CT (Computed Tomography) geometric parameter correction method and system and electronic equipment

Abstract

The invention provides a CT geometric parameter correction method and system and electronic equipment. The correction method comprises the steps that at least three first center coordinates of a ray window of a ray generator and at least three second center coordinates of a flat panel detector in the scanning process are acquired; according to the first center coordinates and / or the second center coordinates, actual geometric parameters in the scanning process are calculated; and generating a corresponding relationship between the actual geometric parameters and the projection angle so as to correct the geometric parameters for image reconstruction. Because the corresponding relation is generated based on the first center coordinate and / or the second center coordinate in the scanning process, the corresponding relation can reflect the dynamic change of the actual geometric parameters of the C-shaped arm in the scanning process, and the geometric parameters used for image reconstruction are corrected according to the corresponding relation. According to the invention, the change of geometric parameters caused by factors such as vibration or gravity center change in the scanning process of the C-shaped arm can be overcome, so that the accuracy of CT geometric parameter correction is improved.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging technology, and in particular to a correction method, system and electronic equipment for CT geometric parameters. Background Art

[0002] The imaging quality of CT is affected by geometric parameters. If the geometric parameters deviate, it may cause image blur, distortion or artifacts, affecting the accuracy of diagnosis. The current correction method of CT geometric parameters only considers the correction of fixed deviations of geometric parameters caused by deformation, installation errors and other factors of the equipment, which will lead to inaccurate correction of CT geometric parameters. Therefore, the correction method of CT geometric parameters still needs to be improved. Summary of the invention

[0003] The technical problem to be solved by the present disclosure is to overcome the defect that the prior art only considers the correction of fixed deviations of geometric parameters caused by deformation, installation errors and other factors of the equipment, which leads to inaccurate correction of CT geometric parameters, and to provide a correction method, system and electronic equipment for CT geometric parameters.

[0004] The present invention solves the above technical problems through the following technical solutions:

[0005] In a first aspect, a method for correcting CT geometric parameters is provided, wherein the method is applied to a C-shaped arm, wherein the C-shaped arm includes a ray generator and a flat panel detector; the method includes:

[0006] Acquire at least three first center coordinates of the ray window of the ray generator and at least three second center coordinates of the flat panel detector during scanning;

[0007] Calculating actual geometric parameters during scanning according to the first center coordinate and / or the second center coordinate;

[0008] A corresponding relationship between the actual geometric parameters and the projection angle is generated to correct the geometric parameters used for image reconstruction.

[0009] Optionally, calculating actual geometric parameters in the scanning process according to the first center coordinate and / or the second center coordinate includes:

[0010] Fitting a first space circle according to the first center coordinates;

[0011] Fitting a second space circle according to the second center coordinates;

[0012] The actual geometric parameters are calculated based on the first center coordinates and the first space circle and / or based on the second center coordinates and the second space circle.

[0013] Optionally, fitting a first space circle according to the first center coordinates and / or fitting a second space circle according to the second center coordinates includes:

[0014] Fitting any three of the first center coordinates into a third space circle;

[0015] Calculate the shortest first distances from the remaining first center coordinates to the edge of the third space circle, and count the first number of the first distances that are lower than the first distance threshold;

[0016] Taking the third space circle corresponding to the maximum value of the first number as the first space circle;

[0017] and / or,

[0018] Fitting any three of the second center coordinates into a fourth space circle;

[0019] Calculate the shortest second distances from the remaining second center coordinates to the fourth spatial circle edge, and count the second number of second distances below the second distance threshold;

[0020] The fourth spatial circle corresponding to the maximum value of the second number is used as the second spatial circle.

[0021] Optionally, the actual geometric parameter includes a third distance from the first center coordinate to the second center coordinate; and calculating the actual geometric parameter in the scanning process according to the first center coordinate and the second center coordinate includes:

[0022] Acquire a fourth distance from a ray source focus of the ray generator to the first center coordinate;

[0023] The third distance is calculated according to the first center coordinates, the second center coordinates and the fourth distance.

[0024] Optionally, the actual geometric parameter includes a fifth distance from the first center coordinate to the first center coordinate of the first space circle; and calculating the actual geometric parameter in the scanning process according to the first center coordinate and the first space circle includes:

[0025] Acquire a fourth distance from a ray source focus of the ray generator to the first center coordinate;

[0026] The fifth distance is calculated according to the first center coordinates, the first circle center coordinates and the fourth distance.

[0027] Optionally, the actual geometric parameter includes a first horizontal offset of an actual projection center coordinate compared to the second center coordinate, wherein the actual projection center coordinate is the intersection coordinate of an extension line of a connecting line of the first center coordinate and the first center coordinate of the first space circle and a plane of the flat panel detector;

[0028] The calculating the actual geometric parameters according to the first center coordinates and the first space circle and according to the second center coordinates and the second space circle comprises:

[0029] Calculate the actual projection center coordinates according to the first center coordinates, the second center coordinates, the first circle center coordinates, and the second circle center coordinates of the second space circle;

[0030] Calculating a horizontal direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the plane normal vector of the second space circle;

[0031] The first offset is calculated according to the actual projection center coordinates, the second center coordinates and the horizontal direction vector.

[0032] Optionally, the actual geometric parameter includes a second offset of the actual projection center coordinates in a vertical direction compared to the second center, and the actual geometric parameter is calculated according to the first center coordinates and the first space circle and according to the second center coordinates and the second space circle, including:

[0033] Calculate the vertical direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the horizontal direction vector;

[0034] The second offset is calculated according to the actual projection center coordinates, the second center coordinates and the vertical direction vector.

[0035] Optionally, before the step of generating the correspondence between the actual geometric parameters and the projection angle to correct the geometric parameters used for image reconstruction, the step includes:

[0036] Obtaining the initial center coordinates of the center of the flat panel detector;

[0037] A projection angle of the second center coordinate is calculated according to the initial center coordinate and the second center coordinate.

[0038] In a second aspect, a CT geometric parameter correction system is provided, which is applied to a C-arm, wherein the C-arm includes a ray generator and a flat-panel detector; the correction system includes a center coordinate acquisition device and a processor; the center coordinate acquisition device is used to acquire the first center coordinate of the ray window of the ray generator and the second center coordinate of the flat-panel detector; the processor is electrically connected to the center coordinate acquisition device; the processor is used to process any of the above-mentioned CT geometric parameter correction methods.

[0039] In a third aspect, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and used to run on the processor, wherein when the processor executes the computer program, the method for correcting the CT geometric parameters described in any one of the above is implemented.

[0040] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0041] The positive progressive effect of the present disclosure is that the correspondence between the actual geometric parameters and the projection angle is generated according to the first center coordinate of the ray window of the ray generator and / or the second center coordinate of the flat-panel detector during the scanning process to correct the geometric parameters used for image reconstruction. Since the correspondence is generated based on the first center coordinate and / or the second center coordinate during the scanning process, the correspondence can reflect the dynamic changes of the actual geometric parameters of the C-arm during the scanning process. Therefore, correcting the geometric parameters used for image reconstruction according to the correspondence can overcome the changes in the geometric parameters caused by factors such as vibration or change of center of gravity of the C-arm during the scanning process, thereby improving the accuracy of CT geometric parameter correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flowchart of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure;

[0043] Figure 2 A schematic diagram of the rotation of a ray generator and a flat panel detector in a method for correcting CT geometric parameters provided in Example 1 of the present disclosure;

[0044] Figure 3 A schematic diagram of a first space circle fitted by a ray generator in a method for correcting CT geometric parameters provided in Example 1 of the present disclosure;

[0045] Figure 4 A curve diagram of a third distance with respect to a projection angle of a method for correcting CT geometric parameters provided in Embodiment 1 of the present disclosure;

[0046] Figure 5A curve diagram of the fifth distance with respect to the projection angle of a method for correcting CT geometric parameters provided in Embodiment 1 of the present disclosure;

[0047] Figure 6 A curve diagram of a first offset of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure with respect to a projection angle;

[0048] Figure 7 A curve diagram of a second offset of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure with respect to a projection angle;

[0049] Figure 8 A schematic diagram of a module of a CT geometric parameter correction system provided in Embodiment 2 of the present disclosure;

[0050] Fig. 9 This is a schematic diagram of the structure of an electronic device shown in Embodiment 3 of the present disclosure. DETAILED DESCRIPTION

[0051] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0052] Prefixes such as "first" and "second" are used in the embodiments of the present disclosure only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present disclosure does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes. In addition, in the description of the present embodiment, unless otherwise specified, the meaning of "plurality" is two or more.

[0053] Example 1

[0054] In order to improve the accuracy of CT geometric parameter correction, an embodiment of the present invention provides a CT geometric parameter correction method. The correction method is applied to a C-shaped arm, and the C-shaped arm includes a ray generator and a flat panel detector. Preferably, the ray generator is an X-ray generator. Figure 1 A flowchart of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure, the correction method comprising the following steps:

[0055] Step 101: Acquire at least three first center coordinates of a ray window of a ray generator and at least three second center coordinates of a flat panel detector during a scanning process.

[0056] In one embodiment, a possible implementation method of how to obtain the first center coordinates and the second center coordinates is described below.

[0057] Step 101-1, fix the optical positioning reference frame containing the target ball array at the ray generator position and the flat-panel detector position of the C-arm respectively, install the infrared optical positioning instrument at the appropriate position on the side of the C-arm and ensure that its field of view covers the two optical positioning reference frames on the opposite side of the C-arm at the same time.

[0058] The target sphere array on the optical positioning reference frame is a group of small, reflective spheres that can reflect light from an infrared optical locator. An infrared optical locator is a device that can emit infrared light and receive reflected light. It usually contains one or more cameras to capture the light reflected by the target sphere array on the optical positioning reference to achieve positioning.

[0059] Step 101 - 2 , using an optical positioning reference frame containing a target ball array, respectively obtain the relative coordinates of the center of the flat panel detector in the flat panel detector reference frame coordinate system and the relative coordinates of the center of the X-ray generator ray window in the X-ray generator reference frame coordinate system.

[0060] During the scanning process, the coordinate transformation can be used to calculate the real-time coordinates of the center of the flat panel detector and the center of the ray window in the optical locator coordinate system. The coordinate transformation calculation formula is:

[0061]

[0062] Wherein, X is the first center coordinate or the second center coordinate of the center of the flat panel detector or the center of the ray window in the corresponding reference frame coordinate system, and Y is the first center coordinate or the second center coordinate of the center of the flat panel detector or the center of the ray window in the optical locator coordinate system (world coordinate system). It is the transformation matrix of the corresponding flat panel detector reference frame or X-ray generator reference frame in the optical locator coordinate system (world coordinate system) to transform the first center coordinate or the second center coordinate from the reference frame coordinate system to the optical locator coordinate system (world coordinate system).

[0063] In one embodiment, the first center coordinate and the second center coordinate may also be recorded as point cloud data, and calculations may be performed based on the point cloud data in subsequent processes.

[0064] Step 102: Calculate actual geometric parameters during the scanning process according to the first center coordinate and / or the second center coordinate.

[0065] Step 103: Generate a corresponding relationship between actual geometric parameters and projection angles to calibrate geometric parameters used for image reconstruction.

[0066] The corresponding relationship can be in the form of a curve graph, a table, etc. The projection angle is the rotation angle of the ray generator and the flat panel detector around their corresponding rotation axis. The rotation axis is a virtual axis. Figure 2 A schematic diagram of the rotation of a ray generator and a flat panel detector in a method for correcting CT geometric parameters provided in Example 1 of the present disclosure. Under ideal conditions, the ray generator 11 and the flat panel detector 12 rotate around the same rotation axis Y, and the rotation angle is the projection angle. However, during the actual scanning process, factors such as vibration or change in the center of gravity may cause the position of the ray generator and the flat panel detector to change, thereby causing the rotation axis to change, and thus the geometric parameters to change.

[0067] In this embodiment, a correspondence between actual geometric parameters and projection angles is generated according to the first center coordinates of the ray window of the ray generator and / or the second center coordinates of the flat-panel detector during the scanning process to correct the geometric parameters used for image reconstruction. Since the correspondence is generated based on the first center coordinates and / or the second center coordinates during the scanning process, the correspondence can reflect the dynamic changes of actual geometric parameters of the C-arm during the scanning process. Therefore, correcting the geometric parameters used for image reconstruction according to the correspondence can overcome the changes in geometric parameters caused by factors such as vibration or change of center of gravity of the C-arm during the scanning process, thereby improving the accuracy of CT geometric parameter correction.

[0068] In one embodiment, calculating the actual geometric parameters in the scanning process according to the first center coordinates includes: fitting a first space circle according to the first center coordinates, and calculating the actual geometric parameters according to the first center coordinates and the first space circle.

[0069] Take the raycaster as an example: Figure 3 A schematic diagram of the first space circle fitted by the ray generator in a method for correcting CT geometric parameters provided in Example 1 of the present disclosure, Cs is the center of the first space circle, Ps is the first center coordinate of the ray generator, and Os is the first space circle. Before being corrected, the geometric parameters used for image reconstruction have fixed values, but are regarded as a ray generator at a fixed position and a flat-panel detector at a fixed position rotating around a fixed rotation axis (the rotation axis is virtual). During the actual scanning process, the position of the ray emitter and / or the flat-panel detector may change due to factors such as vibration or change in the center of gravity. At this time, the fixed rotation axis will also change accordingly, and then the space circle formed by the ray emitter and / or the flat-panel detector rotating around the changed rotation axis will also change accordingly, that is, the rotation axis changes from the initial fixed rotation axis to the axis where Cs (the center of the first space circle) is located, so correction is required.

[0070] In this embodiment, the first spatial circle fitted according to the first center coordinates during the scanning process can be regarded as the running trajectory of the ray generator during the actual scanning process. The actual geometric parameters calculated according to the first spatial circle are the geometric parameters in the actual scanning process. The actual geometric parameters are used to correct the geometric parameters used for image reconstruction. This can overcome the changes in geometric parameters caused by factors such as vibration or change of center of gravity of the C-arm during the scanning process, thereby improving the accuracy of CT geometric parameter correction.

[0071] In one embodiment, calculating the actual geometric parameters in the scanning process according to the second center coordinates includes: fitting a second space circle according to the second center coordinates, and calculating the actual geometric parameters according to the second center coordinates and the second space circle.

[0072] In this embodiment, the second spatial circle fitted according to the second center coordinates during the scanning process can be regarded as the running trajectory of the flat-panel detector during the actual scanning process. The actual geometric parameters calculated according to the second spatial circle are the geometric parameters in the actual scanning process. The actual geometric parameters are used to correct the geometric parameters used for image reconstruction, which can overcome the changes in geometric parameters caused by factors such as vibration or change of center of gravity of the C-arm during the scanning process, thereby improving the accuracy of CT geometric parameter correction.

[0073] In one embodiment, actual geometric parameters in the scanning process are calculated based on the first center coordinates and the second center coordinates, including: fitting a first space circle based on the first center coordinates, fitting a second space circle based on the second center coordinates, and calculating the actual geometric parameters based on the first center coordinates and the first space circle and based on the second center coordinates and the second space circle.

[0074] In this embodiment, the first spatial circle fitted according to the first center coordinates during the scanning process can be regarded as the running trajectory of the ray generator during the actual scanning process, and the second spatial circle fitted according to the second center coordinates can be regarded as the running trajectory of the flat-panel detector during the actual scanning process. The actual geometric parameters calculated according to the first spatial circle and the second spatial circle are the geometric parameters in the actual scanning process. Using the actual geometric parameters to correct the geometric parameters used for image reconstruction can overcome the changes in the geometric parameters caused by factors such as vibration or change of center of gravity of the C-arm during the scanning process, thereby improving the accuracy of CT geometric parameter correction.

[0075] In one embodiment, fitting a first spatial circle according to the first center coordinates includes: fitting any three first center coordinates into a third spatial circle, calculating the shortest first distance from each of the remaining first center coordinates to the edge of the third spatial circle, and counting the first number whose first distance is lower than a first distance threshold, and taking the third spatial circle corresponding to the maximum value of the first number as the first spatial circle.

[0076] It should be noted that the remaining first center coordinates include the first center coordinates that are the same as the spatial plane where the third spatial circle is located, and the shortest first distance from this part of the first center coordinates to the third spatial circle is directly the distance from the first center coordinate to the center of the third spatial circle minus the radius of the third spatial circle; the remaining first center coordinates also include the first center coordinates that are different from the plane where the third spatial circle is located, and the calculation process of the shortest first distance from this part of the first center coordinates to the third spatial circle is:

[0077] Take a first center coordinate that is different from the spatial plane where the third spatial circle is located as an example. First, project the first center coordinate to the spatial plane where the third spatial circle is located to obtain the A projection coordinate, calculate the A distance from the A projection coordinate to the third spatial circle (that is, the distance from the projection coordinate to the center of the third spatial circle minus the radius of the third spatial circle) and the B distance from the projection coordinate to the first center coordinate. Secondly, take the A distance and the B distance as two right-angled sides and use the Pythagorean theorem to calculate the shortest distance from the first center coordinate to the third spatial circle. Take the fitting of the first spatial circle according to the first center coordinate as an example. The calculation formula is:

[0078]

[0079]

[0080]

[0081] in, is the coordinate of the center of the first space circle, The first space circle plane normal vector, is the radius of the first space circle, is the distance from the origin of the coordinate system to the circular plane of the first space circle.

[0082] Regarding how to fit the first space circle, a possible implementation method is introduced below.

[0083] The first spatial circle fitting process uses the sampling consensus algorithm (RANSAC): randomly select 3 first center coordinates from the multiple first center coordinates obtained, and fit the spatial circles where the three first center coordinates are located (it should be noted that every three first center coordinates can fit a spatial circle, and the specific number of spatial circles to be fitted can be set according to needs), calculate the first distance from each of the remaining first center coordinates to each spatial circle (that is, the Euclidean distance from each of the remaining first center coordinates to the nearest point on the spatial circle), and count the first number of the first center coordinates whose first distance is lower than the first threshold; repeat the above process, and take the spatial circle corresponding to the maximum value of the first number as the first spatial circle.

[0084] In this embodiment, the maximum value of the first number usually corresponds to the minimum average error, which means that the average distance between the fitted first space circle and each first center coordinate is the smallest. Therefore, it has better representativeness and robustness in statistics, and the actual geometric parameters calculated according to the first space circle can be more accurate.

[0085] In one embodiment, fitting a second space circle according to the second center coordinates includes: fitting any three second center coordinates into a fourth space circle, calculating the shortest second distances from the remaining second center coordinates to the edge of the fourth space circle, and counting the second numbers whose second distances are lower than the second distance threshold, and taking the fourth space circle corresponding to the maximum value of the second number as the second space circle. The process of obtaining the shortest second distance is the same as the process of obtaining the shortest first distance in the above description, and will not be described again here.

[0086] In this embodiment, the maximum value of the second number usually corresponds to the minimum average error, which means that the average distance between the fitted second space circle and each second center coordinate is the smallest. Therefore, it has better representativeness and robustness in statistics, and the actual geometric parameters calculated according to the second space circle can be more accurate.

[0087] In one embodiment, the actual geometric parameter includes a third distance from the first center coordinate to the second center coordinate; and calculating the actual geometric parameter during scanning according to the first center coordinate and the second center coordinate includes:

[0088] S1: Obtain a fourth distance from a ray source focus of a ray generator to a first center coordinate.

[0089] The distance from the ray source focus to the first center coordinate directly affects the geometric relationship of imaging, including magnification and image resolution; therefore, in order to obtain actual geometric parameters, the fourth distance from the ray source focus of the ray generator to the first center coordinate should be taken into account.

[0090] S2: Calculate a third distance according to the first center coordinate, the second center coordinate and the fourth distance.

[0091] The calculation formula is:

[0092]

[0093] in, is the third distance, is the first center coordinate, is the second center coordinate, The fourth distance.

[0094] Figure 4A curve diagram of the third distance with respect to the projection angle of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure; the abscissa is the projection angle, SDD is the third distance, and the ordinate is the actual value of the third distance.

[0095] In this embodiment, the third distance from the first center coordinate to the second center coordinate is calculated based on the actual geometric parameters in the scanning process according to the first center coordinate and the second center coordinate during the scanning process. The geometric parameters used for image reconstruction can be corrected more accurately in the subsequent process, thereby improving the imaging quality.

[0096] In one embodiment, the actual geometric parameter includes a fifth distance from the first center coordinate to the first center coordinate of the first space circle; and calculating the actual geometric parameter during the scanning process according to the first center coordinate and the first space circle includes:

[0097] S1: Obtain a fourth distance from a ray source focus of a ray generator to a first center coordinate.

[0098] The distance from the ray source focus to the first center coordinate directly affects the geometric relationship of imaging, including magnification and image resolution; therefore, in order to obtain actual geometric parameters, the fourth distance from the ray source focus of the ray generator to the first center coordinate should be taken into account.

[0099] S2: Calculate a fifth distance according to the first center coordinates, the first circle center coordinates and the fourth distance.

[0100] The calculation formula is:

[0101]

[0102] in, is the fifth distance, is the first center coordinate, is the coordinate of the first circle center, The fourth distance.

[0103] Figure 5 This is a graph of the fifth distance with respect to the projection angle of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure; the abscissa is the projection angle, SAD is the fifth distance, and the ordinate is the actual value of the fifth distance.

[0104] In this embodiment, the fifth distance from the ray source to the first center coordinate determines the geometric shape and size of the imaging. Therefore, the fifth distance from the first center coordinate to the first center coordinate of the first space circle calculated based on the first center coordinate during the scanning process and the first center coordinate can make the geometric parameters used for image reconstruction more accurate in the subsequent process, thereby improving the imaging quality.

[0105] In one embodiment, the actual geometric parameter includes a first horizontal offset of the actual projection center coordinates compared to the second center coordinates, wherein the actual projection center coordinates are the intersection coordinates of an extension line of a connection line between the first center coordinates and the first center coordinates of the first space circle and the plane of the flat panel detector;

[0106] According to the first center coordinate and the first space circle and according to the second center coordinate and the second space circle, actual geometric parameters are calculated, including:

[0107] S1: Calculate the actual projection center coordinates according to the first center coordinates, the second center coordinates, the first circle center coordinates and the second circle center coordinates of the second space circle.

[0108] The calculation formula is:

[0109]

[0110] in, is the second center coordinate, Sit for the first center, is the coordinate of the first circle center, is the coordinate of the second circle center, is the actual projection center coordinate.

[0111] S2: Calculate the horizontal direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the plane normal vector of the second space circle.

[0112] The calculation formula is:

[0113]

[0114] in, is the horizontal direction vector, is the second center coordinate, is the coordinate of the second circle center, is the plane normal vector of the second space circle.

[0115] S3: Calculate a first offset according to the actual projection center coordinates, the second center coordinates, and the horizontal direction vector.

[0116] The calculation formula is:

[0117]

[0118] in, is the actual projection center coordinate, is the second center coordinate, is the horizontal direction vector, is the first offset.

[0119] Figure 6 A curve diagram of the first offset of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure with respect to the projection angle; the horizontal axis is the projection angle, the offset in the X direction is the first offset, and the vertical axis is the actual value of the first offset.

[0120] In this embodiment, the horizontal direction vector calculated by the second center coordinate and the actual projection center coordinate during the scanning process can accurately reflect the horizontal deviation of the flat panel detector relative to the second center coordinate during the scanning process, and then the correction of the geometric parameters used for image reconstruction according to the horizontal direction vector in the subsequent process can be more accurate, thereby improving the imaging quality.

[0121] In one embodiment, the actual geometric parameter includes a second offset of the actual projection center coordinates in a vertical direction compared to the second center. The actual geometric parameter is calculated based on the first center coordinates and the first space circle and based on the second center coordinates and the second space circle, including:

[0122] S1: Calculate the vertical direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the horizontal direction vector.

[0123] The calculation formula is:

[0124]

[0125] in, is the horizontal direction vector, is the coordinate of the second circle center, is the second center coordinate, is the vertical direction vector.

[0126] S2: Calculate the second offset according to the actual projection center coordinates, the second center coordinates and the vertical direction vector.

[0127] The calculation formula is:

[0128]

[0129] in, is the actual projection center coordinate, is the second center coordinate, is the vertical direction vector, is the second offset.

[0130] Figure 7 A curve diagram of the second offset of a method for correcting CT geometric parameters provided in Example 1 of the present disclosure with respect to the projection angle; the horizontal axis is the projection angle, the offset in the Y direction is the second offset, and the vertical axis is the actual value of the second offset.

[0131] In this embodiment, the vertical direction vector calculated by the second center coordinate and the actual projection center coordinate during the scanning process can accurately reflect the deviation of the flat panel detector in the vertical direction relative to the second center coordinate during the scanning process, and thus the geometric parameters used for image reconstruction can be corrected more accurately according to the vertical direction vector in the subsequent process.

[0132] In one embodiment, before generating the correspondence between the actual geometric parameters and the projection angle to correct the geometric parameters used for image reconstruction, the method includes:

[0133] S1: Get the initial center coordinates of the flat panel detector center.

[0134] S2: Calculate the projection angle of the second center coordinate according to the initial center coordinate and the second center coordinate.

[0135] First, the zero angle reference coordinate of the flat panel detector is calculated based on the acquired initial center coordinate and the second center coordinate. The calculation formula is:

[0136]

[0137] in, is the initial center coordinate, is the center coordinate of the space circle fitted according to the second center coordinate, is the zero angle reference coordinate.

[0138] Secondly, the projection angle of the second center coordinate is calculated based on the zero-angle reference coordinate and the second center coordinate. The calculation formula is:

[0139]

[0140] in, is the second center coordinate, is the center coordinate of the space circle fitted according to the second center coordinate, is the zero angle reference coordinate, is the projection angle of the second center coordinate.

[0141] In this embodiment, since the acquired second center coordinates are three-dimensional, it is difficult to quantify the three-dimensional coordinates into a form that can be numerically calculated. Therefore, converting the second center coordinates into their corresponding two-dimensional projection angles can be easier to process and visualize, and then it is easier to analyze and understand the relationship between the second center coordinates and their corresponding geometric parameters.

[0142] Example 2

[0143] Corresponding to the aforementioned embodiment of the method for correcting CT geometric parameters, the present disclosure also provides an embodiment of a system for correcting CT geometric parameters. Figure 8 A module schematic diagram of a CT geometric parameter correction system provided in Example 2 of the present disclosure. The correction system is applied to a C-shaped arm, and the C-shaped arm includes a ray generator 11 and a flat panel detector 12; the correction system includes a center coordinate acquisition device 82 and a ray generator 11. The center coordinate acquisition device 82 is used to acquire the first center coordinate of the ray window of the ray generator 11 and the second center coordinate of the flat panel detector 12; the center coordinate acquisition device 82 is connected to the ray generator 11 and the flat panel detector 12 respectively; the processor 81 is electrically connected to the center coordinate acquisition device 82; the processor is used to process the CT geometric parameter correction method mentioned above.

[0144] As for the embodiments of the system, since they basically correspond to the method embodiments, the relevant parts can refer to the partial description of the method embodiments. The system embodiments described above are only schematic, wherein the units described as separate components may or may not be physically separated, and the components as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the disclosed solution.

[0145] Example 3

[0146] Fig. 9 This is a schematic diagram of the structure of an electronic device shown in an exemplary embodiment of the present disclosure, the electronic device includes a memory, a processor, and a computer program stored in the memory and used to run on the processor, and when the processor executes the computer program, the method for correcting the CT geometric parameters described in any of the above embodiments is implemented. Fig. 9 The electronic device 90 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present disclosure.

[0147] like Fig. 9 As shown, the electronic device 90 may be in the form of a general-purpose computing device, for example, it may be a server device. The components of the electronic device 90 may include, but are not limited to: at least one processor 81, at least one memory 92, and a bus 93 connecting different system components (including the memory 92 and the processor 81).

[0148] The bus 93 includes a data bus, an address bus, and a control bus.

[0149] The memory 92 may include a volatile memory, such as a random access memory (RAM) 921 and / or a cache memory 922 , and may further include a read only memory (ROM) 923 .

[0150] The memory 92 may also include a program tool 925 (or utility) having a set (at least one) of program modules 924, such program modules 924 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0151] The processor 81 executes various functional applications and data processing by running the computer program stored in the memory 92, such as the correction method of CT geometric parameters provided in any of the above embodiments.

[0152] The electronic device 90 may also communicate with one or more external devices 94 (e.g., keyboards, pointing devices, etc.). Such communication may be performed via an input / output (I / O) interface 95. Furthermore, the electronic device 90 may also communicate with one or more networks (e.g., local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via a network adapter 96. As shown, the network adapter 96 communicates with other modules of the electronic device 90 via a bus 93. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 90, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems, etc.

[0153] It should be noted that although several units / modules or sub-units / modules of the electronic device are mentioned in the above detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present disclosure, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided into multiple units / modules to be embodied.

[0154] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. A method for correcting CT geometric parameters, characterized in that: The correction method is applied to a C-shaped arm, the C-shaped arm includes a ray generator and a flat panel detector; the correction method includes: Acquire at least three first center coordinates of the ray window of the ray generator and at least three second center coordinates of the flat panel detector during scanning; Calculating actual geometric parameters during scanning according to the first center coordinate and / or the second center coordinate; A corresponding relationship between the actual geometric parameters and the projection angle is generated to correct the geometric parameters used for image reconstruction.

2. The calibration method according to claim 1, characterized in that: The calculating the actual geometric parameters in the scanning process according to the first center coordinate and / or the second center coordinate comprises: Fitting a first space circle according to the first center coordinates; Fitting a second space circle according to the second center coordinates; The actual geometric parameters are calculated based on the first center coordinates and the first space circle and / or based on the second center coordinates and the second space circle.

3. The calibration method according to claim 2, characterized in that: The step of fitting a first space circle according to the first center coordinates and / or fitting a second space circle according to the second center coordinates includes: Fitting any three of the first center coordinates into a third space circle; Calculate the shortest first distances from the remaining first center coordinates to the edge of the third space circle, and count the first number of the first distances that are lower than the first distance threshold; Taking the third space circle corresponding to the maximum value of the first number as the first space circle; and / or, Fitting any three of the second center coordinates into a fourth space circle; Calculate the shortest second distances from the remaining second center coordinates to the fourth spatial circle edge, and count the second number of second distances below the second distance threshold; The fourth spatial circle corresponding to the maximum value of the second number is used as the second spatial circle.

4. The calibration method according to claim 1, wherein: The actual geometric parameter includes a third distance from the first center coordinate to the second center coordinate; the actual geometric parameter in the scanning process is calculated according to the first center coordinate and the second center coordinate, including: Acquire a fourth distance from a ray source focus of the ray generator to the first center coordinate; The third distance is calculated according to the first center coordinates, the second center coordinates and the fourth distance.

5. The calibration method according to claim 2, characterized in that: The actual geometric parameter includes a fifth distance from the first center coordinate to the first center coordinate of the first space circle; and calculating the actual geometric parameter in the scanning process according to the first center coordinate and the first space circle includes: Acquire a fourth distance from a ray source focus of the ray generator to the first center coordinate; The fifth distance is calculated according to the first center coordinates, the first circle center coordinates and the fourth distance.

6. The calibration method according to claim 2, characterized in that: The actual geometric parameter includes a first horizontal offset of the actual projection center coordinates compared to the second center coordinates, wherein the actual projection center coordinates are the intersection coordinates of an extension line of a connecting line of the first center coordinates and the first center coordinates of the first space circle and the plane of the flat panel detector; The calculating the actual geometric parameters according to the first center coordinates and the first space circle and according to the second center coordinates and the second space circle comprises: Calculate the actual projection center coordinates according to the first center coordinates, the second center coordinates, the first circle center coordinates, and the second circle center coordinates of the second space circle; Calculating a horizontal direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the plane normal vector of the second space circle; The first offset is calculated according to the actual projection center coordinates, the second center coordinates and the horizontal direction vector.

7. The calibration method according to claim 6, characterized in that: The actual geometric parameter includes a second offset of the actual projection center coordinates in a vertical direction compared to the second center. The actual geometric parameter is calculated based on the first center coordinates and the first space circle and based on the second center coordinates and the second space circle, including: Calculate the vertical direction vector of the flat panel detector according to the second circle center coordinates, the second center coordinates and the horizontal direction vector; The second offset is calculated according to the actual projection center coordinates, the second center coordinates and the vertical direction vector.

8. The calibration method according to claim 2, characterized in that: Before the step of generating the corresponding relationship between the actual geometric parameters and the projection angle to correct the geometric parameters used for image reconstruction, the method includes: Obtaining the initial center coordinates of the center of the flat panel detector; A projection angle of the second center coordinate is calculated according to the initial center coordinate and the second center coordinate.

9. A CT geometric parameter correction system, characterized in that: Applied to a C-shaped arm, the C-shaped arm includes a ray generator and a flat-panel detector; the correction system includes a center coordinate acquisition device and a processor; the center coordinate acquisition device is used to acquire the first center coordinate of the ray window of the ray generator and the second center coordinate of the flat-panel detector; the processor is electrically connected to the center coordinate acquisition device; the processor is used to process the correction method of CT geometric parameters described in any one of claims 1 to 8.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and used to run on the processor, characterized in that: When the processor executes the computer program, the method for correcting CT geometric parameters according to any one of claims 1 to 8 is implemented.

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