Crystal spatial position determination method, PET image reconstruction method and related device

Abstract

The embodiment of the invention discloses a crystal spatial position determination method, a PET image reconstruction method and a related device, which are applied to positron emission tomography equipment comprising an annular detector, and the annular detector is composed of a plurality of detection modules which are annularly arranged in the radial direction and axially arranged at intervals. Each detection module comprises an array composed of a plurality of actual crystals, and the method comprises the steps: introducing virtual crystals between the detection modules which are axially arranged at intervals, so as to calculate the length of each crystal according to the depth of the annular detector, the detection modules which are annularly arranged in the radial direction are regarded as arcs attached to the inner wall of the annular detector, so that the width of each crystal is calculated according to the perimeter of the annular detector; determining the size of the crystal according to the length and width of the crystal; and determining the spatial position of each crystal according to the size of the crystal. By adopting the embodiment of the invention, the line artifact caused by the PET equipment hardware problem can be removed by re-determining the spatial position of the crystal.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical equipment, and in particular to a method for determining the spatial position of a crystal, a PET image reconstruction method and related devices. Background Art

[0002] Positron Emission Tomography (PET) is an advanced technology developed in the field of biomedical engineering after Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). It can perform functional imaging of human or animal metabolism at the molecular level. PET is non-invasive and can achieve comprehensive imaging of function, metabolism and physiology. It is known as the top technology in medical equipment in the 21st century. Although PET is of great significance in medical applications such as oncology, neuroscience, cardiovascular research, genetic engineering and drug development, its imaging spatial resolution is still lower than that of CT and MRI. Although the iterative reconstruction technology currently widely used can improve image quality, the noise may also gradually increase during the iteration process, eventually leading to obvious artifact problems in the image.

[0003] There are three main methods for removing artifacts: filtering, regularization, and deep learning. Although these methods can effectively remove most noise artifacts in PET systems, it is still difficult to completely remove line artifacts caused by hardware problems in PET equipment. This is because these artifacts mainly affect the data domain, while traditional artifact removal methods mostly eliminate artifacts in the image domain. Summary of the invention

[0004] The embodiments of the present application provide a method for determining the spatial position of a crystal, a PET image reconstruction method, and related devices, which are beneficial for removing line artifacts caused by hardware problems of the PET device by re-determining the spatial position of the crystal.

[0005] In a first aspect, an embodiment of the present application provides a method for determining the spatial position of a crystal, which is applied to a positron emission tomography device including an annular detector, wherein the annular detector is composed of a plurality of detection modules arranged in an annular manner in a radial direction and arranged at intervals in an axial direction, and each of the detection modules includes an array composed of a plurality of actual crystals, and the method includes: Introducing virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and regarding the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals; Determining the size of the crystal according to the length of the crystal and the width of the crystal; The spatial position of each of the crystals is determined according to the size of the crystal.

[0006] Optionally, the step of introducing virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector comprises: Determining the spacing distance between the axially spaced detection modules; Taking the integer of the quotient of the spacing distance and the length of a single actual crystal to obtain the target number; Introducing the target number of virtual crystals between the axially spaced detection modules; The quotient of the depth of the annular detector and the number of the virtual crystals and the actual crystals in the axial direction is determined as the length of each crystal.

[0007] Optionally, the step of considering the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector includes: The radially annularly arranged detection modules are regarded as arcs that fit the inner wall of the annular detector; The quotient of the circumference of the annular detector and the number of the actual crystals in the radial direction is determined as the width of each crystal.

[0008] Optionally, determining the spatial position of each of the crystals according to the size of the crystals includes: Establishing a rectangular coordinate system and numbering each of the crystals, wherein the direction of the y-axis of the rectangular coordinate system is the axial direction of the annular detector, and the plane formed by the x-axis and the z-axis of the rectangular coordinate system is the radial plane of the annular detector; Determine the polar angle according to the number of each crystal and the unit center angle, wherein the unit center angle is equal to the quotient of 2π and the number of the actual crystals in the radial direction; Determine the x-coordinate and z-coordinate of each of the crystals according to the polar angle and the radius of the annular detector, and determine the y-coordinate of each of the crystals according to the number of each of the crystals and the length of each of the crystals; The spatial position of each of the crystals is determined according to the x-coordinate, y-coordinate and z-coordinate of each of the crystals.

[0009] Optionally, the serial numbers of the crystals increase axially from one side of the annular detector to the other side, the axial number of the first circle of crystals on one side of the annular detector is 0, and the determining the y coordinate of each crystal according to the number of each crystal and the length of each crystal includes: The product of the axial number of each crystal and the length of each crystal plus half the length of the crystal is taken as the y coordinate of each crystal.

[0010] A second aspect of an embodiment of the present application provides a positron emission tomography image reconstruction method, the method comprising: Determine the spatial position of each of the crystals in the annular detector according to the method described in any one of the first aspects; Determine a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used to describe the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; The positron emission tomography image is reconstructed according to the system matrix.

[0011] A third aspect of the embodiments of the present application provides a device for determining the spatial position of a crystal, which is applied to a positron emission tomography device including an annular detector, wherein the annular detector is composed of a plurality of detection modules arranged in a radial annular manner and arranged at intervals in an axial direction, each of the detection modules comprising an array composed of a plurality of actual crystals, and the device comprises: a crystal size calculation unit, configured to introduce virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and to regard the radially annularly arranged detection modules as arcs fitted to the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals; a crystal size determination unit, used to determine the size of the crystal according to the length of the crystal and the width of the crystal; The crystal spatial position determining unit is used to determine the spatial position of each of the crystals according to the size of the crystal.

[0012] A fourth aspect of the embodiments of the present application provides a positron emission tomography image reconstruction device, characterized in that the device comprises: A crystal spatial position determination unit, used to determine the spatial position of each of the crystals in the annular detector according to the method described in any one of the first aspects; A system matrix determination unit, used for determining a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used for describing the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; An image reconstruction unit is used to reconstruct the positron emission tomography image according to the system matrix.

[0013] A fifth aspect of the embodiments of the present application provides an electronic device, including: a processor and a memory; The processor is connected to the memory, wherein the memory is used to store a computer program, and the processor is used to call the computer program to execute the method in the first aspect or the second aspect of the embodiment of the present application.

[0014] A fourth aspect of an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. The computer program includes program instructions. When the program instructions are executed by a processor, the method in the first aspect or the second aspect of the embodiment of the present application is executed.

[0015] The present application is applied to a positron emission tomography device including an annular detector, wherein the annular detector is composed of a plurality of detection modules arranged in a radial annular manner and arranged at intervals in the axial direction, each detection module includes an array composed of a plurality of actual crystals, and by introducing a virtual crystal between the detection modules arranged at intervals in the axial direction, when calculating the length of each crystal according to the depth of the annular detector, the crystal includes the virtual crystal and the actual crystal, so that the response line of the virtual crystal is regarded as a real response line, thereby filling the data missing in the system matrix, improving the edge clarity and structural integrity of the image, and making the final generated PET image clearer; at the same time, the detection modules arranged in a radial annular manner are regarded as arcs that fit the inner wall of the annular detector, so that the detection module can be eliminated. Due to the existence of gaps in the radial direction of the module, photons in some areas cannot be detected, resulting in line artifacts caused by missing information when calculating the system matrix. In addition, calculating the width of each crystal based on the circumference of the annular detector is equivalent to reconstructing the original crystal width, which is beneficial to eliminating line artifacts caused by differences in the distances between the endpoints of adjacent response lines due to different intervals between crystals. It can be seen that after the above processing, the size of the crystal is determined based on the length and width of the crystal, and the spatial position of each crystal is determined based on the size of the crystal. The recalculated crystal spatial position can be used to calculate the system matrix and reconstruct PET images through the system matrix, which can effectively remove line artifacts caused by hardware problems of the PET device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the structure of a PET imaging system provided by an embodiment of the present application is shown; Figure 2 A schematic diagram showing exemplary hardware and software components of a computing device on which a data processing system can be implemented according to one embodiment of the present application; Figure 3 An exemplary structural diagram of a ring-shaped detector on which a detector can be implemented according to an embodiment of the present application is shown; Figure 4 A schematic diagram of a processing process of axially spaced detection modules provided by an embodiment of the present application is shown; Figure 5 A schematic diagram of a crystal spacing process provided by an embodiment of the present application is shown; Figure 6 A schematic diagram of a processing process of a radially annularly arranged detection module provided by an embodiment of the present application is shown; Figure 7 A schematic diagram showing a flow chart of a method for determining the spatial position of a crystal provided by an embodiment of the present application; Figure 8 A schematic diagram of a rectangular coordinate system provided by an embodiment of the present application is shown; Fig. 9 A schematic diagram of a process of a positron emission tomography image reconstruction method provided by an embodiment of the present application is shown; Fig.10 A three-dimensional slice diagram of the sensitivity factor before removing the interval provided by one embodiment of the present application is shown; Fig.11 A three-dimensional slice diagram of the sensitivity factor after removing the interval provided by an embodiment of the present application is shown; Fig.12 A schematic diagram showing the structure of a device for determining the spatial position of a crystal provided by an embodiment of the present application is shown; Fig.13 A schematic structural diagram of a positron emission tomography image reconstruction device provided by an embodiment of the present application is shown; Fig.14 A schematic diagram of the structure of a computer device provided in one embodiment of the present application is shown. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0019] Please refer to Figure 1 , which shows a schematic diagram of the structure of a PET imaging system provided by an embodiment of the present application. The PET imaging system can generate a PET image of a scanned object. As shown in the figure, the PET imaging system may include an imaging device 110, a controller 120, a data processing system 130, an input / output device 140, a network 160 and (all) terminals 170.

[0020] In some embodiments, the imaging device 110 may be a PET imaging device including a frame 111, a detector 112, a detection region 113, a platform 114, and a radioactive scanning source 115. The frame 111 may support the detector 112 and the radioactive scanning source 115. An object may be placed on the platform 114 for scanning. The radioactive scanning source 115 may emit radioactive rays to the object. The detector 112 may detect radiation events (e.g., gamma photons) emitted from the detection region 113.

[0021] The controller 120 may control the imaging device 110, the input / output device 140, and / or the data processing system 130. In some embodiments, the controller 120 may receive information from or send information to the imaging device 110, the input / output device 140, and / or the data processing system 130. For example, the controller 120 may receive a command provided by a user from the input / output device 140. As another example, the controller 130 may process data input by a user via the input / output unit 140 and transform the data into one or more commands. As another example, the controller 120 may control the imaging device 110, the input / output device 140, and / or the data processing system 130 according to the received command or the transformed command. As yet another example, the controller 120 may receive an image signal or data related to an object from the imaging device 110. As yet another example, the controller 120 may send an image signal or data to the data processing system 130. As yet another example, the controller 120 may receive processed data or a constructed image from the data processing system 130. As yet another example, the controller 120 may send the processed data or constructed image to the input / output device 140 for display. In some embodiments, the controller 120 may include a computer, a program, an algorithm, software, a storage device, one or more interfaces, etc. Exemplary interfaces may include interfaces with the imaging device 110, the input / output device 140, the data processing system 130, and / or other modules or units in the imaging system.

[0022] In some embodiments, the controller 120 may receive commands provided by a user including, for example, an imaging technician, a doctor, etc. Exemplary commands may be about scanning time, object position, position of the object lying on the bed, controlled or rotational speed of the gantry, specific parameters related to thresholds that may be used in the image reconstruction process, or the like, or any combination thereof. In some embodiments, the controller 120 may control the data processing system 130 to select different algorithms to process the raw data of the image.

[0023] The data processing system 130 can process information received from the imaging device 110, the controller 120, the input / output device 140 and / or the terminal 170. In some embodiments, the data processing system 130 can generate one or more PET images based on the information. The data processing system 130 can deliver the image to the input / output device 140 for display. In some embodiments, the data processing system 130 can perform operations including, for example, data preprocessing, image reconstruction, image correction, image synthesis, lookup table creation, etc., or any combination thereof. In some embodiments, the data processing system 130 can process data based on algorithms including, for example, Fourier slice theorem, filtered back projection algorithm, fan beam reconstruction, iterative reconstruction, etc., or any combination thereof. Just as an example, image data about the lungs can be processed in the data processing system 130. In some embodiments, the data processing system 130 can reconstruct PET images. In some embodiments, artifacts may appear in PET images due to PET device hardware problems. The data processing system 130 can apply various algorithms or techniques to reduce artifacts. For example, the spatial position determination method of the crystal and the PET image reconstruction method in the present application are applied to reduce artifacts.

[0024] In some embodiments, the data processing system 130 may generate control signals regarding the configuration of the imaging device 110. In some embodiments, the results generated by the data processing system 130 may be provided to other modules or units in the system, including, for example, a database (not shown), a terminal (not shown), via the network 160. In some embodiments, data from the data processing system 130 may be transmitted to a storage (not shown) for storage.

[0025] Input / output device 140 can receive or output information. In some embodiments, input / output device 140 can include keyboard, touch screen, mouse, remote controller, etc., or any combination thereof. Input and / or output information can include program, software, algorithm, data, text, number, image, sound, or the like, etc., or any combination thereof. For example, a user can input some initial parameters or conditions to initiate an imaging process. As another example, some information can be imported from an external resource (including, for example, a floppy disk, a hard disk, a wired terminal, a wireless terminal, etc., or any combination thereof). Output information can be transmitted to a display, a printer, a storage device, a computing device, etc., or a combination thereof. In some embodiments, input / output device 140 can include a graphical user interface. This graphical user interface can facilitate user input parameters and intervene in data processing procedures.

[0026] The network 160 may include any suitable network that can facilitate the exchange of information and / or data for the imaging system 100. In some embodiments, one or more components of the imaging system 100 (e.g., the imaging device 110, the controller 120, the data processing system 130, the input / output device 140, and / or the terminal 170, etc.) may communicate information and / or data with one or more other components of the imaging system 100 via the network 160. For example, the data processing system 130 may obtain image data from the imaging device 110 via the network 160. As another example, the data processing system 130 may obtain user instructions from the terminal 170 via the network 160.

[0027] The network 160 may be and / or include a public network (e.g., the Internet), a private network (e.g., a local area network (LAN), a wide area network (WAN), etc.), a wired network (e.g., Ethernet), a wireless network (e.g., an 802.11 network, a Wi-Fi network, etc.), a cellular network (e.g., a long term evolution (LTE) network), a frame relay network, a virtual private network (“VPN”), a satellite network, a telephone network, a router, a hub, a switch, a server computer, and / or any combination thereof. By way of example only, the network 160 may include a cable network, a wired network, a fiber optic network, a telecommunications network, an intranet, a wireless local area network (WLAN), a metropolitan area network (MAN), a public switched telephone network (PSTN), a Bluetooth™ network, a ZigBee™ network, a near field communication (NFC) network, etc., or any combination thereof. In some embodiments, the network 160 may include one or more network access points. For example, network 160 may include wired and / or wireless network access points (such as base stations and / or Internet exchange points) through which one or more components of imaging system 100 may be connected to network 160 to exchange data and / or information.

[0028] The terminal(s) 170 may include a mobile device 171, a tablet computer 172, a laptop computer 173, etc., or any combination thereof. In some embodiments, the mobile device 171 may include a smart home device, a wearable device, a mobile device, a virtual reality device, an augmented reality device, etc., or any combination thereof. In some embodiments, the smart home device may include a smart lighting device, a control device for a smart electrical device, a smart monitoring device, a smart TV, a smart camera, an interconnected phone, etc., or any combination thereof. In some embodiments, the wearable device may include a bracelet, footwear, glasses, a helmet, a watch, clothing, a backpack, a smart accessory, etc., or any combination thereof. In some embodiments, the mobile device may include a mobile phone, a personal digital assistant (PDA), a gaming device, a navigation device, a point of sale (POS) device, a laptop device, a tablet computer, a desktop, etc., or any combination thereof. In some embodiments, the virtual reality device and / or the augmented reality device may include a virtual reality helmet, virtual reality glasses, virtual reality goggles, augmented reality helmets, augmented reality glasses, augmented reality goggles, etc., or any combination thereof. In some embodiments, the terminal(s) 170 may be part of the data processing system 130.

[0029] The gating system 180 may collect information related to, for example, respiration, heartbeat, etc. The gating system 180 may analyze the information to obtain motion signals, including, for example, respiration signals, cardiac motion signals, etc. The gating system may include a gating camera for detecting object motion, a control panel, a marker fixed on the surface of the object for indicating object motion, etc., or any combination thereof. In some embodiments, the gating camera may be an infrared camera. For example, when the imaging device 110 is scanning a patient, the gating system may be automatically triggered. The gating system may collect information associated with respiratory motion. The data collected by the gating system may be stored together with the PET data.

[0030] In some embodiments, the imaging device 110, the controller 120, the data processing system 130, the input / output device 140, the terminal 170, and the door control system 180 may be directly connected or communicated with each other. In some embodiments, the imaging device 110, the controller 120, the data processing system 130, the input / output device 140 may be connected or communicated with each other via the network 160. In some embodiments, the imaging device 110, the controller 120, the data processing system 130, the input / output device 140 may be connected or communicated with each other via an intermediary unit (not shown in FIG. 1 ). Figure 1) are connected or communicated with each other. Intermediate units can be visible components or non-visible fields (radio, optical, acoustic, electromagnetic induction, etc.). The connection between different units can be wired or wireless. Wired connections can include the use of metal cables, optical cables, hybrid cables, interfaces, or the like, or any combination thereof. Wireless connections can include the use of local area networks (LANs), wide area networks (WANs), Bluetooth, ZigBee, near field communications (NFC), or the like, or any combination thereof. The network 160 described herein that can be used in conjunction with the present system is not exhaustive and limiting.

[0031] It should be noted that the above description of the imaging system is only an example and should not be understood as the only embodiment. For those skilled in the art, after understanding the basic principles of the connection between different units, these units and the connections between these units can be modified or changed without departing from these principles. Modifications and deformations are still within the scope of the present application described above. In some embodiments, these units are independent, and in some embodiments, parts of these units can be integrated into one unit to work together.

[0032] Please refer to Figure 2 , which shows a schematic diagram of exemplary hardware and software components of a computing device 200 on which a data processing system 130 can be implemented according to an embodiment of the present application. For example, a processing module 440 can be implemented on the computing device 200 and configured to perform the functions of the data processing system 130 described in the present disclosure.

[0033] The computing device 200 may be a general purpose computer or a special purpose computer, both of which may be used to implement the on-demand system of the present disclosure. The computing device 200 may be used to implement any component of the on-demand service as described herein. For example, the data processing system 130 may be implemented on the computing device 200 by its hardware, software program, firmware, or any combination thereof. Although only one such computer is shown for convenience, the computer functions related to the on-demand service as described herein may be implemented in a distributed manner on several similar platforms to distribute the processing load.

[0034] The computing device 200 may include, for example, a communication (COM) port 260 for connecting to and from a network connected thereto to facilitate data communication. The computing device 200 may also include a central processing unit (CPU) 230 in the form of one or more processors for executing program instructions. An exemplary computer platform may include an internal communication bus 220, different forms of program storage and data storage (e.g., disk 210, and read-only memory (ROM) 240, or random access memory (RAM) 250, for various data files to be processed and / or transmitted by the computer. The exemplary computer platform may also include program instructions to be executed by the CPU 230 stored in ROM 240, RAM 250, and / or other types of non-transient storage media. The method and / or process of the present disclosure may be implemented as program instructions. The computing device 200 also includes an I / O component 270, which supports input / output between the computer and other components therein (such as user interface elements 280). The computing device 200 may also receive programming and data via network communications.

[0035] For illustration only, only one CPU and / or processor is described in the computing device 200. However, it should be noted that the computing device 200 in the present disclosure may also include multiple CPUs and / or processors, whereby the operations and / or method steps performed by one CPU and / or processor described in the present disclosure may also be performed jointly or separately by multiple CPUs and / or processors. For example, if the CPU and / or processor of the computing device 200 in the present disclosure performs both operation A and operation B, it should be understood that operation A and operation B may also be performed jointly or separately by two or different CPUs and / or processors in the computing device 200 (e.g., the first processor performs operation A and the second processor performs operation B, or the first and second processors jointly perform operations A and B).

[0036] Please refer to Figure 3 , which shows an exemplary structural diagram of an annular detector 300 on which the detector 112 can be implemented according to an embodiment of the present application. The detector 112 is an annular detector 300, which is composed of a plurality of detection modules 310 arranged in a radial annular manner and arranged at intervals in the axial direction, each detection module 310 includes an array of a plurality of actual crystals 311, and each crystal is a rectangular parallelepiped with a square bottom. The current PET equipment has the following three hardware problems.

[0037] First, due to the need for maintenance and replacement, physical gaps between the axial detection modules of the annular detector are inevitable. These gaps are mainly used to provide support structures for the modules, heat dissipation channels, and reserve space for the wiring and installation of electronic components. The system matrix is ​​used to describe the probability that the connection lines (i.e., the line of response (LOR)) between all crystals in the annular detector pass through each voxel. A voxel refers to a basic pixel unit in a three-dimensional image, similar to the basic unit pixel in a two-dimensional image.

[0038] Whether using the intercept or the cross-sectional area, or the more difficult to calculate irregular vertebral volume, when calculating the system matrix, the sum of the probabilities of LOR passing through all voxels needs to be considered to ensure the local normalization of the system matrix. However, when some LORs are missing due to the gap between the detection modules, the accuracy of the system matrix will be affected, resulting in line artifacts in the final reconstructed image.

[0039] In order to solve this problem, the present application introduces a virtual crystal 312 between the axially spaced detection modules when calculating the spatial position of the crystal. Figure 4 As shown. The size of these virtual crystals is equal to the gap between the detection modules (such gaps can be controlled by hardware design to be consistent with the size of the actual crystal 311), and are regarded as real crystals when calculating the system matrix. The LORs between the virtual crystals and other crystals in the system will be regarded as real response lines, thereby filling the data gaps in the system matrix, improving the edge clarity and structural integrity of the image, making the final PET image clearer, and improving the accuracy and reliability of diagnosis.

[0040] In addition, the introduction of virtual crystals can keep the number of image layers unchanged and avoid image distortion caused by filling the gaps. This method successfully solves the problem of axial linear artifacts by introducing virtual detection points in the reconstruction algorithm without increasing the manufacturing complexity or cost of the equipment. Therefore, this solution can be seamlessly integrated into existing reconstruction algorithms and PET equipment with good compatibility.

[0041] Secondly, in PET equipment, the detection module is covered with crystals of the same size. Most of the crystals are rectangular blocks with a square bottom. Usually, these crystals are arranged in rows and columns with equal intervals on the detection module. However, in a multi-layer crystal detection module, the intervals between each layer of crystals may not be consistent. Although the crystals are arranged more closely, there are still physical intervals between adjacent crystals. These intervals are to deal with multiple practical problems: first, the crystals may be damaged during transportation and installation, and these intervals make the crystals easier to replace; second, the intervals between the crystals help dissipate heat to prevent the crystals from overheating and affecting performance.

[0042] In order to solve this problem, the present application recalculates the width of each crystal and re-determines the center coordinates of each crystal when calculating the spatial position of the crystal, so as to obtain a more accurate system matrix, such as Figure 5 As shown. This solution effectively compensates for the incomplete system matrix problem caused by uneven crystal spacing. By redistributing the crystal size and center position, it can not only improve the accuracy of the system matrix, but also improve the edge clarity of the reconstructed image and reduce artifacts. In addition, this method does not change the structure and complexity of the actual equipment, is easy to apply to existing PET equipment, and has good compatibility and practicality.

[0043] Finally, ideally, the detection modules of the PET device should be closely arranged on the wall of the tube to form a continuous arc structure to achieve seamless capture of photons. However, due to technical limitations of manufacturing and assembly, the design of the detector module cannot be completely bent into an arc. The detection module is usually a flat plate with crystals evenly distributed on it, which cannot fit perfectly on the inside of the device tube wall, resulting in gaps between the modules. This spacing is difficult to avoid with existing technical processes and structural designs.

[0044] Due to the gaps between the detector modules, photons in some areas cannot be detected, resulting in missing information when calculating the system matrix. This missing information appears as obvious horizontal or vertical line artifacts during image reconstruction, affecting the uniformity and detail accuracy of imaging, especially in the annular detection area.

[0045] In order to solve the artifact problem caused by the radial detection module spacing, when calculating the spatial position of the crystal, the present application regards the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, such as Figure 6 As shown. This morphological change causes a slight shift in the center position of the crystal, but the magnitude of the shift is small and can be ignored. By recalculating the crystal coordinates of all detection modules, the data loss caused by the gap is eliminated. This method essentially optimizes the reconstruction assumptions of the detector geometry to make data acquisition closer to the ideal gap-free state. Compared with physically improving the detector design (such as bending the detector module), this coordinate adjustment-based solution is more realistic and does not require complex and expensive changes to the hardware. By adjusting the computational model and coordinates, the purpose of optimized imaging can be achieved without changing the device hardware.

[0046] By assuming the detection module to be an arc and optimizing the crystal coordinates, the artifacts caused by the detection module spacing were successfully reduced, making the image more uniform and richer in detail, especially avoiding obvious line artifacts in the image. The elimination of spacing artifacts makes PET imaging more accurate, improves the resolution and structural clarity of the image, especially in the detail performance of key areas, and the reliability of diagnosis is further improved.

[0047] In view of the three hardware problems existing in the above PET equipment, this application will be specifically described from the method side embodiment. Figure 7 , which shows a schematic flow chart of a method for determining the spatial position of a crystal provided by an embodiment of the present application. The method is applied to the above-mentioned PET device 110 including an annular detector, wherein the annular detector is composed of a plurality of detection modules arranged in a radial annular manner and arranged at intervals in the axial direction, each of the detection modules comprising an array of a plurality of actual crystals, and the method may include the following steps: Step 401: Introduce virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and regard the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals.

[0048] Among them, real crystals refer to solid substances that actually exist in nature or laboratories, and virtual crystals refer to crystal models constructed in computer simulations, which are used to study the properties and behaviors of crystals without actual preparation and experiments.

[0049] In some examples, the step of introducing a virtual crystal between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector includes: Determining the spacing distance between the axially spaced detection modules; Taking the integer of the quotient of the spacing distance and the length of a single actual crystal to obtain the target number; Introducing the target number of virtual crystals between the axially spaced detection modules; The quotient of the depth of the annular detector and the number of the virtual crystals and the actual crystals in the axial direction is determined as the length of each crystal.

[0050] For example, if the spacing between the axially spaced detection modules in the PET device to be simulated is 52nm, and the length of the actual crystal is 25nm, then 52 / 25=2.08, and 2.08 is rounded to the nearest integer, so the target number is 2, so 2 virtual crystals can be introduced between the detection modules. It should be noted that the spacing between the axially spaced detection modules in the current PET device is usually about the length of one crystal, and the difference is not too large.

[0051] For example, if the depth of the annular detector is H, the number of virtual crystals is Nv, and the number of actual crystals is Nf, the length of each crystal after reconstruction is H / (Nv+Nf). It should be noted that since there are gaps between adjacent crystals on the axially spaced detection modules, the above method actually also performs the same operation on adjacent crystals on the axially spaced detection modules. Figure 5 Processing shown.

[0052] In some examples, the step of considering the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector includes: The radially annularly arranged detection modules are regarded as arcs that fit the inner wall of the annular detector; The quotient of the circumference of the annular detector and the number of the actual crystals in the radial direction is determined as the width of each crystal.

[0053] Furthermore, if the spacing distance between the detection modules arranged in a radial annular shape is also relatively large, for example, greater than or equal to the width of one crystal, a virtual crystal may be introduced between the detection modules arranged in a radial annular shape, and then the width of the crystal may be determined by the method of the above embodiment. It should be noted that the spacing distance between the detection modules arranged in a radial annular shape in current PET equipment is usually relatively small, much smaller than the width of one crystal, and therefore can be ignored, and the width of the reconstructed crystal can be obtained by directly dividing the circumference of the annular detector by the number of actual crystals in the radial direction.

[0054] Step 402: Determine the size of the crystal according to the length of the crystal and the width of the crystal.

[0055] For example, if the length of the reconstructed crystal is 25 nm and the width is 20 nm, the size of the reconstructed crystal can be determined to be 20 nm×20 nm×25 nm. Step 403: Determine the spatial position of each of the crystals according to the size of the crystal.

[0056] For example, after the size of the crystal is determined, a suitable coordinate system can be selected to determine the spatial position of each crystal. The selected coordinate system can be a spherical coordinate system, a cylindrical coordinate system, a rectangular coordinate system, or a polar coordinate system, and the origin of the coordinate can be the center point of the annular detector or the position of the center of the circle on its bottom surface, which is not limited here.

[0057] In some examples, determining the spatial position of each of the crystals according to the size of the crystals includes: Establishing a rectangular coordinate system and numbering each of the crystals, wherein the direction of the y-axis of the rectangular coordinate system is the axial direction of the annular detector, and the plane formed by the x-axis and the z-axis of the rectangular coordinate system is the radial plane of the annular detector; Determine the polar angle according to the number of each crystal and the unit center angle, wherein the unit center angle is equal to the quotient of 2π and the number of the actual crystals in the radial direction; Determine the x-coordinate and z-coordinate of each of the crystals according to the polar angle and the radius of the annular detector, and determine the y-coordinate of each of the crystals according to the number of each of the crystals and the length of each of the crystals; The spatial position of each of the crystals is determined according to the x-coordinate, y-coordinate and z-coordinate of each of the crystals.

[0058] In some examples, the serial numbers of the crystals increase axially from one side of the annular detector to the other side, the axial number of the first circle of crystals on one side of the annular detector is 0, and determining the y coordinate of each crystal according to the number of each crystal and the length of each crystal includes: The product of the axial number of each crystal and the length of each crystal plus half the length of the crystal is taken as the y coordinate of each crystal.

[0059] Exemplarily, numbering each crystal includes numbering each crystal in the axial direction and in the radial direction. If the crystal numbered as 0 is determined, and then the numbering method is determined, the serial numbers of all the crystals can be determined. In an embodiment provided by the present application, for example, one side is a side close to the scanning object (the object to be detected), and the other side is a side away from the scanning object (the object to be detected), the coordinate origin of the rectangular coordinate system is the center of one side, and the x-axis and the z-axis are two perpendicular radial directions, such as Figure 8 The radial numbering method is that the numbers increase gradually in the clockwise direction. The crystal number on the positive x-axis is 0, and the radial numbers of the remaining crystals can be determined.

[0060] Exemplarily, after the radial number of the crystal is determined as above, its polar angle θ can be determined by the radial number n of the crystal and the unit center angle α, θ=nα, and then the x-coordinate and z-coordinate of each crystal are determined according to the polar angle and the radius R of the annular detector, the x-coordinate is Rcosθ, and the z-coordinate is Rsinθ. The unit center angle α is equal to the quotient of 2π and the number of actual crystals in the radial direction. The radius of the annular detector can be determined according to the circumference of the annular detector. If the circumference of the annular detector is L, the radius R=L / 2π. For example, if each circle includes 1000 crystals, the unit center angle is 2π / 1000, and the polar angle θ of the crystal with radial number 5 is 5×2π / 1000=π / 100. L=1000×20nm, R=10000nm / π.

[0061] Exemplarily, the product of the axial number of the crystal and the length of the crystal plus half of the length of the crystal is used as the y coordinate of the crystal. For example, if the length of the reconstructed crystal is 25 nm, the y coordinate of the crystal with axial number 4 is 4×25 nm+25 nm / 2=112.5 nm.

[0062] It can be seen that the present application is applied to a positron emission tomography device including an annular detector, which is composed of a plurality of detection modules arranged in a radial annular manner and arranged at intervals in the axial direction, each detection module including an array composed of a plurality of actual crystals, and by introducing virtual crystals between the detection modules arranged at intervals in the axial direction, when calculating the length of each crystal according to the depth of the annular detector, the crystal includes the virtual crystal and the actual crystal, so that the response line of the virtual crystal is regarded as a real response line, thereby filling the data gap in the system matrix, improving the edge clarity and structural integrity of the image, and making the final generated PET image clearer; at the same time, the detection modules arranged in a radial annular manner are regarded as arcs that fit the inner wall of the annular detector, which can eliminate In addition to the fact that photons in some areas of the detection module cannot be detected due to gaps in the radial direction, resulting in line artifacts caused by missing information when calculating the system matrix; in addition, calculating the width of each crystal based on the circumference of the annular detector is equivalent to reconstructing the original crystal width, which is beneficial to eliminating line artifacts caused by differences in the distances between the endpoints of adjacent response lines due to different intervals between crystals; it can be seen that after the above processing, the size of the crystal is determined based on the length and width of the crystal, and the spatial position of each crystal is determined based on the size of the crystal. The recalculated crystal spatial position can be used to calculate the system matrix and reconstruct PET images through the system matrix, which can effectively remove line artifacts caused by hardware problems of the PET device.

[0063] According to the above-mentioned method for determining the spatial position of the crystal, the present application further provides a method for reconstructing a positron emission tomography image, please refer to Fig. 9, which shows a flow chart of a positron emission tomography image reconstruction method provided by an embodiment of the present application. The positron emission tomography image reconstruction method comprises the following steps: Step 501: determining the spatial position of each crystal in the annular detector according to any one of the above methods for determining the spatial position of a crystal; Step 502: determining a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used to describe the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; Step 503: Reconstruct the PET image according to the system matrix.

[0064] There are many methods for determining the system matrix according to the spatial position of the crystal. For example, the following references can be referred to: [1] Siddon, RL Fast calculation of the exact radiological path for a three-dimensional CT array[J]. Medical Physics, 1985, 12(2):252-255. [2] Zhang, B., LS Wang, SJ Zhao. Implementation of DynamicRay Tracing Method in PET Tomography Reconstruction. Journal of ZhengzhouUniversity(Natural Science Edition), 2012,44(03):69-73. [3] Schretter C. A fast tube of response ray-tracer[J]. MedicalPhysics, 2007, 33(12):4744-4748. There are also many methods for reconstructing positron emission tomography images based on the system matrix. For example, the following references can be referred to: [1] Kaufman, Linda. Implementing and Accelerating the EM Algorithm for Positron Emission Tomography[J]. IEEE Transactions on Medical Imaging, 1987, 6(1):37-43. [2] Moses, WW Recent developments in iterative imagereconstruction for PET and SPECT [Editorial][J]. IEEE Transactions on MedicalImaging, 2000, 19(4):P.257-260. It should be noted that each row of the system matrix corresponds to a LOR, i.e., the line between a pair of crystals, and each column corresponds to a voxel of the image. It can be seen that in the embodiment of the present application, the crystal includes a virtual crystal and an actual crystal, then the response line LOR also includes a real LOR and a virtual LOR. Compared with the previous LOR that only includes the LOR of the real crystal, the system matrix of the present application is larger, which can fill the data missing in the original system matrix, improve the edge clarity and structural integrity of the image, and make the final generated PET image clearer; at the same time, the detection module arranged in a radial ring is regarded as an arc that fits the inner wall of the ring detector, which can eliminate the line artifacts caused by the absence of the system matrix calculation due to the existence of gaps in the radial direction of the detection module, and the photons in some areas cannot be detected; in addition, calculating the width of each crystal according to the circumference of the ring detector is equivalent to reconstructing the original crystal width, which is conducive to eliminating the line artifacts caused by the difference in the distance between the endpoints of adjacent response lines due to the different intervals between the crystals; it can be seen that after the above processing, the size of the crystal is determined according to the length and width of the crystal, and the spatial position of each crystal is determined according to the size of the crystal. When the recalculated crystal spatial position is used to calculate the system matrix and reconstruct the PET image through the system matrix, it can effectively remove the line artifacts caused by the hardware problem of the PET device.

[0065] In order to verify the effect of this method, the three-dimensional slices of the system matrix before and after the removal of the interval were compared. The system matrix is ​​a very large two-dimensional matrix. The horizontal axis is the number of valid LORs (the equipment used in the experiment contains 24,000 real crystals and 900 imaginary crystals), which is about 200 million, and the vertical axis is the number of voxels (the voxel side length defined in the experiment is half the width of the crystal), which is about 8 million. Since the storage and inspection of the system matrix are very difficult, we add the corresponding system matrices of all LORs passing through a voxel as the sensitivity factor of the voxel, so we get a three-dimensional matrix of sensitivity factors that is consistent with the size of the reconstructed image. Reference Fig.10 and Fig.11 , Fig.10 and Fig.11 They are three-dimensional slice diagrams of sensitivity factors before and after removing the intervals provided by an embodiment of the present application. Among them, Fig.10 and Fig.11 The left image is the sagittal plane, the middle image is the cross-section, and the right image is the coronal plane.

[0066] It can be seen that through the method provided by this invention, the clarity and accuracy of the sensitivity factor slice converted by the system matrix have been significantly improved, especially the artifact problem caused by the detection module spacing, crystal spacing and cylinder wall detection module spacing has been effectively removed. This method is suitable for clinical diagnosis and research of high-precision medical images, and helps to improve the application effect and reliability of PET technology.

[0067] Fig.12 The schematic diagram of the structure of a device for determining the spatial position of a crystal provided by an embodiment of the present application is shown. The device is applied to a positron emission tomography device including an annular detector, wherein the annular detector is composed of a plurality of detection modules arranged in an annular manner in the radial direction and arranged at intervals in the axial direction, and each of the detection modules includes an array composed of a plurality of actual crystals, including: A crystal size calculation unit 601 is used to introduce virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and to regard the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals; A crystal size determination unit 602, configured to determine the size of the crystal according to the length of the crystal and the width of the crystal; The crystal spatial position determining unit 603 is used to determine the spatial position of each of the crystals according to the size of the crystal.

[0068] Fig.13The schematic diagram of the structure of a positron emission tomography image reconstruction device provided by an embodiment of the present application is shown. The device comprises: A crystal spatial position determining unit 701, configured to determine the spatial position of each crystal in the annular detector according to any one of the above-mentioned crystal spatial position determining methods; A system matrix determination unit 702, configured to determine a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used to describe the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; The image reconstruction unit 703 is used to reconstruct the positron emission tomography image according to the system matrix.

[0069] Fig.14 A schematic diagram of the structure of a computer device provided in one embodiment of the present application is shown, which includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the functions of the computer system of the method for determining the spatial position of the crystal or the method for reconstructing the positron emission tomography image in any of the above-mentioned embodiments are implemented.

[0070] An embodiment of the present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a computer, the computer executes the functions of a computer system of the method for determining the spatial position of a crystal or the method for reconstructing a positron emission tomography image in any of the above-mentioned embodiments.

[0071] The embodiments of the present application also provide a computer program product comprising instructions, which, when executed by a computer, enables the computer to perform the functions of the computer system of the XXX method in any of the above embodiments.

[0072] It should be understood that the specific examples in this application are only intended to help those skilled in the art to better understand the embodiments of the present application, rather than to limit the scope of the present invention.

[0073] It can be understood that in the various implementations of the present application, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation methods of the present application.

[0074] It can be understood that the various embodiments described in this application can be implemented individually or in combination, and the embodiments of this application are not limited to this.

[0075] Unless otherwise stated, all technical and scientific terms used in the embodiments of the present application have the same meaning as those generally understood by those skilled in the art of the technical field of the present application. The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present application. The term "and / or" used in the present application includes any and all combinations of one or more related listed items. The singular forms of "a kind of", "above" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0076] It can be understood that the processor of the embodiment of the present application can be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method implementation can be completed by the hardware integrated logic circuit or software instructions in the processor. The above processor can be a general processor, a digital signal processor (DigitalSignal Processor, DSP), an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiment of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiment of the present application can be directly embodied as a hardware decoding processor to perform, or the hardware and software modules in the decoding processor are combined and executed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0077] It is understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memory. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (programmable ROM, PROM), an erasable programmable read-only memory (erasable PROM, EPROM), an electrically erasable programmable read-only memory (EEPROM) or a flash memory. The volatile memory may be a random access memory (RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0078] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0079] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method implementation methods and will not be repeated here.

[0080] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device implementation described above is only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0081] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0082] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0083] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of each implementation method of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0084] The above are only specific embodiments of the present application, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for determining the spatial position of a crystal, characterized in that: Applied to a positron emission tomography device including an annular detector, the annular detector is composed of a plurality of detection modules arranged in an annular manner in the radial direction and arranged at intervals in the axial direction, each of the detection modules comprising an array composed of a plurality of actual crystals, the method comprising: Introducing virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and regarding the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals; Determining the size of the crystal according to the length of the crystal and the width of the crystal; The spatial position of each of the crystals is determined according to the size of the crystal.

2. The method according to claim 1, characterized in that: The step of introducing virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector comprises: Determining the spacing distance between the axially spaced detection modules; Taking the integer of the quotient of the spacing distance and the length of a single actual crystal to obtain the target number; Introducing the target number of virtual crystals between the axially spaced detection modules; The quotient of the depth of the annular detector and the number of the virtual crystals and the actual crystals in the axial direction is determined as the length of each crystal.

3. The method according to claim 1, characterized in that: The step of regarding the radially annularly arranged detection modules as arcs that fit the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector includes: The radially annularly arranged detection modules are regarded as arcs that fit the inner wall of the annular detector; The quotient of the circumference of the annular detector and the number of the actual crystals in the radial direction is determined as the width of each crystal.

4. The method according to claim 1, characterized in that: Determining the spatial position of each of the crystals according to the size of the crystals comprises: Establishing a rectangular coordinate system and numbering each of the crystals, wherein the direction of the y-axis of the rectangular coordinate system is the axial direction of the annular detector, and the plane formed by the x-axis and the z-axis of the rectangular coordinate system is the radial plane of the annular detector; Determine the polar angle according to the number of each crystal and the unit center angle, wherein the unit center angle is equal to the quotient of 2π and the number of the actual crystals in the radial direction; Determine the x-coordinate and z-coordinate of each of the crystals according to the polar angle and the radius of the annular detector, and determine the y-coordinate of each of the crystals according to the number of each of the crystals and the length of each of the crystals; The spatial position of each of the crystals is determined according to the x-coordinate, y-coordinate and z-coordinate of each of the crystals.

5. The method according to claim 4, characterized in that The serial numbers of the crystals increase axially from one side of the annular detector to the other side, the axial number of the first circle of crystals on one side of the annular detector is 0, and the y coordinate of each crystal is determined according to the number of each crystal and the length of each crystal, including: The product of the axial number of each crystal and the length of each crystal plus half the length of the crystal is taken as the y coordinate of each crystal.

6. A positron emission tomography image reconstruction method, characterized in that: The method comprises: Determine the spatial position of each of the crystals in the annular detector according to the method described in any one of claims 1 to 5; Determine a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used to describe the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; The positron emission tomography image is reconstructed according to the system matrix.

7. A device for determining the spatial position of a crystal, characterized in that: Applicable to a positron emission tomography device including an annular detector, the annular detector is composed of a plurality of detection modules arranged in an annular manner in the radial direction and arranged at intervals in the axial direction, each of the detection modules includes an array composed of a plurality of actual crystals, the device comprising: a crystal size calculation unit, configured to introduce virtual crystals between the axially spaced detection modules to calculate the length of each crystal according to the depth of the annular detector, and to regard the radially annularly arranged detection modules as arcs fitted to the inner wall of the annular detector to calculate the width of each crystal according to the circumference of the annular detector, wherein the crystals include the actual crystals and the virtual crystals; a crystal size determination unit, used to determine the size of the crystal according to the length of the crystal and the width of the crystal; The crystal spatial position determining unit is used to determine the spatial position of each of the crystals according to the size of the crystal.

8. A positron emission tomography image reconstruction device, characterized in that: The device comprises: A crystal spatial position determination unit, used for determining the spatial position of each of the crystals in the annular detector according to the method described in any one of claims 1 to 5; A system matrix determination unit, used for determining a system matrix according to the spatial position of each of the crystals, wherein the system matrix is ​​used for describing the probability that the connection lines between all the crystals in the annular detector pass through each voxel, wherein the voxel refers to a basic pixel unit in a three-dimensional image; An image reconstruction unit is used to reconstruct the positron emission tomography image according to the system matrix.

9. An electronic device, characterized in that: include: Processor and memory; The processor is connected to a memory, wherein the memory is used to store a computer program, and the processor is used to call the computer program to execute the method according to any one of claims 1-5 or 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the method according to any one of claims 1 to 5 or 7 is executed.

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