calculation model is expressed as the following multiple expressions: ,in ; in, It is the expected projection data of the scanned object. is the measured projection data of the scanned object, and B is the inherent attenuation value of the wedge filter. is the beam hardening correction factor, where i and j are powers.

3. The CT beam hardening correction method according to claim 2, characterized in that, Calculating the beam hardening correction factor based on the aforementioned relationship includes: The actual theoretical projection data of each modulus As the expected projection data of the scanned object, and substituting the measured projection data P of each phantom as the measured projection data of the scanned object into the polynomial expression of the beam hardening correction calculation model, the following expression (1) is obtained: (1), where ; make Then the expression (1) is expressed as the following matrix calculation formula: ， Then, the least squares method is used to solve the matrix calculation formula to calculate the beam hardening correction factor. , where k is the detector pixel index and N is the total amount of pixel data.

4. The CT beam hardening correction method according to claim 3, characterized in that, Calculating the corrected projection data of the measured object based on the aforementioned relationship includes: The measurement projection data P1 of the object under test is used as the measurement projection data of the scanned object, and the correction projection data of the object under test is also used. Substituting the expected projection data of the scanned object into the polynomial expressions of the beam hardening correction calculation model, we obtain the following expression (2): (2), of which Then, based on the calculated beam hardening correction factor... The measured projection data P1 of the object under test is used to calculate the corrected projection data of the object under test using the expression (2). .

5. The CT beam hardening correction method according to claim 3 or 4, characterized in that, The X-ray source is a scanning X-ray tube, and the total amount of pixel data N is equal to the number of phantoms × the number of phantom positions × the number of scanning positions of the scanning X-ray tube × the number of detector pixels.

6. The CT beam hardening correction method according to claim 5, characterized in that, The scanning tube scans at predetermined angle intervals.

7. The CT beam hardening correction method according to claim 6, characterized in that, The measurement projection data of the multiple phantoms includes measurement projection data obtained by scanning each phantom at multiple phantom positions and multiple scanning tube positions.

8. The CT beam hardening correction method according to claim 1, characterized in that, The theoretical projection data calculation model is expressed as follows: , in, The data represents the theoretical projection data of the phantom, where µ1 and µ2 are the attenuation coefficients of the shell of the phantom and the uniform filling material within the shell, respectively. The scanning beam is at an angle relative to the center line of the scanning beam. The path length of the ray in the shell, It is the path length of the ray in the filler, and and It can be calculated using the following formula: ， ， ， Where D is the distance between the X-ray source of the scanning beam and the center of the phantom. It is the angle between the line connecting the radiation source of the scanning beam and the center of the phantom and the centerline of the scanning beam. It is the angle between the ray and the centerline of the scanning beam. It is the radius of the shell of the mold. d is the radius of the filler of the mold, and d is the perpendicular distance from the center of the mold to the ray.

9. The CT beam hardening correction method according to claim 8, characterized in that, The initial estimated position of each phantom relative to the X-ray source of the scanning beam includes the initial estimated distance D′ between the X-ray source of the scanning beam and the center of the phantom, and the initial estimated angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. The calculation model, using theoretical projection data, calculates estimated theoretical projection data for each phantom based on the initial estimated position of each phantom relative to the X-ray source of the scanning beam. This includes: The initial estimated distance D′ and the initial estimated angle are preset. ´; The initial estimated distance D′ is taken as the distance D between the ray source of the scanning beam and the center of the phantom, and the initial estimated angle is taken as... ´ is the angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam. Substitute the theoretical projection data into the calculation model to calculate the estimated theoretical projection data.

10. The CT beam hardening correction method according to claim 9, characterized in that, The actual position of each phantom relative to the X-ray source of the scanning beam includes the actual distance D″ between the X-ray source of the scanning beam and the center of the phantom, and the actual angle between the line connecting the X-ray source of the scanning beam and the center of the phantom, and the centerline of the scanning beam. "The calculation of the actual position of each phantom relative to the X-ray source of the scanning beam, based on the measured projection data of each phantom and the estimated theoretical projection data of each phantom, includes: The actual distance D″ and the actual included angle are determined by minimizing the sum of the squared differences between the measured projection data and the calculated estimated theoretical projection data using a simplex multi-parameter optimization method. ″.

11. The CT beam hardening correction method according to claim 10, characterized in that, Based on the actual position of each phantom relative to the X-ray source of the scanning beam, the theoretical projection data of each phantom is calculated using the theoretical projection data calculation model, including: The determined actual distance D″ is taken as the distance D between the ray source of the scanning beam and the center of the phantom, and the actual included angle is taken as... "The angle between the line connecting the X-ray source of the scanning beam and the center of the phantom and the centerline of the scanning beam." The actual theoretical projection data of each model is calculated by substituting the theoretical projection data into the calculation model.

12. A CT beam hardening correction device, characterized in that, include: The estimated theoretical projection data calculation module uses the theoretical projection data calculation model to calculate the estimated theoretical projection data of each phantom based on the initial estimated position of each phantom relative to the X-ray source of the scanning beam; The actual position calculation module of the phantom calculates the actual position of each phantom relative to the X-ray source of the scanning beam based on the measured projection data of each phantom obtained by scanning multiple phantoms of different sizes with a scanning beam emitted by a CT device and the estimated theoretical projection data of each phantom. The actual theoretical projection data calculation module calculates the actual theoretical projection data of each phantom based on the actual position of each phantom relative to the X-ray source of the scanning beam using the theoretical projection data calculation model. The beam hardening correction calculation model acquisition module acquires the beam hardening correction calculation model, which represents the relationship between the expected projection data of the scanned object, the measured projection data of the scanned object, and the beam hardening correction factor. The beam hardening correction factor calculation module uses the beam hardening correction calculation model to take the actual theoretical projection data of each phantom as the expected projection data of the scanned object, and takes the measured projection data of each phantom as the measured projection data of the scanned object, and calculates the beam hardening correction factor according to the relationship. as well as The measurement projection data correction module of the object under test, based on the calculated beam hardening correction factor, uses the measurement projection data of the object under test as the measurement projection data of the scanned object and the corrected projection data of the object under test as the expected projection data of the scanned object, and calculates the corrected projection data of the object under test according to the relationship.

13. A storage medium storing a program that, when executed by a processor, causes the processor to perform the CT beam hardening correction method according to any one of claims 1-11.

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