Nonlinear correction method and system for detector, and static CT device

Abstract

Disclosed are a nonlinear correction method and system for a detector, and a static CT device. The method comprises the following steps: arranging a mold body in a detection area of the static CT device, and making the rotating axis of the mold body parallel to the central axis of the static CT device; controlling a double-ring structure to rotate relative to the mold body, and collecting image data of the mold body in the relative rotation process; calculating a pixel difference value at each relative angle; drawing a fitting curve corresponding to each projection position; storing a curve coefficient of each fitting curve as a nonlinear correction coefficient of a projection image at a corresponding projection position; and on the basis of each nonlinear correction coefficient, carrying out nonlinear correction on the projection image at each projection position. In the method, polynomial fitting is carried out on a difference between a projection value at each relative angle and a projection value of a standard template to obtain a nonlinear correction table, and each projection position has enough statistical data, such that the nonlinear correction can achieve an ideal effect.

Description

A detector nonlinear correction method, correction system and static CT equipment Technical Field

[0001] The present invention relates to a nonlinear correction method for a detector, a corresponding nonlinear correction system, and a static CT device using the nonlinear correction method, belonging to the technical field of radiation imaging. Background Art

[0002] Static CT equipment faces some challenges in detector technology, which affect image quality and diagnostic accuracy. First, due to the small pixel size and high distribution density of the detector, the response linearity of some pixels is poor, which leads to inconsistency in pixel response. Second, existing photon counting detectors are mostly composed of large-area detector arrays through module splicing, and the linearity of the edge pixels of the modules is even worse due to reasons such as the manufacturing process. In addition, static CT equipment uses a multi-source system, and the energy spectra of different radiation sources are inconsistent, further increasing the inconsistency between radiation sources. These inconsistencies will cause artifacts in the reconstructed CT images, affect the uniformity of the CT values, and thus have a negative impact on image observation and result evaluation. Therefore, solving these inconsistency problems is crucial for the development and application of static CT equipment. Summary of the Invention

[0003] The primary technical problem to be solved by the present invention is to provide a nonlinear correction method for a detector.

[0004] Another technical problem to be solved by the present invention is to provide a nonlinear correction system for a detector.

[0005] Another technical problem to be solved by the present invention is to provide a static CT device that adopts the above-mentioned nonlinear correction method.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] According to a first aspect of an embodiment of the present invention, a method for nonlinear correction of a detector is provided, comprising the following steps:

[0008] A phantom is disposed in a detection area of ​​a static CT device, with the rotation axis of the phantom parallel to the central axis of the static CT device; wherein a dual-ring structure of the static CT device and the phantom are rotatable relative to each other, the dual-ring structure comprising a relatively fixed detector ring and a radiation source ring;

[0009] Controlling the dual-ring structure to rotate relative to the phantom at a preset interval angle to capture projection images of each ray source scanning the phantom at any relative angle; wherein each projection image corresponds to a fixed projection position;

[0010] Pre-correcting all projection images to obtain pre-corrected images of all ray sources at various relative angles;

[0011] For any relative angle, perform pixel averaging processing on the pre-corrected images formed by all ray sources at the relative angle during the relative rotation process to obtain the average pixel value at the relative angle;

[0012] Selecting any projection position and any relative angle, obtaining a pixel value of the pre-corrected image corresponding to the projection position at the relative angle, and comparing the pixel value of the projection position with the average pixel value corresponding to the relative angle to obtain a pixel difference value of the projection position at the relative angle; and using the pixel difference value of the projection position at the relative angle and the pixel value of the projection position at the relative angle as a set of fitting data;

[0013] Repeat the above process to obtain the fitting data of the projection position at each relative angle to form a fitting data set corresponding to the projection position;

[0014] Drawing a fitting curve corresponding to the projection position using the fitting data set;

[0015] Saving the curve coefficients of the fitting curve as nonlinear correction coefficients of the projection image at the projection position;

[0016] Based on the nonlinear correction coefficient, a nonlinear correction is performed on the projection image at the projection position.

[0017] Preferably, each of the projection positions includes a plurality of pixel areas of equal number, and the pixel value of the pre-corrected image corresponding to the projection position is a pixel value set, and the pixel value set includes a sub-pixel value corresponding to each pixel area;

[0018] The average pixel value at any relative angle is an average pixel set, and the average pixel set includes the sub-average pixel value corresponding to each pixel area at the relative angle;

[0019] wherein, for each pixel region, any relative angle is selected, and the sub-pixel value of the pixel region at the relative angle is compared with the sub-average pixel value of the pixel region at the relative angle to obtain the sub-pixel difference value of the pixel region at the relative angle; and the sub-pixel difference value of the pixel region at the relative angle and the sub-pixel value of the pixel region at the relative angle are used as a set of sub-fitting data;

[0020] Repeat the above process to obtain the sub-fitting data of the pixel area at each relative angle to form a sub-fitting data set corresponding to the pixel area;

[0021] Draw a sub-fitting curve corresponding to the pixel area using the sub-fitting data set;

[0022] The fitting curve of the projection position is composed of sub-fitting curves corresponding to each pixel area.

[0023] Preferably, the phantom is composed of a plurality of water phantoms with continuously varying sizes, and each of the water phantoms is separately arranged in the detection area of ​​the static CT device;

[0024] For any projection position, each of the water phantoms corresponds to a fitting data set for drawing a fitting curve, and the fitting curve of the projection position is drawn together by using multiple fitting data sets.

[0025] Preferably, the phantom has a plurality of changeable positions, and the plurality of changeable positions at least include above the central axis of the static CT device, below the central axis of the static CT device, to the left of the central axis of the static CT device, and to the right of the central axis of the static CT device;

[0026] For any projection position, the water phantom at each position corresponds to a fitting data set for drawing a fitting curve, and the fitting curve of the projection position is drawn together by using multiple fitting data sets.

[0027] Preferably, controlling the relative rotation of the double-ring structure and the mold body according to a preset interval angle includes:

[0028] Controlling the phantom to remain stationary and controlling the double-ring structure to rotate at a constant speed according to a preset interval angle;

[0029] Alternatively, the double-ring structure is controlled to remain stationary, and the mold body is controlled to rotate at a constant speed according to a preset interval angle.

[0030] Preferably, the process of drawing the fitting curve is as follows:

[0031] Select any relative angle, use the pixel value of the pre-corrected image of the projection position at the relative angle as the x-coordinate; and use the pixel difference of the projection position at the relative angle as the y-coordinate, and mark a scattered point in the plane coordinate system;

[0032] Repeat the above process until all scattered points are marked;

[0033] With x as the independent variable and y as the dependent variable, a polynomial fitting is performed on the marked scattered points to draw the fitting curve.

[0034] Preferably, the pre-correction includes at least background correction, air correction and scattering correction.

[0035] Preferably, the relative rotation angle between the double-ring structure and the mold body is at least 90°.

[0036] According to a second aspect of an embodiment of the present invention, a nonlinear correction system for a detector is provided, comprising a processor and a memory, wherein the processor reads a computer program in the memory to execute the above-mentioned nonlinear correction method.

[0037] According to a third aspect of an embodiment of the present invention, a static CT device is provided, which uses the above-mentioned nonlinear correction method to perform image correction.

[0038] Compared with the prior art, the present invention has the following technical effects:

[0039] 1. The dual-ring structure of the static CT device can rotate relative to the phantom. This allows for image acquisition at regular intervals during scanning of the phantom at each position, ensuring that several radiation sources capture images of the phantom at each relative angle. This ensures that the standard template at each relative angle is an ideal template.

[0040] 2. A polynomial fit is performed based on the difference between the projection values ​​at each relative angle and the standard template projection values ​​to generate a nonlinear correction table. Furthermore, since sufficient statistical data is available at each relative angle, the nonlinear correction can achieve ideal results.

[0041] 3. Scanning with phantoms of different sizes at multiple locations can ensure that each projection position has sufficient data for polynomial fitting and obtain the nonlinear characteristics of each projection position. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1 is a flow chart of a nonlinear correction method provided by a first embodiment of the present invention;

[0043] FIG2 is a schematic diagram of the first embodiment of the present invention, in which the double-ring structure and the mold body are not rotating relative to each other;

[0044] FIG3 is a schematic diagram of the first embodiment of the present invention, in which the double-ring structure and the mold body are rotated 10° relative to each other;

[0045] FIG4 is a schematic diagram of the first embodiment of the present invention, in which the double-ring structure and the mold body are rotated 180° relative to each other;

[0046] FIG5 is a flow chart of a nonlinear correction method provided by a second embodiment of the present invention;

[0047] FIG6 is a flow chart of a nonlinear correction method provided by a third embodiment of the present invention;

[0048] FIG7 is a flow chart of a nonlinear correction method provided by a fourth embodiment of the present invention;

[0049] FIG8 is a structural diagram of a nonlinear correction system provided by a fifth embodiment of the present invention. DETAILED DESCRIPTION

[0050] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] The core technical concept of the embodiments of the present invention lies in the relative rotation of the dual-ring structure of the static CT device and the mounted phantom. This allows for image acquisition at regular intervals during scanning of the phantom at each relative angle, ensuring that several radiation sources capture images of the phantom at each relative angle. This ensures that the standard template for each relative angle is a relatively ideal template. Finally, a polynomial fit is performed based on the difference between the projection values ​​at each relative angle and the projection values ​​of the standard template to generate a nonlinear correction table. Because sufficient statistical data is available at each relative angle, the nonlinear correction achieves ideal results.

[0052] First embodiment

[0053] As shown in FIG1 , a nonlinear correction method for a detector provided by the first embodiment of the present invention specifically includes steps S1 to S7:

[0054] S1: A phantom is placed in a detection area of ​​a static CT device, and a rotation axis of the phantom is parallel to a central axis of the static CT device.

[0055] Specifically, as shown in FIG2 , only the dual-ring structure 10 of a static CT device is shown. The dual-ring structure 10 is composed of a relatively fixed detector ring 11 and a radiation source ring 12. The rotation axis of the detector ring 11 is the central axis of the static CT device. The phantom 20 is preferably a cylindrical water phantom, but the shape and type of the phantom 20 are not limited. The phantom 20 is disposed within the annular region of the detector 11. Furthermore, the rotation axis of the phantom 20 is parallel to the central axis of the static CT device. Thus, radiation emitted by the radiation source ring 12 can scan the phantom 20 and form an image on the detector ring 11. It will be understood that in this embodiment, there are no strict requirements for the placement of the phantom 20; it only needs to be approximately parallel to the central axis of the static CT device. The optimal position is when the rotation axis of the phantom 20 coincides with the central axis of the static CT device, but other positions are also acceptable.

[0056] In addition, in this embodiment, the dual-ring structure 10 and the phantom 20 can rotate relative to each other, so that when scanning the phantom 20 at each position, images can be collected at intervals of a certain angle. It is understood that the relative rotation of the dual-ring structure 10 and the phantom 20 can be achieved by the following methods:

[0057] The first method is that the mold body 20 is stationary, and the double-ring structure 10 rotates at a constant speed according to a preset interval angle (for example, 1°).

[0058] The second method is that the double-ring structure 10 is stationary, and the mold body 20 rotates at a constant speed according to a preset interval angle (for example, 1°).

[0059] Of course, in another embodiment, the double-ring structure 10 and the mold body 20 may both rotate to rotate together by the preset interval angle (eg, 1°).

[0060] In addition, to ensure that there is sufficient data for subsequent polynomial fitting (described in detail below), in this embodiment, the relative rotation angle between the dual-ring structure 10 and the model 20 is at least 90°, preferably 90° to 180°, and can exceed 180°. In principle, the more angles the better, so that the statistical quantity is larger, but the amount of data to be processed is also relatively large.

[0061] S2: collecting image data of the phantom 20 during the relative rotation process.

[0062] Specifically, the dual-ring structure 10 and the phantom 20 are controlled to rotate relative to each other at a preset interval angle to capture the projection image of each radiation source scanning the phantom 10 at any relative angle. Since the positions of the detector ring 11 and the radiation source ring 12 are relatively fixed, each radiation source corresponds to a fixed projection position. Furthermore, in this embodiment, each projection position includes a plurality of pixel areas of equal number (i.e., the projection image is composed of a plurality of pixel blocks, and the number of pixel blocks is equal).

[0063] For ease of understanding, in this embodiment, as shown in Figures 2 to 4, the relative rotation angle between the dual-ring structure 10 and the phantom 20 is 180°, the preset interval angle is 1°, and there are 8 ray sources 120 on the ray source ring 12, corresponding to 8 projection positions 110 on the detector ring 11, and each projection position 110 corresponds to 10 pixel areas. An example is given for explanation.

[0064] It is understood that for every 1° of relative rotation between the dual-ring structure 10 and the phantom 20, all radiation sources on the radiation source ring 12 (i.e., 8 radiation sources) will scan the phantom 10 and form a set of projection images (8 projection images) on the detector ring 11. Therefore, when the dual-ring structure 10 and the phantom 20 rotate 180° relative to each other, a total of 180 sets of projection images need to be collected during the relative rotation of the dual-ring structure 10 and the phantom 20. Accordingly, for each radiation source, 180 projection images need to be collected during the relative rotation of the dual-ring structure 10 and the phantom 20.

[0065] S3: Pre-correct all projection images to obtain pre-corrected images of all ray sources at various relative angles.

[0066] Specifically, the pre-correction includes all correction processes except nonlinear correction, such as background correction, air correction, and scatter correction, etc. The specific correction method can be adaptively selected according to needs and is not specifically limited here.

[0067] It is understandable that, in this embodiment, if 180 sets of projection images are acquired based on step S2, all of the 180 sets of projection images need to be pre-corrected.

[0068] S4: Calculate the average pixel value at each relative angle.

[0069] Specifically, it includes steps S41 to S43:

[0070] S41: Select any relative angle.

[0071] For example, if the relative angle is selected as 1°, it means that the double-ring structure 10 and the mold body 20 are rotated relative to each other by 1°; if the relative angle is selected as 2°, it means that the double-ring structure 10 and the mold body 20 are rotated relative to each other by 2°.

[0072] S42: performing pixel average processing on the pre-corrected images formed by all the ray sources at the relative angle during the relative rotation process to obtain an average pixel value at the relative angle.

[0073] Specifically, using Figure 2 as a reference, let's define the radiation source marked 120 as radiation source 1, and number the other seven radiation sources 2 through 8 in a counterclockwise direction. If a relative angle of 1° is selected, then during a 180° relative rotation of the dual-ring structure 10 and the phantom 20, a total of four radiation sources numbered 1 through 4 are imaged at 1°.

[0074] Therefore, by averaging the pre-corrected images formed by the four ray sources numbered 1 to 4 at 1°, we can obtain the average pixel value at 1°. Furthermore, it should be understood that since a pre-corrected image has 10 pixels, the average pixel value here refers to an average pixel set, which includes 10 sub-average pixel values ​​corresponding to the 10 pixel regions.

[0075] S43: Repeat the above steps S41 to S42 until the average pixel values ​​at all relative angles are obtained.

[0076] S5: Draw the fitting curve corresponding to each projection position.

[0077] Specifically, it includes steps S51 to S56:

[0078] S51: Select any projection position.

[0079] It can be understood that, in this embodiment, based on the fact that the number of ray sources is 8, corresponding to 8 projection positions, one projection position needs to be selected from the 8 projection positions to draw a fitting curve for the projection position.

[0080] Furthermore, it can be understood that, since the projection position in this embodiment corresponds to 10 pixel areas, in fact, drawing a fitting curve for the projection position is to draw sub-fitting curves for the 10 pixel areas respectively, and the 10 sub-fitting curves together constitute the fitting curve of the projection position.

[0081] S52: Select any relative angle and obtain pixel values ​​of the pre-corrected image corresponding to the projection position at the relative angle.

[0082] Specifically, after the projection position is determined based on step S51, the corresponding ray source can be determined through the projection position. Then, based on the data in step S2, the projection image of the ray source at all relative angles (i.e., 180 relative angles) can be obtained, and then the 180 pixel values ​​corresponding to the projection position can be obtained.

[0083] It can be understood that, since the projected image has 10 pixel blocks, the pixel value corresponding to the projection position here is a pixel value set, and the pixel value set includes 10 sub-pixel values ​​corresponding to the 10 pixel blocks respectively.

[0084] S53: Obtain the pixel difference value of the projection position at the relative angle.

[0085] Specifically, after obtaining the pixel values ​​of the projection position at the relative angle (i.e., the sub-pixel values ​​of the 10 pixel blocks) in step S52, the sub-pixel values ​​of the 10 pixel blocks are respectively compared with the corresponding sub-average pixel values ​​(see step S42) to obtain 10 sub-pixel difference values ​​of the 10 pixel blocks at the relative angle. These 10 sub-pixel difference values ​​together constitute the pixel difference value of the projection position at the relative angle.

[0086] Therefore, for a pixel area at the projection position, after a relative angle is selected, the sub-pixel value of the pixel area at the relative angle and the sub-pixel difference of the pixel area at the relative angle are used as a set of sub-fitting data. A projection position corresponds to 10 sets of sub-fitting data at a relative angle.

[0087] S54: Repeat the above steps S52 to S53 to obtain fitting data of the projection position at each relative angle to form a fitting data set corresponding to the projection position.

[0088] It is understood that, in one embodiment of the present invention, the relative rotation angle between the dual-ring structure and the phantom is 180 degrees, with each rotation interval being 1°. Therefore, for each projection position, a total of 180 fitting data points at these relative angles must be collected to form a fitting data set corresponding to that projection position. Furthermore, it is understood that the fitting data set corresponding to that projection position is composed of 10 sub-fitting data sets corresponding to 10 pixel regions.

[0089] S55: Draw a fitting curve corresponding to the projection position.

[0090] Specifically, it includes steps S551 to S552:

[0091] S531: Standard scatter.

[0092] Specifically, an arbitrary relative angle (eg, 1°) is selected, and the pixel value of the pre-corrected image at the projection position of 1° is used as the x-coordinate. The x-coordinate here includes 10 coordinate values, corresponding to the x-coordinates of 10 pixel areas respectively.

[0093] The pixel difference of the projection position at 1° is used as the y coordinate. The y coordinate here includes 10 coordinate values, corresponding to the y coordinates of 10 pixel areas respectively.

[0094] For each pixel area of ​​the projection position, mark a scattered point in the plane coordinate system;

[0095] Repeat the above process until all scattered points are labeled.

[0096] It is understandable that when the relative angle changes, the x-coordinate and the y-coordinate will also change accordingly. Therefore, for any pixel area of ​​the projection position, 180 scattered points will be marked in the plane coordinate system.

[0097] S552: Polynomial fitting.

[0098] Specifically, for each pixel area of ​​the projection position, the sub-pixel value of the pixel area is used as the independent variable x, and the sub-pixel difference of the pixel area is used as the dependent variable y, and a polynomial fitting is performed on the 180 marked scattered points to form a sub-fitting curve corresponding to the pixel area.

[0099] After the polynomial fitting of 10 pixel areas is completed in sequence, 10 sub-fitting curves are formed, which together constitute the fitting curve of the projection position.

[0100] S56: Repeat the above steps S51 to S55 to obtain the fitting curve of each projection position.

[0101] It can be understood that, in this embodiment, since there are 8 projection positions and each projection position corresponds to 10 pixel areas, it is necessary to form 8*10=80 sub-fitting curves.

[0102] S6: Save the curve coefficient of each fitting curve as a nonlinear correction coefficient of the projection image at the corresponding projection position.

[0103] It can be understood that, in this embodiment, a total of 80 curve coefficients of sub-fitting curves need to be saved, thereby forming 80 nonlinear correction coefficients corresponding to 80 pixel areas.

[0104] S7: Based on the nonlinear correction coefficients, nonlinear correction is performed on the projection image at each projection position.

[0105] Specifically, a nonlinear correction coefficient corresponding to a pixel area at each projection position and a pixel value corresponding to each pixel area are calculated to obtain a pixel difference, and then pixel subtraction is performed to complete the nonlinear correction of a pixel area.

[0106] After the nonlinear correction of all pixel areas is completed, the nonlinear correction of the projection image at each projection position can be achieved.

[0107] Second embodiment

[0108] As shown in Figure 5 , based on the first embodiment, the second embodiment of the present invention further provides a detector nonlinearity correction method. Compared with the first embodiment, the difference between this embodiment and the first embodiment is that the number of phantoms 20 is different.

[0109] Specifically, in this embodiment, the phantom 20 is composed of multiple water phantoms of continuously varying sizes, each of which is individually positioned within the detection area of ​​a static CT device. It will be appreciated that, in this embodiment, for any projection position, a fitting data set can be obtained using each water phantom. Therefore, before performing polynomial fitting, each water phantom must be positioned within the detection area of ​​the static CT device to obtain n fitting data sets, where n is the number of water phantoms.

[0110] Therefore, using multiple water phantoms with continuously changing sizes can increase the amount of data during polynomial fitting, thereby improving fitting accuracy and enhancing the effect of nonlinear correction.

[0111] Except for the above differences, the remaining steps of this embodiment are the same as those of the first embodiment and are not described again here.

[0112] Third embodiment

[0113] As shown in Figure 6 , based on the first embodiment, the second embodiment of the present invention further provides a method for correcting nonlinearity of a detector. Compared with the first embodiment, the difference of this embodiment is that the position of the phantom 20 is variable.

[0114] Specifically, in this embodiment, the phantom has multiple variable positions, wherein the multiple variable positions include at least above the central axis of the static CT device, below the central axis of the static CT device, to the left of the central axis of the static CT device, and to the right of the central axis of the static CT device. Of course, it can also be the upper left, lower left, upper right, and lower right positions of the central axis of the static CT device, and can be adaptively set according to needs.

[0115] It can be understood that for any projection position, each variable position corresponds to a fitting data set. Therefore, before performing polynomial fitting, the water phantom needs to be adjusted to different positions to obtain m fitting data sets, where m is the number of variable positions of the phantom.

[0116] Therefore, using a position-variable phantom can increase the amount of data during polynomial fitting, thereby improving fitting accuracy and enhancing the effect of nonlinear correction.

[0117] Except for the above differences, the remaining steps of this embodiment are the same as those of the first embodiment and are not described again here.

[0118] Fourth embodiment

[0119] As shown in Figure 7 , based on the first embodiment, the second embodiment of the present invention further provides a detector nonlinearity correction method. Compared with the first embodiment, the difference of this embodiment is that the number of phantoms 20 is different and the positions are variable.

[0120] In this embodiment, the phantom 20 is composed of n water phantoms of continuously varying size, each with m variable positions. Thus, before polynomial fitting, m*n fitting data sets can be obtained, further improving fitting accuracy and the effectiveness of nonlinear correction.

[0121] Except for the above differences, the remaining steps of this embodiment are the same as those of the first embodiment and are not described again here.

[0122] Fifth embodiment

[0123] As shown in Figure 8 , based on the aforementioned nonlinear correction method, the present invention further provides a nonlinear correction system for a detector. This nonlinear correction system includes one or more processors 21 and a memory 22. The memory 22 is coupled to the processor 21 and is configured to store one or more programs. When executed by the processor 21, the processor 21 implements the nonlinear correction method described in the aforementioned embodiment.

[0124] The processor 21 is used to control the overall operation of the nonlinear correction system to complete all or part of the steps of the nonlinear correction method described above. The processor 21 can be a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processing (DSP) chip, etc. The memory 22 is used to store various types of data to support the operation of the nonlinear correction system. Such data may include, for example, instructions for any application or method operating on the nonlinear correction system, as well as application-related data. The memory 22 can be implemented by any type of volatile or nonvolatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, etc.

[0125] In an exemplary embodiment, the nonlinear correction system described above can be implemented as a computer chip or entity, or as a product with certain functions, to perform the above-described detector nonlinear correction method and achieve the same technical effects as the above-described method. A typical embodiment is a computer. Specifically, the computer can be a personal computer, a laptop computer, an in-vehicle human-computer interaction device, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0126] In another exemplary embodiment, the present invention further provides a computer-readable storage medium comprising program instructions, which, when executed by a processor, implement the steps of the detector nonlinearity correction method described in any of the aforementioned embodiments. For example, the computer-readable storage medium may be the aforementioned memory comprising the program instructions, which may be executed by a processor of a nonlinearity correction system to perform the aforementioned detector nonlinearity correction method and achieve the same technical effects as the aforementioned method.

[0127] Sixth embodiment

[0128] Based on the first to fourth embodiments described above, the sixth embodiment of the present invention further provides a static CT device that uses any one of the nonlinear correction methods described in the first to fourth embodiments to perform image correction.

[0129] It should be noted that the above embodiments are merely examples, and the technical solutions of the various embodiments may be combined and are all within the scope of protection of the present invention.

[0130] It should be understood that the terms "thickness", "up", "down", "horizontal", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0131] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0132] The above describes in detail the detector nonlinearity correction method, correction system, and static CT device provided by the present invention. Any obvious modification made by a person skilled in the art without departing from the essence of the present invention would constitute an infringement of the patent rights of the present invention and would result in the corresponding legal liability.

Claims

1. A non-linear correction method for a detector, characterized in that It includes the following steps: Set a phantom in the detection area of the static CT device, and make the rotation axis of the phantom parallel to the central axis of the static CT device; wherein, the double-ring structure of the static CT device and the phantom can rotate relative to each other, and the double-ring structure is composed of a relatively fixed detector ring and a radiation source ring; Control the relative rotation of the double-ring structure and the phantom at a preset interval angle to collect projection images after each radiation source scans the phantom at any relative angle; wherein, each projection image corresponds to a fixed projection position; Perform pre-correction on all projection images to respectively obtain pre-corrected images of all radiation sources at each relative angle; For any relative angle, perform pixel mean processing on the pre-corrected images formed by all radiation sources at this relative angle during the relative rotation process to obtain the average pixel value at this relative angle; Select any one projection position and any one relative angle, obtain the pixel value of the pre-corrected image corresponding to this projection position at this relative angle, and compare the pixel value of this projection position with the average pixel value corresponding to this relative angle to obtain the pixel difference of this projection position at this relative angle; and, use the pixel difference of this projection position at this relative angle and the pixel value of this projection position at this relative angle as a set of fitting data; Repeat the above process to obtain the fitting data of this projection position at each relative angle, and form a fitting data set corresponding to this projection position; Use the fitting data set to draw a fitting curve corresponding to this projection position; Save the curve coefficient of the fitting curve as the non-linear correction coefficient of the projection image at this projection position; Based on the non-linear correction coefficient, perform non-linear correction on the projection image at this projection position.

2. The non-linear correction method according to claim 1, wherein: Each of the projection positions includes a plurality of pixel regions with equal numbers, the pixel value of the pre-corrected image corresponding to the projection position is a set of pixel values, and the set of pixel values includes sub-pixel values corresponding to each pixel region; The average pixel value at any relative angle is an average pixel set, and the average pixel set includes sub-average pixel values corresponding to each pixel region at this relative angle; Wherein, for each pixel region, select any one relative angle, compare the sub-pixel value of this pixel region at this relative angle with the sub-average pixel value of this pixel region at this relative angle to obtain the sub-pixel difference of this pixel region at this relative angle; and, use the sub-pixel difference of this pixel region at this relative angle and the sub-pixel value of this pixel region at this relative angle as a set of sub-fitting data; Repeat the above process to obtain the sub-fitting data of this pixel region at each relative angle, and form a sub-fitting data set corresponding to this pixel region; Use the sub-fitting data set to draw a sub-fitting curve corresponding to this pixel region; The fitting curve of the projection position is jointly composed of sub-fitting curves corresponding to each pixel region.

3. The non-linear correction method according to claim 1, wherein: The phantom is composed of a plurality of water phantoms with continuously varying sizes, and each of the water phantoms is separately arranged in the detection area of the static CT device; For any projection position, each of the water phantoms corresponds to a fitting data set for drawing a fitting curve, and the fitting curves at this projection position are jointly drawn through a plurality of the fitting data sets.

4. The non-linear correction method according to claim 1, wherein: The phantom has a plurality of varying positions, and the plurality of varying positions at least include above the central axis of the static CT device, below the central axis of the static CT device, to the left of the central axis of the static CT device, and to the right of the central axis of the static CT device; For any projection position, each of the water phantoms at each position corresponds to a fitting data set for drawing a fitting curve, and the fitting curves at this projection position are jointly drawn through a plurality of the fitting data sets.

5. The non-linear correction method according to claim 1, wherein The controlling the relative rotation of the double-ring structure and the phantom at a preset interval angle includes: Controlling the phantom to be stationary and controlling the double-ring structure to rotate uniformly at a preset interval angle; Or, controlling the double-ring structure to be stationary and controlling the phantom to rotate uniformly at a preset interval angle.

6. The non-linear correction method according to claim 1, characterized in that The process of drawing the fitting curve is as follows: Select any relative angle, take the pixel value of the pre-corrected image at this relative angle of the projection position as the x coordinate; and take the pixel difference value at this relative angle of the projection position as the y coordinate, and mark a scatter point in the plane coordinate system; Repeat the above process until all scatter points are marked; Using x as the independent variable and y as the dependent variable, perform polynomial fitting on the marked scatter points, thereby drawing the fitting curve.

7. The non-linear correction method according to claim 1, wherein: The pre-correction at least includes: background correction, air correction, and scatter correction.

8. The non-linear correction method according to claim 1, wherein: The relative rotation angle between the double-ring structure and the phantom is at least 90°.

9. A non-linear correction system for a detector, characterized in that It includes a processor and a memory, and the processor reads the computer program in the memory for executing the non-linear correction method according to any one of claims 1 to 8.

10. A static CT device, characterized in that Perform image correction using the non-linear correction method according to any one of claims 1 to 8.

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