Method and device for calibrating tube position of CT system

Abstract

The present invention discloses a method and device for calibrating the position of a tube in a CT system, and relates to the field of CT system scanning technology. The method includes: obtaining projection data of a shielding piece projected onto a detector when the frame rotates; calculating the projection center of gravity of the shielding piece window on the detector, and calculating the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector through the projection center of gravity at different exposure angles; establishing a conversion relationship between the three-dimensional coordinate system of the shielding piece and the two-dimensional coordinate system of the detector, solving the conversion relationship parameters, i.e., the projection coordinates of the tube focus in the two-dimensional coordinate system of the detector, through the correspondence between the size of the shielding piece and the projection data, and further solving the calibration amount for calibration. The phantom of the present invention is simple to manufacture, and a single scan can realize the simultaneous calculation of the calibration amounts in the X and Z directions. It is applicable to all frame-mounted CT systems, avoids the limitations of a cumbersome calibration process and the need for multiple adjustments, and is simple to implement in practice and low in cost.

Description

Technical Field

[0001] The present invention relates to the field of CT scanning technology, and in particular to a method and device for calibrating the position of a tube of a CT system. Background Art

[0002] CT systems have been widely used in fields such as medical diagnosis and industrial inspection. As one of the important components in the CT system, the tube's position accuracy directly affects the X-ray projection path, which in turn affects the clarity of the CT image and the accuracy of the diagnosis. Therefore, accurate calibration of the tube position is crucial to ensuring CT image quality and the precise operation of the CT system.

[0003] In existing technologies, it is often necessary to calibrate the X and Z directions of the tube position separately, and this usually requires the use of one or more phantoms. The acquisition process usually involves multiple adjustments, multiple scans, and manual intervention, resulting in a cumbersome calibration process and low accuracy. In addition, methods that can simultaneously calibrate the tube in both the X and Z directions usually require multiple scans with a phantom of a specific geometric structure. Although such methods avoid the limitation of separate calibration in the X and Z directions, they also have the limitations of complex and high production costs of the phantom, and require the phantom to be placed at the center of rotation of the slip ring, which is difficult to achieve in practice. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, the present invention provides a method and device for calibrating the tube position of a CT system to solve the problems in the prior art such as cumbersome calibration process, complex phantom manufacturing and difficulty in actual operation.

[0005] In a first aspect, an embodiment of the present invention provides a method for calibrating a CT system tube position, comprising:

[0006] Acquire projection data of a horizontally placed shielding sheet projected onto the detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows;

[0007] Calculate the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculate the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles;

[0008] According to the conversion relationship between the three-dimensional coordinate system of the shielding piece and the two-dimensional coordinate system of the detector, and the corresponding relationship between the size of the shielding piece and the projection data, the projection coordinates of the focus of the tube in the two-dimensional coordinate system of the detector are solved;

[0009] According to the projection coordinates of the rotation center and the focus of the tube in the two-dimensional coordinate system of the detector, calibration information is generated to calibrate the position of the tube.

[0010] Furthermore, it also includes:

[0011] The focus of the tube is the coordinate origin and the horizontal direction is Axis and frame rotation axis are Axis and horizontal plane perpendicular to Axis, establish the three-dimensional coordinate system of the tube focus;

[0012] The upper left corner of the occlusion piece is the coordinate origin and the plane where the occlusion piece is located is The perpendicular line between the plane and the shielding piece is Y Axis, establish the three-dimensional coordinate system of the shielding piece;

[0013] The detector's two-dimensional coordinate system is established with the detector's upper left corner as the coordinate origin and the detector's plane as the coordinate plane.

[0014] The two-dimensional coordinate system of the two-dimensional projection image is established with the projection of the tube focus on the detector plane as the coordinate origin and the plane where the detector is located as the coordinate plane.

[0015] Furthermore, it also includes:

[0016] Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shielding piece:

[0017]

[0018] in, 、 、 is the three-dimensional coordinate of any point in the three-dimensional coordinate system of the tube focus, 、 、 is the corresponding coordinate of any point in the three-dimensional coordinate system of the shielding piece, is the rotation matrix, is the translation matrix.

[0019] Furthermore, it also includes:

[0020] Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projection image:

[0021]

[0022] in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the two-dimensional coordinate system of the projection image, is the distance from the tube focus to the detector.

[0023] Furthermore, it also includes:

[0024] Obtain the transformation relationship matrix between the two-dimensional coordinate system of the projection image and the two-dimensional coordinate system of the detector:

[0025]

[0026] in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the detector two-dimensional coordinate system, 、 is the two-dimensional coordinate of the origin of the projected image two-dimensional coordinate system in the detector two-dimensional coordinate system, 、 They represent the actual size of a single pixel in the detector's two-dimensional coordinate system in the X and Z directions, respectively.

[0027] Furthermore, it also includes:

[0028] Get the transformation matrix between the three-dimensional coordinate system of the shield and the two-dimensional coordinate system of the detector:

[0029]

[0030] According to the above formula, calculate the projection coordinates of the tube focus in the detector's two-dimensional coordinate system 、 .

[0031] Furthermore, the tube position is calibrated according to the following formula:

[0032]

[0033] in, 、 Respectively represent the calibration amount of the tube position in the X direction and the Z direction, 、 Represents the projection coordinates of the rotation center in the detector's two-dimensional coordinate system.

[0034] In a second aspect, an embodiment of the present invention provides a device for calibrating a tube position of a CT system, comprising:

[0035] A first module is configured to obtain projection data of a horizontally placed shielding sheet projected onto the detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows;

[0036] The second module is configured to calculate the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculate the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles;

[0037] The third module is configured to solve the projection coordinates of the focus of the tube in the two-dimensional coordinate system of the detector based on the conversion relationship between the three-dimensional coordinate system of the shielding piece and the two-dimensional coordinate system of the detector, and the correspondence between the size of the shielding piece and the projection data;

[0038] The fourth module is configured to generate calibration information to calibrate the tube position according to the projection coordinates of the rotation center and the tube focus in the two-dimensional coordinate system of the detector.

[0039] In a third aspect, an embodiment of the present invention provides an electronic device, including:

[0040] one or more processors;

[0041] a storage device for storing one or more programs;

[0042] When the one or more programs are executed by the one or more processors, the one or more processors implement a method for calibrating the position of a CT system tube as described in any one of the first aspects.

[0043] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for calibrating the position of a tube of a CT system as described in any one of the first aspects is implemented.

[0044] The present invention provides a method and device for calibrating the tube position of a CT system. The method obtains projection data of a shielding window on a detector at different exposure angles, establishes a conversion relationship between the shielding window's three-dimensional coordinate system and the detector's two-dimensional coordinate system, and solves the tube focus projection coordinates and further solves the tube position calibration value based on multiple sets of corresponding points between the shielding window centers and the shielding window projection gravity centers. By simply placing the shielding window horizontally, rather than at the rotation center, a single scan can simultaneously calculate the calibration values in the X and Z directions. The method is applicable to all gantry-mounted CT systems and avoids the limitations of difficult phantom placement, cumbersome calibration processes, and the need for multiple adjustments. In addition, the shielding window phantom used in the present invention is simple to manufacture and reusable, saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0046] Figure 1 This is a flow chart of a method for calibrating the position of a CT system tube provided by one embodiment of the present application;

[0047] Figure 2 This is a schematic diagram of a shielding sheet for a method for calibrating the position of a CT system tube provided by an embodiment of the present application;

[0048] Figure 3 This is a schematic diagram of establishing a coordinate system for a method for calibrating the position of a CT system tube provided by one embodiment of the present application;

[0049] Figure 4 This is a schematic diagram of the conversion relationship between the three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projection image in a method for calibrating the position of a CT system tube provided by one embodiment of the present application;

[0050] Figure 5 This is a schematic diagram of the conversion relationship between the two-dimensional coordinate system of the projection image and the two-dimensional coordinate system of the detector in a method for calibrating the position of the tube of a CT system provided by one embodiment of the present application;

[0051] Figure 6 This is a schematic structural diagram of a device for calibrating the position of a CT system tube provided by one embodiment of the present application;

[0052] Figure 7 An electronic device is provided in one embodiment of the present application. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0054] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0055] It should be understood that although the terms first, second, third, etc. may be used to describe the acquisition modules in the embodiments of the present invention, the acquisition modules should not be limited to these terms. These terms are only used to distinguish the acquisition modules from each other.

[0056] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0057] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should be understood that when an element is referred to as being formed "on" or "under" another element, it can be formed not only directly "on" or "under" the other element, but also indirectly "on" or "under" the other element through an intermediate element.

[0058] See also Figure 1 An embodiment of the present invention provides a method for calibrating a CT system tube position, comprising:

[0059] Step S101, obtaining projection data of a horizontally placed shielding sheet projected onto a detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows;

[0060] Specifically, a shielding sheet with multiple hollow windows is used as a model, referring to Figure 2 The shielding sheet used in this embodiment contains 9 hollow windows, which are arranged regularly. The window positions can be known through the actual size of the shielding sheet. Preferably, the shielding sheet is made of ordinary metal. The shielding sheet is placed horizontally in the scanning field of view of the CT system. The frame rotates one circle, and the hollow windows of the shielding sheet form projections on the detector to collect projection data under different exposure angles.

[0061] Step S102, calculating the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculating the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles;

[0062] Specifically, the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector are calculated by the projection data of the hollow window on the shielding sheet at different angles. For example, taking the central window on the shielding sheet as an example, the centroid coordinates of the projection area of the central window on the detector at different exposure angles are calculated, and the X-direction coordinate and the Z-direction coordinate of the centroid coordinate are separated. If the projection area of the central window at each exposure angle is complete, the X-direction coordinate and the Z-direction coordinate of the centroid of the projection area of the central window at different exposure angles constitute a complete sine curve, and the center of the sine curve is the average of the X-direction coordinate and the Z-direction coordinate. The center coordinate of the obtained sine curve is also the projection coordinate of the rotation center in the two-dimensional coordinate system of the detector. If there is an incomplete projection area through the window, the exposure angle and the symmetric angle of the exposure angle are removed before further calculating the projection coordinates of the rotation center.

[0063] Step S103, calculating the projection coordinates of the tube focus in the detector's two-dimensional coordinate system based on the conversion relationship between the shield's three-dimensional coordinate system and the detector's two-dimensional coordinate system, and the corresponding relationship between the shield's size and the projection data;

[0064] Specifically, refer to Figure 3 , with the focus of the tube as the coordinate origin and the horizontal direction as Axis and frame rotation axis are Axis and horizontal plane perpendicular to Axis, establish the three-dimensional coordinate system of the tube focus, the unit is millimeter, the three-dimensional coordinate system of the tube focus rotates with the rotation of the tube focus, for example, the tube focus is the coordinate origin , horizontal direction is Axis and frame rotation axis are Axis and horizontal plane perpendicular to axis;

[0065] The upper left corner of the occlusion piece is the coordinate origin and the plane where the occlusion piece is located is The perpendicular line between the plane and the shielding piece is Y Axis, establish the three-dimensional coordinate system of the shielding piece, the unit is millimeter, for example, the upper left corner of the shielding piece is the coordinate origin , the plane where the shielding piece is located is The perpendicular line between the plane and the shielding piece is axis;

[0066] With the upper left corner of the detector as the coordinate origin and the plane where the detector is located as the coordinate plane, a two-dimensional coordinate system of the detector is established. The unit is pixel. For example, the upper left corner of the detector is the coordinate origin. , the plane where the detector is located is the coordinate plane ;

[0067] The projection of the focus of the tube on the detector plane is used as the coordinate origin and the plane where the detector is located is used as the coordinate plane to establish a two-dimensional coordinate system for the two-dimensional projection image. The unit is millimeter. For example, the projection of the focus of the tube on the detector plane is used as the coordinate origin. , the plane where the detector is located is the coordinate plane .

[0068] Based on the conversion relationship between the above coordinate systems and the correspondence between the actual size of the shielding sheet and the projection data, the projection coordinates of the tube focus in the detector's two-dimensional coordinate system are solved, specifically including:

[0069] The three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shield are transformed by rotation and translation. Let any point in the three-dimensional coordinate system of the tube focus be P. The three-dimensional coordinates of point P in the three-dimensional coordinate system of the tube focus are , the three-dimensional coordinates of point P in the three-dimensional coordinate system of the occlusion piece are , then the transformation relationship between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shield can be expressed by the following formula:

[0070]

[0071] Its matrix form is:

[0072]

[0073] in, is the rotation matrix, which can be expressed as follows:

[0074]

[0075] 、 、 is the rotation component of the transformation relationship between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shield;

[0076] is the translation matrix, which can be expressed as follows:

[0077]

[0078] 、 、 is the translation component of the transformation relationship between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shield.

[0079] The three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projected image are transformed through perspective projection. Figure 4 , let the corresponding point of point P projected on the detector plane be ,point The coordinates in the two-dimensional coordinate system of the projected image are , set point P to the three-dimensional coordinate system of the tube focus The foot of the plane is point B, and point B to The foot of the perpendicular axis is point A, point The foot of the perpendicular to the X-axis in the two-dimensional coordinate system of the projected image is point C, then:

[0080]

[0081] in 、 、 、 is the distance SDD from the tube focus to the detector, 、 ,

[0082] Therefore, the conversion relationship between the three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projection image can be expressed as follows:

[0083]

[0084] Its matrix form is:

[0085]

[0086] The two-dimensional coordinate system of the projected image and the two-dimensional coordinate system of the detector are both based on the detector plane. The only difference is the origin of the coordinates and the unit of measurement. The conversion is performed by translation. Figure 5 , let the origin of the detector's two-dimensional coordinate system be ,point The coordinates in the detector's two-dimensional coordinate system are , the coordinate origin of the projected image two-dimensional coordinate system The coordinates in the detector's two-dimensional coordinate system are , then the transformation relationship between the detector two-dimensional coordinate system and the projection image two-dimensional coordinate system can be expressed as follows:

[0087]

[0088] Its matrix form is:

[0089]

[0090] in, 、 Respectively represent the actual size of a single pixel in the X and Z directions in the detector's two-dimensional coordinate system, in millimeters;

[0091] By combining the above transformation relationship matrices, we can obtain the transformation relationship matrix between the three-dimensional coordinate system of the shielding plate and the two-dimensional coordinate system of the detector, which is expressed by the following formula:

[0092]

[0093] From step S101, it can be seen that the coordinates of the center of the window on the shielding sheet in the shielding sheet three-dimensional coordinate system can be obtained by The coordinates of the projection center of the window on the shielding piece on the detector in the two-dimensional coordinate system of the detector can be expressed as Indicates that, are all known and form a set of corresponding points, is the Y-direction coordinate of the window center in the three-dimensional coordinate system of the tube focus, which is a non-zero constant. Since the homogeneous coordinate system used in the above transformation relationship has scale invariance, The value does not affect the parameter solution of the above conversion relationship. The value is 1. The LM (Levenberg-Marquardt) algorithm is used to iteratively solve multiple sets of corresponding points under multiple exposure angles to obtain the unknown parameters of the conversion relationship between the 3D coordinate system of the mask and the 2D coordinate system of the detector. 、 , The origin of the two-dimensional coordinate system of the projected image The coordinates in the detector's two-dimensional coordinate system, and the origin of the projected image's two-dimensional coordinate system is the projection of the tube focus on the detector's two-dimensional coordinate system, so That is, the projection coordinates of the tube focus in the two-dimensional coordinate system of the detector.

[0094] Step S104 , generating calibration information based on the projection coordinates of the rotation center and the focus of the tube in the two-dimensional coordinate system of the detector to calibrate the position of the tube.

[0095] Specifically, the projection coordinates of the rotation center and the focus of the tube in the two-dimensional coordinate system of the detector are obtained through steps S102 and S103, and the tube position calibration amount is expressed by the following formula:

[0096]

[0097] in, 、 Respectively represent the calibration amount of the tube position in the X direction and the Z direction, 、 represents the projection coordinates of the rotation center in the detector's two-dimensional coordinate system,

[0098] For example, the U direction of the detector two-dimensional coordinate system is the same as the X direction of the projection image two-dimensional coordinate system, and the V direction of the detector two-dimensional coordinate system is the same as the Z direction of the projection image two-dimensional coordinate system. 、 That is, they respectively represent the calibration amounts of the tube position in the U direction and the V direction in the two-dimensional coordinate system of the detector.

[0099] Adjust the mechanical position of the tube according to the calibration amount. In actual operation, there is an error between the adjustment amount and the calibration amount. Repeat the above steps to calculate the calibration amount again until the calibration amount meets the error requirements.

[0100] An embodiment of the present invention provides a method for calibrating the tube position of a CT system. This method establishes a coordinate system transformation relationship and solves the tube position calibration value based on multiple sets of corresponding points. By simply placing a shielding sheet horizontally, rather than at the rotation center, a single scan can simultaneously calculate the calibration values in the X and Z directions. This method is applicable to all gantry-mounted CT systems and avoids the limitations of a cumbersome calibration process and the need for multiple adjustments. In addition, the shielding sheet phantom used in the present invention is simple to manufacture and reusable, saving costs.

[0101] See also Figure 6 Another embodiment of the present invention further provides a device 200 for calibrating the position of a CT system tube, comprising:

[0102] The first module 201 is configured to obtain projection data of a horizontally placed shielding sheet projected onto the detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows;

[0103] The second module 202 is configured to calculate the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculate the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles;

[0104] The third module 203 is configured to solve the projection coordinates of the focus of the tube in the two-dimensional coordinate system of the detector based on the conversion relationship between the three-dimensional coordinate system of the shielding piece and the two-dimensional coordinate system of the detector, and the correspondence between the size of the shielding piece and the projection data;

[0105] The fourth module 204 is configured to generate calibration information to calibrate the tube position according to the projection coordinates of the rotation center and the tube focus in the two-dimensional coordinate system of the detector.

[0106] It should be noted that the device 200 for calibrating the position of the CT system tube provided in this embodiment corresponds to a technical solution that can be used to execute each method embodiment. Its implementation principle and technical effects are similar to those of the method and will not be repeated here.

[0107] Figure 7 This is a schematic diagram of the structure of an electronic device provided in another embodiment of the present invention, which is used to implement the method for calibrating the position of a CT system tube in a method embodiment. The electronic device 300 may include a processing device (e.g., a central processing unit, a graphics processing unit, etc.) 301, which can perform various appropriate actions and processes to implement the methods described in various embodiments of the present invention based on programs stored in a read-only memory (ROM) 302 or programs loaded from a storage device 308 into a random access memory (RAM) 303. RAM 303 also stores various programs and data required for the operation of the electronic device 300. The processing device 301, ROM 302, and RAM 303 are interconnected via a bus 304. An input / output (I / O) interface 305 is also connected to bus 304.

[0108] Typically, the following devices may be connected to the I / O interface 305: an input device 306 including, for example, a touch screen, a touchpad, a keyboard, a mouse, a camera, a microphone, an accelerometer, a gyroscope, etc.; an output device 307 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage device 308 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 309. The communication device 309 may allow the electronic device 300 to communicate with other devices wirelessly or by wire to exchange data. Figure 7 The electronic device 300 is shown with various devices, but it should be understood that it is not required to implement or possess all of the devices shown. More or fewer devices may be implemented or possessed instead.

[0109] In particular, according to an embodiment of the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a non-transitory computer-readable medium, and the computer program includes program code for executing the method shown in the flowchart, thereby implementing the method described above. In such an embodiment, the computer program can be downloaded and installed from the network via the communication device 309, or installed from the storage device 308, or installed from the ROM 302. When the computer program is executed by the processing device 301, the above-mentioned functions defined in the method of the embodiment of the present invention are performed.

[0110] Another embodiment of the present invention further provides a computer-readable medium, which may be included in the electronic device or may exist independently without being incorporated into the electronic device. When executed by a processor, the computer program can implement the aforementioned method for managing a large number of small files.

[0111] The above description is merely a preferred embodiment of the present invention. Those skilled in the art should understand that the scope of the present invention is not limited to technical solutions formed by specific combinations of the above-mentioned technical features. It also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents, without departing from the above-mentioned disclosure. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A method for calibrating the position of a CT system tube, characterized in that: include: Acquire projection data of a horizontally placed shielding sheet projected onto the detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows; Calculate the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculate the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles; According to the conversion relationship between the three-dimensional coordinate system of the shield and the two-dimensional coordinate system of the detector, and the corresponding relationship between the size of the shield and the projection data, the projection coordinates of the focus of the tube in the two-dimensional coordinate system of the detector are solved: The focus of the tube is the coordinate origin and the horizontal direction is Axis and frame rotation axis are The axis and the perpendicular line to the horizontal plane are Axis, establish the three-dimensional coordinate system of the tube focus; The upper left corner of the occlusion piece is the coordinate origin and the plane where the occlusion piece is located is The perpendicular line between the plane and the shielding piece is Y Axis, establish the three-dimensional coordinate system of the shielding piece; The detector's two-dimensional coordinate system is established with the detector's upper left corner as the coordinate origin and the detector's plane as the coordinate plane. The projection of the tube focus on the detector plane is taken as the coordinate origin and the plane where the detector is located is taken as the coordinate plane to establish a two-dimensional coordinate system for the projected image. Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shielding piece: in, 、 、 is the three-dimensional coordinate of any point in the three-dimensional coordinate system of the tube focus, 、 、 is the corresponding coordinate of any point in the three-dimensional coordinate system of the shielding piece, is the rotation matrix, is the translation matrix; Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projection image: in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the two-dimensional coordinate system of the projection image, is the distance from the tube focus to the detector; Obtain the transformation relationship matrix between the two-dimensional coordinate system of the projection image and the two-dimensional coordinate system of the detector: in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the detector two-dimensional coordinate system, 、 is the two-dimensional coordinate of the origin of the projected image two-dimensional coordinate system in the detector two-dimensional coordinate system, 、 Respectively represent the actual size of a single pixel in the X and Z directions in the two-dimensional coordinate system of the detector; Get the transformation matrix between the three-dimensional coordinate system of the shield and the two-dimensional coordinate system of the detector: According to the above formula, calculate the projection coordinates of the tube focus in the detector's two-dimensional coordinate system 、 ; According to the projection coordinates of the rotation center and the tube focus in the detector's two-dimensional coordinate system, calibration information is generated to calibrate the tube position: in, 、 Respectively represent the calibration amount of the tube position in the X direction and the Z direction, 、 Represents the projection coordinates of the rotation center in the detector's two-dimensional coordinate system.

2. A device for calibrating the position of a CT system tube, characterized in that: include: A first module is configured to obtain projection data of a horizontally placed shielding sheet projected onto the detector when the gantry rotates, wherein the shielding sheet includes a plurality of hollow windows; The second module is configured to calculate the projection center of gravity of the hollow window on the shielding sheet on the detector, and calculate the projection coordinates of the rotation center in the two-dimensional coordinate system of the detector based on the projection center of gravity at different exposure angles; The third module is configured to solve the projection coordinates of the tube focus in the detector's two-dimensional coordinate system based on the conversion relationship between the shield's three-dimensional coordinate system and the detector's two-dimensional coordinate system, and the correspondence between the shield's size and the projection data: The focus of the tube is the coordinate origin and the horizontal direction is Axis and frame rotation axis are The axis and the perpendicular line to the horizontal plane are Axis, establish the three-dimensional coordinate system of the tube focus; The upper left corner of the occlusion piece is the coordinate origin and the plane where the occlusion piece is located is The perpendicular line between the plane and the shielding piece is Y Axis, establish the three-dimensional coordinate system of the shielding piece; The detector's two-dimensional coordinate system is established with the detector's upper left corner as the coordinate origin and the detector's plane as the coordinate plane. The projection of the tube focus on the detector plane is taken as the coordinate origin and the plane where the detector is located is taken as the coordinate plane to establish a two-dimensional coordinate system for the projected image. Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the three-dimensional coordinate system of the shielding piece: in, 、 、 is the three-dimensional coordinate of any point in the three-dimensional coordinate system of the tube focus, 、 、 is the corresponding coordinate of any point in the three-dimensional coordinate system of the shielding piece, is the rotation matrix, is the translation matrix; Obtain the transformation relationship matrix between the three-dimensional coordinate system of the tube focus and the two-dimensional coordinate system of the projection image: in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the two-dimensional coordinate system of the projection image, is the distance from the tube focus to the detector; Obtain the transformation relationship matrix between the two-dimensional coordinate system of the projection image and the two-dimensional coordinate system of the detector: in, 、 is the two-dimensional coordinate of the corresponding point of the arbitrary point projected on the detector plane in the detector two-dimensional coordinate system, 、 is the two-dimensional coordinate of the origin of the projected image two-dimensional coordinate system in the detector two-dimensional coordinate system, 、 Respectively represent the actual size of a single pixel in the X and Z directions in the two-dimensional coordinate system of the detector; Get the transformation matrix between the three-dimensional coordinate system of the shield and the two-dimensional coordinate system of the detector: According to the above formula, calculate the projection coordinates of the tube focus in the detector's two-dimensional coordinate system 、 ; The fourth module is configured to generate calibration information for tube position calibration based on the projection coordinates of the rotation center and the tube focus in the detector's two-dimensional coordinate system: in, 、 Respectively represent the calibration amount of the tube position in the X direction and the Z direction, 、 Represents the projection coordinates of the rotation center in the detector's two-dimensional coordinate system.

3. An electronic device, characterized in that: include: one or more processors; a storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method for calibrating the position of a tube of a CT system as claimed in claim 1 .

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for calibrating the position of a CT system tube as claimed in claim 1 is implemented.

Images