Method for detecting an offset of a detector, device and medical imaging system

Abstract

The application relates to a detector offset detection method and device and a medical imaging system, wherein the detector offset detection method comprises the following steps: obtaining measured coordinates of a target phantom projected on a detector; determining estimated coordinates of the target phantom projected on the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; and solving the geometric offset of the detector according to the difference between the measured coordinates and the estimated coordinates and the spatial position model between the estimated coordinates and the geometric offset of the detector. The application combines a three-dimensional reconstruction algorithm with an optimization algorithm to accurately solve the geometric offset according to the difference between the measured value and the estimated value of the projection coordinates of the target phantom, and does not need to use high-precision optical equipment, so that the application cost of the geometric correction can be reduced. In addition, periodic correction can be realized in the use process of the medical imaging system, and the hardware cost of the geometric correction is reduced.

Description

Technical Field

[0001] This application relates to the field of medical imaging, and in particular to methods, apparatus and medical imaging systems for detecting detector offset. Background Technology

[0002] Single-photon emission computed tomography (SPECT) systems have high application value due to their system flexibility, large field of view (FOV), and lower cost.

[0003] In a dual-probe SPECT system, the detector and collimator used to acquire the gamma rays emitted from the scanned sample are relatively large in mass, and the design and manufacturing cost of a mechanical structure that ensures the detector remains in its intended position are both high. Therefore, in practical applications of a dual-probe SPECT system, the detector, affected by gravity, will deviate at different projection angles; this deviation includes both angular and spatial displacement. This detector deviation will reduce the reconstruction accuracy and quantitative precision of the SPECT image.

[0004] In related technologies, geometric correction parameters are often determined for each medical imaging system before it leaves the factory, based on high-precision optical equipment. This method is costly and can only achieve geometric correction of the detector before it leaves the factory, which also leads to high mechanical costs for the detector.

[0005] There is currently no effective solution to the problem of high hardware costs for implementing geometric correction in related technologies. Summary of the Invention

[0006] This embodiment provides a detector offset detection method, apparatus, and medical imaging system to address the problem of high hardware costs for geometric correction in related technologies.

[0007] In a first aspect, this embodiment provides a detector offset detection method for a medical imaging system, the method comprising:

[0008] Obtain the measured coordinates of the target phantom projected onto the detector of the medical imaging system;

[0009] Based on the spatial position model, the estimated coordinates of the target phantom projected onto the detector are determined; the spatial position model is obtained by physically modeling the medical imaging system.

[0010] The geometric offset of the detector is determined based on the difference between the measured coordinates and the estimated coordinates.

[0011] In some embodiments, obtaining the measured coordinates of the target phantom projected onto the detector of the medical imaging system includes:

[0012] The medical imaging system is used to scan each target phantom placed in a preset stereo array model to obtain projection data of each target phantom; wherein, the different target phantoms are located in different spatial positions;

[0013] The projection data is fitted to obtain the measured coordinates of the target phantom projected onto the detector.

[0014] In some embodiments, determining the estimated coordinates of the target phantom projected onto the detector based on a spatial location model includes:

[0015] Physical modeling is performed based on the structure of the medical imaging system to determine the mapping relationship between the three-dimensional spatial coordinates of the target phantom and the projection coordinates of the target phantom on the detector, thereby constructing the spatial position model.

[0016] Based on the spatial location model, the estimated coordinates of the detector under different projection angles are obtained.

[0017] In some embodiments, determining the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates includes:

[0018] Based on a preset 3D reconstruction algorithm, the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates is calculated.

[0019] In some embodiments, the 3D reconstruction algorithm is a motion recovery structure algorithm.

[0020] In some embodiments, the method further includes:

[0021] The detector is offset corrected based on the detected geometric offset.

[0022] In some embodiments, the method further includes:

[0023] The geometric offset of the detector is input into a preset medical imaging reconstruction algorithm to obtain the target reconstruction image.

[0024] Secondly, this embodiment provides a detector offset detection device for a medical imaging system, the device comprising: a first acquisition module, a second acquisition module, and a solution module; wherein:

[0025] The first acquisition module is used to acquire the measured coordinates of the target phantom projected onto the detector of the medical imaging system;

[0026] The second acquisition module is used to determine the estimated coordinates of the projection of the target phantom onto the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system.

[0027] The offset determination module is used to determine the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates.

[0028] Thirdly, this embodiment provides a medical imaging system, which includes at least: a detector and a processor;

[0029] The detector is used to collect projection data of the imaging object;

[0030] The processor is used to execute the offset detection method of the detector described in the first aspect above.

[0031] Fourthly, this embodiment provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the offset detection method of the detector described in the first aspect above.

[0032] Fifthly, this embodiment provides a storage medium storing a computer program that, when executed by a processor, implements the detector offset detection method described in the first aspect above.

[0033] Compared with related technologies, this embodiment provides a detector offset detection method, apparatus, and medical imaging system. The detector offset detection method first obtains the measured coordinates of the target phantom projected onto the detector of the medical imaging system. Based on a spatial position model, it determines the estimated coordinates of the target phantom projected onto the detector; this spatial position model is obtained by physically modeling the medical imaging system. Then, based on the difference between the measured and estimated coordinates, it determines the geometric offset of the detector. By accurately solving for the geometric offset based on the difference between the measured and estimated values ​​of the target phantom's projected coordinates, it can be used for detector offset correction without relying on high-precision optical equipment, thus reducing the application cost of geometric correction. Furthermore, it can achieve periodic detection of the geometric offset during the use of the medical imaging system, thereby completing periodic correction, reducing mechanical costs, and consequently, reducing the hardware cost of the medical imaging system.

[0034] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a hardware structure block diagram of the terminal of the detector offset detection method in this embodiment;

[0037] Figure 2 This is a flowchart of the detector offset detection method in this embodiment;

[0038] Figure 3 This is a schematic diagram of the detector offset variables in a computed tomography imaging system;

[0039] Figure 4 This is a schematic diagram of the structure of a three-dimensional array model in this embodiment;

[0040] Figure 5 This is a schematic diagram of the placement of a three-dimensional array model in this embodiment;

[0041] Figure 6 This is a flowchart of a detector offset detection method applied to a SPECT system in some embodiments;

[0042] Figure 7 This is a structural block diagram of the offset detection device of the detector in this embodiment;

[0043] Figure 8 This is a schematic diagram of the medical imaging system in this embodiment. Detailed Implementation

[0044] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0045] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0046] The method embodiments provided in this example can be executed on a terminal, computer, or similar computing device. For example, it can run on a terminal. Figure 1 This is a hardware structure block diagram of the terminal of the detector offset detection method in this embodiment. For example... Figure 1 As shown, the terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 and a memory 104 for storing data are also included. The processor 102 may be, but is not limited to, a microprocessor (MCU) or a programmable logic device (FPGA). The terminal may also include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that… Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the terminal described above. For example, the terminal may also include components that are larger than... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown are illustrated.

[0047] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the detector offset detection method in this embodiment. The processor 102 executes various functional applications and data processing by running the computer programs stored in the memory 104, thereby implementing the above-described method. The memory 104 may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0048] The transmission device 106 is used to receive or send data via a network. This network includes a wireless network provided by the terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 can be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0049] This embodiment provides a detector offset detection method for use in a medical imaging system. Figure 2 This is a flowchart of the detector offset detection method in this embodiment, as follows: Figure 2 As shown, the process includes the following steps:

[0050] Step S210: Obtain the measured coordinates of the target phantom projected onto the detector of the medical imaging system.

[0051] The target phantom can specifically be a geometric phantom used for detector geometric correction, such as a spherical phantom. The size, shape, and material of the target phantom can be predetermined according to the requirements of the actual application scenario. The aforementioned medical imaging system can specifically be a computed tomography imaging system, such as a digital subtraction angiography (DSA) system, a computed tomography (CT) system, or a SPECT system. Specifically, when the application scenario is a DSA or CT system, the target phantom can be a steel sphere; when the application scenario is a SPECT system, the target phantom can be a radioactive source sphere, specifically using the radioactive nuclide Tc-99m as the radioactive source. In the offset correction scenario, on the one hand, the radioactive source sphere can simulate the distribution of radioactivity in the body, more realistically reflecting the imaging conditions of the SPECT system in actual applications; on the other hand, the correction accuracy can be improved based on the clear imaging target provided by the radioactive source sphere.

[0052] In this embodiment, a target phantom can be fixed between the detector and the scanning bed of a medical imaging system. Based on a pre-set scanning protocol, the target phantom is rotated and scanned to obtain its specific coordinates on the detector at different projection angles. The scanning protocol can be any protocol capable of multi-angle rotational scanning; this embodiment does not impose a specific limitation. There can be one or more target phantoms. After the target phantom is fixed, the measured coordinates of its projection on the detector are obtained based on the scanning of the target phantom.

[0053] Step S220: Based on the spatial position model, determine the estimated coordinates of the target phantom projected onto the detector; wherein, the spatial position model is obtained by physically modeling the medical imaging system.

[0054] Based on the structure of this medical imaging system, physical modeling can be used to map the three-dimensional spatial coordinates of the target phantom to its projected coordinates on the detector, resulting in a spatial position model. This spatial position model includes the correspondence between the estimated coordinates and the geometric offset of the detector. Based on this spatial position model, the projected coordinates of the target phantom on the detector are estimated, yielding the estimated coordinates of the target phantom's projection on the detector. These estimated coordinates can be considered as the theoretical coordinates of the target phantom's projection on the detector. It can be understood that the estimated coordinates obtained through the spatial position model can specifically be an expression that includes the projection intrinsic matrix of the medical imaging system, the geometric offset to be solved, and the three-dimensional spatial coordinates of the target phantom.

[0055] Step S230: Determine the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates.

[0056] The aforementioned geometric offset is the offset that occurs during the acquisition of projection data by the detector, and it can be described by six variables. Figure 3 This is a schematic diagram of the detector offset variable in a computed tomography imaging system. (Example) Figure 3 As shown, the computed tomography imaging system includes a detector and a gantry, with the detector fixed to the gantry. The six variables used to describe the geometric offsets are: the detector's rotation along its X-axis, described as pitch; the detector's displacement along its X-axis, described as transX; the detector's rotation along its Y-axis, described as roll; the detector's displacement along its Y-axis, described as transY; the detector's rotation along its Z-axis, described as yaw; and the detector's displacement along its Z-axis, described as transZ. This spatial position model can specifically include the mapping relationship between the estimated coordinates and the geometric offsets. By combining the projection intrinsic matrix and the three-dimensional spatial coordinates of the target phantom, a spatial position model regarding the estimated coordinates and geometric offsets can be obtained.

[0057] Based on the aforementioned spatial location model, a pre-defined minimum value algorithm can be used to construct an objective function for solving the geometric offset. This objective function can include an expression for the difference between the estimated coordinates and the measured coordinates, as well as prior knowledge about various parameters to be solved. In the aforementioned difference expression, the estimated coordinates can be represented by the geometric offset and the projection intrinsic matrix through the aforementioned spatial location model. By solving the objective function, the geometric offset of the detector can be determined. Specifically, the geometric offset can be solved using minimum value algorithms such as least squares, Newton's method, or gradient descent. Furthermore, three-dimensional reconstruction algorithms can be used in the geometric offset process, such as two-dimensional to three-dimensional reconstruction algorithms based on computer vision. Specifically, these can include Structure from Motion (SFM) algorithms, Multi-View Stereo (MVS) algorithms, etc. After constructing the aforementioned objective function, a pre-defined three-dimensional reconstruction algorithm can be used to solve for the geometric offset and the specific three-dimensional coordinates of the target phantom.

[0058] In medical imaging systems, detectors undergo angular and spatial displacement due to gravity during the rotation of the scanned sample to acquire projection data. Take a dual-probe SPECT system as an example. The detectors and collimators used to acquire gamma rays emitted from the scanned sample in a dual-probe SPECT system are relatively large, making the design and manufacturing of a mechanical structure that ensures the gamma ray detector remains in the expected position complex and costly. Furthermore, in practical applications, the scanning protocol of a dual-probe SPECT system typically requires each probe to rotate at least 180 degrees around the scanned sample. Therefore, the detector's displacement varies at different projection angles due to gravity. Ignoring this detector displacement during image reconstruction will reduce the reconstruction accuracy and quantitative precision of the SPECT image. In particular, large detector displacements at different angles can lead to artifacts in the reconstructed SPECT image, thus affecting its interpretation.

[0059] Currently, some SPECT system manufacturers calculate the three-dimensional rotational deformation parameter matrix (i.e., the aforementioned geometric offset) using a high-precision optical system before each imaging system leaves the factory, and consider the impact of these parameters on the reconstruction during quantitative reconstruction. Therefore, the hardware cost for correcting the geometric parameters of a SPECT system is currently high, and correction can only be performed before leaving the factory, rather than periodically correcting for offsets that occur during actual use.

[0060] Furthermore, for X-ray CT systems, due to their higher spatial resolution, detector offset has a greater impact on reconstructed image quality. In some related techniques, cone-beam X-ray CT is used to acquire the projection of a small spherical phantom at different angles. The mechanical correction parameters for the entire CT system are then calculated by comparing the residual between the measured projection and the analytically obtained projection position of the phantom. These mechanical correction parameters include, but are not limited to, detector offset. Alternatively, the mechanical parameters of the CT system can be calculated by analyzing the motion trajectory of the mechanical correction phantom in different projections. It is important to note that the above-mentioned mechanical correction schemes for CT systems often rely on X-ray tubes that can emit cone or fan-beam X-rays. For imaging systems such as SPECT systems that only emit parallel beams such as gamma rays, the above schemes cannot achieve detector offset correction.

[0061] In contrast, steps S210 to S230 above, based on the difference between the measured and estimated coordinates and combined with the spatial position model between the estimated coordinates and the geometric offset, can correct the geometric offset of the detector in the tomographic imaging system caused by gravity and tooling errors. On the one hand, it eliminates the need for a high-precision optical system, thereby reducing hardware costs. On the other hand, this embodiment is not limited to pre-shipment geometric calibration; it can also repeatedly perform periodic calibration of the detector's offset during actual use of the medical imaging system. Furthermore, since this embodiment can achieve geometric calibration of the detector, it reduces the mechanical cost of the tomographic imaging system. In addition, the workflow for solving the entire geometric offset is relatively simple, without registration and transformation between multiple coordinate systems, thus facilitating workflow maintenance and learning.

[0062] Steps S210 to S230 above obtain the measured coordinates of the target phantom projected onto the detector of the medical imaging system. Based on the spatial position model, the estimated coordinates of the target phantom projected onto the detector are determined. This spatial position model is obtained by physically modeling the medical imaging system. The geometric offset of the detector is determined based on the difference between the measured and estimated coordinates. By accurately solving for the geometric offset based on the difference between the measured and estimated values ​​of the target phantom's projected coordinates, the offset can be corrected for the detector without the need for high-precision optical equipment, thus reducing the application cost of geometric correction. Furthermore, it enables periodic detection of the geometric offset during the use of the medical imaging system, thereby completing periodic correction and reducing the mechanical cost of the detector. Consequently, it reduces the hardware cost of implementing geometric correction in the medical imaging system.

[0063] In one embodiment, obtaining the measured coordinates of the target phantom projected onto the detector of the medical imaging system based on step S210 above may include:

[0064] The medical imaging system is used to scan each target phantom placed in the preset stereo array model to obtain the projection data of each target phantom. The different target phantoms are located in different spatial positions. The projection data is fitted to obtain the measured coordinates of the target phantom projected on the detector.

[0065] This 3D array model can be configured with multiple layers of insert plates, each with multiple insertion holes. The spacing between each insertion hole can be set according to the requirements of the actual application scenario. Multiple target phantoms can be staggered and placed in the insertion holes at different positions on different layers of the 3D array model. Figure 4 This is a schematic diagram of a three-dimensional array model according to this embodiment. Figure 4As shown, the three-dimensional array model can be a cube, including a base and multiple layers of insert plates. Each layer has multiple insertion holes spaced apart. When applied to a SPECT system, the target phantom can be a radioactive source sphere. The size of the radioactive source sphere matches the insertion holes. When placing different radioactive source spheres into insertion holes in different layers, the different spheres can maintain a certain spatial distance, without needing to insert a radioactive source sphere into every insertion hole. The specific insertion holes used to hold the radioactive source spheres can be determined based on the requirements of the actual application scenario.

[0066] Figure 5 This is a schematic diagram of the placement of a three-dimensional array model according to this embodiment. Figure 5 As shown, the SPECT system includes a SPECT detector, a SPECT scanning bed, and a SPECT gantry. During the scanning process, the stereo array phantom can be placed on the SPECT scanning bed. During placement, it can be... Figure 5 The left and right sides of the stereo array model are parallel to the direction of movement of the scanning bed (e.g., Figure 5 (As indicated by the black arrow in the image), and there are no precision requirements for parallelism. After placing the three-dimensional array phantom containing the radioactive source spheres on the scanning bed, the SPECT system acquires projection data of the three-dimensional array phantom at different angles within a preset angle range according to a preset SPECT scanning protocol. The aforementioned SPECT scanning protocol is a scanning protocol that enables the detector to acquire projection data from different projection angles.

[0067] By setting up a 3D array model to place each target phantom, the target phantoms can be fixed during the calibration process, thus facilitating the correction of geometric offsets. Furthermore, this embodiment only requires a simple 3D array model to achieve detector geometric calibration, and compared to other geometric calibration schemes in related technologies, the testing cost of this embodiment is also lower.

[0068] Specifically, when fitting the projection data to obtain the measured coordinates of the target phantom projected onto the detector, the projection data can be fitted based on a Gaussian function to obtain the measured coordinates of the target phantom projected onto the detector.

[0069] In this embodiment, firstly, according to a pre-set scanning protocol, projection data of the target phantom at different projection angles is collected within a preset angle range, such as 360 degrees. Then, a Gaussian function is used to fit the collected projection data, thereby obtaining the measured coordinates of the target phantom on the detector at different projection angles. By introducing the Gaussian function, accurate fitting of the projection data can be achieved, thus calculating the accurate measured coordinates of the target phantom on the detector, thereby improving the accuracy of the measured coordinate calculation.

[0070] Furthermore, in one embodiment, based on the above step S210, determining the estimated coordinates of the target phantom projected onto the detector based on the spatial position model may include:

[0071] Physical modeling is performed based on the structure of the medical imaging system to determine the mapping relationship between the three-dimensional spatial coordinates of the target phantom and the projection coordinates of the target phantom on the detector, thus constructing a spatial position model; based on this spatial position model, the estimated coordinates of the detector under different projection angles are obtained.

[0072] Specifically, based on the structure and imaging mechanism of the medical imaging system, a physical model is performed to establish the mapping relationship between the three-dimensional spatial coordinates of the target phantom's position in three-dimensional space and the two-dimensional projection coordinates of the target phantom projected onto the detector. This allows for the estimation of the detector's coordinates at different projection angles. These estimated coordinates are represented by a combination of geometric offsets, the three-dimensional spatial coordinates of the target phantom, and the projection intrinsic matrix of the medical imaging system. The spatial position model can be expressed as follows:

[0073] π m (p i )=K·(R(α m ,β m ,γ m )·p i +T m )=K·(R m ·p i +T m )

[0074] Where, π m (p i ) represents the target p i The estimated coordinates on the detector at the m-th projection angle, i.e., the theoretical coordinates; pi in the formula represents the three-dimensional spatial coordinates of the target phantom; K represents the projection intrinsic matrix of the current imaging system, and all values ​​within this matrix are known quantities; R(α) m ,β m ,γ m (abbreviated as Rm) is the rotation matrix of the detector at the m-th projection angle caused by the deflection of the detector along each axis. The size of this rotation matrix is ​​3x3, where α m Corresponding to the detector's rotation along its own Y-axis, β m Corresponding to the detector's rotation along its own X-axis, γ m This corresponds to the detector's rotation along its own Z-axis; finally, T m Let represent the displacement vector of the detector along each axis at the m-th rotation angle. The size of this displacement vector is 3x1.

[0075] In this embodiment, by physically modeling the medical imaging system, the estimated coordinates of the detector under different projection angles can be determined. Furthermore, the physical model takes into account the geometric offset of the detector, thus providing an accurate theoretical basis for the subsequent solution of the geometric offset and improving the accuracy of the subsequent solution of the geometric offset.

[0076] In one embodiment, based on step S220 above, determining the geometric offset of the detector according to the difference between the measured coordinates and the estimated coordinates may include:

[0077] Based on a pre-defined 3D reconstruction algorithm, the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates is calculated.

[0078] Specifically, based on the spatial position model between the estimated coordinates and the geometric offset described above, an objective function can be constructed using a preset minimum value solution algorithm to find the geometric offset that makes the measured coordinates closest to the estimated coordinates. For example, the following objective function can be constructed based on the least squares method:

[0079]

[0080] in, Represents the rotation matrix at each projection angle; It is the displacement vector; M represents the ideal value of the three-dimensional coordinates of the target phantom; M is the number of projection angles, and N is the number of target phantoms. The objective function on the right-hand side of the equation can be used to obtain R. m Let T be the rotation matrix of the detector at the m-th projection angle caused by the detector's deflection along each axis; m Let q be the displacement vector of the detector along each axis at the m-th rotation angle; im Let P(R,T,p) represent the measured coordinates of the i-th target phantom on the detector at the m-th projection angle. P(R,T,p) represents prior knowledge about the various geometric parameters to be obtained, and β is a preset weight value for this prior knowledge. The value can be an empirical value in the actual application scenario, and the range of the value depends on the coordinates of P(R,T,p) and the acquisition point source. K is the projection intrinsic matrix of the medical imaging system.

[0081] Understandably, the objective function described above can also take other forms, and this embodiment does not impose specific limitations on it. In particular, the minimum value solution algorithm can be the least squares method, combined with the SFM algorithm to solve for the geometric offset. In addition, other algorithms and 3D reconstruction algorithms can be selected according to the needs of the actual application scenario.

[0082] This embodiment utilizes a preset minimum value solving algorithm to solve for the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates. Specifically, it uses a 3D reconstruction algorithm in the field of computer vision to solve for the geometric offset and the specific coordinates of the target phantom in 3D space. Based on this process, the geometric correction of the detector in the medical imaging system can be achieved, reducing the errors caused by the gravity of the detector and the tooling.

[0083] It is worth noting that the offset detection method provided in this embodiment can be applied to different computed tomography imaging systems, such as dual-probe SPECT systems, CT systems, and DSA systems. For different medical imaging systems, the specific form of the aforementioned projection intrinsic matrix K can be set according to the actual situation.

[0084] Specifically, in one embodiment, the 3D reconstruction algorithm is a motion-based structure reconstruction algorithm. The SFM algorithm is an image-based 3D scene reconstruction technique capable of recovering the 3D structure of a scene from image data or other sensor data. When calculating the geometric offset, the SFM algorithm is used to further improve the accuracy of the calculation results by leveraging its high precision and robustness in 3D structure recovery. This enables accurate calibration of the detector's geometric offset, thereby improving the quality and accuracy of subsequent image reconstruction.

[0085] In one embodiment, the offset detection method for the detector may further include:

[0086] The detector is offset corrected based on the detected geometric offset. Specifically, relevant parameters of the computed tomography imaging equipment, such as the detector's position and angle, can be adjusted according to the detected geometric offset to achieve detector offset correction. In this embodiment, detector offset correction is performed based on accurate detector geometric offset, thereby improving the accuracy of medical images.

[0087] Furthermore, in one embodiment, the offset detection method for the detector described above may further include:

[0088] The detector's geometric offset is input into a preset medical imaging reconstruction algorithm to obtain the target reconstructed image. After calculating the detector's geometric offset, it can be input into subsequent medical imaging reconstruction algorithms to reconstruct the medical image. The aforementioned medical imaging reconstruction algorithm varies depending on the medical imaging system and can specifically be a SPECT reconstruction algorithm, a CT reconstruction algorithm, or a DSA reconstruction algorithm.

[0089] By incorporating the solved geometric offset into the medical imaging reconstruction stage, the geometric offset of the detector can be taken into account during image reconstruction, thereby improving the imaging quality and accuracy of the final image.

[0090] Figure 6 This is a flowchart of a detector offset detection method applied to a SPECT system in some embodiments, such as... Figure 6 As shown, the offset detection method of this detector includes the following steps:

[0091] Step S601: Insert the radioactive source sphere into the socket of the 3D array model; wherein, the radioactive source sphere is selected as the target phantom when performing geometric correction on the detector of the SPECT system. Before placing the radioactive source sphere into the socket of the 3D array model, theoretical analysis can be performed according to the needs of the actual application scenario, and the socket to be placed can be pre-selected. Different radioactive source spheres can be placed into different sockets of different layers of the 3D array model.

[0092] Step S602: Place the stereo array model containing the radiation source onto the scanning bed of the SPECT system; during placement, the left and right sides of the stereo array model should be parallel to the direction of movement of the scanning bed as much as possible (no precision requirement).

[0093] Step S603: According to the pre-set SPECT scanning protocol, projected data from different angles is acquired on the stereo array model within a 360-degree range; wherein, the SPECT scanning protocol can be any scanning protocol that enables the detector to acquire projected data within a 360-degree range.

[0094] Step S604: Use a Gaussian function to fit the collected projection data and calculate the measured coordinates of the radioactive source ball on the detector under different projection angles.

[0095] Step S605: Based on the spatial position model obtained by physically modeling the SPECT system, the estimated coordinates of the radioactive source ball on the detector are obtained.

[0096] Step S606 involves using the least squares method combined with the SFM algorithm to solve for the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates. This spatial location model also includes the projection intrinsic matrix of the SPECT system; its specific form can be found in the formulas of the above embodiments, and will not be repeated here. Ideally, the estimated coordinates in step S605 are consistent with the measured coordinates in step S604. However, due to the detector offset and the unknown specific value of the radioactive source sphere in three-dimensional space, the measured coordinates of the radioactive source sphere on the detector will deviate from the estimated coordinates. Therefore, by minimizing the difference between the measured and estimated coordinates, and using the SFM algorithm, the actual geometric offset of the detector and the specific coordinates of the radioactive source sphere in three-dimensional space are determined.

[0097] In step S607, the geometric offset calculated in step S606 is input into the SPECT reconstruction algorithm to obtain the SPECT reconstructed image. In this step, since the detector offset is taken into account, the quality and accuracy of the final SPECT reconstructed image are both high.

[0098] Steps S601 to S607 above, by using optimization algorithms combined with three-dimensional reconstruction algorithms, accurately solve for the geometric offset based on the difference between the measured and estimated values ​​of the projected coordinates of the target phantom, without the need for high-precision optical equipment, thus reducing the hardware cost of geometric correction; in addition, periodic correction can be achieved during the use of medical imaging systems.

[0099] It should be noted that the steps shown in the above flowchart or the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than that shown here. For example, steps S604 and S605.

[0100] This embodiment also provides a detector offset detection device, which is used to implement the above embodiments and preferred embodiments, and will not be repeated as already described. The terms "module," "unit," "subunit," etc., used below can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0101] Figure 7 This is a structural block diagram of the detector offset detection device 70 in this embodiment, which is used in a medical imaging system. Figure 7As shown, the offset detection device 70 of the detector includes: a first acquisition module 72, a second acquisition module 74, and an offset determination module 76; wherein:

[0102] The first acquisition module 72 is used to acquire the measured coordinates of the target phantom projected onto the detector of the medical imaging system; the second acquisition module 74 is used to determine the estimated coordinates of the target phantom projected onto the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; the offset determination module 76 is used to determine the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates.

[0103] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0104] This embodiment also provides a medical imaging system. Figure 8 This is a schematic diagram of the structure of the medical imaging system 80 in this embodiment, as shown below. Figure 8 As shown, the medical imaging system 80 includes at least: a detector 82 and a processor 84; the detector 82 is used to acquire projection data of the imaging object; the processor 84 is used to execute the detector offset detection method provided in any of the above embodiments. It can be understood that, except... Figure 8 In addition to the portion shown, the medical imaging system 80 may also include more structures, such as a scanning bed, gantry, collimator, beam expander, etc.

[0105] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated in this embodiment.

[0106] Furthermore, in conjunction with the detector offset detection method provided in the above embodiments, this embodiment can also provide a storage medium for implementation. This storage medium stores a computer program; when executed by a processor, the computer program implements any of the detector offset detection methods described in the above embodiments.

[0107] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0108] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0109] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0110] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0111] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method for detecting the offset of a detector, characterized in that, For use in a medical imaging system, the method includes: The measured coordinates of the target phantom projected onto the detector of the medical imaging system are obtained; the medical imaging system includes a single-photon emission computed tomography system. Based on the spatial position model, the estimated coordinates of the target phantom projected onto the detector are determined; the spatial position model is obtained by physically modeling the medical imaging system; the spatial position model is expressed as: ； in, Representative target motif The estimated coordinates on the detector at the m-th projection angle; pi represents the three-dimensional spatial coordinates of the target phantom; K represents the projection intrinsic matrix of the medical imaging system, and all values ​​within the projection intrinsic matrix are known quantities; Let be the rotation matrix of the detector at the m-th projection angle, caused by the deflection of the detector along each axis, where the size of the rotation matrix is ​​3×3. Corresponding to the rotation of the detector along its own Y-axis, Corresponding to the rotation of the detector along its own X-axis, This corresponds to the detector's rotation along its own Z-axis; This represents the displacement vector of the detector along each axis at the m-th rotation angle, and the size of the displacement vector is 3×1; The geometric offset of the detector is determined based on the difference between the measured coordinates and the estimated coordinates.

2. The detector offset detection method according to claim 1, characterized in that, The process of obtaining the measured coordinates of the target phantom projected onto the detector of the medical imaging system includes: The medical imaging system is used to scan each target phantom placed in a preset stereo array model to obtain projection data of each target phantom; wherein, the different target phantoms are located in different spatial positions; The projection data is fitted to obtain the measured coordinates of the target phantom projected onto the detector.

3. The detector offset detection method according to claim 1, characterized in that, The step of determining the estimated coordinates of the target phantom projected onto the detector based on the spatial position model includes: Physical modeling is performed based on the structure of the medical imaging system to determine the mapping relationship between the three-dimensional spatial coordinates of the target phantom and the projection coordinates of the target phantom on the detector, thereby constructing the spatial position model. Based on the spatial location model, the estimated coordinates of the detector under different projection angles are obtained.

4. The detector offset detection method according to claim 1, characterized in that, Determining the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates includes: Based on a preset 3D reconstruction algorithm, the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates is calculated.

5. The detector offset detection method according to claim 4, characterized in that, The three-dimensional reconstruction algorithm is a motion recovery structure algorithm.

6. The method for detecting the offset of a detector according to any one of claims 1 to 5, characterized in that, The method further includes: The detector is offset corrected based on the detected geometric offset.

7. The method for detecting the offset of a detector according to any one of claims 1 to 5, characterized in that, The method further includes: The geometric offset of the detector is input into a preset medical imaging reconstruction algorithm to obtain the target reconstruction image.

8. A detector offset detection device, characterized in that, For use in a medical imaging system, the device includes: a first acquisition module, a second acquisition module, and an offset determination module; wherein: The first acquisition module is used to acquire the measured coordinates of the target phantom projected onto the detector of the medical imaging system; the medical imaging system includes a single-photon emission computed tomography system. The second acquisition module is used to determine the estimated coordinates of the target phantom projected onto the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; the spatial position model is represented as: ； in, Representative target motif The estimated coordinates on the detector at the m-th projection angle; pi represents the three-dimensional spatial coordinates of the target phantom; K represents the projection intrinsic matrix of the medical imaging system, and all values ​​within the projection intrinsic matrix are known quantities; Let be the rotation matrix of the detector at the m-th projection angle, caused by the deflection of the detector along each axis, where the size of the rotation matrix is ​​3×3. Corresponding to the rotation of the detector along its own Y-axis, Corresponding to the rotation of the detector along its own X-axis, This corresponds to the detector's rotation along its own Z-axis; This represents the displacement vector of the detector along each axis at the m-th rotation angle, and the size of the displacement vector is 3×1; The offset determination module is used to determine the geometric offset of the detector based on the difference between the measured coordinates and the estimated coordinates.

9. A medical imaging system, characterized in that, The system includes at least: a detector and a processor; The detector is used to collect projection data of the imaging object; The processor is used to execute the offset detection method of the detector according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the offset detection method for the detector according to any one of claims 1 to 7.

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