Patent Description:
Medical imaging systems may include a Positron Emission Tomography (PET) system for medical diagnosis or treatment. An object, such as a phantom, may be scanned to obtain PET data. During a performance test and a correction of the PET system, the phantom may be acquired to irradiate all detector units in the detector. For a PET system with a relatively long axial length (e.g., <NUM> meters), a plurality of phantoms may be used to perform the PET scan, based on which a PET image may be reconstructed. The inhomogeneity of the plurality of phantoms may introduce noise to the PET image. There is a need for a system and method to solve the problem. <CIT> discloses apparatus and methods for simulating a sheet source with a line source for determining normalization coefficients for the detectors in positron emission tomography (PET) scanners and single photon emission computed tomography (SPECT) scanners. A line source, oriented perpendicular to the axis of a scanner gantry, is moved along the axis while the detectors are stationary and positioned substantially parallel to the plane in which the source moves. <CIT>discloses a normalization apparatus and method for a PET scanner with panel detectors for obtaining an estimate of a normalization array, for correction for count rate effects on the normalization array, and for measurement of the relation between the normalization array and the count rate.

In a first aspect of the present disclosure, a method for medical imaging is provided. The method may include one or more of the following operations. A phantom may be moved along an axis of a scanner to a plurality of phantom positions. A first set of PET data relating to the phantom at the plurality of phantom positions may be acquired, by a scanner of the imaging device. The length of an axis of the phantom may be shorter than the length of an axis of the scanner, and at least one of the plurality of phantom positions may be inside a bore of the scanner. The first set of PET data may be stored as an electrical file.

In some embodiments, the plurality of phantom positions may be determined based on a scanning parameter of the scanner and a parameter of the phantom.

In some embodiments, the plurality of phantom positions may be determined based on at least one of scan time of the scanner, the length of the axis of the scanner, phantom weight and the length of the axis of the phantom.

In some embodiments, a PET image may be reconstructed at least based on the first set of PET data.

In some embodiments, a second set of PET data may be extracted from the first set of PET data based on the plurality of phantom positions of the phantom. The second set of PET data may correspond to one or more coincidence events of the phantom. A first set of attenuation data for the phantom may be acquired. The first set of attenuation data may correspond to part of the axis of the scanner. A second set of attenuation data for the phantom corresponding to the axis of the scanner may be determined based on the plurality of phantom positions and the first set of attenuation data. The PET image may be reconstructed based on the second set of PET data and the second set of attenuation data.

In some embodiments, calibration data may be acquired. The PET image may be corrected based on the plurality of phantom positions and the calibration data.

In some embodiments, statistic data of phantom position may be generated by normalizing the plurality of phantom positions. Statistic data of nuclide decay may be generated by normalizing nuclide decay corresponding to the axis of the scanner. The PET image may be corrected based on the statistic data of phantom position and the statistic data of nuclide decay.

In some embodiments, the phantom may be placed on a bed, and the motion controller may be configured to move the bed to drive the phantom to the plurality of phantom positions.

In a second aspect of the present disclosure, a system for medical imaging is provided. The system may include a bed configured to support a phantom, a scanner configured to detect coincidence events related to the phantom, and a motion controller configured to move the phantom along the scanner to a plurality of phantom positions. The system may include at least one storage medium and at least one processor. The at least one storage medium may include a set of instructions. The at least one processor may be configured to communicate with the at least one storage medium, wherein when executing the set of instructions, the system is configured to perform one or more of the following operations. A first set of PET data relating to a phantom at the plurality of phantom positions may be acquired, by the scanner of the imaging device. The length of an axis of the phantom may be shorter than the length of an axis of the scanner, and at least one of the plurality of phantom positions may be inside a bore of the scanner. The first set of PET data may be stored as an electrical file.

In some embodiments, the motion controller may be further configured to move the bed to drive the phantom to the plurality of phantom positions.

In some embodiments, the motion controller may include a first motion controller. The first motion controller may include a first moving mechanism and a second moving mechanism. The first moving mechanism may be configured to move the bed in a first direction or a second direction. The second moving mechanism may be configured to move the phantom in a third direction. The third direction may be perpendicular to the first direction and the second direction.

In some embodiments, the second moving mechanism may include a support plate, a first rotating wheel and a second rotating wheel, a first driver, and a transmission belt. The first rotating wheel and the second rotating wheel may be disposed at two ends of the support plate. The first driver may be connected to the first rotating wheel and the second rotating wheel. The transmission belt may encompass the first rotating wheel and the second rotating wheel. The transmission belt may extend in the third direction, and may be connected to the phantom.

In some embodiments, the second moving mechanism may include a support plate, a screw shaft, a second drive, and a support base. The screw shaft may be disposed on the support plate. The screw shaft may extend in the third direction. The second driver may be connected to an end of the screw shaft. The support base attached to the screw shaft. The support base may be connected to the phantom.

In some embodiments, the second moving mechanism may further include a guiding mechanism, and the phantom may be connected to and may move along the guiding mechanism.

In some embodiments, the second moving mechanism may further include a shield configured to shield radiation from the phantom.

In some embodiments, the motion controller may include a second motion controller. The second motion controller may include a moving mechanism. The moving mechanism may include a screw shaft, a slider block, and a shield. The screw shaft may extend along the first direction. An end of the screw shaft may be connected to a first driver. The slider block may be attached to the screw shaft. The slider block may be connected to the phantom. The shield may be configured to accommodate the screw shaft, the slider block and the phantom.

In some embodiments, the second motion controller may further include a rotation shaft, a second driver and a rotation arm. The second driver may be mounted on the slider block and may be connected to an end of the rotation shaft. The rotation arm may be configured to rotate the phantom under a force supplied by the rotation shaft.

In some embodiments, the shield may include a first shield comprising a first groove. The first groove may extend along the first direction, and the screw shaft may be disposed inside the first groove.

In some embodiments, the first groove may include a guiding mechanism. The slider block may be configured to move along the guiding mechanism.

In some embodiments, the shield may further include a second shield. A surface of the second field facing the phantom may include a second groove configured to provide a moving passage for the phantom. The second groove may extend in the first direction.

In some embodiments, the system may further include a third groove configured to accommodate the phantom. The third groove may be on a different plane from the second groove, and may extend in the first direction.

In some embodiments, the third groove may include two closed ends.

In a third aspect of the present disclosure, a non-transitory computer readable medium is provided. The non-transitory computer readable medium may include executable instructions that, when executed by at least one processor, cause the at least one processor to effectuate a method. The method may include one or more of the following operations. A first set of PET data relating to a phantom at a plurality of phantom positions may be acquired, by a scanner of the imaging device. The length of an axis of the phantom may be shorter than the length of an axis of the scanner, and at least one of the plurality of phantom positions may be inside a bore of the scanner. The first set of PET data may be stored as an electrical file.

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, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the present disclosure. 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 descending 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.

Provided herein is a method and system for calibrating an imaging system (e.g., a PET system) and/or generating an image (e.g., a PET image). The present disclosure intends to calibrate the imaging system and/or generate the image with a phantom while being placed at a plurality of phantom positions. By placing the phantom in the plurality of phantom positions at a plurality of time nodes, which may imitate a plurality of phantoms being disposed at the plurality of phantom positions at a same time node, radiation related to the phantom may be utilized to calibrate the imaging system and/or generate the PET image, while sparing noise that may be introduced due to the inhomogeneity of the plurality of phantoms.

The term "image" used in this disclosure may refer to a 2D image, a 3D image, a 4D image, and/or any related data (e.g., PET data, radiation data corresponding to the PET data). 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 the guidance of the present disclosure.

The term "radiation" used herein may include a particle radiation, a photon radiation, or the like, or any combination thereof. The particle may include a positron, a neutron, a proton, an electron, a µ-meson, a heavy ion, or the like, or any combination thereof. The photon may include a gamma photon, a beta photon, an X-ray photon, or the like, or any combination thereof. Those variations, changes, and/or modifications do not depart from the scope of the present disclosure.

<FIG> is a schematic diagram illustrating an exemplary PET system <NUM> according to some embodiments of the present disclosure. As shown, the PET system <NUM> may include a PET scanner <NUM>, a network <NUM>, one or more terminals <NUM>, a processing engine <NUM>, a storage <NUM>, and a motion controller <NUM>.

The PET scanner <NUM> may include a gantry <NUM>, a bed <NUM> (or referred to as a scanning table <NUM>), a detecting region <NUM>, and a detector <NUM>. The detector <NUM> may be mounted on the gantry <NUM>. The bed <NUM> may be positioned within a bore of the gantry <NUM>. Specifically, the bed <NUM> may be adapted to be accommodated in a bore enclosed by a plurality of detector units of the detector <NUM> mounted on the gantry <NUM>.

The bed <NUM> may support an object (e.g., a phantom) for scanning. The object (e.g., a phantom) may include a radioactive source that may emit radiology rays. The radiology rays emitted by the phantom may be detected by one or more detector units of the detector <NUM>. When an object is supported by a bed <NUM>, the bed <NUM> may be at a bed location. Merely by way of example, a bed location may be described as a location of the bed <NUM> relative to the gantry <NUM> of the PET system <NUM> in a certain direction. The certain direction may include, for example, an X direction, a Y direction, and/or a Z direction. As used herein, the X direction, the Y direction, and the Z direction may represent an X axis, a Y axis, and a Z axis in a coordinate system. Merely by way of example, the X axis and the Z axis may be in a horizontal plane , the X axis and the Y axis may be in a vertical plane, the Z axis may be along the rotational axis of the PET scanner <NUM>. The phantom supported by the bed <NUM> may be at a phantom position. The phantom position may be described as a spatial location of the phantom relative to the gantry <NUM> of the PET system <NUM> in a certain direction. The certain direction may include, for example, an X direction, a Y direction, and/or a Z direction as illustrated elsewhere in the present disclosure. In some embodiments, the phantom may be placed at a plurality of phantom positions. The plurality of phantom positions may be expressed as below:
{phantom position <NUM>, phantom position <NUM>,. , phantom position i,. , and phantom position N}.

In some embodiments, the phantom may be fixed on the bed <NUM>, and a phantom position may correspond to a bed position. In some embodiments, when the bed <NUM> stops at a bed position, the phantom may be moved on the bed <NUM> to stop at a plurality of phantom positions for imaging. Therefore, a bed position may correspond to a plurality of phantom positions.

The detector <NUM> may detect or collect PET data relating to photons. The photons may include a gamma photon, an x-ray photon, or the like, or any combination thereof. The PET data may include, for example, scanning data related to the object being scanned (e.g., the phantom). The scanning data may include, for example, a plurality of coincidence events detected by the detector <NUM> and/or line of response (LOR)s corresponding to the plurality of coincidence events. As used herein, an LOR may refer to a line connecting the detector units that have detected two photons of a coincidence event. Merely by way of example, the detector <NUM> may collect a first set of PET data. The first set of PET data may refer to original PET data (e.g., counting response of the detector <NUM>) collected by the scanner. In some embodiments, the phantom may be placed at a plurality of phantom positions to generate the first set of PET data. For example, the first set of PET data may include a plurality sub-sets of PET data, which may be generated by the phantom at a plurality of phantom positions respectively. The plurality sub-sets of PET data may be expressed as below:
{PET data <NUM>, PET data <NUM>,. , PET data i,. , and PET data N}
wherein each sub-set of PET data of the plurality sub-sets of PET data may correspond to a phantom position of the plurality of phantom positions. Merely by way of example, PET data <NUM> may correspond to phantom position <NUM>, PET data may correspond to phantom position <NUM>, PET data i may correspond to phantom position i, etc. I or N may represent an interger larger than <NUM>.

In some embodiments, at least a portion of the first set of PET data (also referred to as a second set of PET data) may correspond to one or more coincidence events of the phantom. The second set of PET data may be extracted from the first set of PET data. The detailed description of extracting the second set of PET data may be found in <FIG> in the present disclosure and the description thereof.

In some embodiments, the detector <NUM> may include one or more detector units for detecting scanning data relating to an object (e.g., a phantom), or a portion thereof, located in the detecting region <NUM>. A detector unit may include a scintillation detector <NUM> (e.g., a cesium iodide detector <NUM>), a gas detector <NUM>, etc. The detector <NUM> may be and/or include a single-row detector <NUM> and/or a multi-row detector <NUM>. In some embodiments, the detector <NUM> may further send the detected PET data to the processing engine <NUM>.

The network <NUM> may include any suitable network that can facilitate exchange of information and/or data (e.g., emission data) for the PET system <NUM>.

In some embodiments, one or more components of the PET system <NUM> (e.g., the PET scanner <NUM>, the terminal <NUM>, the processing engine <NUM>, the storage <NUM>, etc.) may communicate information and/or data with one or more other components of the PET system <NUM> via the network <NUM>. For example, the processing engine <NUM> may obtain emission data from the PET scanner <NUM> via the network <NUM>. As another example, the processing engine <NUM> may obtain user instructions from the terminal <NUM> via the network <NUM>.

The network <NUM> may be and/or include a public network (e.g., the Internet), a private network (e.g., a local area network (LAN), a wide area network (WAN)), etc.), a wired network (e.g., an Ethernet network), a wireless network (e.g., an <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, switches, server computers, and/or any combination thereof. Merely by way of example, the network <NUM> may include 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> may include one or more network access points. For example, the network <NUM> may include wired and/or wireless network access points such as base stations and/or internet exchange points through which one or more components of the PET system <NUM> may be connected to the network <NUM> to exchange data and/or information.

The terminal(s) <NUM> may include a mobile device <NUM>, a tablet computer <NUM>, a laptop computer <NUM>, or the like, or any combination thereof. In some embodiments, the mobile device <NUM> may include 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 may include 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 may include 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 may include 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 may include 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 may include a Google Glass™, an Oculus Rift™, a Hololens™, a Gear VR™, etc. In some embodiments, the terminal(s) <NUM> may be part of the processing engine <NUM>.

The processing engine <NUM> may process data and/or information obtained from the PET scanner <NUM>, the terminal <NUM>, and/or the storage <NUM>. Merely by way of example, the processing engine <NUM> may process the emission data (e.g., the reference emission data, the working emission data, etc.) transmitted from the detector <NUM> of the PET scanner <NUM>.

In some embodiments, the processing engine <NUM> may be a single server or a server group. The server group may be centralized or distributed. In some embodiments, the processing engine <NUM> may be local or remote. For example, the processing engine <NUM> may access information and/or data stored in the PET scanner <NUM>, the terminal <NUM>, and/or the storage <NUM> via the network <NUM>. As another example, the processing engine <NUM> may be directly connected to the PET scanner <NUM>, the terminal <NUM> and/or the storage <NUM> to access stored information and/or data. In some embodiments, the processing engine <NUM> may be implemented on a cloud platform. Merely by way of example, the cloud platform may include 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.

The storage <NUM> may store data, instructions, and/or any other information. In some embodiments, the storage <NUM> may store data obtained from the terminal <NUM> and/or the processing engine <NUM>. In some embodiments, the storage <NUM> may store data and/or instructions that the processing engine <NUM> may execute or use to perform exemplary methods described in the present disclosure. In some embodiments, the storage <NUM> may include 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 may include a magnetic disk, an optical disk, a solid-state drive, etc. Exemplary removable storage may include 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 may include a random access memory (RAM). Exemplary RAM may include 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 may include 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> may be implemented on a cloud platform. Merely by way of example, the cloud platform may include 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> may be connected to the network <NUM> to communicate with one or more other components in the PET system <NUM> (e.g., the processing engine <NUM>, the terminal <NUM>, etc.). One or more components in the PET system <NUM> may access the data or instructions stored in the storage <NUM> via the network <NUM>. In some embodiments, the storage <NUM> may be directly connected to or communicate with one or more other components in the PET system <NUM> (e.g., the processing engine <NUM>, the terminal <NUM>, etc.). In some embodiments, the storage <NUM> may be part of the processing engine <NUM>.

The motion controller <NUM> may move the phantom to a plurality of phantom positions. The motion controller <NUM> may move the phantom to the plurality of phantom positions directly. For example, the phantom may connect to a motion controller <NUM> placed on the bed <NUM>. The motion controller <NUM> may move the phantom directly on the bed <NUM>. The motion controller <NUM> may move the phantom to the plurality of phantom positions indirectly. For example, the bed <NUM> may connect to a motion controller <NUM>, and the motion controller <NUM> may move the bed <NUM> to a plurality of positions in a certain direction (e.g., the X direction, the Y direction, and/or the Z direction). Accordingly, the phantom being placed on the bed <NUM> may be moved to a plurality of positions in the certain direction (e.g., the X direction, the Y direction, and/or the Z direction).

The motion controller <NUM> may be of various configurations. For example, the motion controller <NUM> may include a first motion controller and/or a second motion controller. The first motion controller may move the bed <NUM> and/or the phantom in one or more certain directions. Merely by way of example, the first motion controller may include a first moving mechanism and a second moving mechanism. The first moving mechanism (or referred to as a scanning-table driving mechanism) may be configured to move the bed <NUM> in a first direction (e.g., the Z direction) or a second direction (e.g., the Y direction). The second moving mechanism (or referred to as phantom controlling device) may be configured to move the phantom in a third direction (e.g., the Y direction) perpendicular to the first direction and the second direction. The second motion controller may move the phantom in a one or more certain directions (e.g., the Z direction). Exemplary first motion controller, first moving mechanism, second moving mechanism, may be found in <FIG> and the description thereof. Exemplary second motion controller may be found in <FIG> and the description thereof.

<FIG> is a block diagram illustrating an exemplary processing engine <NUM> according to some embodiments of the present disclosure. As illustrated in <FIG>, the processing engine <NUM> may include a parameter acquisition module <NUM>, a motion controlling module <NUM>, a data acquisition module <NUM>, a processing module <NUM>, and a storage module <NUM>.

The parameter acquisition module <NUM> may acquire at least one of a scanning parameter of a scanner (e.g., the scanner of the PET system <NUM>) or a parameter of a phantom from one or more components in the PET system <NUM> (e.g., the PET scanner <NUM>, the network <NUM>, the terminal <NUM>, and/or the storage <NUM>). The scanning parameter may be configured to scan a phantom and different configurations of the scanning parameter may cause different results of the scanning of a phantom. In some embodiments, the scanning parameter may be related to the size or structure of a scanner (e.g., the PET scanner <NUM> of the PET system <NUM>). For example, the scanning parameter may include the length of the axis of the scanner. In some embodiments, the scanning parameter may be designated by a user (e.g., a doctor, a nurse, a patient, etc.). For example, the scanning parameter of the scanner may include scan time of the scanner. A parameter of the phantom may include phantom weight, the length of the axis of the phantom, the size of the phantom, etc..

The parameter acquisition module <NUM> may connect to or communicate with the motion controlling module <NUM>, and transmit the acquired parameter (e.g., the scanning parameter of the scanner, or the parameter of the phantom) thereto.

The motion controlling module <NUM> may determine a plurality of phantom positions and/or generate a motion instruction to control the movement of the phantom and/or the bed <NUM>.

The motion controlling module <NUM> may determine a plurality of phantom positions. In some embodiments, the motion controlling module <NUM> may determine the plurality of phantom positions based on the scanning parameter of the scanner and/or the parameter of the phantom. Merely by way of example, the motion controlling module <NUM> may determine the plurality of phantom positions based on scan time of the scanner, the length of the axis of the scanner, phantom weight or the length of the axis of the phantom. The determined plurality of phantom positions may be expressed as below:
{phantom position <NUM>, phantom position <NUM>,. , phantom position i,. , and phantom position N}.

In some embodiments, the plurality of the phantom positions may ensure that the axis of the scanner is completely covered by the phantom while being placed in the plurality of phantom positions. Therefore, the scintillator crystals in the detector <NUM> may be irradiated by the phantom while being placed in the plurality of phantom positions (e.g., radiation rays generated by the phantom). For example, the plurality of phantom positions may include a phantom position <NUM> and a phantom position <NUM>. When the phantom is placed in the phantom position <NUM>, a first set of scintillator crystals corresponding to a first part of the axis of the scanner may be irradiated by radiation rays generated by the phantom. When the phantom is placed in the phantom position <NUM>, a second set of scintillator crystals corresponding to a second part of the axis of the scanner may be irradiated by radiation rays generated by the phantom. The first set of scintillator crystals and at least part of the second set of scintillator crystals may constitute all the scintillator crystals in the detector <NUM>. The first part of the axis of the scanner and at least part of the second part of the axis of the scanner may correspond to the entire axis of the PET scanner <NUM>. Thus, while placing the phantom in the phantom positon <NUM> and the phantom position <NUM>, the phantom may cover the axis of the scanner, and the scintillator crystals in the detector <NUM> may be irradiated by radiation rays generated by the phantom at the phantom position <NUM> and the phantom position <NUM>.

The motion controlling module <NUM> may generate a motion instruction to control the movement of the phantom and/or the bed <NUM>. As used herein, a movement of the phantom (or the bed <NUM>) may be represented by one or more parameters, for example, a velocity of the phantom (or the bed <NUM>), an accelerated velocity of the phantom (or the bed <NUM>), a moving direction of the phantom (or the bed <NUM>), a moving time span of the phantom (or the bed <NUM>), a moving range of the phantom (or the bed <NUM>), an acceleration range of the phantom (or the bed <NUM>), a deceleration range of the phantom (or the bed <NUM>), or the like, or a combination thereof. In some embodiments, the motion controlling module <NUM> may generate the motion instruction based on a user command. The user command may be input by the user through, for example, the terminal <NUM>.

The motion controlling module <NUM> may connect to or communicate with the motion controller <NUM> or the data acquisition module <NUM>. For example, the motion controlling module <NUM> may transmit the determined plurality of phantom positions to the data acquisition module <NUM>. As another example, the motion controlling module <NUM> may transmit the generated motion instruction to the motion controller <NUM>, which may operate according to the motion instruction.

The data acquisition module <NUM> may acquire data and/or information from the motion controller <NUM> and one or more components in the PET system <NUM> (e.g., the PET scanner <NUM>, the network <NUM>, the terminal <NUM>, the processing engine <NUM>, and/or the storage <NUM>). The data and/or information acquired may include the determined plurality of phantom positions, a first set of PET data, and correction data.

The first set of PET data may refer to original PET data collected by the scanner. The original PET data may include counting response of the detector <NUM>. In some embodiments, the first set of PET data may correspond to the plurality of phantom positions determined by the motion controlling module <NUM>.

The correction data may be configured to correct a PET image related to the phantom and/or determine a factor of the detector <NUM>. Merely by way of example, the correction data may include counting response of each scintillator crystal of the detector <NUM>, based on which a normalizing factor for normalizing the detecting efficiency of the detector <NUM> may be determined. The counting response of the detector <NUM> may be determined by placing the phantom in a plurality of phantom positions. As another example, the correction data may include a first set of attenuation data for the phantom, based on which a PET image related to the phantom may be corrected. As used herein, the first set of attenuation data for the phantom may refer to attenuation data corresponding to part of the field of vision (FOV) of the PET system <NUM>. The attenuation data may include an attenuation map generated from the CT scan data of the phantom. Further, as another example, the correction data may include nuclide decay information for the phantom, based on which a PET image related to the phantom may be corrected.

The data acquisition module <NUM> may transmit the acquired data and/or information to the motion controlling module <NUM>, the processing module <NUM>, and/or the storage module <NUM>. In some embodiments, the data acquisition module <NUM> may transmit the plurality of phantom positions, the first set of PET data, and the correction data to the processing module <NUM>. Specifically, for example, the data acquisition module <NUM> may transmit the acquired first set of PET data, the plurality of phantom positions, and/or the first set of attenuation data for the phantom to the PET image reconstruction unit <NUM> (shown in <FIG>) in the processing module <NUM>. As another example, the data acquisition module <NUM> may transmit the plurality of phantom positions and the nuclide decay information for the phantom to the correction unit <NUM> (shown in <FIG>) in the processing engine <NUM>.

The processing module <NUM> may process information provided by the data acquisition module <NUM>. In some embodiments, the processing module <NUM> may reconstruct PET images based on the first set of PET data, the plurality of phantom positions, and/or the first set of attenuation data for the phantom according to a reconstruction algorithm, determine a normalizing factor of the detector <NUM>, and/or perform any other function for image reconstruction in accordance with various embodiments of the present disclosure. The reconstruction algorithm may include an ML-EM (Maximum Likelihood Expectation Maximization), an OSEM (Ordered Subset Expectation Maximization), a RAMLA (Row-Action Maximum Likelihood Algorithm), a DRAMA (Dynamic Row-Action Maximum Likelihood Algorithm), or the like, or a combination thereof.

The storage module <NUM> may store PET data, control parameters, processed PET data, or the like, or a combination thereof. For example, the storage module <NUM> may store the algorithms to be employed by the processing module <NUM>. As another example, the storage module <NUM> may store the first set of PET data acquired from the data acquisition module <NUM>. In some embodiments, the storage may store 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 may store program(s) and/or instruction(s) that can be executed by the processor(s) of the processing engine <NUM> to cause the PET system <NUM> or a portion thereof to acquire PET data and/or to process the PET data, etc. In some embodiments, the storage module <NUM> may include a mass storage. For example, the mass storage may include a magnetic disk, an optical disk, a solid-state drives, etc..

It should be noted that the above description of the processing engine <NUM> 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 and modifications may be made under the teaching of the present invention. However, those variations and modifications do not depart from the scope of the present disclosure. For example, the parameter acquisition module <NUM> and the data acquisition module <NUM> may be integrated to a data acquisition module <NUM>, which perform the function of both the parameter acquisition module <NUM> and the data acquisition module <NUM>.

<FIG> is a flowchart illustrating an exemplary process <NUM> for processing PET data according to some embodiments of the present disclosure. The process, or a portion thereof, may be implemented on a processing engine <NUM> as illustrated in <FIG>. For illustration purposes, the following description is provided with reference to the PET system <NUM> as illustrated in <FIG>. As already described, the PET system <NUM> includes a detector <NUM> including scintillator crystals.

In <NUM>, the parameter acquisition module <NUM> may acquire at least one of a scanning parameter of a scanner or a parameter of a phantom. The scanning parameter may be configured to scan a phantom and different configurations of the scanning parameter may cause different results of the scanning of a phantom. For example, the scanning parameter may include the length of the axis of the scanner, scan time of the scanner, etc. The parameter of the phantom may include phantom weight, the length of the axis of the phantom, the size of the phantom, etc..

In <NUM>, the motion controlling module <NUM> may determine a plurality of phantom positions based on the at least one of the scanning parameter of the scanner or the parameter of the phantom. Merely by way of example, the motion controlling module <NUM> may determine the plurality of phantom positions based on scan time of the scanner, the length of the axis of the scanner, phantom weight or the length of the axis of the phantom. The determined plurality of phantom positions may be expressed as: {phantom position <NUM>, phantom position <NUM>,. , phantom position i,. , and phantom position N}. In some embodiments, the determined plurality of the phantom positions may ensure that the axis of the scanner is completely covered by the phantom while being placed in the plurality of phantom positions. Therefore, the scintillator crystals in the detector <NUM> maybe irradiated by the phantom (e.g., radiation rays generated by the phantom) while being placed in the plurality of phantom positions.

In <NUM>, the data acquisition module <NUM> may acquire a first set of PET data produced by the phantom at the plurality of phantom positions. The first set of PET data may refer to a set of original PET data collected by the scanner while the phantom is placed at the plurality of phantom positions. The set of original PET data may include a plurality of sub-sets of PET data, which may be generated by the phantom at the plurality of phantom positions respectively. The plurality sub-sets of PET data may be expressed as: {PET data <NUM>, PET data <NUM>,. , PET data i,. , and PET data N}.

In <NUM>, the processing module <NUM> may process the acquired first set of PET data. In some embodiments, the processing module <NUM> may process the acquired first set of PET data (e.g., the PET data <NUM>, the PET data <NUM>, etc.) corresponding to the respective phantom positions (e.g., the phantom position <NUM>, the phantom position <NUM>, etc.) to generate a PET image. In some embodiments, the processing module <NUM> may process the acquired first set of PET data to determine normalizing factors of a detector <NUM>. For example, the acquired first set of PET data may include counting responses (e.g., a first counting response, a second counting response, an ith counting response , an nth counting response, etc.) of scintillator crystals (e.g., a first scintillator crystal, a second scintillator crystal, an ith scintillator crystal, an nth scintillator crystal, etc.) of the detector <NUM>. The normalizing factor of a certain scintillator crystal may be determined based on the counting response of the scintillator crystal. For example, the normalizing factor of the ith scintillator crystal Mi may be determined by: <MAT> wherein M may represent the number of the scintillator crystals, Di may represent the counting response of the ith scintillator crystal, and i may represent an integer larger than <NUM>.

It should be noted that the flowchart described above is provided for the purposes of illustration, not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be reduced to practice in the light of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, a step in which the first set of PET data may be stored may be added between operation <NUM> and <NUM>.

<FIG> is a block diagram illustrating an exemplary motion controlling module <NUM> according to some embodiments of the present disclosure. As illustrated, the motion controlling module <NUM> may include a bed motion controlling unit <NUM>.

The bed motion controlling unit <NUM> may control the movement of the scanning table <NUM> (or referred to as the bed <NUM>) and adjust the position of the scanning table <NUM> in real time. For example, the bed motion controlling unit <NUM> may drive the scanning table <NUM> to move along the rotational axis of the PET scanner <NUM>.

In some embodiments, the bed motion controlling unit <NUM> may control the movement of the scanning table <NUM> based on the scanning parameters of the PET scanner <NUM>, the information of the phantom and/or the information of the scanning table <NUM>. Specifically, the bed motion controlling unit <NUM> may perform logical calculations based on the acquired scanning parameters of the PET scanner <NUM>, the information of the phantom and/or the information of the scanning table <NUM> to obtain motion control logic of the scanning table <NUM>. The motion control logic of the scanning table <NUM> may relate to, for example, a movement range of the scanning table <NUM> along the axis (Z direction) of the detector <NUM>, a movement speed of the scanning table <NUM> and acceleration/deceleration positions of the scanning table <NUM>. As used herein, an acceleration position of the scanning table <NUM> may relate to location at which the scanning table <NUM> starts to accelerate. A deceleration position of the scanning table <NUM> may relate to location at which the scanning table <NUM> starts to decelerate. In some embodiments, to ensure the detector <NUM> to collect enough phantom data (or referred to as scanning data related to the phantom), the scanning time of the PET system <NUM> to the phantom may be increased, the scanning table <NUM> may perform reciprocating motions. The number of times of reciprocating motion of the scanning table <NUM> may be adjusted and controlled by the motion control logic of the scanning table <NUM>, which is calculated by the bed motion controlling unit <NUM>. It should be noted that the bed motion controlling unit <NUM> may control the scanning table <NUM> to move continuously during a certain time interval or move at a uniform velocity. The bed motion controlling unit <NUM> may also control the scanning table <NUM> to move dis-continuously during at least one certain time interval or at a non-uniform velocity. It may be within the intent of the present disclosure to control the movement of the scanning table <NUM> during the scanning process, to ensure predetermined detector units to detect the phantom (or the scanning data related to the phantom). As used herein, the predetermined detector units may refer to one or more detector units of which the detecting abilities are to be tested. The predetermined detector units may be designated by a user or the PET system <NUM>. The predetermined detector units may include one or more detector units. For example the predetermined detector units may include all detector units of the detector <NUM>.

<FIG> is a block diagram illustrating an exemplary storage module <NUM> according to some embodiments of the present disclosure. As illustrated, the storage module <NUM> may include a PET scan data unit <NUM>. The PET scan data unit <NUM> may store the scanning data related to the phantom, the position information of the scanning table <NUM>, and/or the position or length information of the phantom.

<FIG> is a flowchart illustrating a method for collecting PET data (or referred to as a PET data collection method) according to some embodiments of the present disclosure. As shown in <FIG>, the method may include one or more steps as illustrated below.

In <NUM>, a phantom may be placed on the scanning table <NUM>, and the length of the axis of the phantom may be shorter than the length of the axis of FOV of the detector <NUM>.

In <NUM>, the scanning table <NUM> may be controlled to drive the phantom to move along the axis of FOV of the detector <NUM>. Meanwhile, the detector <NUM> may be used to collect coincidence events from the phantom.

In the PET data collection method according to the present disclosure, the predetermined detector units may be irradiated by the phantom by controlling a movement of the scanning table <NUM> during the collection related to the phantom. When the predetermined detector units include all the detector units of the detector <NUM>, the collected data by all the detector units of the detector <NUM> may be used to determine a normalizing factor and generate a reconstructed PET image. Thus, in the PET data collection method according to the present disclosure, by controlling the movement of the scanning table <NUM>, most of the axial FOV, or even entire axial FOV of the detector <NUM> may be covered by a short phantom (e.g., a phantom with an axis shorter than the axis of the PET scanner <NUM>). In conclusion, via the PET data collection method according to the present disclosure, a phantom (the length of the axis of the phantom may be shorter than the length of the axis of FOV of the detector <NUM>) may be used to facilitate the predetermined detector units in the detector <NUM> and even all detector units to collect data of the phantom.

With the scanning method according to the present disclosure, for the long axial PET system <NUM>, a single phantom with an axial length shorter than the axial length of FOV of the detector <NUM> may be used to facilitate the predetermined detector units to collect data of the phantom and ensure the radiation uniformity of the phantom.

Further, data obtained by the scanning method of a PET system <NUM> according to the present disclosure may be applied to a PET image reconstruction. The reconstructed PET image may further be used to analyze the PET system <NUM>. The data obtained by the scanning method according to the present disclosure may be utilized to generate the normalizing factor of the detector efficiency.

<FIG> is a diagram illustrating a method for collecting PET data according to an embodiment of the present disclosure. The scanning method of the PET system <NUM>, in some embodiments will be further described below in combination with <FIG>, <FIG> and <FIG>.

In step <NUM>, a phantom may be placed on the scanning table <NUM> and the length of the axis of the phantom may be shorter than the length of the axis of FOV of the detector <NUM>.

Referring to <FIG>, the PET system <NUM> may include a detector <NUM> and a scanning table <NUM>. During a scan of the PET system <NUM>, the phantom may be placed on the scanning table <NUM>. With a movement of the scanning table <NUM>, the phantom may be moved into the FOV of the detector <NUM> so that the phantom may be scanned by the detector <NUM> to collect coincidence events generated from the phantom. Further, the detector <NUM> may include a plurality of detector units arranged in a circular shape. The coincidence events within the FOV of the detector <NUM> may be detected by the plurality of detector units <NUM>.

In step <NUM>, the scanning table <NUM> may be controlled to drive the phantom to move along the axis of FOV of the detector <NUM>. Meanwhile, the detector unit may be used to collect coincidence events from the phantom. Thus, during the data collection process, the phantom may be moved along the axis to ensure that the predetermined detector units are irradiated by the phantom.

Further, when the scanning table <NUM> is controlled to move with the phantom along the axis of the PET scanner <NUM>, the movement of the scanning table <NUM> may be specifically controlled based on scanning parameters of the PET scanner <NUM>. The scanning parameters of the PET scanner <NUM> may include a scanning time and/or the length of the axis of FOV of the detector <NUM> (e.g., the Z direction shown in <FIG>). Further, when the scanning table <NUM> is controlled to move with the phantom along the axis of the PET scanner <NUM>, the scanning table <NUM> may also be controlled to move with the phantom based on information of the phantom. The information of the phantom may include the length, position and weight of the phantom, etc. Specifically, the information of the phantom may be obtained by a Computed Tomography (CT) image of the phantom. The CT image of the phantom may be obtained by CT scanning of the phantom.

The phantom may be placed on the scanning table <NUM> and may be moved along with the movement of the scanning table <NUM>. When the scanning table <NUM> is controlled to move with the phantom along the axis of the PET scanner <NUM>, information of the scanning table <NUM> may be further combined to control the movement of the phantom along the axis of the PET scanner <NUM> (e.g., the Z direction shown in <FIG>) and along a direction perpendicular to the axis (e.g., the Y direction shown in <FIG>). In some embodiments, the information of the scanning table <NUM> may be a deformation factor of the scanning table <NUM> estimated by a deformation curve of the scanning table <NUM>. Specifically, the deformation factor of the scanning table <NUM> may include the deformation factor of the scanning table <NUM> in the height direction, the direction perpendicular to the ground floor (e.g., the Y direction shown in <FIG>). It may be possible to adjust the height position of the scanning table <NUM> in real time by applying the deformation factor of the scanning table <NUM> to the height direction. In some embodiments, the height position of the scanning table <NUM> may be adjusted dynamically in a manner to ensure that the phantom (or a certain point of the phantom) moves along the axis of the PET scanner (e.g., the Z direction shown in <FIG>).

During the scanning of the phantom by the detector <NUM>, the movement of the scanning table <NUM> may be controlled. In some embodiments, the scanning table <NUM> may be moved to a plurality of bed positions. As a result, the phantom placed on the scanning table <NUM> may be moved to a plurality of phantom positions. Thus, for a PET system <NUM> with a long axial length, the predetermined detector units may be irradiated respectively by a short phantom (e.g., a phantom with an axis shorter than the length of the axial FOV of the detector <NUM>) placed at the plurality of phantom positions. In some embodiments, most or all of the detector units in the detector <NUM> may be irradiated when scanning with a short phantom at the plurality of phantom positions to ensure that the phantom cover most of the axial FOV (e.g., <NUM>%) or even the entire axial FOV of the detector <NUM>.

As described above, when the movement range of the phantom along the axis of the PET scanner <NUM>10corresponds to an axial length larger than or equal to the length of the axis of FOV of the detector <NUM>, the irritation of phantom may completely cover the entire axial FOV of the detector <NUM>, and thus, all detector units of the detector <NUM> may collect data of the phantom. In some embodiments, the data collected by the detector units (e.g., all detector units of the detector <NUM>) may be further used for the normalization correction (e.g., determining a normalizing factor) or PET image reconstruction. In addition, since all detector units collect data based on a uniform phantom rather than a phantom formed by splicing, for example, a few sub-phantoms, the coincidence events detected by all detector units are statistically the same. Therefore, a more accurate normalizing factor and a more accurate reconstructed PET image may be obtained, compared with that generated with a phantom that is spliced by a few sub-phantoms. As a result, the performance of the PET system <NUM> may be tested and the PET system <NUM> may be corrected more accurately.

<FIG> is a block diagram illustrating an exemplary processing module <NUM> according to some embodiments of the present disclosure. As shown, the processing module <NUM> may include a PET image reconstruction unit <NUM> and a correction unit <NUM>. The correction unit <NUM> may include an axial counting correction sub-unit <NUM>.

The PET image reconstruction unit <NUM> may be configure to reconstruct a PET image based on the coincidence events detected by the detector units. The PET image reconstruction unit <NUM> may reconstruct a PET image based on the first set of PET data, the plurality of phantom positions, and/or the first set of attenuation data for the phantom acquired from the data acquisition module <NUM>. Merely by way of example, the PET image reconstruction unit <NUM> may be used to extract valid scanning data based on position of the phantom and to reconstruct PET image in conjunction with attenuation information for the phantom within the entire axial FOV. In some embodiments, the PET image reconstruction unit <NUM> may transmit the generated PET image to the correction unit <NUM>.

The correction unit <NUM> may correct the generated PET image and/or determine a normalizing factor based on correction data (e.g., first set of attenuation data for the phantom, counting response of each scintillator crystal of the detector <NUM>, and the nuclide decay information for the phantom) and the plurality of phantom positions from the data acquisition module <NUM>. For example, the correction unit <NUM> may correct the reconstructed PET image based on the plurality of phantom positions and the nuclide decay information for the phantom. To correct the reconstructed PET image, the correction unit <NUM> may generate statistic data of phantom position by normalizing a plurality of phantom positions, generate statistic data of nuclide decay by normalizing nuclide decay, and further correct the PET image based on the statistic data of phantom position and the statistic data of nuclide decay. The plurality of phantom positions and the nuclide decay may correspond to the FOV of the detector <NUM>. As another example, the correction unit <NUM> may correct the reconstructed PET image based on the first set of attenuation data for the phantom and the plurality of phantom positions. As another example, the correction unit <NUM> may determine a normalizing factor for normalizing the detecting efficiency of the detector <NUM> based on the counting response of each scintillator crystal of the detector <NUM>. The correction unit <NUM> may correct an axial count of the detector <NUM>. For example, as illustrated, the correction unit <NUM> may include an axial counting correction sub-unit <NUM>. The axial counting correction sub-unit <NUM> may be used to perform an axial count correction based on statistic information about the scanning table position and statistic information about the nuclide decay within the axial FOV, in conjunction with the reconstructed PET image, to improve the image deviation that may be caused by the movement of the scanning table <NUM> and the nuclide decay.

It should be noted that the above description of the processing module <NUM> 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 and modifications may be made under the teaching of the present invention. However, those variations and modifications do not depart from the scope of the present disclosure. For example, the correction unit <NUM> may be omitted and the function of the correction unit <NUM> may be realized by the image reconstruction unit.

<FIG> is a flowchart illustrating an exemplary process <NUM> for processing PET data according to some embodiments of the present disclosure.

In <NUM>, the PET image reconstruction unit <NUM> may reconstruct a PET image at least based on the acquired first set of PET data. For example, the PET image reconstruction unit <NUM> may reconstruct the PET image based on the acquired first set of PET data and the plurality of phantom positions corresponding to the first set of PET data for the phantom. One or more reconstruction algorithms may be employed to reconstruct the PET image. Exemplary reconstruction algorithms may be illustrated elsewhere in the present disclosure.

In <NUM>, the correction unit <NUM> may acquire correction data. For example, the correction unit <NUM> may acquire the first set of attenuation data for the phantom. As another example, the correction unit <NUM> may acquire the nuclide decay information for the phantom.

In <NUM>, the correction unit <NUM> may correct the reconstructed PET image based on the plurality of phantom positions and the correction data. For example, the correction unit <NUM> may correct the reconstructed PET image based on the plurality of phantom positions and the nuclide decay information for the phantom. As another example, the correction unit <NUM> may correct the reconstructed PET image based on the first set of attenuation data for the phantom and the plurality of phantom positions.

It should be noted that the flowchart described above is provided for the purposes of illustration, not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be reduced to practice in the light of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, a step in which the correction data may be stored may be added to the process <NUM>.

<FIG> is a block diagram illustrating an exemplary PET image reconstruction unit <NUM> according to some embodiments of the present disclosure. As illustrated, the PET image reconstruction unit <NUM> may include a valid data extraction sub-unit <NUM>, an attenuation determination sub-unit <NUM>, and an image reconstruction sub-unit <NUM>.

The valid data extraction sub-unit <NUM> may extract the second set of PET data (or referred to as valid scanning data) from the first set of PET data. As described above, the first set of PET data may refer to original PET data collected by the detector units at the plurality of phantom positions (e.g., phantom position <NUM>, phantom position <NUM>, etc.). The original PET data may include valid scanning data corresponding to the phantom and invalid PET data not corresponding to the phantom. Merely by way of example, when the phantom is placed at a certain phantom position of the plurality phantom positions, scanning data corresponding to the phantom may be detected by a certain number of detector units of the detector <NUM> that are within a spatial range related to the phantom position. Meanwhile, one or more detector units beyond the spatial range may detect data not relating to the phantom (or referred to as invalid scanning data). The valid data extraction sub-unit <NUM> may extract the valid scanning data (or referred to as the second set of PET data) from the first set of PET data based on the corresponding phantom position. Merely by way of example, for each of at least one phantom position of the plurality of phantom positions, the valid data extraction sub-unit <NUM> may determine data collected by the detector units within a predetermined spatial range related to the phantom position to be valid scanning data and extract the determined valid scanning data from the first set of PET data. The extracted valid scanning data corresponding to the plurality of phantom positions may constitute the second set of PET data. In some embodiments, the valid data extraction sub-unit <NUM> may transmit the extracted second set of PET data to the image reconstruction sub-unit <NUM>.

The attenuation determination sub-unit <NUM> may determine a second set of attenuation data for the phantom. As used herein, the second set of attenuation data for the phantom may to attenuation data corresponding to the entire FOV of the PET system <NUM>. In some embodiments, the attenuation determination sub-unit <NUM> may determine the second set of attenuation data for the phantom based on the plurality of phantom positions and the first set of attenuation data which corresponds to part of the FOV of the PET system <NUM>. In some embodiments, the attenuation determination sub-unit <NUM> may further employ a relationship between the phantom position and the attenuation data may to determine the second set of attenuation data for the phantom. In some embodiments, the attenuation determination sub-unit <NUM> may transmit the determined second set of attenuation data for the phantom to the image reconstruction sub-unit <NUM>.

The image reconstruction sub-unit <NUM> may reconstruct a PET image based on the second set of PET data and the second set of attenuation data. For example, the image reconstruction sub-unit <NUM> may reconstruct the PET image based on the second set of PET data. As another example, the image reconstruction sub-unit <NUM> may reconstruct the PET image based on the second set of PET data and the second set of attenuation data for the phantom. The image reconstruction sub-unit <NUM> may employ an image reconstruction algorithm to reconstruct the PET image. Exemplary image reconstruction algorithms may be illustrated elsewhere in the present disclosure.

It should be noted that the above description of the PET image reconstruction unit <NUM> 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 and modifications may be made under the teaching of the present invention. However, those variations and modifications do not depart from the scope of the present disclosure. For example, the valid data extraction sub-unit <NUM> may be omitted and the function of the valid data extraction sub-unit <NUM> may be realized by the image reconstruction sub-unit <NUM>.

In <NUM>, the valid data extraction sub-unit <NUM> may extract a second set of PET data from first set of PET data based on a plurality of phantom positions of a phantom. The first set of PET data may be collected at the plurality of phantom positions. The second set of PET data may correspond to one or more coincidence events of the phantom. The valid data extraction sub-unit <NUM> may extract the second set of PET data from the first set of PET data based on the corresponding phantom position. Merely by way of example, for each of at least one phantom position of the plurality of phantom positions, the valid data extraction sub-unit <NUM> may extract a set of data collected by the detector units within a predetermined spatial range relating to the phantom position. The extracted plurality sets of data, which may correspond to the at least one phantom position of the plurality of phantom positions, may constitute the second set of PET data.

In <NUM>, the attenuation determination sub-unit <NUM> may acquire a first set of attenuation data for the phantom, the first set of attenuation data corresponding to part of FOV of an imaging device.

In <NUM>, the attenuation determination sub-unit <NUM> may determine a second set of attenuation data for the phantom corresponding to the FOV of the imaging device based on the plurality of phantom positions and the first set of attenuation data. For example, the second set of attenuation data for the phantom may correspond to the phantom position <NUM> and phantom position <NUM>. The first set of attenuation data for the phantom may correspond to the phantom position <NUM>. The attenuation determination sub-unit <NUM> may fill attenuation data for the phantom corresponding to the phantom position <NUM> based on the first set of attenuation data for the phantom, the phantom position <NUM> and the phantom position <NUM>, which may further constitute the second set of attenuation data for the phantom with the first set of attenuation data for the phantom.

In <NUM>, the image reconstruction sub-unit <NUM> may reconstruct a PET image based on the second set of PET data and the second set of attenuation data. An image reconstruction algorithm may be employed to reconstruct the PET image. Exemplary image reconstruction algorithms may be illustrated elsewhere in the present disclosure.

It should be noted that the flowchart described above is provided for the purposes of illustration, not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be reduced to practice in the light of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, operations <NUM> and <NUM> may be omitted, and the PET image may be reconstructed based on the second set of PET data.

<FIG> is a flowchart illustrating an exemplary process <NUM> for correcting a PET image according to some embodiments of the present disclosure. The process may be executed by the correction unit <NUM>.

In <NUM>, statistic data of phantom position may be generated by normalizing a plurality of phantom positions corresponding to FOV of an imaging device. A detector <NUM> of the imaging device may collect PET data related to the phantom while being placed at the plurality of phantom positions. While the phantom moves amongst the plurality of phantom positions, the phantom may accelerate or decelerate, thus introducing noise to the PET data collected by the detector <NUM>. The correction unit <NUM> may normalize the plurality of phantom positions to reduce the introduced noise. A normalizing method may be employed to normalize the plurality of phantom positions.

In <NUM>, statistic data of nuclide decay may be generated by normalizing nuclide decay corresponding to the FOV. In some embodiments, the correction unit <NUM> may extract a plurality sets of nuclide decay information corresponding to the plurality of phantom positions corresponding to the FOV from the nuclide decay corresponding to the FOV, respectively. The extracted plurality sets of nuclide decay information may be normalized to determine the statistic data of nuclide decay. A normalizing method may be employed to normalize the plurality of phantom positions.

In <NUM>, the second set of PET data may be corrected based on the statistic data of phantom position and the statistic data of nuclide decay. Merely by way of example, the correction unit <NUM> may perform an axial count correction on the second set of PET data based on the statistic data of phantom position and statistic data of nuclide decay.

It should be noted that the flowchart described above is provided for the purposes of illustration, not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be reduced to practice in the light of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. In operation <NUM>, the first set of PET data rather than the second set of PET data may be corrected based on the statistic data of phantom position and the statistic data of nuclide decay.

The present disclosure also provides a method for reconstructing the PET image. <FIG> is a flowchart illustrating an exemplary process for reconstructing a PET image according to an embodiment of the present disclosure. As shown in <FIG>, the method of reconstructing the PET image may include the following steps.

In <NUM>, scanning data of the phantom may be collected by using the PET data collection method described above. In some embodiments, in the process of collecting data of the phantom by the detector <NUM>, a movement of the scanning table <NUM> may be controlled so that the predetermined detector units may be irradiated. The PET data collection method may be specified as described above and will not be described here. In some embodiments, the movement range of the phantom along the axis may correspond to an axial length larger than or equal to the length of the axis of FOV of the detector <NUM> so that all detector units may collect data of the phantom.

Position information of the scanning table <NUM> may be generated while the scanning table <NUM> is moved. Scanning data may be generated while the detector <NUM> is detecting coincidence events. The scanning data may include, for example, a plurality of coincidence events detected by the detector <NUM> and line of response (LOR)s corresponding to the plurality of coincidence events. As used herein, an LOR may refer to a line that connects the detector units that have detected two gamma photons of a coincidence event.

In some embodiments, the generated position information of the scanning table <NUM> and the scanning data related to the phantom may be further stored in a storage. In some embodiments, corresponding data may be read or retrieved from the storage during the subsequent PET image reconstruction.

In <NUM>, the position information of the phantom may be obtained based on the position information of the scanning table <NUM>.

During the data collection process of the phantom, since the length of the axis of the phantom is shorter than the length of the axis of FOV of the detector <NUM>, at a certain time point, some detector units may be able to collect the scanning data of the phantom while the other detector units, which may not be irradiated by the phantom, may collect scanning data that does not correspond to the phantom. The scanning data corresponding to the phantom may also be referred to as valid scanning data, and the scanning data not corresponding the phantom may also be referred to as invalid data. An image reconstruction should be based on the scanning data of the phantom (e.g., valid scanning data). Therefore, it may be necessary to extract valid scanning data corresponding to the phantom and discard invalid scanning data that does not correspond to the phantom to generate a more accurate PET image. In some embodiments, the valid scanning data corresponding to the phantom may be determined based on the position information of the scanning table <NUM> at the corresponding time point. In some embodiments, the position information of the phantom may be obtained based on the position information of the scanning table <NUM> to further extract the valid scanning data corresponding to the phantom.

In some embodiments, the corresponding scanning data may be extracted from the collected scanning data based on the position information of the phantom to perform the PET image reconstruction.

As described above, after obtaining the position information of the phantom, the valid scanning data corresponding to the phantom may be extracted. In some embodiments, the scanning data related to the phantom may be stored in the PET scan data unit <NUM>, from which the corresponding scanning data may be extracted based on the position information of the phantom. In some embodiments, the corresponding scanning data may be determined based on the position information of the phantom and the length of the phantom.

Specifically, as shown in <FIG>, the process of acquiring the valid scanning data corresponding to the phantom and perform the PET image reconstruction based thereon may include one or more of the following operations.

In step <NUM>, attenuation information for the phantom within the entire axial FOV may be obtained based on attenuation information for the phantom and the position information of the scanning table <NUM>. The attenuation information for the phantom may be acquired, for example, by CT scanning. For example, CT scanning data of the phantom may be acquired by the CT scanning, based on which an attenuation map, or attenuation information for the phantom may be acquired.

As described above, in some embodiments, the length of the axis of the phantom may be shorter than the length of the axis of FOV of the detector <NUM>, and the attenuation information for the phantom within the entire axial FOV may not be acquired during the CT scanning of the phantom, which may be performed to acquire the attenuation information for the phantom. Thus, in some embodiments according to the present disclosure, the position information of the scanning table <NUM> and the known attenuation information for the phantom (e.g., attenuation information corresponding to part of the axis of FOV of the detector <NUM>) may be combined to fill the corresponding position in the axial scanning area with the corresponding attenuation information for the phantom, to acquire the attenuation information for the phantom within the entire axial FOV.

In <NUM>, a PET image reconstruction may be performed with the attenuation information for the phantom within the entire axial FOV, to generate a reconstructed PET image within the entire axial FOV.

In some embodiments, during the PET image reconstruction process, the valid scanning data may be extracted based on the position information of the phantom. Further, a PET image may be reconstructed based on the attenuation information for the phantom and the corresponding scanning data (e.g., the extracted valid scanning data).

The PET image reconstruction method may include, for example, a filtered back projection (FBP) or an ordered subset expectation-maximization (OSEM).

It should be noted that the recited order of the operations in <FIG> is not intended to limit the claimed process. For example, the sequence of the step in which the information for the phantom and the step in which the valid scanning data may be extracted may be exchanged, with a premise that the attenuation information for the phantom and the valid scanning data are available at the time of performing the PET image reconstruction.

In some embodiments, the method of reconstructing the PET image further may include the following steps:.

In step <NUM>, the statistic information of scanning table position and the statistic information of the nuclide decay may be obtained by normalizing the scanning table positions within the axial FOV and the nuclide decay within the axial FOV of the detector <NUM>, respectively.

The statistic information of the scanning table position may be obtained by extracting and normalizing the position information of the scanning table <NUM> and the position or length information of the phantom stored in the PET scan data unit <NUM>. During the data collection process, the movement of the scanning table <NUM> may drive the phantom to move. In some embodiments, when the scanning table <NUM> moves, the scanning table <NUM> may accelerate or decelerate, which may drive the phantom to accelerate or decelerate accordingly. In some embodiments, thorough normalizing the corresponding position information of the scanning table <NUM>, the position of the phantom (the position information of the phantom on the scanning table <NUM>) and/or the length of the phantom at each time point, image differences that may be generated due to the acceleration or deceleration of the scanning table <NUM> and other factors during the movement of the scanning table <NUM> may be corrected to reconstruct a more accurate PET image.

Similarly, the statistic information of the nuclide decay may also be obtained by extracting nuclide decay information at the corresponding time point from the PET scan data unit <NUM> based on the position information of the scanning table <NUM> and by normalizing the nuclide decay within the axial FOV of the detector <NUM>. That is, due to the radioactive decay of the nuclide, the nuclide decay information extracted based on the position information of the scanning table <NUM> at each time point may be normalized, to avoid a deviation that the reconstructed image may have due to the nuclide decay.

In <NUM>, an axial count correction may be performed based on the statistic information of the scanning table position and the statistic information of the nuclide decay within the axial FOV, and the reconstructed PET image, to obtain a corrected PET image of the phantom within the entire axial FOV.

After operation <NUM>, in which the reconstructed PET image may be obtained, the reconstructed PET image may be axially corrected by further combining the statistic information of the scanning table position and the statistic information of the nuclide decay within the axial FOV to eliminate the image differences due to the acceleration, deceleration of the scanning table <NUM> and other factors, and further to avoid the impact of the nuclide decay on the reconstructed image. Thus, a more accurate corrected reconstructed PET image of the phantom within the entire axial FOV may be obtained. In this way, the reconstructed PET image may be analyzed to further obtain the performance and working condition of the PET system <NUM>. For example, the axial uniformity of the PET system <NUM> may be verified based on the reconstructed PET image.

In some embodiments, the PET image may be reconstructed by using the data of the phantom collected by all detector units, so that the quality analysis may be performed based on the generated reconstructed PET image. In other embodiments, the normalizing factor of the detector efficiency may be generated by using the data of the phantom obtained by the PET data collection method described above.

In some embodiments, there may be tens of thousands of detector units in the detector <NUM> of the PET system <NUM>. The detection efficiency of the detector units may be inconsistent due to their respective geometric positions and performance differences. The performance differences of the detector units may be due to factors including different luminous efficiencies of crystal strips of the detector units, different coupling extents between the crystal strips and photomultiplier tubes in the detector units, and different angles of the crystal strips with respect to coincidence lines. The inconsistency of the detection efficiency of the detector units may introduce artifacts in the PET image reconstruction. Therefore, to accurately model the detector units and to obtain a satisfactory image quality, the detection efficiencies of the detector units of the detector <NUM> may be normalized. The normalization of the detection efficiencies may also be referred to as a normalizing calibration. The normalizing calibration method of the detector efficiency may be illustrated elsewhere in the present disclosure. In some embodiments, the normalizing calibration method of the detector efficiencies may include a plurality of factors (e.g., a plurality of normalizing factors), which may be stored in a computer in a file format. In some embodiments, while a patient is scanned by the PET system <NUM>, the normalizing factor may be applied to a measured value of the detector <NUM> to perform the normalizing calibration of the detector efficiency.

<FIG> is a flowchart illustrating an exemplary process for controlling a phantom of a medical imaging device with a first motion controller according to an embodiment of the present disclosure. Refer to <FIG>, in <NUM>, a phantom may be mounted on a phantom controlling device (or referred to as the second moving mechanism). In <NUM>, the phantom controlling device may be mounted on the scanning table <NUM> to cause the phantom to insert into the detection region <NUM>. In <NUM>, the phantom may be controlled to move inside the detection region <NUM> via the phantom controlling device and the scanning table <NUM>. In some embodiments, the phantom controlling device may include a moving mechanism that may drive the phantom to move along the X direction inside the detection region <NUM>. In some embodiments, the scanning table <NUM> may include a scanning-table driving mechanism (or referred to as the first moving mechanism) that may drive the scanning table <NUM> to move along a forward-backward (e.g., the Y direction shown in <FIG>) and/or an up-down direction (e.g., the Z direction shown in <FIG>). The moving mechanism may move along the Y direction and/or the Z direction inside the detection region <NUM> based on the effect of the scanning-table driving mechanism. In other embodiments, the phantom may be controlled to move circumferentially inside the detection region <NUM> via the phantom controlling device and the scanning table <NUM>.

<FIG> is a schematic diagram illustrating a phantom controlling device (or referred to as the first phantom controlling device, or the second moving mechanism) according to an embodiment of the present disclosure. Referring to <FIG>, the phantom controlling device may include a phantom bearing <NUM> and a moving mechanism. The moving mechanism may include a support plate <NUM>, a first rotation wheel <NUM> and a second rotation wheel <NUM> which are installed at both ends of the support plate <NUM>, a transmission belt <NUM> sheathed on the first rotation wheel <NUM>, and the second rotation wheel <NUM>. The transmission belt <NUM> may extend along the X direction. The phantom <NUM> may be connected to the transmission belt <NUM> via the phantom bearing <NUM>, and the first rotation wheel <NUM> and/or the second rotation wheel <NUM> may be connected to a driver <NUM> (e.g., a first driver). When the driver <NUM> is started, the first rotation wheel <NUM> and the second rotation wheel <NUM> may drive the transmission belt <NUM> to move along the X direction and the phantom <NUM> may be moved with the transmission belt <NUM> along the direction. The phantom <NUM> may be driven to reciprocate along the direction. In one embodiment, the first rotation wheel <NUM> and the second rotation wheel <NUM> may be mounted on the support plate <NUM> via a supporting frame, and the transmission belt <NUM> and the first rotation wheel <NUM> and the second rotation wheel <NUM> may be gear-driven. In another embodiment, the moving mechanism may include a guide structure, and the phantom <NUM> may be connected to the guide structure via the phantom bearing <NUM> (e.g., a connecting plate) and may move along the guide structure. In a specific embodiment, the guide structure may be a guiding mechanism <NUM> installed on the support plate <NUM>, and the guiding mechanism <NUM> may be installed on one side of the transmission belt <NUM> and may extend along the X direction. The guiding mechanism <NUM> may be installed with a slider block <NUM>. The phantom <NUM> may be mounted on the connecting plate <NUM>. One end of the connecting plate <NUM> may be connected to the slider block <NUM> and the other end thereof may be connected to the transmission belt <NUM>. The phantom <NUM> may move along the guiding mechanism <NUM>, along with the transmission belt <NUM>.

<FIG> is a schematic diagrams illustrating a phantom controlling device (or referred to as a first phantom controlling device, or the second moving mechanism) according to another embodiment of the present disclosure. Referring to <FIG>, the phantom controlling device may include a phantom bearing <NUM> (e.g., a connecting plate) and a moving mechanism. The moving mechanism may include a support plate <NUM> and a screw shaft <NUM> installed on the support plate <NUM>. The screw shaft <NUM> may extend along the X direction (e.g., a direction perpendicular to the axial direction of the detection region <NUM>). The phantom <NUM> may be mounted on a support base <NUM> via the phantom bearing <NUM>, the support base <NUM> may be sheathed on the screw shaft <NUM>, and the end of the screw shaft <NUM> may be connected to a driver <NUM> (or referred to as a second driver). When the driver <NUM> is started, the screw shaft <NUM> may drive the support base <NUM> and the phantom <NUM> to reciprocate along the X direction. In one embodiment, the screw shaft <NUM> may be mounted on the support plate <NUM> via the supporting frame. In another embodiment, the moving mechanism may include a guide structure, and the phantom <NUM> may be connected to the guide structure via the phantom bearing <NUM> and may move along the guide structure. In a specific embodiment, the guide structure may be a guiding mechanism <NUM> installed on the support plate <NUM>. The guiding mechanism <NUM> may be installed on one side of the screw shaft <NUM> and may extend along the X direction. A slider block <NUM> may be installed on the guiding mechanism <NUM>. The phantom <NUM> may be mounted on the connecting plate <NUM>. One end of the connecting plate <NUM> may be connected to the slider block <NUM>, while the other end thereof may be connected to the support base <NUM>. The phantom <NUM> may move along the guiding mechanism <NUM> with the rotation of the screw shaft <NUM>. In some embodiments, the guiding mechanism <NUM> may be installed beneath the screw shaft <NUM> and the support base <NUM> may be mounted on the guiding mechanism <NUM>. A groove may be installed on the surface of the support base <NUM> facing the guiding mechanism <NUM>, so that the support base <NUM> may slide along the guiding mechanism <NUM>,.

The moving mechanism may drive the phantom <NUM> to move along the X direction inside the detection region <NUM>. The movement may be of a uniform or non-uniform velocity, may be a continuous movement within a certain period of time, or may be a discontinuous movement separated by at least one time interval. The present disclosure is not intended to limit the scope of the mode in which the moving mechanism may drive the phantom <NUM> to move along the X direction inside the detection region <NUM>.

<FIG> is a schematic diagrams illustrating a phantom controlling device according to another embodiment of the present disclosure. As illustrated, the phantom controlling device may include a support plate <NUM>, screw shaft <NUM>, support base <NUM>, driver <NUM>, guiding mechanism <NUM>, slider block <NUM> and a connecting plate <NUM>. The function of the phantom controlling device may be illustrated in <FIG> and/or <FIG>. The configuration of the connecting plate <NUM> and the manner in which the phantom <NUM> is located in the connecting plate <NUM> may be different with respect to those illustrated in <FIG> and/or <FIG>.

The phantom <NUM> may be a point phantom, a line phantom, a rod phantom, etc. As shown in <FIG> and <FIG>, the phantom may be a rod phantom. As shown in <FIG>, the phantom <NUM> may be a point phantom and the point phantom <NUM> may be installed at an end of a connecting plate <NUM>. In one embodiment of the disclosure, the angle <NUM> between the extension direction of the phantom on the connecting plate <NUM> and the extension direction of the moving mechanism <NUM> may be any angle greater than zero, such as <NUM> degrees, <NUM> degrees, <NUM> degrees or <NUM> degrees. In another embodiment, the phantom <NUM> and the connecting plate <NUM> may be detachably connected to facilitate the installment or replacement of the phantom <NUM>. In other embodiments, the phantom <NUM> (e.g., a rod phantom) or the connecting plate <NUM> may be connected to a rotation mechanism (not shown). When the phantom is required for scanning, the rotation mechanism may be operated so that the angle <NUM> between the extension direction of the phantom 1611and the extension direction of the moving mechanism <NUM> may be greater than zero. When the phantom is not required, the phantom may be rotated so that the extension direction of the phantom may be the same as that of the moving mechanism, so that the phantom and the moving mechanism may be accommodated in the shield cover for storage.

The motion control of the phantom in the Yl direction as shown in <FIG> or <FIG> may be achieved by the above-described phantom controlling device. The phantom controlling device may be placed on the scanning table <NUM>. In some embodiments, the phantom controlling device may be placed on the top surface of the scanning table <NUM> near a frame (e.g., the gantry <NUM> of the PET system <NUM>). The support plate <NUM> may be inserted directly into a head support socket of the scanning table <NUM> to be fixed onto it. The phantom <NUM> mounted on the phantom controlling device may be inserted into the detection region <NUM> by adjusting the position of the scanning table <NUM>. The phantom controlling device may drive the phantom <NUM> to move along the X direction (e.g., a direction perpendicular to the axial direction of the detection region <NUM>) inside the detection region <NUM>. The position of the phantom <NUM> in a direction perpendicular to the Z direction of the detection region <NUM> may also be adjusted to meet the requirements for precise positioning of the phantom <NUM>. The driver may also be adjusted to meet the requirements to achieve a certain motion trail of the phantom <NUM>. For example, in the PET resolution test, the above-described phantom controlling device may position the phantom <NUM> at different positions to meet the requirements for precise positioning of the phantom <NUM>. In addition, the phantom controlling device may drive a rod phantom <NUM> to move along the X direction to simulate a plane phantom.

In some embodiments of the present disclosure, the scanning table <NUM> may include a scanning table driving mechanism that may drive the scanning table <NUM> to move along the Z direction and/or the Y direction. The scanning table driving mechanism may drive the moving mechanism to move inside the detection region <NUM>. The movement of the moving mechanism may be of a uniform or non-uniform velocity, may be a continuous movement within a certain period of time, or may be a discontinuous movement separated by at least one time interval. The present disclosure is not intended to limit the scope of the mode in which the scanning table moving mechanism drive the moving mechanism.

The phantom may move in a certain direction, or in a certain plane while driven by the phantom controlling device and/or the scanning table <NUM>. For example, the phantom controlling device (or the scanning table <NUM>) may drive the phantom to move along the X direction or the Y direction. As another example, the scanning table <NUM> may drive the phantom controlling device to move along the Y direction and/or the Z direction. As another example, the phantom controlling device may drive the phantom to move in the X direction, while the scanning table <NUM> may drive the phantom to move in the Y direction, resulting in a movement in the X-Y plane of the phantom. The movement trail of the phantom may be regular or irregular in shape. For example, the movement trail of the phantom may be circular.

<FIG> is a schematic diagram illustrating a circular movement trail of the phantom according to some embodiments of the present disclosure.

Referring to <FIG>, the phantom <NUM> may move in a circular trail <NUM> on the X-Y plane, around the Z axis. The phantom <NUM> may move in a circular trail <NUM> at a uniform velocity when the equation (<NUM>) to equation (<NUM>) are satisfied: <MAT> <MAT> <MAT> <MAT> wherein v denotes the uniform velocity of the phantom <NUM>, and w denotes an angular velocity of the phantom <NUM>, and θ denotes an angle between the axis of the phantom <NUM> and the Z direction. Vx denotes a velocity of the phantom in the X direction. The phantom <NUM> may be driven by the moving mechanism. Vy denotes a velocity of the phantom in the Y direction. In some embodiments, a vertical lifting mechanism in the scanning table <NUM> may be utilized to drive the phantom <NUM> to move in the Y direction.

The movement of the scanning table <NUM> and the phantom <NUM> controlling device may be of a uniform or non-uniform velocity. In some embodiments, to obtain a circular movement of the phantom <NUM>, the speed of the phantom <NUM> may be precisely controlled to be uniform during its movement. In some embodiments, the scanning table driving mechanism and/or the phantom controlling device may communicate with a computer to control the movement of the phantom <NUM> together. The scanning table driving mechanism and/or the phantom controlling device may drive the phantom <NUM> to move under an instruction sent out by the computer. In some embodiments, a movement trail may be input into the computer based on which one or more instructions may be generated. The computer may further send the generated instructions to the phantom controlling device and/or the scanning table driving mechanism to control the phantom <NUM> to move in the movement trail that has been input to the computer.

<FIG> is a schematic diagram illustrating a phantom controlling device (or referred to as a second phantom controlling device, or the second motion controller) according to some embodiments of the present disclosure. As shown in <FIG>, the phantom controlling device may include a first shield <NUM>, a second shield <NUM> and a phantom <NUM>. The phantom <NUM> (e.g., a point phantom, a line phantom, a rod phantom, etc.) may be installed in a radiation shielding space formed by the first shield <NUM> and the second shield <NUM> and may stretch out or retract into the second shield <NUM>. When a subject (e.g., a human body) is scanned by the PET system <NUM>, the phantom <NUM> may retract into the second shield <NUM> to prevent the subject from being affected by the radiation from the phantom <NUM>. When the PET system <NUM> is to be tested or calibrated, as shown in <FIG>, radiations of the phantom may be required to accomplish the test or calibration. Thus, the phantom <NUM> may stretch out from the second shield <NUM> and extend into the detection region <NUM> to radiate the detectors of the PET system.

The phantom controlling device may be mounted beneath the scanning table. For example, the phantom controlling device may be mounted on the bottom surface of the scanning table <NUM> that is close to the gantry <NUM>.

<FIG> is a schematic diagram illustrating an internal structure of a first shield <NUM> according to some embodiments of the present disclosure. As shown in <FIG>, the first shield <NUM> has a first groove extending along the Z direction. A screw shaft <NUM> may be installed in the groove. The phantom <NUM> may be installed on a slider block <NUM> that is sheathed on the crew shaft <NUM>. One end of the crew shaft <NUM> may be connected to a first motor <NUM>, and the first motor <NUM> may be installed at one end of the first shield <NUM>. The first motor <NUM> may drive the crew shaft <NUM> to drive the phantom <NUM> to move via the slider block <NUM>. In some embodiments of the present disclosure, a guide structure (e.g., a guide trail) may be mounted on at least one surface of the first groove, along which the slider block <NUM> may slide. The phantom controlling device may further comprise a phantom driving device. The phantom driving device may include a rotation shaft <NUM> and a rotation arm <NUM>. One end of the rotation shaft <NUM> may connect to a second motor <NUM>. The second motor <NUM> may be installed on the slider block <NUM>, and may slide along the screw shaft <NUM> with the slider block <NUM>. For example, the second motor <NUM> may locate between the first shield <NUM> and the second shield <NUM>. The phantom <NUM> may be connected to the rotation arm <NUM>. The second motor <NUM> may drive the rotation shaft <NUM> to drive the phantom <NUM> to rotate via the rotation arm <NUM>. In some embodiments of the disclosure, the rotation arm <NUM> may be in a crank structure.

<FIG> is a schematic diagram illustrating a second shield according to some embodiments of the present disclosure. <FIG> is a cross-sectional view of the second shield according to some embodiments of the present disclosure. As shown in <FIG>, the second shield <NUM> may have, on its surface facing the phantom <NUM>, a second groove <NUM> that extends along the Z direction. The end of the second groove, which faces the Y-Z plane, may include an opening. The second groove <NUM> may provide the phantom <NUM> with a moving passage. The motor <NUM> may drive the phantom <NUM> to stretch out or retract into the second shield <NUM> through the second groove <NUM>. A third groove <NUM>, which may be configured to accommodate the phantom <NUM>, may locate on a surface of the second groove <NUM>. In some embodiments of the present disclosure, the third groove <NUM> and the second groove <NUM> may be on different planes. The third groove may include two closed ends. The two ends of the third groove may be along the Z direction. The phantom <NUM> may retract into the second shield <NUM> and may be accommodated in the third groove <NUM>, while the human body is scanned by the PET system <NUM>.

To calibrate the PET system <NUM> with the phantom <NUM>, the first motor <NUM> may drive the phantom <NUM> to stretch out from the second shield <NUM> to extend into the detection region <NUM>. The second motor <NUM> may drive the phantom <NUM> to rotate at a uniform velocity inside the detection region <NUM> to irradiate the detector units within the detecting region <NUM>. When the calibration of the PET system is finished, the first motor <NUM> may drive the phantom <NUM> to retract into the second shield <NUM>. The second motor <NUM> may drive the phantom <NUM> to enter a space formed by the third groove <NUM> in the second shield <NUM>. The space may shied radiation emitted by the phantom <NUM>. In some embodiments, the phantom controlling device may further include a fixing device for fixing the phantom controlling device on the bottom surface of the scanning table <NUM>. The fixing device may include a buckle, a nut, or the like, or any combination thereof.

In some embodiments, the scanning table <NUM> may further include a lifting device, through which the height of the scanning table <NUM> may be adjusted. When the PET device is calibrated using the phantom, the height of the scanning table <NUM> may be adjusted to coincide the axis of the rotation shaft <NUM> and the axis of the ring of the FOV.

It should be noted that the flowchart described above is provided for the purposes of illustration, not intended to limit the scope of the present disclosure. For persons having ordinary skills in the art, multiple variations and modifications may be reduced to practice in the light of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure. For example, the phantom controlling device may not only be used to calibrate a single modality imaging system such as the PET system <NUM> as illustrated, a Computed Tomography (CT) system, a MR (Magnetic Resonance) system, or the like, but may also be used to calibrate a multi-modality imaging system such as PET-CT device, PET-MR device, etc..

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.

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 object 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.

In some embodiments, the numbers expressing quantities or properties used to describe and claim certain embodiments of the application are to be understood as being modified in some instances by the term "about," "approximate," or "substantially. " For example, "about," "approximate," or "substantially" may indicate ±<NUM>% variation of the value it describes, unless otherwise stated. Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

Claim 1:
A method implemented on an imaging device (<NUM>) having at least one processor (<NUM>) and storage (<NUM>) for medical imaging, comprising:
moving, by a motion controller (<NUM>), a phantom along an axis of a scanner (<NUM>) to a plurality of phantom positions;
acquiring, by a detector (<NUM>) of the imaging device (<NUM>), a first set of PET data relating to the phantom at the plurality of phantom positions, wherein the length of an axis of the phantom is shorter than the length of an axis of the scanner (<NUM>), and at least one of the plurality of phantom positions is inside a bore of the scanner (<NUM>);
acquiring calibration data that comprises nuclide decay corresponding to the axis of the scanner (<NUM>);
reconstructing a PET image based at least in part on the first set of PET data; and
correcting the PET image based on the calibration data and the plurality of phantom positions, comprising:
obtaining statistic data of phantom position by normalizing the plurality of phantom positions;
obtaining statistic data of nuclide decay by normalizing nuclide decay corresponding to the axis of the scanner (<NUM>); and
correcting the PET image based on the statistic data of phantom position and the statistic data of nuclide decay.