Patent Description:
Generally, positron emission tomography (PET) detector units have been set in various medical devices such as, positron emission tomography devices, positron emission tomography-computed tomography (PET-CT) devices, and positron emission tomography-magnetic resonance imaging devices (PET-MRI), in which PET technologies are applied. PET detector units are used to receive radiation rays (e.g., γ rays) generated from a patient's body indirectly by tracer molecules and to provide information relating to the locations of the tracer molecules, which in turn provides functional information of the patient. PET detector units may generate electrical signals based on the radiation rays, and then the electrical signals may be detected and used to reconstruct an image.

A PET detector assembly of a PET imaging system may include a plurality of detector units arranged in a substantially cylindrical configuration. Generally speaking, the more detector units the PET detector assembly includes, the more radiation rays the PET detector assembly may receive, and the higher the sensitivity of a PET imaging system may be. In some embodiments, it may be desirable to perform a whole-body scanning using a PET imaging system. A large axial field-of-view (AFOV) detector assembly may image a large fraction of an object (e.g., the whole body of a patient) in one scan, the sensitivity may be increased, and the scanning time may be shortened. Besides, a large AFOV may facilitate a whole-body dynamic scan that may have the benefits of a low radiation dose, a fast speed, etc. It may be desirable to develop a PET imaging system having a detector assembly with a large AFOV.

<CIT> relates to radiation tomography apparatus that images radiation emitted from a subject. <NPL> relates to tomograph simulation of a cylindrical phantom. <CIT> relates to nuclear medicine imaging system and in particular to the electronics and detectors of apparatus detecting photons in emission and transmission mode. <CIT> relates to an apparatus for providing geometrically configurable mechanical support for PET detector arrays.

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should 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 circuitry have been described at a relatively high-level, without detail, in order 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. Thus, the present disclosure is not limited to the embodiments shown, but to be accorded the widest scope consistent with the claims.

It will be understood that the term "system," "engine," "unit," "module," and/or "block" used herein are one method to distinguish different components, elements, parts, section or assembly of different level in ascending order. However, the terms may be displaced by other expression if they achieve the same purpose.

Generally, the word "module," "unit," or "block," as used herein, refers to logic embodied in hardware or firmware, or to a collection of software instructions. A module, a unit, or a block described herein may be implemented as software and/or hardware and may be stored in any type of non-transitory computer-readable medium or other storage device. In some embodiments, a software module/unit/block may be compiled and linked into an executable program. It will be appreciated that software modules can be callable from other modules/units/blocks or from themselves, and/or may be invoked in response to detected events or interrupts. Software modules/units/blocks configured for execution on computing devices may be provided on a computer-readable medium, such as a compact disc, a digital video disc, a flash drive, a magnetic disc, or any other tangible medium, or as a digital download (and can be originally stored in a compressed or installable format that needs installation, decompression, or decryption prior to execution). Such software code may be stored, partially or fully, on a storage device of the executing computing device, for execution by the computing device. Software instructions may be embedded in a firmware, such as an EPROM. It will be further appreciated that hardware modules/units/blocks may be included in connected logic components, such as gates and flip-flops, and/or can be included of programmable units, such as programmable gate arrays or processors. The modules/units/blocks or computing device functionality described herein may be implemented as software modules/units/blocks, but may be represented in hardware or firmware. In general, the modules/units/blocks described herein refer to logical modules/units/blocks that may be combined with other modules/units/blocks or divided into sub-modules/sub-units/sub-blocks despite their physical organization or storage. The description may be applicable to a system, an engine, or a portion thereof.

It will be understood that when a unit, engine, module or block is referred to as being "on," "connected to," or "coupled to," another unit, engine, module, or block, it may be directly on, connected or coupled to, or communicate with the other unit, engine, module, or block, or an intervening unit, engine, module, or block may be present, unless the context clearly indicates otherwise.

For illustration purposes, the following description is provided to help better understanding a PET imaging system. It is understood that this is not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, a certain amount of variations, changes and/or modifications may be deducted under guidance of the present disclosure. Those variations, changes and/or modifications do not depart from the scope of the present disclosure.

<FIG> is a schematic diagram illustrating an exemplary imaging system <NUM> according to some embodiments of the present disclosure. As shown, the imaging system <NUM> includes a scanner <NUM>, a network <NUM>, one or more terminals <NUM>, a processing engine <NUM>, and a storage <NUM>. In some embodiments, the scanner <NUM>, the processing engine <NUM>, the storage <NUM>, and/or the terminal(s) <NUM> are connected to and/or communicate with each other via a wireless connection (e.g., the network <NUM>), a wired connection, or a combination thereof. The connection between the components in the imaging system <NUM> is variable. Merely by way of example, the scanner <NUM> is connected to the processing engine <NUM> through the network <NUM>, as illustrated in <FIG>. As another example, the scanner <NUM> is connected to the processing engine <NUM> directly. As a further example, the storage <NUM> is connected to the processing engine <NUM> through the network <NUM>, as illustrated in <FIG>, or connected to the processing engine <NUM> directly.

The scanner <NUM> scans an object, and/or generate a plurality of data relating to the object. In some embodiments, the scanner <NUM> is a medical imaging device, for example, a PET device, a PET-CT device, a PET-MRI device, etc. The scanner <NUM> includes a supporting assembly <NUM> (e.g., a gantry), a detector assembly <NUM>, a detection region <NUM>, a table <NUM>, an electronics module <NUM>, and a cooling assembly <NUM>. A subject is placed on the table <NUM> for scanning. In the present disclosure, "object" and "subject" are used interchangeably. The detector assembly <NUM> detects radiation events (e.g., gamma photons) emitted from the detection region <NUM>. In some embodiments, the detector assembly <NUM> includes one or more detectors. The detectors are implemented in any suitable manner, for example, a ring, an arc, a rectangle, an array, or the like, or any combination thereof. See, for example, <FIG> and the description thereof. In some embodiments, a detector includes one or more crystal elements and/or one or more photomultipliers (e.g., silicon photomultiplier (SiPM), photomultiplier tube (PMT)). See, for example, <FIG> and the description thereof. The table <NUM> positions a subject in the detection region <NUM>. The electronics module <NUM> collects electrical signals generated based on the radiation events detected by the detector assembly <NUM>. The cooling assembly <NUM> cools the detector assembly <NUM>. More descriptions of the supporting assembly <NUM>, the detector assembly <NUM>, the table <NUM>, the electronics module <NUM>, and the cooling assembly <NUM> are found elsewhere in the present disclosure. See, for example, <FIG> and the description thereof.

The network <NUM> includes any suitable network that can facilitate exchange of information and/or data for the imaging system <NUM>. In some embodiments, one or more components of the imaging system <NUM> (e.g., the scanner <NUM>, the terminal <NUM>, the processing engine <NUM>, the storage <NUM>, etc.) communicate information and/or data with one or more other components of the imaging system <NUM> via the network <NUM>. For example, the processing engine <NUM> obtains image data from the scanner <NUM> via the network <NUM>. As another example, the processing engine <NUM> obtains user instructions from the terminal <NUM> via the network <NUM>. The network <NUM> is and/or includes 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 <NUM> 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, routers, hubs, witches, server computers, and/or any combination thereof. Merely by way of example, the network <NUM> includes a cable network, a wireline network, a fiber-optic network, a telecommunications network, an intranet, a wireless local area network (WLAN), a metropolitan area network (MAN), a public telephone switched network (PSTN), a Bluetooth™ network, a ZigBee™ network, a near field communication (NFC) network, or the like, or any combination thereof. In some embodiments, the network <NUM> includes one or more network access points. For example, the network <NUM> includes wired and/or wireless network access points such as base stations and/or internet exchange points through which one or more components of the imaging system <NUM> are connected to the network <NUM> to exchange data and/or information.

The terminal(s) <NUM> includes a mobile device <NUM>-<NUM>, a tablet computer <NUM>-<NUM>, a laptop computer <NUM>-<NUM>, or the like, or any combination thereof. In some embodiments, the mobile device <NUM>-<NUM> includes a smart home device, a wearable device, a mobile device, a virtual reality device, an augmented reality device, or the like, or any combination thereof. In some embodiments, the smart home device includes a smart lighting device, a control device of an intelligent electrical apparatus, a smart monitoring device, a smart television, a smart video camera, an interphone, or the like, or any combination thereof. In some embodiments, the wearable device includes a bracelet, a footgear, eyeglasses, a helmet, a watch, clothing, a backpack, a smart accessory, or the like, or any combination thereof. In some embodiments, the mobile device includes a mobile phone, a personal digital assistance (PDA), a gaming device, a navigation device, a point of sale (POS) device, a laptop, a tablet computer, a desktop, or the like, or any combination thereof. In some embodiments, the virtual reality device and/or the augmented reality device includes a virtual reality helmet, virtual reality glasses, a virtual reality patch, an augmented reality helmet, augmented reality glasses, an augmented reality patch, or the like, or any combination thereof. For example, the virtual reality device and/or the augmented reality device includes a Google Glass™, an Oculus Rift™ a Hololens™, a Gear VR™, etc. In some embodiments, the terminal(s) <NUM> are part of the processing engine <NUM>.

The processing engine <NUM> processes data and/or information obtained from the scanner <NUM>, the terminal(s) <NUM>, and/or the storage <NUM>. For example, the processing engine <NUM> processes image data and reconstructs an image based on the image data. In some embodiments, the processing engine <NUM> is a single server or a server group. The server group is centralized or distributed. In some embodiments, the processing engine <NUM> is local or remote. For example, the processing engine <NUM> accesses information and/or data stored in the scanner <NUM>, the terminal(s) <NUM>, and/or the storage <NUM> via the network <NUM>. As another example, the processing engine <NUM> is directly connected to the scanner <NUM>, the terminal(s) <NUM> and/or the storage <NUM> to access stored information and/or data. In some embodiments, the processing engine <NUM> is implemented on a cloud platform. Merely by way of example, the cloud platform includes a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an inter-cloud, a multi-cloud, or the like, or any combination thereof. In some embodiments, the processing engine <NUM> is implemented by a computing device. In some embodiments, the processing engine <NUM>, or a portion of the processing engine <NUM> is integrated into the scanner <NUM>.

In some embodiments, a computing device includes a processor, a storage, an input/output (I/O), and a communication port. The processor executes computer instructions (e.g., program code) and perform functions of the processing engine <NUM> in accordance with techniques described herein. The computer instructions include, for example, routines, programs, objects, components, data structures, procedures, modules, and functions, which perform particular functions described herein. In some embodiments, the processor includes one or more hardware processors, such as a microcontroller, a microprocessor, a reduced instruction set computer (RISC), an application specific integrated circuits (ASICs), an application-specific instruction-set processor (ASIP), a central processing unit (CPU), a graphics processing unit (GPU), a physics 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 processor capable of executing one or more functions, or the like, or any combinations thereof.

The storage stores data/information obtained from the scanner <NUM>, the terminal(s) <NUM>, the storage <NUM>, and/or any other component of the imaging system <NUM>. In some embodiments, the storage includes a mass storage, a removable storage, a volatile read-and-write memory, a read-only memory (ROM), or the like, or any combination thereof. For example, the mass storage includes a magnetic disk, an optical disk, a solid-state drives, etc. The removable storage includes a flash drive, a floppy disk, an optical disk, a memory card, a zip disk, a magnetic tape, etc. The volatile read-and-write memory includes a random access memory (RAM). The RAM includes a dynamic RAM (DRAM), a double date rate synchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristor RAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc. The ROM includes a mask ROM (MROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a compact disk ROM (CD-ROM), and a digital versatile disk ROM, etc. In some embodiments, the storage stores one or more programs and/or instructions to perform exemplary methods described in the present disclosure.

The I/O inputs and/or outputs signals, data, information, etc. In some embodiments, the I/O enables a user interaction with the processing engine <NUM>. In some embodiments, the I/O includes an input device and an output device. Examples of the input device include a keyboard, a mouse, a touch screen, a microphone, or the like, or a combination thereof. Examples of the output device include a display device, a loudspeaker, a printer, a projector, or the like, or a combination thereof. Examples of the display device include a liquid crystal display (LCD), a light-emitting diode (LED)-based display, a flat panel display, a curved screen, a television device, a cathode ray tube (CRT), a touch screen, or the like, or a combination thereof.

The communication port is connected to a network (e.g., the network <NUM>) to facilitate data communications. The communication port establishes connections between the processing engine <NUM> and the scanner <NUM>, the terminal(s) <NUM>, and/or the storage <NUM>. The connection is a wired connection, a wireless connection, any other communication connection that can enable data transmission and/or reception, and/or any combination of these connections. The wired connection includes, for example, an electrical cable, an optical cable, a telephone wire, or the like, or any combination thereof. The wireless connection includes, for example, a Bluetooth™ link, a Wi-Fi™ link, a WiMax™ link, a WLAN link, a ZigBee link, a mobile network link (e.g., <NUM>, <NUM>, <NUM>, etc.), or the like, or a combination thereof. In some embodiments, the communication port is and/or includes a standardized communication port, such as RS232, RS485, etc. In some embodiments, the communication port is a specially designed communication port. For example, the communication port is designed in accordance with the digital imaging and communications in medicine (DICOM) protocol.

The storage <NUM> stores data, instructions, and/or any other information. In some embodiments, the storage <NUM> stores data obtained from the terminal(s) <NUM> and/or the processing engine <NUM>. In some embodiments, the storage <NUM> stores data and/or instructions that the processing engine <NUM> executes or uses to perform exemplary methods described in the present disclosure. In some embodiments, the storage <NUM> includes a mass storage, a removable storage, a volatile read-and-write memory, a read-only memory (ROM), or the like, or any combination thereof. Exemplary mass storage includes a magnetic disk, an optical disk, a solid-state drive, etc. Exemplary removable storage includes a flash drive, a floppy disk, an optical disk, a memory card, a zip disk, a magnetic tape, etc. Exemplary volatile read-and-write memory includes a random access memory (RAM). Exemplary RAM includes a dynamic RAM (DRAM), a double date rate synchronous dynamic RAM (DDR SDRAM), a static RAM (SRAM), a thyristor RAM (T-RAM), and a zero-capacitor RAM (Z-RAM), etc. Exemplary ROM includes a mask ROM (MROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a compact disk ROM (CD-ROM), and a digital versatile disk ROM, etc. In some embodiments, the storage <NUM> is implemented on a cloud platform. Merely by way of example, the cloud platform includes a private cloud, a public cloud, a hybrid cloud, a community cloud, a distributed cloud, an inter-cloud, a multi-cloud, or the like, or any combination thereof.

In some embodiments, the storage <NUM> is connected to the network <NUM> to communicate with one or more other components in the imaging system <NUM> (e.g., the processing engine <NUM>, the terminal(s) <NUM>, etc.). One or more components in the imaging system <NUM> accesses the data or instructions stored in the storage <NUM> via the network <NUM>. In some embodiments, the storage <NUM> is directly connected to or communicate with one or more other components in the imaging system <NUM> (e.g., the processing engine <NUM>, the terminal(s) <NUM>, etc.). In some embodiments, the storage <NUM> is part of the processing engine <NUM>.

<FIG> is a schematic diagram illustrating an exemplary scanner <NUM> according to some embodiments of the present disclosure. As illustrated in <FIG>, the scanner <NUM> includes a supporting assembly <NUM>, a detector assembly <NUM>, a table <NUM>, an electronic module <NUM>, and a cooling assembly <NUM>.

The supporting assembly <NUM> supports one or more parts of the scanner <NUM>, for example, the detector assembly <NUM>, electronic module <NUM>, the cooling assembly <NUM>, etc. In some embodiments, the supporting assembly <NUM> includes a main gantry, a gantry base, a front cover plate, and a back cover plate (not shown). The front cover plate is connected with the gantry base. The front cover plate is substantially perpendicular to the gantry base. The main gantry is mounted on a side face of the front cover plate. The main gantry includes one or more supporting frames to contain the detector assembly <NUM> and/or the electronic module <NUM>. The main gantry includes a substantially circular opening (e.g., the detection region <NUM>) to accommodate a scanned object. In some embodiments, the opening of the main gantry is of another shape including, for example, an oval. The term "subject" and the term "object" are used interchangeably in the present disclosure, unless stated otherwise. The back cover plate is mounted on a side face of the main gantry opposite to the front cover plate. The gantry base supports the front cover plate, the main gantry, and/or the back cover plate. In some embodiments, the scanner <NUM> includes a shell (e.g., a shell <NUM> illustrated in <FIG>) to cover and protect the main gantry.

The detector assembly <NUM> detects radiation events (e.g., gamma photons) emitted from the detection region <NUM>. In some embodiments, the detector assembly <NUM> receives radiation rays (e.g., gamma rays) and generates electrical signals. The detector assembly <NUM> includes one or more detector units. One or more detector units are packaged to form a detector block. More descriptions of the detector block are found elsewhere in the present disclosure. See, for example, <FIG> and the description thereof. One or more detector blocks are packaged to form a detector cassette. One or more detector cassettes are arranged to form a detector ring. One or more detector rings are arranged to form a detector module. More descriptions of the detector ring are found elsewhere in the present disclosure. See, for example, <FIG> and the description thereof.

The table <NUM> supports an object and position the object at a desired position in the detection region <NUM>. In some embodiments, the object lays on the table <NUM>. The table <NUM> is moved under the control of the control module <NUM> and reaches a desired position in the detection region <NUM>. In some embodiments, the scanner <NUM> has a relatively long axial field-of-view (AFOV) (see <FIG>), for example, <NUM>-meter long AFOV, and correspondingly, the table <NUM> is moved in a wide range (e.g., ><NUM> meters) along the axial direction.

The electronics module <NUM> collects and/or processes the electrical signals generated by the detector assembly <NUM>. The electronics module <NUM> inlucdes an adder, a multiplier, a subtracter, an amplifier, a drive circuit, a differential circuit, a integral circuit, a counter, a filter, an analog-to-digital converter (ADC), a lower limit detection (LLD) circuit, a constant fraction discriminator (CFD) circuit, a time-to-digital converter (TDC), a coincidence circuit, or the like, or any combination thereof. The electronics module <NUM> converts an analog signal relating to an energy of radication rays received by the detector assembly <NUM> to a digital signal. The electronics module <NUM> compares a plurality of digital signals, analyzes the plurality of digital signals, and determines an interaction position and/or an interaction time of the received radication rays in the detector assembly <NUM>. The electronics module <NUM> determines one or more coincidence events based on the plurality of digital signals. The electronics module <NUM> determines image data based on the coincidence events and the energies of radiation rays recognized as the coincidence events. In some embodiments, if the detector assembly <NUM> has a large axial FOV (e.g., <NUM> meters to <NUM> meters), the electronics module <NUM> has a high data input rate from multiple detector channels. For example, the electronics module <NUM> handles up to tens of billion events (e.g., coincidence events, single events, etc.) per second. In some embodiments, the data input rate relates to the number of detector units in the detector assembly <NUM>.

The cooling assembly <NUM> produces, transfers, delivers, channels, or circulates a cooling medium to the scanner <NUM> to absorb heat produced by the scanner <NUM> during an imaging procedure. In some embodiments, the cooling assembly <NUM> is entirely integrated into the scanner <NUM> and become a part of the scanner <NUM>. In some embodiments, the cooling assembly <NUM> is partially integrated into the scanner <NUM> and associated with the scanner <NUM>. The cooling assembly <NUM> allows the scanner <NUM> to maintain a suitable and stable working temperature (e.g., <NUM>, <NUM>, <NUM>, etc.). In some embodiments, the cooling assembly <NUM> controls the temperature of one or more target components of the scanner <NUM>. The target components include the detector assembly <NUM>, the electronics module <NUM>, and/or any other component that generates heat in operation. The cooling medium is gaseous, liquid (e.g., water), or the like, or any combination thereof. In some embodiments, the gaseous cooling medium is air. More descriptions of the cooling assembly <NUM> are found elsewhere in the present disclosure. See, for example, <FIG> and the description thereof.

<FIG> is a schematic diagram illustrating a side view of an exemplary scanner <NUM>. As illustrated in <FIG>, a plurality of detector cassettes <NUM> are arranged in substantially a ring configuration (also referred to as a detector ring) in the transverse plane. A detector cassette <NUM> includes one or more detector blocks <NUM>. An exemplary detector block <NUM> is found in <FIG>. The detector cassettes <NUM> are covered and protected by a shell <NUM>. In some embodiments, the shell <NUM> is a hollow cylinder. The region encircled by the detector cassettes <NUM> is the detection region <NUM>. The detection region <NUM> accommodates a subject <NUM> to be scanned. The subject <NUM> is supported on the table <NUM>. In some embodiments, if the subject <NUM> is positioned within the range of a transverse FOV, radiation rays emitted from the subject <NUM> are detected by the detector cassettes <NUM>. More descriptions of the transverse FOV are found elsewhere in the present disclosure. See, for example, <FIG> and the description thereof.

<FIG> are schematic diagrams illustrating an exemplary detector block <NUM> according to some embodiments of the present disclosure. A detector block <NUM> includes one or more crystal elements (e.g., the scintillator crystal array <NUM>) and one or more photosensor arrays <NUM>.

As shown in <FIG>, the crystal elements are configured as a scintillator crystal array <NUM> (also referred to as scintillator array <NUM>). The scintillator array <NUM> includes one or more scintillators (e.g., the scintillator <NUM>-<NUM>, the scintillator <NUM>-<NUM>, the scintillator <NUM>-<NUM>, the scintillator <NUM>-<NUM>, etc. as illustrated in <FIG>). A scintillator scintillates when a radiation ray (e.g., γ ray) photon impinges on the scintillator. The scintillator absorbs the energy of the radiation ray (e.g., γ ray) photon, and converts the absorbed energy into light. In some embodiments, the scintillators of the scintillator array <NUM> are arranged in N rows and M columns. N is an integer larger than <NUM>. M is an integer larger than <NUM>. In some embodiments, N is equal to M. In some embodiments, N is different from M. In some embodiments, the N×M scintillator array is obtained by making partial cuts through a crystal with a saw. In some embodiments, the cuts are made to various depths. In some embodiments, the deepest cut is at the edge of the detector block <NUM>. In some embodiments, two adjacent scintillators of the scintillator array <NUM> are filled with a barrier material (e.g., a light-reflective film, etc.). The scintillator uses one or more types of crystals including, for example, Nal(TI), BGO, LSO, YSO, GSO, LYSO, LaBr<NUM>, LFS, LuAP, Lul<NUM>, BaF<NUM>, CeF, Csl(TI), Csl(Na), CaF<NUM>(Eu), CdWO<NUM>, YAP, or the like, or any combination thereof. Exemplary physical properties of some scintillators are found in Table <NUM>.

<FIG> illustrates an exemplary <NUM>×<NUM> scintillator array. The scintillator array <NUM> has a first surface and a second surface opposite to the first surface. The first surface is a common face of one end of the scintillators (e.g., a top surface) in the scintillator array <NUM>. The second surface is a common face of the other end of the scintillators (e.g., a bottom surface) in the scintillator array <NUM>. In some embodiments, the first surface or the second surface faces the detection region <NUM>.

A photosensor array <NUM> includes one or more photosensors (e.g., the photosensor <NUM>-<NUM>, the photosensor <NUM>-<NUM>, the photosensor <NUM>-<NUM>, the photosensor <NUM>-<NUM>, etc. as illustrated in <FIG>). A photosensor converts a light signal (e.g., the light output from a scintillator) to an electrical signal. In some embodiments, a photosensor is a photomultiplier tube (PMT), a silicon photomultiplier (SiPM), etc. In some embodiments, a photosensor (e.g., PMT, or SiPM) is a single-channel photosensor or a multi-channel photosensor. The photosensor array <NUM> is coupled to the scintillator array <NUM>. In some embodiments, the photosensor array <NUM> is arranged on the first surface or the second surface of the scintillator array <NUM>. In some embodiments, two photosensor arrays are arranged on the first surface and the second surface of the scintillator array <NUM>, respectively. In some embodiments, the photosensors of the photosensor array <NUM> are arranged in N' rows and M' columns. N' is an integer larger than <NUM> but no larger than N. M' is an integer larger than <NUM> but no larger than M. In some embodiments, a photosensor is coupled to one or more scintillators of the scintillator array <NUM> simultaneously.

It should be noted that the above description of the detector block <NUM> is merely provided for the purpose of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be made to the detector module <NUM> under the teachings of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, one or more light guides may be configured between the scintillator array <NUM> and the photosensor array <NUM>.

<FIG> are schematic diagrams illustrating exemplary detector rings according to some embodiments of the present disclosure. In some embodiments, a plurality of detector cassettes (or detector blocks) are arranged in an array of full or partial rings. A detector ring includes one or more rings of detector blocks. For example, as illustrated in <FIG>, a detector ring includes four rings of detector blocks. A detector ring has a diameter of <NUM> centimeters to <NUM> centimeters. In some embodiments, a detector ring with the full ring configuration is configured in a circular form (see <FIG>), hexagonal form (see <FIG>), elliptic form, or another polygon form. In some embodiments, a detector ring with a partial ring configuration is realized based on two or more detector blocks. A detector block is curved or flat. <FIG> illustrates a partial ring with a <NUM>° angular shift between two curved detector blocks. <FIG> illustrates a partial ring with six uniformly spaced curved detector blocks. In some embodiments, with the partial ring geometry, the transverse FOV of the detector ring is increased based on the same total crystal volume of the detector ring. In some embodiments, a plurality of detector rings are configured successively in the axial direction to form a detector assembly with a large axial length (e.g., <NUM> meters to <NUM> meters). In a detector assembly, at least one of the detector rings has the full ring configuration, and/or at least one of the detector rings may be have the partial ring configuration. The detector assembly with a large axial length has a large axial FOV (e.g., <NUM> to <NUM>). In some embodiments, the detector assembly with a large axial length realizes whole-body scanning.

<FIG> is a schematic diagram illustrating an exemplary scanner <NUM> according to some embodiments of the present disclosure. As shown in <FIG>, the scanner <NUM> includes a supporting assembly <NUM>, a detector assembly <NUM>, and a table <NUM>. The supporting assembly <NUM> is configured to support other components in the scanner <NUM> including, for example, the detector assembly <NUM>, a cooling assembly (not shown in <FIG>), etc. For example, the supporting assembly <NUM> is configured to support the detector assembly <NUM> and/or drive the detector assembly <NUM> to move, such as rotate, translate, swing, etc. In some embodiments, the supporting assembly <NUM> includes a bore (e.g., the detection region <NUM>). The bore has a first transverse diameter (or referred to as a bore transverse diameter) and a first axial length (or referred to as a bore axial length). The bore axial length is defined as the distance from one end of the bore to an opposite end of the bore along a Z axis direction (i.e., the axial direction) indicated by the arrow as shown in <FIG>. The bore axial length also refers to a length of the supporting assembly <NUM> along the Z axis direction. In some embodiments, the bore axial length of the supporting assembly <NUM> is in a range from <NUM> meters to <NUM> meters. In some embodiments, the bore axial length of the supporting assembly <NUM> exceeds <NUM> meters.

The detector assembly <NUM> includes one or more detector modules (e.g., the detector modules <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-(N-<NUM>), <NUM>-N as shown in <FIG>). A detector module includes one or more detector blocks. In some embodiments, the detector blocks are arranged on an inner wall of the supporting assembly <NUM> in a certain number of rings. In some embodiments, the detector assembly <NUM> has a second transverse diameter (or referred to as the transverse diameter of the detector assembly) and a second axial length (or referred to as the axial length of the detector assembly). The axial length of the detector assembly is defined as a distance from one end of the detector assembly <NUM> to an opposite end of the detector assembly <NUM> along the Z axis direction. The axial length of the detector assembly also refers to the length of the detector assembly <NUM> in the Z axis direction. The transverse diameter of the detector assembly is defined as a diameter of a detector ring on the transverse plane perpendicular to the Z axis direction.

In some embodiments, the axial length of the detector assembly relates to an axial field-of-view (AFOV) of the scanner <NUM>. As used herein, the AFOV refers to a maximum length along the Z axis direction of the detector assembly <NUM> to detect a coincidence event effectively (see <FIG>). The greater the axial length of the detector assembly <NUM> is, the larger the AFOV of the scanner <NUM> may be. For instance, the axial length of the detector assembly <NUM> is in a range from <NUM> meters to <NUM> meters. In some embodiments, the axial length of the detector assembly <NUM> exceeds <NUM> meters, or <NUM> meter, or <NUM> meters, or <NUM> meters. Correspondingly, the axial length of the AFOV exceeds <NUM> meters, or <NUM> meter, or <NUM> meters, or <NUM> meters. Multiple organs (e.g., a head, a heart, a lung, a liver, a stomach, a pancreas, a bladder, a knee, etc.) of a subject are scanned in a single scan. As another example, the axial length of the detector assembly <NUM> is in a range from <NUM> meters to <NUM> meters. The region between the head and the thigh of a subject (e.g., an adult patient) is scanned in a single scan, or a whole-body scan is achieved in a single scan of a subject of a small size (e.g., a child). As a further example, the axial length of the detector assembly <NUM> is in the range from <NUM> meters to <NUM> meters, or exceeds <NUM> meters. In some embodiments, the bore axial length of the supporting assembly <NUM> is equal to or greater than the axial length of the detector assembly <NUM>.

The transverse diameter of the detector assembly <NUM> relates to a transverse field-of-view (FOV) of the scanner <NUM>. The transverse FOV relates to an angle of acceptance for a scintillator of the detector assembly <NUM> to detect a coincidence event on the transverse plane (see <FIG>). The greater the transverse diameter of the detector assembly <NUM> is, the larger the transverse FOV of the scanner <NUM> may be. The transverse diameter of the detector assembly <NUM> is smaller than the bore transverse diameter.

<FIG> is a schematic diagram illustrating an exemplary detector assembly <NUM> of <FIG> illustrated in a two-dimensional plane according to some embodiments of the present disclosure. As shown in <FIG>, the supporting assembly <NUM> is an integrated structure. The detector assembly <NUM> includes one or more detector modules (e.g., the detector modules <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-(N-<NUM>), <NUM>-N, etc.). Multiple detector modules are mounted on the supporting assembly <NUM>. Two adjacent detector modules are spaced with a first gap (or referred to as a module gap) d<NUM> in the Z axis direction. In some embodiments, the first gap d<NUM> between two adjacent detector modules is less than <NUM> millimeters (e.g., <NUM> millimeter, <NUM> millimeters, <NUM> millimeters, <NUM> millimeters, etc.). In some embodiments, the first gaps d<NUM> between any two adjacent detector modules in the detector assembly <NUM> is equal to or less than <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeter. In some embodiments, the first gap d<NUM> is less than a width of a scintillator in the Z axis direction. In some embodiments, the first gap d<NUM> between different detector modules is the same or different. For example, two adjacent detector modules (e.g., a first detector module and a second detector module) are spaced by <NUM> millimeters, while two adjacent detector modules (e.g., a third detector module and a fourth detector module) may be spaced by <NUM> millimeters. As another example, the detector modules in the detector assembly <NUM> are spaced uniformly in the Z axis direction.

A detector module includes one or more detector blocks (or detector units, detector cassettes) as described in connection with <FIG>, and/or 4C. The detector blocks (or detector units, detector cassettes) are configured as one or more detector rings (e.g., detector rings with a full ring configuration and/or detector rings with a partial ring configuration) of a detector module. In a detector module, two adjacent detector rings are spaced with a second gap (or referred to as a ring gap) d<NUM> in the Z axis direction. In some embodiments, the second gap d<NUM> is less than <NUM> (e.g., <NUM>, <NUM>, <NUM>, etc.). In some embodiments, the second gap d<NUM> between two adjacent detector rings is less than <NUM> millimeters. In some embodiments, the second gap d<NUM> between two adjacent detector rings is less than <NUM> millimeters. In some embodiments, the gap d<NUM> of two adjacent detector modules is the same as or different from the gap d<NUM> of two adjacent detector rings.

In some embodiments, the number of detector blocks (or detector units, detector cassettes) in different detector modules is the same or different. For example, the detector module <NUM>-<NUM> and the detector module <NUM>-<NUM> includes the same number of detector blocks. As another example, the detector module <NUM>-(N-<NUM>) and the detector module <NUM>-N have different numbers of detector blocks. In some embodiments, the sizes of detector blocks (or detector units, detector cassettes) in different detector modules are the same or different. In some embodiments, the sizes of detector blocks (or detector units, detector cassettes) in the same detector module are the same or different. In some embodiments, the transverse diameters of detector rings in different detector modules are the same or different. In some embodiments, the transverse diameters of detector rings in the same detector module are the same or different.

<FIG> is a schematic diagram illustrating another exemplary scanner <NUM> according to some embodiments of the present disclosure. As shown in <FIG>, the scanner <NUM> includes a supporting assembly <NUM>, a detector assembly <NUM>, and a table <NUM>. In some embodiments, the supporting assembly <NUM> is not an integrated structure. The supporting assembly <NUM> includes one or more supporting modules, for example, a supporting module <NUM>-<NUM>, a supporting module <NUM>-<NUM>,. , a supporting module <NUM>-(N-<NUM>), a supporting module <NUM>-N, etc. The detector assembly <NUM> includes one or more detector modules, for example, a detector module <NUM>-<NUM>, a detector module <NUM>-<NUM>,. , a detector module <NUM>-(N-<NUM>), a detector module <NUM>-N, etc., as descried in <FIG>. As shown in <FIG>, the multiple detector modules are mounted on the multiple supporting modules, respectively. For example, the detector module <NUM>-<NUM> is mounted on the supporting module <NUM>-<NUM>, the detector module <NUM>-<NUM> is mounted on the supporting module <NUM>-<NUM>, the detector module <NUM>-(N-<NUM>) is mounted on the supporting module <NUM>-(N-<NUM>), and the detector module <NUM>-N is mounted on the supporting module <NUM>-N. In some embodiments, two adjacent supporting modules are connected to each other by way of, such as, for example, welding, riveting, bolting, etc. In some embodiments, a detector module is assembled on a supporting module to configure an imaging unit (e.g., a PET unit). In some embodiments, different imaging units are used to scan different portions of a subject. In some embodiments, the length of an axial FOV of an imaging unit ranges from <NUM> meters to <NUM> meters. In some embodiments, the length of an axial FOV of an imaging unit ranges from <NUM> meters to <NUM> meters. In some embodiments, the length of an axial FOV of an imaging unit is equal to or larger than a width of a detector block in the axial direction. In some embodiments, one or more imaging units are assembled in the scanner <NUM> along the Z axis direction to obtain a large AFOV (e.g., <NUM> meters to <NUM> meters) for whole-body scanning (see, <FIG>). In some embodiments, the axial length of the AFOV exceeds <NUM> meters, or <NUM> meter, or <NUM> meters, or <NUM> meters.

In some embodiments, each imaging unit has a center (e.g., a center in the transverse plane). In some embodiments, a deviation of the center of a first imaging unit (e.g., the imaging unit assembled based on the supporting module <NUM>-<NUM> and the detector module <NUM>-<NUM>) and the center of a second imaging unit (i.e., an imaging unit other than the first imaging unit, e.g., the imaging unit assembled based on the supporting module <NUM>-N and the detector module <NUM>-N) is below or equal to x millimeters. In some embodiments, x may be less than <NUM> millimeter. In some embodiments, x ranges from <NUM> millimeters to <NUM> millimeter. In some embodiments, x is less than <NUM> millimeters. In some embodiments, a deviation of the center of a first imaging unit and the center of a second imaging unit that is located adjacent to the first imaging unit is below or equal to <NUM> millimeter, or <NUM> millimeters, or <NUM> millimeters. In some embodiments, one or more imaging units are adjusted in the transverse plane, so that the transverse plane of the imaging unit(s) is substantially parallel to the transverse plane of the scanner <NUM>.

<FIG> is a schematic diagram illustrating an exemplary detector assembly <NUM> of <FIG> illustrated in a two-dimensional plane according to some embodiments of the present disclosure. As illustrated in <FIG>, two adjacent detector modules are spaced by a first gap d<NUM>. In some embodiments, the first gap d<NUM> is less than a width of a scintillator in the Z axis direction. The second gap d<NUM> between adjacent detector rings is similar to that described in <FIG>. Two adjacent supporting modules are spaced by a third gap d<NUM>. In some embodiments, the third gap d<NUM> is less than the first gap d<NUM>. In some embodiments, the third gap d<NUM> between two adjacent supporting modules is less than <NUM> millimeters. In some embodiments, the third gap d<NUM> between two adjacent supporting modules is less than <NUM> millimeters. In some embodiments, the third gap d<NUM> between two adjacent supporting modules is less than <NUM> millimeters. In some embodiments, the first gap d<NUM>, the second gap d<NUM>, and/or the third gap d<NUM> are the same or different. For example, the first gap d<NUM> and the second gap d<NUM> are equal. As another example, the third gap d<NUM> is greater than the second gap d<NUM>.

<FIG> is a schematic diagram illustrating an exemplary multi-modal scanner <NUM> according to some embodiments of the present disclosure. As shown in <FIG>, the multi-modal scanner <NUM> includes a first scanner <NUM>, a PET scanner <NUM>, a position adjustment assembly <NUM>, a rail <NUM>, and a detection region (not shown).

In some embodiments, the first scanner <NUM> includes a computed tomography (CT) scanner, an X-rays scanner, an MRI scanner, or the like, or a combination thereof. The first scanner <NUM> is positioned at the front of the PET scanner <NUM> in the Z axis direction. In some embodiments, the first scanner <NUM> includes an X ray emission device and a first detector assembly. The first detector assembly forms a first portion of the detection region. The first detector assembly is configured to detect at least a portion of an X ray beam emitted by the X ray emission device and traversing the subject located within the first portion of the detection region.

The PET scanner <NUM> includes one or more PET units (e.g., a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, a PET unit <NUM>, etc.). In some embodiments, a PET unit includes a detector module (e.g., the detector modules <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N as shown in <FIG>) and a supporting module (e.g., the supporting modules <NUM>-<NUM>, <NUM>-<NUM>,. , <NUM>-N as shown in <FIG>). In some embodiments, one or more detector modules of the PET scanner <NUM> form a second portion of the detection region. Two adjacent PET units are connected by way of, for example, bolting, riveting, screwing, welding, or the like, or a combination thereof. In some embodiments, the two adjacent PET units are spaced with a gap <NUM> ranging from <NUM> millimeter to <NUM> millimeters. In some embodiments, the gap <NUM> between two adjacent PET units is in a range from <NUM> millimeters to <NUM> millimeters. In some embodiments, the gap <NUM> between two adjacent PET units is in a range from <NUM> millimeters to <NUM> millimeters. In some embodiments, the gap <NUM> is less than a width of a scintillator in the Z axis direction. In some embodiments, the length of an axial FOV of a PET unit ranges from <NUM> meters to <NUM> meters. In some embodiments, the length of an axial FOV of a PET unit ranges from <NUM> meters to <NUM> meters. In some embodiments, the length of an axial FOV of an imaging unit is equal to or larger than a width of a detector block in the axial direction.

The position adjustment assembly <NUM> is configured to adjust the positions of the PET scanner <NUM> (e.g., the multiple PET units) and/or the first scanner <NUM> for alignment in the Z axis direction and/or in the transverse plane. In some embodiments, the position adjustment assembly <NUM> includes one or more position adjustment modules. A position adjustment module is associated with one of the multiple PET units. The position adjustment module is configured to move a PET unit associated with the position adjustment module.

In some embodiments, each PET unit has a center (e.g., a center in the transverse plane). In some embodiments, a deviation of the center of a first PET unit (e.g., the PET unit <NUM>) and the center of a second imaging unit (i.e., a PET unit other than the first PET unit, e.g., the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, etc.) is below or equal to y millimeters. In some embodiments, y is less than <NUM> millimeter. In some embodiments, y ranges from <NUM> millimeters to <NUM> millimeter. In some embodiments, y is less than <NUM> millimeters. In some embodiments, a deviation of the center of a first PET unit (e.g., the PET unit <NUM>) and the center of a second PET unit (e.g., the PET unit <NUM>) that is located adjacent to the first PET unit is below or equal to <NUM> millimeter, or <NUM> millimeters, or <NUM> millimeters. In some embodiments, the deviation of the center of different PET units is adjusted by the position adjustment assembly <NUM>. In some embodiments, the deviation of the centers of the first scanner <NUM> and the PET scanner <NUM> is adjusted by another position adjustment assembly (not shown). In some embodiments, one or more PET units are adjusted in the transverse plane, so that the transverse plane of the PET unit(s) is substantially parallel to the transverse plane of the multi-modal scanner <NUM>. In some embodiments, the first scanner <NUM> and/or the PET scanner <NUM> is adjusted in the transverse plane, so that the transverse plane of the first scanner <NUM> and/or the PET scanner <NUM> is substantially parallel to the transverse plane of the multi-modal scanner <NUM>.

The rail <NUM> includes a support rail <NUM> and a service rail <NUM>. In some embodiments, the support rail <NUM> is configured to support the position adjustment assembly <NUM>. The supporting rail <NUM> guides the PET unit(s) to be assembled or detached. In some embodiments, the support rail <NUM> includes one or more slides. The position adjustment assembly <NUM> moves along the multiple slides. In some embodiments, one or more of the PET units are detachable. A PET unit is assembled to or detached from the PET scanner <NUM> through the slide(s). The service rail <NUM> is configured to support the multi-modal scanner <NUM>. In some embodiments, the service rail <NUM> includes multiple wheels. The multi-modal scanner <NUM> moves with the wheels. In some embodiments, the service rail <NUM> is detachable with the multi-modal scanner <NUM>. More descriptions of the multi-modal scanner <NUM> are found in <CIT>, and <CIT>.

As illustrated in <FIG>, a PET scanner with large AFOV (e.g., <NUM> meters to <NUM> meters) facilitates whole-body scanning. Thus, a low-dose scan, a fast scan, a whole-body dynamic scan are achieved. For a scan using a traditional PET scanner, the injection dose of fluorodeoxyglucose is <NUM> mci, a corresponding radiation dosage is <NUM> mSv. A PET scanner with large AFOV (e.g., <NUM> meters to <NUM> meters), the radiation dose for a scan is less than <NUM> mSv, about one tenth of a current level. The PET scanner with a large AFOV (e.g., <NUM> meters to <NUM> meters) is used in a physical examination, the scanning of a child, etc. For a PET-CT scanner, the radiation dose for whole-body CT scanning is in a range from <NUM> mSv to <NUM> mSv (<NUM> kV, <NUM>-<NUM> mAs/slice). The radiation dose for CT scanning is reduced by way of dose modulation, iterative reconstruction, using PET topogram instead of CT topogram, etc..

In some embodiments, the sensitivity of the PET scanner with a large AFOV (e.g., <NUM> meters to <NUM> meters) is not less than <NUM> cps/kBq. In some embodiments, the scanning time for a scan is less than <NUM> seconds. In some embodiments, the scanning time for a whole-body scan is within <NUM> seconds to <NUM> seconds. A single-breath hold is enough for whole-body scan. In some embodiments, a fast scan reduces motion artifact. In some embodiments, the spatial resolution of the PET scanner with a large AFOV (e.g., <NUM> meters to <NUM> meters) is not less than <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeter. For instance, the spatial resolution of the PET scanner with a large AFOV (e.g., <NUM> meters to <NUM> meters) is <NUM> millimeters, or <NUM> millimeters, or <NUM> millimeters, or less than <NUM> millimeters.

It should be noted that the above description of the diagrams in <FIG> is merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations or modifications may be made under the teachings of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, the scanner <NUM> in <FIG> further includes one or more components, such as one or more electronics modules. As another example, the number of PET units in <FIG> is any integer larger than <NUM> (e.g., <NUM>). As still another example, the number of imaging units in <FIG> is any integer larger than <NUM> (e.g., <NUM>, or a number between <NUM> and <NUM>).

<FIG> is a schematic diagram illustrating an exemplary transverse FOV according to some embodiments of the present disclosure. In some embodiments, a detector unit (e.g., the detector unit <NUM>) of a detector ring <NUM> is connected by a coincidence circuit (not shown) of the electronics module <NUM> with a time window to a plurality of opposing detector units in the transverse plane. In some embodiments, the time window is set at <NUM> nanosecond to <NUM> nanoseconds depending on the type of detector. In some embodiments, the detector ring <NUM> has P detector units. In some embodiments, the detector unit <NUM> is in coincidence with Q detector units on the opposite side. In some embodiments, Q is a fraction of P, for example, Q=P/<NUM>, Q=P/<NUM>, Q=2P/<NUM>, etc. Therefore, Q projections are available for the detector unit <NUM>. The Q projections for the detector unit <NUM> form an angle of acceptance in the transverse plane. In some embodiments, similar to the detector unit <NUM>, each detector unit forms an angle of acceptance in the transverse plane, and the angles of acceptance for all detector units in the detector ring <NUM> form the transverse field of view (FOV). In some embodiments, the transverse FOV is an overlapping region formed by the projections for all detector units in the detector ring <NUM>. The larger the number of detector units in multicoincidence with each detector unit, the larger the angle of acceptance and hence the larger transverse FOV for the imaging system <NUM>. In some embodiments, the transverse FOV is determined based on a user input, or a default setting of the imaging system <NUM>. In some embodiments, the transverse FOV is determined based on performance of the imaging system <NUM>, for example, a sensitivity, a spatial resolution, a time resolution, a response time, etc. In some embodiments, the transverse FOV is determined based on the configuration of the detector ring <NUM>, for example, the size of a detector unit, the thickness of a detector unit, the diameter of the detector ring <NUM>, the gap between two adjacent detector units of the detector ring <NUM>, etc. In some embodiments, the transverse FOV relates to the diameter of the detector ring <NUM> and/or the transverse angle of acceptance. In some embodiments, the transverse FOV has a diameter ranging from <NUM> centimeters to <NUM> centimeters.

<FIG> is a schematic diagram illustrating an exemplary axial FOV according to some embodiments of the present disclosure. In some embodiments, a detector unit (e.g., the detector unit A) of the detector assembly <NUM> is connected by a coincidence circuit (not shown) of the electronics module <NUM> with a time window to a plurality of opposite detector units in the axial plane. In some embodiments, the time window is set at <NUM> nanosecond to <NUM> nanoseconds depending on the type of detector. In some embodiments, the detector assembly <NUM> has E rings of detector units. In some embodiments, the detector unit A is in coincidence with F detector units in the axial direction on the opposite side. In some embodiments, F is a fraction of E, for example, F=E/<NUM>, F=E/<NUM>, F=2E/<NUM>, F=E, etc. Therefore, F projections are available for the detector unit A. Each of the F projections forms an angle relative to the transverse plane <NUM>. The maximum angle (e.g., α) for the F projections constitutes the axial angle of acceptance. The detector unit A and the detector unit B (or, the detector unit A' and the detector unit B') are positioned on opposite sides of the transverse plane <NUM>. Both the detector unit A and the detector unit B (or, the detector unit A' and the detector unit B') form the axial angle of acceptance. Then, the distance between the detector unit A and the detector unit B (or, the detector unit A' and the detector unit B') forms the axial FOV. In some embodiments, the axial FOV is determined based on a user input, or a default setting of the imaging system <NUM>. In some embodiments, the axial FOV is determined based on the performance of the imaging system <NUM>, for example, a sensitivity, a spatial resolution, a time resolution, a response time, etc. In some embodiments, the axial FOV is determined based on the configuration of the detector assembly <NUM>, for example, the size of a detector unit, the axial thickness of a detector ring, the diameter of the detector ring, the interval between two adjacent detector rings, the axial length of the detector assembly <NUM>, etc. In some embodiments, the axial FOV is less than <NUM> meters. In some embodiments, the axial FOV is larger than <NUM> meters, for example, from <NUM> meters to <NUM> meters, etc. In some embodiments, for a large axial FOV (e.g., <NUM> meters to <NUM> meters), the time window of the coincidence circuit is relatively large (e.g., <NUM> nanoseconds, <NUM> nanoseconds, <NUM> nanoseconds, etc.). In some embodiments, for a large axial FOV (e.g., <NUM> meters to <NUM> meters), different detector units have different time windows. For example, detector units (e.g., the detector unit A and the detector unit B') far from the transverse plane <NUM> have a time window of <NUM> nanoseconds, while detector units (e.g., the detector unit C and the detector unit C') close to the transverse plane <NUM> have a time window of 1nanosecond.

<FIG> is a schematic diagram illustrating a relationship between an exemplary detector assembly <NUM> and the sensitivity of the imaging system <NUM> according to some embodiments of the present disclosure. As shown in <FIG>, the imaging system <NUM> includes eight PET units (e.g., the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM>, the PET unit <NUM> as illustrated in <FIG>). In some embodiments, the length of the axial FOV of each of the eight PET units is <NUM> meters. It should be noted that the number of the axial FOV of each of the eight PET units is merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. The triangle regions (e.g., <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>) refer to sensitivities relating to coincidence events detected by one of the PET units. For example, the triangle region <NUM>-<NUM> refers to sensitivities relating to coincidence events detected by the PET unit <NUM>. The diamond regions (e.g., <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, etc.) indicate different sensitivities relating to cross coincidence events detected by different PET units (e.g., two adjacent PET units). For example, the diamond region <NUM>-<NUM> (also <NUM>-<NUM>) refers to sensitivities relating to cross coincidence events detected by the PET unit <NUM> and the PET unit <NUM>. The lines of response (LOR) between the PET units are set by a user via the terminal(s) <NUM>. As used herein, the line of response (LOR) refers to a line between two scintillators that may detect a coincidence event. The inclination angle of a coincidence line relates to a sensitivity of the imaging system <NUM>. The greater the inclination angle of a coincidence line is, the higher the sensitivity of the imaging system <NUM> is. In some embodiments, the inclination angle of a line of response is defined by an offset of the line of response. In some embodiments, if coincidence events detected by two adjacent PET units need to be processed, the offset of the line of response is equal to <NUM>, and the sensitivity of the imaging system <NUM> relates to the accumulation of sensitivities in the triangle regions (e.g., <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>). The greater the offset is, the higher the sensitivity of the imaging system <NUM> is.

<FIG> is a schematic diagram illustrating an exemplary cooling assembly <NUM> according to some embodiments of the present disclosure. The cooling assembly <NUM> uses a cooling medium that is gas, liquid, or the like, or a combination thereof. For illustration purposes and not intended to limit the scope of the present disclosure, the cooling assembly <NUM> of <FIG> and <FIG> use a gaseous cooling medium, or referred to as a cooling gas for brevity. The cooling assembly <NUM> produces, transfers, delivers, channels, or circulates cooling gas to the scanner <NUM> to absorb heat produced by the scanner <NUM> during an imaging procedure. In some embodiments, the cooling assembly <NUM> is entirely integrated into the scanner <NUM> and becomes a part of the scanner <NUM>. In some embodiments, the cooling assembly <NUM> is partially integrated into the scanner <NUM> and associated with the scanner <NUM>. For example, a portion of the cooling assembly <NUM> (e.g., the chamber <NUM>) is integrated into the scanner <NUM>, while another portion of the cooling assembly <NUM> (e.g., the refrigerator <NUM>) is configured outside the scanner <NUM>. The cooling assembly <NUM> allows the scanner <NUM> to maintain a suitable and/or stable working temperature. In some embodiments, the cooling assembly <NUM> controls the temperature at one or more target locations of the scanner <NUM>. The target location includes the detector assembly <NUM>, the electronics module <NUM>, and/or any other component that may generate heat. As illustrated in <FIG>, the cooling assembly <NUM> includes a refrigerator <NUM> and a chamber <NUM>.

The refrigerator <NUM> processes or cools down the cooling medium. The cooling medium is introduced into the chamber <NUM> to absorb heat from the scanner <NUM> (e.g., the detector assembly <NUM>). Exemplary gaseous cooling medium includes an inert gas, nitrogen, carbon dioxide, air, or the like, or a combination thereof. In some embodiments, the refrigerator <NUM> cools heated cooling medium that has absorbed heat from the scanner <NUM>.

As illustrated, the refrigerator <NUM> includes a compressor <NUM> and an air blower <NUM>. The compressor <NUM> increases the pressure of a coolant, then, the coolant is condensed, and the heat in the coolant is dissipated through a heat sink. In some embodiments, the condensed coolant is evaporated by an evaporator (not shown), and absorbs heat in the cooling gas, and then the heated cooling gas is cooled down for reuse. The cooling gas is driven by the air blower <NUM> and flow in the cooling assembly <NUM> cyclically. In some embodiments, the compressor <NUM> includes a centrifugal compressor, an axial compressor, a reciprocating compressor, a rotary compressor, or the like, or a combination thereof. For example, the axial compressor includes a diagonal or mixed-flow compressor, an axial-flow compressor, etc. The reciprocating compressor includes a diagram compressor, a double acting compressor, a single acting compressor, etc. The rotary compressor includes a rotary vane compressor, a scroll compressor, a rotary screw compressor, an ionic liquid piston compressor, a lobe compressor, a liquid ring compressor, etc. The air blower <NUM> (also referred to as fan) drives the cooling gas to flow in the chamber <NUM>. In some embodiments, the air blower <NUM> includes a mechanical bearing blower, a magnetic suspension blower, a gas suspension bearing blower, etc. In some embodiments, one or more parameters relating to a cooling process, such as a flow rate of the cooling gas, are determined and/or adjusted by the air blower <NUM>. For example, the flow rate of the cooling gas is regulated through the variation of the rotation speed of the air blower <NUM>.

The chamber <NUM> is configured to channel the cooling gas to one or more target locations (e.g., around the detector assembly <NUM>) of the scanner <NUM>. As illustrated in <FIG>, the chamber <NUM> includes one or more air chambers <NUM>, a compressor chamber <NUM>, and one or more chilling chambers <NUM>. The compressor chamber <NUM> is configured to receive the cooling gas processed by the compressor <NUM>. In some embodiments, the compressor chamber <NUM> houses the compressor <NUM>. In some embodiments, the compressor chamber <NUM> is connected to the compressor <NUM> via, for example, a pipe. The chilling chamber(s) <NUM> are located around the heating components (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.) to cool the heating components.

The air chamber <NUM> provides a location for gas communication between the compressor chamber <NUM> and one or more chilling chambers <NUM>. For example, the air chamber <NUM> includes one or more inlet chambers connecting the compressor chamber <NUM> and the chilling chamber(s) <NUM>. The cooling gas exiting the compressor <NUM> is driven by the air blower <NUM> to flow from the compressor chamber <NUM> to the chilling chamber(s) <NUM> through the inlet chambers. As another example, the air chamber <NUM> includes one or more outlet chambers connecting the compressor chamber <NUM> and the chilling chamber(s) <NUM>. The gas absorbing heat from the heating components (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.) is driven to flow from the chilling chamber(s) <NUM> to the compressor chamber <NUM> though the outlet chambers.

In some embodiments, the configuration between the detector assembly <NUM> and the chilling chamber(s) <NUM> is various. For example, one detector module of the detector assembly <NUM> is configured to have one chilling chamber <NUM>. As another example, multiple detector modules (e.g., all detector modules) of the detector assembly <NUM> are configured to share one chilling chamber <NUM>. In some embodiments, a first number of detector modules are configured to share one single chilling chamber <NUM>. The first number is higher than <NUM> but lower than the number of the detector modules in the detector assembly <NUM>.

In some embodiments, the configuration between the air chamber <NUM> and the chilling chamber <NUM> is various. For example, one of the chilling chambers <NUM> is configured to have one air chamber <NUM>. As another example, multiple (e.g., all) chilling chambers <NUM> are configured to share one air chamber <NUM>. In some embodiments, a second number of chilling chambers <NUM> are configured to share one single air chamber <NUM>. The second number is higher than <NUM> but lower than the number of the chilling chambers <NUM>.

<FIG> is a schematic diagram illustrating an exemplary air cooling assembly and multiple detector modules according to some embodiments of the present disclosure.

The refrigerator <NUM> provides cooling gas as described in connection with <FIG>. The controller <NUM> controls the refrigerator <NUM>, the chilling chambers <NUM>, inlet chambers, and/or outlet chambers. In some embodiments, the controller <NUM> is integrated in the control module <NUM>. In some embodiments, the controller <NUM> controls a parameter of the cooling gas in the refrigerator <NUM>, the chilling chambers <NUM>, inlet chambers, and/or outlet chambers respectively according to for example, an instruction set by a user via the terminal <NUM>. The parameter of the cooling gas includes a pressure, a temperature, a flow rate of the cooling gas, a rate of heat generation, a cooling load to remove the generated heat, a cooling rate, or the like, or a combination thereof. For example, the controller <NUM> adjusts a pressure of the cooling gas (e.g., a gas pressure) in an inlet chamber (e.g., inlet chamber <NUM>, inlet chamber <NUM>,. , inlet chamber N). As another example, the controller <NUM> controls a flow rate of the cooling gas in one of the multiple inlet chambers and/or the outlet chambers respectively. Furthermore, the parameter of the cooling gas (e.g., the pressure, the temperature, the flow rate, etc.) in the inlet chambers (e.g., inlet chamber <NUM>, inlet chamber <NUM>,. , inlet chamber N) and/or the outlet chambers (e.g., outlet chamber <NUM>, outlet chamber <NUM>,. , outlet chamber N) is different or the same.

In some embodiments, one of the multiple inlet chambers is connected to one of the chilling chambers <NUM>. One of the chilling chambers <NUM> is configured with one of the detector modules (e.g., a detector module <NUM>, a detector module <NUM>,. , a detector module N). A detector module includes one or more detector rings. For example, the detector module <NUM>-<NUM> includes k detector rings. As another example, the detector module <NUM>-<NUM> includes m detector rings. As still another example, the detector module <NUM>-N includes j detector rings. One of the multiple outlet chambers are connected to one of the chilling chambers <NUM>. The cooling gas provided by the refrigerator <NUM> bypasses the multiple inlet chambers and flow to the multiple chilling chambers <NUM>, respectively. The numbers k, m, j and N are integers larger than <NUM>. The numbers k, m, j and N are the same or different.

In some embodiments, the flow rate of the cooling gas delivered to a detector module is controlled based on the rate heat is generated in that detector module. For instance, if the temperature of a detector module increases beyond a threshold, or the temperature of a detector module increases at a rate beyond a threshold, the flow rate of the cooling gas delivered to that detector module is increased. In some embodiments, the delivery of the cooling gas to various heating components is controlled individually. For instance, the flow rates of the cooling gas to various detector modules are different. The flow rate of the cooling gas to a heating component is changed by changing the opening of one or more valves (not shown) configured in the chilling chamber <NUM> and/or the inlet chamber.

It should be noted that the above description of the air cooling assembly in <FIG> and <FIG> is merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations or modifications may be made under the teachings of the present disclosure. For example, the cooling assembly <NUM> further includes one or more components, such as one or more thermal insulation layers. As another example, the cooling assembly <NUM> further includes one or more chambers configured as the cooling gas passage. As still another example, the detector module <NUM> and the detector module <NUM> may be configured with one chilling chamber, also referred to that the chilling chamber <NUM>-<NUM> and the chilling chamber <NUM>-<NUM> are integrated into one chilling chamber. As a further example, the chilling chamber <NUM>-<NUM> and the chilling chamber <NUM>-<NUM> communicate with each other. In some embodiments, the chilling chamber <NUM>-<NUM> and the chilling chamber <NUM>-<NUM> are configured with one inlet chamber and/or one outlet chamber. However, those variations and modifications do not depart from the scope of the present disclosure. More descriptions of the air cooling assembly are found in <CIT>.

<FIG> is a schematic diagram illustrating another exemplary cooling assembly <NUM> according to some embodiments of the present disclosure. The cooling assembly <NUM> uses a cooling medium that is gas, liquid, or the like, or a combination thereof. For illustration purposes and not intended to limit the scope of the present disclosure, the cooling assembly <NUM> of <FIG> and <FIG> uses a liquid cooling medium, or a cooling liquid for brevity. As shown in <FIG>, the cooling assemble <NUM> includes a cooling liquid <NUM>, a valve <NUM>, a pump <NUM>, an inlet/outlet <NUM>, a heat exchanger <NUM>, a liquid distributor <NUM>, and a temperature controller <NUM>. In some embodiments, the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM> are connected to each other via one or more pipes. In some embodiments, the temperature controller <NUM> is connected to the valve <NUM>, the pump <NUM>, the inlet/outlet <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM> via a wireless connection and/or a wired connection.

The cooling liquid <NUM> cools a heating component (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.) by absorbing and/or transferring the heat produced by the heating component. In some embodiments, the cooling liquid <NUM> includes water, oil, polyalkylene glycol (PAG), gutting fluid, nanofluid (e.g., CuO, alumina, titanium, carbon nanotubes, etc.), liquid gas (e.g., CO<NUM>), freon, etc..

The valve <NUM> is configured to control an on/off state of a pipe and/or a flow rate of the cooling liquid. In some embodiments, the valve <NUM> is configured to control the flow velocity and/or the flow rate of the cooling liquid <NUM> from or to the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM>.

The pump <NUM> drives the cooling liquid to flow in the liquid cooling assembly cyclically. In some embodiments, the pump <NUM> includes a positive displacement pump, an impulse pump, a velocity pump, a gravity pump, a steam pump, a valveless pump, a centrifugal pump, or the like, or a combination thereof. For example, the positive displacement pump includes a rotary lobe pump, a progressive cavity pump, a rotary gear pump, a piston pump, a diaphragm pump, a screw pump, a gear pump, a hydraulic pump, a rotary vane pump, a peristaltic pump, a rope pump, a flexible impeller pump, etc. In some embodiments, the pump <NUM> is in fluid communication with the heat exchanger <NUM> via the inlet/outlet <NUM>.

The inlet/outlet <NUM> is connected to the heat exchanger <NUM>. In some embodiments, the liquid cooling assembly includes an inlet and an outlet. In some embodiments, the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM> areconfigured to share the inlet/outlet <NUM>. For example, the cooling liquid <NUM> flows into or discharge from the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM> through the inlet/outlet <NUM>. In some embodiments, each of the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM> has its own inlet/outlet <NUM>.

The heat exchanger <NUM> is configured to transfer heat between the cooling liquid <NUM> and a refrigerant (also refer to as a coolant) including, for example, freon, an azeotropic mixture, a hydrocarbon refrigerant, or the like, or any combination thereof. For example, the cooling liquid <NUM> absorbs heat from a heating component (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.), and flows to the heat exchanger <NUM> driven by the pump <NUM>. The used cooling liquid <NUM> in the heat exchanger <NUM> transfers the heat absorbed from the heating component to the refrigerant. In some embodiments, the refrigerant is separated from the cooling liquid <NUM> by a solid wall to prevent the mixing of the two. In some embodiments, the heat exchanger <NUM> includes a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic wheel heat exchanger, a plate fin heat exchanger, a pillow plate heat exchanger, a fluid heat exchanger, a waste heat recovery unit, a dynamic scraped surface heat exchanger, a phase-change heat exchanger, a direct contact heat exchanger, a microchannel heat exchanger, or the like, or a combination thereof.

The liquid distributor <NUM> distributes the cooling liquid <NUM> to different channels. The channels are configured to transfer the cooling liquid <NUM> to target locations (e.g., around the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.). In some embodiments, the liquid distributor <NUM> controls an amount of the cooling liquid <NUM> distributed to one of the channels. For example, if a portion of the detector assembly <NUM> is at a high temperature, the liquid distributor <NUM> increases the flow rate of the cooling liquid <NUM> to the channel corresponding to the portion of the detector assembly <NUM>. As another example, the liquid distributor <NUM> distributes the cooling liquid <NUM> to different channels equably. In some embodiments, the liquid distributor <NUM> includes various types including, for example, a pass type, a weir type, a pressure type liquid distributor, a spray type, a porous tube type, etc..

The temperature controller <NUM> controls a temperature of the heating component (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.) by controlling one or more modules in the water cooling assembly (e.g., the valve <NUM>, the pump <NUM>, the inlet/outlet <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM>). For example, the temperature controller <NUM> controls the liquid distributor <NUM> to increase the flow rate of the cooling liquid <NUM> to one pipe corresponding to a detector assembly <NUM> to decrease the temperature of the detector assembly <NUM>. As another example, the temperature controller <NUM> controls the pump <NUM> to increase a pressure and/or a flow velocity of the cooling liquid <NUM> to decrease the temperature of the heating component. As still another example, the temperature controller <NUM> control the heat exchanger <NUM> to decrease the temperature of the cooling liquid <NUM> to decrease the temperature of the heating component. In some embodiments, the temperature controller <NUM> includes one or more temperature sensors connected with a target location (e.g., the detector assembly <NUM>, the electronics module <NUM> of the scanner <NUM>, etc.) to monitor the temperature relating to the target location.

<FIG> is a schematic diagram illustrating an exemplary water cooling assembly and multiple detector modules according to some embodiments of the present disclosure. As shown in <FIG>, the liquid distributor <NUM> distributes the cooling liquid <NUM> into multiple pipes. The multiple pipes are in fluid communication with different target locations around the multiple detector modules (e.g., a first detector module <NUM>, a second detector module <NUM>, a third detector module <NUM>, a fourth detector module <NUM>, a fifth detector module <NUM>, a sixth detector module <NUM>, a seventh detector module <NUM>, an eighth detector module <NUM>, etc.). One of the multiple pipes are coupled to one detector module. In some embodiments, a pipe clings to one or more surfaces of a detector module, and thus, the cooling liquid <NUM> flowing in the pipe absorbs heat from the detector module.

<FIG> is a schematic diagram illustrating another exemplary water cooling assembly and multiple detector modules according to some embodiments of the present disclosure. As shown in <FIG>, the water cooling assembly includes a water cooling chiller <NUM> and at least two water distributors (e.g., a water distributor <NUM>-<NUM> and a water distributor <NUM>-<NUM>). The water cooling chiller <NUM> includes a pump, an inlet/outlet, a heat exchanger, and/or a temperature controller <NUM> as described in connection with <FIG>. The water distributer <NUM>-<NUM> is configured to distribute a cooling liquid (e.g., water) of a lower temperature, according to a specific flow rate, to multiple target regions around multiple detector modules. A detector module includes one or more detector rings. In some embodiments, a detector module refers to a PET unit as illustrated in <FIG>. As shown in <FIG>, the water distributer <NUM>-<NUM> distributes cooling liquid (e.g., water) to a first PET unit <NUM>-<NUM>, a second PET unit <NUM>-<NUM>, a third PET unit <NUM>-<NUM>, a fourth PET unit <NUM>-<NUM>, a fifth PET unit <NUM>-<NUM>, a sixth PET unit <NUM>-<NUM>, a seventh PET unit <NUM>-<NUM>, an eighth PET unit <NUM>-<NUM>, etc. It should be noted that the number of PET units is merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. The water distributor <NUM>-<NUM> is configured to converge the cooling liquid which have absorbed heat from the target regions around the multiple detector modules and transfer the heated liquid to the water cooling chiller <NUM>.

In some embodiments, the water cooling chiller <NUM> cools, within a period of time, a specific amount of cooling liquid to a lower temperature by a heat exchanger (e.g., the heat exchanger <NUM>). A pump drives the cooling liquid to flow to the water distributor <NUM>-<NUM> through an inlet. The water distributor <NUM>-<NUM> distributes the specific amount of cooling liquid at the lower temperature into multiple portions and transfer the multiple portions of cooling liquid to multiple target regions around the multiple detector modules. The cooling liquid of the lower temperature absorbs heat generated by the detector modules or other heating components around the target regions (e.g., the electronics assembly <NUM>). The used cooling liquid is at a higher temperature after absorbing heat. Then the used cooling liquid of a higher temperature is transferred to and mixed at the water distributor <NUM>-<NUM>. The mixed used cooling liquid is transferred back to the heat exchanger in the water cooling chiller <NUM>. Then in the heat exchanger, the used cooling liquid at the higher temperature is cooled to provide a cooled cooling liquid of a lower temperature for reuse. The water cooling assembly performs the above operations cyclically to cool the scanner <NUM>. More descriptions of the water cooling assembly in the scanner <NUM> are found in <CIT>.

It should be noted that the above description of the diagram in <FIG> is merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations or modifications may be made under the teachings of the present disclosure. For example, the valve <NUM> and/or the inlet/outlet <NUM> is integrated into other modules in the cooling assembly <NUM>, for example, the pump <NUM>, the heat exchanger <NUM>, and/or the liquid distributor <NUM>. As another example, the cooling assembly <NUM> includes one or more pipes for transferring the cooling liquid <NUM> to one or more target locations. As still another example, one or more detector modules (e.g., PET unit) may be coupled to the same pipe. As a further example, the number of PET units are any integer larger than <NUM>. However, those variations and modifications do not depart the scope of the present disclosure.

<FIG> is a schematic diagram illustrating an exemplary processing engine <NUM> according to some embodiments of the present disclosure. The processing engine <NUM> includes an acquisition module <NUM>, a control module <NUM>, a processing module <NUM>, a storage module <NUM>. At least a portion of the processing engine <NUM> is implemented on a computing device.

The acquisition module <NUM> acquires data or signal. In some embodiments, the acquisition module <NUM> acquires the data from the scanner <NUM>, the storage <NUM>, the terminal(s) <NUM>, and/or an external data source (not shown). In some embodiments, the data includes image data (e.g., projection data), instructions, or the like, or a combination thereof. For example, the image data is generated based on the radiation rays (e.g., γ rays) that emit from a subject positioned in the detection region <NUM>. In some embodiments, the image data includes information relating to energy of the radiation rays (e.g., γ rays), information relating to an interaction position of the radiation rays (e.g., γ rays) in the detector assembly <NUM>, and/or information relating to an interaction time of the radiation rays (e.g., γ rays) in the detector assembly <NUM>. The instructions are executed by the processor(s) of the processing engine <NUM> to perform exemplary methods described in this disclosure. In some embodiments, the acquired data is transmitted to the storage module <NUM> for storing.

The control module <NUM> generates one or more control parameters for controlling the acquisition module <NUM>, the processing module <NUM>, the storage module <NUM>, the table <NUM>, the detector assembly <NUM>, the cooling assembly <NUM>, the electronics module <NUM>, or the like, or any combination thereof. For example, the control module <NUM> controls the acquisition module <NUM> as to whether to acquire image data. As another example, the control module <NUM> controls the electronics module <NUM> as to whether to acquire an electrical signal, the time when an electrical signal acquisition may occur, or the frequency to acquire an electrical signal. As still another example, the control module <NUM> controls the operation of the scanner <NUM> (e.g., the detector assembly <NUM>, table <NUM>, electronics module <NUM>, cooling assembly <NUM>, etc.). As a further example, the control module <NUM> controls the processing module <NUM> to select different algorithms to process the data acquired by the acquisition module <NUM> or electrical signal acquired by the electronics module <NUM>. In some embodiments, the control module <NUM> receives a real-time or a predetermined instruction provided by a user (e.g., a doctor, a technician, etc.) to control one or more operations of the scanner <NUM>, the acquisition module <NUM>, and/or the processing module <NUM>. For example, the control module <NUM> adjusts the acquisition module <NUM> and/or the processing module <NUM> to generate images of a subject according to the real-time or predetermined instruction. In some embodiments, the control module <NUM> communicates with other modules in the PET imaging system <NUM> for exchanging information and/or data.

The processing module <NUM> processes information provided by various modules of the processing engine <NUM>. The processing module <NUM> processes data acquired by the acquisition module <NUM>, signal acquired by the electronics module <NUM>, data retrieved from the storage module <NUM>, etc. In some embodiments, the processing module <NUM> reconstructs one or more images based on the data or signal according to a reconstruction technique, generates reports including the one or more images and/or other related information, and/or performs any other function for image reconstruction. The reconstruction technique includes an iterative reconstruction algorithm (e.g., a maximum likelihood expectation maximization (MLEM) algorithm, an ordered subset expectation maximization (OSEM) algorithm), a filtered back projection (FBP) algorithm, a 3D reconstruction algorithm, or the like, or any combination thereof. In some embodiments, the processing module <NUM> corrects the data or reconstructed image based on one or more correction techniques. The correction technique includes a random correction, a scatter correction, an attenuation correction, a dead time correction, normalization, or the like, or any combination thereof. In some embodiments, the processing module <NUM> performs one or more corrections in image reconstruction.

The storage module <NUM> stores data or signal, control parameter(s), processed data or signal, or the like, or a combination thereof. In some embodiments, the storage module <NUM> stores one or more programs and/or instructions that may be executed by the processor(s) of the processing engine <NUM> to perform exemplary methods described in this disclosure. For example, the storage module <NUM> stores program(s) and/or instruction(s) that may be executed by the processor(s) of the processing engine <NUM> to acquire data or signal, reconstructs an image based on the data or signal, and/or displays any intermediate result or a resultant image.

In some embodiments, one or more modules illustrated in <FIG> are implemented in at least part of the exemplary PET imaging system <NUM> as illustrated in <FIG>. For example, the acquisition module <NUM>, the control module <NUM>, the storage module <NUM>, and/or the processing module <NUM> are integrated into a console (not shown). Via the console, a user sets the parameters for scanning a subject, acquiring data or signal, etc. In some embodiments, the console is implemented via the processing engine <NUM> and/or an external device (not shown).

<FIG> is a flowchart illustrating an exemplary process <NUM> for PET imaging according to some embodiments of the present disclosure. In some embodiments, one or more operations of process <NUM> illustrated in <FIG> for PET imaging are implemented in the PET imaging system <NUM> illustrated in <FIG>. For example, the process <NUM> illustrated in <FIG> is stored in the storage <NUM> in the form of instructions, and invoked and/or executed by the processing engine <NUM> (e.g., the processor of a computing device). As another example, a portion of the process <NUM> is implemented on the scanner <NUM>.

In <NUM>, a scan is initialized. In some embodiments, operation <NUM> is performed by the control module <NUM>. In some embodiments, the initialization is performed based on a scanning protocol, a user input, a default setting of the imaging system <NUM>, or the like, or any combination thereof. The scanning protocol includes a scan region of an object, a dose of a tracer isotope, an uptake period of the tracer isotope, or the like, or any combination thereof.

In some embodiments, the detector assembly <NUM> is initialized in <NUM>. In some embodiments, the scanner <NUM> has a large axial FOV (e.g., between <NUM> and <NUM>), and the detector assembly <NUM> has an axial length larger than or equal to the axial FOV. As the number of detectors of the scanner <NUM> with a large axial FOV is larger than that of a scanner with a normal axial FOV (e.g., from <NUM> meters to <NUM> meters, from <NUM> meters to <NUM> meters, etc.), the alignment and function of the detectors are significant for achieving a good performance. In some embodiments, a validity test of the detector assembly <NUM> is performed in <NUM>. For example, whether the detectors are aligned in the axial direction is tested. As another example, whether the detectors in the axial FOV range are functional is tested. With large axial FOV, more radiation rays are detected, and the complexity for identifying which crystal has a radiation ray interaction is increased. With more detectors, spatial distortions in crystal identification are intensified. In some embodiments, positions of the detectors (or crystals) is calibrated based on a position calibration algorithm, for example, a position calibration algorithm based on a crystal position look-up table. The crystal position look-up table maps the inaccurate interaction location to the exact interaction crystal position. The crystal position look-up table is generated based on one or more algorithms including, for example, a principal component analysis (PCA)-based algorithm, a hierarchical fusion algorithm, a region segmentation based algorithm, or the like, or any combination thereof. In some embodiments, the crystal position look-up table is generated or obtained in <NUM>. For example, the crystal position look-up table is acquired from the storage <NUM>, the storage module <NUM>, or an external data source (not shown). More descriptions regarding a crystal position look-up table are found in, for example, U. Patent Publication No.<CIT>.

In some embodiments, the detector assembly <NUM> is initialized to "enable" a portion of detectors while "disabling" the rest of detectors. For example, if the head of the object is to be scanned, a portion of detectors in a certain axial range (e.g., <NUM> centimeters) is "enabled" to detect radiation rays emitted from the head, while the rest of detectors may not detect radiation rays even though there may be radiation rays reaching the rest of detectors. As another example, if the whole body of the object is to be scanned, a plurality of detectors surrounding the whole body (e.g., the detectors along the length of an axial FOV of <NUM> meters) are selected to detect signals. In some embodiments, different detectors of the detector assembly <NUM> is selected to detect signals at different times. The selection of detectors and the time to start scanning are initialized in <NUM> based on the scanning protocol. For example, a first portion of detectors is "enabled" to scan the head at time T<NUM>, while a second portion of detectors is "enabled" to scan the feet at time T<NUM>.

In some embodiments, the cooling assembly <NUM> is initialized in <NUM>. In some embodiments, a flow rate (or a flux) of the cooling air or coolant is initialized. In some embodiments, which air chamber (or which valve) is to be opened may be initialized. As the main function of the cooling assembly <NUM> is cooling the detectors that generate heat, the cooling assembly <NUM> may be initialized based on the initialization of the detector assembly <NUM>. For example, if a first portion of detectors are to be "enabled" to work at time T<NUM>, the air chamber (or valve) that introduce the cooling air (or coolant) to the surface of the first portion of detectors is opened at time T<NUM> or earlier than the time T<NUM>, or the flow rate (or flux) of the cooling air or coolant that pass through the first portion of detectors may be increased at time T<NUM>.

In some embodiments, one or more parameters are initialized in <NUM>. The parameters include scanning parameters, reconstruction parameters, etc. The scanning parameters include a scan start time, a scan duration, a signal acquisition frequency, a coincidence time window, an offset (as illustrated in <FIG>), an energy threshold, etc. In some embodiments, the coincidence time window relates to the offset. The larger the offset is, the larger the coincidence time window is. In some embodiments, a variable coincidence time window is set based on the offset. For example, a relatively small coincidence time window is set if the offset is <NUM>, while a relatively large coincidence time window is set if the offset is larger than <NUM>. The reconstruction parameters include an image resolution, a filter, one or more parameters used in a reconstruction technique (e.g., an iteration time in iterative reconstruction, a coefficient, a threshold, etc.), or the like, or any combination thereof. In some embodiments, the parameters are initialized based on a user input, a system default, or the like, or any combination thereof.

In some embodiments, a desired position of the table <NUM> is initialized in <NUM>. The desired position is in an FOV (e.g., the transverse FOV and the axial FOV) of the detection region <NUM>. In some embodiments, the desired position of the table <NUM> is initialized based on a scanning protocol, a user input, a system default, or the like, or any combination thereof. For example, the desired position of the table <NUM> is determined based on a scan region of the subject. In some embodiments, the desired position of the table <NUM> is associated with the "enabled" detectors. For example, the desired position of the table <NUM> is within a special region surrounded by the "enabled" detectors. In some embodiments, the subject positioned on the table <NUM> is moved to the desired position. The table <NUM> is moved in the axial direction, a vertical position, and a horizontal direction perpendicular to the axial direction and the vertical position.

In <NUM>, electrical signals generated through the scan are collected. In some embodiments, operation <NUM> is performed by the electronics module <NUM>. A plurality of radiation rays are received using the detector assembly <NUM>. The radiation rays are γ rays that emit from the subject positioned in the detection region <NUM>. Before scanning, a radioactive tracer isotope is injected into the subject. One or more atoms of the tracer isotope are chemically incorporated into one or more biologically active molecules in the subject. The active molecules become concentrated in one or more tissues of interest within the subject. The tracer isotope undergoes positron emission decay and emits one or more positrons. A positron travels a short distance (e.g., about <NUM>) within a tissue of interest, loses kinetic energy and interacts with an electron of the subject. The positron and the electron annihilate and produce a pair of annihilation photons. The pair of annihilation photons (or radiation rays) move in approximately opposite directions. A plurality of radiation rays reach the detector assembly <NUM> and are received by the scintillators (e.g., the scintillator array <NUM>) in the detector assembly <NUM>. Then, the scintillators absorb the energy of the radiation ray (e.g., γ ray) photons, and convert the absorbed energy into light. A plurality of electrical signals are generated based on the absorbed radiation rays by the photosensors that couple to the scintillators.

In some embodiments, an interaction position and/or an interaction time of a received radiation ray aredetermined by the electronics module <NUM>. The interaction position is used to identify which scintillator within the scintillators of the detector assembly <NUM> has a radiation ray interaction with the received radiation ray, and/or a depth of interaction of the received radiation ray in the identified scintillator. The interaction position is determined based on the energy of the electrical signals and one or more algorithms including, for example, a centroid algorithm, the Anger-Logic algorithm, a maximum likelihood estimation algorithm, or a localization algorithm based on an artificial neutral network model, or the like, or any combination thereof. In some embodiments, the interaction time is determined based on the energy and/or collection time of the electrical signals. In some embodiments, the interaction time is determined based on a lower limit detection (LLD) circuit (or a constant fraction discriminator (CFD) circuit) and a time-to-digital converter (TDC). In some embodiments, the interaction time is corrected based on the depth of interaction and a time correction technique. The time correction technique includes a dead time correction, a time walk correction, etc..

In <NUM>, image data is obtained based on the electrical signals collected in <NUM>. In some embodiments, operation <NUM> is performed by the electronics module <NUM>. In some embodiments, the image data includes data relating to one or more lines of response (LOR). In some embodiments, one or more coincidence events are determined based on the interaction positions and the interaction times of a plurality of received radiation rays. If two radiation rays are received and interact with two scintillators within a certain time window (e.g., <NUM> nanosecond, <NUM> nanoseconds, <NUM> nanoseconds, <NUM> nanoseconds, <NUM> nanoseconds, etc.), the two radiation rays are determined to come from the same annihilation, and regarded as a coincidence event. In some embodiments, the coincidence event is determined by a coincidence circuit of the electronics module <NUM>. The coincidence event is assigned to a line of response (LOR) joining the two relevant scintillators that detect the coincidence event. The coincidence events that are assigned to the same line of response (LOR) are projected and image data is generated. In some embodiments, the image data is stored as a sinogram in the storage <NUM>, the storage module <NUM>, an external data source, etc. In some embodiments, the image data is acquired by the acquisition module <NUM> from the storage <NUM>, the storage module <NUM>, an external data source, etc..

In <NUM>, an image is generated based on the image data obtained in <NUM>. In some embodiments, operation <NUM> is performed by the processing module <NUM>. In some embodiments, the image data is processed to generate an image. The image data is processed based on one or more algorithms including, for example, denoising, a reconstruction algorithm, a correction algorithm, etc. In some embodiments, the reconstruction algorithm includes an iterative reconstruction algorithm (e.g., a maximum likelihood expectation maximization (MLEM) algorithm, an ordered subset expectation maximization (OSEM) algorithm), a filtered back projection (FBP) algorithm, a 3D reconstruction algorithm, or the like, or any combination thereof. In some embodiments, the correction algorithm includes a random correction, a scatter correction, an attenuation correction, a dead time correction, normalization, or the like, or any combination thereof. A reconstructed image shows a tracer distribution within the scanned subject. In some embodiments, a whole body image is generated based on the electrical signals generated by a large axial FOV scanner (e.g., the scanner <NUM>). In some embodiments, mechanical installation error (e.g., a deviation of the centers of two imaging units as described in <FIG>) is corrected in image reconstruction.

In <NUM>, the image generated in <NUM> is outputted. In some embodiments, operation <NUM> is performed by the control module <NUM>. In some embodiments, the image is outputted to the storage module <NUM>, the storage <NUM>, an external data source, etc. for storing. In some embodiments, the image is outputted to the terminal(s) <NUM> for displaying.

It should be noted that the above description of the process <NUM> is merely provided for the purpose of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be made to the process <NUM> under the teachings of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, an image segmentation operation may be added after operation <NUM>.

Having thus described the basic concepts, it may be rather apparent to those skilled in the art after reading this detailed disclosure that the foregoing detailed disclosure is intended to be presented by way of example only and is not limiting. Various alterations, improvements, and modifications may occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested by this disclosure, and are within the scope of the exemplary embodiments of this disclosure.

Furthermore, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claimed processes and methods to any order except as may be specified in the claims. Although the above disclosure discusses through various examples what is currently considered to be a variety of useful embodiments of the disclosure, it is to be understood that such detail is solely for that purpose, and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover modifications and equivalent arrangements that are within the scope of the disclosed embodiments. For example, although the implementation of various components described above may be embodied in a hardware device, it may also be implemented as a software only solution, for example, an installation on an existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description of embodiments of the present disclosure, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the various inventive embodiments. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, inventive embodiments lie in less than all features of a single foregoing disclosed embodiment.

Claim 1:
A system for imaging, comprising:
a supporting assembly (<NUM>, <NUM>) comprising a detection region (<NUM>) to accommodate a subject; and
a detector assembly (<NUM>, <NUM>) surrounding the detection region (<NUM>), the detector assembly (<NUM>, <NUM>) being configured to detect radiation rays emitted from the subject located within the detection region (<NUM>), the detector assembly (<NUM>, <NUM>) including a plurality of detector rings, each detector ring comprising a scintillator array (<NUM>) and a plurality of photosensors, the plurality of detector rings being arranged on the supporting assembly (<NUM>, <NUM>) in an axial direction of the supporting assembly (<NUM>, <NUM>) to form an axial field of view (FOV) having a length no less than <NUM> meters, characterised in that
the detector assembly (<NUM>, <NUM>) includes N detector modules, each of which comprises a portion of the plurality of detector rings,
the supporting assembly (<NUM>, <NUM>) includes N supporting modules, and
the N detector modules and the N supporting modules are configured as N imaging units, each of which comprises at least one detector module of the N detector modules and at least one supporting module of the N supporting module, and at least one of the N imaging units is detachable from the system.