WO2023109064A1 - 梯度灵敏度校正方法和系统 - Google Patents

梯度灵敏度校正方法和系统 Download PDF

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WO2023109064A1
WO2023109064A1 PCT/CN2022/100376 CN2022100376W WO2023109064A1 WO 2023109064 A1 WO2023109064 A1 WO 2023109064A1 CN 2022100376 W CN2022100376 W CN 2022100376W WO 2023109064 A1 WO2023109064 A1 WO 2023109064A1
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phantom
size
mri
gradient sensitivity
fitting
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PCT/CN2022/100376
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English (en)
French (fr)
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周建帆
邢斌
雷红霞
翟人宽
邢峣
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武汉联影生命科学仪器有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass

Definitions

  • This specification relates to the field of magnetic resonance imaging (magnetic resonance imaging, MRI), in particular to a gradient sensitivity correction method and system.
  • a spherical phantom is mostly used, and the gradient sensitivity of the MRI equipment is corrected by using the consistency of the dimensions of the coronal, sagittal, and transverse planes at the center of the spherical phantom.
  • the gradient sensitivity of the MRI equipment is corrected by using the consistency of the dimensions of the coronal, sagittal, and transverse planes at the center of the spherical phantom.
  • there is a very high precision requirement for the positioning of the phantom and it is necessary to make the center of the phantom coincide with the center of the MRI equipment as much as possible.
  • the traditional method for calibrating the gradient sensitivity of MRI equipment has the problems of low calibration accuracy and complicated operation.
  • the method can be executed by at least one processor.
  • the method may include acquiring a three-dimensional image of the phantom, the three-dimensional image is collected by MRI equipment, and the phantom has a known actual size on the target axis; fitting the three-dimensional image to determine the fitting size of the phantom on the target axis ; and based on the fitted size and the actual size, correcting the gradient sensitivity of the MRI device.
  • the phantom may be a spherical phantom.
  • the phantom may be a non-spherical phantom that may be positioned based on the target axis.
  • performing fitting based on the three-dimensional image, determining the fitting size of the phantom on the target axis may include determining at least one central section based on the three-dimensional image; and determining the phantom on the target axis based on the at least one central section fit size.
  • correcting the gradient sensitivity of the MRI device may include determining a difference between the fitted size and the actual size; determining whether the difference satisfies a preset condition; conditions, correcting for the gradient sensitivity of the MRI equipment.
  • the method may further include verifying the corrected gradient sensitivity.
  • verifying the corrected gradient sensitivity may include acquiring a three-dimensional verification image of the phantom, and the three-dimensional verification image is collected by an MRI device with the corrected gradient sensitivity; the verified fit dimensions on the axis; determine the verified difference between the verified fitted size and the actual size; and based on the verified difference, verify the corrected gradient sensitivity.
  • the MRI apparatus may include a cantilever bed on which the phantom may be placed.
  • the target axes may include three coordinate axes corresponding to a coordinate system established with the central position of the magnet imaging area of the MRI equipment as the origin and three orthogonal axes in space as the three axis directions.
  • the system may include a storage device storing computer instructions; a processor connected to the storage device.
  • the processor when executing the computer instructions, causes the system to perform the operations described below.
  • the operation may include acquiring a three-dimensional image of the phantom, the three-dimensional image is collected by MRI equipment, and the phantom has a known actual size on the target axis; fitting the three-dimensional image to determine the fitting size of the phantom on the target axis ; and based on the fitted size and the actual size, correcting the gradient sensitivity of the MRI device.
  • One of the embodiments of the present specification provides a computer-readable storage medium, the storage medium stores computer instructions, and when a computer reads the computer instructions, the computer executes a gradient sensitivity correction method.
  • the method may include acquiring a three-dimensional image of a phantom, the three-dimensional image being collected by an MRI device, the phantom having a known actual size on the target axis; fitting the three-dimensional image to determine the phantom a fitted dimension on the target axis; and based on the fitted dimension and the actual dimension, correcting for gradient sensitivity of the MRI apparatus.
  • the system may include an acquisition module, a determination module and a correction module.
  • the acquisition module can be used to acquire a three-dimensional image of a phantom, which is acquired by an MRI device, and the phantom has a known actual size on the target axis.
  • the determining module can be used to fit the three-dimensional image, and determine the fitting size of the phantom on the target axis.
  • a correction module may be used for correcting the gradient sensitivity of the MRI device based on the fitted size and the actual size.
  • FIG. 1 is a schematic diagram of an application scenario of an exemplary MRI system according to some embodiments of the present specification
  • FIG. 2 is a schematic diagram of an exemplary computing device according to some embodiments of the present application.
  • FIG. 3 is a block diagram of an exemplary processing device according to some embodiments of the present specification.
  • FIG. 4 is a flow chart of an exemplary gradient sensitivity correction process according to some embodiments of the present specification.
  • FIG. 5 is a flow chart of an exemplary process for calibrating gradient sensitivity according to some embodiments of the present specification
  • FIG. 6 is a flow chart of an exemplary process for verifying gradient sensitivity according to some embodiments of the present specification
  • Fig. 7 is a schematic diagram of an exemplary process for calibrating gradient sensitivity according to some embodiments of the present specification.
  • FIG. 8 is a schematic illustration of an exemplary cylindrical phantom, according to some embodiments of the present specification.
  • system means for distinguishing different components, elements, parts, parts or assemblies of different levels.
  • the words may be replaced by other expressions if other words can achieve the same purpose.
  • the magnetic resonance imaging system may include a single modality imaging system and/or a multimodal imaging system.
  • Unimodal imaging systems may include, for example, MRI systems.
  • Exemplary MRI systems may include superconducting magnetic resonance imaging systems, non-superconducting magnetic resonance imaging systems, and the like.
  • Multimodal imaging systems may include, for example, computed tomography-magnetic resonance imaging (MRI-CT) systems, positron emission tomography-magnetic resonance imaging (PET-MRI) systems, single photon emission computed tomography-magnetic resonance imaging (SPECT-MRI) system, digital subtraction angiography-magnetic resonance imaging (DSA-MRI) system, etc.
  • MRI-CT computed tomography-magnetic resonance imaging
  • PET-MRI positron emission tomography-magnetic resonance imaging
  • SPECT-MRI single photon emission computed tomography-magnetic resonance imaging
  • DSA-MRI digital subtraction angiography-magnetic resonance imaging
  • Fig. 1 is a schematic diagram of an application scenario of an exemplary MRI system 100 according to some embodiments of the present specification.
  • the MRI system 100 may include an MRI scanner 110 , a network 120 , one or more terminals 130 , a processing device 140 and a storage device 150 .
  • Components in MRI system 100 may be connected in one or more of a variety of ways.
  • MRI scanner 110 may be connected to processing device 140 via network 120 .
  • the MRI scanner 110 may be directly connected to the processing device 140 as indicated by the dashed double-headed arrow connecting the MRI scanner 110 and the processing device 140 .
  • the storage device 150 may be connected to the processing device 140 directly or through the network 120 .
  • terminal 130 may be connected to processing device 140 either directly (as indicated by the dashed bi-directional arrow connecting terminal 130 and processing device 140) or through network 120.
  • the MRI scanner 110 may scan an object within its detection region and generate data related to the object (eg, echo signals or MR signals associated with the object).
  • MRI scanner 110 may scan an object by executing one or more protocols.
  • objects may include human bodies, animals, man-made objects (eg, phantoms), and the like.
  • an object may include a specific part, organ and/or tissue of a human body, an animal, or a phantom.
  • an object may include a head, brain, neck, body, shoulders, arms, chest, heart, stomach, blood vessels, soft tissue, knees, feet, etc., or any combination thereof.
  • MRI scanner 110 may comprise a closed-bore MRI scanner or an open-bore MRI scanner.
  • the MRI scanner 110 may include a permanent magnet magnetic resonance scanner, a superconducting electromagnet magnetic resonance scanner, a resistive electromagnet magnetic resonance scanner, and the like.
  • the MRI scanner 110 may include a high-field MRI scanner, a mid-field MRI scanner, a low-field MRI scanner, etc., depending on the strength of the magnetic field.
  • the MRI scanner 110 may include a rail bed MRI scanner, a cantilever MRI scanner, etc., depending on how the couch moves.
  • cantilever MRI scanners may include animal MRI scanners, infant MRI scanners, and the like.
  • the X axis, Y axis and Z axis shown in FIG. 1 may form an orthogonal coordinate system.
  • the X and Z axes shown in Figure 1 may be horizontal and the Y axis may be vertical.
  • the positive X direction along the X axis shown in FIG. 1 may be from the right side to the left side of the MRI scanner 110 seen from a direction facing the front of the MRI scanner 110, and the positive direction along the Y axis shown in FIG.
  • the Y direction may be from the bottom to the top of the MRI scanner 110, and the positive Z direction along the Z axis shown in FIG.
  • the MRI scanner 110 may include, for example, a main magnet, gradient coils (also referred to as spatially encoded coils), radio frequency (RF) coils, and the like.
  • RF radio frequency
  • the main magnet can generate a first magnetic field (also referred to as the main magnetic field), which can act on an object (also referred to as the object) exposed to the main magnetic field.
  • the main magnet may include an aperture for placing an object.
  • the main magnet can also control the homogeneity of the generated main magnetic field. For example, some shim coils may be in the main magnet. The shim coils placed in the gap of the main magnet can compensate the inhomogeneity of the magnetic field of the main magnet.
  • Gradient coils may be located within the main magnet.
  • the gradient coils can generate a second magnetic field (or called a gradient magnetic field, including gradient magnetic fields Gx, Gy and Gz).
  • the second magnetic field can be superimposed on and distort the main magnetic field generated by the main magnet so that the magnetic orientation of the subject's protons can change according to their position within the gradient magnetic field, thereby encoding spatial information into the imaged subject's Magnetic resonance (MR) signals (eg, echo signals) generated by the region.
  • MR Magnetic resonance
  • the gradient coils may include X coils (for example, for generating a gradient magnetic field Gx corresponding to the X direction), Y coils (for example, for generating a gradient magnetic field Gy corresponding to the Y direction), and/or Z coils (for example, for generating corresponds to the gradient magnetic field Gz) in the Z direction (not shown in FIG. 1 ).
  • the Z coil may be based on a circular (Maxwell) coil design, while the X and Y coils may be based on a saddle (Golay) coil configuration.
  • Three sets of coils can generate three different magnetic fields for position encoding.
  • Gradient coils can allow spatial encoding of MR signals for image construction. In some cases, three sets of gradient coils may be energized and thus three gradient magnetic fields may be generated.
  • an RF coil may be located within the main magnet and function as a transmitter, receiver, or both.
  • an RF coil can generate an RF signal.
  • the RF signal can provide a third magnetic field that can be used to generate an MR signal related to the region of the imaged object.
  • the third magnetic field may be perpendicular to the main magnetic field.
  • the RF coil may be responsible for detecting MR signals. After excitation, the MR signal generated by the subject can be sensed by the RF coil.
  • Network 120 may include any suitable network that may facilitate the exchange of information and/or data for MRI system 100 .
  • one or more components of the MRI system 100 e.g., the MRI scanner 110, the terminal 130, the processing device 140, or the storage device 150
  • processing device 140 may acquire object-related data from MRI scanner 110 via network 120 .
  • the network 120 may be a wired network or a wireless network, etc. or any combination thereof.
  • Network 120 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., 11 networks, Wi-Fi networks, etc.), cellular networks (e.g., Long Term Evolution (LTE) networks), frame relay networks, virtual private networks (“VPNs”), satellite networks, telephone networks, routers, hubs, switches, servers computer and/or any combination thereof.
  • 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., 11 networks, Wi-Fi networks, etc.
  • cellular networks e.g., Long Term Evolution (LTE) networks
  • frame relay networks e.g.,
  • network 120 may include a cable network, a wired network, a fiber optic network, a telecommunications network, an intranet, a wireless local area network (WLAN), a metropolitan area network (MAN), a public switched telephone network (PSTN), a Bluetooth network, ZigBee network, near field communication (NFC) network, etc., or any combination thereof.
  • network 120 may include one or more network access points.
  • network 120 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 MRI system 100 may connect to network 120 to exchange data and/or information.
  • Terminals 130 include mobile devices 131, tablets 132, laptops 133, etc., or any combination thereof.
  • the mobile device 131 may include a smart home device, a wearable device, a smart mobile device, a virtual reality device, an augmented reality device, etc., or any combination thereof.
  • smart home devices may include smart lighting devices, smart electrical control devices, smart monitoring devices, smart TVs, smart cameras, walkie-talkies, etc., or any combination thereof.
  • a wearable device may include a smart bracelet, smart footwear, a pair of smart glasses, a smart helmet, a smart watch, smart clothing, a smart backpack, a smart accessory, etc., or any combination thereof.
  • a smart mobile device may include a smart phone, a personal digital assistant (PDA), a gaming device, a navigation device, a point of sale (POS), etc., or any combination thereof.
  • the virtual reality device and/or the augmented virtual reality device may include a virtual reality helmet, virtual reality glasses, virtual reality goggles, augmented reality helmet, augmented reality glasses, augmented reality goggles, etc., or any combination thereof.
  • virtual reality devices and/or augmented reality devices may include Google Glass TM , Oculus Rift TM , Hololens TM , Gear VR TM , and the like.
  • terminal 130 may operate MRI scanner 110 and/or processing device 140 remotely.
  • terminal 130 may operate MRI scanner 110 and/or processing device 140 via a wireless connection. In some embodiments, terminal 130 may receive information and/or instructions input by a user, and transmit the received information and/or instructions to MRI scanner 110 or processing device 140 via network 120 . In some embodiments, terminal 130 may receive data and/or information from processing device 140 . In some embodiments, terminal 130 may be part of processing device 140 . In some embodiments, terminal 130 may be omitted.
  • Processing device 140 may process data and/or information obtained from MRI scanner 110 , terminal 130 and/or storage device 150 .
  • the processing device 140 may obtain the actual size and the fitted size of the phantom, and based on the actual size and the fitted size, correct the gradient sensitivity of the MRI scanner 110 .
  • processing device 140 may be a single server or a group of servers. Server groups can be centralized or distributed.
  • processing device 140 may be local or remote.
  • processing device 140 may access information and/or data stored in or obtained by MRI scanner 110 , terminal 130 and/or storage device 150 via network 120 .
  • the processing device 140 can be directly connected to the MRI scanner 110 (as shown by the bidirectional arrow in the dashed line connecting the processing device 140 and the MRI scanner 110 in FIG. 1 ), the terminal 130 (as shown in FIG. 1 connecting the processing device 140 and Terminal 130 (indicated by the double-headed arrow in the dotted line) and/or storage device 150 to access stored or retrieved information and/or data.
  • the processing device 140 may be implemented on a cloud platform.
  • the cloud platform can include private clouds, public clouds, hybrid clouds, community clouds, distributed clouds, internal clouds, multi-layer clouds, etc., or any combination thereof.
  • processing device 140 may be implemented on computing device 200 having one or more components shown in FIG. 2 of this application.
  • processing device 140 or a portion of processing device 140 may be integrated into MRI scanner 110 .
  • Storage device 150 may store data and/or instructions.
  • storage device 150 may store data acquired from MRI scanner 110 , terminal 130 and/or processing device 140 .
  • the storage device 150 can store data such as a three-dimensional image of the phantom, actual size, fitting size, and the like.
  • storage device 150 may store data and/or instructions that processing device 140 may execute or be used to perform the exemplary methods described herein.
  • storage device 150 may store instructions for processing device 140 to execute to correct gradient sensitivity.
  • the storage device 150 includes a mass storage device, a removable storage device, a volatile read-write memory, a read-only memory (ROM), etc., or any combination thereof.
  • Exemplary mass storage may include magnetic disks, optical disks, solid state drives, and the like.
  • Exemplary removable storage may include flash drives, floppy disks, compact disks, memory cards, compact disks, magnetic tape, and the like.
  • Exemplary volatile read-write memory may include random access memory (RAM).
  • Exemplary RAMs may include dynamic RAM (DRAM), double data rate synchronous dynamic RAM (DDRSDRAM), static RAM (SRAM), thyristor RAM (T-RAM), and zero capacitance RAM (Z-RAM).
  • Exemplary ROMs may include mask ROM (MROM), programmable ROM (PROM), erasable programmable ROM (PEROM), electrically erasable programmable ROM (EEPROM), compact disc ROM (CD-ROM), and digital Universal disk ROM, etc.
  • the storage device 150 can be implemented on a cloud platform.
  • the cloud platform may include private clouds, public clouds, hybrid clouds, community clouds, distributed clouds, internal clouds, multi-layer clouds, etc., or any combination thereof.
  • storage device 150 may be connected to network 120 to communicate with one or more components of MRI system 100 (eg, MRI scanner 110, processing device 140, terminal 130, etc.). One or more components of MRI system 100 may access data or instructions stored in storage device 150 via network 120 . In some embodiments, storage device 150 may be directly connected to or in communication with one or more components of MRI system 100 (eg, MRI scanner 110, processing device 140, terminal 130, etc.). In some embodiments, storage device 150 may be part of processing device 140 .
  • MRI system 100 may also include one or more power supplies (not shown in FIG. ).
  • a computing device 200 is provided. An internal structural diagram of the computing device 200 may be shown in FIG. 2 .
  • Computing device 200 may include a processor, memory, communication interface, display screen, and input device connected through a system bus. Among them, the processor of the computing device 200 may be used to provide computing and control capabilities. For example, the gradient sensitivity correction method shown in some embodiments of the present application can be implemented.
  • the memory of the computing device 200 may include a non-volatile storage medium, an internal memory.
  • the non-volatile storage medium can store an operating system and computer programs.
  • the internal memory can provide an environment for the operation of the operating system and computer programs in the non-volatile storage medium.
  • the communication interface of the computing device 200 may be used for wired or wireless communication with an external terminal, and the wireless mode may be implemented through WIFI, operator network, NFC (Near Field Communication) or other technologies.
  • the computer program is executed by the processor, the gradient sensitivity correction method can be realized.
  • the display screen of computing device 200 may be a liquid crystal display screen or an electronic ink display screen.
  • the input device of the computing device 200 may be a touch layer covered on the display screen, a button, a trackball or a touch pad provided on the casing of the computing device 200, or an external keyboard, touch pad or mouse.
  • FIG. 2 is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation to the computing equipment applied to the MRI system of the solution of the application.
  • the specific computing equipment More or fewer components than shown in the figures may be included, or certain components may be combined, or have a different arrangement of components.
  • FIG. 3 is a block diagram of an exemplary processing device 140 shown in accordance with some embodiments of the present specification.
  • the processing device 140 may include an acquisition module 310 , a determination module 320 and a correction module 330 .
  • the acquiring module 310 can be used to acquire a three-dimensional image of the phantom.
  • Three-dimensional images can be acquired using MRI equipment.
  • the phantom may have known actual dimensions on the target axis. For more information on acquiring a three-dimensional image, refer to step 402 in FIG. 4 and related descriptions.
  • the determining module 320 can be used to fit the three-dimensional image, and determine the fitting size of the phantom on the target axis.
  • the fitting size may refer to the size of the phantom on the target axis determined based on the fitted three-dimensional image or three-dimensional model. For more details about determining the fitting size, please refer to step 404 in FIG. 4 and related descriptions.
  • the calibration module 330 can be used to correct the gradient sensitivity of the MRI device based on the fitted size and the actual size.
  • Gradient sensitivity can characterize the scale relationship between the object to be scanned and the MR image of the object to be scanned. For more information about calibrating the gradient sensitivity, please refer to step 406 in FIG. 4 and related descriptions.
  • Each module in the above-mentioned gradient sensitivity correction system can be fully or partially realized by software, hardware and a combination thereof.
  • the above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, and can also be stored in the memory of the computer device in the form of software, so that the processor can invoke and execute the corresponding operations of the above-mentioned modules.
  • the above description of the gradient sensitivity correction system and its modules is only for convenience of description, and does not limit this description to the scope of the illustrated embodiments. It can be understood that for those skilled in the art, after understanding the principle of the system, it is possible to combine various modules arbitrarily, or form a subsystem to connect with other modules without departing from this principle.
  • the obtaining module 310, the determining module 320 and the correcting module 330 disclosed in FIG. 3 may be different modules in one system, or one module may realize the functions of the above two modules.
  • each module in the gradient sensitivity calibration system may share one storage module, or each module may have its own storage module. Such deformations are within the protection scope of this specification.
  • FIG. 4 is a flowchart of an exemplary gradient sensitivity correction process 400 according to some embodiments of the present specification.
  • process 400 may be performed by MRI system 100 .
  • the process 400 may be stored in a storage device (eg, the storage device 150 ) in the form of an instruction set (eg, an application program).
  • processing device 140 eg, one or more modules shown in FIG. 3 ) may execute a set of instructions and instruct one or more components of MRI system 100 to perform process 400 accordingly.
  • the gradient magnetic field may be a magnetic field with a spatially varying strength generated by the gradient coils of the magnetic resonance scanner.
  • Gradient magnetic fields including gradient magnetic fields Gx, Gy, and Gz
  • Gx, Gy, and Gz can be superimposed on and distort the main magnetic field generated by the main magnet, so that the magnetic orientation of the protons of the object to be scanned can change according to their positions within the gradient magnetic field, Spatial information is thereby encoded into magnetic resonance (MR) signals (eg echo signals) generated by the region of the object to be scanned.
  • MR magnetic resonance
  • the gradient sensitivity may represent the scale relationship between the object to be scanned and the image (for example, MR image) acquired after MR scanning the object to be scanned.
  • the scale of the object to be scanned on the MR image can be adjusted by adjusting the gradient sensitivity. If the gradient sensitivity is inaccurate, the size of the object to be scanned on the MR image is inconsistent with the actual size of the object to be scanned, thereby affecting the accuracy of the MRI system. In order to ensure that the size of the object in the acquired MR image is consistent with the actual size of the object, it is necessary to correct the gradient sensitivity of the MRI equipment.
  • the size of the object in the MR image refers to the size of the object in the actual physical space determined based on the image. For example, the size of the object in the actual physical space may be determined based on the pixel size of the part representing the object in the image and the correspondence between the image and the actual physical space.
  • a spherical phantom is mostly used, and the gradient sensitivity of the MRI equipment is corrected by using the consistency of the dimensions of the coronal (Cor), sagittal (Sag), and transverse (Tra) planes at the center of the spherical phantom.
  • Cor coronal
  • Sag sagittal
  • Tra transverse
  • the phantom setup there is a very high precision requirement for the phantom setup, that is, the center of the phantom needs to coincide with the center of the MRI system as much as possible. Once the setup of the phantom does not meet the accuracy requirements, it will lead to inaccurate calibration of the gradient sensitivity.
  • the scanning chamber has a relatively small inner diameter and a long length, and a retractable cantilever bed fixed outside the scanning chamber is generally used to send the object to be scanned to into the center of the magnet imaging area of the scan chamber.
  • the cantilever end of the cantilever MRI system is drooping, which makes it difficult to determine the center position of the phantom. Therefore, it takes a lot of time and effort to position the phantom accurately by using the traditional gradient sensitivity correction method, which reduces the efficiency of the MRI system and user experience. Accordingly, there is a need to provide efficient systems and methods for gradient sensitivity correction.
  • gradient sensitivity can be corrected by performing the following operations of process 400 .
  • the processing device 140 may acquire a three-dimensional image of the phantom.
  • Three-dimensional images can be acquired using MRI equipment.
  • the phantom may have known actual dimensions on the target axis.
  • Phantoms A phantom that can be used to test an MRI system.
  • phantoms can be used to monitor the image performance of an MRI system.
  • tests performed on an MRI system may include gradient sensitivity, spatial uniformity, scan slice thickness/slice spacing, collimation system verification, spatial resolution, geometric distortion rate (spatial linearity), signal-to-noise ratio ( SNR), low contrast sensitivity (low contrast resolution), T1 and T2 relaxation time values and other measurement content.
  • the phantom may be composed of any material capable of generating magnetic resonance signals under a magnetic field.
  • the phantom can be made of a single material.
  • the phantom can be made from a variety of materials.
  • the phantom may include a glass enclosure and a liquid (eg, water, saline solution).
  • the phantom may have a fixed shape.
  • phantoms can have regular shapes (eg, spheres, cylinders, cuboids, cubes, etc.) and irregular shapes. Therefore, the processing device 140 can obtain the actual size of the phantom on the target axis based on the shape of the phantom.
  • the target axis may include taking the center position (for example, the isocenter) of the magnet imaging area of the MRI system (for example, the MRI scanner 110) as the origin, and taking three orthogonal axes in space as the three-axis directions respectively.
  • the target axes may include the X-axis, Y-axis, and Z-axis of the coordinate system shown in FIG. 1 .
  • the phantom may be a spherical phantom. Since the distance from the center of the spherical model to every point on the spherical surface is equal to the radius of the sphere, the processing device 140 can determine the actual size of the spherical phantom on the target axis based on the radius of the spherical phantom. Moreover, the spherical phantom can be placed anywhere in the magnet imaging area, and it is not necessary to place the center of the spherical phantom at the center of the magnet imaging area.
  • the phantom When the phantom is a non-spherical phantom (for example, a cylindrical phantom, a rectangular phantom, a cube phantom, etc.), the phantom can be positioned first, and then the actual size of the phantom on the target axis can be determined. As an example only, as shown in FIG.
  • the phantom is a cylindrical phantom, and the center point of the cylindrical phantom and the center position (i.e., point O) of the magnet imaging region of the MRI system (for example, MRI scanner 110) can be made ) coincide, so that the vertical direction of the cylindrical phantom is parallel to the Z-axis of the MRI system, and the horizontal section of the cylindrical phantom is parallel to the XZ plane of the MRI system, thereby completing the positioning of the cylindrical phantom.
  • the processing device 140 can determine the actual dimensions of the cylindrical phantom on the target axis.
  • the processing device 140 may determine the diameter of the bottom surface of the cylindrical phantom as the actual size of the cylindrical phantom on the X-axis and the Z-axis, and determine the height of the cylindrical phantom as the dimension of the cylindrical phantom in Y Actual size on axis.
  • the placement of the non-spherical phantom can be determined by the judgment of the user (eg, doctor, technician, etc.).
  • the processing device 140 can pre-set markers on the scanning bed, and the markers can be used to determine whether the positioning of the phantom is accurate. For example, the processing device 140 may determine whether the position of the phantom is accurate according to the positional relationship (for example, parallel, coincident) between the phantom and the marker.
  • the three-dimensional image of the phantom can be used to represent the three-dimensional information of the phantom (for example, three-dimensional structural features).
  • a three-dimensional image may refer to a magnetic resonance image acquired with an MRI device (eg, MRI scanner 110).
  • the processing device 140 may acquire MRI data of the phantom through an MRI device, and reconstruct a three-dimensional MR image according to the MRI data.
  • the processing device 140 may reconstruct a two-dimensional MR image from the MRI data.
  • the processing device 140 may further perform three-dimensional reconstruction on the two-dimensional MR image, so as to obtain a three-dimensional image of the phantom.
  • a spherical phantom may be scanned using a multi-slice scanning protocol to obtain a three-dimensional image of the spherical phantom.
  • the multi-slice scanning protocol can enable the MRI equipment to scan the spherical phantom in multiple layers, and obtain three-dimensional images of the spherical phantom from multiple levels, ensuring the accuracy of the obtained three-dimensional image of the spherical phantom.
  • the three-dimensional image of the spherical phantom in this embodiment is a reconstructed image, and the three-dimensional information of the spherical phantom is represented in the image.
  • the phantom can be scanned using a pulse sequence that is insensitive to the uniformity of the magnetic field (for example, conventional spin echo sequence, fast spin echo sequence, etc.), thereby reducing the influence of magnetic field inhomogeneity on MR imaging .
  • a pulse sequence that is insensitive to the uniformity of the magnetic field (for example, conventional spin echo sequence, fast spin echo sequence, etc.), thereby reducing the influence of magnetic field inhomogeneity on MR imaging .
  • the processing device 140 may acquire the three-dimensional image of the phantom directly from the MRI device (eg, the MRI scanner 110). Alternatively, processing device 140 may acquire the three-dimensional image of the phantom from a storage device (eg, storage device 150 ) that stores three-dimensional images of the phantom.
  • a storage device eg, storage device 150
  • the specific time and steps for obtaining the three-dimensional image of the phantom are not limited, as long as the three-dimensional image of the phantom can be obtained by performing magnetic resonance imaging on the phantom.
  • the processing device 140 may perform preprocessing operations (eg, resizing, image resampling, image normalization, etc.) after acquiring the three-dimensional image of the phantom.
  • the processing device 140 may further perform other steps in the process 400 on the preprocessed three-dimensional image.
  • the execution process of the process 400 is described below by taking the original three-dimensional image as an example.
  • the processing device 140 may perform fitting on the three-dimensional image, and determine the fitting size of the phantom on the target axis.
  • the fitting size may refer to the size of the phantom on the target axis determined based on the fitted three-dimensional image or three-dimensional model.
  • the processing device 140 may use a preset fitting algorithm to fit the three-dimensional image of the phantom to obtain a fitted three-dimensional image or model. For example, the processing device 140 may reconstruct the phantom based on the three-dimensional image. Further, the processing device 140 may determine the fitting size of the phantom on the target axis based on the fitted three-dimensional image or model. It can be understood that the coordinates of each point in the coordinate system established with the central position of the magnet imaging area as the origin and the three orthogonal axes as the directions of the three axes can be obtained. That is, the processing device 140 may determine the fitting size of the phantom on the target axis based on the fitting image.
  • the processing device 140 can use a preset fitting algorithm to fit the three-dimensional image of the spherical phantom (for example, ellipsoid fitting), that is, the three-dimensional image fitting based on the spherical phantom
  • a preset fitting algorithm to fit the three-dimensional image of the spherical phantom (for example, ellipsoid fitting), that is, the three-dimensional image fitting based on the spherical phantom
  • a sphere eg, an ellipsoid or a standard sphere
  • the processing device 140 can obtain the fitting size of the longest axis of the ellipsoid and the fitting size of the shortest axis of the ellipsoid based on the coordinates of each point in the coordinate system. dimension, and the fitted dimension of an axis perpendicular to both the longest and shortest axes. For another example, if a standard sphere is fitted based on the three-dimensional image of the spherical phantom, the processing device 140 may obtain the fitting size of the target axis of the standard sphere through the coordinates of each point in the coordinate system.
  • the processing device 140 may determine at least one central section based on the three-dimensional image.
  • the central section may refer to a section passing through the center of the phantom in the three-dimensional image, for example, a first section parallel to the XY plane and passing through the center of the phantom, a second section parallel to the XZ plane passing through the center of the phantom, and a YZ plane A third section parallel to and passing through the center of the phantom. Further, the processing device 140 may determine the fitting size of the phantom on the target axis based on at least one central section.
  • the processing device 140 can obtain the fitting dimensions of the phantom on the X-axis and the Y-axis; based on the second section, the processing device 140 can obtain the fitting dimensions of the phantom on the X-axis and the Z-axis; Based on the third section, the processing device 140 can obtain the fitting dimensions of the phantom on the Y-axis and the Z-axis. In some embodiments, the processing device 140 may assign a weight to each fitting size, and determine the fitting size of the phantom on the target axis in a weighted manner.
  • the processing device 140 may assign weights to the fitting size of the phantom on the Y-axis determined based on the first cross-section and the fitting size of the phantom on the Y-axis determined based on the third cross-section (for example, weight 1 and weight 2 ), and determine the fitting size of the phantom on Y by weighting.
  • weight 1 and weight 2 may be the same or different.
  • the processing device 140 may correct the gradient sensitivity of the MRI device based on the fitted size and the actual size.
  • Gradient sensitivity can characterize the scale relationship between the object to be scanned and the MR image of the object to be scanned.
  • Gradient sensitivity may be accurate when the size of the object (eg, phantom) in the acquired magnetic resonance image remains consistent with the actual size of the object.
  • the gradient sensitivity may be inaccurate when the size of the object in the acquired magnetic resonance image does not correspond to the actual size of the object.
  • gradient sensitivity is inaccurate when a spherical phantom appears as an ellipsoid in the acquired MRI image, or when the fitted size of the phantom at the target axis does not match the actual size of the phantom at the target axis.
  • the processing device 140 can obtain the similarity between the fitted size and the actual size, and based on the similarity, correct the gradient sensitivity of the MRI device.
  • the similarity may refer to the closeness of the numerical values of the fitting size and the actual size. For example, if the similarity value between the fitted size and the actual size is large (for example, the fitted size of the phantom on each target axis has a large similarity value to the actual size of the object on the corresponding axis), then the fitted size Similar to the actual size, the processing device 140 may finely adjust the gradient sensitivity of the MRI device or keep the current gradient sensitivity of the MRI device unchanged.
  • the processing device 140 can greatly adjust the gradient sensitivity of the MRI device until the fitted size is close to the actual size. It can be understood that, ideally, the fitted size of the phantom on the target axis is the actual size of the target axis of the phantom. That is, ideally, the fitted size is equal to the actual size.
  • processing device 140 may determine the difference between the fitted size and the actual size. The processing device 140 may determine whether the difference satisfies a preset condition. If the difference does not satisfy the preset condition, the processing device 140 may correct the gradient sensitivity of the MRI device. If the difference satisfies a preset condition, the processing device 140 may not correct the gradient sensitivity of the MRI device. That is, magnetic resonance imaging of a subject can be performed without correcting the gradient sensitivity of the MRI apparatus. For more information on calibrating the gradient sensitivity, please refer to FIG. 5 and its related description.
  • processing device 140 may verify the corrected gradient sensitivity. For example, the processing device 140 may determine the verification fitting size of the phantom on the target axis based on the three-dimensional verification image of the phantom acquired by the MRI device with the corrected gradient sensitivity, and based on the verification difference between the verification fitting size and the actual size , to verify the corrected gradient sensitivity. More information on verifying gradient sensitivity can be found in Figure 6 and its related description.
  • the gradient sensitivity of the MRI equipment can be corrected based on the fitting size and the actual size, thereby improving the accuracy of gradient sensitivity correction.
  • the fitting size of the spherical phantom on the target axis can be determined based on the three-dimensional image of the spherical phantom obtained by acquiring the three-dimensional image of the spherical phantom. Due to the physical properties of the sphere, the spherical phantom can be placed anywhere in the magnet imaging area of the MRI system, that is, the center of the spherical phantom does not need to coincide with the center of the magnet imaging area.
  • the gradient sensitivity calibration method provided by some embodiments of this specification can be used in any MRI system, especially MRI with a small scanning cavity and difficult positioning of the phantom. system (eg, cantilever MRI system, animal MRI system, infant MRI system, etc.).
  • process 400 may be accomplished with one or more additional operations not described and/or omitting one or more operations discussed above.
  • the processing device 140 may store the corrected gradient sensitivity in a storage device (for example, the storage device 150 ) for use in subsequent MRI scans.
  • FIG. 5 is a flowchart of an exemplary process 500 for calibrating gradient sensitivity according to some embodiments of the present specification.
  • process 500 may be performed by MRI system 100 .
  • the process 500 may be stored in a storage device (eg, the storage device 150 ) in the form of an instruction set (eg, an application program).
  • processing device 140 eg, one or more modules shown in FIG. 3
  • operation 406 in FIG. 4 may be implemented by executing process 500 .
  • the processing device 140 may determine a difference between the fitted size and the actual size.
  • the difference may represent a difference between the fitted size and the actual size.
  • the processing device 140 may determine the difference between the fitted size and the actual size based on the difference between the fitted size and the actual size. For example, the processing device 140 may respectively determine the first difference between the fitted size of the phantom on the X axis and the actual size of the phantom on the X axis, the fitted size of the phantom on the Y axis and the first difference between the phantom's actual size on the Y axis. and/or the third difference between the fitted size of the phantom on the Z axis and the actual size of the phantom on the Z axis. The processing device 140 may further determine the difference between the fitted size and the actual size based on the first difference, the second difference and the third difference.
  • the difference sum of the first difference, the second difference and the third difference may be used as the difference between the fitted size and the actual size.
  • the larger the difference sum the greater the difference between the fitted size and the actual size; the smaller the difference sum, the smaller the difference between the fitted size and the actual size.
  • the processing device 140 may determine the difference between the fitted size and the actual size based on the ratio of the fitted size to the actual size. For example, the processing device 140 may respectively determine a first ratio of the fitted size of the phantom on the X axis to the actual size of the phantom on the X axis, the fitted size of the phantom on the Y axis and the first ratio of the phantom's actual size on the Y axis. The second ratio of the actual size of the phantom and/or the third ratio of the fitted size of the phantom on the Z axis to the actual size of the phantom on the Z axis.
  • the processing device 140 may further determine the difference between the fitted size and the actual size based on the first ratio, the second ratio, and the third ratio. For example, the average of the first ratio, the second ratio, and the third ratio can be used as the difference between the fitted size and the actual size. The closer the average value is to 1, the smaller the difference between the fitted size and the actual size; the farther the average value is from 1, the larger the difference between the fitted size and the actual size.
  • the processing device 140 may determine whether the difference satisfies a preset condition.
  • the difference if the difference satisfies the preset condition, it may indicate that the gradient sensitivity of the MRI equipment has been adjusted to an acceptable range. That is to say, if the difference satisfies the preset condition, it may indicate that there is no need to adjust the gradient sensitivity of the MRI equipment.
  • the preset condition may include a threshold corresponding to the difference. For example, if the difference is the difference between the fitting size and the actual size (for example, the difference sum of the first difference, the second difference and the third difference mentioned above), the preset condition can be that the difference is less than The preset difference threshold or within the preset difference range, for example, 0.1 mm, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 5 mm and so on.
  • the preset condition can be that the ratio is less than the preset ratio threshold or Within the preset ratio range, for example, 0.95 to 1.05, 0.9 to 1.1, 0.85 to 1.15, 0.8 to 1.2, etc.
  • step 506 When the difference does not satisfy the preset condition, the processing device 140 may execute step 506 .
  • step 504 may be omitted, and the processing device 140 may directly execute step 506 .
  • the processing device 140 may correct the gradient sensitivity of the MRI device.
  • the processing device 140 may correct the gradient sensitivity of the MRI device based on the difference. For example, the processing device 140 may determine the correction value for the gradient sensitivity based on the difference, according to the physical principles of magnetic resonance (eg, the characteristics of the gradient magnetic field of the MRI system). As an example only, the processing device 140 may pre-acquire a relationship (for example, a linear relationship) between the gradient sensitivity and the difference, and then determine the correction value of the gradient sensitivity based on the difference. Further, the processing device 140 may correct the gradient sensitivity of the MRI device based on the correction value.
  • the processing device 140 may correct the gradient sensitivity of the MRI device based on the correction value.
  • the processing device 140 may determine a correction value of the gradient sensitivity based on the difference, and use the sum of the correction value and the gradient sensitivity as the corrected gradient sensitivity. If the difference is the ratio of the fitted size to the actual size, the processing device 140 may determine a correction value of the gradient sensitivity based on the ratio, and use the product of the correction value and the gradient sensitivity as the corrected gradient sensitivity.
  • the processing device 140 may adjust the gradient sensitivity factor of the MRI device according to the difference between the fitted size and the actual size, so that the difference meets a preset condition. For example, if the difference between the fitted size and the actual size decreases after the gradient sensitivity factor of the MRI device is adjusted, the gradient sensitivity factor of the MRI device may be adjusted continuously according to the current adjustment direction. For another example, if the difference between the fitted size and the actual size increases after the gradient sensitivity factor of the MRI equipment is adjusted, the current adjustment direction can be adjusted, and the gradient sensitivity factor of the MRI equipment can be adjusted in the direction opposite to the previous adjustment direction. Make adjustments.
  • the difference between the fitted size and the actual size eg, the sum of the differences described above
  • the difference between the fitted size and the actual size is 0.5
  • the gradient sensitivity factor of the MRI equipment can be continuously adjusted in the current adjustment direction, so as to correct the gradient sensitivity of the MRI equipment until the difference satisfies the preset condition.
  • the current adjustment direction can be adjusted to match the previous
  • the adjustment direction opposite to the adjustment direction adjusts the gradient sensitivity factor of the MRI equipment, so as to correct the gradient sensitivity of the MRI equipment until the difference satisfies the preset condition.
  • the gradient sensitivity of the MRI device may be corrected.
  • the gradient sensitivity factor of the MRI equipment can be accurately adjusted according to the difference, thereby improving the accuracy and efficiency of the gradient sensitivity correction of the MRI equipment.
  • process 500 may be accomplished with one or more additional operations not described and/or omitting one or more operations discussed above.
  • FIG. 6 is a flowchart of an exemplary process 600 for verifying gradient sensitivity according to some embodiments of the present specification.
  • process 600 may be performed by MRI system 100 .
  • the process 600 may be stored in a storage device (eg, the storage device 150 ) in the form of an instruction set (eg, an application program).
  • processing device 140 eg, one or more modules shown in FIG. 3
  • operation 406 in FIG. 4 may be implemented by executing process 600 .
  • the processing device 140 may acquire a three-dimensional verification image of the phantom.
  • Three-dimensional verification images can be acquired using an MRI device with corrected gradient sensitivity.
  • the processing device 140 can correct the gradient sensitivity of the MRI device through the process 400 or the process 500, and use the MRI device with the corrected gradient sensitivity to acquire a three-dimensional verification image of the phantom.
  • the manner of acquiring the 3D verification image may be similar to the manner of acquiring the 3D image described in step 402 .
  • the processing device 140 may perform fitting based on the three-dimensional verification image, and determine the verification fitting size of the phantom on the target axis.
  • the verification fitting size may refer to the size of the phantom on the target axis determined based on the fitted 3D verification image or 3D model.
  • the method of determining the fitting size for verification may be similar to the method of determining the fitting size described in step 404 .
  • the processing device 140 may determine a verified difference between the verified fitted size and the actual size.
  • the processing device 140 may obtain the actual size of the phantom on the target axis based on the shape of the phantom. Alternatively, the processing device 140 may obtain the actual size of the phantom on the target axis based on a gradient sensitivity calibration procedure (eg, procedure 400 ).
  • the verification difference may characterize the difference between the verification fitted dimensions and the actual dimensions.
  • the manner of determining the verification difference may be similar to the manner of determining the difference described in step 502.
  • the processing device 140 may verify the corrected gradient sensitivity based on the verification difference.
  • the manner of determining whether the verification difference satisfies the preset condition may be similar to the manner of determining whether the difference satisfies the preset condition described in step 504 .
  • the processing device 140 may determine that the gradient sensitivity correction is completed. That is, magnetic resonance imaging of the subject can be performed using the MRI apparatus with the corrected gradient sensitivity.
  • the processing device 140 may determine that the gradient sensitivity of the MRI device needs to be continuously corrected until the corrected gradient sensitivity is verified, that is, the corrected gradient sensitivity passes through the process 600 .
  • the corrected gradient sensitivity of the MRI device can be verified based on the three-dimensional verification image acquired by the MRI device with the corrected gradient sensitivity, so as to ensure the accuracy of gradient sensitivity correction.
  • process 600 may be accomplished with one or more additional operations not described and/or omitting one or more operations discussed above.
  • FIG. 7 is a schematic diagram of an exemplary process 700 for calibrating gradient sensitivity according to some embodiments of the present specification.
  • a three-dimensional image 704 of a spherical phantom 702 may be acquired using an MRI device 703 . Fitting the three-dimensional image 704 can determine the fitting size 706 of the spherical phantom 702 on the target axis. Further, the actual size 708 of the spherical phantom 702 on the target axis may be obtained. Based on the fitted size 706 and the actual size 708 , a difference 710 between the fitted size 706 and the actual size 708 may be determined. Further, the process 700 may execute step 712 to determine whether the difference 710 satisfies a preset condition.
  • the process 700 may execute step 716 to end the process 700 . If the difference 710 does not satisfy the preset condition, the process 700 may execute step 714 to correct the gradient sensitivity of the MRI device 703 .
  • the MRI apparatus with corrected gradient sensitivity 703 may perform the process 700 again, thereby verifying the corrected gradient sensitivity.
  • the MRI device 703 with the corrected gradient sensitivity can acquire a three-dimensional image 704 (referred to as a three-dimensional verification image) of the spherical phantom 702 again. Fitting the three-dimensional verification image again can determine the fitting size 706 of the spherical phantom 702 on the target axis (referred to as the verification fitting size).
  • a difference 710 (referred to as a verified difference) of the verified fitted and actual sizes 708 may be determined.
  • the process 700 may execute step 712 to determine whether the verification difference satisfies a preset condition.
  • the process 700 may execute step 716 to end the process 700 . That is, it can be understood that the verification of the corrected gradient sensitivity is completed. If the verification difference does not meet the preset condition, the process 700 may execute step 714 to continue to correct the gradient sensitivity of the MRI device 703 until the corrected gradient sensitivity is verified.
  • the gradient sensitivity of the MRI equipment can be corrected, thereby improving the accuracy of gradient sensitivity correction;
  • the gradient sensitivity can be corrected through a spherical phantom, because the spherical
  • the spherical phantom can be placed anywhere in the magnet imaging area of the MRI system, that is, the center of the spherical phantom does not need to coincide with the center of the magnet imaging area, which can reduce the impact on the phantom placement during gradient sensitivity correction.
  • the gradient sensitivity correction method provided by some embodiments of this specification can be used in any MRI system, Especially for MRI systems with small scanning chambers and difficult positioning of phantoms (for example, cantilever MRI systems, animal MRI systems, infant MRI systems, etc.); Verifying the image can verify the gradient sensitivity of the corrected MRI equipment, thereby ensuring the accuracy of gradient sensitivity correction.
  • Some embodiments of the present description also provide an MRI device, the MRI device includes: at least one storage medium storing computer instructions; at least one processor executing the computer instructions to implement the gradient sensitivity correction method described in this specification.
  • the MRI device includes: at least one storage medium storing computer instructions; at least one processor executing the computer instructions to implement the gradient sensitivity correction method described in this specification.
  • Some embodiments of the present description also provide a computer-readable storage medium, the storage medium stores computer instructions, and when the computer reads the computer instructions, the computer executes the gradient sensitivity correction method described in the present specification.
  • the storage medium stores computer instructions, and when the computer reads the computer instructions, the computer executes the gradient sensitivity correction method described in the present specification.
  • user information including but not limited to user equipment information, user personal information, etc.
  • data including but not limited to data used for analysis, stored data, displayed data, etc.
  • numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of the embodiments use the modifiers "about”, “approximately” or “substantially” in some examples. grooming. Unless otherwise stated, “about”, “approximately” or “substantially” indicates that the stated figure allows for a variation of ⁇ 20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximations that can vary depending upon the desired characteristics of individual embodiments. In some embodiments, numerical parameters should take into account the specified significant digits and adopt the general digit reservation method. Although the numerical ranges and parameters used in some embodiments of this specification to confirm the breadth of the range are approximations, in specific embodiments, such numerical values are set as precisely as practicable.

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Abstract

一种梯度灵敏度校正方法和系统。方法包括获取模体的三维图像，三维图像利用MRI设备采集，模体在目标轴上具有已知的实际尺寸(402)；对三维图像进行拟合，确定模体在目标轴上的拟合尺寸(404)；以及基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度(406)。

Description

梯度灵敏度校正方法和系统
交叉引用
本申请要求2021年12月14日提交的名称为“梯度灵敏度校准方法、装置及磁共振设备”的中国专利申请202111525705.1的优先权，上述申请的全部内容以引用方式并入本文。
技术领域
本说明书涉及磁共振成像(magnetic resonance imaging，MRI)领域，尤其涉及一种梯度灵敏度校正方法和系统。
背景技术
在磁共振系统中，为了确保采集的磁共振图像的尺寸与实物尺寸保持一致，需要对MRI设备的梯度灵敏度进行校正。
传统技术中，大多使用球形模体，利用球形模体中心点上冠状面、矢状面、横断面三个层面尺寸的一致性对MRI设备的梯度灵敏度进行校正。但是，实际操作过程中对模体的摆位有非常高的精度要求，需要尽可能将模体的中心与MRI设备的中心重合。
因此，传统的MRI设备的梯度灵敏度的校正方法，存在校正准确度较低、操作复杂的问题。
发明内容
本说明书实施例之一提供一种梯度灵敏度校正方法。所述方法可以由至少一个处理器执行。所述方法可以包括获取模体的三维图像，三维图像利用MRI设备采集，模体在目标轴上具有已知的实际尺寸；对三维图像进行拟合，确定模体在目标轴上的拟合尺寸；以及基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度。
在一些实施例中，模体可以是球形模体。
在一些实施例中，模体可以是非球形模体，非球形模体可以基于目标轴进行摆位。
在一些实施例中，基于三维图像进行拟合，确定模体在目标轴上的拟合尺寸可以包括基于三维图像，确定至少一个中心截面；以及基于至少一个中心截面，确定模体在目标轴上的拟合尺寸。
在一些实施例中，基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度可以包括确定拟合尺寸与实际尺寸之间的差别；确定差别是否满足预设条件；以及响应于差别不满足预设条件，校正MRI设备的梯度灵敏度。
在一些实施例中，所述方法可以进一步包括验证校正后的梯度灵敏度。
在一些实施例中，验证校正后的梯度灵敏度可以包括获取模体的三维验证图像，三维 验证图像利用具有校正后的梯度灵敏度的MRI设备采集；基于三维验证图像进行拟合，确定模体在目标轴上的验证拟合尺寸；确定验证拟合尺寸与实际尺寸的验证差别；以及基于验证差别，验证校正后的梯度灵敏度。
在一些实施例中，MRI设备可以包括悬臂床，模体可以被放置于悬臂床上。
在一些实施例中，目标轴可以包括以MRI设备的磁体成像区域的中心位置为原点、以空间正交的三轴分别作为三轴方向建立的坐标系所对应的三个坐标轴。
本说明书实施例之一提供一种梯度灵敏度校正系统。所述系统可以包括存储设备，存储计算机指令；处理器，与存储设备相连接。当执行计算机指令时，处理器使所述系统执行下述操作。所述操作可以包括获取模体的三维图像，三维图像利用MRI设备采集，模体在目标轴上具有已知的实际尺寸；对三维图像进行拟合，确定模体在目标轴上的拟合尺寸；以及基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度。
本说明书实施例之一提供一种计算机可读存储介质，所述存储介质存储计算机指令，当计算机读取所述计算机指令，所述计算机执行一种梯度灵敏度校正方法。所述方法可以包括获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸；对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸；以及基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
本说明书实施例之一提供一种梯度灵敏度校正系统。所述系统可以包括获取模块、确定模块和校正模块。获取模块可以用于获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸。确定模块可以用于对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸。校正模块可以用于基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
附图说明
本说明书将以示例性实施例的方式进一步说明，这些示例性实施例将通过附图进行详细描述。这些实施例并非限制性的，在这些实施例中，相同的编号表示相同的结构，其中：
图1是根据本说明书一些实施例所示的示例性MRI系统的应用场景示意图；
图2是根据本申请的一些实施例所示的示例性计算设备的示意图；
图3是根据本说明书的一些实施例所示的示例性处理设备的模块图；
图4是根据本说明书的一些实施例所示的示例性梯度灵敏度校正流程的流程图；
图5是根据本说明书的一些实施例所示的示例性校正梯度灵敏度的流程的流程图；
图6是根据本说明书的一些实施例所示的示例性的验证梯度灵敏度的流程的流程图；
图7是根据本说明书的一些实施例所示的示例性校正梯度灵敏度的流程的示意图；
图8是根据本说明书的一些实施例所示的示例性圆柱形模体的示意图。
具体实施方式
为了更清楚地说明本说明书实施例的技术方案，下面将对实施例描述中所需要使用的附图作简单的介绍。显而易见地，下面描述中的附图仅仅是本说明书的一些示例或实施例，对于本领域的普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图将本说明书应用于其它类似情景。除非从语言环境中显而易见或另做说明，图中相同标号代表相同结构或操作。
应当理解，本文使用的“系统”、“装置”、“单元”和/或“模块”是用于区分不同级别的不同组件、元件、部件、部分或装配的一种方法。然而，如果其他词语可实现相同的目的，则可通过其他表达来替换所述词语。
如本说明书和权利要求书中所示，除非上下文明确提示例外情形，“一”、“一个”、“一种”和/或“该”等词并非特指单数，也可包括复数。一般说来，术语“包括”与“包含”仅提示包括已明确标识的步骤和元素，而这些步骤和元素不构成一个排它性的罗列，方法或者设备也可能包含其它的步骤或元素。
本说明书中使用了流程图用来说明根据本说明书的实施例的系统所执行的操作。应当理解的是，前面或后面操作不一定按照顺序来精确地执行。相反，可以按照倒序或同时处理各个步骤。同时，也可以将其他操作添加到这些过程中，或从这些过程移除某一步或数步操作。
本文提供了用于磁共振影像的系统和组件。在一些实施例中，磁共振影像系统可以包括单模态影像系统和/或多模态影像系统。单模态影像系统可包括例如MRI系统。示例性MRI系统可包括超导磁共振成像系统、非超导磁共振成像系统等。多模态影像系统可包括，例如，计算机断层扫描-磁共振成像(MRI-CT)系统、正电子发射断层扫描-磁共振成像(PET-MRI)系统、单光子发射计算机断层扫描-磁共振成像(SPECT-MRI)系统、数字减影血管造影-磁共振成像(DSA-MRI)系统等。
图1是根据本说明书一些实施例所示的示例性MRI系统100的应用场景示意图。
如图1所示，MRI系统100可以包括MRI扫描仪110、网络120、一个或以上终端130、处理设备140和存储设备150。MRI系统100中的组件可以以各种方式中的一种或多种连接。仅作为示例，MRI扫描仪110可以通过网络120连接到处理设备140。又例如，MRI扫描仪110可以直接连接到处理设备140，如由虚线的双向箭头所指示的，所述虚线的双向箭头连接MRI扫描仪110和处理设备140。又例如，存储设备150可以直接或通过网络120连接到处理设备140。再例如，终端130可以直接(如连接终端130和处理设备140的虚线的双向箭 头所示)或通过网络120连接到处理设备140。
在一些实施例中，MRI扫描仪110可以扫描位于其检测区域内的对象，并生成与对象有关的数据(例如，与对象相关联的回波信号或MR信号)。例如，MRI扫描仪110可以通过执行一个或多个协议来扫描对象。在本申请中，“对象”和“物体”可互换使用。仅作为示例，对象可以包括人体、动物、人造对象(例如，模体)等。又例如，对象可以包括人体、动物或者模体的特定部分，器官和/或组织。例如，对象可以包括头部、脑部、颈部、身体、肩部、手臂、胸部、心脏、胃、血管、软组织、膝盖、脚等，或其任何组合。
在一些实施例中，MRI扫描仪110可以包括闭孔MRI扫描仪或开孔MRI扫描仪。在一些实施例中，根据主磁体的类型，MRI扫描仪110可以包括永磁体磁共振扫描仪、超导电磁体磁共振扫描仪、电阻式电磁体磁共振扫描仪等。在一些实施例中，根据磁场的强度，MRI扫描仪110可以包括高场MRI扫描仪、中场MRI扫描仪、低场MRI扫描仪等。在一些实施例中，根据床的运动方式，MRI扫描仪110可以包括滑轨床MRI扫描仪、悬臂式MRI扫描仪等。例如，悬臂式MRI扫描仪可以包括动物MRI扫描仪、婴儿MRI扫描仪等。
在本申请中，图1中所示的X轴、Y轴和Z轴可以形成正交坐标系。图1中所示的X轴和Z轴可以是水平的，Y轴可以是垂直的。图1所示的沿着X轴的正X方向可以是从面向MRI扫描仪110的前方的方向看到的MRI扫描仪110的右侧到左侧，图1中所示的沿Y轴的正Y方向可以是MRI扫描仪110的下部到上部，图1中所示的沿Z轴的正Z方向可以指对象移出MRI扫描仪110的扫描通道(也称为孔)的方向。在一些实施例中，MRI扫描仪110可以包括例如主磁体、梯度线圈(也称为空间编码线圈)、射频(RF)线圈等。
主磁体可以产生第一磁场(也称为主磁场)，其可以作用于暴露在主磁场内的对象(也称为物体)。主磁体可以包括用于放置对象的孔径。主磁体还可以控制所产生的主磁场的均匀性。例如，一些匀场线圈可以在主磁体中。放置在主磁体的间隙中的匀场线圈可以补偿主磁体的磁场的不均匀性。
梯度线圈可以位于主磁体内。梯度线圈可以产生第二磁场(或被称为梯度磁场，包括梯度磁场Gx、Gy和Gz)。第二磁场可以叠加在由主磁体产生的主磁场上并使主磁场扭曲，使得对象的质子的磁取向可以根据它们在梯度磁场内的位置而变化，从而将空间信息编码成由成像的对象的区域产生的磁共振(MR)信号(例如，回波信号)。梯度线圈可以包括X线圈(例如，用于生成对应于X方向的梯度磁场Gx)、Y线圈(例如，用于生成对应于Y方向的梯度磁场Gy)和/或Z线圈(例如，用于生成对应于Z方向的梯度磁场Gz)(图1中未示出)。在一些实施例中，Z线圈可以基于圆形(Maxwell)线圈设计，而X线圈和Y线圈可以基于鞍形(Golay)线圈配置来设计。三组线圈可以产生三个不同的磁场，用于位置编码。 梯度线圈可以允许用于图像构建的MR信号进行空间编码。在一些情况下，梯度线圈的三组线圈可以被激励并由此可以生成三个梯度磁场。
在一些实施例中，RF线圈可以位于主磁体内并且用作发射器、接收器或其两者。当用作发射器时，RF线圈可以产生RF信号。RF信号可以提供第三磁场，该第三磁场可以用于产生与成像的对像的区域相关的MR信号。第三磁场可以垂直于主磁场。当用作接收器时，RF线圈可以负责检测MR信号。在激励之后，对象产生的MR信号可以由RF线圈感测。
网络120可以包括可以促进MRI系统100的信息和/或数据交换的任何合适的网络。在一些实施例中，MRI系统100的一个或以上组件(例如，MRI扫描仪110、终端130、处理设备140或存储设备150)可以经由网络120与MRI系统100的一个或以上其他组件传送信息和/或数据。例如，处理设备140可以经由网络120从MRI扫描仪110获取对象有关的数据。在一些实施例中，网络120可以是有线网络或无线网络等或其任意组合。网络120可以是和/或包括公共网络(例如，因特网)、专用网络(例如，局部区域网络(LAN)、广域网(WAN)等)、有线网络(例如，以太网网络)、无线网络(例如，11网络、Wi-Fi网络等)、蜂窝网络(例如，长期演进(LTE)网络)、帧中继网络、虚拟专用网络(“VPN”)、卫星网络、电话网络、路由器、集线器、交换机、服务器计算机和/或其任何组合。仅作为示例，网络120可以包括电缆网络、有线网络、光纤网络、电信网络、内联网、无线局部区域网络(WLAN)、城域网(MAN)、公共电话交换网(PSTN)、蓝牙网络、ZigBee网络、近场通信(NFC)网络等，或其任何组合。在一些实施例中，网络120可以包括一个或以上网络接入点。例如，网络120可以包括有线和/或无线网络接入点，例如基站和/或互联网交换点，MRI系统100的一个或以上组件可以通过它们连接到网络120以交换数据和/或信息。
终端130包括移动设备131、平板电脑132、膝上型计算机133等，或其任何组合。在一些实施例中，移动设备131可以包括智能家居设备、可穿戴设备、智能移动设备、虚拟现实设备、增强现实设备等，或其任意组合。在一些实施例中，智能家居设备可以包括智能照明设备、智能电器控制设备、智能监控设备、智能电视、智能摄像机、对讲机等，或其任意组合。在一些实施例中，可穿戴设备可包括智能手环、智能鞋袜、一副智能眼镜、智能头盔、智能手表、智能服装、智能背包、智能配件等，或其任何组合。在一些实施例中，智能移动设备可以包括智能电话、个人数字助理(PDA)、游戏设备、导航设备、销售点(POS)等，或其任意组合。在一些实施例中，虚拟现实设备和/或增强型虚拟现实设备可以包括虚拟现实头盔、虚拟现实眼镜、虚拟现实眼罩、增强现实头盔、增强现实眼镜、增强现实眼罩等，或其任意组合。例如，虚拟现实设备和/或增强现实设备可以包括Google Glass TM、Oculus Rift TM、Hololens TM、Gear VR TM等。在一些实施例中，终端130可以远程操作MRI扫描仪110和/或 处理设备140。在一些实施例中，终端130可以通过无线连接操作MRI扫描仪110和/或处理设备140。在一些实施例中，终端130可以接收由用户输入的信息和/或指令，并且经由网络120将所接收的信息和/或指令发送到MRI扫描仪110或处理设备140。在一些实施例中，终端130可以从处理设备140接收数据和/或信息。在一些实施例中，终端130可以是处理设备140的一部分。在一些实施例中，可以省略终端130。
处理设备140可以处理从MRI扫描仪110、终端130和/或存储设备150获得的数据和/或信息。例如，处理设备140可以获取模体的实际尺寸和拟合尺寸，并且基于实际尺寸和拟合尺寸，校正MRI扫描仪110的梯度灵敏度。在一些实施例中，处理设备140可以是单个服务器或服务器组。服务器组可以是集中式的或分布式的。在一些实施例中，处理设备140可以是本地的或远程的。例如，处理设备140可以经由网络120访问存储在MRI扫描仪110、终端130和/或存储设备150中或由其获取的信息和/或数据。又例如，处理设备140可以直接连接到MRI扫描仪110(如图1中连接处理设备140和MRI扫描仪110的虚线中的双向箭头所示)、终端130(如图1中连接处理设备140和终端130的虚线中的双向箭头所示)和/或存储设备150，以访问存储的或获取的信息和/或数据。在一些实施例中，处理设备140可以在云平台上实现。仅作为示例，该云平台可以包括私有云、公共云、混合云、社区云、分布云、内部云、多层云等或其任意组合。在一些实施例中，处理设备140可以在计算设备200上实现，该计算设备200具有本申请中的图2中所示的一个或以上组件。在一些实施例中，处理设备140或处理设备140的一部分可以集成到MRI扫描仪110中。
存储设备150可以存储数据和/或指令。在一些实施例中，存储设备150可以存储从MRI扫描仪110、终端130和/或处理设备140获取的数据。例如，存储设备150可以存储模体的三维图像、实际尺寸、拟合尺寸等数据。在一些实施例中，存储设备150可以存储处理设备140可以执行或用于执行本申请中描述的示例性方法的数据和/或指令。例如，存储设备150可以存储处理设备140以执行校正梯度灵敏度的指令。一些实施例中，存储设备150包括大容量存储设备、可移动存储设备、易失性读写内存、只读内存(ROM)等，或其任意组合。示例性大容量存储器可以包括磁盘、光盘、固态驱动器等。示例性可移动存储器可以包括闪光驱动器、软盘、光盘、内存卡、压缩盘、磁带等。示例性易失性读写内存可以包括随机存取内存(RAM)。示例性RAM可以包括动态RAM(DRAM)、双倍数据速率同步动态RAM(DDRSDRAM)、静态RAM(SRAM)、晶闸管RAM(T-RAM)和零电容RAM(Z-RAM)。示例性ROM可以包括掩模ROM(MROM)、可编程ROM(PROM)、可擦除可编程ROM(PEROM)、电可擦除可编程ROM(EEPROM)、光盘ROM(CD-ROM)，以及数字通用磁盘ROM等。在一些实施例中，存储设备150可以在云平台上实现。仅作为示例，该云平台 可以包括私有云、公共云、混合云、社区云、分布云、内部云、多层云等或其任意组合。
在一些实施例中，存储设备150可以连接到网络120以与MRI系统100的一个或以上组件(例如，MRI扫描仪110、处理设备140、终端130等)通信。MRI系统100的一个或以上组件可以经由网络120访问存储设备150中存储的数据或指令。在一些实施例中，存储设备150可以直接连接到MRI系统100的一个或以上组件或与之通信(例如，MRI扫描仪110、处理设备140、终端130等)。在一些实施例中，存储设备150可以是处理设备140的一部分。
应该注意的是，上述描述仅出于说明性目的而提供，并不旨在限制本说明书的范围。对于本领域普通技术人员而言，在本说明书内容的指导下，可做出多种变化和修改。可以以各种方式组合本说明书描述的示例性实施例的特征、结构、方法和其他特征，以获取另外的和/或替代的示例性实施例。例如，MRI系统100还可以包括连接到MRI系统100(例如，MRI扫描仪110、处理设备140、终端130、存储设备150等)的一个或以上组件的一个或以上电源(图1中未示出)。
在一些实施例中，提供了一种计算设备200。该计算设备200的内部结构图可以如图2所示。计算设备200可以包括通过系统总线连接的处理器、存储器、通信接口、显示屏和输入装置。其中，计算设备200的处理器可以用于提供计算和控制能力。例如，可以执行本申请中一些实施例所示的梯度灵敏度校正方法。计算设备200的存储器可以包括非易失性存储介质、内存储器。该非易失性存储介质可以存储有操作系统和计算机程序。该内存储器可以为非易失性存储介质中的操作系统和计算机程序的运行提供环境。计算设备200的通信接口可以用于与外部的终端进行有线或无线方式的通信，无线方式可以通过WIFI、运营商网络、NFC(近场通信)或其他技术实现。该计算机程序被处理器执行时可以实现梯度灵敏度校正方法。计算设备200的显示屏可以是液晶显示屏或者电子墨水显示屏。计算设备200的输入装置可以是显示屏上覆盖的触摸层，也可以是计算设备200外壳上设置的按键、轨迹球或触控板，还可以是外接的键盘、触控板或鼠标等。
本领域技术人员可以理解，图2中示出的结构，仅仅是与本申请方案相关的部分结构的框图，并不构成对本申请方案所应用于MRI系统上的计算设备的限定，具体的计算设备可以包括比图中所示更多或更少的部件，或者组合某些部件，或者具有不同的部件布置。
图3是根据本说明书的一些实施例所示的示例性处理设备140的模块图。处理设备140可以包括获取模块310、确定模块320和校正模块330。
获取模块310可以用于获取模体的三维图像。三维图像可以利用MRI设备采集。模体可以在目标轴上具有已知的实际尺寸。关于获取三维图像的更多内容可以参考图4的步骤402 及其相关描述。
确定模块320可以用于对三维图像进行拟合，确定模体在目标轴上的拟合尺寸。拟合尺寸可以指基于拟合后的三维图像或三维模型确定的模体在目标轴上的尺寸。关于确定拟合尺寸的更多内容可以参考图4的步骤404及其相关描述。
校正模块330可以用于基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度。梯度灵敏度可以表征待扫描物和待扫描物的MR图像之间的尺度关系。关于校正梯度灵敏度的更多内容可以参考图4的步骤406及其相关描述。
上述梯度灵敏度校正系统中的各个模块可全部或部分通过软件、硬件及其组合来实现。上述各模块可以硬件形式内嵌于或独立于计算机设备中的处理器中，也可以以软件形式存储于计算机设备中的存储器中，以便于处理器调用执行以上各个模块对应的操作。
需要注意的是，以上对于梯度灵敏度校正系统及其模块的描述，仅为描述方便，并不能把本说明书限制在所举实施例范围之内。可以理解，对于本领域的技术人员来说，在了解该系统的原理后，可能在不背离这一原理的情况下，对各个模块进行任意组合，或者构成子系统与其他模块连接。例如，图3中披露的获取模块310、确定模块320和校正模块330可以是一个系统中的不同模块，也可以是一个模块实现上述的两个模块的功能。又例如，梯度灵敏度校正系统中各个模块可以共用一个存储模块，各个模块也可以分别具有各自的存储模块。诸如此类的变形，均在本说明书的保护范围之内。
图4是根据本说明书的一些实施例所示的示例性梯度灵敏度校正流程400的流程图。在一些实施例中，流程400可以由MRI系统100执行。例如，流程400可以以指令集(例如，应用程序)的形式存储在存储设备(例如，存储设备150)中。在一些实施例中，处理设备140(例如，图3中所示的一个或多个模块)可以执行指令集并相应指示MRI系统100的一个或多个组件执行流程400。
在MRI系统中，梯度磁场可以是由磁共振扫描仪的梯度线圈产生的、在空间中具有变化的强度的磁场。梯度磁场(包括梯度磁场Gx、Gy和Gz)可以叠加在由主磁体产生的主磁场上并使主磁场扭曲，使得待扫描物的质子的磁取向可以根据它们在梯度磁场内的位置而变化，从而将空间信息编码成由待扫描物的区域产生的磁共振(MR)信号(例如，回波信号)。梯度灵敏度可以表示待扫描物和对待扫描物进行MR扫描后获取的图像(例如，MR图像)之间的尺度关系。即，通过调整梯度灵敏度可以调整待扫描物在MR图像上的尺度。如果梯度灵敏度不准确，待扫描物在MR图像上的尺寸和待扫描物的实际尺寸就不一致，从而影响MRI系统的准确性。为了确保对象在采集的MR图像中的尺寸与对象的实际尺寸保持一致，需要对MRI设备的梯度灵敏度进行校正。在本申请中，对象在MR图像中的尺寸指的是基于 图像所确定的对象在实际物理空间中的尺寸。例如，可以基于图像中表示对象的部分的像素尺寸，以及图像和实际物理空间的对应关系，确定对象在实际物理空间中的尺寸。
传统技术中，大多使用球形模体，利用球形模体中心点上冠状面(Cor)、矢状面(Sag)、横断面(Tra)三个层面尺寸的一致性对MRI设备的梯度灵敏度进行校正。然而，在传统的梯度灵敏度校正方法中，对模体的摆位有着非常高的精度要求，即，需要尽可能将模体的中心与MRI系统的中心重合。一旦模体的摆位不符合精度要求，则会导致梯度灵敏度的校正不准确。此外，在悬臂式MRI系统(例如，动物MRI系统、婴儿MRI系统等)中，其扫描腔内径比较小而且长度较长，一般采用固定在扫描腔外的可伸缩的悬臂床将待扫描物送入扫描腔的磁体成像区域的中心位置。相比于一般的临床采用的滑轨床MRI系统，悬臂式MRI系统的悬臂末端下垂造成模体中心位置不易确定。因此，使用传统的梯度灵敏度校正方法需要耗费大量时间和精力才能将模体准确摆位，降低了MRI系统的使用效率和用户的使用体验。因此，需要提供有效的系统和方法用于进行梯度灵敏度校正。在一些实施例中，可以通过执行流程400的以下操作来校正梯度灵敏度。
在402中，处理设备140(例如，获取模块310)可以获取模体的三维图像。三维图像可以利用MRI设备采集。模体可以在目标轴上具有已知的实际尺寸。
模体可以用于对MRI系统进行检测的模体。例如，模体可以用于对MRI系统的图像性能的检测。在一些实施例中，对MRI系统进行的检测可以包括梯度灵敏度、空间均匀性、扫描层厚/层间距、准直定位系统验证、空间分辨力、几何畸变率(空间线性)、信噪比(SNR)、低对比灵敏度(低对比分辨力)、T1和T2驰豫时间值等测量内容。
在一些实施例中，模体可以由任意能够在磁场下产生磁共振信号的材料组成。例如，模体可以由单一材料制成。又例如，模体可以由多种材料制成。仅作为示例，模体可以包括玻璃外壳和液体(例如，水、盐溶液)。
在一些实施例中，模体可以具有固定的形状。例如，模体可以具有规则形状(例如，球形、圆柱形、长方体形、正方体形等)和不规则形状。因此，处理设备140可以基于模体的形状，获取模体在目标轴上的实际尺寸。在一些实施例中，目标轴可以包括以MRI系统(例如，MRI扫描仪110)的磁体成像区域的中心位置(例如，等中心点)为原点、以空间正交的三轴分别作为三轴方向建立的坐标系所对应的三个坐标轴。例如，目标轴可以包括图1中所示的坐标系的X轴、Y轴和Z轴。
在一些实施例中，模体可以是球体模体。由于球体模型的球心到球面上每一点的距离均等于球体的半径，处理设备140可以基于球形模体的半径确定球形模体在目标轴上的实际尺寸。并且，球形模体可以放置在磁体成像区域的任意位置，无需将球体模型的中心放置在 磁体成像区域的中心位置。
当模体为非球形模体(例如，圆柱形模体、长方体形模体、正方体形模体等)时，可以先对模体进行摆位，再确定模体在目标轴上的实际尺寸。仅作为示例，如图8所示，模体为圆柱形模体，可以使圆柱形模体的中心点和MRI系统(例如，MRI扫描仪110)的磁体成像区域的中心位置(即，点O)重合，使圆柱形模体的竖直方向和MRI系统的Z轴平行，并且使圆柱形模体的水平截面和MRI系统的XZ平面平行，从而完成圆柱形模体的摆位。相应地，处理设备140可以确定圆柱形模体在目标轴上的实际尺寸。具体地，处理设备140可以将圆柱形模体的底面的直径确定为圆柱形模体在X轴和Z轴上的实际尺寸，并且将圆柱形模体的高尺寸确定为圆柱形模体在Y轴上的实际尺寸。在一些实施例中，非球形模体的摆位可以通过用户(例如，医生、技师等)的判断确定。在一些实施例中，处理设备140可以在扫描床上预先设置标记物，该标记物可以用于确定模体的摆位是否准确。例如，处理设备140可以根据模体和标记物的位置关系(例如，平行、重合)确定模体的摆位是否准确。
模体的三维图像可以用来表征模体的三维立体信息(例如，三维结构特征)。在一些实施例中，三维图像可以指利用MRI设备(例如，MRI扫描仪110)采集的磁共振图像。例如，处理设备140可以通过MRI设备获取模体的MRI数据，根据MRI数据重建三维MR图像。或者处理设备140可以根据MRI数据重建二维MR图像。处理设备140可以进一步对二维MR图像进行三维重建，从而获取模体的三维图像。
仅作为示例，可以使用多片层扫描协议对球形模体进行扫描，从而获取球形模体的三维图像。具体地，多片层扫描协议可以使MRI设备对球形模体进行多层扫描，从多个层次获取球形模体的三维图像，确保了获取的球形模体的三维图像的准确度。需要说明的是，本实施例中的球形模体的三维图像为重建后的图像，图像中表征的是球形模体的三维立体信息。通过使用多片层扫描协议对模体进行准确地扫描，可以获取从多个片层进行扫描得到的模体的三维图像，从而提高了三维图像的准确性，进而提高了梯度灵敏度校正的准确性。
在一些实施例中，可以使用对磁场的均匀性不敏感的脉冲序列(例如，常规自旋回波序列、快速自旋回波序列等)对模体进行扫描，从而降低磁场不均匀对MR成像的影响。
在一些实施例中，处理设备140可以直接从MRI设备(例如，MRI扫描仪110)获取模体的三维图像。或者，处理设备140可以从存储模体的三维图像的存储设备(例如，存储设备150)获取模体的三维图像。本实施中对获取模体的三维图像的具体时间和步骤不加以限制，只要能够通过对模体进行磁共振成像得到模体的三维图像即可。
在一些实施例中，处理设备140可以在获取模体的三维图像后进行预处理操作(例如，尺寸调整、图像重采样、图像归一化等)。处理设备140可以进一步对预处理后的三维图像 执行流程400中的其他步骤。出于示例目的，下文以原始的三维图像为例描述流程400的执行过程。
在404中，处理设备140(例如，确定模块320)可以对三维图像进行拟合，确定模体在目标轴上的拟合尺寸。
拟合尺寸可以指基于拟合后的三维图像或三维模型确定的模体在目标轴上的尺寸。
在一些实施例中，处理设备140可以利用预设的拟合算法对模体的三维图像进行拟合，得到拟合后的三维图像或模型。例如，处理设备140可以基于三维图像，对模体进行重建。进一步地，处理设备140可以基于拟合后的三维图像或模型，确定模体在目标轴上的拟合尺寸。可以理解的是，以磁体成像区域的中心位置为原点、以空间正交的三轴分别作为三轴方向建立的坐标系中每点的坐标是可以获取的。即，处理设备140可以基于拟合后的图像，确定模体在目标轴上的拟合尺寸。
以模体为球形模体为例，处理设备140可以利用预设的拟合算法对球形模体的三维图像进行拟合(例如，椭球拟合)，即基于球形模体的三维图像拟合出一个球体(例如，椭球或标准球体)，从而基于拟合的球体，获取球体的目标轴的拟合尺寸。例如，如果基于球形模体的三维图像拟合出一个椭球，处理设备140可以基于坐标系中每点的坐标，获取椭球的最长轴的拟合尺寸、椭球的最短轴的拟合尺寸，以及同时与最长轴、最短轴相互垂直的轴的拟合尺寸。又例如，如果基于球形模体的三维图像拟合出一个标准球体，处理设备140可以通过坐标系中每点的坐标，获取标准球体的目标轴的拟合尺寸。
在一些实施例中，处理设备140可以基于三维图像，确定至少一个中心截面。中心截面可以指经过三维图像中模体的中心的截面，例如，与XY平面平行且经过模体的中心的第一截面、与XZ平面平行且经过模体的中心的第二截面、与YZ平面平行且经过模体的中心的第三截面。进一步地，处理设备140可以基于至少一个中心截面，确定模体在目标轴上的拟合尺寸。例如，基于第一截面，处理设备140可以获取模体在X轴和Y轴上的拟合尺寸；基于第二截面，处理设备140可以获取模体在X轴和Z轴上的拟合尺寸；基于第三截面，处理设备140可以获取模体在Y轴和Z轴上的拟合尺寸。在一些实施例中，处理设备140可以赋予每个拟合尺寸权重，通过加权的方式确定模体在目标轴上的拟合尺寸。例如，处理设备140可以分别赋予基于第一截面确定的模体在Y轴上的拟合尺寸和基于第三截面确定的模体在Y轴上的拟合尺寸权重(例如，权重1和权重2)，并且通过加权的方式确定模体在Y上的拟合尺寸。其中，权重1和权重2可以相同或不同。
在406中，处理设备140(例如，校正模块330)可以基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度。
梯度灵敏度可以表征待扫描物和待扫描物的MR图像之间的尺度关系。当对象(例如，模体)在采集的磁共振图像中的尺寸与对象的实际尺寸保持一致时，梯度灵敏度可以为准确的。当对象在采集的磁共振图像中的尺寸与对象的实际尺寸不一致时，梯度灵敏度可以为不准确的。例如，当球形模体在采集的磁共振图像中表现为椭球时，或者当模体在目标轴的拟合尺寸与模体在目标轴的实际尺寸不一致时，说明梯度灵敏度不准确。
在一些实施例中，处理设备140可以获取拟合尺寸和实际尺寸的相似度，并且基于相似度，对MRI设备的梯度灵敏度进行校正。相似度可以指拟合尺寸和实际尺寸的数值的接近程度。例如，若拟合尺寸和实际尺寸的相似度值较大(例如，模体在每个目标轴的拟合尺寸与对象在对应轴的实际尺寸的相似度值较大)，则说明拟合尺寸和实际尺寸较为相似，处理设备140可以对MRI设备的梯度灵敏度进行细微地调整或者保持当前的MRI设备的梯度灵敏度不变。若拟合尺寸和实际尺寸的相似度值较小(例如，模体在至少一个目标轴的拟合尺寸与对象在对应轴的实际尺寸的相似度值较小)，则说明拟合尺寸和实际尺寸相差较大，处理设备140可以对MRI设备的梯度灵敏度进行大幅度调整，直至拟合尺寸和实际尺寸相近。可以理解的是，在理想情况下，模体在目标轴上的拟合尺寸为模体的目标轴的实际尺寸。即，在理想情况下，拟合尺寸等于实际尺寸。
在一些实施例中，处理设备140可以确定拟合尺寸与实际尺寸之间的差别。处理设备140可以确定差别是否满足预设条件。如果差别不满足预设条件，处理设备140可以校正MRI设备的梯度灵敏度。如果差别满足预设条件，处理设备140可以不校正MRI设备的梯度灵敏度。即，不需要校正MRI设备的梯度灵敏度即可对对象进行磁共振成像。关于校正梯度灵敏度的更多内容可以参见图5及其相关描述。
在一些实施例中，处理设备140可以验证校正后的梯度灵敏度。例如，处理设备140可以基于具有校正后的梯度灵敏度的MRI设备采集的模体的三维验证图像，确定模体在目标轴上的验证拟合尺寸，并且基于验证拟合尺寸与实际尺寸的验证差别，验证校正后的梯度灵敏度。关于验证梯度灵敏度的更多内容可以参见图6及其相关描述。
根据本说明书的一些实施例，可以基于拟合尺寸和实际尺寸，校正MRI设备的梯度灵敏度，从而提高梯度灵敏度的校正的准确性。其中，可以通过获取球形模体的三维图像，并且基于球形模体的三维图像确定球形模体在目标轴的拟合尺寸。由于球形的物理特性，球形模体可以放置在MRI系统的磁体成像区域的任意位置，即，球形模体的中心不需要与磁体成像区域的中心位置重合。由此，可以降低梯度灵敏度校正时对模体摆位的要求，提高了梯度灵敏度校正的准确度性和效率。此外，由于降低了校正时对模体摆位的要求，本说明书的一些实施例所提供的梯度灵敏度校正方法可以用于任意MRI系统，尤其是扫描腔小、不易对模 体进行摆位的MRI系统(例如，悬臂式MRI系统、动物MRI系统、婴儿MRI系统等)。
应当注意，以上关于流程400的描述仅出于说明的目的而提供，而不是旨在限制本说明书的范围。对于本领域的普通技术人员，可以在本说明书的指导下进行各种变化和修改。然而，这些变化和修改不脱离本说明书的范围。在一些实施例中，流程400可以通过一个或多个未描述的额外操作和/或省略一个或多个以上讨论的操作来完成。例如，验证梯度灵敏度后，处理设备140可以将校正后的梯度灵敏度存储在存储设备(例如，存储设备150)中，以便后续进行MRI扫描时使用。
图5是根据本说明书的一些实施例所示的示例性校正梯度灵敏度的流程500的流程图。在一些实施例中，流程500可以由MRI系统100执行。例如，流程500可以以指令集(例如，应用程序)的形式存储在存储设备(例如，存储设备150)中。在一些实施例中，处理设备140(例如，图3中所示的一个或多个模块)可以执行指令集并相应指示MRI系统100的一个或多个组件执行流程500。在一些实施例中，图4中的操作406可以通过执行流程500来实现。
在502中，处理设备140(例如，校正模块330)可以确定拟合尺寸与实际尺寸之间的差别。
所述差别可以表征拟合尺寸与实际尺寸之间的差异。
在一些实施例中，处理设备140可以根据拟合尺寸和实际尺寸的差值，确定拟合尺寸与实际尺寸之间的差别。例如，处理设备140可以分别确定模体在X轴上的拟合尺寸和模体在X轴上的实际尺寸的第一差值、模体在Y轴上的拟合尺寸和模体在Y轴上的实际尺寸的第二差值和/或模体在Z轴上的拟合尺寸和模体在Z轴上的实际尺寸的第三差值。处理设备140可以进一步基于第一差值、第二差值和第三差值确定拟合尺寸与实际尺寸之间的差别。例如，第一差值、第二差值和第三差值的差值和可以作为拟合尺寸与实际尺寸之间的差别。差值和越大，说明拟合尺寸和实际尺寸的差别越大；差值和越小，说明拟合尺寸和实际尺寸的差别越小。
在一些实施例中，处理设备140可以根据拟合尺寸和实际尺寸的比值，确定拟合尺寸与实际尺寸之间的差别。例如，处理设备140可以分别确定模体在X轴上的拟合尺寸和模体在X轴上的实际尺寸的第一比值、模体在Y轴上的拟合尺寸和模体在Y轴上的实际尺寸的第二比值和/或模体在Z轴上的拟合尺寸和模体在Z轴上的实际尺寸的第三比值。处理设备140可以进一步基于第一比值、第二比值和第三比值确定拟合尺寸与实际尺寸之间的差别。例如，第一比值、第二比值和第三比值的平均值可以作为拟合尺寸与实际尺寸之间的差别。平均值越靠近1，说明拟合尺寸和实际尺寸的差别越小；平均值越远离1，说明拟合尺寸和实际尺寸的差别越大。
在504中，处理设备140(例如，校正模块330)可以确定差别是否满足预设条件。
在一些实施例中，若差值满足预设条件，可以说明MRI设备的梯度灵敏度已调整至可接受范围内。也就是说，若差值满足预设条件，可以说明无需对MRI设备的梯度灵敏度进行调整。
在一些实施例中，预设条件可以包括与差别对应的阈值。例如，若差别为拟合尺寸和实际尺寸的差值(例如，上文所述的第一差值、第二差值和第三差值的差值和)，预设条件可以为差值小于预设差值阈值或者在预设差值范围内，例如，0.1毫米、0.2毫米、0.5毫米、1毫米、2毫米、5毫米等。又例如，若差别为拟合尺寸和实际尺寸的比值(例如，上文所述的第一比值、第二比值和第三比值的平均值)，预设条件可以为比值小于预设比值阈值或者在预设比值范围内，例如，0.95到1.05、0.9到1.1、0.85到1.15、0.8到1.2等。
当差值不满足预设条件时，处理设备140可以执行步骤506。在一些实施例中，步骤504可以省略，处理设备140可以直接执行步骤506。
在506中，处理设备140(例如，校正模块330)可以校正MRI设备的梯度灵敏度。
在一些实施例中，处理设备140可以基于差别校正MRI设备的梯度灵敏度。例如，根据磁共振的物理原理(例如，MRI系统的梯度磁场的特性)，处理设备140可以基于差别确定梯度灵敏度的校正值。仅作为示例，处理设备140可以预先获取梯度灵敏度和差别之间的关系(例如，线性关系)，再基于差别确定梯度灵敏度的校正值。进一步地，处理设备140可以基于校正值校正MRI设备的梯度灵敏度。仅作为示例，如果差别为拟合尺寸和实际尺寸的差值，处理设备140可以基于差值确定梯度灵敏度的校正值，并且将校正值和梯度灵敏度之和作为校正后的梯度灵敏度。如果差别为拟合尺寸和实际尺寸的比值，处理设备140可以基于比值确定梯度灵敏度的校正值，并且将校正值和梯度灵敏度之积作为校正后的梯度灵敏度。
在一些实施例中，处理设备140可以根据拟合尺寸和实际尺寸的差别对MRI设备的梯度灵敏度因子进行调整，以使差别满足预设条件。例如，若对MRI设备的梯度灵敏度因子进行调整后，拟合尺寸和实际尺寸的差别减小，则可以按照当前的调整方向继续对MRI设备的梯度灵敏度因子进行调整。又例如，若对MRI设备的梯度灵敏度因子进行调整后，拟合尺寸和实际尺寸的差别增大，则可以调整当前的调整方向，以与之前调整方向相反的调整方向对MRI设备的梯度灵敏度因子进行调整。仅作为示例，若拟合尺寸和实际尺寸的差别(例如，上文所述的差值和)为0.8，对MRI设备的梯度灵敏度因子进行调整后，拟合尺寸和实际尺寸的差别为0.5，则可以继续以当前的调整方向继续对MRI设备的梯度灵敏度因子进行调整，以校正MRI设备的梯度灵敏度直至差别满足预设条件。又例如，若拟合尺寸和实际尺寸的差值为0.8，对MRI设备的梯度灵敏度因子进行调整后，拟合尺寸和实际尺寸的差值为0.9，则 可以调整当前的调整方向，以与之前调整方向相反的调整方向对MRI设备的梯度灵敏度因子进行调整，以校正MRI设备的梯度灵敏度直至差别满足预设条件。
根据本说明书的一些实施例，可以确定拟合尺寸和实际尺寸的差别是否满足预设条件，并且当差别不满足预设条件时可以校正MRI设备的梯度灵敏度。其中，根据差别可以准确地对MRI设备的梯度灵敏度因子进行调整，由此可以提高MRI设备的梯度灵敏度校正的准确度和效率。
应当注意，以上关于流程500的描述仅出于说明的目的而提供，而不是旨在限制本说明书的范围。对于本领域的普通技术人员，可以在本说明书的指导下进行各种变化和修改。然而，这些变化和修改不脱离本说明书的范围。在一些实施例中，流程500可以通过一个或多个未描述的额外操作和/或省略一个或多个以上讨论的操作来完成。
图6是根据本说明书的一些实施例所示的示例性的验证梯度灵敏度的流程600的流程图。在一些实施例中，流程600可以由MRI系统100执行。例如，流程600可以以指令集(例如，应用程序)的形式存储在存储设备(例如，存储设备150)中。在一些实施例中，处理设备140(例如，图3中所示的一个或多个模块)可以执行指令集并相应指示MRI系统100的一个或多个组件执行流程600。在一些实施例中，图4中的操作406可以通过执行流程600来实现。
在602中，处理设备140(例如，获取模块310)可以获取模体的三维验证图像。
三维验证图像可以利用具有校正后的梯度灵敏度的MRI设备采集。在一些实施例中，处理设备140可以通过流程400或流程500校正MRI设备的梯度灵敏度，并且利用具有校正后的梯度灵敏度的MRI设备采集模体的三维验证图像。三维验证图像的获取方式可以和步骤402所描述的三维图像的获取方式相似。
在604中，处理设备140(例如，确定模块320)可以基于三维验证图像进行拟合，确定模体在目标轴上的验证拟合尺寸。
验证拟合尺寸可以指基于拟合后的三维验证图像或三维模型确定的模体在目标轴上的尺寸。验证拟合尺寸的确定方式可以和步骤404所描述的拟合尺寸的确定方式相似。
在606中，处理设备140(例如，校正模块330)可以确定验证拟合尺寸与实际尺寸的验证差别。
在一些实施例中，处理设备140可以基于模体的形状，获取模体在目标轴上的实际尺寸。或者，处理设备140可以基于梯度灵敏度的校正流程(例如，流程400)，获取模体在目标轴上的实际尺寸。
验证差别可以表征验证拟合尺寸与实际尺寸之间的差异。验证差别的确定方式可以和 步骤502所描述的差别的确定方式相似。
在608中，处理设备140(例如，校正模块330)可以基于验证差别，验证校正后的梯度灵敏度。
验证差别是否满足预设条件的确定方式可以和步骤504所描述的差别是否满足预设条件的确定方式相似。
当验证差别满足预设条件，处理设备140可以确定梯度灵敏度校正完成。即，可以利用具有校正后的梯度灵敏度的MRI设备对对象进行磁共振成像。
当验证差别不满足预设条件，处理设备140可以确定需要对MRI设备的梯度灵敏度继续进行校正，直至校正后的梯度灵敏度完成验证，即，校正后的梯度灵敏度通过流程600。
根据本说明书的一些实施例，可以基于具有校正后的梯度灵敏度的MRI设备采集的三维验证图像，验证校正后的MRI设备的梯度灵敏度，从而保证梯度灵敏度校正的准确性。
应当注意，以上关于流程600的描述仅出于说明的目的而提供，而不是旨在限制本说明书的范围。对于本领域的普通技术人员，可以在本说明书的指导下进行各种变化和修改。然而，这些变化和修改不脱离本说明书的范围。在一些实施例中，流程600可以通过一个或多个未描述的额外操作和/或省略一个或多个以上讨论的操作来完成。
图7是根据本说明书的一些实施例所示的示例性校正梯度灵敏度的流程700的示意图。
如图7所示，可以利用MRI设备703采集球体模体702的三维图像704。对三维图像704进行拟合，可以确定球体模体702在目标轴上的拟合尺寸706。进一步地，可以获取球体模体702在目标轴上的实际尺寸708。基于拟合尺寸706和实际尺寸708，可以确定拟合尺寸706和实际尺寸708的差别710。进一步地，流程700可以执行步骤712，确定差别710是否满足预设条件。若差别710满足预设条件，流程700可以执行步骤716，以结束流程700。若差别710不满足预设条件，流程700可以执行步骤714，校正MRI设备703的梯度灵敏度。
具有校正后的梯度灵敏度的MRI设备703可以再次执行流程700，从而验证校正后的梯度灵敏度。具体地，具有校正后的梯度灵敏度的MRI设备703可以再次采集球体模体702的三维图像704(称为三维验证图像)。对三维验证图像再次进行拟合，可以确定球体模体702在目标轴上的拟合尺寸706(称为验证拟合尺寸)。基于验证拟合尺寸和实际尺寸708，可以确定验证拟合尺寸和实际尺寸708的差别710(称为验证差别)。进一步地，流程700可以执行步骤712，确定验证差别是否满足预设条件。若验证差别满足预设条件，流程700可以执行步骤716，以结束流程700。即，可以理解为校正后的梯度灵敏度完成验证。若验证差别不满足预设条件，流程700可以执行步骤714，继续校正MRI设备703的梯度灵敏度，直至校正后的梯度灵敏度完成验证。
本说明书一些实施例中，(1)基于拟合尺寸和实际尺寸，可以校正MRI设备的梯度灵敏度，从而提高梯度灵敏度的校正的准确性；(2)可以通过球形模体校正梯度灵敏度，由于球形的物理特性，球形模体可以放置在MRI系统的磁体成像区域的任意位置，即，球形模体的中心不需要与磁体成像区域的中心位置重合，可以降低梯度灵敏度校正时对模体摆位的要求，提高了梯度灵敏度校正的准确度性和效率；(3)由于降低了校正时对模体摆位的要求，本说明书的一些实施例所提供的梯度灵敏度校正方法可以用于任意MRI系统，尤其是扫描腔小、不易对模体进行摆位的MRI系统(例如，悬臂式MRI系统、动物MRI系统、婴儿MRI系统等)；(4)基于具有校正后的梯度灵敏度的MRI设备采集的三维验证图像，可以验证校正后的MRI设备的梯度灵敏度，从而保证梯度灵敏度校正的准确性。
本说明一些实施例还提供了一种MRI设备，该MRI设备包括：至少一个存储介质，存储计算机指令；至少一个处理器，执行该计算机指令，以实现本说明书所述的梯度灵敏度校正方法。有关更多技术细节可参见图1至图8的相关描述，在此不再赘述。
本说明一些实施例还提供了一种计算机可读存储介质，该存储介质存储计算机指令，当计算机读取该计算机指令时，计算机执行本说明书所述的梯度灵敏度校正方法。有关更多技术细节可参见图1至图8的相关描述，在此不再赘述。
需要说明的是，本申请所涉及的用户信息(包括但不限于用户设备信息、用户个人信息等)和数据(包括但不限于用于分析的数据、存储的数据、展示的数据等)，均为经用户授权或者经过各方充分授权的信息和数据。
上文已对基本概念做了描述，显然，对于本领域技术人员来说，上述详细披露仅仅作为示例，而并不构成对本说明书的限定。虽然此处并没有明确说明，本领域技术人员可能会对本说明书进行各种修改、改进和修正。该类修改、改进和修正在本说明书中被建议，所以该类修改、改进、修正仍属于本说明书示范实施例的精神和范围。
同时，本说明书使用了特定词语来描述本说明书的实施例。如“一个实施例”、“一实施例”、和/或“一些实施例”意指与本说明书至少一个实施例相关的某一特征、结构或特点。因此，应强调并注意的是，本说明书中在不同位置两次或多次提及的“一实施例”或“一个实施例”或“一个替代性实施例”并不一定是指同一实施例。此外，本说明书的一个或多个实施例中的某些特征、结构或特点可以进行适当的组合。
此外，除非权利要求中明确说明，本说明书所述处理元素和序列的顺序、数字字母的使用、或其他名称的使用，并非用于限定本说明书流程和方法的顺序。尽管上述披露中通过各种示例讨论了一些目前认为有用的发明实施例，但应当理解的是，该类细节仅起到说明的目的，附加的权利要求并不仅限于披露的实施例，相反，权利要求旨在覆盖所有符合本说明 书实施例实质和范围的修正和等价组合。例如，虽然以上所描述的系统组件可以通过硬件设备实现，但是也可以只通过软件的解决方案得以实现，如在现有的服务器或移动设备上安装所描述的系统。
同理，应当注意的是，为了简化本说明书披露的表述，从而帮助对一个或多个发明实施例的理解，前文对本说明书实施例的描述中，有时会将多种特征归并至一个实施例、附图或对其的描述中。但是，这种披露方法并不意味着本说明书对象所需要的特征比权利要求中提及的特征多。实际上，实施例的特征要少于上述披露的单个实施例的全部特征。
一些实施例中使用了描述成分、属性数量的数字，应当理解的是，此类用于实施例描述的数字，在一些示例中使用了修饰词“大约”、“近似”或“大体上”来修饰。除非另外说明，“大约”、“近似”或“大体上”表明所述数字允许有±20％的变化。相应地，在一些实施例中，说明书和权利要求中使用的数值参数均为近似值，该近似值根据个别实施例所需特点可以发生改变。在一些实施例中，数值参数应考虑规定的有效数位并采用一般位数保留的方法。尽管本说明书一些实施例中用于确认其范围广度的数值域和参数为近似值，在具体实施例中，此类数值的设定在可行范围内尽可能精确。
针对本说明书引用的每个专利、专利申请、专利申请公开物和其他材料，如文章、书籍、说明书、出版物、文档等，特此将其全部内容并入本说明书作为参考。与本说明书内容不一致或产生冲突的申请历史文件除外，对本说明书权利要求最广范围有限制的文件(当前或之后附加于本说明书中的)也除外。需要说明的是，如果本说明书附属材料中的描述、定义、和/或术语的使用与本说明书所述内容有不一致或冲突的地方，以本说明书的描述、定义和/或术语的使用为准。
最后，应当理解的是，本说明书中所述实施例仅用以说明本说明书实施例的原则。其他的变形也可能属于本说明书的范围。因此，作为示例而非限制，本说明书实施例的替代配置可视为与本说明书的教导一致。相应地，本说明书的实施例不仅限于本说明书明确介绍和描述的实施例。

Claims (20)

  1. 一种梯度灵敏度校正方法，由至少一个处理器执行，其特征在于，所述方法包括：
    获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸；
    对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸；以及
    基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
  2. 如权利要求1所述的方法，其特征在于，所述模体是球形模体。
  3. 如权利要求1所述的方法，其特征在于，所述模体是非球形模体，所述非球形模体基于所述目标轴进行摆位。
  4. 如权利要求1-3任一项所述的方法，其特征在于，所述基于所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸包括：
    基于所述三维图像，确定至少一个中心截面；以及
    基于所述至少一个中心截面，确定所述模体在所述目标轴上的拟合尺寸。
  5. 如权利要求1-4任一项所述的方法，其特征在于，所述基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度包括：
    确定所述拟合尺寸与所述实际尺寸之间的差别；
    确定所述差别是否满足预设条件；以及
    响应于所述差别不满足所述预设条件，校正所述MRI设备的梯度灵敏度。
  6. 如权利要求5所述的方法，其特征在于，所述方法进一步包括：
    验证所述校正后的梯度灵敏度。
  7. 如权利要求6所述的方法，其特征在于，所述验证所述校正后的梯度灵敏度包括：
    获取所述模体的三维验证图像，所述三维验证图像利用具有所述校正后的梯度灵敏度的所述MRI设备采集；
    基于所述三维验证图像进行拟合，确定所述模体在所述目标轴上的验证拟合尺寸；
    确定所述验证拟合尺寸与所述实际尺寸的验证差别；以及
    基于所述验证差别，验证所述校正后的梯度灵敏度。
  8. 如权利要求1-6任一项所述的方法，其特征在于，所述MRI设备包括悬臂床，所述模体被放置于所述悬臂床上。
  9. 如权利要求1-7任一项所述的方法，其特征在于，所述目标轴包括以所述MRI设备的磁体成像区域的中心位置为原点、以空间正交的三轴分别作为三轴方向建立的坐标系所对应的三个坐标轴。
  10. 一种梯度灵敏度校正系统，包括：
    存储设备，存储计算机指令；
    处理器，与所述存储设备相连接，当执行所述计算机指令时，所述处理器使所述系统执行下述操作：
    获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸；
    对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸；以及
    基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
  11. 如权利要求10所述的系统，其特征在于，所述模体是球形模体。
  12. 如权利要求10所述的系统，其特征在于，所述模体是非球形模体，所述非球形模体基于所述目标轴进行摆位。
  13. 如权利要求10-12任一项所述的系统，其特征在于，所述基于所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸包括：
    基于所述三维图像，确定至少一个中心截面；以及
    基于所述至少一个中心截面，确定所述模体在所述目标轴上的拟合尺寸。
  14. 如权利要求10-13任一项所述的系统，其特征在于，所述基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度包括：
    确定所述拟合尺寸与所述实际尺寸之间的差别；
    确定所述差别是否满足预设条件；以及
    响应于所述差别不满足所述预设条件，校正所述MRI设备的梯度灵敏度。
  15. 如权利要求14所述的系统，其特征在于，所述处理器使所述系统执行下述操作：
    验证所述校正后的梯度灵敏度。
  16. 如权利要求15所述的系统，其特征在于，所述验证所述校正后的梯度灵敏度包括：
    获取所述模体的三维验证图像，所述三维验证图像利用具有所述校正后的梯度灵敏度的所述MRI设备采集；
    基于所述三维验证图像进行拟合，确定所述模体在所述目标轴上的验证拟合尺寸；
    确定所述验证拟合尺寸与所述实际尺寸的验证差别；以及
    基于所述验证差别，验证所述校正后的梯度灵敏度。
  17. 如权利要求10-16任一项所述的系统，其特征在于，所述MRI设备包括悬臂床，所述模体被放置于所述悬臂床上。
  18. 如权利要求10-17任一项所述的系统，其特征在于，所述目标轴包括以所述MRI设备的磁体成像区域的中心位置为原点、以空间正交的三轴分别作为三轴方向建立的坐标系所对应的三个坐标轴。
  19. 一种计算机可读存储介质，所述存储介质存储计算机指令，当计算机读取所述计算机指令，所述计算机执行一种梯度灵敏度校正方法，包括：
    获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸；
    对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸；以及
    基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
  20. 一种梯度灵敏度校正系统，包括：
    获取模块，用于获取模体的三维图像，所述三维图像利用MRI设备采集，所述模体在目标轴上具有已知的实际尺寸；
    确定模块，用于对所述三维图像进行拟合，确定所述模体在所述目标轴上的拟合尺寸；以及
    校正模块，用于基于所述拟合尺寸和所述实际尺寸，校正所述MRI设备的梯度灵敏度。
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