Systems and methods for modifying a positron emission tomography device

Abstract

The present disclosure relates to a system and method for data masking. The method includes acquiring data associated with coincidence events related to intrinsic background radiation of multiple crystals of a PET device. Each of the coincidence events may be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event may include first time information and second time information. The method includes determining a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information. The method includes determining a second TOF difference corresponding to each coincidence event based on the locations of the two crystals that detect each coincidence event. The method includes modifying the PET device based on the first TOF difference and the second TOF difference.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Chinese Patent Application No. 202110405984.1, filed on April 15, 2021, the contents of which are hereby incorporated by reference.

[0002] The present disclosure relates generally to systems and methods for positron emission tomography (PET) devices, and more particularly to systems and methods for modifying PET devices. [Background technology]

[0003] Positron emission tomography (PET) is widely used in medicine for diagnostic and other purposes. Accurate assessment of a patient's disease relies on accurate acquisition of PET data. However, due to aging of PET device components and external environmental influences, the state of the PET device (e.g., energy state, time-of-flight (TOF) state) may be changed, which may affect the quality of the PET data acquired by the PET device. Conventionally, an external radiation source may be introduced to modify the state of the PET device, which may result in unnecessary radiation to operators and increase the downtime of the PET device. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, it would be desirable to provide a system and method for accurately and efficiently calibrating a PET device. [Means for solving the problem]

[0005] According to aspects of the present disclosure, a method may be implemented in a computer device having one or more processing units and one or more storage devices. The method may include acquiring data associated with coincidence events related to intrinsic background radiation of multiple crystals of a PET device. Each of the coincidence events may be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event may include first time information and second time information. The method may include determining a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information. The method may include determining a second TOF difference corresponding to each coincidence event based on locations of the two crystals detecting each coincidence event. The method may include correcting the PET device based on the first TOF difference and the second TOF difference.

[0006] In some embodiments, each of the coincident events may include a β event and a γ event, and the first time information may correspond to the β event and the second time information may correspond to the γ event.

[0007] In some embodiments, the method may include, for each coincidence event, acquiring a first optical signal excited by a beta particle and a second optical signal excited by a gamma particle. The method may include acquiring a first electrical signal by converting the first optical signal. The method may include acquiring a second electrical signal by converting the second optical signal. The method may include determining first time information based on the first electrical signal. The method may include determining second time information based on the second electrical signal.

[0008] In some embodiments, the method may include acquiring data associated with the coincidence events based on a target energy window and a target time window. The target energy window may be determined based on at least one of a beta particle energy, a gamma particle energy, or a reference energy. The target time window may be determined based on a reference time.

[0009] In some embodiments, a first of the two crystals is capable of detecting beta particles and a second of the two crystals is capable of detecting gamma particles, and the method may include determining a second TOF difference based on a distance between a location of the first crystal and a location of the second crystal.

[0010] In some embodiments, the method may include determining a second TOF difference by dividing the distance between the location of the first crystal and the location of the second crystal by the speed of light.

[0011] In some embodiments, a first detector including a first crystal and a second detector including a second crystal may be spaced apart from each other.

[0012] In some embodiments, the method may include generating a time spectrum for each crystal of a plurality of crystals in a PET device based on a first TOF difference and a second TOF difference corresponding to each of one or more of the coincidence events detected between the crystal and other crystals. The method may include determining a TOF correction value based on the time spectrum. The method may include correcting the PET device based on the TOF correction value corresponding to each crystal of the plurality of crystals in the PET device.

[0013] In some embodiments, the method may include determining a TOF correction value based on a time spectrum from a repeating operation including one or more repeats. In at least one of the one or more repeats, the method may include generating a crystal time spectrum for each crystal of a plurality of crystals in the PET device. The method may include determining an offset value for the crystal based on the time spectrum. The method may include determining whether the repeating operation satisfies a condition based on the offset value for the crystal. Depending on the result of determining whether the repeating operation satisfies a condition based on the offset value for the crystal, the method may include adjusting TOF information for the crystal based on the offset value for the crystal, or determining a TOF correction value for the crystal by summing one or more offset values ​​for the crystal in one or more repeats.

[0014] In some embodiments, the method may include recording the TOF correction values ​​in a correction file of the PET device or programming the TOF correction values ​​into one or more detectors of the PET device.

[0015] In some embodiments, the method may include performing a time walk effect correction and / or a position correction on the first TOF difference.

[0016] In some embodiments, the method may include modifying the PET device based on energy information of the data associated with the coincidence events.

[0017] In some embodiments, the method may include generating a reference energy spectrum based on energy information of each coincidence event. The method may include determining a reference peak position in the reference energy spectrum. The method may include determining a target peak position based on the reference peak position in the reference energy spectrum. The method may include modifying energy information of a crystal of a PET device based on the target peak position and the modified peak position.

[0018] In some embodiments, the method may include determining whether energy information of a crystal of the PET device needs to be modified based on the target peak position and the modified peak position. The method may include programming the target peak position into one or more detectors of the PET device in response to determining that the energy information of the crystal of the PET device needs to be modified.

[0019] In some embodiments, the method may include determining a target peak position based on a reference peak position and a relationship between the position of the peak and the energy of the peak.

[0020] According to another aspect of the present disclosure, a system may include at least one storage device storing a set of instructions and at least one processing device in communication with the at least one storage device. When executing the stored set of instructions, the at least one processing device may cause the system to perform a method. The method may include acquiring data associated with coincidence events related to intrinsic background radiation of multiple crystals of a PET device. Each of the coincidence events may be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event may include first time information and second time information. The method may include determining a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information. The method may include determining a second TOF difference corresponding to each coincidence event based on locations of the two crystals detecting each coincidence event. The method may include correcting the PET device based on the first TOF difference and the second TOF difference.

[0021] According to another aspect of the present disclosure, a non-transitory computer-readable medium may include at least one set of instructions. When executed by at least one processing unit of a computing device, the at least one set of instructions may cause the at least one processing unit to perform a method. The method may include acquiring data associated with coincidence events related to intrinsic background radiation of multiple crystals of a PET device. Each of the coincidence events may be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event may include first time information and second time information. The method may include determining a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information. The method may include determining a second TOF difference corresponding to each coincidence event based on locations of the two crystals detecting each coincidence event. The method may include correcting the PET device based on the first TOF difference and the second TOF difference.

[0022] Additional features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon review of the following and the accompanying drawings, or may be learned by the fabrication or operation of the examples. Features of the present disclosure may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities, and combinations that are set forth in the detailed examples discussed below.

[0023] The present disclosure will be further described in terms of exemplary embodiments. These exemplary embodiments will be described in detail with reference to the drawings. The drawings are not to scale. These embodiments are non-limiting exemplary embodiments, and like reference numerals represent like structure throughout the several views of the drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram illustrating an exemplary medical system according to some embodiments of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating exemplary hardware and / or software components of an exemplary computing device in which a processing device may be implemented according to some embodiments of the present disclosure. [Figure 3] 1 is a schematic diagram illustrating example hardware and / or software components of an example mobile device in which a terminal may be implemented according to some embodiments of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram illustrating an example processing device according to some embodiments of the present disclosure. [Figure 5] 1 is a flow chart illustrating an example process for modifying a PET device, according to some embodiments of the present disclosure. [Figure 6] 1 is a flow chart illustrating an example process for determining a TOF correction value according to some embodiments of the present disclosure. [Figure 7] 1 is a flow chart illustrating an example process for modifying a PET device, according to some embodiments of the present disclosure. [Figure 8] FIG. 1 illustrates an exemplary intrinsic background radiation of a crystal in a PET device, according to some embodiments of the present disclosure. [Figure 9] FIG. 1 illustrates an example time spectrum according to some embodiments of the present disclosure. [Figure 10] FIG. 1 illustrates an example reference energy spectrum according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] In the following detailed description, numerous specific details are set forth by way of example to provide a thorough understanding of the relevant disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well-known methods, procedures, systems, components, and / or circuits have been described at a relatively high level, without detail, to avoid unnecessarily obscuring aspects of the present disclosure. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the broad principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the claims.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. As used herein, the terms "and / or" and "at least one of" include any and all combinations of one or more of the associated listed items. It is further understood that the terms "comprising," "comprising," "including," and / or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Additionally, the term "exemplary" is intended to refer to an example or illustration.

[0027] It is understood that the terms "system," "engine," "unit," "module," and / or "block" used herein are a way of distinguishing between different components, elements, parts, sections, or assemblies at different levels in ascending order. However, the terms may be substituted by other expressions that achieve the same purpose.

[0028] Aspects of the present disclosure relate to systems and methods for correcting a PET device. According to some embodiments of the present disclosure, a processing device can acquire data associated with coincidence events related to intrinsic background radiation of multiple crystals of the PET device. Each of the coincidence events can be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event can include first time information and second time information. The processing device can determine a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information. The processing device can determine a second TOF difference corresponding to each coincidence event based on locations of the two crystals that detect each coincidence event. The processing device can correct a TOF state of the PET device based on the first TOF difference and the second TOF difference.

[0029] Another aspect of the present disclosure relates to a system and method for modifying a PET device. According to some embodiments of the present disclosure, a processing device can acquire data associated with a single event or a coincidence event related to intrinsic background radiation of a crystal of the PET device. The processing device can generate a reference energy spectrum based on energy information of the single event or the coincidence event. The processing device can determine a reference peak position in the reference energy spectrum. The processing device can determine a target peak position based on the reference peak position in the reference energy spectrum. The processing device can determine an energy modification state based on the target peak position and the modified peak position. The processing device can modify an energy state of the PET device based on the energy modification state.

[0030] Thus, the state of the PET device (e.g., TOF state, energy state) can be modified based on data associated with a single event or coincidence events related to the intrinsic background radiation of multiple crystals in the PET device without the use of an external radiation source, reducing the radiation exposure of PET device operators and reducing the cost of PET device modification.

[0031] FIG. 1 is a schematic diagram illustrating an example medical system according to some embodiments of the present disclosure. As shown, medical system 100 may include a medical device 110, a processing device 120, a storage device 130, a terminal 140, and a network 150. The components of medical system 100 may be connected in one or more of a variety of ways. By way of example only, as shown in FIG. 1, medical device 110 may be connected to processing device 120 directly, as indicated by the dotted double-headed arrow connecting medical device 110 and processing device 120, or through network 150. As another example, storage device 130 may be connected to medical device 110 directly, as indicated by the dotted double-headed arrow connecting medical device 110 and storage device 130, or through network 150. As yet another example, terminal 140 may be connected to processing device 120 directly, as indicated by the dotted double-headed arrow connecting terminal 140 and processing device 120, or through network 150.

[0032] In some embodiments, the medical device 110 can scan a subject and acquire data regarding the subject. In some embodiments, the medical device 110 can be an emission computed tomography (ECT) device, a positron emission tomography (PET) device, a single photon emission computed tomography (SPECT) device, a multi-modality device, etc., or any combination thereof. Exemplary multi-modality devices can include CT-PET devices, MR-PET devices, etc. In some embodiments, the multi-modality device can include modules and / or components for performing PET imaging and / or related analyses.

[0033] In some embodiments, the medical device 110 may be a PET device including a gantry 111, a PET detector 112, a detection region 113, and a table 114. The PET detector 112 can detect radiation events (e.g., gamma photons) emitted from the detection region 113. In some embodiments, the PET detector 112 may include multiple detectors. The PET detector 112 may be a single-row detector in which multiple detectors are arranged in a single row, and / or a multi-row detector in which multiple detectors are arranged in multiple rows. In some embodiments, each detector of the multiple detectors may include a crystal (e.g., a scintillator), a light guide, and a photoelectric conversion device. The crystal may include different types of compounds. Exemplary compounds may include bismuth germanate (BGO), barium fluoride (BaFl), gadolinium silicate (GSO), lutetium orthosilicate (LSO), lutetium yttrium orthosilicate (LYSO), etc., or any combination thereof. The light guide can be optically coupled to the crystal to provide a light path to the photoelectric conversion device. During a PET scan of a subject, incident gamma rays can strike the crystal to produce small bursts of visible or invisible light (e.g., optical signals). The visible or invisible light can be converted into an electrical signal (e.g., an electrical pulse signal) by the photoelectric conversion device. In some embodiments, the photoelectric conversion device can include a photomultiplier tube (PMT), a silicon photomultiplier tube (SiPM), an avalanche photodiode (APD), or the like, or any combination thereof.

[0034] The processing device 120 can process data and / or information acquired from the medical device 110, the storage device 130, and / or the terminal 140. For example, the processing device 120 can acquire data associated with a coincidence event related to the intrinsic background radiation of multiple crystals of the PET device. As another example, the processing device 120 can determine a first TOF difference corresponding to the coincidence event based on first time information and second time information. As another example, the processing device 120 can determine a second TOF difference corresponding to the coincidence event based on the locations of two crystals that detect the coincidence event. As yet another example, the processing device 120 can correct the TOF state of the PET device based on the first TOF difference and the second TOF difference.

[0035] In some embodiments, processing device 120 may be a single server or a group of servers. The server group may be centralized or distributed. In some embodiments, processing device 120 may be local or remote. For example, processing device 120 may access data and / or information from medical device 110, storage device 130, and / or terminal 140 via network 150. As another example, processing device 120 may be directly connected to medical device 110, storage device 130, and / or terminal 140 to access data and / or information. In some embodiments, processing device 120 may be implemented on a cloud platform. For example, the cloud platform may include a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an intercloud, a multicloud, etc., or a combination thereof. In some embodiments, processing device 120 may be part of terminal 140. In some embodiments, processing device 120 may be part of medical device 110.

[0036] The storage device 130 can store data, instructions, and / or any other information. In some embodiments, the storage device 130 can store data acquired from the medical device 110, the processing device 120, and / or the terminal 140. The data can include image data acquired by the processing device 120, algorithms, and / or algorithms for processing the image data. For example, the storage device 130 can store data associated with coincidence events related to the intrinsic background radiation of multiple crystals of a PET device. As another example, the storage device 130 can store first and second TOF differences corresponding to coincidence events determined by the processing device 120. As yet another example, the storage device 130 can store reference energy spectra determined by the processing device 120. In some embodiments, the storage device 130 can store data and / or instructions that the processing device 120 and / or the terminal 140 can execute or use to implement example methods described in this disclosure. In some embodiments, the storage device 130 may include mass storage, removable storage, volatile read-and-write storage, read-only storage (ROM), etc., or any combination thereof. Exemplary mass storage may include magnetic disks, optical disks, solid-state drives, etc. Exemplary removable storage may include flash drives, floppy disks, optical disks, memory cards, zip disks, magnetic tape, etc. Exemplary volatile read-and-write storage may include random access memory. Exemplary RAM may include dynamic RAM (DRAM), double-date rate synchronous dynamic RAM (DDR SDRAM), static RAM (SRAM), thyristor RAM (T-RAM), zero-capacitor RAM (Z-RAM), etc.Exemplary ROM may include masked ROM (MROM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), compact disc ROM (CD-ROM), digital versatile disc ROM, etc. In some embodiments, storage device 130 may be implemented in a cloud platform. By way of example only, the cloud platform may include a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an intercloud, a multicloud, etc., or any combination thereof.

[0037] In some embodiments, the storage device 130 can be connected to a network 150 for communication with one or more other components in the medical system 100 (e.g., the processing device 120, the terminal 140). One or more components in the medical system 100 can access data or instructions stored on the storage device 130 via the network 150. In some embodiments, the storage device 130 can be incorporated into the medical device 110.

[0038] The terminal 140 can be connected to and / or communicate with the medical device 110, the processing device 120, and / or the storage device 130. In some embodiments, the terminal 140 can include a mobile device 141, a tablet computer 142, a laptop computer 143, etc., or any combination thereof. For example, the mobile device 141 can include a mobile phone, a personal digital assistant (PDA), a gaming device, a navigation device, a point-of-sale (POS) device, a laptop, a tablet computer, a desktop, etc., or any combination thereof. In some embodiments, the terminal 140 can include input devices, output devices, etc. Input devices can include alphanumeric and other keys that can be input via a keyboard, a touchscreen (e.g., with haptic or tactile feedback), voice input, eye-tracking input, a brain monitoring system, or any other equivalent input mechanism. Other types of input devices can include cursor control devices such as a mouse, a trackball, or cursor direction keys. Output devices can include a display device, a printer, etc., or any combination thereof.

[0039] Network 150 may include any suitable network capable of facilitating the exchange of information and / or data for medical system 100. In some embodiments, one or more components of medical system 100 (e.g., medical device 110, processing device 120, storage device 130, terminal 140, etc.) may communicate information and / or data with one or more other components of medical system 100 via network 150. For example, processing device 120 and / or terminal 140 may obtain data associated with coincidence events related to the intrinsic background emissions of multiple crystals of a PET device via network 150. As another example, processing device 120 and / or terminal 140 may obtain information stored in storage device 130 via network 150. Network 150 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., an Ethernet network), 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, etc. For example, network 150 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, network 150 may include one or more network access points.For example, network 150 may include wired and / or wireless network access points, such as base stations and / or Internet interconnection points through which one or more components of medical system 100 may be connected to network 150 to exchange data and / or information.

[0040] This description is intended to be illustrative and not to limit the scope of the present disclosure. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein can be combined in various ways to yield additional and / or alternative exemplary embodiments. However, these variations and modifications do not depart from the scope of the present disclosure. In some embodiments, the medical system 100 may include one or more additional components and / or one or more components of the medical system 100 previously described may be omitted. Additionally or alternatively, two or more components of the medical system 100 may be combined into a single component. A component of the medical system 100 may be implemented in two or more subcomponents.

[0041] In some embodiments, a PET system may include a detector subsystem, an electronics system, a data correction subsystem, and / or a reconstruction subsystem. During a PET scan of a subject (e.g., a patient), after a PET tracer is introduced into the subject, the PET tracer molecule can emit a positron, an antiparticle of an electron. A positron has the same mass and opposite charge as an electron and undergoes annihilation (also referred to as an "annihilation event," "coincidence event," or "clinical coincidence event") with an electron (which may be naturally abundant in the subject) when the two particles collide. Electron-positron annihilation can result in two particles (e.g., two 511 keV gamma photons) that begin to move in opposite directions relative to each other upon their own generation. In some embodiments, each gamma photon can strike a crystal in the detector system to produce a small burst of visible or invisible light (e.g., a light signal). The visible or invisible light can be converted into an electrical signal by a photoelectric conversion device coupled to the crystal. The electrical signals may be sent to a front-end circuit of the electronic system for waveform size or shape, noise, filtering, and / or discriminant logic selection. The processed electronic signals may be sent to a back-end circuit of the electronic system for digital processing to obtain position, time, and / or energy information of the gamma photons. A data correction system may correct the position, time, and / or energy information of the gamma photons to generate coincidence event information associated with the gamma photons. A reconstruction system may generate a PET image based on the coincidence event information.

[0042] 2 is a schematic diagram illustrating example hardware and / or software components of an example computing device 200 in which processing device 120 may be implemented according to some embodiments of the present disclosure. As shown in FIG. 2, computing device 200 may include a processing unit 210, a storage unit 220, an input / output (I / O) 230, and a communication port 240.

[0043] The processing unit 210 can execute computer instructions (e.g., program code) to perform the functions of the processing device 120 in accordance with the techniques disclosed herein. Computer instructions may include, for example, routines, programs, objects, components, data structures, procedures, modules, and functions that perform specific functions described herein. For example, the processing unit 210 can process image data obtained from the medical device 110, the terminal 140, the storage device 130, and / or any other component of the medical system 100. In some embodiments, the processing unit 210 can comprise one or more hardware processing units, such as a microcontroller, a microprocessor, a reduced instruction set computer (RISC), an application specific integrated circuit (ASIC), an application specific instruction set processor (ASIP), a central processing unit (CPU), a graphics processing unit (GPU), a physical processing unit (PPU), a microcontroller unit, a digital signal processor (DSP), a field programmable gate array (FPGA), an advanced RISC machine (ARM), a programmable logic device (PLD), any circuit or processing unit capable of performing one or more functions, or any combination thereof.

[0044] For illustrative purposes only, only one processing device is depicted in computing device 200. However, it should be noted that computing device 200 in the present disclosure may include multiple processing devices. Accordingly, the operations and / or method steps performed by a processing device as described in the present disclosure may be performed by multiple processing devices, either together or separately. For example, in the present disclosure, if a processing device of computing device 200 performs both process A and process B, processes A and B may be performed by two or more different processing devices, either together or separately, in computing device 200 (e.g., a first processing device performs process A and a second processing device performs process B, or the first and second processing devices perform processes A and B together).

[0045] The storage device 220 can store data / information obtained from the medical device 110, the terminal 140, the storage device 130, and / or any other components of the medical system 100. The storage device 220 can be similar to the storage device 130 described in connection with FIG. 1, and a detailed description thereof will not be repeated herein.

[0046] I / O 230 may be input and / or output signals, data, information, etc. In some embodiments, I / O 230 may enable user interaction with processing device 120. In some embodiments, I / O 230 may include input and output devices. Examples of input devices may include a keyboard, a mouse, a touchscreen, a microphone, a recording device, etc., or a combination thereof. Examples of output devices may include a display device, a speaker, a printer, a projector, etc., or a combination thereof. Examples of display devices may include a liquid crystal display (LCD), a light emitting diode (LED)-based display device, a flat panel display, a curved screen, a television, a cathode ray tube (CRT), a touchscreen, etc., or a combination thereof.

[0047] The communication port 240 may be connected to a network (e.g., network 150) to facilitate data communication. The communication port 240 may establish communication between the processing device 120 and the medical device 110, the terminal 140, and / or the storage device 130. The connection may be a wired connection, a wireless connection, any other communication connection capable of enabling the transmission and / or reception of data, and / or any combination of these connections. A wired connection may include, for example, an electrical cable, an optical cable, a telephone line, etc., or any combination thereof. A wireless connection may include, for example, a Bluetooth® link, a Wi-Fi® link, a WiMax® link, a WLAN link, a ZigBee link, a mobile network link (e.g., 3G, 4G, 5G), etc., or any combination thereof. In some embodiments, the communication port 240 may be and / or include a standardized communication port such as RS232, RS485, etc. In some embodiments, the communication port 240 may be a specially designed communication port. For example, the communications port 240 may be designed according to the Digital Imaging and Communications in Medicine (DICOM) protocol.

[0048] 3 is a schematic diagram illustrating example hardware and / or software components of an example mobile device 300 according to some embodiments of the present disclosure. In some embodiments, terminal 140 and / or processing device 120 may each be implemented in mobile device 300.

[0049] 3, mobile device 300 may include a communications platform 310, a display device 320, a graphics processing unit (GPU) 330, a central processing unit (CPU) 340, an I / O 350, memory 360, and storage 390. In some embodiments, any other suitable components may be included in mobile device 300, including, but not limited to, a system bus or controller (not shown).

[0050] In some embodiments, the communications platform 310 may be configured to establish a connection between the portable device 300 and other components of the medical system 100 and / or to enable data and / or signals to be transmitted between the portable device 300 and other components of the medical system 100. For example, the communications platform 310 may establish a wireless connection between the portable device 300 and the medical device 110 and / or the processing device 120. The wireless connection may include, for example, a Bluetooth® link, a Wi-Fi® link, a WiMax® link, a WLAN link, a ZigBee link, a mobile network link (e.g., 3G, 4G, 5G), etc., or any combination thereof. The communications platform 310 may also facilitate data and / or signals between the portable device 300 and other components of the medical system 100. For example, the communications platform 310 may transmit data and / or signals input by a user to other components of the medical system 100. The input data and / or signals may include commands by the user. As another example, the communications platform 310 can receive data and / or signals transmitted from the processing device 120. The received data and / or signals may include image data acquired by a detector of the medical device 110.

[0051] In some embodiments, a mobile operating system (OS) 370 (e.g., iOS®, Android®, Windows Phone®, etc.) and one or more applications (apps) 380 may be loaded from storage 390 into memory 360 for execution by CPU 340. Applications 380 may include a browser or any other suitable mobile app for receiving and displaying information related to motion signal recalibration or other information from processing device 120. User interaction involving information flow may be achieved via I / O 350 and provided via network 150 to processing device 120 and / or other components of medical system 100.

[0052] To implement the various modules, units, and their functionality described in this disclosure, a computer hardware platform may be used as the hardware platform for one or more of the elements described herein. A computer with user interface elements can be used to implement a personal computer (PC), other types of workstations, or terminal devices, although if properly programmed, the computer can also act as a server. Those skilled in the art are assumed to be familiar with the structure, programming, and general operation of such computer equipment, and as a result, the drawings should not require explanation.

[0053] 4 is a block diagram illustrating an example processing device according to some embodiments of the present disclosure. In some embodiments, the processing device 120 may include an acquisition module 410, a determination module 420, and a modification module 430.

[0054] The acquisition module 410 may be configured to acquire data and / or information associated with the medical system 100. The data and / or information associated with the medical system 100 may include data associated with coincidence events related to the intrinsic background radiation of multiple crystals of the PET device, first TOF differences corresponding to the coincidence events, second TOF differences corresponding to the coincidence events, a reference energy spectrum, a reference energy spectrum, a reference peak position in the reference energy spectrum, a target peak position, etc., or any combination thereof. For example, the acquisition module 410 may acquire data associated with a single event or a coincidence event related to the intrinsic background radiation of the crystals of the PET device. Further description of data associated with a single event or a coincidence event related to the intrinsic background radiation of the crystals of the PET device may be found elsewhere in this disclosure (e.g., FIG. 5 and its description). In some embodiments, the acquisition module 410 may acquire data and / or information associated with the medical system 100 from one or more components of the medical system 100 (e.g., the medical device 110, the storage device 130, the terminal 140) via the network 150.

[0055] The determination module 420 may be configured to determine data and / or information associated with the medical system 100. For example, the determination module 420 may determine a first TOF difference corresponding to a coincident event based on the first time information and the second time information. As another example, the determination module 420 may determine a second TOF difference corresponding to a coincident event based on the locations of two crystals that detect the coincident event. Further description of determining a first TOF difference and a second TOF difference may be found elsewhere in this disclosure (e.g., FIG. 5 and its description). As yet another example, the determination module 420 may generate a time spectrum of the crystal. As yet another example, the determination module 420 may determine an offset value for the crystal based on the time spectrum. As yet another example, the determination module 420 may determine whether a repeat operation satisfies a condition based on the offset value. As yet another example, the determination module 420 may adjust the TOF state of the crystal based on the offset value for the crystal. As yet another example, the determination module 420 may determine a TOF correction value for the crystal by summing one or more offset values ​​for the crystal over one or more iterations. As yet another example, the determination module 420 may generate a reference energy spectrum based on energy information of a single event or coincident events. As yet another example, the determination module 420 may determine a reference peak position in the reference energy spectrum. As yet another example, the determination module 420 may determine a target peak position based on the reference peak position in the reference energy spectrum. As yet another example, the determination module 420 may determine an energy correction state based on the target peak position and the corrected peak position.

[0056] The correction module 430 may be configured to correct data and / or information associated with the medical system 100. For example, the correction module 430 may correct a TOF state of the PET device based on the first TOF difference and the second TOF difference. Further description of correcting a TOF state of the PET device may be found elsewhere in this disclosure (e.g., FIG. 5, FIG. 6 and their descriptions). As another example, the correction module 430 may correct an energy state of the PET device based on an energy correction state. Further description of correcting an energy state of the PET device may be found elsewhere in this disclosure (e.g., FIG. 7 and their descriptions).

[0057] It should be noted that the above description of the processing device 120 is provided for illustrative purposes only and is not intended to limit the scope of the present disclosure. Those skilled in the art may make numerous modifications and improvements under the teachings of the present disclosure. However, these modifications and improvements do not depart from the scope of the present disclosure. In some embodiments, one or more modules may be combined into a single module. For example, the determination module 420 and the correction module 430 may be combined into a single module. In some embodiments, one or more modules may be added or omitted in the processing device 120. For example, the processing device 120 may further include a storage module (not shown in FIG. 4 ) configured to store data and / or information associated with the medical system 100 (e.g., data associated with the coincident events, first TOF differences corresponding to the coincident events, second TOF differences corresponding to the coincident events, reference energy spectra, energy correction status of the medical device).

[0058] FIG. 5 is a flow chart illustrating an example process for modifying a TOF status of a PET device, according to some embodiments of the present disclosure. In some embodiments, process 500 may be implemented in medical system 100 shown in FIG. 1. For example, process 500 may be stored in the form of instructions in storage device 130 and / or a storage device (e.g., storage device 220, storage device 390) and may be recalled and / or executed by processing device 120 (e.g., processing unit 210 of computing device 200 as shown in FIG. 2, CPU 340 of mobile device 300 as shown in FIG. 3). The illustrated process operations are intended to be illustrative. In some embodiments, process 500 may be performed with one or more additional operations not described and / or without one or more of the discussed operations. Additionally, the order of operations of process 500 as shown in FIG. 5 and described below is not intended to be limiting.

[0059] At 510, the processing device 120 (e.g., the acquisition module 410) can acquire data associated with coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device. Each of the coincidence events can be detected by two of the multiple crystals of the PET device. The data associated with each coincidence event can include first time information and / or second time information.

[0060] In some embodiments, the PET device may include multiple detectors. The multiple detectors may be arranged in the form of a ring, cylinder, or portion thereof to surround the subject being scanned. In some embodiments, the detector may include a crystal (e.g., a scintillator). In some embodiments, the crystal may emit a specific amount of radiation (also referred to as intrinsic background radiation). For example, a lutetium (Lu)-based crystal (e.g., lutetium orthosilicate (LSO), lutetium yttrium orthosilicate (LYSO)) may contain a radioactive isotope of lutetium (176Lu). When 176Lu decays, it can emit one or more beta particles (with energies ranging from 0 keV to 593 keV) and one or more gamma particles (with energies of 88, 202, or 307 keV).

[0061] In some embodiments, a beta particle emitted from a first crystal (e.g., a lutetium-based crystal) can deposit energy in the first crystal and can only be detected by the first crystal. A gamma particle emitted from a first crystal can be detected not only by the first crystal but also by a second crystal after emitting outside the first crystal. In some embodiments, a single event can include a beta event and a gamma event. A beta event can refer to an event in which a beta particle emitted from a first crystal is detected by the first crystal. A gamma event can refer to an event in which a gamma particle emitted from a first crystal is detected by a second crystal. In some embodiments, if a gamma particle and a beta particle are accepted and interact with the two crystals within a specific time window (e.g., 1 nanosecond, 2 nanoseconds, 5 nanoseconds, 10 nanoseconds, 20 nanoseconds), it can be determined that the gamma and beta events can be considered coincident events because the two particles come from the same intrinsic background radiation.

[0062] In some embodiments, the data associated with the coincidence events associated with the crystal's intrinsic background radiation may include time information, energy information, etc., or a combination thereof. The time information may include first time information and / or second time information. The first time information may correspond to a β event. The second time information may correspond to a γ event. The first time information may include the time when a β particle is detected by the first crystal (also referred to as the detection time of the β particle). The second time information may include the time when a γ particle is detected by the second crystal (also referred to as the detection time of the γ particle).

[0063] In some embodiments, the processing device 120 can acquire a first optical signal excited by a beta particle and a second optical signal excited by a gamma particle. The processing device 120 can acquire a first electrical signal by converting the first optical signal. The processing device 120 can acquire a second electrical signal by converting the second optical signal. For example, the beta particle (and / or the gamma particle) can strike a corresponding crystal to produce a small burst of visible or invisible light (i.e., the first optical signal, the second optical signal). The first optical signal (and / or the second optical signal) can be converted into a first electrical signal (and / or the second electrical signal), respectively, by a photoelectric conversion device coupled to the corresponding crystal. The processing device 120 can determine first time information based on the first electrical signal. The processing device 120 can determine second time information based on the second electrical signal. For example, the processing device 120 can determine the time when the first electrical signal is generated as the detection time of the beta particle. The processing device 120 can determine the time when the second electrical signal is generated as the detection time of the gamma particle.

[0064] FIG. 8 illustrates exemplary intrinsic background radiation of a crystal in a PET device, according to some embodiments of the present disclosure. As illustrated in FIG. 8, the PET device may include a first crystal 810 and a second crystal 820. When the first crystal 810 decays, it can emit a beta particle 830 and at least one gamma particle 840. The beta particle 830 can strike the first crystal 810 to generate a first optical signal (also referred to as a beta event). The gamma particle 840 can be emitted out of the first crystal 810 and strike the second crystal 820 to generate a second optical signal (also referred to as a gamma event). The first optical signal can be converted into a first electrical signal by a first photoelectric conversion device 850 coupled to the first crystal 810. The second optical signal can be converted into a second electrical signal by a second photoelectric conversion device 860 coupled to the second crystal 820. First time information 870 corresponding to a β event can be generated or obtained based on the first electrical signal, and second time information 880 corresponding to a γ event can be generated or obtained based on the second electrical signal.

[0065] In some embodiments, a first detector including a first crystal and a second detector including a second crystal can be spaced apart from each other. In some embodiments, a PET device can include multiple detectors (e.g., a first detector, a second detector, a third detector, a fourth detector, a fifth detector, a sixth detector, a seventh detector, and an eighth detector). The multiple detectors can be arranged in a ring shape. For example, the first detector can be adjacent to the second detector, the second detector can be adjacent to the third detector, the third detector can be adjacent to the fourth detector, the fourth detector can be adjacent to the fifth detector, the fifth detector can be adjacent to the sixth detector, the sixth detector can be adjacent to the seventh detector, the seventh detector can be adjacent to the eighth detector, and the eighth detector can be adjacent to the first detector. In some embodiments, in the inherent background radiation of the crystal of the first detector, a gamma particle emitted from the crystal of the first detector can be detected by the third detector, the fourth detector, the fifth detector, the sixth detector, and the seventh detector, but cannot be detected by the second detector or the eighth detector adjacent to the first detector. It should be noted that a PET device can include any number of detectors, and the multiple detectors can be arranged in any suitable manner. Therefore, because the two crystals detecting the coincidence event are spaced apart from each other, the distance between the two crystals can be relatively long, and the TOF of the gamma particle between the two crystals can be relatively long. Because the magnitude of the parameter associated with the coincidence event is relatively small, increasing the distance between the two crystals detecting the coincidence event can reduce the difficulty of calculating the parameter associated with the coincidence event and improve the calculation accuracy of the parameter associated with the coincidence event.

[0066] In some embodiments, the processing device 120 can acquire data associated with the coincident events based on a target energy window and a target time window. In some embodiments, the target energy window can be determined based on beta particle energy (e.g., 0 keV to 593 keV), gamma particle energy (e.g., 88 keV, 202 keV, 307 keV), a reference energy, etc., or a combination thereof. In some embodiments, the reference energy can be a clinical energy (e.g., 511 keV). In some embodiments, the target energy window can be greater than the beta particle energy, gamma particle energy, and / or the clinical energy. For example, the target energy window can range from 200 keV to 650 keV.

[0067] In some embodiments, the target time window can be determined based on a reference time window (e.g., a clinical time window). For example, the target time window can be larger than the clinical time window. During a PET scan of a subject (e.g., a patient), the subject can be typically positioned at the center of the field of view (FOV) of the PET device, and the annihilation location where two 511 keV gamma photons are generated in a clinical coincidence event can be located on the subject's body. The annihilation location where two particles (e.g., a beta particle and a gamma particle) are generated in a coincidence event with the intrinsic background radiation of the crystal of the PET device can be located on the crystal. That is, the travel distance of the gamma particle generated in a coincidence event with the intrinsic background radiation can be longer than the travel distance of the gamma particle generated in a clinical coincidence event. Therefore, the time it takes for a gamma particle to travel from a first crystal to a second crystal in a coincidence event with the intrinsic background radiation can be longer than the time it takes for a gamma ray to travel from an annihilation location to a corresponding detector of the PET device in a clinical coincidence event. Therefore, the target time window can be larger than the clinical time window, thereby enabling the PET device to acquire data associated with the coincidence event with the intrinsic background radiation of the crystal of the PET device.

[0068] At 520, the processing device 120 (e.g., the determination module 420) can determine a first time-of-flight (TOF) difference corresponding to each coincidence event based on the first time information and the second time information.

[0069] In some embodiments, the first TOF difference can be a measured time difference between two detection times of two particles generated in a coincidence event, for example, the first TOF difference can be a time difference between the detection time of a beta particle (or the detection time of a gamma particle) and the detection time of a gamma particle (or the detection time of a beta particle).

[0070] In some embodiments, the processing device 120 may determine a first TOF difference corresponding to the coincident event based on the first time information and the second time information corresponding to the coincident event. For example, the processing device 120 may determine the time difference between the first time information and the second time information as the first TOF difference.

[0071] In some embodiments, the processing device 120 can correct the first TOF difference based on one or more correction algorithms. For example, the processing device 120 can perform time walk effect correction on the first TOF difference. In a PET device, a time readout circuit can be used to obtain the arrival time of the rising edge of an input signal. The time readout circuit can amplify the input signal, and the arrival time of the signal's rising edge is discriminated by a rising edge discriminator (LED), thereby determining the time information of the signal. However, the amplification of the input signal difference can be different. A rising edge of a signal with a relatively small amplitude may arrive at the rising edge discriminator later than a rising edge of a signal with a relatively large amplitude, generating a time walk effect that may result in inaccurate timing of the time readout circuit. Therefore, time walk effect correction can be performed on the first TOF difference to reduce the time walk effect. As another example, the processing device 120 can perform position correction on the first TOF difference. The position correction can be used to correct for differences in the time walk effect due to different locations of the detectors in the PET device. Thus, by correcting the first TOF difference based on one or more correction algorithms, the accuracy of the first TOF difference may be improved.

[0072] At 530, the processing device 120 (e.g., the determination module 420) can determine a second TOF difference corresponding to each coincidence event based on the locations of the two crystals that detect each coincidence event.

[0073] In some embodiments, the second TOF difference can be the actual time difference between two detection times of two particles generated in a coincidence event, for example, the second TOF difference can be the time it takes for a gamma particle to escape from a first crystal to a second crystal.

[0074] In some embodiments, processing device 120 can determine the second TOF difference based on the distance between the location of the first crystal and the location of the second crystal and the speed of the gamma particle (i.e., the speed of light). For example, processing device 120 can determine the second TOF difference by dividing the distance between the location of the first crystal and the location of the second crystal by the speed of light.

[0075] At 540, the processing device 120 (eg, the correction module 430) may correct the PET device (eg, the TOF state of the PET device) based on the first TOF difference and the second TOF difference.

[0076] As used herein, the TOF status of a PET device refers to the TOF information of coincidence events detected by one or more crystals of the PET device. In some embodiments, the processing device 120 can determine whether the TOF status of each of the multiple crystals of the PET device needs to be corrected based on a first TOF difference and a second TOF difference corresponding to at least one coincidence event detected between each crystal and another crystal. In some embodiments, if at least one component of the PET device (e.g., a photoelectric conversion device, a back-end circuit) is malfunctioning, the first time information and the second time information may be inaccurate, and the first TOF difference determined based on the first time information and the second time information may also be inaccurate. That is, the first TOF difference measured by the PET device may differ from the second TOF difference.

[0077] In some embodiments, for a particular crystal among the multiple crystals of the PET device, processing device 120 can determine a TOF correction value for the particular crystal. For example, processing device 120 can determine a difference value (i.e., a TOF correction value) between a first TOF difference and a second TOF difference corresponding to a coincidence event detected between the particular crystal and another crystal. Processing device 120 can determine whether the difference value is less than a first difference threshold. In response to determining that the difference value is less than the first difference threshold, processing device 120 can determine that the TOF status of the particular crystal does not need to be corrected. In response to determining that the difference value is not less than the first difference threshold, processing device 120 can determine that the TOF status of the particular crystal needs to be corrected.

[0078] In some embodiments, for a particular crystal of the multiple crystals in the PET device, processing device 120 determines multiple pairs of first and second TOF differences corresponding to each of multiple coincidence events detected between the particular crystal and other crystals. Processing device 120 can determine a difference value between the first and second TOF differences for each of the multiple pairs of first and second TOF differences. Processing device 120 can determine an average value (i.e., a TOF correction value) of the multiple difference values ​​corresponding to the multiple pairs of first and second TOF differences. Processing device 120 can determine whether the difference value is less than a second difference threshold. In response to determining that the average value is less than the second difference threshold, processing device 120 can determine that the TOF status of the particular crystal does not need to be corrected. In response to determining that the average value is not less than the second difference threshold, processing device 120 can determine that the TOF status of the particular crystal needs to be corrected.

[0079] In some embodiments, for a particular crystal of the multiple crystals of the PET device, processing device 120 can generate a time spectrum based on a first TOF difference and a second TOF difference corresponding to each of one or more of the coincidence events detected between the particular crystal and the other crystals. Processing device 120 can determine a TOF correction value based on the time spectrum. For example, processing device 120 can determine a TOF correction value based on the time spectrum through a repetitive operation including one or more repetitions. Further description of determining a TOF correction value based on a time spectrum can be found elsewhere in this disclosure (e.g., FIG. 6 and its description).

[0080] The processing device 120 can correct the TOF state of the PET device based on the TOF correction value corresponding to each of the multiple crystals of the PET device. In some embodiments, the processing device 120 can record one or more TOF correction values ​​corresponding to one or more of the multiple crystals of the PET device in a correction file of the PET device (also referred to as an offline correction mode). During a scan of a subject (e.g., a patient), the processing device 120 can correct TOF information of one or more coincidence events detected by one or more crystals based on the one or more TOF correction values ​​corresponding to the one or more crystals in the correction file of the PET device. If the TOF correction value corresponding to a particular crystal is +50 time units, the target detection time of a particle generated in a coincidence event detected by the particular crystal can be determined by subtracting 50 time units from the original detection time of the particle. Therefore, by recording the TOF correction value in the correction file of the PET device, the TOF state of the PET device can be corrected offline, which can simplify the correction process, shorten the correction time, and improve the efficiency of the correction process.

[0081] In some embodiments, processing device 120 can program one or more TOF correction values ​​corresponding to one or more crystals of the PET device in one or more detectors of the PET device (also referred to as an online correction mode). For example, processing device 120 can program one or more TOF correction values ​​into the front-end circuits of one or more detectors of the PET device. Thus, by programming one or more TOF correction values ​​into the front-end circuits of one or more detectors of the PET device, the TOF status of the PET device can be corrected online, and the correction effect can be improved.

[0082] In some embodiments, the correction mode (e.g., offline correction mode, online correction mode) can be determined based on actual needs and / or the TOF correction value. For example, if the absolute value of the TOF correction value is relatively large (e.g., greater than a threshold), the TOF status of the PET device can be corrected according to the online correction mode. If the absolute value of the TOF correction value is relatively small (e.g., smaller than a threshold), the TOF status of the PET device can be corrected according to the offline correction mode.

[0083] In some embodiments, deviations in the TOF status of the PET device may be caused by the malfunction of any component of the PET device. The location of the malfunctioning component cannot be determined solely based on the TOF correction value, and therefore the TOF status of the PET device cannot be corrected by repairing the malfunctioning component. Therefore, by recording the TOF correction value in a correction file of the PET device or programming the TOF correction value into one or more detectors of the PET device, the TOF status of the PET device can be corrected without determining the reason for the malfunction of the PET device and repairing the malfunctioning component of the PET device, which may improve the accuracy and efficiency of the correction process.

[0084] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of the present disclosure. Those skilled in the art can make numerous modifications and improvements under the teachings of the present disclosure. However, these modifications and improvements do not depart from the scope of the present disclosure. In some embodiments, process 500 may include an operation for modifying the energy state of the PET device based on data associated with coincidence events. Further description of modifying the energy state of the PET device can be found elsewhere in this disclosure (e.g., FIG. 7 and its description). In some embodiments, during the PET device modification process, a subject positioned in the FOV of the PET device may be positioned in the FOV of the PET device to prevent the subject from absorbing gamma rays emitted from the intrinsic background radiation of the multiple crystals of the PET device.

[0085] FIG. 6 is a flow chart illustrating an example process for determining a TOF correction value according to some embodiments of the present disclosure. In some embodiments, process 600 may be implemented in medical system 100 shown in FIG. 1. For example, process 600 may be stored in the form of instructions in storage device 130 and / or a storage device (e.g., storage device 220, storage device 390) and may be recalled and / or executed by processing device 120 (e.g., processing unit 210 of computing device 200 as shown in FIG. 2, CPU 340 of mobile device 300 as shown in FIG. 3). The illustrated process operations are intended to be illustrative. In some embodiments, process 600 may be performed with one or more additional operations not described and / or without one or more of the discussed operations. Additionally, the order of operations of process 600 as shown in FIG. 6 and described below is not intended to be limiting.

[0086] At 610, for each crystal of the plurality of crystals of the PET device, the processing device 120 (eg, the determination module 420) can generate a time spectrum of the crystal.

[0087] In some embodiments, for a first iteration in the iterative operation, processing device 120 can generate a time spectrum based on a first TOF difference and a second TOF difference corresponding to one or more of the coincidence events detected between the crystal and the other crystals of the PET device. In some embodiments, the time spectrum can satisfy a Gaussian distribution. For example, for each of one or more (e.g., all) coincidence events detected between the crystal and the other crystals, processing device 120 can determine the time difference between the first TOF difference and the second TOF difference corresponding to the coincidence event. Processing device 120 can generate a time spectrum of the crystal based on one or more time differences corresponding to one or more coincidence events detected between the crystal and the other crystals.

[0088] In some embodiments, the time spectrum of a particular crystal can reflect the count of coincidence events and the time difference between the first TOF difference and the second TOF difference corresponding to each of multiple coincidence events detected between the particular crystal and other crystals. For example, the horizontal axis of the time spectrum can refer to Tbin. Tbin can be determined based on the time difference between the first TOF difference and the second TOF difference corresponding to the coincidence events and the time unit. For example, Tbin can be determined by dividing the time difference by the time unit. The time unit can be manually set by a user of the medical system 100 or can be determined by one or more components of the medical system 100 (e.g., the processing device 120). For example, the time unit can be 10, 20, 30, etc. The vertical axis of the time spectrum can refer to the count of coincidence events. In some embodiments, it is assumed that the TOF status of the other crystals is normal, and the processing device 120 can generate the time spectrum of the particular crystal by accumulating multiple time differences corresponding to multiple coincidence events detected between the particular crystal and other crystals. For example, for each of multiple coincidence events detected between a particular crystal and other crystals, processing device 120 can determine the time difference between the first TOF difference and the second TOF difference corresponding to the coincidence event, determine which T bin the time difference belongs to, and add 1 to the cumulative count of the coincidence event corresponding to T bin.

[0089] At 620, the processing device 120 (eg, the determination module 420) may determine an offset value for the crystal based on the time spectrum.

[0090] In some embodiments, processing device 120 can determine an offset value for a crystal based on an expected value of a time spectrum with a Gaussian distribution. For example, processing device 120 can determine the expected value of a time spectrum with a Gaussian distribution as the offset value for the crystal in the current iteration. In some embodiments, if the TOF state of the crystal (also referred to in this disclosure as the TOF information of the crystal) is normal, the expected value of the time spectrum with a Gaussian distribution for the crystal can be zero, and the offset value can also be zero. If the TOF state of the crystal is abnormal, the expected value of the time spectrum with a Gaussian distribution can be less than or greater than zero, and the offset value can be the expected value. As used herein, the TOF state of the crystal refers to the TOF information of coincidence events detected by the crystal.

[0091] At 630, the processing device 120 (eg, the determination module 420) may determine whether the repeat operation satisfies the condition based on the offset value.

[0092] In some embodiments, processing device 120 can determine whether the repeat operation satisfies a condition based on offset values ​​for multiple crystals of the PET device. For example, the condition can be met if the offset value for each crystal of the multiple crystals is less than a threshold. As another example, the termination condition can be met if the change in the offset value for each crystal of the multiple crystals over two or more consecutive repeats is less than a threshold.

[0093] At 640, in response to determining that the repeat operation does not satisfy the condition, the processing device 120 (eg, the decision module 420) may adjust the TOF state of the crystal based on an offset value for the crystal.

[0094] In some embodiments, for each crystal of the multiple crystals in the PET device, processing device 120 can adjust the TOF state of the crystal based on an offset value for the crystal so that the time spectrum of the adjusted crystal does not shift. As used herein, an adjusted crystal refers to a crystal whose TOF state is adjusted based on an offset value for the crystal. That is, the offset value of the time spectrum of the adjusted crystal may be zero.

[0095] In some embodiments, processing device 120 can adjust the TOF state of the crystal by adjusting data associated with the coincidence events detected by the crystal. For example, processing device 120 can adjust the time information (e.g., first time information, second time information) of the coincidence events detected by the crystal. Simply by example, if the offset value for the crystal in the current iteration is +50 time units, the target detection time of a particle generated in the coincidence events detected by the crystal can be determined by subtracting 50 time units from the original detection time of the particle. The first TOF difference can be adjusted based on the corrected first time information and / or the corrected second time information.

[0096] FIG. 9 shows an example time spectrum of a crystal, according to some embodiments of the present disclosure. The horizontal axis of the time spectrum may refer to Tbin. The vertical axis of the time spectrum may refer to the count of radiation events (e.g., coincidence events). As shown in FIG. 9, the time spectrum 910 of the crystal satisfies a Gaussian distribution. The expected value of the time spectrum 910 is +50 time units. An offset value for the crystal may be determined as +50 time units. After the TOF state of the crystal is corrected, the time spectrum 920 of the crystal is generated. The expected value of the time spectrum 920 is 0 time units.

[0097] In some embodiments, operations 610-630 may be repeated until the repeat operation satisfies a condition. For example, in the next iteration, for each crystal of the multiple crystals of the PET device, processing device 120 may generate a time spectrum of the crystal based on adjusted data (e.g., adjusted first time information, adjusted second time information) associated with coincidence events detected between the crystal and other crystals, as described in connection with operation 610. Processing device 120 may determine an offset value for the crystal based on the time spectrum, as described in connection with operation 620. Processing device 120 may determine whether the repeat operation satisfies a condition based on the offset value for the crystal, as described in connection with operation 630.

[0098] In some embodiments, the same set of data associated with coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device may be used in each of one or more iterations of the repeating operation. In some embodiments, different sets of data associated with coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device may be used in different iterations of the repeating operation. For example, in a first iteration of the repeating operation, processing device 120 may obtain a first set of data associated with coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device. In a second iteration of the repeating operation, processing device 120 may obtain a second set of data associated with coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device. The first set of data and the second set of data may be associated with different coincidence events related to the intrinsic background radiation of the multiple crystals of the PET device.

[0099] At 650, in response to determining that the iterative operation satisfies the condition, the processing device 120 (e.g., the determination module 420) may determine a TOF correction value for the crystal by summing one or more offset values ​​for the crystal in one or more iterations.

[0100] In some embodiments, processing device 120 can determine a TOF correction value for a particular crystal by summing one or more offset values ​​for the particular crystal over one or more iterations. For example, processing device 120 can determine the sum of one or more offset values ​​for the particular crystal over one or more iterations as the TOF correction value for the particular crystal. As another example, processing device 120 can determine the additive inverse of the sum of one or more offset values ​​for the particular crystal over one or more iterations as the TOF correction value for the particular crystal. Furthermore, processing device 120 can correct the TOF state of the PET device based on the TOF correction values ​​for each of the multiple crystals of the PET device, as described in connection with operation 540.

[0101] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of the present disclosure. For those skilled in the art, multiple modifications and improvements can be made under the teachings of the present disclosure. However, these modifications and improvements do not depart from the scope of the present disclosure.

[0102] FIG. 7 is a flow chart illustrating an example process for modifying the energy state of a PET device, according to some embodiments of the present disclosure. In some embodiments, process 700 may be implemented in medical system 100 shown in FIG. 1. For example, process 700 may be stored in the form of instructions in storage device 130 and / or a storage device (e.g., storage device 220, storage device 390) and may be recalled and / or executed by processing device 120 (e.g., processing unit 210 of computing device 200 as shown in FIG. 2, CPU 340 of mobile device 300 as shown in FIG. 3). The illustrated process operations are intended to be illustrative. In some embodiments, process 700 may be performed with one or more additional operations not described and / or without one or more of the discussed operations. Additionally, the order of operations of process 700 as shown in FIG. 7 and described below is not intended to be limiting.

[0103] At 710, the processing device 120 (eg, acquisition module 410) can acquire data associated with single events or coincident events related to the intrinsic background radiation of the crystals of the PET device.

[0104] Operation 710 may be performed in a manner similar to operation 510 as described in connection with FIG. 5, and that description will not be repeated here.

[0105] At 720, the processing device 120 (eg, the determination module 420) may generate a reference energy spectrum based on the energy information of the single event or the coincident events.

[0106] In some embodiments, the processing device 120 can generate a reference energy spectrum based on energy information of a single event. In some embodiments, the processing device 120 can generate a reference energy spectrum based on time and energy information of coincident events. For example, the coincident events may include a β event and a γ event. The processing device 120 can generate a reference energy spectrum corresponding to the β event and / or a reference energy spectrum corresponding to the γ event based on time information of the β event and time information of the γ event. For example, the detection time of the γ event may be later than the detection time of the β event. The processing device 120 can obtain energy information of the β event and / or energy information of the γ event based on the detection time of the γ event and the detection time of the β event. The processing device 120 can generate a reference energy spectrum corresponding to the β event and / or a reference energy spectrum corresponding to the γ event based on the energy information of the β event and the energy information of the γ event.

[0107] In some embodiments, the intrinsic background radiation generated from the Lu-based crystal can produce three types of gamma particles with energy peaks of 307 keV, 202 keV, and 88 keV upon decay. The gamma particles can strike the crystal of the PET device to generate an optical signal. The optical signal can be converted into an electrical signal by a photoelectric conversion device (e.g., a PMT) coupled to the crystal. The electrical signal can include information about the energy peaks of the gamma particles (i.e., energy information of the gamma events). The processing device 120 can process the electrical signal to generate a reference energy spectrum corresponding to the gamma events. In some embodiments, the reference energy spectrum can have one or more peaks, each corresponding to an energy. For example, the reference energy spectrum corresponding to a gamma event can have a peak corresponding to 307 keV, a peak corresponding to 202 keV, and a peak corresponding to 88 keV.

[0108] At 730, the processing device 120 (eg, the determining module 420) may determine a reference peak position in the reference energy spectrum.

[0109] In some embodiments, the processing device 120 can identify one or more positions of one or more reference peaks (also referred to as one or more reference peak positions) in the reference energy spectrum. FIG. 10 shows an example reference energy spectrum according to some embodiments of the present disclosure. The radiation source is intrinsic background radiation generated by a Lu-based crystal. The horizontal axis of the reference energy spectrum 1000 can refer to analog-to-digital converter (ADC) channel values. The vertical axis of the reference energy spectrum 1000 can refer to PET counts (e.g., radiation event counts). The ADC channel values ​​can be ADC sampled values. The ADC channel values ​​can reflect energy information of the radiation events. As shown in FIG. 10 , a reference peak position 1001 corresponding to 202 keV and a reference peak position 1002 corresponding to 307 keV are determined in the reference energy spectrum 1000.

[0110] At 740, the processing device 120 (eg, the determination module 420) may determine a target peak position based on the reference peak position in the reference energy spectrum.

[0111] In some embodiments, the target peak position can be a measured peak position corresponding to a target energy in a reference energy spectrum. In some embodiments, the reference energy can be a measured peak position corresponding to a target energy in a reference energy spectrum. 18 For example, the target energy may be 511 keV.

[0112] In some embodiments, the processing device 120 can determine the target peak position based on the reference peak position and the relationship between the position of the peak (e.g., ADC channel value) and the energy of the peak. For example, if a reference peak position corresponding to 307 keV (or 88 keV, 202 keV) is determined in the reference energy spectrum, the processing device 120 can determine the target peak position corresponding to 511 keV based on the relationship between the peak position corresponding to 307 keV (or 88 keV, 202 keV) and the peak position corresponding to 511 keV.

[0113] In some embodiments, the relationship between the peak position and the peak energy can be expressed in the form of a table, curve, diagram, mathematical formula, etc., for different energies of the peak and their corresponding peak positions. In some embodiments, the relationship between the peak position and the peak energy can be determined based on multiple peak positions corresponding to particles of different energies generated by multiple radioactive sources (e.g., technetium-99 (Tc-99), fluorine-18 (F-18), indium-111 (In-111), iodine-131 (I-131)). In some embodiments, the processing device 120 can obtain a first peak position (also referred to as a first peak position corresponding to a first energy) corresponding to a first particle with a first energy generated by a first radioactive source, a second peak position corresponding to a second particle with a second energy generated by a second radioactive source, and a third peak position corresponding to a third particle with a third energy generated by a third radioactive source. The first energy, the second energy, and the third energy may be different. The first radioactive source, the second radioactive source, and the third radioactive source may be the same or different. The processing device 120 can determine a relationship between the peak positions and the peak energies based on the first peak positions, the second peak positions, the third peak positions, the first energy, the second energy, and the third energy. For example, the processing device 120 can generate a curve by fitting the first peak position corresponding to the first energy, the second peak position corresponding to the second energy, and the third peak position corresponding to the third energy. The processing device 120 can specify the curve as the relationship between the peak positions and the peak energies.

[0114] In some embodiments, the relationship between the peak position and the peak energy may be stored in a storage device (e.g., storage device 130) of the medical system 100. When the processing device 120 modifies the energy state of the PET device, the relationship between the peak position and the peak energy may be retrieved from a storage device (e.g., storage device 130) of the medical system 100. In some embodiments, different crystals may correspond to different relationships between the peak position and the peak energy. In some embodiments, different crystals may correspond to the same relationship between the peak position and the peak energy.

[0115] At 750, the processing device 120 (eg, the determination module 420) may determine an energy modification state based on the target peak position and the modified peak position.

[0116] In some embodiments, the energy correction state of the PET device can indicate whether the peak position corresponding to the energy in the energy spectrum is misaligned. In some embodiments, the corrected peak position can be the actual peak position corresponding to the target energy (e.g., 511 keV) in the target energy spectrum. In some embodiments, the processing device 120 18 Data associated with single events or coincidence events associated with 511 keV gamma photons generated from a radioactive source such as F-fluorodeoxyglucose (FDG) or germanium-68 (Ge-68) can be acquired. The processing device 120 can generate a reference energy spectrum based on energy information of the single events or coincidence events corresponding to the 511 keV gamma photons. The processing device 120 can determine corrected peak positions in the reference energy spectrum.

[0117] In some embodiments, the processing device 120 can determine the energy correction state by comparing the target peak position and the corrected peak position. For example, the processing device 120 can determine whether the offset between the target peak position and the corrected peak position is greater than an offset threshold. In response to determining that the offset between the target peak position and the corrected peak position is greater than the offset threshold, the processing device 120 can determine that the energy correction state is abnormal, and the energy state of the PET device needs to be corrected. As another example, the processing device 120 can determine whether the ratio between the target peak position and the corrected peak position is greater than a ratio threshold. In response to determining that the ratio between the target peak position and the corrected peak position is greater than the ratio threshold, the processing device 120 can determine that the energy correction state is abnormal, and the energy state of the PET device needs to be corrected. In some embodiments, the offset threshold and / or the ratio threshold can be determined manually by a user (e.g., a doctor) of the medical system 100 or by one or more components (e.g., the processing device 120) of the medical system 100 depending on different circumstances.

[0118] At 760, the processing device 120 (eg, the modification module 430) may modify the PET device (eg, the energy state of the PET device) based on the energy modification state.

[0119] In some embodiments, processing device 120 can determine whether the energy state of the PET device needs to be modified based on the energy modification state. In response to determining that the energy state of the PET device needs to be modified, processing device 120 can program a target peak position into one or more detectors of the PET device. For example, processing device 120 can program the target peak position into front-end circuits of one or more detectors of the PET device.

[0120] In some embodiments, the processing device 120 can modify the relationship between the peak position and the peak energy based on the energy modification state. For example, the processing device 120 can modify the peak position (e.g., the ADC channel value) of the 511 keV gamma photon based on the energy modification state. For example, the processing device 120 can designate the peak position of the 511 keV gamma photon as the target peak position.

[0121] In some embodiments, the processing device 120 can determine the energy window of the PET detector based on the energy modification state. As used herein, the energy window of the PET detector refers to the energy range of particles detected by the PET detector. In some embodiments, the energy window of the PET detector can be determined based on the energy corresponding to one or more peaks in the energy spectrum of the radiotracer. For example, the energy window can include energies within an energy threshold range around the energy of the peak. For example, if the energy corresponding to the peak is 511 keV and the energy threshold range is 100 keV, the energy window can be determined as [411 keV, 611 keV]. In some embodiments, if the measured energy corresponding to a gamma photon is shifted from 511 keV to 400 keV, the energy window can be changed from [411 keV, 611 keV] to [300 keV, 500 keV]. Therefore, by changing the energy window based on the energy modification state, the accuracy of PET data acquisition (e.g., data associated with coincidence events) can be improved.

[0122] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of the present disclosure. Those skilled in the art may make numerous modifications and improvements under the teachings of the present disclosure. However, these modifications and improvements do not depart from the scope of the present disclosure. In some embodiments, for each crystal of a plurality of crystals in a PET device, process 700 may be performed to determine an energy correction state for the crystal. The energy state of the PET device may be modified based on the energy correction states for the plurality of crystals in the PET device.

[0123] In some embodiments, after the energy state of the PET device is corrected, the processing device 120 can acquire target data associated with a single event or a coincidence event related to the intrinsic background radiation of the PET device crystal (e.g., a Lu-based crystal). The processing device 120 can generate a candidate energy spectrum based on the energy information of the single event or the coincidence event. The processing device 120 can determine a candidate peak position in the candidate energy spectrum. During the PET device energy state correction process (e.g., process 700), the processing device 120 can determine the energy correction state based on the candidate peak position and a reference peak position. In some embodiments, the processing device 120 can determine the energy correction state by comparing the candidate peak position with the reference peak position. For example, the processing device 120 can determine whether the offset between the candidate peak position and the reference peak position is greater than an offset threshold. In response to determining that the offset between the candidate peak position and the reference peak position is greater than the offset threshold, the processing device 120 can determine that the energy correction state is abnormal, and the energy state of the PET device crystal needs to be corrected.

[0124] In some embodiments, the processing device 120 can determine an energy modification state based on multiple candidate peak positions and multiple reference peak positions. For example, the processing device 120 can determine, in the candidate energy spectrum, a first candidate peak position corresponding to 202 keV and a second candidate peak position corresponding to 307 keV. The processing device 120 can determine, in the reference energy spectrum, a first reference peak position corresponding to 202 keV and a second reference peak position corresponding to a 307 keV particle. The processing device 120 can determine a first distance between the first reference peak position and the second reference peak position. The processing device 120 can determine a second distance between the first candidate peak position and the second candidate peak position. The processing device 120 can determine whether a difference between the first distance and the second distance is greater than a distance threshold. In response to determining that the difference between the first distance and the second distance is greater than the distance threshold, the processing device 120 can determine that the energy modification state is abnormal and that the energy state of the crystal of the PET device needs to be modified.

[0125] It should be noted that the above description is provided for illustrative purposes only and is not intended to limit the scope of the present disclosure. For those skilled in the art, multiple modifications and improvements can be made under the teachings of the present disclosure. However, these modifications and improvements do not depart from the scope of the present disclosure.

[0126] Having described the basic concepts, it may be rather apparent to those skilled in the art after reading the foregoing detailed description that the detailed description is intended to be presented by way of example only and not by way of limitation. Although not expressly stated herein, various substitutions, modifications, and variations may be made and are contemplated by those skilled in the art. These substitutions, modifications, and variations are intended to be suggested by this disclosure and are within the spirit and scope of the exemplary embodiments of the disclosure. [Explanation of symbols]

[0127] 100 Healthcare Systems 110 Medical Devices 111 Gantry 112 PET detector 113 Detection Area 114 Tables 120 Processing Device 130 Storage Devices 140 terminals 141 Mobile Devices 142 tablet computers 143 laptop computers 150 Network 200 Computer Devices 210 Processing equipment 220 Storage device 230 Input / Output (I / O) 240 communication port 300 mobile devices 310 Communication Platform 320 display device 330 Graphics Processing Unit, GPU 340 Central Processing Unit, CPU 350 I / O 360 memory 370 Mobile Operating System, OS 380 Applications 390 Storage device 410 Acquisition Module 420 Decision Module 430 Correction Module 810 First Crystal 820 Second Crystal 830 β particle 840 gamma particle 850 First photoelectric conversion device 860 Second Photoelectric Conversion Device 910 Time Spectrum 1000 Reference Energy Spectra 1001 Reference peak position corresponding to 202 keV 1002 Reference peak position corresponding to 307 keV

Claims

1. 1. A method for modifying a positron emission tomography (PET) device implemented on a computing device comprising at least one processing unit and at least one storage device, the method comprising: acquiring data associated with coincidence events related to intrinsic background radiation of a plurality of crystals of the PET device, each of the coincidence events being detected by two of the plurality of crystals of the PET device, and the data associated with each of the coincidence events including first time information and second time information; determining a first time-of-flight (TOF) difference corresponding to each of the coincident events based on the first time information and the second time information; determining a second TOF difference corresponding to each of the coincidence events based on the locations of the two crystals detecting each of the coincidence events; For each crystal of the plurality of crystals of the PET device: generating a time spectrum based on the first TOF difference and the second TOF difference corresponding to each of one or more of the coincidence events detected between the crystal and another crystal; determining a TOF correction value based on the time spectrum through an iterative operation including one or more iterations, wherein in at least one of the one or more iterations, determining the TOF correction value comprises: For each crystal of the plurality of crystals of the PET device: generating a time spectrum of the crystal; determining an offset value for the crystal based on the time spectrum; determining whether the repeat operation satisfies a condition based on the offset value for the crystal; adjusting the TOF information of the crystal based on the offset value for the crystal in response to determining that the iterative operation does not satisfy the condition; responsive to determining that the iteration satisfies the condition, determining the TOF correction value for the crystal by summing one or more offset values ​​for the crystal in the one or more iterations; determining a TOF correction value, correcting the PET device based on the TOF correction value corresponding to each crystal of the plurality of crystals of the PET device; A method comprising:

2. each of the coincident events includes a β event and a γ event, the first time information corresponds to the β event, and the second time information corresponds to the γ event; detecting β particles with a first of the two crystals and detecting γ particles with a second of the two crystals, and determining a second TOF difference corresponding to each of the coincidence events based on the locations of the two crystals, The method of claim 1 , comprising determining the second TOF difference based on a distance between the location of the first crystal and the location of the second crystal.

3. The method of claim 1 , wherein the condition is met if the offset value of the crystal for each of the plurality of crystals is less than a threshold value.

4. The method of claim 1 , wherein the condition is met when a change in the offset value of each of the plurality of crystals in two or more consecutive iterations is less than a threshold value.

5. The step of correcting the PET device based on the TOF correction value corresponding to each crystal of the plurality of crystals of the PET device comprises: recording the TOF correction value in a correction file of the PET device; or programming the TOF correction values ​​into one or more detectors of the PET device. The method of claim 1 , comprising:

6. The method of claim 1 , further comprising performing a time walk effect correction and / or a position correction on the first TOF difference.

7. The method of claim 1 , further comprising modifying the PET device based on energy information of the data associated with the coincident events.

8. modifying the PET device based on energy information of the data associated with the coincidence events, generating a reference energy spectrum based on the energy information of each of the coincidence events; determining a reference peak position in the reference energy spectrum; determining a target peak position based on the reference peak position in the reference energy spectrum; modifying the PET device based on the target peak location and the modified peak location; The method of claim 7, comprising:

9. the reference energy spectrum includes a reference energy spectrum corresponding to a gamma event, the reference energy spectrum corresponding to the gamma event having a peak corresponding to 307 keV, a peak corresponding to 202 keV, and a peak corresponding to 88 keV; and 9. The method of claim 8, wherein the target peak position corresponds to 511 keV and is determined based on a relationship between any of peak positions corresponding to 307 keV, 88 keV, and 202 keV and the peak position corresponding to 511 keV.

10. The step of modifying the PET device based on the target peak location and the modified peak location comprises: determining whether the PET device needs to be modified based on the target peak location and the corrected peak location; In response to determining that the PET device needs to be modified, programming the target peak location into one or more detectors of the PET device; The method of claim 8, comprising:

11. determining a target peak position based on the reference peak position in the reference energy spectrum, The method of claim 8 , comprising determining the target peak position based on the base peak position and a relationship between the position of a peak and the energy of the peak.

12. If the absolute value of the TOF correction value is greater than a threshold, correcting the TOF state of the PET device according to an online correction mode; The method of claim 1 , further comprising correcting the TOF state of the PET device according to an offline correction mode if the absolute value of the TOF correction value is less than a threshold value.

13. 1. A system for modifying a positron emission tomography (PET) device, comprising: at least one storage device containing a set of instructions; at least one processing device configured to communicate with the at least one storage device, wherein when executing the set of instructions, the at least one processing device provides the system with: acquiring data associated with coincidence events related to intrinsic background radiation of a plurality of crystals of the PET device, each of the coincidence events being detected by two of the plurality of crystals of the PET device, and the data associated with each of the coincidence events including first time information and second time information; determining a first time-of-flight (TOF) difference corresponding to each of the coincident events based on the first time information and the second time information; determining a second TOF difference corresponding to each of the coincidence events based on the locations of the two crystals detecting each of the coincidence events; For each crystal of the plurality of crystals of the PET device: generating a time spectrum based on the first TOF difference and the second TOF difference corresponding to each of one or more of the coincidence events detected between the crystal and another crystal; determining a TOF correction value based on the time spectrum through an iterative operation including one or more iterations, wherein in at least one of the one or more iterations, determining the TOF correction value includes: For each crystal of the plurality of crystals of the PET device: generating a time spectrum of said crystal; determining an offset value for the crystal based on the time spectrum; determining whether the repeating operation satisfies a condition based on the offset value for the crystal; adjusting the TOF information of the crystal based on the offset value for the crystal in response to determining that the repeating operation does not satisfy the condition; responsive to determining that the iteration satisfies the condition, determining the TOF correction value for the crystal by summing one or more offset values ​​for the crystal in the one or more iterations; determining a TOF correction value, correcting the PET device based on the TOF correction value corresponding to each crystal of the plurality of crystals of the PET device; at least one processing unit configured to instruct the processor to perform operations including: A system comprising:

14. 1. A non-transitory computer-readable medium comprising executable instructions that, when executed by at least one processing device, direct the at least one processing device to perform a method for modifying a positron emission tomography (PET) device, the method comprising: acquiring data associated with coincidence events related to intrinsic background radiation of a plurality of crystals of the PET device, each of the coincidence events being detected by two of the plurality of crystals of the PET device, and the data associated with each of the coincidence events including first time information and second time information; determining a first time-of-flight (TOF) difference corresponding to each of the coincident events based on the first time information and the second time information; determining a second TOF difference corresponding to each of the coincidence events based on the locations of the two crystals detecting each of the coincidence events; For each crystal of the plurality of crystals of the PET device: generating a time spectrum based on the first TOF difference and the second TOF difference corresponding to each of one or more of the coincidence events detected between the crystal and another crystal; determining a TOF correction value based on the time spectrum through an iterative operation including one or more iterations, wherein in at least one of the one or more iterations, determining the TOF correction value comprises: For each crystal of the plurality of crystals of the PET device: generating a time spectrum of the crystal; determining an offset value for the crystal based on the time spectrum; determining whether the repeat operation satisfies a condition based on the offset value for the crystal; adjusting the TOF information of the crystal based on the offset value for the crystal in response to determining that the iterative operation does not satisfy the condition; responsive to determining that the iteration satisfies the condition, determining the TOF correction value for the crystal by summing one or more offset values ​​for the crystal in the one or more iterations; determining a TOF correction value, correcting the PET device based on the TOF correction value corresponding to each crystal of the plurality of crystals of the PET device; 1. A non-transitory computer-readable medium, comprising:

Images