Detector offset detection method and device and medical imaging system

Abstract

The invention relates to an offset detection method and device of a detector and a medical imaging system.The offset detection method of the detector comprises the steps that actual measurement coordinates of a target motif projected on the detector are obtained, and estimated coordinates of the target motif projected on the detector are determined based on a spatial position model; the spatial position model is obtained by performing physical modeling on the medical imaging system; and solving the geometric offset of the detector according to the difference between the actually measured coordinates and the estimated coordinates and a spatial position model between the estimated coordinates and the geometric offset of the detector. According to the method, an optimization algorithm is combined with a three-dimensional reconstruction algorithm, according to a difference value between a measured value and an estimated value of a projection coordinate of a target motif, accurate solution of geometric offset is realized, and high-precision optical equipment is not needed, so that the application cost of geometric correction can be reduced; in addition, periodic correction can be achieved in the use process of the medical imaging system, and then the hardware cost of geometric correction is reduced.

Description

Technical Field

[0001] The present application relates to the field of medical imaging, and in particular to a detector offset detection method, device and medical imaging system. Background Art

[0002] Single Photon Emission Computed Tomography (SPECT) has high application value due to its system flexibility, large field of view (FOV) and lower price.

[0003] In the dual-probe SPECT system, the detectors and collimators used to collect gamma rays emitted by the scanned samples are both heavy, and the mechanical structure design difficulty and manufacturing cost of a set of mechanical structures that can ensure that the detectors are always in their expected positions are high. Therefore, in the actual application of the dual-probe SPECT system, the detectors are affected by gravity and will have different offsets at different projection angles. The offset includes both angular offset and spatial displacement. The offset of the detector will reduce the reconstruction accuracy and quantitative accuracy of the SPECT reconstructed image.

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

[0005] With regard to the problem of high hardware cost for implementing geometric correction in related technologies, no effective solution has been proposed so far. Summary of the invention

[0006] In this embodiment, a detector offset detection method, device and medical imaging system are provided to solve the problem of high hardware cost for geometric correction in related technologies.

[0007] In a first aspect, a detector offset detection method is provided in this embodiment, which is used in a medical imaging system, and the method includes:

[0008] Acquiring measured coordinates of the target phantom projected on the detector of the medical imaging system;

[0009] Determining estimated coordinates of the projection of the target phantom on the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system;

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

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

[0012] Using the medical imaging system to scan each target phantom placed in a preset three-dimensional array model to obtain projection data of each target phantom; wherein different target phantoms are located at different spatial positions;

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

[0014] In some embodiments, determining the estimated coordinates of the projection of the target phantom on the detector based on the spatial position model includes:

[0015] Performing physical modeling according to the structure of the medical imaging system, determining a mapping relationship between the three-dimensional spatial coordinates of the target phantom and the projection coordinates of the target phantom on the detector, and constructing the spatial position model;

[0016] The estimated coordinates of the detector at different projection angles are obtained according to the spatial position model.

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

[0018] Based on a preset three-dimensional reconstruction algorithm, the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates is solved.

[0019] In some of the embodiments, the three-dimensional reconstruction algorithm is a structure from motion algorithm.

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

[0021] The detector is subjected to offset correction according to the detected geometric offset of the detector.

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

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

[0024] In a second aspect, in this embodiment, a detector offset detection device is provided, which is used in a medical imaging system. The device includes: 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 on 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 on the detector based on the 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 according to the difference between the measured coordinates and the estimated coordinates.

[0028] In a third aspect, a medical imaging system is provided in this embodiment, the system comprising 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 detector offset detection method described in the first aspect above.

[0031] In a fourth aspect, an electronic device is provided in this embodiment, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the detector offset detection method described in the first aspect is implemented.

[0032] In a fifth aspect, in this embodiment, a storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the method for detecting the offset of the detector described in the first aspect is implemented.

[0033] Compared with the related art, the present embodiment provides a detector offset detection method, device and medical imaging system. The detector offset detection method first obtains the measured coordinates of the target phantom projected on the detector of the medical imaging system, and determines the estimated coordinates of the target phantom projected on the detector based on the spatial position model; wherein the spatial position model is obtained by physically modeling the medical imaging system; and then determines the geometric offset of the detector according to the difference between the measured coordinates and the estimated coordinates. It realizes accurate solution of the geometric offset for detector offset correction based on the difference between the measured value and the estimated value of the projection coordinates of the target phantom, without the aid of high-precision optical equipment, thereby reducing the application cost of geometric correction; in addition, it can also realize periodic detection of geometric offset during the use of the medical imaging system, and then complete periodic correction, thereby reducing mechanical costs, and further reducing the hardware cost of the medical imaging system.

[0034] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

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

[0037] Figure 2 is a flow chart of the detector offset detection method of this embodiment;

[0038] Figure 3 is a schematic diagram of detector offset variables for a tomographic imaging system;

[0039] Figure 4 is a structural schematic diagram of a three-dimensional array model of this embodiment;

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

[0041] Figure 6 is a flow chart of a method for detecting an offset of a detector applied to a SPECT system in some embodiments;

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

[0043] Figure 8 Schematic diagram of the structure of the medical imaging system of this embodiment. DETAILED DESCRIPTION

[0044] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0045] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the", "these" and the like in this application do not represent quantitative restrictions, and they can be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether directly or indirectly. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. Usually, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0046] The method embodiment provided in this embodiment can be executed in a terminal, a computer or a similar computing device. For example, running on a terminal, Figure 1 FIG. 1 is a hardware structure diagram of a terminal of the detector offset detection method of this embodiment. Figure 1 As shown, the terminal may include one or more ( Figure 1 Only one is shown in the figure) processor 102 and memory 104 for storing data, wherein processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA. The above terminal may also include a transmission device 106 and an input and output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is only for illustration and does not limit the structure of the above terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations shown.

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

[0048] The transmission device 106 is used to receive or send data via a network. The above network includes a wireless network provided by the communication provider of the terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 can be a radio frequency (Radio Frequency, referred to as RF) module, which is used to communicate with the Internet wirelessly.

[0049] In this embodiment, a detector offset detection method is provided for a medical imaging system. Figure 2 is a flow chart of the detector offset detection method of this embodiment, such as Figure 2 As shown, the process includes the following steps:

[0050] Step S210, obtaining the measured coordinates of the target phantom projected on the detector of the medical imaging system.

[0051] The target phantom may specifically be a geometric phantom for geometric correction of the detector, for example, a spherical phantom. The size, shape and material of the target phantom may be predetermined according to the requirements of the actual application scenario. The above-mentioned medical imaging system may specifically be a tomography imaging system. For example, a Digital subtraction angiography (DSA) system, a Computed Tomography (CT) system or a SPECT system. Wherein, when the application scenario is a DSA system or a CT system, the above-mentioned target phantom may be a steel ball, and when the application scenario is a SPECT system, the above-mentioned target phantom may be a radioactive source ball, and specifically, the radioactive nuclide Tc-99m may be used as a radiation source. In the offset correction scenario, on the one hand, the radioactive source ball can simulate the distribution of radioactivity in the body and more realistically reflect the imaging conditions of the SPECT system in actual application; on the other hand, the correction accuracy can be improved based on the clear imaging target provided by the radioactive source ball.

[0052] The target phantom can be fixed between the detector and the scanning bed of the medical imaging system, and the target phantom can be rotationally scanned based on a pre-set scanning protocol to obtain specific coordinates of the target phantom on the detector at different projection angles. The above scanning protocol can be any protocol that can realize multi-angle rotation scanning, and this embodiment does not specifically limit this. The above target phantom can be one or more. After the target phantom is fixed, based on the scanning of the target phantom, the measured coordinates of the target phantom projected on the detector are obtained.

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

[0054] Based on the structure of the medical imaging system, physical modeling can be used to map the three-dimensional spatial coordinates of the target model to the projection coordinates on the detector to obtain a spatial position model. The spatial position model contains the correspondence between the estimated coordinates and the geometric offset of the detector. Based on the spatial position model, the projection coordinates of the target model on the detector are estimated to obtain the estimated coordinates of the target model projected on the detector. The estimated coordinates can be regarded as the theoretical coordinates of the target model projected on the detector. It can be understood that the above-mentioned estimated coordinates obtained by the spatial position model can be in the form of 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 model.

[0055] Step S230, determining the geometric offset of the detector according to the difference between the measured coordinates and the estimated coordinates.

[0056] The above-mentioned geometric offset is the offset of the detector during the process of collecting projection data, which can be described by six variables. Figure 3 Schematic diagram of detector offset variables for a tomography imaging system. Figure 3 As shown, the tomography imaging system includes a detector and a frame, and the detector is fixed on the frame. The above six variables used to describe the geometric offset are: the rotation of the detector along its own X-axis, which can be described as pitch; the displacement of the detector along its own X-axis, which can be described as transX; the rotation of the detector along its own Y-axis, which can be described as roll; the displacement of the detector along its own Y-axis, which can be described as transY; the rotation of the detector along its own Z-axis, which can be described as yaw; the displacement of the detector along its own Z-axis, which can be described as transZ. The above spatial position model can specifically include a mapping relationship between the estimated coordinates and the geometric offset. The spatial position model between the above estimated coordinates and the geometric offset can be obtained by combining the projection intrinsic matrix and the three-dimensional spatial coordinates of the target model.

[0057] Among them, according to the above-mentioned spatial position model, a preset minimum solution algorithm can be used to construct an objective function for solving the geometric offset, and the objective function can include the difference expression between the estimated coordinates and the measured coordinates, as well as the prior knowledge about the various parameters to be solved. In the above-mentioned difference expression, the estimated coordinates can be represented by the geometric offset and the projection intrinsic matrix through the above-mentioned spatial position model. By solving the objective function, the geometric offset of the detector can be determined. Specifically, the geometric offset can be solved based on a minimum solution algorithm such as the least squares method, the Newton method or the gradient descent method. In addition, a three-dimensional reconstruction algorithm can be used in the process of geometric offset, such as a two-dimensional to three-dimensional restoration algorithm based on the field of computer vision. Specifically, it can be a motion recovery structure (Structure from Motion, referred to as SFM) algorithm, a multi-view stereo vision (Multi-View Stereo, referred to as MVS) algorithm, etc. After constructing the above-mentioned objective function, the preset three-dimensional reconstruction algorithm can be used to realize the solution of the geometric offset of the target phantom and the specific three-dimensional coordinates of the target phantom.

[0058] For medical imaging systems, when the detector rotates to collect projection data of the scanned sample, it will be affected by its own gravity and will have angular offset and spatial displacement. Take the dual-probe SPECT system as an example. The detector and collimator used by the dual-probe SPECT system to collect gamma rays emitted by the scanned sample are of large mass. It is difficult to design a mechanical structure that can ensure that the gamma-ray detector is always in the expected position and the manufacturing cost is high. In addition, in practical applications, the scanning protocol of the dual-probe SPECT system usually requires each probe to rotate at least 180 degrees around the scanned sample. Based on this, the detector is affected by gravity, and the offset at different projection angles is also different. If the offset of the detector is ignored during the image reconstruction process, the reconstruction accuracy and quantitative accuracy of the SPECT reconstructed image will be reduced. In particular, if the offset of the detector at different angles is large, it will also cause artifacts in the reconstructed SPECT image, thereby affecting the interpretation of the SPECT image.

[0059] At present, some SPECT system manufacturers will use high-precision optical systems to calculate the three-dimensional rotational deformation parameter matrix (that is, the geometric offset mentioned above) for each imaging system before it leaves the factory, and consider the impact of these parameters on the reconstruction in quantitative reconstruction. Therefore, the hardware cost of calibrating the geometric parameters of the SPECT system is currently high, and the calibration can only be achieved before leaving the factory, and it is impossible to perform periodic calibration for the offset generated by the detector during actual use.

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

[0061] Different from this, the above steps S210 to S230, based on the difference between the measured coordinates and the estimated coordinates, combined with the spatial position model between the estimated coordinates and the geometric offset, can correct the geometric offset of the detector caused by gravity and tooling errors in the tomographic imaging system. On the one hand, there is no need to use a high-precision optical system, thereby reducing hardware costs. On the other hand, the present embodiment is not limited to geometric correction before shipment, but can also repeatedly implement periodic correction of the detector offset in the actual use of the medical imaging system. In addition, since the present embodiment can implement geometric correction of the detector, the mechanical cost of the tomographic imaging system is reduced. In addition, the workflow of the entire geometric offset solution process is relatively simple, and there is no registration and conversion between multiple coordinate systems, which facilitates the maintenance and learning of the workflow.

[0062] In the above steps S210 to S230, the measured coordinates of the target phantom projected on the detector of the medical imaging system are obtained, and the estimated coordinates of the target phantom projected on the detector are determined based on the spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; and the geometric offset of the detector is determined according to the difference between the measured coordinates and the estimated coordinates. It realizes accurate solution of the geometric offset for detector offset correction based on the difference between the measured value and the estimated value of the projection coordinates of the target phantom, without the aid of high-precision optical equipment, thereby reducing the application cost of geometric correction; in addition, it can also realize periodic detection of geometric offset during the use of the medical imaging system, and then complete periodic correction, thereby reducing the mechanical cost of the detector, and further, it can reduce the hardware cost of geometric correction of the medical imaging system.

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

[0064] A 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; different target phantoms are located in different spatial positions; the projection data are fitted to obtain the measured coordinates of the target phantom projected on the detector.

[0065] The three-dimensional array model can be provided with multiple layers of plug boards, and multiple sockets can be provided on each layer of plug boards. The spacing between each socket can be set according to the requirements of the actual application scenario. Multiple target phantoms can be staggered and placed in sockets at different positions of different layers of plug boards of the three-dimensional array model. Figure 4 FIG. 1 is a schematic diagram of the structure of a three-dimensional array model of this embodiment. Figure 4As shown, the three-dimensional array model can be a cube, including a base and a multi-layer plug-in board. A plurality of sockets are arranged at intervals on each layer of the plug-in board. When applied to the SPECT system, the target phantom can be a radioactive source ball. The size of the radioactive source ball matches the socket. When different radioactive source balls are placed in the sockets of different layers, the different radioactive source balls can be kept at a certain spatial distance as much as possible, and there is no need to insert the radioactive source ball into each socket. Which sockets are specifically needed to place the radioactive source balls can be determined according to the needs of the actual application scenario.

[0066] Figure 5 FIG. 1 is a schematic diagram of the placement of a three-dimensional array model of this embodiment. Figure 5 As shown in FIG. 1 , the SPECT system includes a SPECT system detector, a SPECT system scanning bed, and a SPECT system rack. During the scanning process, the stereo array phantom can be placed on the SPECT system scanning bed. Figure 5 The left and right sides of the stereo array model are parallel to the moving direction of the scanning bed (such as Figure 5 The SPECT system collects projection data of different angles from the three-dimensional array phantom within a preset angle range according to a preset SPECT scanning protocol. The above-mentioned SPECT scanning protocol is a scanning protocol that enables the detector to collect projection data from different projection angles.

[0067] By setting up a three-dimensional array model to place each target model, the target model can be fixed during the calibration process, thereby facilitating the calibration of the geometric offset. In addition, this embodiment only introduces a three-dimensional array model with a simple structure to achieve the geometric calibration of the detector. Compared with other geometric calibration solutions in the related art, the test cost of this embodiment is also lower.

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

[0069] In this embodiment, first, according to a preset scanning protocol, within a preset angle range, such as a 360-degree angle range, projection data of the target phantom at different projection angles are collected. Then, the collected projection data are fitted using a Gaussian function, and the measured coordinates of the target phantom on the detector at different projection angles can be obtained. By introducing the Gaussian function, accurate fitting of the projection data can be achieved, and then the accurate measured coordinates of the target phantom on the detector can be calculated, thereby improving the calculation accuracy of the measured coordinates.

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

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

[0072] Specifically, according to the structure and imaging mechanism of the medical imaging system, the mapping relationship between the three-dimensional spatial coordinates of the position of the target phantom in the three-dimensional space and the two-dimensional projection coordinates of the target phantom projected on the detector is physically modeled, so that the estimated coordinates of the detector at different projection angles can be obtained. The estimated coordinates are represented by the geometric offset, 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 shown 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] Among them, π m (p i ) represents the target motif p i The estimated coordinates on the detector at the mth projection angle, i.e., the theoretical coordinate values; pi in the formula represents the three-dimensional spatial coordinates of the target model; K represents the projection intrinsic matrix of the current imaging system, and all values ​​in the matrix are known quantities; R(α m ,β m ,γ m ) (abbreviated as Rm) is the rotation matrix caused by the deflection of the detector along each axis at the mth projection angle. The size of the rotation matrix is ​​3x3, where α m Corresponding to the rotation of the detector along its own Y axis, β m Corresponding to the rotation of the detector along its own X-axis, γ m corresponds to the rotation of the detector along its own Z axis; finally, T m Represents the displacement vector of the detector along each axis at the mth rotation angle, and the size of the displacement vector is 3x1.

[0075] In this embodiment, by physically modeling the medical imaging system, the estimated coordinates of the detector at different projection angles can be determined, and the geometric offset of the detector is taken into account in the physical model. Therefore, it can provide an accurate theoretical basis for the subsequent solution of the geometric offset, thereby improving the accuracy of the subsequent solution of the geometric offset.

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

[0077] Based on the preset 3D reconstruction algorithm, the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates is solved.

[0078] Among them, the objective function can be constructed according to the spatial position model between the estimated coordinates and the geometric offset according to the preset minimum value solving algorithm to solve the geometric offset that makes the measured coordinates closest to the estimated coordinates. Exemplarily, the following objective function can be constructed based on the least squares method:

[0079]

[0080] in, Represents the rotation matrix at each projection angle; is the displacement vector; is the ideal value of the three-dimensional coordinate of the target phantom; M is the number of projection angles, and N is the number of target phantoms; By solving the objective function on the right side of the formula, we can get R m is the rotation matrix caused by the deflection of the detector along each axis at the mth projection angle; T m is the displacement vector of the detector along each axis at the mth rotation angle; q im represents the measured coordinates of the i-th target model on the detector at the m-th projection angle. P(R,T,p) represents the prior knowledge about the various geometric parameters required, and β is the weight value preset for the prior knowledge. The value can be an empirical value in the actual application scenario, and the value range is set according to P(R,T,p) and the coordinates of the acquisition point source. K is the projection intrinsic matrix of the medical imaging system.

[0081] It is understandable that the above objective function can also be in other forms, which are not specifically limited in this embodiment. In particular, the minimum value solving algorithm can use the least square method and combine it with the SFM algorithm to solve the geometric offset. In addition, other algorithms and three-dimensional reconstruction algorithms can also be selected according to the needs of actual application scenarios.

[0082] This embodiment uses a preset minimum solution algorithm to solve the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates, and specifically uses a three-dimensional reconstruction algorithm in the field of computer vision to achieve the solution of the geometric offset and the specific coordinates of the target model in the three-dimensional space. Based on this process, it is ultimately possible to achieve geometric correction of the detector of the medical imaging system and reduce errors caused by the gravity and tooling of the detector.

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

[0084] In particular, in one embodiment, the 3D reconstruction algorithm is a structure from motion algorithm. The SFM algorithm is an image-based 3D reconstruction technology for scenes that can recover the 3D structure of a scene from image data or other sensor data. When actually solving the geometric offset, the SFM algorithm is used for calculation, thereby further improving the accuracy of the calculation result by utilizing the high precision and robustness of the SFM algorithm in 3D structure recovery, achieving accurate calibration of the detector geometric offset, and thereby improving the quality and accuracy of subsequent image reconstruction.

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

[0086] According to the detected geometric offset of the detector, the detector is offset corrected. Specifically, the relevant parameters of the tomography imaging device, such as the position and angle of the detector, can be adjusted according to the detected geometric offset of the detector to achieve the offset correction of the detector. In this embodiment, the detector is offset corrected based on the accurate geometric offset of the detector, so as to improve the accuracy of the medical image.

[0087] In addition, in one embodiment, the above detector offset detection method may further include:

[0088] The geometric offset of the detector is input into a preset medical imaging reconstruction algorithm to obtain a target reconstructed image. After the geometric offset of the detector is calculated, the obtained geometric offset can be input into a subsequent medical imaging reconstruction algorithm to achieve reconstruction of the medical image. The above-mentioned medical imaging reconstruction algorithm varies with different medical imaging systems, and can specifically be a SPECT reconstruction algorithm, a CT reconstruction algorithm, or a DSA reconstruction algorithm.

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

[0090] Figure 6 FIG. 1 is a flow chart of a method for detecting the offset of a detector in a SPECT system in some embodiments. Figure 6 As shown, the detector offset detection method includes the following steps:

[0091] Step S601, insert the radiation source ball into the socket of the three-dimensional array model; wherein, when the detector of the SPECT system is geometrically corrected, the radiation source ball is selected as the target model. Before placing the radiation source ball in the socket of the three-dimensional array model, a theoretical analysis can be performed according to the needs of the actual application scenario, and the socket where the radiation source ball needs to be placed can be pre-selected, and different radiation source balls can be placed in different sockets of different layers of the three-dimensional array model.

[0092] Step S602, placing the three-dimensional array model with the radiation source placed on the scanning bed of the SPECT system; during the placement, the left and right sides of the three-dimensional array model can be made parallel to the moving direction of the scanning bed as much as possible (no accuracy requirement).

[0093] Step S603, according to a preset SPECT scanning protocol, collecting projection data at different angles for the stereo array model within a 360-degree range; wherein the SPECT scanning protocol can be any scanning protocol that enables the detector to collect projection data within a 360-degree range.

[0094] Step S604, fitting the collected projection data using a Gaussian function to calculate the measured coordinates of the radiation source ball on the detector at different projection angles;

[0095] Step S605, based on the spatial position model obtained by physical modeling of the SPECT system, the estimated coordinates of the radiation source ball on the detector are obtained.

[0096] Step S606, using the least squares method combined with the SFM algorithm, solves the geometric offset that minimizes the difference between the measured coordinates and the estimated coordinates; wherein, the spatial position model also includes the projection intrinsic matrix of the SPECT system, and the specific form can refer to the formula of the above embodiment, which will not be repeated here. Ideally, the estimated coordinates in step S605 are consistent with the measured coordinates in step S604, but due to the offset of the detector and the unknown specific value of the radiation source ball in the three-dimensional space, the measured coordinates of the radiation source ball on the detector will deviate from the estimated coordinates. Based on this, by minimizing the difference between the measured coordinates and the estimated coordinates, with the help of the SFM algorithm, the actual geometric offset of the detector and the specific coordinates of the radiation source ball in the three-dimensional space are determined.

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

[0098] In the above steps S601 to S607, with the help of an optimization algorithm combined with a three-dimensional reconstruction algorithm, the geometric offset is accurately solved according to the difference between the measured value and the estimated value of the projection coordinates of the target model, without the need for high-precision optical equipment, thereby reducing the hardware cost of geometric correction; in addition, periodic correction can be achieved during the use of the medical imaging system.

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

[0100] In this embodiment, a detector offset detection device is also provided, which is used to implement the above embodiments and preferred implementations, and will not be repeated hereafter. The terms "module", "unit", "subunit", etc. used below may be a combination of software and / or hardware that implements a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware, is also possible and conceivable.

[0101] Figure 7 FIG. 7 is a block diagram of a detector offset detection device 70 of this embodiment, and the detector offset detection device 70 is used in a medical imaging system. Figure 7As shown, the detector offset detection device 70 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 obtain the measured coordinates of the target model projected on the detector of the medical imaging system; the second acquisition module 74 is used to determine the estimated coordinates of the target model projected on the detector based on the spatial position model; the spatial position model is obtained by physical modeling of 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 by software or hardware. For modules implemented by hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0104] In this embodiment, a medical imaging system is also provided. Figure 8 is a schematic diagram of the structure of the medical imaging system 80 of this embodiment. Figure 8 As shown, the medical imaging system 80 at least includes: a detector 82 and a processor 84; the detector 82 is used to collect 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 parts shown, the medical imaging system 80 may also include more structures, such as a scanning bed, a gantry, a collimator and a 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 implementation modes, and will not be repeated in this embodiment.

[0106] In addition, in combination with the detector offset detection method provided in the above embodiments, a storage medium can also be provided in this embodiment to implement the method. The storage medium stores a computer program; when the computer program is executed by a processor, any detector offset detection method in the above embodiments is implemented.

[0107] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope 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, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0109] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

[0110] The term "embodiment" in this application refers to a specific feature, structure or characteristic described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various locations in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. It is clearly or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.

[0111] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for detecting the offset of a detector, characterized in that: For use in a medical imaging system, the method comprises: Acquiring measured coordinates of the target phantom projected on the detector of the medical imaging system; Determining estimated coordinates of the projection of the target phantom on the detector based on a spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; The geometric offset of the detector is determined according to the difference between the measured coordinates and the estimated coordinates.

2. The detector offset detection method according to claim 1, characterized in that: The step of obtaining the measured coordinates of the target phantom projected on the detector of the medical imaging system includes: Using the medical imaging system to scan each target phantom placed in a preset three-dimensional array model to obtain projection data of each target phantom; wherein different target phantoms are located at different spatial positions; The projection data are fitted to obtain the measured coordinates of the target phantom projected on the detector.

3. The detector offset detection method according to claim 1, characterized in that: The step of determining the estimated coordinates of the projection of the target phantom on the detector based on the spatial position model includes: Performing physical modeling according to the structure of the medical imaging system, determining a mapping relationship between the three-dimensional spatial coordinates of the target phantom and the projection coordinates of the target phantom on the detector, and constructing the spatial position model; The estimated coordinates of the detector at different projection angles are obtained according to the spatial position model.

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

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

6. The detector offset detection method according to any one of claims 1 to 5, characterized in that: The method further comprises: The detector is subjected to offset correction according to the detected geometric offset of the detector.

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

8. A detector offset detection device, characterized in that: For use in a medical imaging system, the device comprises: a first acquisition module, a second acquisition module and a solution module; wherein: The first acquisition module is used to acquire the measured coordinates of the target phantom projected on the detector of the medical imaging system; The second acquisition module is used to determine the estimated coordinates of the projection of the target phantom on the detector based on the spatial position model; the spatial position model is obtained by physically modeling the medical imaging system; The offset determination module is used to determine the geometric offset of the detector according to the difference between the measured coordinates and the estimated coordinates.

9. A medical imaging system, characterized in that: The system at least includes: 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 a processor, the steps of the detector offset detection method according to any one of claims 1 to 7 are implemented.

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