Ray source focus position correction method and system of static CT

Abstract

The invention discloses a method and a system for correcting the focus position of a radiation source of a static CT (Computed Tomography). The method comprises the following steps: installing a test tool; acquiring a test image corresponding to each radiation source; respectively calculating the position of the test tool through each group of test images; based on the position of the test tool, preliminarily calculating a rough calculation rotation angle of each radiation source in a cylindrical coordinate system; accurately calculating an actuarial rotation angle phi 1 of each radiation source in the cylindrical coordinate system based on the roughly calculated rotation angle; calculating the eccentricity r1 and the z-direction height z1 of the radiation source based on the eccentricity of the steel ball; acquiring the position (r1, phi1, z1) of the radiation source in the cylindrical coordinate system, and comparing the position (r1, phi1, z1) with a preset position so as to acquire the position deviation of the radiation source; and performing position correction on each radiation source based on the position deviation of each radiation source. Therefore, the position deviation of the radiation source can be calculated according to the position of the test tool by collecting the test image of the test tool and cooperating with an algorithm program, and then the position correction of the radiation source is realized.

Description

Technical Field

[0001] The present invention relates to a method for correcting the focus position of a ray source of static CT, and also relates to a corresponding ray source focus position correction system, belonging to the technical field of radiation imaging. Background Art

[0002] The radiation source for static CT consists of multiple sources arranged in a circular pattern. The focal point of each source must be coplanar in the XY plane. However, due to an error of approximately ±1.5mm in the manufacturing of the source die, significant deviations in the source focus can occur after installation. This deviation affects the geometric relationship between the source, beam limiter, and detector, making static CT calibration more difficult.

[0003] The degree of overlap between the theoretical center of the X-ray source and the detector directly impacts the quality of the reconstructed image. In some cases, static CT systems may have as many as 24 X-ray sources, necessitating the alignment of each source's focus with the detector within ±1 pixel. However, since static CT requires simultaneous measurement and adjustment of the positions of multiple tubes, and the detector and tube positions are interdependent, the calibration process becomes more complex.

[0004] Given these challenges, a simple method for calibrating the focus position of the X-ray source is needed to effectively address the installation errors that occur during the adjustment of the tubes in a multi-tube system. This method must improve calibration efficiency while maintaining accuracy and ensure that the geometric relationship between all X-ray sources and detectors remains consistent even in complex optical configurations. Summary of the Invention

[0005] The primary technical problem to be solved by the present invention is to provide a method for correcting the focus position of a static CT ray source.

[0006] Another technical problem to be solved by the present invention is to provide a static CT radiation source focus position correction system.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present invention, a method for correcting the focal position of a static CT radiation source is provided, comprising the following steps:

[0009] Fix the test fixture in the detector ring of the static CT;

[0010] Controlling each radiation source on the radiation source ring to be exposed separately, so as to obtain a test image of the test fixture on the detector ring for each radiation source;

[0011] Controlling the ray source ring and the detector ring to rotate synchronously within a range of 360 degrees, so as to obtain a set of test images of the test fixture on the detector ring for each ray source;

[0012] For each ray source, based on a set of test images corresponding to the ray source, calculate the rotation angle of the test fixture in the preset cylindrical coordinate system and z-direction height z; wherein the cylindrical coordinate system is constructed with the axis direction of the detector ring as the z-direction and the intersection of the plane formed by the z-axis and the starting position of the first row of pixels of the detector ring as the coordinate point, and the cylindrical coordinate system is constructed with the direction in which the number of rows of the detector ring increases as the positive z-direction;

[0013] Based on the rotation angle of the test fixture and z-direction height z, preliminarily calculating a rough rotation angle of the ray source in the cylindrical coordinate system;

[0014] Based on the roughly calculated rotation angle of the ray source in the cylindrical coordinate system, the precise rotation angle of the ray source in the cylindrical coordinate system is accurately calculated.

[0015] Based on the rotation angle of the test fixture and z-height z, calculate the eccentricity r of the test fixture;

[0016] Based on the eccentricity r of the test fixture, calculating the eccentricity r1 and the z-direction height z1 of the ray source in the cylindrical coordinate system;

[0017] Get the position of the ray source in the cylindrical coordinate system

[0018] The position of the ray source in the cylindrical coordinate system Comparing with a preset position to obtain a position deviation of the ray source;

[0019] The position of the ray source is corrected based on the position deviation of the ray source.

[0020] Preferably, for each ray source, the rotation angle of the test fixture in the preset cylindrical coordinate system is calculated based on a set of test images corresponding to the ray source. and z-height z, specifically including:

[0021] Performing image cropping on each test image to cut off the irradiation range of the ray source;

[0022] Stitching the cut images to form a stitched image larger than a preset pixel;

[0023] Based on the stitched image, find the pixel with the largest pixel value, and crop the second image with the pixel as the center and a preset size as the radius; wherein the pixel values of the pixels outside the second image are all 0;

[0024] Based on the second image, in the cylindrical coordinate system Take the mean in the direction and find the second image Directional maximum and minimum values;

[0025] The second image The maximum and minimum values of the direction are taken as the average of the half height, and the traversal For all values in the direction, find the first range that is greater than half the height;

[0026] Based on the second image, In the first range of directions, take the mean in the z direction and find the second range that is greater than the half height;

[0027] Based on the second image, multiple spline interpolations are performed within the second range to find the highest point, and the position of the highest point is recorded as the z-direction height z of the test fixture in the preset cylindrical coordinate system;

[0028] Based on the second image, swap The operation in the direction of the axis and the z direction is performed to record the result as the rotation angle of the test fixture in the preset cylindrical coordinate system.

[0029] Preferably, the rotation angle of the test fixture is and z-direction height z, and preliminarily calculate the rough rotation angle of the ray source in the cylindrical coordinate system, specifically including:

[0030] For each ray source, calculate the time it takes for the test fixture to rotate once the ray source rotates one circle. The difference between the maximum and minimum values of the direction is recorded as

[0031] For each ray source, based on a set of test images corresponding to the ray source, calculate the test fixture The mean in the direction and remove The mean of the direction is near the center records;

[0032] As mentioned The mean of the direction is the center, and the remaining test fixtures are placed in The rotation angles in the direction are divided into two groups;

[0033] Count the difference between the maximum and minimum z-direction positions in the two groups of rotation angles respectively, and take the value with the smaller z-direction deviation, which is recorded as dz;

[0034] After performing multiple spline interpolations on the two sets of rotation angles, the data within the intersection range of the two sets of data in the z direction are integrated;

[0035] The sum of the integral results divided by dz is the ray source at A rough rotation angle in the direction.

[0036] Preferably, the rotation angle of the ray source in the cylindrical coordinate system is roughly calculated based on the rotation angle of the ray source in the cylindrical coordinate system. Specifically include:

[0037] Traverse all ray sources and assume the initial position of each ray source in the z direction as the ideal position; initially set dz = ±2mm;

[0038] For each ray source, the positions of all test fixtures of the ray source are projected onto a preset area; wherein the preset area is the tangent plane AB between the roughly calculated rotation angle and the ideal circumscribed circle of the detector; wherein OB passes through the ISO center of the static CT and is perpendicular to AB, O is the position of the ray source, A is the projection position of the tangent line between the ray source and the test work trajectory on the plane, B is the intersection point from the ray source through the ISO center to the detector position, and AB is the tangent line on the detector passing through point B;

[0039] Fit the projection results to the elliptical trajectory corresponding to the test work, and use dz = 2mm, 0mm, -2mm to calculate the difference between the three projection results and the ideal ellipse, where dz is the difference between the z-position of the projection tube and the ideal tube position;

[0040] If the z-axis center position lose is the smallest, update dz = dz / 2 and recalculate lose; otherwise, offset the ideal z position by dz and recalculate lose until dz is less than 1E-4mm.

[0041] Determine whether the center of the elliptical trajectory coincides with the projection OB of the tube position through the rotation center;

[0042] If they overlap, then As the calculated rotation angle of the ray source in the cylindrical coordinate system If they do not coincide, then the deviation between the center of the ellipse and the ideal position is pass Correction is performed and the corrected result is used as the precise rotation angle of the ray source in the cylindrical coordinate system

[0043] in, Indicates that after the update, the tube is The position in the direction; SDD is the distance from the focus of the tube to the detector; SID is the distance from the focus of the tube to the center of rotation.

[0044] Preferably, the rotation angle of the test fixture is and z-height z, calculate the eccentricity r of the test fixture, specifically including:

[0045] Repeated calculation of the rotation angle steps until

[0046] Record the length of the minor axis of the ellipse with the smallest lost in the final fitting, and substitute it into the following formula to calculate the eccentricity r of the test fixture:

[0047]

[0048] Where x represents the length of the intersection of the projected ellipse and the plane perpendicular to the z-axis passing through the center of the ellipse, and SID takes the r-direction position of the ideal tube.

[0049] Preferably, the calculating the eccentricity r1 of the ray source in the cylindrical coordinate system based on the eccentricity r of the test fixture specifically includes:

[0050] Based on the eccentricity r of the test fixture, the actual SID of each radiation source is solved by the following formula:

[0051]

[0052] Where SDD = SID + R, R is the distance from the detector ring to the rotation center.

[0053] Preferably, the test fixture includes a steel ball of preset size and a steel ball holder;

[0054] The steel ball is located in the detector ring and is offset from the ISO center of the static CT by a preset distance; the steel ball holder is installed on the static CT to support the steel ball to stay in the detector ring.

[0055] According to a second aspect of an embodiment of the present invention, there is provided a system for correcting the focus position of a ray source using the above-mentioned method for correcting the focus position of a ray source, comprising:

[0056] An image acquisition unit is configured to acquire test images of the test fixture on the detector ring; wherein the test fixture is fixed within the detector ring of a static CT system, and the radiation source ring and the detector ring rotate synchronously within a range of 360 degrees. For each radiation source, a set of test images of the test fixture on the detector ring is acquired by the image acquisition unit.

[0057] A calculation unit is connected to the image acquisition unit and has a preset algorithm to calculate the position of each ray source through the preset algorithm, thereby obtaining the position of the ray source in the preset cylindrical coordinate system.

[0058] A comparison unit connected to the calculation unit for comparing the position of the ray source in the cylindrical coordinate system The position deviation of the ray source is obtained by comparing the position deviation with the preset position, and the position of the ray source is corrected based on the position deviation of the ray source.

[0059] According to a third aspect of an embodiment of the present invention, a system for correcting the focus position of a ray source of static CT is provided, comprising a processor and a memory, wherein the processor reads a computer program in the memory to execute the above-mentioned method for correcting the focus position of a ray source.

[0060] According to a fourth aspect of an embodiment of the present invention, a computer-readable storage medium is provided, storing a computer program, and when the computer program is read, the above-mentioned method for correcting the focus position of a ray source is executed.

[0061] Compared with the prior art, the present invention has the following technical effects:

[0062] (1) Through a simple test fixture, combined with a preset algorithm program, the position deviation of the radiation source can be quickly measured and corrected. This method uses the known position of the test fixture to calculate the deviation between the actual position of the radiation source and the theoretical position, and adjusts the installation position of the radiation source based on the deviation. At the same time, based on the calculated position deviation, subsequent patient scan images can also be corrected and reconstructed, thereby ensuring the reconstruction quality of the CT image.

[0063] (2) This method is simple to implement, and the processing cost of the test fixture is low, making it suitable for large-scale application. This method can reduce the requirements for the detector installation position accuracy, and instead use the test fixture and algorithm program to perform post-calibration adjustment of the radiation source position. This method not only optimizes the calibration process of static CT, but also greatly improves the assembly efficiency of the equipment, while ensuring the accuracy and consistency of the multi-tube system under complex optical path configurations. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A schematic diagram of the installation position of the test fixture provided in an embodiment of the present invention on a static CT;

[0065] Figure 2 A schematic diagram of the installation position of the test tool on a static CT from another angle provided by an embodiment of the present invention;

[0066] Figure 3 A schematic diagram of the trajectory of the test fixture when the rack according to an embodiment of the present invention rotates one circle;

[0067] Figure 4 A flowchart of a method for correcting the focal position of a static CT radiation source provided by the first embodiment of the present invention;

[0068] Figure 5 This is a schematic diagram of the principle of accurately calculating the rotation angle in the first embodiment of the present invention;

[0069] Figure 6 This is a schematic diagram of calculating the eccentricity r1 and the z-direction height z1 of a ray source in a cylindrical coordinate system in the first embodiment of the present invention;

[0070] Figure 7 A structural diagram of a static CT radiation source focus position correction system provided by the second embodiment of the present invention;

[0071] Figure 8 This is a structural diagram of a static CT radiation source focus position correction system provided by the third embodiment of the present invention. DETAILED DESCRIPTION

[0072] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0073] Embodiments of the present invention provide a method for correcting the focus position of a static CT scan's X-ray source during installation. Using a test fixture mounted on a patient bed, an image of the test fixture is captured on a detector after X-ray exposure. An algorithm then calculates the X-ray source's positional deviation. The X-ray source's position is then corrected through a combination of algorithmic procedures and actual adjustments. This method then reconstructs the patient's scanned image based on the corrected X-ray source position, resulting in higher-quality CT reconstructed images.

[0074] Figure 1 and Figure 2 The figure shows the installation position of the test fixture on the static CT in the embodiment of the present invention. Figure 3 As shown in the figure, the detector is used as the coordinate system, and the trajectory of the test fixture is measured when the rack rotates one circle. Figure 3 It can be seen that the trajectory of the test fixture is projected as an ellipse on the plane. By measuring the shape of the ellipse, the position of the ray source can be inferred.

[0075] First embodiment

[0076] like Figure 4 As shown, the first embodiment of the present invention provides a method for correcting the focus position of a static CT radiation source, which specifically includes the following steps:

[0077] S1: Install the test tooling.

[0078] Specifically, in this embodiment, the test fixture is composed of a steel ball of a preset size and a steel ball holder. The steel ball is preferably a spherical steel ball of 4 to 5 mm, and the steel ball holder is installed on the static CT to support the steel ball to stay in the detector ring (such as Figure 1 As shown), the steel ball is offset from the ISO center of the static CT by a preset distance (for example, about 150 mm).

[0079] It can be understood that step S1 is a pre-step of the calibration method, and if the test fixture is installed in advance, step S1 can be omitted.

[0080] S2: Obtain the test image corresponding to each ray source.

[0081] It's understood that after a radiation source is exposed, the X-rays scan the steel balls, forming a test image on the detector ring. Furthermore, since the steel balls are stationary, while the radiation source and detector rings rotate slowly and synchronously throughout a 360° range, for each radiation source, a set of test images is acquired after one rotation of the source and detector rings.

[0082] Without loss of generality, 24 radiation sources will be installed on the radiation source ring of the static CT, thereby obtaining 24 sets of test images.

[0083] S3: Calculate the position of the steel ball through each set of test images.

[0084] For each ray source, the rotation angle of the steel ball in the preset cylindrical coordinate system can be calculated through a set of test images corresponding to the ray source. and z-direction height z. The cylindrical coordinate system is constructed with the axis of the detector ring as the z-direction and the intersection of the plane formed by the z-axis and the starting position of the first row of pixels of the detector ring as the coordinate point. Furthermore, the cylindrical coordinate system takes the direction of increasing rows of detector rings as the positive z-direction.

[0085] Specifically, step S3 includes S31 to S38:

[0086] S31: performing image cropping on each test image to cut out the irradiation range of the ray source;

[0087] S32: stitching the cut images to form a stitched image larger than a preset pixel; wherein the preset pixel is 10240, and in this embodiment, the default pixel of the stitched image is 10304 pixels;

[0088] S33: Based on the stitched image, find the pixel with the largest pixel value, and crop the second image with the pixel as the center and a preset size (50 pixels in this embodiment) as the radius; the pixel values of the pixels outside the second image are all 0;

[0089] S34: Based on the second image, in the cylindrical coordinate system Take the mean in the direction and find the Directional maximum and minimum values;

[0090] S35: The second image The maximum and minimum values of the direction are taken as the average of the half height, and the traversal For all values in the direction, find the first range that is greater than half the height;

[0091] S36: Based on the second image, In the first range of directions, take the mean in the z direction and find the second range that is greater than the half height;

[0092] S37: Based on the second image, perform multiple spline interpolations within the second range to find the highest point, and record the position of the highest point as the z-direction height z of the test fixture in the preset cylindrical coordinate system;

[0093] S38: Swap based on the second image Operations in the direction and z-direction to record the results as the rotation angle of the test fixture in the preset cylindrical coordinate system

[0094] It will be appreciated that steps S31-S38 above calculate the steel ball position based on a set of test images corresponding to one of the radiation sources, thereby enabling subsequent position calculations for that radiation source. Similarly, for other radiation sources, different sets of test images can be used to calculate different steel ball positions, enabling subsequent position calculations for those different radiation sources.

[0095] S4: Preliminary calculation of the rough rotation angle of each ray source in the cylindrical coordinate system.

[0096] After obtaining the steel ball position calculated for each ray source based on step S3, the rough rotation angle of the ray source in the cylindrical coordinate system can be preliminarily calculated based on the steel ball position for each ray source. The specific calculation process is as follows:

[0097] S41: Traverse all ray sources and calculate the The difference between the maximum and minimum values of the direction is recorded as

[0098] Specifically, in this embodiment, the data of the ray source that needs to be calibrated rotates one circle is used as a reference, and the test fixture is found from the data corresponding to the ray source. The maximum and minimum values of the direction, the difference between the two is taken as the corresponding It is understandable that 24 ray sources correspond to 24 different

[0099] S42: For each ray source, based on a set of test images corresponding to the ray source, calculate the test fixture The mean in the direction and remove The mean of the direction is near the center records;

[0100] S43: With the above The mean of the direction is the center, and the remaining test fixtures are placed in The rotation angles in the direction are divided into two groups;

[0101] S44: Count the difference between the maximum and minimum z-direction positions in the two groups of rotation angles respectively, and take the value with the smaller z-direction deviation, which is recorded as dz;

[0102] S45: performing multiple spline interpolations on the two sets of rotation angles respectively and integrating the data within the intersection range of the two sets of data in the z direction;

[0103] S46: Divide the sum of the integral results by dz to obtain the ray source at A rough rotation angle in the direction.

[0104] S5: Accurately calculate the rotation angle of each ray source in the cylindrical coordinate system

[0105] After the rough rotation angle of each ray source in the cylindrical coordinate system is calculated based on step S4, the rough rotation angle of each ray source in the cylindrical coordinate system is used as a reference to accurately calculate the precise rotation angle of each ray source in the cylindrical coordinate system by the following method:

[0106] Specifically, such as Figure 5 As shown, the following steps are included:

[0107] S51: Traverse all ray sources and assume the initial position of each ray source in the z direction as an ideal position; initially set dz = ±2 mm;

[0108] S52: For each ray source, project the positions of all test fixtures of the ray source to a preset area; wherein the preset area is a tangent plane AB formed by the roughly calculated rotation angle and the ideal circumscribed circle of the detector; wherein OB passes through the ISO center of the static CT and is perpendicular to AB, O is the position of the ray source, A is the projection position of the tangent line between the ray source and the test working trajectory on the plane, B is the intersection point from the ray source through the ISO center to the detector position, and AB is the tangent line on the detector passing through point B;

[0109] S53: Fit the projection results to the elliptical trajectory corresponding to the test work, and use dz = 2 mm, 0 mm, -2 mm to calculate the difference between the three projection results and the ideal ellipse, where dz is the difference between the z-direction position of the projection tube and the ideal tube position;

[0110] S54: If the z-axis center position lose is the smallest, update dz = dz / 2 and recalculate lose; otherwise, offset the ideal z position by a distance dz and recalculate lose until dz is less than 1E-4 mm, where E is the scientific notation symbol;

[0111] S55: Determine whether the center of the elliptical trajectory coincides with the projection OB of the tube position through the rotation center;

[0112] S56: If they overlap, then As the calculated rotation angle of the ray source in the cylindrical coordinate system If they do not coincide, then the deviation between the center of the ellipse and the ideal position is pass Correction is performed and the corrected result is used as the precise rotation angle of the ray source in the cylindrical coordinate system

[0113] in, Indicates that after the update, the tube is The position in the direction; SDD is the distance from the focus of the tube to the detector; SID is the distance from the focus of the tube to the center of rotation.

[0114] S6: Calculate the eccentricity r of the steel ball.

[0115] Specifically, repeatedly calculate the rotation angle steps until

[0116] Record the length of the minor axis of the ellipse with the smallest lost in the final fitting, and substitute it into the following formula to calculate the eccentricity r of the test fixture:

[0117]

[0118] Where x represents the length of the intersection of the projected ellipse and the plane perpendicular to the z-axis passing through the center of the ellipse, and SID takes the r-direction position of the ideal tube.

[0119] S7: Calculate the eccentricity r1 and the z-direction height z1 of the ray source in the cylindrical coordinate system.

[0120] Specifically, after the eccentricity r of the test fixture is calculated in step S6, the actual SID of each ray source is solved by the following formula:

[0121]

[0122] Among them, SDD=SID+R, where R is the distance from the detector ring to the rotation center.

[0123] It should be understood that the SID of each ray source has installation errors. The SID in step S6 uses the r-axis position of the ideal tube, and step S7 is the process of resolving the SID error.

[0124] And, refer to Figure 6 As shown, according to the elliptical trajectory of the test fixture, the height of the elliptical result is recorded as AB; the eccentricity of the test fixture is recorded as EF / 2; OD is recorded as SDD; EC is recorded as SID-EF / 2; the position of the ray source is recorded as Figure 6 mid AD;

[0125] The detector position at the z-height of the ray source z1 = AB + BC + CD + A;

[0126] in,

[0127] BC and CD are Figure 6 Middle space position.

[0128] S8: Obtain the position of the ray source in the cylindrical coordinate system.

[0129] Specifically, when the precise rotation angle of the ray source in the cylindrical coordinate system is calculated in step S5 After calculating the eccentricity r1 and the z-direction height z1 of the ray source in the cylindrical coordinate system in step S7, the coordinate point in the cylindrical coordinate system is That is, the position of the ray source in the cylindrical coordinate system. It can be understood that the calculated All different.

[0130] S9: Perform position correction on the ray source.

[0131] Specifically, after the position of each ray source in the cylindrical coordinate system is obtained in step S8, the position of the ray source in the cylindrical coordinate system is The position deviation of the ray source is obtained by comparing it with the preset position, and then the position of the ray source is corrected based on the position deviation of the ray source.

[0132] In this embodiment, the position of the radiation source is corrected by manual adjustment. In other embodiments, the position of the radiation source can be automatically corrected by a mechanical structure or by a compensation algorithm, which is not specifically limited here.

[0133] Second embodiment

[0134] like Figure 7 As shown, based on the above-mentioned first embodiment, the second embodiment of the present invention provides a radiation source focus position correction system for static CT, including an image acquisition unit 1, a calculation unit 2 and a comparison unit 3.

[0135] Specifically, the image acquisition unit 1 is used to acquire the test image of the test fixture on the detector ring. The calculation unit 2 is connected to the image acquisition unit 1 and has a preset algorithm. The operation logic of the preset algorithm corresponds to steps S3 to S7 in the first embodiment. Thus, for each ray source, the position calculation is performed using the preset algorithm to obtain the position of the ray source in the preset cylindrical coordinate system. The comparison unit 3 is connected to the calculation unit 2 to calculate the position of the ray source in the cylindrical coordinate system. The position deviation of the ray source is obtained by comparing it with the preset position, and then the position of the ray source is corrected based on the position deviation of the ray source.

[0136] It is understood that in this embodiment, each module unit is a functional module corresponding to each step in the first embodiment, but is not limited to this structural form. In other embodiments, the radiation source focus position correction method in the first embodiment can be implemented by combining other module structures.

[0137] Third embodiment

[0138] like Figure 8 As shown, based on the first embodiment described above, the third embodiment of the present invention provides a system for correcting the focus position of a radiation source for static CT. The system includes one or more processors 21 and a memory 22. The memory 22 is coupled to the processors 21 and is configured to store one or more programs. When the one or more programs are executed by the one or more processors 21, the one or more processors 21 implement the method for correcting the focus position of a radiation source for static CT described in the above embodiment.

[0139] The processor 21 is used to control the overall operation of the X-ray source focus position correction system to complete all or part of the steps of the above-mentioned X-ray source focus position correction method for static CT. 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 X-ray source focus position correction system. This data can include, for example, instructions for any application or method operating on the X-ray source focus position correction system, as well as data related to the application. The memory 22 can be implemented by any type of volatile or non-volatile 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 storage, flash memory, etc.

[0140] In an exemplary embodiment, the radiation source focal position correction system can be implemented as a computer chip or entity, or as a product with certain functions, to perform the above-described radiation source focal position correction method for static CT and achieve the same technical effects as the above-described method. A typical embodiment is a computer. Specifically, the computer can be, for example, 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.

[0141] 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 method for calibrating the focal position of a static CT source, as 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 system for calibrating the focal position of a static CT source, to perform the aforementioned method for calibrating the focal position of a static CT source, thereby achieving the same technical effects as those described above.

[0142] In summary, the embodiments of the present invention provide a method and system for calibrating the focus position of a static CT radiation source, which have the following beneficial effects:

[0143] (1) Through a simple test fixture, combined with a preset algorithm program, the position deviation of the radiation source can be quickly measured and corrected. This method uses the known position of the test fixture to calculate the deviation between the actual position of the radiation source and the theoretical position, and adjusts the installation position of the radiation source based on the deviation. At the same time, based on the calculated position deviation, subsequent patient scan images can also be corrected and reconstructed, thereby ensuring the reconstruction quality of the CT image.

[0144] (2) This method is simple to implement, and the processing cost of the test fixture is low, making it suitable for large-scale application. This method can reduce the requirements for the detector installation position accuracy, and instead use the test fixture and algorithm program to perform post-calibration adjustment of the radiation source position. This method not only optimizes the calibration process of static CT, but also greatly improves the assembly efficiency of the equipment, while ensuring the accuracy and consistency of the multi-tube system under complex optical path configurations.

[0145] 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.

[0146] It should be understood that the terms "upper", "lower", "horizontal", etc., indicating the orientation or position relationship, are based on the orientation or position 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.

[0147] 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.

[0148] The above describes in detail the method and system for calibrating the focal position of a static CT radiation source provided by the present invention. For those skilled in the art, any obvious modification without departing from the essence of the present invention would constitute an infringement of the present invention's patent rights and would result in corresponding legal liability.

Claims

1. A method for correcting the focal position of a static CT source, characterized in that The steps include: Fix the test fixture in the detector ring of the static CT; Controlling each radiation source on the radiation source ring to be exposed separately, so as to obtain a test image of the test fixture on the detector ring for each radiation source; Controlling the ray source ring and the detector ring to rotate synchronously within a range of 360 degrees, so as to obtain a set of test images of the test fixture on the detector ring for each ray source; For each ray source, based on a set of test images corresponding to the ray source, calculate the rotation angle of the test fixture in the preset cylindrical coordinate system and z-direction height z; wherein the cylindrical coordinate system is constructed with the axis direction of the detector ring as the z-direction and the intersection of the plane formed by the z-axis and the starting position of the first row of pixels of the detector ring as the coordinate point, and the cylindrical coordinate system is constructed with the direction in which the number of rows of the detector ring increases as the positive z-direction; Based on the rotation angle of the test fixture and z-direction height z, preliminarily calculating a rough rotation angle of the ray source in the cylindrical coordinate system; Based on the roughly calculated rotation angle of the ray source in the cylindrical coordinate system, the precise rotation angle of the ray source in the cylindrical coordinate system is accurately calculated. Based on the rotation angle of the test fixture and z-height z, calculate the eccentricity r of the test fixture; Based on the eccentricity r of the test fixture, calculating the eccentricity r1 and the z-direction height z1 of the ray source in the cylindrical coordinate system; Get the position of the ray source in the cylindrical coordinate system ; The position of the ray source in the cylindrical coordinate system Comparing with a preset position to obtain a position deviation of the ray source; The position of the ray source is corrected based on the position deviation of the ray source.

2. The method for correcting the focus position of a radiation source according to claim 1, wherein: For each ray source, based on a set of test images corresponding to the ray source, the rotation angle of the test fixture in the preset cylindrical coordinate system is calculated. and z-height z, specifically including: Performing image cropping on each test image to cut off the irradiation range of the ray source; Stitching the cut images to form a stitched image larger than a preset pixel; Based on the stitched image, find the pixel with the largest pixel value, and crop the second image with the pixel as the center and a preset size as the radius; wherein the pixel values of the pixels outside the second image are all 0; Based on the second image, in the cylindrical coordinate system Take the mean in the direction and find the second image Directional maximum and minimum values; The second image The maximum and minimum values of the direction are taken as the average of the half height, and the traversal For all values in the direction, find the first range that is greater than half the height; Based on the second image, In the first range of directions, take the mean in the z direction and find the second range that is greater than the half height; Based on the second image, multiple spline interpolations are performed within the second range to find the highest point, and the position of the highest point is recorded as the z-direction height z of the test fixture in the preset cylindrical coordinate system; Based on the second image, swap The operation in the direction of the axis and the z direction is performed to record the result as the rotation angle of the test fixture in the preset cylindrical coordinate system. .

3. The method for correcting the focus position of a radiation source according to claim 2, wherein: The rotation angle of the test fixture and z-direction height z, and preliminarily calculate the rough rotation angle of the ray source in the cylindrical coordinate system, specifically including: For each ray source, calculate the time it takes for the test fixture to rotate once the ray source rotates one circle. The difference between the maximum and minimum values of the direction is recorded as For each ray source, based on a set of test images corresponding to the ray source, calculate the test fixture The mean in the direction and remove The mean of the direction is 1 / 4d around the center records; As mentioned The mean of the direction is the center, and the remaining test fixtures are placed in The rotation angles in the direction are divided into two groups; Count the difference between the maximum and minimum z-direction positions in the two groups of rotation angles respectively, and take the value with the smaller z-direction deviation, which is recorded as dz; After performing multiple spline interpolations on the two sets of rotation angles, the data within the intersection range of the two sets of data in the z direction are integrated; The sum of the integral results divided by dz is the ray source at A rough rotation angle in the direction.

4. The method for correcting the focus position of a radiation source according to claim 3, wherein: The method comprises the steps of: accurately calculating the rotation angle of the ray source in the cylindrical coordinate system based on the roughly calculated rotation angle of the ray source in the cylindrical coordinate system; and accurately calculating the precise rotation angle of the ray source in the cylindrical coordinate system. Specifically include: Traverse all ray sources and assume the initial position of each ray source in the z direction as the ideal position; initially set dz = ±2mm; For each ray source, the positions of all test fixtures of the ray source are projected onto a preset area; wherein the preset area is the tangent plane AB between the roughly calculated rotation angle and the ideal circumscribed circle of the detector; wherein OB passes through the ISO center of the static CT and is perpendicular to AB, O is the position of the ray source, A is the projection position of the tangent line between the ray source and the test work trajectory on the plane, B is the intersection point from the ray source through the ISO center to the detector position, and AB is the tangent line on the detector passing through point B; Fit the projection results to the elliptical trajectory corresponding to the test work, and use dz = 2mm, 0mm, -2mm to calculate the difference between the three projection results and the ideal ellipse, where dz is the difference between the z-position of the projection tube and the ideal tube position; If the z-axis center position lose is the smallest, update dz = dz / 2 and recalculate lose; otherwise, offset the ideal z position by dz and recalculate lose until dz is less than 1E-4mm. Determine whether the center of the elliptical trajectory coincides with the projection OB of the tube position through the rotation center; If they overlap, then As the calculated rotation angle of the ray source in the cylindrical coordinate system If they do not coincide, then the deviation d between the center of the ellipse and the ideal position is ,pass Correction is performed and the corrected result is used as the precise rotation angle of the ray source in the cylindrical coordinate system in, Indicates that after the update, the tube is The position in the direction; SDD is the distance from the focus of the tube to the detector; SID is the distance from the focus of the tube to the center of rotation.

5. The method for correcting the focus position of a radiation source according to claim 4, wherein: The rotation angle of the test fixture and z-height z, calculate the eccentricity r of the test fixture, specifically including: Repeated calculation of the rotation angle steps until Record the length of the minor axis of the ellipse with the smallest lost in the final fitting, and substitute it into the following formula to calculate the eccentricity r of the test fixture: Where x represents the length of the intersection of the projected ellipse and the plane perpendicular to the z-axis passing through the center of the ellipse, and SID takes the r-direction position of the ideal tube.

6. The method for correcting the focus position of a ray source according to claim 5, wherein: The calculating the eccentricity r1 of the ray source in the cylindrical coordinate system based on the eccentricity r of the test fixture specifically includes: Based on the eccentricity r of the test fixture, the actual SID of each radiation source is solved by the following formula: Where SDD = SID + R, R is the distance from the detector ring to the rotation center.

7. The method for calibrating the focus position of a radiation source according to claim 1, wherein: The test fixture includes a steel ball of preset size and a steel ball holder; The steel ball is located in the detector ring and is offset from the ISO center of the static CT by a preset distance; the steel ball holder is installed on the static CT to support the steel ball to stay in the detector ring.

8. A ray source focus position correction system using the ray source focus position correction method according to any one of claims 1 to 7, characterized in that include: An image acquisition unit is configured to acquire test images of the test fixture on the detector ring; wherein the test fixture is fixed within the detector ring of a static CT system, and the radiation source ring and the detector ring rotate synchronously within a range of 360 degrees. For each radiation source, a set of test images of the test fixture on the detector ring is acquired by the image acquisition unit. A calculation unit is connected to the image acquisition unit and has a preset algorithm to calculate the position of each ray source through the preset algorithm, thereby obtaining the position of the ray source in the preset cylindrical coordinate system. A comparison unit connected to the calculation unit for comparing the position of the ray source in the cylindrical coordinate system The position deviation of the ray source is obtained by comparing it with a preset position, and then the position of the ray source is corrected based on the position deviation of the ray source.

9. A static CT radiation source focus position correction system, characterized in that The method comprises a processor and a memory, wherein the processor reads a computer program in the memory and is used to execute the method for correcting the focus position of a ray source according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is read, the method for correcting the focus position of a radiation source according to any one of claims 1 to 7 is executed.

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