Large-view-field cone beam CT imaging method, device and equipment and storage medium

Abstract

The embodiment of the invention relates to the field of cone-beam CT imaging, and discloses a large-view-field cone-beam CT imaging method, device and equipment and a storage medium. A target is scanned around a scanning center according to a first sub-scanning path and a second sub-scanning path; in the scanning process, the main mechanical arm and the auxiliary mechanical arm drive the transmitting device and the receiving device to synchronously move, so that the center of the conical imaging beam is always perpendicular to the center of the receiving device; the first sub-scanning path comprises that the center of the transmitting device deflects for a preset angle from the center of the conical imaging beam to the scanning center to a preset direction and then rotates along a set track; the second sub-scanning path comprises that the center of the transmitting device rotates in the reverse direction of the set track after deflecting by two times of a preset angle in the reverse direction of the preset direction at the ending position of the first sub-scanning path; scanning data at the same position are combined and then subjected to back projection reconstruction, X-ray energy can be efficiently utilized without changing hardware equipment, and large-view cone beam CT imaging is achieved.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of cone-beam CT imaging, and particularly to a large-field-of-view cone-beam CT imaging method, apparatus, device, and storage medium. Background Art

[0002] Cone-beam CT imaging is applied in fields such as orthopedic C-arms, vascular C-arms, image-guided radiotherapy systems, and industrial CTs. The size of its reconstructed volume is limited by the detector size. In the fields of industrial CT and radiotherapy, it is necessary to perform scanning and reconstruction for relatively large targets. The large-field-of-view scanning imaging principle of industrial CT is as Figure 1 shown. S0 represents the radiation source, D1D2 represents the detector, δ represents the effective fan-beam angle, and D represents the distance from the radiation source to the detector. S0D1D2 constitutes the geometric layout of normal-field-of-view scanning. The object rotates 360° with O1 as the scanning center to complete the scanning and reconstruction, and components with a radius less than or equal to r1 can be detected. When performing offset large-field-of-view scanning, the geometric layout of the scanning remains unchanged, the scanning center on the examination table moves to O2, and the object rotates one week, and objects with a radius less than or equal to r2 can be detected. This method uses object offset to form large-field-of-view reconstruction. For simple mechanical design, industrial CTs all use the method of rotating the object on the turntable while the tube and the flat panel do not move for scanning. However, traditional medical cone-beam CTs all use the method of rotating the gantry with the tube and the flat panel while the human body does not move for imaging. Mature medical cone-beam CT products translate the flat-panel detector along the width direction of the scanning target (for example, cone-beam CT imaging in radiotherapy equipment produced by Varian and Elekta), as Figure 2 shown is the geometric layout of this kind of cone-beam CT normal scanning. After the flat-panel detector is translated, large-field-of-view scanning can be performed, and the geometric layout can be Figure 3 shown. However, the applicant found that this solution has two problems: First, it is necessary to change the collimator to change the X-ray range emitted by the tube. Since the tube does not move, the photons and energy of the X-ray are the strongest in the central region and gradually weaken towards the periphery. After the flat-panel detector is translated, for example, Figure 3 in the cases shown in (2) and (3), the X-rays in the off-center region are used, and the best region of the X-rays shown in Figure 3 (1) is not used; Second, since the flat-panel detector is offset, in order to form a reconstructed image, the rotation angle is increased. For example, in the case shown in Figure 3 (1), only 180° plus the fan angle plus the fan angle α (see Figure 2 ) need to be rotated, but Figure 3 in the cases shown in (2) or (3), a rotation angle of 360° is required, and the increased rotation angle requires higher hardware requirements. Summary of the Invention

[0003] The object of the present invention is to provide at least one large field of view cone beam CT imaging method, device, equipment and storage medium, which can at least solve the problem of efficiently using X-ray energy to achieve large field of view cone beam CT imaging, and can at least achieve freely changing the positional relationship between the emitting device and the receiving device relative to the scanning center around which the rotational movement occurs without changing the hardware equipment (such as a collimator) to efficiently use X-ray energy and achieve large field of view cone beam CT imaging.

[0004] To solve the above technical problems, at least one embodiment of the present application provides a large field of view cone beam CT imaging method, which is implemented based on an image-guided radiotherapy system. The image-guided radiotherapy system includes a main robotic arm and an auxiliary robotic arm. A emitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm. The large field of view cone beam CT imaging method includes: driving the emitting device and the receiving device respectively by the main robotic arm and the auxiliary robotic arm to scan a target around a scanning center according to a preset scanning path, obtaining two sets of scanning data. During the scanning process, the emitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the emitting device is always perpendicular to the center of the receiving device. The preset scanning path includes a first sub-scanning path and a second sub-scanning path. The first sub-scanning path includes the center of the emitting device deflecting a preset angle in a preset direction from the direction pointing from the center of the cone-shaped imaging beam to the scanning center and then rotating along a set trajectory. The second sub-scanning path includes the center of the emitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scanning path and then rotating in the opposite direction along the set trajectory. Combining the scanning data when the center of the emitting device in the two sets of scanning data is in the same position to obtain a combined projection result; performing back-projection reconstruction according to the combined projection results when the center of the emitting device is in different positions.

[0005] At least one embodiment of the present application further provides a large field of view cone beam CT imaging device, which is implemented based on an image-guided radiotherapy system. The image-guided radiotherapy system includes a main robotic arm and an auxiliary robotic arm. A transmitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm. The large field of view cone beam CT imaging device includes: a rotation scanning control module, configured to drive the transmitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan a target around a scanning center according to a preset scanning path to obtain two sets of scanning data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device. The preset scanning path includes a first sub-scanning path and a second sub-scanning path. The first sub-scanning path includes that the center of the transmitting device deflects a preset angle in a preset direction from the direction from the center of the cone-shaped imaging beam to the scanning center and then rotates along a set trajectory. The second sub-scanning path includes that the center of the transmitting device deflects a preset angle in the opposite direction of the preset direction at the end position of the first sub-scanning path and then rotates reversely along the set trajectory. A scanning data combination module, configured to combine the scanning data when the center of the transmitting device in the two sets of scanning data is in the same position to obtain a combined projection result. A back-projection reconstruction module, configured to perform back-projection reconstruction according to the combined projection results when the center of the transmitting device is in different positions.

[0006] At least one embodiment of the present application further provides an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor. Wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the above-mentioned large field of view cone beam CT imaging method.

[0007] At least one embodiment of the present application further provides a computer-readable storage medium, storing a computer program, and when the computer program is executed by a processor, the above-mentioned large field of view cone beam CT imaging method is implemented.

[0008] The large field of view cone beam CT imaging method provided by the embodiments of the present application utilizes an image-guided radiotherapy system with dual robotic arms. The main robotic arm and the auxiliary robotic arm drive the emission device and the reception device to rotate synchronously around the scanning center respectively. After the center of the emission device deflects a preset angle in the first direction, it rotates along a set trajectory and then the center of the emission device deflects 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scanning path and rotates reversely along the set trajectory, obtaining two sets of scanning data for forming a large field of view. The scanning data obtained by scanning with the center of the emission device at the same position is combined to achieve scanning sorting, and then back-projection reconstruction is performed using the combined data, and the large field of view reconstruction result obtained for the target can be obtained. Compared with the large field of view imaging scheme in the prior art, by controlling the main robotic arm and the auxiliary robotic arm with dual robotic arms to drive the emission device and the reception device to rotate synchronously around the scanning center, the center of the cone imaging beam is always perpendicular to the center of the reception device, without the need to change hardware devices (such as beam limiters), and the positional relationship between the emission device and the reception device relative to the scanning center around which the rotational movement occurs can be freely changed, efficiently utilizing X-ray energy to achieve large field of view cone beam CT imaging.

[0009] In some alternative embodiments, the preset angle is half of the fan angle. To improve the large field of view imaging effect, the center of the emission device deflects from the direction from the center of the cone imaging beam to the scanning center to both sides, and the deflection angles on both sides are set to half of the fan angle, so that the two sets of scanning data obtained when the center of the emission device is at different positions cover the maximum field of view angle after combination.

[0010] In some alternative embodiments, combining the scanning data with the center of the emission device at the same position in the two sets of scanning data includes: using a virtual reception device to combine the projection images respectively corresponding to the scanning data with the center of the emission device at the same position in the two sets of scanning data to obtain a combined projection result. The position of the virtual reception device is determined based on the position of the reception device in the first projection space and the position of the reception device in the second projection space. The first projection space is the projection space formed when the center of the emission device is at any position on the first sub-scanning path, and the second projection space is the projection space formed when the center of the emission device is at this position on the second sub-scanning path. By using the virtual reception device to combine the two projection images corresponding to the same position in the two sets of scanning data, the large field of view reconstruction can be simplified to a reconstruction process similar to that of a small field of view.

[0011] In some alternative embodiments, a virtual receiving device is utilized to combine two projection images respectively corresponding to the scan data with the center of the transmitting device in the same position in the two sets of scan data, and a combined projection result is obtained, including: directly mapping each pixel point in the projection images corresponding to the first projection space and the second projection space onto the virtual receiving device to obtain a first mapping result; or, setting pixel positions with equidistant distribution on the virtual receiving device and inversely mapping them to the projection images corresponding to the first projection space and the second projection space according to the pixel positions to obtain a second mapping result; splicing the two projection images in the first mapping result or the second mapping result to obtain a combined projection result, and processing the overlapping area in a weighted fusion manner during splicing. This means of pixel sorting before back-projection reconstruction makes the pixels corresponding to the actual receiving device correspond one by one with the virtual receiving device, or, setting pixel positions with equidistant distribution on the virtual receiving device and then inversely mapping these pixel positions to the projection images of the actual receiving device. In this way, pixel sorting can be achieved, accurate reconstruction positions can be obtained, and thus accurate back-projection reconstruction results can be obtained.

[0012] In some alternative embodiments, the back-projection reconstruction includes filtered back-projection reconstruction.

[0013] In some alternative embodiments, the large field of view cone beam CT imaging method further includes: driving the emission device and the reception device respectively by the main robotic arm and the auxiliary robotic arm to scan a geometric phantom placed at the scan center around the scan center according to a preset scan path, obtaining two sets of scan data. During the scanning process, the emission device and the reception device move synchronously so that the center of the conical imaging beam emitted by the emission device is always perpendicular to the center of the reception device; the preset scan path includes a first sub-scan path and a second sub-scan path. The first sub-scan path includes the center of the emission device deflecting a preset angle in a preset direction from the direction pointing from the center of the conical imaging beam to the scan center and then rotating along a set trajectory. The second sub-scan path includes the center of the emission device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scan path and then rotating in the opposite direction along the set trajectory; combining the scan data when the center of the emission device in the two sets of scan data is at the same position to obtain a combined projection result; calculating projection matrices at different positions according to the combined projection results and the coordinates on the geometric phantom when the center of the emission device is at different positions, and determining the projection matrices at different positions as the geometric relationships at different positions. By scanning the geometric phantom in the same scanning manner as the real target scanning reconstruction before the real target scanning reconstruction, two sets of scan data are obtained. The scan data when the center of the emission device is at the same position are combined to obtain a combined projection result. Combining with the coordinates on the geometric phantom, the projection matrix representing the geometric relationships at different positions can be calculated, and this projection matrix provides an accurate determination of the projection path during back-projection reconstruction.

[0014] In some alternative embodiments, back-projection reconstruction is performed according to the combined projection results and the geometric relationships when the center of the emission device is at different positions. By pre-calculating the geometric relationships, the emission center and the reception center can be accurately determined, and the geometric relationships of the reconstructed phantom can be obtained, improving the reconstruction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] One or more embodiments are illustrated by way of example in the accompanying drawings, and these exemplary illustrations do not constitute a limitation on the embodiments.

[0016] Figure 1 is a schematic diagram of the large field of view scanning imaging principle of industrial CT in the prior art; Figure 2 is a schematic diagram of the geometric layout of normal scanning of medical cone beam CT in the prior art; Figure 3 is a schematic diagram of the geometric layout of large field of view scanning of medical cone beam CT after translating the flat panel detector in the prior art; Figure 4It is a flowchart of a large field of view cone beam CT imaging method provided by an embodiment of the present application; Figure 5 It is a schematic diagram of an image-guided radiotherapy system provided by an embodiment of the present application; Figure 6 It is a schematic diagram of the positional relationship where the transmitting device is below and the receiving device is above; Figure 7 It is Example 1 of the path between the center of the transmitting device and the center of the receiving device provided by an embodiment of the present application; Figure 8 It is a schematic diagram of large field of view imaging scanning provided by an embodiment of the present application; Figure 9 It is Example 2 of the path between the center of the transmitting device and the center of the receiving device provided by an embodiment of the present application; Figure 10 It is Example 3 of the path between the center of the transmitting device and the center of the receiving device provided by an embodiment of the present application; Figure 11 It is a schematic diagram of the positional relationship among the tube center, the flat panel detector center, and the line connecting their centers at a typical position provided by an embodiment of the present application, where (a) and (b) respectively correspond to Figure 9 the positional relationship among the tube center, the flat panel detector center, and the line connecting their centers at a typical position in Example 2 of the path in Figure 10 the positional relationship among the tube center, the flat panel detector center, and the line connecting their centers at a typical position in Example 3 of the path in; Figure 12 It is a schematic diagram of a virtual receiving device provided by an embodiment of the present application; Figure 13 It is a schematic diagram of mapping each pixel point on the real receiving device to the virtual receiving device provided by an embodiment of the present application; Figure 14 It is provided by an embodiment of the present application Figure 13 a simplified example; Figure 15 It is a schematic diagram of inverse mapping on the real flat panel detector provided by an embodiment of the present application; Figure 16 It is a schematic diagram of a large field of view cone beam CT imaging device provided by an embodiment of the present application. Detailed implementation manners

[0017] To solve the above technical problem of efficiently using X-ray energy to achieve large field of view cone beam CT imaging, the present invention proposes a large field of view cone beam CT imaging method. The implementation details of the large field of view cone beam CT imaging method in this embodiment are specifically described below. The following content is only for facilitating the understanding of the implementation details provided by the present invention.

[0018] Embodiment 1: The large field of view cone beam CT imaging method of this embodiment can be applied to an electronic device with communication, computing, and data storage capabilities. This large field of view cone beam CT imaging method is implemented based on an image-guided radiotherapy system. The image-guided radiotherapy system includes a main robotic arm and an auxiliary robotic arm. A transmitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm. The specific process of the large field of view cone beam CT imaging method of this embodiment can be as Figure 4 shown, including: Step 101, drive the transmitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan the target around the scanning center according to a preset scanning path to obtain two sets of scanning data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device.

[0019] Specifically, the preset scanning path includes a first sub-scanning path and a second sub-scanning path. The first sub-scanning path includes the center of the transmitting device deflecting a preset angle in a preset direction from the direction from the center of the cone-shaped imaging beam to the scanning center and then rotating along a set trajectory. The second sub-scanning path includes the center of the transmitting device deflecting 2 times the preset angle in the reverse direction of the preset direction at the end position of the first sub-scanning path and then rotating in the reverse direction along the set trajectory.

[0020] In some specific implementations, the preset direction includes the clockwise direction or the counterclockwise direction. After the center of the transmitting device deflects 1 / 2 of the fan angle in the clockwise direction from the direction from the center of the cone-shaped imaging beam to the scanning center, it rotates 180° plus the fan angle around the scanning center along the set trajectory. At the current position, the center of the transmitting device then deflects the fan angle in the counterclockwise direction and rotates 180° plus the fan angle along the set trajectory in the reverse direction to obtain two sets of scanning data for forming a large field of view. The combination of the two sets of scanning data can cover a larger field of view angle and achieve large field of view cone beam CT imaging. It should be understood that it is okay for the center of the transmitting device to deflect to the clockwise side or the counterclockwise side first in the two sub-scanning paths. Since the set trajectory is determined, only the deflection directions of the center of the transmitting device in the two sub-scanning paths are different, and the actual large field of view imaging result is not affected.

[0021] In some specific implementations, the preset angle is half of the fan angle. In order to improve the large field of view imaging effect, the angle of deflection of the preset center of the transmitting device is set to half of the fan angle, so that the combination of the two sets of scanning data obtained when the center of the transmitting device is at different positions covers the maximum field of view angle.

[0022] In some examples, starting from the initial scanning position, the first sub-scanning path and the second sub-scanning path are executed in sequence. That is, at the initial scanning position, the center of the cone-shaped imaging beam emitted from the center of the emitting device points to the scanning center. According to the first sub-scanning path, the center of the emitting device deflects 1 / 2 fan angle in the clockwise (counterclockwise) direction from the direction where the center of the cone-shaped imaging beam points to the scanning center, and then rotates 180° plus the fan angle along the set trajectory. At the current position, the center of the emitting device deflects the fan angle in the counterclockwise (clockwise) direction and then rotates 180° plus the fan angle along the reverse direction of the set trajectory, obtaining two sets of scanning data corresponding to the two sub-scanning paths. It should be understood that the center of the emitting device deflects to the opposite sides in the two sub-scanning paths, only changing the emission direction of the cone-shaped imaging beam, and does not change the position of the center of the emitting device. In practical applications, the center of the emitting device needs to move along the set trajectory to continuously change the position of the center of the emitting device for scanning. Therefore, the center of the emitting device performs the above-mentioned scanning of the target around the scanning center according to the preset scanning path to obtain two sets of scanning data.

[0023] When precisely positioning a tumor before radiotherapy, the size of the reconstructed volume is limited by the size of the imaging device. In some scenarios, a reconstructed volume with a larger field of view is required, such as chest and abdomen imaging. A larger field of view can also obtain better registration results. Therefore, this embodiment provides a scheme for large-field cone-beam CT imaging based on a dual robotic arm. Specifically, the main robotic arm and the auxiliary robotic arm drive the emitting device and the receiving device respectively, and scan the target around the scanning center according to the first sub-scanning path and the second sub-scanning path respectively to obtain two sets of scanning data. During the scanning process, the positional relationship between the emitting device and the receiving device relative to the scanning center around which the rotational movement occurs is freely changed, so that the emitting device and the receiving device move synchronously to make the center of the cone-shaped imaging beam emitted by the emitting device always perpendicular to the center of the receiving device. Without changing the hardware device (such as a beam limiter), the X-ray energy can be efficiently utilized. By deflecting the center of the emitting device by a preset angle in the preset direction and then the emitting device and the receiving device rotating 180° plus the fan angle along the set trajectory around the scanning center, and then deflecting the center of the emitting device by 2 times the preset angle in the opposite direction of the preset direction and then the emitting device and the receiving device rotating 180° plus the fan angle along the reverse direction of the set trajectory, two sets of scanning data are formed. After combining these two sets of data, large-field cone-beam CT imaging can be achieved. The deflection of the center of the emitting device on the two sub-scanning paths can form two projection spaces symmetrical about the direction where the center of the cone-shaped imaging beam points to the scanning center at the same position on the set trajectory, thereby forming large-field cone-beam CT imaging.

[0024] Step 102: Combine the scanning data when the center of the emitting device in the two sets of scanning data is in the same position to obtain a combined projection result.

[0025] Step 103, perform back-projection reconstruction based on the combined projection results when the center of the emission device is at different positions.

[0026] The large-field cone-beam CT imaging method provided in this embodiment uses an image-guided radiotherapy system with a dual robotic arm. The main robotic arm and the auxiliary robotic arm drive the emission device and the reception device to rotate synchronously around the scanning center. The center of the emission device deflects a preset angle in the preset direction from the direction pointing from the center of the cone-shaped imaging beam to the scanning center, and then rotates along a set trajectory. The center of the emission device then deflects 2 times the preset angle in the opposite direction of the preset direction and rotates along the opposite direction of the set trajectory, obtaining two sets of scan data for forming a large field of view. Combine the scan data obtained when the center of the emission device is at the same position, and perform back-projection reconstruction based on the combined projection results at different positions, then the large-field reconstructed imaging result for the target can be obtained. Compared with the large-field imaging scheme in the prior art, through the flexible control of the dual robotic arm, the main robotic arm and the auxiliary robotic arm drive the emission device and the reception device to rotate synchronously around the scanning center, so that the center of the cone-shaped imaging beam is always perpendicular to the center of the reception device, without the need to change hardware devices (such as a beam limiter), and the positional relationship between the emission device and the reception device relative to the scanning center around which the rotational movement occurs can be freely changed, efficiently utilizing the X-ray energy to achieve large-field cone-beam CT imaging.

[0027] Combining the scan data when the center of the emission device is at the same position in the two sets of scan data to obtain a combined projection result may further include: Step 102a, using a virtual reception device, combine the projection images respectively corresponding to the scan data when the center of the emission device is at the same position in the two sets of scan data. The position of the virtual reception device is determined based on the position of the reception device in the first projection space and the position of the reception device in the second projection space. The first projection space is the projection space formed when the center of the emission device is at any position on the first sub-scan path, and the second projection space is the projection space formed when the center of the emission device is at this position on the second sub-scan path.

[0028] Combining the two projection images respectively corresponding to the scan data at the same position in the two sets of scan data through the virtual reception device to obtain a combined projection result can simplify the large-field reconstruction into a reconstruction process similar to that of a small field of view.

[0029] In some embodiments, using a virtual reception device, combining the projection images respectively corresponding to the scan data when the center of the emission device is at the same position in the two sets of scan data to obtain a combined projection result further includes: Directly map each pixel point in the projection images corresponding to the first projection space and the second projection space onto the virtual receiving device to obtain a first mapping result; or, set equidistantly distributed pixel positions on the virtual receiving device, and inversely map them to the projection images corresponding to the first projection space and the second projection space according to the pixel positions to obtain a second mapping result; Stitch the two projection images in the first mapping result or the second projection result to obtain a combined projection result, and process the overlapping area in a weighted fusion manner during stitching.

[0030] This means of pixel sorting before back-projection reconstruction makes the pixels corresponding to the real receiving device correspond one by one with the virtual receiving device, or set equidistantly distributed pixel positions on the virtual receiving device, and then inversely map these pixel positions to the projection image of the real receiving device. In this way, pixel sorting can be achieved, and accurate reconstruction positions can be obtained, and then accurate back-projection reconstruction results can be obtained.

[0031] In some embodiments, the large field of view cone beam CT imaging method of this embodiment further includes: Drive the emitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan the geometric phantom placed at the scan center around the scan center according to a preset scan path to obtain two sets of scan data. During the scanning process, the emitting device and the receiving device move synchronously so that the center of the conical imaging beam emitted by the emitting device is always perpendicular to the center of the receiving device; the preset scan path includes a first sub-scan path and a second sub-scan path. The first sub-scan path includes the center of the emitting device deflecting a preset angle from the direction pointing from the center of the conical imaging beam to the scan center to a preset direction and then rotating along a set trajectory. The second sub-scan path includes the center of the emitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scan path and then rotating in the opposite direction along the set trajectory; Combine the scan data when the center of the emitting device is in the same position in the two sets of scan data to obtain a combined projection result; and Calculate the projection matrices at different positions according to the combined projection results when the center of the emitting device is at different positions and the coordinates on the geometric phantom, and determine the geometric relationships at different positions by the projection matrices at different positions.

[0032] In a specific implementation, back-projection reconstruction is performed according to the combined projection results when the center of the emitting device is at different positions and the geometric relationships determined in advance by calculation.

[0033] Before scanning and reconstructing the real target, the geometric phantom is scanned in the same scanning manner as the real target to obtain two sets of scanning data. The scanning data with the center of the transmitting device at the same position is combined with the coordinates on the geometric phantom to calculate the projection matrix representing the geometric relationship of different positions. The projection matrix provides accurate determination of the projection path during back-projection reconstruction.

[0034] Embodiment 2: Based on the above embodiments, this embodiment is based on Figure 5 The image-guided radiotherapy system shown implements the method of the aforementioned embodiment, wherein a transmitting device 111 for transmitting a cone-shaped imaging beam is installed at the end of the main robotic arm 11, and a receiving device 121 for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm 12. The transmitting device 111 may be an X-ray tube, and the receiving device 121 may be a flat-panel detector. In some examples, a treatment device 112 is also installed at the end of the main robotic arm 11, and the transmitting device 111 may be installed on the treatment device 112. The two robotic arms rotate synchronously around the scanning center (e.g., the center of the lesion), and while rotating, the tube emits a cone-shaped X-ray beam, and the flat-panel detector receives it synchronously, thereby obtaining multiple projection images. When the scanning angle is greater than 180° plus the fan angle, a cone-beam CT image can be obtained using a reconstruction algorithm. Figure 6 In the positional relationship shown in FIG. 1 , where the transmitting device 111 is at the bottom and the receiving device 121 is at the top, the dotted circle within the coverage range of the conical imaging beam emitted by the center 111 a of the transmitting device 111 represents the size of the cross-section of the reconstructed volume. Figure 7 is the rotation path of the center of the transmitting device 111 and the center of the receiving device 121 ( Figure 6 In order to distinguish the rotation paths of the two, the large arc A0-A1 is the rotation path of the center 111a of the transmitting device 111, and the small arc B0-B1 is the rotation path of the center of the receiving device 121. The two rotate synchronously around the scanning center (the intersection between the two dotted lines). The center 111a of the transmitting device 111 rotates from A0 to A1. Synchronously, the center of the receiving device 121 rotates from B0 to B1. The two are driven by the main robot arm 11 and the auxiliary robot arm 12 respectively. Based on this rotation path, it can be formed Figure 6 The reconstructed volume is represented by the dotted circle. Figure 7 All positions on the two arcs try to ensure that the X-ray beam emitted from the center of the tube passes through the scanning center and reaches the center of the flat-panel detector vertically, which can be achieved through the synchronous motion control of the dual robotic arms. Figure 7 The path shown is only an example. There may be multiple scanning paths in actual applications. As long as the robot arm position is reachable and there is no collision between the robot arms or between the robot arms and other objects, and the rotation angle is greater than 180° plus the fan angle, a cone-beam CT image can be formed.

[0035] In practical applications, it is often necessary to achieve scanning and reconstruction with a larger field of view in order to obtain a reconstructed object of a larger size.

[0036] To form a reconstructed image with a large field of view and make the cross-section of the reconstructed object larger, by utilizing the flexible and free movement and rotation of the robotic arm, with the rotation center and the center of the reconstructed object remaining unchanged, at the starting position of the scan, the X-ray tube first deflects by 1 / 2 fan beam to one side (e.g., in the clockwise direction), and the flat panel detector moves to the corresponding position, ensuring that the center of the beam is perpendicular to the center of the flat panel detector. As shown in the solid triangle area in Figure 8 Then, the X-ray tube deflects by 1 / 2 fan beam to the other side (e.g., in the counterclockwise direction), and the flat panel detector moves to the corresponding position, ensuring that the center of the beam is perpendicular to the center of the flat panel detector. As shown in the dashed triangle area in Figure 8 The solid triangle area and the dashed triangle area in Figure 8 combine to form a large irradiation field, as shown in the solid circle area in Figure 8 The combined irradiation field rotates 180° around the rotation center plus the combined fan angle to form a cone beam CT image with a large field of view.

[0037] To achieve the scanning effect shown in Figure 8 at the starting position of the scan, the X-ray tube first deflects by 1 / 2 fan beam to one side (e.g., from the center of the cone-shaped imaging beam towards the scanning center in the clockwise direction), and the flat panel detector moves to the corresponding position, ensuring that the center of the beam is perpendicular to the center of the flat panel detector. As shown in the solid triangle area in Figure 8 Then, the X-ray tube and the flat panel detector rotate synchronously around the scanning center by 180° plus the fan angle plus the fan angle. Figure 9 is a schematic diagram of the rotation path of the X-ray tube center and the flat panel detector center. For the sake of distinction, let the large arc A0 - A1 be the path of the X-ray tube center, and the small arc B0 - B1 be the path of the flat panel detector center. A0 and B0 are the positions of the X-ray tube center and the flat panel detector center shown in the solid triangle area in Figure 8 The X-ray tube center rotates from A0 to A1. Synchronously, the flat panel detector center rotates from B0 to B1. At all positions on the two arcs, it is ensured as much as possible that the X-ray emitted from the X-ray tube center passes through the scanning center and then reaches the flat panel detector center vertically. This effect can be achieved by controlling the synchronous movement of the robotic arm. Figure 11 In (a) of

[0038] After the previous rotation, the tube further deflects by 1 / 2 fan beam to the other side (e.g., counterclockwise in the direction where the center of the cone imaging beam points to the scanning center), and the flat panel detector moves to its corresponding position, ensuring that the center of the light beam is perpendicular to the center of the flat panel detector. As Figure 8 shown in the dashed triangular area, the tube and the flat panel detector rotate synchronously around the scanning center by 180° plus the fan angle. Figure 10 Figure (b) in is a schematic diagram of another rotation path of the tube center and the flat panel detector center. For the sake of distinction, let the large arc A0 - A1 be the path of the tube center, and the small arc B0 - B1 be the path of the flat panel detector center. A0 and B0 are Figure 8 the positions of the tube center and the flat panel detector center shown in the dashed triangular area. The tube center rotates from A0 to A1, and synchronously, the flat panel detector center moves from B0 to B1. At all positions between the two arcs, it is ensured as much as possible that the X-ray emitted from the tube center passes through the scanning center and then perpendicularly reaches the flat panel detector center. This effect can be achieved by the synchronous movement control of the robotic arm. Figure 11 Figure (b) in shows the positional relationship among the tube center, the flat panel detector center, and the line connecting their centers at three typical positions in the current rotation path. It can be seen that although the tube center and the flat panel detector center are not directly facing the center of the scanned object, the distance between the tube center and the center of the scanned object remains unchanged. The rotation path is still centered on the scanning center, and the same applies to the flat panel detector center, which will not be elaborated here.

[0039] This embodiment also provides the following fast scanning path: First, the tube center first rotates from Figure 9 A0 at Figure 9 to A1 at Figure 9 along an arc path, and the flat panel detector center synchronously rotates from Figure 9 B0 at Figure 9 to B1 at Figure 10 along an arc path; then, the attitude of the tube is rotated and moved nearby through the main and auxiliary robotic arms. The tube center rotates from Figure 10 the attitude of A1 at Figure 9 to A1 at Figure 10 , that is, it deflects by 1 / 2 fan angle to the other side (counterclockwise in the direction where the center of the cone imaging beam points to the scanning center). The flat panel detector center faces Figure 10 B1 in , and the flat panel detector center moves nearby from Figure 10 B1 at Figure 10 to B1 at Figure 10 so that the X-ray emitted from the tube center at Figure 10 A1 at Figure 10B0 thereof; thus, a cone-beam CT scan of a large field of view is completed with this fast scanning path.

[0040] The reconstruction methods of cone-beam CT include direct filtered back-projection reconstruction and sorted back-projection reconstruction. The scanned data obtained by scanning with the tube center at the same position can be combined and then reconstructed by back-projection in one of two ways. The principle of back-projection is to evenly distribute the measured projection values to each point passed through according to their original projection paths. After performing such back-projections of the projection values in each direction, the back-projection images at each angle are then accumulated. Filtered back-projection is to first perform one-dimensional filtering on the projection values and then perform back-projection, which can make the contour of the reconstructed image clearer.

[0041] The key to back-projection reconstruction is to know the projection path, that is, to know the relationship between the coordinates of the reconstructed object and the tube center and the center of the flat-panel detector, which is called the geometric relationship. Therefore, before back-projection reconstruction, the geometric relationship is calculated first, as shown in the following formula.

[0042]

[0043] In the formula, s represents the magnification factor (which is a dimensionless distance weight factor), ([[]] x , y , z ) represents the spatial coordinates of the reconstructed object, ([[]] u , v ) represents the coordinates of the projection image, P represents a 3×4 projection matrix.

[0044] The process of solving the projection matrix is called geometric calibration and can be solved using a geometric phantom. Given the coordinates (x, y, z) of the object points on the phantom and the position coordinates (u, v) of these points on the projection image, the projection matrix is numerically solved. There is a respective projection matrix for each projection angle.

[0045] One implementation of back-projection reconstruction is to traverse the coordinates (x, y, z) of the reconstructed object and calculate the corresponding (u, v) values according to the above formula, V(x, y, z)=F(u, v), where V represents the reconstructed object and F represents the filtered projection image. In the case of direct filtered back-projection reconstruction, if the geometric relationship is slightly deviated, it will cause some reconstruction positions to be superimposed multiple times, and weighted addition needs to be performed, with the total weight being 1.

[0046] In this embodiment, the implementation method of sorted back-projection reconstruction can be adopted. The tube and the flat-panel detector deflect to both sides as shown by the solid triangle and the dashed triangle as Figure 8 shown. The two triangular fields of view are exactly the solid large circle. Compared with Figure 6 , the scanned data at the same position can be combined into a similar Figure 6a circular region, such as Figure 12 shown by the thick solid line in

[0047] Figure 12 is a virtual detector. Thus, the scanning and reconstruction are consistent with the reconstruction process of the traditional small field of view. Figure 8 The position of the virtual receiving device 121a in Figure 8 is determined based on the (real) receiving device position in the first projection space and the (real) receiving device position in the second projection space. The first projection space is the projection space formed when the center of the transmitting device is at any position on the first sub-scanning path (

[0048] the solid triangular region in Figure 13 ), and the second projection space is the projection space formed when the center of the transmitting device is at this position on the second sub-scanning path ( Figure 14 the dashed triangular region in Figure 14 ). The virtual receiving device 121a is the side that forms a new triangle with the two sides representing the real receiving device in the solid triangular region and the dashed triangular region. (1) Given ∠ACD, according to the cosine formula, AD 2 = AC 2 + CD 2 - 2 * AC * CD * cos(∠ACD), the distance of AD can be calculated; (2) According to the sine formula, CD / sin(∠CAE) = AD / sin(∠ACD), ∠CAE can be obtained; (3) Given ∠ACE and ∠CAE, ∠AEC can be obtained. According to the sine formula: CE / sin(∠CAE) = AC / sin(∠AEC), CE can be obtained.

[0049] The above method directly maps the pixel size of the real flat panel detector to the virtual flat panel detector, and one-to-one correspondence is established between the pixels corresponding to the real receiving device and the virtual receiving device. In this way, the pixel distances on the virtual flat panel detector are not equal, and the non-uniform pixel reconstruction calculation may be more complex. Therefore, in order to simplify the reconstruction in this embodiment, equally spaced pixel positions can also be assumed on the virtual flat panel detector, and the pixel values can be obtained by inverse interpolation mapping on the real flat panel detector, such as Figure 15As shown, the dotted line is the connection line between the center of the X-ray tube and the pixels with equal distances on the virtual flat panel detector. Given the length of CE, to find the length of CD, the calculation is similar to the aforementioned solution. This method of sorting pixels before back-projection reconstruction sets the pixel positions of the virtual receiving device to be equally spaced, and then maps these pixel positions backward to the projection image of the real receiving device, so as to obtain the accurate reconstruction position and further obtain the accurate back-projection reconstruction result.

[0050] The scanning and reconstruction process of the method in the foregoing embodiment in this embodiment is as follows: (1) Place a large geometric phantom at the scanning center; (2) Scan the geometric phantom along the fast scanning path to obtain two sets of scanning data; Specifically, the fast scanning path includes: First, the center of the X-ray tube first rotates from Figure 9 A0 along an arc path to Figure 9 A1, and the center of the flat panel detector synchronously rotates from Figure 9 B0 along an arc path to Figure 9 B1; Then, rotate the attitude of the X-ray tube through the main and auxiliary robotic arms and move it nearby. The center of the X-ray tube rotates from Figure 9 the attitude of A1 to Figure 10 the attitude of A1, that is, deflect 1 / 2 fan angle to the other side (the counterclockwise direction of the direction in which the center of the conical imaging beam points to the scanning center). The center of the flat panel detector faces Figure 10 B1 in Figure 9 and the flat panel detector moves nearby from Figure 10 B1 to Figure 10 B1, so that the X-ray emitted by the center of the X-ray tube at Figure 10 A1 is perpendicular to the center of the flat panel detector at Figure 10 B1; Finally, the center of the X-ray tube rotates from Figure 10 A1 along an arc path to Figure 10 A0, and the center of the flat panel detector synchronously rotates from Figure 10 B1 along an arc path to Figure 10 B0; Complete the cone beam CT scan of the large field of view with this fast scanning path.

[0051] (3) Combine the scanning data at the same position of the center of the X-ray tube. It should be understood that the spatial positions of the center of the X-ray tube in these two sets of data are the same but the attitude orientations are different. The scanning data at the same position in the two sets of data correspond to two projection images. Since the distances of the objects on the geometric phantom are known, the two projection images can be synthesized into one image by image stitching. When stitching the images, weighted addition is performed on the overlapping areas. Record the weighted values under different virtual pixels.

[0052] (4) Calculate the geometric relationship: Given the projection image and the object coordinates on the geometric phantom, calculate the projection matrix according to Equation (1).

[0053] (5) Repeat steps (3) and (4) at different tube center positions to obtain the corresponding projection matrices, and the geometric relationship is established.

[0054] (6) Place the scanned object at the scan center and scan the object along the fast scan path to obtain two sets of scan data; (7) Combine the data in the manner of step (3) using the recorded weighting values to quickly combine the data; (8) Perform filtered back-projection reconstruction according to the geometric relationship calculated in step (4); (9) Repeat steps (7) and (8) for the scan data at different tube center positions to complete the reconstruction process.

[0055] Embodiment 3: Another embodiment of the present application relates to a large field of view cone beam CT imaging device. The implementation details of the large field of view cone beam CT imaging device in this embodiment will be specifically described below. The following content is only provided for facilitating understanding of the implementation details of the present invention. The schematic diagram of the large field of view cone beam CT imaging device in this embodiment can be as Figure 16 shown, implemented based on an image-guided radiotherapy system. The image-guided radiotherapy system includes a main robotic arm and an auxiliary robotic arm. A transmitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm. The large field of view cone beam CT imaging device includes a rotation scan control module 301, a scan data combination module 302, and a back-projection reconstruction module 303; The rotation scan control module 301 is used to drive the transmitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan the target around the scan center along a preset scan path to obtain two sets of scan data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device. The preset scan path includes a first sub-scan path and a second sub-scan path. The first sub-scan path includes the center of the transmitting device deflecting a preset angle in the preset direction from the direction pointing from the center of the cone-shaped imaging beam to the scan center and then rotating along a set trajectory. The second sub-scan path includes the center of the transmitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scan path and then rotating in the opposite direction along the set trajectory. It should be understood that deflecting the preset angle on both sides of the direction from the center of the transmitting device to the direction pointing from the center of the cone-shaped imaging beam to the scan center only changes the emission direction of the cone-shaped imaging beam and does not change the position of the center of the transmitting device. In actual applications, it is necessary to continuously change the position of the center of the transmitting device for scanning. Therefore, the center of the transmitting device performs the above-mentioned scanning of the target around the scan center along the preset scan path to obtain two sets of scan data.

[0056] The scan data combination module 302 is configured to combine the scan data when the centers of the emission devices in two sets of scan data are at the same position, so as to obtain a combined projection result.

[0057] The back-projection reconstruction module 303 is configured to perform back-projection reconstruction according to the combined projection results when the centers of the emission devices are at different positions.

[0058] In some specific implementations, the preset direction includes the clockwise direction or the counterclockwise direction. After the center of the emission device deflects by 1 / 2 fan angle from the center of the cone-shaped imaging beam pointing to the scan center in the clockwise direction, it rotates 180° plus the fan angle along the set trajectory around the scan center. At the current position, the center of the emission device then deflects by the fan angle in the counterclockwise direction and rotates 180° plus the fan angle along the set trajectory in the reverse direction, so as to obtain two sets of scan data for forming a large field of view. The combination of the two sets of scan data can cover a larger field of view angle, realizing large-field-of-view cone-beam CT imaging. It should be understood that it is acceptable for the center of the emission device in the two sub-scan paths to deflect to the clockwise side or the counterclockwise side first. Since the set trajectory is determined, only the deflection directions of the centers of the emission devices in the two sub-scan paths are different, and the actual large-field-of-view imaging result is not affected.

[0059] In some specific implementations, the preset angle is half of the fan angle. In order to improve the large-field-of-view imaging effect, the preset deflection angle of the center of the emission device is set to half of the fan angle, so that the combination of the two sets of scan data obtained when the centers of the emission devices are at different positions covers the maximum field of view angle.

[0060] In some examples, starting from the scan initial position, the first sub-scan path and the second sub-scan path are executed in sequence. That is, at the scan initial position, the center of the cone-shaped imaging beam emitted by the center of the emission device points to the scan center. According to the first sub-scan path, after the center of the emission device deflects by 1 / 2 fan angle from the center of the cone-shaped imaging beam pointing to the scan center in the clockwise direction (counterclockwise direction) and then rotates 180° plus the fan angle along the set trajectory, at the current position, the center of the emission device deflects by the fan angle in the counterclockwise direction (clockwise direction) and rotates 180° plus the fan angle along the reverse direction of the set trajectory, so as to obtain two sets of scan data corresponding to the two sub-scan paths. It should be understood that the centers of the emission devices in the above two sub-scan paths deflect to the opposite sides in opposite directions, which only changes the emission direction of the cone-shaped imaging beam and does not change the position of the center of the emission device. In practical applications, the center of the emission device needs to move along the set trajectory to continuously change the position of the center of the emission device for scanning. Therefore, the center of the emission device performs the above-mentioned scanning of the target around the scan center according to the preset scan path to obtain two sets of scan data.

[0061] When precisely positioning the tumor before radiotherapy, the size of the reconstructed volume is restricted by the size of the imaging device. In some scenarios, a reconstructed volume with a larger field of view is required, such as in chest and abdomen imaging. Moreover, a larger field of view can also yield better registration results. Therefore, this embodiment provides a solution for large-field cone-beam CT imaging based on a dual robotic arm. Specifically, the main robotic arm and the auxiliary robotic arm drive the emission device and the reception device respectively, and scan the target around the scan center along the first sub-scan path and the second sub-scan path respectively to obtain two sets of scan data. During the scanning process, the positional relationship between the emission device and the reception device relative to the scan center around which the rotational movement occurs is freely changed, enabling the emission device and the reception device to move synchronously so that the center of the conical imaging beam emitted by the emission device is always perpendicular to the center of the reception device. Without changing the hardware device (such as a collimator), the X-ray energy can be efficiently utilized. After deflecting the center of the emission device by a preset angle in a preset direction, the emission device and the reception device rotate 180° plus the fan angle along a set trajectory around the scan center, and then after deflecting the center of the emission device by 2 times the preset angle in the opposite direction of the preset direction, the emission device and the reception device rotate 180° plus the fan angle along the opposite direction of the set trajectory around the scan center to form two sets of scan data. The combination of these two sets of data can achieve large-field cone-beam CT imaging. The deflection of the center of the emission device on the two sub-scan paths can form two projection spaces with the direction in which the center of the conical imaging beam points to the scan center as the axis of symmetry at the same position on the set trajectory, thereby forming large-field cone-beam CT imaging.

[0062] The large-field cone-beam CT imaging device provided in this embodiment utilizes an image-guided radiotherapy system with a dual robotic arm. The main robotic arm and the auxiliary robotic arm drive the emission device and the reception device respectively to rotate synchronously around the scan center. After deflecting the center of the emission device by a preset angle from the direction in which the center of the conical imaging beam points to the scan center in a preset direction and then rotating along a set trajectory, the center of the emission device is then deflected by 2 times the preset angle in the opposite direction of the preset direction and rotated along the opposite direction of the set trajectory to obtain two sets of scan data for forming a large field of view. The scan data obtained by scanning with the center of the emission device in the same position is combined, and back-projection reconstruction is performed based on the combined projection results at different positions, thereby obtaining a large-field reconstructed imaging result for the target. Compared with the large-field imaging solutions in the prior art, through the flexible control of the dual robotic arm, the main robotic arm and the auxiliary robotic arm drive the emission device and the reception device respectively to rotate synchronously around the scan center, ensuring that the center of the conical imaging beam is always perpendicular to the center of the reception device. There is no need to change the hardware device (such as a collimator), and the positional relationship between the emission device and the reception device relative to the scan center around which the rotational movement occurs can be freely changed, efficiently utilizing the X-ray energy to achieve large-field cone-beam CT imaging.

[0063] Combining the scan data when the centers of the emitting devices in two sets of scan data are in the same position to obtain a combined projection result may further include: using a virtual receiving device to combine the projection images respectively corresponding to the scan data when the centers of the emitting devices in two sets of scan data are in the same position to obtain a combined projection result, where the position of the virtual receiving device is determined based on the position of the receiving device in the first projection space and the position of the receiving device in the second projection space. The first projection space is the projection space formed when the center of the emitting device is at any position on the first sub-scan path, and the second projection space is the projection space formed when the center of the emitting device is at this position on the second sub-scan path.

[0064] By using a virtual receiving device to combine the two projection images respectively corresponding to the scan data at the same position in two sets of scan data, the large-field-of-view reconstruction can be simplified to a reconstruction process similar to that of a small field of view.

[0065] In some embodiments, using a virtual receiving device to combine the projection images respectively corresponding to the scan data when the centers of the emitting devices in two sets of scan data are in the same position to obtain a combined projection result further includes: Directly mapping each pixel point in the projection images corresponding to the first projection space and the second projection space to the virtual receiving device to obtain a first mapping result; or, setting equidistantly distributed pixel positions on the virtual receiving device and inversely mapping them to the projection images corresponding to the first projection space and the second projection space to obtain a second mapping result; Stitching the two projection images in the first mapping result or the second projection result to obtain a combined projection result, and processing the overlapping area in a weighted fusion manner during stitching.

[0066] This means of pixel sorting before back-projection reconstruction makes the pixels corresponding to the real receiving device correspond one by one with the virtual receiving device, or, setting equidistantly distributed pixel positions on the virtual receiving device and then inversely mapping these pixel positions to the projection images of the real receiving device, so as to achieve pixel sorting. In this way, accurate reconstruction positions can be obtained, and then accurate back-projection reconstruction results can be obtained.

[0067] In some embodiments, the large-field-of-view cone-beam CT imaging device further includes a geometric relationship calculation module for: The main robotic arm and the auxiliary robotic arm drive the transmitting device and the receiving device respectively, and scan the geometric phantom placed at the scanning center around the scanning center according to a preset scanning path to obtain two sets of scanning data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the conical imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device; the preset scanning path includes a first sub-scanning path and a second sub-scanning path. The first sub-scanning path includes the center of the transmitting device deflecting a preset angle in a preset direction from the direction where the center of the conical imaging beam points to the scanning center and then rotating along a set trajectory. The second sub-scanning path includes the center of the transmitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scanning path and then rotating in the opposite direction along the set trajectory; combine the scanning data when the center of the transmitting device is in the same position in the two sets of scanning data to obtain a combined projection result; and According to the combined projection results when the center of the transmitting device is in different positions and the coordinates on the geometric phantom, calculate the projection matrices at different positions, and determine the geometric relationships at different positions with the projection matrices at different positions.

[0068] In a specific implementation, back-projection reconstruction is performed according to the combined projection results when the center of the transmitting device is in different positions and the geometric relationships determined by the foregoing calculations in advance.

[0069] Before the scanning reconstruction of the real target, the geometric phantom is scanned in the same scanning manner as the scanning reconstruction of the real target to obtain two sets of scanning data. By combining the scanning data when the center of the transmitting device is in the same position with the coordinates on the geometric phantom, the projection matrix representing the geometric relationships at different positions can be calculated. This projection matrix provides an accurate determination of the projection path during back-projection reconstruction.

[0070] It is worth mentioning that each module involved in this embodiment is a logic module. In practical applications, a logic unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. In addition, to highlight the innovative part of this application, units not closely related to solving the technical problems proposed in this application are not introduced in this embodiment, but this does not mean that there are no other units in this embodiment.

[0071] Embodiment 4: Another embodiment of this application relates to an electronic device, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the large field of view cone beam CT imaging method in the foregoing embodiments.

[0072] Among them, the memory and the processor are connected in a bus manner. The bus can include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors and the memory together. The bus can also connect various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art, and thus will not be further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single component or multiple components, such as multiple receivers and transmitters, and provides a unit for communicating with various other devices on the transmission medium. The data processed by the processor is transmitted on the wireless medium through the antenna. Further, the antenna also receives data and transmits the data to the processor.

[0073] The processor is responsible for managing the bus and general processing, and can also provide various functions, including timing, peripheral interface, voltage regulation, power management, and other control functions. The memory can be used to store the data used by the processor when executing operations.

[0074] Embodiment Five: Another embodiment of the present application relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the above-mentioned embodiments of the large field of view cone beam CT imaging method.

[0075] That is, those skilled in the art can understand that all or part of the steps of implementing the above-mentioned embodiment methods can be completed by instructing relevant hardware through a program. The program is stored in a storage medium, including several instructions for causing a device (which can be a single-chip microcomputer, a chip, etc.) or a processor to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0076] Those of ordinary skill in the art can understand that the above-mentioned embodiments are specific embodiments for implementing the present application, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. A large field of view cone beam CT imaging method, implemented based on an image-guided radiotherapy system, the image-guided radiotherapy system comprising a main robotic arm and an auxiliary robotic arm, characterized in that, A transmitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm; The large field of view cone beam CT imaging method includes: Driving the transmitting device and the receiving device by the main robotic arm and the auxiliary robotic arm respectively, and scanning the target around the scanning center according to a preset scanning path to obtain two sets of scanning data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device; the preset scanning path includes a first sub-scanning path and a second sub-scanning path. The first sub-scanning path includes the center of the transmitting device deflecting a preset angle in a preset direction from the direction where the center of the cone-shaped imaging beam points to the scanning center and then rotating along a set trajectory. The second sub-scanning path includes the center of the transmitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scanning path and then rotating in the opposite direction along the set trajectory; Combining the scanning data when the centers of the transmitting devices in the two sets of scanning data are in the same position to obtain a combined projection result; Performing back-projection reconstruction according to the combined projection results when the centers of the transmitting devices are in different positions.

2. The large field of view cone beam CT imaging method according to claim 1, characterized in that The preset angle is half of the fan angle.

3. The large field of view cone beam CT imaging method according to claim 1, wherein Combining the scanning data when the centers of the transmitting devices in the two sets of scanning data are in the same position includes: Using a virtual receiving device to combine the projection images corresponding to the scanning data when the centers of the transmitting devices in the two sets of scanning data are in the same position to obtain a combined projection result; the position of the virtual receiving device is determined based on the position of the receiving device in the first projection space and the position of the receiving device in the second projection space. The first projection space is the projection space formed when the center of the transmitting device is at any position on the first sub-scanning path, and the second projection space is the projection space formed when the center of the transmitting device is at this position on the second sub-scanning path.

4. The large field of view cone beam CT imaging method according to claim 3, characterized in that, Using a virtual receiving device to combine the projection images corresponding to the scanning data when the centers of the transmitting devices in the two sets of scanning data are in the same position to obtain a combined projection result includes: Directly mapping each pixel point in the projection images corresponding to the first projection space and the second projection space to the virtual receiving device to obtain a first mapping result; or, setting equidistantly distributed pixel positions on the virtual receiving device and inversely mapping them to the projection images corresponding to the first projection space and the second projection space to obtain a second mapping result; Stitching the two projection images in the first mapping result or the second projection result to obtain a combined projection result. When stitching, the overlapping area is processed in a weighted fusion manner.

5. The large field of view cone beam CT imaging method according to claim 1, characterized in that, The back-projection reconstruction includes filtered back-projection reconstruction.

6. The large field of view cone beam CT imaging method according to any one of claims 1 to 5, characterized in that It also includes: Drive the transmitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan the geometric phantom placed at the scan center around the scan center according to a preset scan path to obtain two sets of scan data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device; the preset scan path includes a first sub-scan path and a second sub-scan path. The first sub-scan path includes the center of the transmitting device deflecting a preset angle in a preset direction from the direction from the center of the cone-shaped imaging beam to the scan center and then rotating along a set trajectory. The second sub-scan path includes the center of the transmitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scan path and then rotating in the opposite direction along the set trajectory; Combine the scan data when the center of the transmitting device in the two sets of scan data is in the same position to obtain a combined projection result; According to the combined projection results when the center of the transmitting device is in different positions and the coordinates on the geometric phantom, calculate the projection matrices in different positions, and determine the geometric relationships in different positions with the projection matrices in different positions.

7. The large field of view cone beam CT imaging method according to claim 6, wherein Perform back-projection reconstruction according to the combined projection results when the center of the transmitting device is in different positions and the geometric relationships.

8. A large field of view cone beam CT imaging device, implemented based on an image-guided radiotherapy system, the image-guided radiotherapy system including a main robotic arm and an auxiliary robotic arm, characterized in that, A transmitting device for emitting a cone-shaped imaging beam is installed at the end of the main robotic arm, and a receiving device for receiving the cone-shaped imaging beam is installed at the end of the auxiliary robotic arm; The large field of view cone beam CT imaging device includes: A rotation scan control module, which is used to drive the transmitting device and the receiving device respectively through the main robotic arm and the auxiliary robotic arm, and scan the target around the scan center according to a preset scan path to obtain two sets of scan data. During the scanning process, the transmitting device and the receiving device move synchronously so that the center of the cone-shaped imaging beam emitted by the transmitting device is always perpendicular to the center of the receiving device; the preset scan path includes a first sub-scan path and a second sub-scan path. The first sub-scan path includes the center of the transmitting device deflecting a preset angle in a preset direction from the direction from the center of the cone-shaped imaging beam to the scan center and then rotating along a set trajectory. The second sub-scan path includes the center of the transmitting device deflecting 2 times the preset angle in the opposite direction of the preset direction at the end position of the first sub-scan path and then rotating in the opposite direction along the set trajectory; A scan data combination module, which is used to combine the scan data when the center of the transmitting device in the two sets of scan data is in the same position to obtain a combined projection result; A back-projection reconstruction module, which is used to perform back-projection reconstruction according to the combined projection results when the center of the transmitting device is in different positions.

9. An electronic device, characterized in that, Includes: At least one processor; And, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the large field of view cone beam CT imaging method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the large field of view cone beam CT imaging method according to any one of claims 1 to 7.

Images