Calibration method and system for geometric calibration of scanning and imaging equipment

Abstract

Provided is a calibration method for calibrating a scanning and imaging device. The calibration method comprises: by means of a detector, collecting rays which have passed through a geometric calibration phantom so as to obtain detector data, the detector data comprising an actual projection position of the rays on the detector after the rays have passed through the geometric calibration phantom; obtaining initial ray source parameters and initial detector parameters; according to the initial ray source parameters, the initial detector parameters, and the positional relationship of the geometric calibration phantom with respect to a ray source and the detector, obtaining a theoretical projection position of the geometric calibration phantom on the detector by means of geometric calculation; constructing an optimization function of the deviation between the actual projection position and the theoretical projection position in terms of the ray source parameters and the detector parameters; and according to the optimization function, determining the ray source parameters and the detector parameters which correspond to the minimum deviation value as optimized ray source parameters and optimized detector parameters, and determining the optimized ray source parameters and the optimized detector parameters as geometric calibration parameters.

Description

Calibration method and system for geometric calibration of scanning imaging equipment

[0001] This application claims priority to Chinese patent application No. 202311864035.5 filed on December 29, 2023, the contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the field of scanning imaging technology, and more particularly, to a calibration method and a calibration system for performing geometric calibration on a scanning imaging device. Background Art

[0003] According to scanning imaging theory, if you want to accurately reconstruct the image of the scanned object, you must know the precise position of the radiation source target and the detector crystal. Due to errors in mechanical manufacturing and installation, geometric calibration becomes an essential step in scanning imaging.

[0004] For example, in static CT scanning imaging technology, according to CT imaging theory, accurate CT reconstruction of the scanned object requires the precise position of the radiation source target and detector crystal. Due to errors in mechanical manufacturing and installation, geometric calibration becomes an essential step in CT imaging. Static CT using distributed radiation sources or multiple single-target radiation sources, due to the larger size or greater number of radiation sources themselves, will also result in greater manufacturing and installation errors, significantly affecting image quality. Similarly, detectors face the same issues, requiring geometric calibration to correct for these errors.

[0005] The above information disclosed in this section is only for understanding of the background of the technical concept of the present disclosure and therefore may contain information that does not constitute related art. Summary of the Invention

[0006] Embodiments of the present disclosure provide a calibration method and a calibration system for geometrically calibrating a scanning imaging device.

[0007] In one aspect, a calibration method for geometrically calibrating a scanning imaging device is provided. The scanning imaging device includes a radiation source for emitting radiation and a detector for receiving radiation. During the calibration process, a geometric calibration phantom is located in a scanning area formed by the radiation. The calibration method includes:

[0008] collecting, by the detector, rays passing through the scanning area to obtain detector data, wherein the detector data includes an actual projection position of the rays on the detector after the rays pass through the scanning area;

[0009] Acquiring initial ray source parameters and initial detector parameters, wherein the ray source parameters are used to represent the position of the ray source in the calibration system, and the detector parameters are used to represent the position of the detector in the calibration system;

[0010] Obtaining a theoretical projection position of the geometric calibration phantom on the detector through geometric calculation according to initial ray source parameters, initial detector parameters, and a positional relationship of the geometric calibration phantom relative to the ray source and the detector;

[0011] Calibrate the ray source parameters and the detector parameters according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters; and

[0012] The optimized ray source parameters and the optimized detector parameters are determined as geometric calibration parameters.

[0013] According to some exemplary embodiments, the ray source parameters and the detector parameters are calibrated according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters, including: constructing an optimization function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters, in which the deviation is the dependent variable, and the ray source parameters and the detector parameters are independent variables.

[0014] According to some exemplary embodiments, the ray source parameters and the detector parameters are calibrated according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters, and also include: according to the optimization function, determining the ray source parameters and detector parameters corresponding to the minimum value of the deviation as the optimized ray source parameters and optimized detector parameters, and determining the optimized ray source parameters and optimized detector parameters as geometric calibration parameters.

[0015] According to some exemplary embodiments, the ray source includes N s targets, the N s Target points are spaced apart along the first direction, where N sis a positive integer greater than or equal to 2; calibrating the ray source parameters and the detector parameters according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters, including: constructing an optimization function, the optimization function including a projection position constraint term and a target distance constraint term, wherein the projection position constraint term is a first function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters; the target distance constraint term is a second function of the deviation between the actual distance and the theoretical distance between two adjacent targets with respect to the ray source parameters and the detector parameters.

[0016] According to some exemplary embodiments, in the optimization function, the projection position constraint term has a first weight value, and the target point distance constraint term has a second weight value.

[0017] According to some exemplary embodiments, the ray source parameters and the detector parameters are calibrated according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters, and also include: according to the optimization function, determining the ray source parameters and the detector parameters corresponding to the minimum value of the weighted sum of the deviation between the actual projection position and the theoretical projection position and the deviation between the actual distance and the theoretical distance between two adjacent target points as the optimized ray source parameters and optimized detector parameters, and determining the optimized ray source parameters and the optimized detector parameters as geometric calibration parameters.

[0018] According to some exemplary embodiments, the calibration system includes a rotating table, and the geometric calibration phantom is located on the rotating table; the detector collects rays passing through the scanning area to obtain detector data, including: controlling the ray source to emit rays; controlling the rotating table to rotate to drive the geometric calibration phantom to rotate m circles, where m is a positive integer greater than or equal to 1; and during the process of the geometric calibration phantom rotating m circles, the detector collects rays emitted from the ray source and passing through the scanning area.

[0019] According to some exemplary embodiments, the calibration system includes a lifting platform, and the geometric calibration phantom is located on the lifting platform; the detector collects the rays passing through the scanning area to obtain the detector data, including: controlling the ray source to emit rays; controlling the lifting platform to move up and down to drive the geometric calibration phantom to move up and down.

[0020] According to some exemplary embodiments, the ray source includes N s targets, the N s Target points are spaced apart along the first direction, where N sis a positive integer greater than or equal to 2; the detector collects the rays passing through the scanning area and obtains the detector data, including: controlling the N s The target points emit rays in a set order; and in the N s In the process of each target point emitting rays in a set order, the detector collects rays emitted from the ray source and passing through the scanning area.

[0021] According to some exemplary embodiments, the calibration system includes a rotating table, and the geometric calibration phantom is located on the rotating table; the ray source includes N s targets, the N s Target points are spaced apart along the first direction, where N s is a positive integer greater than or equal to 2; the detector collects the rays passing through the scanning area to obtain the detector data, including: controlling the N s The target points emit rays in a set order; the rotating stage is controlled to rotate to drive the geometric calibration phantom to rotate m circles, where m is a positive integer greater than or equal to 1; and s During the process in which the target points emit rays in a set order and the geometric calibration phantom rotates m circles, the detector collects rays emitted from the ray source and passing through the scanning area.

[0022] According to some exemplary embodiments, the ray source parameters include: s The position coordinates of the first target point in the calibration system, the N s The arrangement direction of the targets, and the N s The number of each target in the target.

[0023] According to some exemplary embodiments, the detector includes a detector arm and a plurality of detection units mounted on the detector arm; the plurality of detection units are arranged in a straight line on the detector arm, and the detector parameters include: the position coordinates of the first detection unit among the plurality of detection units in a calibration system, and the arrangement direction of the plurality of detection units; or, the plurality of detection units are arranged in an arc on the detector arm, and the detector parameters include: the angle and radius of the first detection unit among the plurality of detection units in the calibration system.

[0024] According to some exemplary embodiments, the calibration method further includes: before placing the geometric calibration phantom in the scanning area formed by the rays, collecting air projection data through the detector; obtaining the detector data includes: collecting rays passing through the scanning area through the detector to obtain initial detector data; and, using the air projection data, correcting the initial detector data to obtain the detector data.

[0025] According to some exemplary embodiments, the geometric calibration phantom includes at least one metal wire.

[0026] According to some exemplary embodiments, the geometric calibration phantom includes a plurality of metal wires, and the plurality of metal wires are distributed on the rotating stage with different radii and / or different angles.

[0027] On the other hand, a calibration system for geometrically calibrating a scanning imaging device is provided, the calibration system comprising: a calibration device body; a geometric calibration phantom disposed on the calibration device body; a driving member, the driving member being used to drive the geometric calibration phantom to move; and a controller, the controller being configured to geometrically calibrate the scanning imaging device according to the calibration method described above.

[0028] On the other hand, a calibration system for geometrically calibrating a scanning imaging device is provided, the calibration system comprising: a base; a rotating table connected to the base; a geometric calibration phantom disposed on the rotating table, the geometric calibration phantom being located at an off-center position of the rotating table; and a driving member, the driving member being used to drive the rotating table to rotate, thereby driving the geometric calibration phantom to rotate.

[0029] According to some exemplary embodiments, the calibration system further includes: a lifting platform connected to the base, and the rotating platform is disposed on the lifting platform.

[0030] According to some exemplary embodiments, the geometric calibration phantom includes at least one metal wire; or, the geometric calibration phantom includes a plurality of metal wires, and the plurality of metal wires are distributed on the rotating stage with different radii and / or different angles.

[0031] According to some exemplary embodiments, the scanning imaging device includes a detector including a plurality of detector crystals; and a diameter of the metal wire is no greater than a width of a single detector crystal.

[0032] Additional aspects and advantages of the present disclosure will be set forth in part in the following description and, in part, will be obvious from the following description, or may be learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0034] FIG1 schematically shows a schematic diagram of the projection relationship between a ray source, an object to be inspected, and a detector.

[0035] FIG2 is a schematic structural diagram of a static CT device according to some exemplary embodiments of the present disclosure.

[0036] FIG3A is a schematic structural diagram of a scanning stage included in a static CT device according to some exemplary embodiments of the present disclosure.

[0037] FIG3B is a schematic structural diagram of a scanning stage included in a static CT device according to other exemplary embodiments of the present disclosure.

[0038] FIG4A is a schematic structural diagram of a calibration system according to some exemplary embodiments of the present disclosure.

[0039] FIG4B is a schematic structural diagram of a calibration system according to other exemplary embodiments of the present disclosure.

[0040] FIG. 4C is a projection diagram of the four metal wires shown in FIG. 4B on the rotating stage.

[0041] 4D is a side view of the calibration system shown in FIG. 4A .

[0042] FIG5 is a flowchart of a calibration method according to some exemplary embodiments of the present disclosure.

[0043] FIG6 is an exemplary flowchart of obtaining optimized ray source parameters and optimized detector parameters in a calibration method according to some exemplary embodiments of the present disclosure.

[0044] FIG7 is an exemplary flowchart of obtaining optimized ray source parameters and optimized detector parameters in a calibration method according to other exemplary embodiments of the present disclosure.

[0045] FIG8 schematically shows a structural block diagram of a controller of a calibration system according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure. In addition, the various embodiments provided below and the technical features in the embodiments may be combined with each other in any manner.

[0047] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. In addition, the terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components. All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used here should be interpreted as having meanings consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0048] In the description of the present disclosure, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present disclosure 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 disclosure. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present disclosure, unless otherwise specified, "multiple" means two or more.

[0049] In the description of this disclosure, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on the specific circumstances.

[0050] In the present disclosure, computed tomography (CT) imaging refers to the use of radiation to perform a cross-sectional scan of an object, converting the analog signal received by a detector into a digital signal, calculating the attenuation coefficient of each pixel using an electronic computer, and reconstructing the image to display the cross-sectional structure of each part of the object.

[0051] FIG1 schematically shows a schematic diagram of the projection relationship between a ray source, an object under inspection, and a detector. Referring to FIG1 , in an embodiment of the present disclosure, rays (such as X-rays, gamma rays, etc.) emitted by a ray source S are incident on the object under inspection OB, and rays transmitted through the object under inspection OB are detected by a detector D. A spatial point X on the object under inspection OB is acted upon by the ray source S to an image point Y on the detector D. In forward projection (also called forward projection), the pixel value of the spatial point on the object under inspection OB is known, and the projection value of the image point on the detector D is obtained. In reverse projection (also called backward projection), the projection value of the image point on the detector D is known, and the pixel value of the spatial point on the object under inspection OB is obtained.

[0052] Computed tomography (CT) technology, because it can eliminate the effects of overlapping objects, has played a vital role in security inspections and medical fields. Traditional CT systems use a slip-ring mechanism to acquire projection data at different angles by rotating the X-ray source and detector. Reconstruction methods produce tomographic images, thereby revealing internal information about the inspected baggage. Traditional CT systems typically rely on slip-ring rotation during data acquisition, which not only limits scanning speed and is bulky, but also requires high machining precision and is expensive, limiting their widespread practical application. In recent years, carbon nanotube X-ray tube technology has entered the practical field. Unlike traditional X-ray sources, it does not require high temperatures to generate X-rays. Instead, it generates cathode rays based on discharge at the tip of the carbon nanotube, which then strikes the target to produce X-rays. Its advantages include fast switching on and off and a smaller size. Arranging these X-ray sources in a ring shape to irradiate objects at different angles creates a "static CT" system that does not require rotation. This significantly improves X-ray imaging speed and, by eliminating the slip-ring mechanism, reduces costs. This holds significant significance for applications in security inspections and other fields.

[0053] FIG2 is a schematic diagram of the structure of a static CT device according to some exemplary embodiments of the present disclosure. Referring to FIG2 , the static CT device according to an embodiment of the present disclosure may include a scanning stage, a transmission mechanism 110, a control device 140, and an imaging device 130. For example, the scanning stage may include a radiation source, a detector, and an acquisition device.

[0054] For example, in an embodiment of the present disclosure, the ray source may be a distributed ray source, which may include multiple target points, for example, multiple X-ray target points. In a distributed X-ray source, the target point refers to the emission point or focus of the ray source. Specifically, high-energy electrons are emitted from the cathode and bombard the metal anode target, thereby generating X-rays. The energy of the emitted X-rays depends on the material of the anode target, while the intensity of the X-rays depends on the electron flux and electron energy bombarding the anode target. In a distributed X-ray source, multiple cathodes correspond one-to-one to multiple target points, so that multiple target points receive electron beams from multiple cathodes to generate multiple beams of X-rays. This design enables the distributed X-ray source to achieve the effect of generating more X-ray radiation sources using fewer cathode components, thereby improving the stability of the system, reducing the number of cathode components used, and reducing the production cost of the equipment.

[0055] In static CT devices that utilize distributed radiation sources, multiple targets are combined and activated in a set order at different angles to obtain multiple projection data sets from various angles. These projection data sets can be used in computer reconstruction algorithms to generate high-quality cross-sectional images. One advantage of using a distributed X-ray source is that it can reduce artifacts and improve image quality. By using multiple targets, the emission positions of the X-ray beam are more evenly distributed, providing more projection angles and data, reducing artifacts in the reconstructed image, and providing more accurate anatomical information. In other words, the targets in a distributed X-ray source refer to the points or areas that emit X-ray beams, and their distribution helps to obtain high-quality projection data for the reconstruction of static CT images.

[0056] In the embodiments of the present disclosure, multiple targets in a distributed radiation source can be arranged along a predetermined first direction. For example, the predetermined first direction can be a straight line or an arc. The embodiments of the present disclosure do not impose any particular restrictions on the arrangement of the targets in the distributed radiation source.

[0057] FIG3A is a schematic diagram of the structure of a scanning stage included in a static CT device according to some exemplary embodiments of the present disclosure. FIG3B is a schematic diagram of the structure of a scanning stage included in a static CT device according to other exemplary embodiments of the present disclosure. Referring to FIG3A and FIG3B , in an embodiment of the present disclosure, the static CT device includes a distributed radiation source 20 and a detector 30. The distributed radiation source 20 may include multiple targets 210. In some embodiments, as shown in FIG3A , the multiple targets 210 may be arranged in an arc shape. Accordingly, the detector 30 may include multiple detection units 310 arranged in an arc shape or a circle. In some embodiments, as shown in FIG3B , the multiple targets 210 may be arranged along a straight line. Accordingly, the detector 30 may include multiple detection units 310 arranged along a straight line. It should be noted that the embodiments of FIG2 to FIG3B are merely schematic diagrams of the structures of static CT devices according to some exemplary embodiments of the present disclosure, and do not represent all embodiments of the present disclosure. In the embodiments of the present disclosure, any suitable arrangement of distributed radiation sources and detectors may be employed.

[0058] In the embodiment of the present disclosure, the multiple target points 210 each emit radiation toward the inspected object 120, and the multiple detection units 310 are used to detect the radiation that has passed through the inspected object 120. For example, in the embodiment shown in Figures 3A and 3B, the multiple target points 210 emit X-rays, and the multiple detection units 310 receive a portion of the X-rays emitted from the multiple target points 210 that have passed through the inspected object 120. Thus, a scanning area is formed between the radiation source 20 and the detector 30 for scanning the inspected object 120. Within this scanning area, at least one plane located approximately in the middle of the scanning area and perpendicular to the conveying direction of the conveying mechanism 110 can be referred to as a scanning plane.

[0059] For example, the detection unit 310 may include at least one detector crystal. For example, the detection unit 310 may include one detector crystal. For another example, the detection unit 310 may include multiple detector crystals, and the multiple detector crystals may be arranged along a one-dimensional direction, or the multiple detector crystals may be arranged along a two-dimensional direction.

[0060] It should be understood that each detector crystal is a basic unit of the detector, which can absorb radiation (such as X-rays) and convert it into other forms of energy, such as light or electrical signals. For example, the materials of the detector crystals can include oxides and halides (such as iodide and fluoride).

[0061] For example, in the embodiment shown in FIG2 , the transport mechanism 110 carries the object 120 under inspection and drives the object 120 in linear motion. The control device 140 controls the order in which the radiation source 20 emits beams at multiple targets 210, causing the detector 30 to output digital signals corresponding to the projection data. The imaging device 130 reconstructs a CT image of the object 120 under inspection based on the digital signals.

[0062] It should be noted that in the embodiments of the present disclosure, the imaging device 130 can use various known reconstruction algorithms to reconstruct the CT image of the inspected object. For example, the reconstruction algorithm can be an iterative, analytical, or other reconstruction algorithm. The embodiments of the present disclosure do not place any particular restrictions on the reconstruction algorithm.

[0063] In some embodiments of the present disclosure, each distributed ray source 20 has one or more targets, the energy of the targets can be set, and the order of target activation can be set. For example, the targets can be distributed on multiple scanning planes (for example, the scanning plane is perpendicular to the direction of passage). In each plane, the target distribution can be continuous or discontinuous, one or more straight lines or arcs. Since the target energy can be set, a variety of scanning modes can be achieved during the beam emission process, such as different targets having different energy spectra, or targets located in different planes having different energies. The targets can be designed in groups, such as the targets of each module as a group, or the targets of each plane as a group. The order of electronic targeting of targets in the same group can be adjusted, and sequential beam emission and alternating beam emission can be achieved. Targets in different groups can be activated at the same time for scanning to speed up the scanning speed.

[0064] The detector 30 may be a single row or multiple rows, and the detector type may be a single energy, dual energy or energy spectrum detector.

[0065] The transport mechanism 110 includes a stage or conveyor belt. The control device 140 controls the X-ray machine and detector frames. By controlling the beam emission pattern of the distributed X-ray source and the linear translation of the object, or a combination of the two, spiral scanning trajectories, circular scanning trajectories, or other special trajectories can be achieved. The control device 140 is responsible for controlling the CT system's operation, including mechanical rotation, electrical control, and safety interlocks. Specifically, it controls the X-ray source's beam emission speed / frequency, energy, and sequence, and controls detector data readout and reconstruction.

[0066] Static CT has become a research hotspot in the CT field due to its advantages such as high scanning speed, high stability, and flexible scanning methods. However, as a new technology, it has different data processing requirements from traditional spiral CT. For example, due to the geometric correction issues caused by multiple targets, spiral CT processing methods cannot be used.

[0067] According to CT imaging theory, accurate CT reconstruction of the scanned object requires the precise position of the source target and detector crystals. Due to errors in mechanical manufacturing and installation, geometric calibration is an essential step in CT imaging. Static CT using distributed radiation sources or multiple single-target radiation sources can lead to greater manufacturing and installation errors due to the large size or number of radiation sources, significantly impacting image quality. Similarly, detectors face the same challenges, requiring geometric calibration to correct for these errors.

[0068] An embodiment of the present disclosure provides a calibration system for geometrically calibrating a scanning imaging device, which can perform geometric calibration on the scanning imaging device, for example, can perform geometric calibration on a static CT device based on a distributed ray source.

[0069] FIG4A is a schematic diagram of the structure of a calibration system according to some exemplary embodiments of the present disclosure. FIG4B is a schematic diagram of the structure of a calibration system according to other exemplary embodiments of the present disclosure. Referring to FIG4A and FIG4B , the calibration system 40 may include: a base 410; a rotating table 420 connected to the base 410; a geometric calibration phantom 50 disposed on the rotating table 420, the geometric calibration phantom 50 being located at an eccentric position of the rotating table 420; and a driving member 430, the driving member 430 being used to drive the rotating table 420 to rotate, thereby driving the geometric calibration phantom 50 to rotate.

[0070] In some exemplary embodiments, the geometric calibration phantom 50 may include at least one metal wire. For example, the geometric calibration phantom 50 includes only one metal wire, and the one metal wire is located at an eccentric position on the rotating stage 420 .

[0071] Referring to Figure 4A , a rotating stage 420 rotates about a rotation axis AX1. A metal wire is disposed perpendicularly on the rotating stage 420 and offset from the rotation axis AX1. Because the geometric calibration phantom is eccentrically positioned on the rotating stage 420, it can be positioned at different geometric positions during the rotation of the rotating stage 420. This facilitates obtaining calibration data from multiple different geometric positions, thereby improving calibration accuracy.

[0072] 4B , the rotating stage 420 rotates about the rotation axis AX1. The geometric calibration phantom 50 may include a plurality of metal wires, each of which is located at a different eccentric position on the rotating stage 420. That is, the plurality of metal wires are distributed on the rotating stage 420 at different radii and / or angles. In other words, on the rotating stage 420, at least one of the radius and angle of any one of the plurality of metal wires is different from at least one of the radius and angle of another of the plurality of metal wires.

[0073] For example, in the embodiment shown in FIG4B , four metal wires are schematically illustrated, which, for ease of description, are labeled as a first metal wire 501, a second metal wire 502, a third metal wire 503, and a fourth metal wire 504. The first metal wire 501, the second metal wire 502, the third metal wire 503, and the fourth metal wire 504 are all vertically disposed on the rotating stage 420, and are offset from the rotation axis AX1 by distances ρ1, ρ2, ρ3, and ρ4, respectively.

[0074] Figure 4C is a projection of the four wires shown in Figure 4B onto the rotating stage. Referring to Figures 4B and 4C, a polar coordinate system is established. In this polar coordinate system, the point of the orthographic projection of the rotation axis AX1 onto the rotating stage 420 is used as the pole AXO, and a ray OX originating from the pole AXO is used as the polar axis. Based on this, the positions of the four wires can be represented by (ρ, θ), where ρ corresponds to the polar diameter, radial vector, or radius in the polar coordinate system, specifically the distance between the orthographic projection of the wires on the rotating stage and the pole AXO; and θ corresponds to the polar angle or argument in the polar coordinate system, specifically the angle between the line connecting the orthographic projection of the wires on the rotating stage and the pole and the polar axis OX.

[0075] For example, the positions of the first metal wire 501, the second metal wire 502, the third metal wire 503, and the fourth metal wire 504 are respectively expressed as (ρ1, θ1), (ρ2, θ2), (ρ3, θ3), and (ρ4, θ4). Any two of ρ1, ρ2, ρ3, and ρ4 are not equal, and / or any two of θ1, θ2, θ3, and θ4 are not equal.

[0076] In this embodiment, multiple metal wires are arranged on the rotating table 420 and have different offset distances or offset angles from the rotation axis AX1. In this way, during the rotation of the rotating table 420, the multiple metal wires can be in different geometric positions, which is conducive to obtaining calibration data from multiple different geometric positions, thereby further improving the calibration accuracy.

[0077] In some exemplary embodiments, the metal wire may be a hard metal wire, so that the metal wire may be perpendicular to the table surface of the rotating table 420 , which is beneficial for placing the front end of the metal wire in the scanning area.

[0078] In some exemplary embodiments, the diameter of the metal wire is no greater than the width of a single detector crystal. By designing the diameter of the metal wire to be smaller, the accuracy of calibration can be improved.

[0079] 4A and 4B , the calibration system 40 may further include a lifting platform 440 connected to the base 410, and a rotating platform 420 disposed on the lifting platform 440. In this way, by controlling the lifting platform to translate up and down a fixed distance, the wire can be scanned at multiple height positions to obtain more calibration data, thereby improving calibration accuracy.

[0080] In the embodiment of the present disclosure, the base 410 is used to support other components and maintain the stability of the components installed thereon. The driving member 430 may include a movement driving mechanism for driving the lifting platform 440 to move up and down; and / or a rotation driving mechanism for driving the rotating platform 420 to rotate.

[0081] For example, the rotation drive mechanism for driving the turntable 420 to rotate may include at least one of a gear transmission mechanism, a servo motor drive mechanism, and a stepper motor drive mechanism. The gear transmission mechanism may include a drive motor, a drive gear, and a driven gear, and the rotational force is transmitted through the meshing of the gears. The servo motor drive is to achieve the rotation of the turntable by controlling the speed and position of the servo motor. The servo motor is usually used in combination with an encoder and a closed-loop control system to achieve high-precision rotation control. The stepper motor drive is to achieve the rotation of the turntable by controlling the pulse signal of the stepper motor. The stepper motor has a discrete step angle, which can accurately control the position and speed of the turntable.

[0082] For example, the mobile drive mechanism used to drive the lifting platform 440 up and down may include at least one of a screw drive mechanism, an electric screw drive mechanism, and a gear drive mechanism. The screw drive mechanism may include a screw and a nut that meshes with it. When the screw rotates, the nut moves along the screw's helical line, thereby achieving the up and down movement of the lifting platform. The electric screw drive mechanism combines screw drive and electric drive technology. The screw is driven by an electric motor to rotate, thereby driving the lifting platform up and down. The gear drive mechanism uses the meshing of gears to transmit force and motion. The up and down movement of the lifting platform can be achieved by rotating the drive gear.

[0083] It should be noted that in the embodiments of the present disclosure, there is no special restriction on the type and structure of the rotary drive mechanism and the mobile drive mechanism. Unless there is a conflict, various types of rotary drive mechanisms and mobile drive mechanisms known in the relevant field can be used in the embodiments of the present disclosure.

[0084] Some exemplary embodiments of the present disclosure also provide a calibration method for geometrically calibrating a scanning imaging device.

[0085] FIG4D is a side view of the calibration system shown in FIG4A . Referring to FIG4A through FIG4D , during calibration, the calibration system 40 is placed on a conveyor device (e.g., the conveyor mechanism 110 shown in FIG2 ) of the scanning imaging device. The conveyor device is controlled to transport the geometric calibration phantom 50 of the calibration system 40 to the X-ray scanning plane, such that the geometric calibration phantom 50 is within the scanning plane formed by the X-ray source 20 and the detector 30. For example, during geometric calibration, only the front end of the geometric calibration phantom 50 is within the scanning plane, while the rest of the calibration system 40 remains outside the scanning plane. This prevents interference with the calibration data from other parts of the calibration system 40.

[0086] FIG5 is a flow chart of a calibration method according to some exemplary embodiments of the present disclosure. Referring to FIG1 to FIG5 , the calibration method can be used to perform geometric calibration on a scanning imaging device. For example, the calibration method can perform geometric calibration on a static CT device. In the static CT device, the ray source 20 can be a distributed ray source, which includes N s Target 210, N s Target points are spaced apart along the first direction, where N s is a positive integer greater than or equal to 2. The first direction may correspond to the linear arrangement shown in FIG3A or the arc arrangement shown in FIG3B. It should be noted that in the embodiments of the present disclosure, no particular limitation is imposed on the arrangement direction and form of the multiple targets of the distributed radiation source.

[0087] In some embodiments of the present disclosure, the calibration method may include steps S510 to S550.

[0088] In step S510 , the detector 30 collects the rays passing through the scanning area to obtain detector data, wherein the detector data includes the actual projection position of the rays on the detector 30 after passing through the scanning area.

[0089] In some exemplary embodiments, the calibration method may include: before placing the geometric calibration phantom 50 in the scanning area or scanning plane formed by the ray, collecting the air projection data p by the detector 30 air .

[0090] It should be understood that when performing image reconstruction, it is necessary to know the detector reading when there is no object (i.e., only air) in order to remove this background value from the actual measurement data. For example, in CT imaging, a method called line integral is often used to obtain projection data. This process involves passing rays through the object and measuring the attenuation of the rays after passing through the object. This attenuation value (or projection data) reflects the properties of the material in the ray path, such as density and composition. Similar measurements can be made when there is no object present, that is, only air. The projection data thus obtained can be used as a reference or background value. During the actual image reconstruction process, this background value is removed from the measured projection data to obtain the ray attenuation caused only by the object itself.

[0091] In step S510, the acquisition of detector data includes: collecting rays passing through a scanning area (where the geometric calibration phantom 50 is located) through the detector 30 to obtain initial detector data p i ; and, using the air projection data p air , for the initial detector data p i Correction is performed to obtain the detector data prj i .

[0092] It should be noted that in this article, 1≤i≤N s , that is, i represents the number of a target point 210 in the distributed ray source.

[0093] For example, the following formula can be used to perform air correction to obtain the detector data prj i :prj i =p i / p air .

[0094] In some exemplary embodiments of the present disclosure, the calibration system 40 includes a rotating stage 420 , and the geometric calibration phantom 50 is located on the rotating stage 420 .

[0095] In this embodiment, the initial detector data p is obtained i It can include: controlling the ray source 20 to emit rays; controlling the rotation of the rotating table 420 to drive the geometric calibration phantom 50 to rotate m circles, where m is a positive integer greater than or equal to 1; and, during the process of the geometric calibration phantom 50 rotating m circles, the detector 30 collects rays emitted from the ray source 20 and passing through the scanning area.

[0096] In some exemplary embodiments of the present disclosure, the calibration system 40 includes a lifting platform 440 , and the geometric calibration phantom 50 is located on the lifting platform 440 .

[0097] In this embodiment, the initial detector data p is obtained i The method may include: controlling the ray source 20 to emit rays; controlling the lifting platform 440 to move up and down to drive the geometric calibration phantom 50 to move up and down; and during the lifting and lowering of the geometric calibration phantom 50 , the detector 30 collects rays emitted from the ray source 20 and passing through the scanning area.

[0098] In some exemplary embodiments of the present disclosure, the ray source 20 includes N s Target 210, N s Target points 210 are distributed along the first direction at intervals, where N s is a positive integer greater than or equal to 2.

[0099] In this embodiment, the initial detector data p is obtained i May include: Control N s The target points 210 emit radiation in a set order; and s When each target point 210 emits radiation in a set order, the detector 30 collects radiation emitted from the radiation source 20 and passing through the scanning area.

[0100] In some exemplary embodiments of the present disclosure, the calibration system 40 includes a rotating stage 420, and the geometric calibration phantom 50 is located on the rotating stage 420. The radiation source 20 includes N s Target 210, N s Target points 210 are spaced apart along the first direction, where N s is a positive integer greater than or equal to 2.

[0101] In this embodiment, the initial detector data p is obtained i May include: Control N s The target points 210 emit rays in a set order; the rotating stage 420 is controlled to rotate to drive the geometric calibration phantom 50 to rotate m circles, where m is a positive integer greater than or equal to 1; and s During the process in which each target point 210 emits radiation in a set order and the geometric calibration phantom 50 rotates m circles, the detector 30 collects radiation emitted from the radiation source and passing through the scanning area.

[0102] It should be noted that in the embodiments of the present disclosure, there are no special restrictions on the movement form, number of settings of the geometric calibration phantom, and the number of targets of the radiation source. In the absence of conflict, various situations can be combined and integrated with each other. For example, in some embodiments, the geometric calibration phantom 50 can be set on a rotating table, the rotating table is set on a lifting table, and the radiation source 20 can be a distributed radiation source including multiple targets. In this way, the detector data prj is obtained. i The steps can be adjusted accordingly according to the setting method, and will not be repeated here.

[0103] It should also be noted that in the embodiments of the present disclosure, the movement of the geometric calibration phantom 50 and the order in which the radiation sources emit beams are not particularly limited. For example, the geometric calibration phantom 50 may be fixed in one position, and all targets may be controlled to emit beams once in a set order. The rotating stage may then rotate to the next position, and all targets may be controlled to emit beams again, until the rotating stage completes one rotation.

[0104] In step S520 , initial ray source parameters and initial detector parameters are acquired, wherein the ray source parameters are used to represent the position of the ray source 20 in the calibration system 40 , and the detector parameters are used to represent the position of the detector 30 in the calibration system 40 .

[0105] The inventors discovered that in static CT scanning imaging equipment using distributed radiation sources, the large distances between targets, particularly when the source is composed of multiple single targets, can lead to inconsistent errors at each target. However, densely packed detector crystals result in relatively small errors, primarily due to the installation of the entire detector arm. Therefore, geometric calibration involves calibrating each target position individually and calibrating the detector as a whole.

[0106] In this paper, for the convenience of description, the ray source parameters are described as s i , the detector parameters are described as P d .

[0107] In some exemplary embodiments, the ray source is a distributed ray source, the target interval has a sufficiently high accuracy, and the error mainly comes from the installation of the entire ray source. Then, the target position can be calibrated as a whole, that is, {s i： 1≤i≤N s} is determined by the starting coordinates, arrangement direction and number i of the distributed ray source. In this embodiment, the relative position relationship between two adjacent targets in the ray source is known, and the ray source parameter s i Can include: N s The position coordinates of the first target point in the calibration system, N s The arrangement direction of the targets, and N s The number of each target in the target.

[0108] In some exemplary implementation cases, the detector arms are arranged in a straight line or an arc, and the parameters of the detector arms are the starting coordinates and the arrangement direction.

[0109] For example, referring to Figures 4A to 4D, the detector 30 may include a detector arm 320 and a plurality of detection units 310 mounted on the detector arm 320. The plurality of detection units 310 are arranged in a straight line on the detector arm 320. In this embodiment, the relative positional relationship between two adjacent detection units is known, and the detector parameter P isd It may include: the position coordinates of the first detection unit among the multiple detection units in the calibration system, and the arrangement directions of the multiple detection units.

[0110] For another example, multiple detection units 310 are arranged in an arc on the detector arm, and the relative position relationship between two adjacent detection units is known. The detector parameter P d It may include: the angle and radius of the first detection unit among the multiple detection units in the calibration system.

[0111] In step S530 , the theoretical projection position of the geometric calibration phantom 50 on the detector 30 is obtained through geometric calculation based on the initial ray source parameters, the initial detector parameters, and the positional relationship of the geometric calibration phantom 50 relative to the ray source 20 and the detector 30 .

[0112] For example, the detector data prj obtained in step S510 i includes the actual projection position, i.e., the detector data prj i In the above example, the actual projection position of the geometric calibration phantom 50 (e.g., a metal wire) can be extracted and can be described as pos(s i , P d ). It can be understood that the actual projection position is a function of the ray source parameters and the detector parameters.

[0113] For example, in step S530, the rotation center of the rotating stage 420 is used as the coordinate origin, and according to the rotation speed of the rotating stage 420 and the position of the geometric calibration phantom 50, the initial ray source parameter s is known. i and detector parameters P d In this case, through geometric calculation, we can obtain the projection data prj i The corresponding theoretical projection position of the geometric calibration phantom 50 is denoted as cpos(s i , P d ). It can be understood that the theoretical projection position cpos(s i , P d ) is also a function of the ray source parameters and detector parameters.

[0114] In step S540 , the ray source parameters and the detector parameters are calibrated according to the actual projection position and the theoretical projection position to obtain optimized ray source parameters and optimized detector parameters.

[0115] In step S550 , the optimized ray source parameters and the optimized detector parameters are determined as geometric calibration parameters.

[0116] FIG6 is an exemplary flowchart of obtaining optimized ray source parameters and optimized detector parameters in a calibration method according to some exemplary embodiments of the present disclosure.

[0117] 6 , in some exemplary embodiments, step S540 may include steps S541 - S542 .

[0118] In step S541, an optimization function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters is constructed. In the optimization function, the deviation is the dependent variable, and the ray source parameters and the detector parameters are the independent variables.

[0119] In step S542, according to the optimization function, the ray source parameters and the detector parameters corresponding to when the deviation takes the minimum value are determined as the optimized ray source parameters and the optimized detector parameters.

[0120] For example, in this embodiment, the optimized ray source parameters and the optimized detector parameters can be obtained by solving the following optimization function:

[0121] Among them, "argmin" is a mathematical term used to represent the parameter value (the value of the independent variable) of a function to achieve the minimum value in its domain. Specifically, in this optimization function, it means: when The ray source parameter s when the minimum value is obtained i and detector parameters P d ;s i is the ray source parameter; P d is the detector parameter; N s is the total number of targets in the distributed ray source; i represents the number of a target in the distributed ray source, 1≤i≤N s ;pos(s i , P d ) represents the actual projection position; cpos(s i , P d ) represents the theoretical projection position.

[0122] FIG7 is an exemplary flowchart of obtaining optimized ray source parameters and optimized detector parameters in a calibration method according to other exemplary embodiments of the present disclosure.

[0123] 7 , in some exemplary embodiments, step S540 may include steps S543 - S544 .

[0124] In step S543, an optimization function is constructed, which includes a projection position constraint item and a target distance constraint item, wherein the projection position constraint item is a first function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters; the target distance constraint item is a second function of the deviation between the actual distance and the theoretical distance between two adjacent target points with respect to the ray source parameters and the detector parameters.

[0125] For example, in the optimization function, the projection position constraint has a first weight value, and the target distance constraint has a second weight value. Optionally, the second weight value may be 0.

[0126] In step S544, according to the optimization function, the ray source parameters and detector parameters corresponding to the minimum value of the weighted sum of the deviation between the actual projection position and the theoretical projection position and the deviation between the actual distance between two adjacent target points and the theoretical distance are determined as the optimized ray source parameters and the optimized detector parameters.

[0127] In some exemplary implementation cases, some constraints are added to the optimization objective function according to the actual situation to make the solution of the optimization problem more stable. For example, although there is an error in the target position, the deviation between the target points is within a certain range. Then, the following target distance constraint term can be added to the optimization function, where dis(s i , s i+1 ) represents the distance between target points i and i+1, d s represents the theoretical distance between two targets, and λ1 and λ2 represent the weights of the two constraints.

[0128] For example, in this embodiment, the optimized ray source parameters and the optimized detector parameters can be obtained by solving the following optimization function:

[0129] Among them, "argmin" is a mathematical term used to represent the parameter value (the value of the independent variable) of a function to achieve the minimum value in its domain. Specifically, in this optimization function, it means: when The ray source parameter s when the minimum value is obtained i and detector parameters P d ;s i is the ray source parameter; P d is the detector parameter; N s is the total number of targets in the distributed ray source; i represents the number of a target in the distributed ray source; pos(s i , P d ) represents the actual projection position; cpos(s i , P d ) represents the theoretical projection position; dis(s i , s i+1 ) represents the distance between target points i and i+1; d s represents the theoretical distance between two targets; λ1 and λ2 represent the weight values ​​of the two constraints.

[0130] Specifically, in the above optimization function, is the projection position constraint, The projection position constraint has a weight of λ1, and the target distance constraint has a weight of λ2. In some exemplary embodiments, the projection position constraint has a weight of λ1 greater than the target distance constraint, so that the projection position constraint is more effectively considered during calibration.

[0131] Referring back to Figures 4A to 4D, the calibration system 40 according to some embodiments of the present disclosure may include: a calibration device body; a geometric calibration phantom 50 arranged on the calibration device body; a driving member 430, the driving member 430 is used to drive the geometric calibration phantom to move; and a controller 450, the controller 450 is configured to: perform geometric calibration on the scanning imaging device according to the above-mentioned calibration method.

[0132] For example, the calibration device body may include: a base 410; and a rotating platform 420 connected to the base 410. Alternatively, the calibration device body may include: a base 410; a lifting platform 440 connected to the base 410; and a rotating platform 420 connected to the base 410.

[0133] FIG8 schematically shows a structural block diagram of a controller of a calibration system according to an exemplary embodiment of the present disclosure.

[0134] As shown in Figure 8, the controller 450 of the calibration system according to an embodiment of the present disclosure may include a processor 1001, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage part 1008 into a random access memory (RAM) 1003. The processor 1001 may, for example, include a general-purpose microprocessor (such as a CPU), an instruction set processor and / or a related chipset and / or a special-purpose microprocessor (for example, an application-specific integrated circuit (ASIC)), etc. The processor 1001 may also include on-board memory for caching purposes. The processor 1001 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0135] Various programs and data required for the operation of the controller 450 are stored in the RAM 1003. The processor 1001, the ROM 1002, and the RAM 1003 are connected to each other via a bus 1004. The processor 1001 executes the various operations of the method flow according to the embodiment of the present disclosure by executing the programs in the ROM 1002 and / or the RAM 1003. It should be noted that the programs may also be stored in one or more memories other than the ROM 1002 and the RAM 1003. The processor 1001 may also execute the various operations of the method flow according to the embodiment of the present disclosure by executing the programs stored in the one or more memories.

[0136] According to an embodiment of the present disclosure, the controller 450 may further include an input / output (I / O) interface 1005, which is also connected to the bus 1004. The controller 450 may further include one or more of the following components connected to the I / O interface 1005: an input section 1006 including a keyboard, a mouse, etc.; an output section 1007 including devices such as a cathode ray tube (CRT), a liquid crystal display (LCD), and a speaker; a storage section 1008 including a hard disk; and a communication section 1009 including a network interface card such as a LAN card or a modem. The communication section 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to the I / O interface 1005 as needed. A removable medium 1011, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed in the drive 1010 as needed, so that computer programs read therefrom can be installed into the storage section 1008 as needed.

[0137] The present disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments, or may exist independently and not be incorporated into the device / apparatus / system. The computer-readable storage medium carries one or more programs, and when executed, implements the method according to the embodiments of the present disclosure.

[0138] According to an embodiment of the present disclosure, a computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, it may include but is not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in combination with an instruction execution system, apparatus, or device. For example, according to an embodiment of the present disclosure, a computer-readable storage medium may include the ROM 1002 and / or RAM 1003 described above and / or one or more memories other than ROM 1002 and RAM 1003.

[0139] It should be noted that in the above embodiments, the calibration method is described using a static CT scanning imaging device with a distributed radiation source as an example. However, the embodiments of the present disclosure are not limited thereto. In other exemplary embodiments of the present disclosure, the calibration system and calibration method can also perform geometric calibration on a spiral CT device with a single target radiation source. During the calibration process, the radiation source and detector are in a static state.

[0140] It should also be noted that the embodiments of the present disclosure can also perform geometric calibration on single / multi-view X-ray imaging devices. For example, in some embodiments, the number of target points of the ray source can be N s =1. Although the single / multi-view X-ray imaging device itself is not a CT device and cannot perform CT imaging of the scanned object, when a single target point emits a beam, the data collected by the rotation of the calibration device meets the data completeness requirements of CT imaging and can also be used for CT reconstruction, and is therefore also applicable to the geometric calibration process described above.

[0141] According to an embodiment of the present disclosure, the program code for executing the computer program provided by the embodiment of the present disclosure can be written in any combination of one or more programming languages. Specifically, these computer programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages ​​include, but are not limited to, languages ​​such as Java, C++, python, "C" or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, partially on a remote computing device, or entirely on a remote computing device or server. In cases involving a remote computing device, the remote computing device can be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, using an Internet service provider to connect via the Internet).

[0142] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, program segment, or a part of code, and the above-mentioned module, program segment, or a part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0143] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0144] Although embodiments of the present disclosure have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and purpose of the present disclosure, and that the scope of the present disclosure is defined by the claims and their equivalents. It will be understood by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in various ways, without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

Claims

1. A calibration method for geometric calibration of a scanning imaging device, the scanning imaging device including a radiation source for emitting radiation and a detector for receiving radiation. During the calibration process, a geometric calibration phantom is located in the scanning area formed by the radiation, and it is characterized in that, The calibration method includes: Collecting, by the detector, rays passing through the scanning area to obtain detector data, where the detector data includes the actual projection positions of the rays on the detector after passing through the scanning area; Obtaining initial ray source parameters and initial detector parameters, where the ray source parameters are used to represent the position of the ray source in the calibration system, and the detector parameters are used to represent the position of the detector in the calibration system; Obtaining, through geometric calculation, the theoretical projection positions of the geometric calibration phantom on the detector according to the initial ray source parameters, the initial detector parameters, and the positional relationship of the geometric calibration phantom relative to the ray source and the detector; Calibrating the ray source parameters and the detector parameters according to the actual projection positions and the theoretical projection positions to obtain optimized ray source parameters and optimized detector parameters; and Determining the optimized ray source parameters and the optimized detector parameters as geometric calibration parameters.

2. The method according to claim 1, wherein, Calibrating the ray source parameters and the detector parameters according to the actual projection positions and the theoretical projection positions to obtain optimized ray source parameters and optimized detector parameters, including: Constructing an optimization function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters. In the optimization function, the deviation is the dependent variable, and the ray source parameters and the detector parameters are the independent variables.

3. The method according to claim 2, wherein Calibrating the ray source parameters and the detector parameters according to the actual projection positions and the theoretical projection positions to obtain optimized ray source parameters and optimized detector parameters, further including: According to the optimization function, determining the ray source parameters and the detector parameters corresponding to the minimum value of the deviation as the optimized ray source parameters and the optimized detector parameters, and determining the optimized ray source parameters and the optimized detector parameters as geometric calibration parameters.

4. The method according to claim 1, wherein The ray source includes N s target points, and the N s target points are spaced apart along a first direction, where N s is a positive integer greater than or equal to 2; Calibrating the ray source parameters and the detector parameters according to the actual projection positions and the theoretical projection positions to obtain optimized ray source parameters and optimized detector parameters, including: Constructing an optimization function, where the optimization function includes a projection position constraint term and a target point distance constraint term, where the projection position constraint term is a first function of the deviation between the actual projection position and the theoretical projection position with respect to the ray source parameters and the detector parameters; the target point distance constraint term is a second function of the deviation between the actual distance and the theoretical distance between two adjacent target points with respect to the ray source parameters and the detector parameters.

5. The method according to claim 4, wherein, In the optimization function, the projection position constraint term has a first weight value, and the target point distance constraint term has a second weight value.

6. The method according to claim 4 or 5, wherein Calibrating the ray source parameters and the detector parameters according to the actual projection positions and the theoretical projection positions to obtain optimized ray source parameters and optimized detector parameters, further including: According to the optimization function, when the weighted sum of the deviation between the actual projection position and the theoretical projection position and the deviation between the actual distance and the theoretical distance between two adjacent target points takes the minimum value, the corresponding ray source parameters and detector parameters are determined as the optimized ray source parameters and the optimized detector parameters, and the optimized ray source parameters and the optimized detector parameters are determined as the geometric calibration parameters.

7. The method according to any one of claims 1-6, wherein, The calibration system includes a turntable, and the geometric calibration phantom is located on the turntable; The obtaining of detector data by collecting, through the detector, rays passing through the scanning area includes: Controlling the ray source to emit rays; Controlling the turntable to rotate to drive the geometric calibration phantom to rotate m circles, where m is a positive integer greater than or equal to 1; and During the process of the geometric calibration phantom rotating m circles, the detector collects the rays emitted from the ray source and passing through the scanning area.

8. The method according to any one of claims 1-7, wherein The calibration system includes a lifting table, and the geometric calibration phantom is located on the lifting table; The obtaining of detector data by collecting, through the detector, rays passing through the scanning area includes: Controlling the ray source to emit rays; Controlling the lifting table to lift to drive the geometric calibration phantom to lift.

9. The method according to any one of claims 1-8, wherein, The radiation source includes N s target points, and the N s target points are spaced along a first direction, where N s is a positive integer greater than or equal to 2; The obtaining of detector data by collecting, through the detector, rays passing through the scanning area includes: Control the N s targets to emit rays in a set order; and During the process in which the N s target points emit rays in a set order, the detector collects the rays emitted from the ray source and passing through the scanning area.

10. The method according to any one of claims 1-6, wherein, The calibration system includes a rotary table, and the geometric calibration phantom is located on the rotary table; the radiation source includes N s target points, and the N s target points are spaced apart along a first direction, where N s is a positive integer greater than or equal to 2; The obtaining of detector data by collecting, through the detector, rays passing through the scanning area includes: Control the N s target points to emit rays in a set order; Controlling the turntable to rotate to drive the geometric calibration phantom to rotate m circles, where m is a positive integer greater than or equal to 1; and During the process that the N s targets emit rays in a set order and the geometric calibration phantom rotates m circles, the detector collects the rays emitted from the ray source and passing through the scanning area.

11. The method according to claim 9 or 10, wherein The ray source parameters include: the N s position coordinates of the first target among the N s targets in the calibration system, the arrangement direction of the N s targets, and the numbers of the respective targets among the N 12. The method according to any one of claims 1-11, wherein, The detector includes a detector arm and a plurality of detection units mounted on the detector arm; The plurality of detection units are linearly arranged on the detector arm, and the detector parameters include: the position coordinates of the first detection unit among the plurality of detection units in the calibration system, and the arrangement direction of the plurality of detection units; or, the plurality of detection units are arc-arranged on the detector arm, and the detector parameters include: the angle and radius of the first detection unit among the plurality of detection units in the calibration system.

13. The method according to any one of claims 1 to 12, wherein, The calibration method further includes: before placing the geometric calibration phantom in the scanning area formed by the rays, collecting air projection data through the detector; The obtaining of detector data includes: collecting, through the detector, rays passing through the scanning area to obtain initial detector data; and using the air projection data to correct the initial detector data to obtain the detector data.

14. The method according to any one of claims 1-13, wherein, The geometric calibration phantom includes at least one wire.

15. The method according to any one of claims 1-13, wherein, The geometric calibration phantom includes a plurality of wires, and the plurality of wires are distributed on the turntable with different radii and / or different angles from each other.

16. A calibration system for geometric calibration of a scanning imaging device, characterized in that, The calibration system includes: A calibration device main body; A geometric calibration phantom arranged on the calibration device main body; A driving member for driving the geometric calibration phantom to move; and A controller configured to perform geometric calibration on the scanning imaging device according to the calibration method as recited in any one of claims 1-13.

17. A calibration system for geometric calibration of a scanning imaging device, characterized in that, The calibration system includes: Base; Rotating table connected to the base; Geometric calibration module disposed on the rotating table, the geometric calibration module being located at the centrifugal position of the rotating table; and Driver for driving the rotation of the rotating table to drive the rotation of the geometric calibration module.

18. The system according to claim 17, wherein, The calibration system further includes: a lifting table connected to the base, and the rotating table is disposed on the lifting table.

19. The system according to claim 17 or 18, wherein, The geometric calibration module includes at least one wire; or The geometric calibration module includes a plurality of wires, and the plurality of wires are distributed on the rotating table with different radii and / or different angles from each other.

20. The system according to claim 19, wherein, The scanning imaging device includes a detector, and the detector includes a plurality of detector crystals; and The diameter of the wire is not greater than the width of a single detector crystal.

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