Magnetic resonance imaging system and method

Abstract

Embodiments of the present specification provide a magnetic resonance imaging method and system. The method can include acquiring magnetic resonance imaging data of a target object. The magnetic resonance imaging data can be acquired by applying a magnetic resonance imaging pulse sequence to the target object. The magnetic resonance imaging pulse sequence can include a single radio frequency pulse for exciting a first substance in the target object and suppressing a second substance in the target object. The method can further include reconstructing a magnetic resonance image of the target object based on the magnetic resonance imaging data.

Description

[0001] Cross-references

[0002] This specification claims priority to U.S. Application No. 18 / 430,594, filed on February 1, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This specification relates to the field of magnetic resonance imaging (MRI), and more particularly to MRI systems and methods using MRI sequences including a monomial RFPulse with off-resonant spin-tipping effects (MOSTRF pulse for short). Background Technology

[0004] Magnetic resonance (MR) technology has been widely applied in various fields such as physics, chemistry, biology, and medicine. In some MR scans, it is necessary to specifically design RF pulses to excite a target substance (e.g., water) while suppressing other substances (e.g., fat, silica gel) within the target object. Therefore, it is desirable to provide an improved RF pulse design strategy that reliably excites the target substance while reliably suppressing other substances. Summary of the Invention

[0005] One aspect of this specification provides an MRI method. The method can be implemented on a computing device having at least one processor and at least one storage device. The method may include acquiring MRI data of a target object. The MRI data can be acquired by applying an MRI pulse sequence to the target object. The MRI pulse sequence may include a single radio frequency pulse for exciting a first substance in the target object and inhibiting a second substance in the target object. The method may further include reconstructing an MR image of the target object based on the MRI data. The waveform of the single radio frequency pulse can be determined by: generating a trapezoidal wave; generating an initial waveform by performing an exponential transformation on each point in the trapezoidal wave; and determining the waveform of the single radio frequency pulse by filtering the initial waveform.

[0006] In some embodiments, the phase of the single radio frequency pulse can be a constant value during application.

[0007] In some embodiments, the trapezoidal wave may include a top edge having a first length and a bottom edge having a second length, wherein the first length may be greater than zero and less than the second length.

[0008] In some embodiments, the center frequency of the single radio frequency pulse can be determined by: determining the duration and radio frequency field strength of the single radio frequency pulse; determining an estimated first frequency response curve of the first material relative to the single radio frequency pulse and an estimated second frequency response curve of the second material relative to the single radio frequency pulse based on the duration and the radio frequency field strength; and determining the center frequency of the single radio frequency pulse based on the estimated first frequency response curve and the estimated second frequency response curve.

[0009] In some embodiments, the estimated first frequency response curve and the estimated second frequency response curve may be determined by: determining peak width information based on the duration; determining peak frequency information based on the radio frequency field strength; and determining the estimated first frequency response curve and the estimated second frequency response curve based on the peak width information and the peak frequency information.

[0010] In some embodiments, determining peak frequency information based on the radio frequency field strength may include: determining a threshold strength associated with the radio frequency field strength, the threshold strength corresponding to a preset equivalent flip angle; and determining the peak frequency information based on the radio frequency field strength and the threshold strength.

[0011] In some embodiments, determining the center frequency of the single radio frequency pulse based on the estimated first frequency response curve and the estimated second frequency response curve may include: determining one or more estimated passbands based on the estimated first frequency response curve, in which the first material is excited; determining one or more estimated stopbands based on the estimated second frequency response curve, in which the second material is suppressed; determining an estimated overlap frequency range between the one or more estimated passbands and the one or more estimated stopbands; and determining the center frequency within the estimated overlap frequency range.

[0012] In some embodiments, a first frequency response curve of the first substance relative to the single radio frequency pulse may include one or more passbands in which the first substance is excited, each of the one or more passbands spanning a locally continuous frequency range. A second frequency response curve of the second substance relative to the single radio frequency pulse may include one or more stopbands in which the second substance is suppressed, at least one of the one or more stopbands being a semi-infinite frequency range. At least one of the one or more passbands and at least one stopband may have overlapping frequency ranges, and the center frequency of the single radio frequency pulse may be within the overlapping frequency range.

[0013] In some embodiments, the first substance and the second substance may be two different substances among water, fat, and silica gel.

[0014] In another aspect of the embodiments of this specification, an MRI method is provided. The method can be implemented on a computing device having at least one processor and at least one storage device. The method may include acquiring MRI data of a target object. The MRI data can be acquired by applying an MRI pulse sequence to the target object. The MRI pulse sequence may include a single radio frequency pulse for exciting a first substance in the target object and inhibiting a second substance in the target object. The method may further include reconstructing an MR image of the target object based on the MRI data. A first frequency response curve of the first substance relative to the single radio frequency pulse may include one or more passbands in which the first substance is excited, each of the one or more passbands spanning a locally continuous frequency range. A second frequency response curve of the second substance relative to the single radio frequency pulse may include one or more stopbands in which the second substance is excited, at least one of the one or more stopbands being a semi-infinite frequency range. At least one passband and at least one stopband may have overlapping frequency ranges, and the center frequency of the single radio frequency pulse may be within the overlapping frequency range.

[0015] In another aspect of this specification, an MRI system is provided. The system may include at least one storage device comprising a set of instructions; and at least one processor configured to communicate with the at least one storage device. When the set of instructions is executed, the at least one processor may be configured to instruct the system to perform operations. The operations may include acquiring MRI data of a target object. The MRI data is acquired by applying an MRI pulse sequence to the target object. The MRI pulse sequence may include single radio frequency pulses for exciting a first substance in the target object and inhibiting a second substance in the target object. The operations may further include reconstructing an MR image of the target object based on the MRI data. The waveform of the single radio frequency pulse may be determined by: generating a trapezoidal wave; generating an initial waveform by performing an exponential transformation on each point in the trapezoidal wave; and determining the waveform of the single radio frequency pulse by filtering the initial waveform.

[0016] Some additional features of this specification may be described in the following description. These additional features will become apparent to those skilled in the art through study of the following description and the accompanying drawings, or through an understanding of the production or operation of the embodiments. Features of some embodiments of this specification may be implemented and achieved by practicing or using various aspects of the methods, tools, and combinations set forth in the detailed examples discussed below. Attached Figure Description

[0017] This application will be further described through exemplary embodiments. These exemplary embodiments will be described in detail with reference to the accompanying drawings. These embodiments are non-limiting exemplary embodiments, in which the same numbers in the figures denote similar structures, wherein:

[0018] Figure 1 These are exemplary schematic diagrams of MRI shown according to some embodiments of this specification;

[0019] Figure 2 These are exemplary block diagrams of a processing apparatus according to some embodiments of this specification;

[0020] Figure 3 This is an exemplary flowchart illustrating the reconstruction of MRI images according to some embodiments of this specification;

[0021] Figure 4A This is an exemplary schematic diagram of the frequency response curves of the first and second substances relative to a single radio frequency pulse, as shown in some embodiments of this specification.

[0022] Figure 4B This is an exemplary schematic diagram of the frequency response curves of the first and second substances relative to a binomial off-resonant rectangular (BORR) pulse, as shown in some embodiments of this specification.

[0023] Figure 4C This is an exemplary schematic diagram of the frequency response curves of the first and second substances relative to a lipid-insensitive binomial off-resonant RF excitation (LIBRE) pulse, as shown in some embodiments of this specification.

[0024] Figure 5 This is an exemplary flowchart illustrating the process of determining a single radio frequency pulse waveform according to some embodiments of this specification;

[0025] Figure 6 This is an exemplary schematic diagram illustrating the determination of a single radio frequency pulse waveform according to some embodiments of this specification;

[0026] Figure 7 This is an exemplary flowchart illustrating the process of determining the center frequency of a single radio frequency pulse according to some embodiments of this specification;

[0027] Figure 8 This is an exemplary flowchart illustrating the process of determining a first frequency response curve and a second frequency response curve according to some embodiments of this specification;

[0028] Figure 9 These are exemplary schematic diagrams of the estimated first frequency response curve and the estimated second frequency response curve shown in some embodiments of this specification;

[0029] Figure 10 These are exemplary schematic diagrams of the estimated first frequency response curve and the estimated second frequency response curve shown in some embodiments of this specification;

[0030] Figure 11 These are exemplary schematic diagrams illustrating the estimated first frequency response curve and the estimated second frequency response curve according to some embodiments of this specification; and

[0031] Figure 12 These are exemplary schematic diagrams of computing devices according to some embodiments of this specification. Detailed Implementation

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. However, those skilled in the art should understand that this application can be implemented without these details. In other instances, well-known methods, procedures, systems, components, and / or circuits have been described at a relatively high level, but without detailed description, to avoid unnecessarily obscuring various aspects of this specification. It will be apparent to those skilled in the art that various changes can be made to the disclosed embodiments, and the general principles defined in this application can be applied to other embodiments and application scenarios without departing from the principles and scope of this application. Therefore, this application is not limited to the embodiments shown, but conforms to the broadest scope consistent with the scope of the claims.

[0033] The terminology used in this application is for the purpose of describing particular exemplary embodiments only and is not restrictive. The singular forms “a,” “an,” and “the” used in this application may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and “including” as used in this specification indicate only the presence of the stated features, integers, steps, operations, components, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, parts, and / or combinations thereof.

[0034] It is 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 to, or coupled to another unit, engine, module, or block, or communicate with another unit, engine, module, or block, or there may be an intermediate unit, engine, module, or block, unless the context clearly indicates otherwise. In this application, the term "and / or" may include any one or more of the relevant listed items or a combination thereof.

[0035] These and other features, characteristics, functions and operating methods of related structural elements, as well as component assembly and manufacturing economics, will become more apparent from the following description of the accompanying drawings, which form part of this application specification. However, it should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of this application. It should also be understood that the drawings are not drawn to scale.

[0036] The terms "pixel" and "voxel" are used interchangeably in this specification to refer to elements in an image. In this specification, the term "image" can refer to a two-dimensional (2D), three-dimensional (3D), or four-dimensional (4D) image (e.g., a time series of a three-dimensional image). In some embodiments, the term "image" can refer to an image of a region of a subject (e.g., a region of interest (ROI)). In some embodiments, an image can be a medical image, an optical image, etc.

[0037] In this specification, for the sake of brevity, a representation of an object (such as a body, a patient, or a portion thereof) in an image may be referred to as an "object." For example, for the sake of brevity, a representation of an organ, tissue (such as a heart, liver, or lung), or ROI in an image may be referred to as an organ, tissue, or ROI. Furthermore, for the sake of brevity, an image that includes a representation of an object or a portion thereof may be referred to as an image of the object or a portion thereof, or an image including the object or a portion thereof. Additionally, for the sake of brevity, an operation performed on a representation of an object or a portion thereof in an image may be referred to as an operation performed on the object or a portion thereof. For example, for the sake of brevity, segmentation of a portion of an image that includes a representation of an ROI may be referred to as ROI segmentation.

[0038] In some MR scans, it is necessary to specifically design radio frequency pulses to excite a primary substance (such as water) in the target object while suppressing a secondary substance (such as fat or silicone). Recently, BORR and LIBRE pulses have been proposed. However, both BORR and LIBRE pulses consist of two rectangular radio frequency sub-pulses, which places certain demands on the MRI equipment. Furthermore, the frequency range for suppressing the secondary substance is relatively small (e.g., the frequency range spans approximately 100 Hz), which reduces the applicability of the pulses. Therefore, an improved radio frequency pulse design strategy is desired to reliably excite the primary substance while reliably suppressing other substances.

[0039] Some embodiments of this specification relate to MRI systems and methods using MRI pulse sequences comprising a single radio frequency pulse (monomial radio frequency pulse) for exciting a first substance in a target object and suppressing a second substance in the target object. The single radio frequency pulse in some embodiments of this specification is referred to as a MOST pulse, and the waveform of the single radio frequency pulse can be determined by: generating a trapezoidal wave; generating an initial waveform by performing an exponential transformation on each point in the trapezoidal wave; and determining the waveform of the single radio frequency pulse by filtering the initial waveform. By using a single radio frequency pulse specifically designed according to some embodiments of this specification, the first substance in the target object can be effectively excited, and the second substance in the target object can be effectively suppressed, which can reduce noise and / or interference from the second substance, thereby improving the accuracy of MRI data and / or MR images. Furthermore, the specifically designed single radio frequency pulse is particularly suitable for applications in high and ultra-high fields. The single radio frequency pulse is not only insensitive to B0 and B1 inhomogeneities that are typically prominent in high fields, but also produces a relatively low specific absorption rate (SAR).

[0040] In some embodiments, a first frequency response curve of a first substance relative to a single radio frequency pulse may include one or more passbands in which the first substance is excited, and each of the one or more passbands may span a locally continuous frequency range. A second frequency response curve of a second substance relative to a single radio frequency pulse may include one or more stopbands in which the second substance is suppressed, and at least one of the one or more stopbands may be a semi-infinite frequency range. At least one of the one or more passbands may have an overlapping frequency range with at least one stopband, and the center frequency of the single radio frequency pulse may be within the overlapping frequency range. Since the frequency range of at least one stopband is semi-infinite, the entire passband of at least one passband may lie within at least one stopband, which can improve the length of the overlapping frequency range and improve the selectivity of the center frequency of the single radio frequency pulse and the applicability of the single radio frequency pulse.

[0041] Figure 1 This is an exemplary schematic diagram of an MRI system 100 according to some embodiments of this specification. Figure 1 As shown, the MRI system 100 may include an MRI device 110, a network 120, one or more terminals 130, a processing device 140, and a storage device 150. In some embodiments, the MRI device 110, processing device 140, storage device 150, and / or terminal 130 may be interconnected and / or communicate with each other via wireless connections (such as network 120), wired connections, or combinations thereof. The connections between the components in the MRI system 100 may be variable.

[0042] MRI device 110 can be configured to generate or provide image data (such as MRI data) by scanning a target object or at least a portion of the target object. For example, MRI device 110 can acquire MRI data (such as MR signals) by applying an MRI pulse sequence to the target object. In some embodiments, MRI device 110 may include a single-mode MRI device or a multi-mode MRI device. Exemplary multimodal MRI devices may include computed tomography-magnetic resonance imaging (CT-MRI) devices, positron emission tomography-magnetic resonance imaging (PET-MRI) scanners, etc., or any combination thereof. It should be noted that the MRI devices described below are for illustrative purposes only and are not intended to limit the scope of this specification.

[0043] In some embodiments, the MRI device 110 may include a magnet, a gradient coil assembly, a radio frequency coil assembly, etc. The magnet can generate a first magnetic field (also called a main magnetic field) to polarize the target object to be scanned. The gradient coil assembly can generate a second magnetic field (also called a gradient magnetic field). The gradient coil assembly may include an X-gradient coil, a Y-gradient coil, and a Z-gradient coil. The gradient coil assembly can generate one or more magnetic field gradient pulses in the X, Y, and Z directions relative to the main magnetic field to encode spatial information of the target object. The radio frequency coil assembly may include multiple radio frequency coils. The radio frequency coils may include one or more radio frequency transmitting coils and / or one or more radio frequency receiving coils. The radio frequency transmitting coils can transmit radio frequency pulses toward the target object. Under the coordinated action of the main magnetic field, the gradient magnetic field, and the radio frequency pulses, the MRI pulse sequence can excite one or more MR signals associated with the target object. The radio frequency receiving coils can acquire MR signals from the target object based on the MRI pulse sequence.

[0044] The target object may include a patient or other experimental subject (such as a laboratory mouse or other animal). In some embodiments, the target object may be a patient or a specific part, organ, and / or tissue of a patient. For example, the target object may include the head, neck, chest, heart, stomach, blood vessels, soft tissue, tumor, nodule, etc., or any combination thereof. In some embodiments, the target object may be non-biological. For example, the target object may include a phantom, artificial object, etc. In this specification, the terms "object" and "subject" are used interchangeably.

[0045] Network 120 may include any suitable network that facilitates the exchange of information and / or data between the MRI system 100 and the MRI system 100. In some embodiments, one or more components of the MRI system 100 (e.g., MRI device 110, terminal 130, processing device 140, storage device 150, etc.) may communicate information and / or data with one or more other components of the MRI system 100 via network 120. In some embodiments, network 120 may include one or more network access points.

[0046] Terminal 130 may include mobile device 130-1, tablet computer 130-2, laptop computer 130-3, etc., or any combination thereof. In some embodiments, mobile device 130-1 may include smart home device, wearable device, smart mobile device, virtual reality device, augmented reality device, etc., or any combination thereof. In some embodiments, terminal 130 may be part of processing device 140.

[0047] Processing device 140 can process data and / or information acquired from one or more components of MRI system 100 (MRI device 110, terminal 130, and / or storage device 150). For example, processing device 140 can acquire MRI data of a target object. As another example, processing device 140 can reconstruct MR images of the target object based on the MRI data. In some embodiments, processing device 140 can be a single server or a group of servers. The server group can be centralized or distributed. In some embodiments, processing device 140 can be local or remote. In some embodiments, processing device 140 can be implemented on a cloud platform. Exemplary cloud platforms may include private clouds, public clouds, hybrid clouds, community clouds, distributed clouds, inter-cloud clouds, multi-clouds, etc., or any combination thereof.

[0048] In some embodiments, the processing device 140 may be implemented by a computing device. For example, the computing device may include a processor, memory, input / output (I / O), and communication ports. In some embodiments, the processing device 140 or a portion thereof may be implemented by a portion of the terminal 130.

[0049] Storage device 150 may store data / information (e.g., MRI pulse sequences, MRI data, MR images, etc.) obtained from MRI device 110, terminal 130, and / or any other component of MRI system 100. In some embodiments, storage device 150 may include mass storage, removable storage, volatile read-write memory, read-only memory (ROM), etc., or any combination thereof. In some embodiments, storage device 150 may store one or more programs and / or instructions to perform the exemplary methods described herein.

[0050] In some embodiments, the MRI system 100 may include one or more additional components, and / or one or more components of the MRI system 100 described above may be omitted. Alternatively or concurrently, two or more components of the MRI system 100 may be integrated into a single component. One component of the MRI system 100 may be implemented on two or more sub-components.

[0051] Figure 2 This is an exemplary block diagram of a processing apparatus according to some embodiments of this specification. In some embodiments, the processing apparatus 140 may be coupled to a computer-readable storage medium (such as...) Figure 1 The processing device 140 communicates with the storage device 150 shown and executes instructions stored in a computer-readable storage medium. The processing device 140 may include an acquisition module 210 and a reconstruction module 220.

[0052] Acquisition module 210 can be configured to acquire MRI data of a target object. MRI data can be acquired by applying an MRI pulse sequence to the target object. The MRI pulse sequence may include single radiofrequency pulses used to excite a first substance in the target object and inhibit a second substance in the target object. Further description of acquiring MRI data can be found in other parts of this specification, such as operation 302 and its related descriptions.

[0053] The reconstruction module 220 can be configured to reconstruct MR images of a target object based on MRI data. Further descriptions of MR image reconstruction can be found in other parts of this specification, such as operation 304 and its related instructions.

[0054] In some embodiments, the processing device 140 may further include a waveform determination module 230. The waveform determination module 230 may be configured to determine the waveform of a single radio frequency pulse. For example, the waveform determination module 230 may generate a trapezoidal wave, generate an initial waveform by performing an exponential transformation on each point in the trapezoidal wave, and determine the waveform of the single radio frequency pulse by filtering the initial waveform. Further description of determining the waveform of a single radio frequency pulse can be found in other parts of this specification. For example, Figure 5 And related explanations.

[0055] In some embodiments, the processing device 140 may include one or more other modules, which may be omitted. For example, the processing device 140 may include a storage module for storing data generated by the modules in the processing device 140. In some embodiments, any two modules may be combined into one module, and any module may be divided into two or more units.

[0056] Figure 3 This is an exemplary flowchart illustrating the reconstruction of MR images according to some embodiments of this specification. Flowchart 300 can be... Figure 1 This is implemented in the MRI system 100 shown. For example, process 300 may be stored in storage device 150 as instructions (such as an application program) and invoked and / or executed by processing device 140.

[0057] In 302, the processing device 140 (e.g., acquisition module 210) can acquire MRI data of the target object.

[0058] MRI data can be acquired by applying an MRI pulse sequence to a target object. The MRI pulse sequence can be used to scan the target object and / or generate MRI data. For example, an MRI device (such as MRI device 110) can be instructed to apply an MRI pulse sequence to the target object and acquire MRI data (such as MR signals).

[0059] In some embodiments, an MRI pulse sequence can be defined by imaging parameters and an arrangement associated with image parameters in a time sequence. For example, an MRI pulse sequence may include or be associated with one or more parameters related to the radio frequency pulse, such as bandwidth (or frequency range), amplitude (or intensity), application time, duration, etc. As another example, an MRI pulse sequence may include or be associated with one or more parameters related to the gradient field, such as application direction, field strength, application time, duration, etc. Yet another example is that an MRI pulse sequence may be defined by one or more time-related parameters, such as repetition time (TR), acquisition time (TA), echo time (TE), inversion time (TI), etc.

[0060] In some embodiments, the MRI pulse sequence may include a single radio frequency pulse for exciting a first substance in the target object and inhibiting a second substance in the target object. The first substance refers to the target substance to be excited by the single radio frequency pulse, and the second substance refers to another substance to be inhibited. In some embodiments, the chemical shift of the first substance may be different from the chemical shift of the second substance. For example, the first substance and the second substance may be two different substances in water, fat, and silica gel. For example, assuming that the resonant frequency of water is the same as the center frequency of the MRI device 110 (i.e., the chemical shift of water is equal to 0 parts per million (ppm)), when the radio frequency field strength of the MRI device 110 is 3 Tesla (T), the chemical shift of fat relative to water may be -3.5 ppm, while the chemical shift of silica gel relative to water may be -4.7 ppm.

[0061] In some embodiments, the single radio frequency pulse can be a single radio frequency pulse with a partial resonant spin-flip effect (also known as a MOSTRF pulse). Since the center frequency of the single radio frequency pulse differs from the center frequency of the substance (such as water), the single radio frequency pulse can be a partial resonant radio frequency pulse. Accordingly, the substance signal excited by the single radio frequency pulse may be less effective than the substance signal excited by the resonant pulse. The partial resonant spin-flip effect refers to an effect that causes the substance signal to tilt towards the xy plane perpendicular to the Z direction.

[0062] In some embodiments, the phase of a single radiofrequency pulse can be a constant value during application. That is, when a single radiofrequency pulse is applied to a target object, the phase of the single radiofrequency pulse remains unchanged. For example, the phase of a single radiofrequency pulse can be any value within the range of -180 degrees to 180 degrees. It should be noted that a constant value corresponds to a single MRI pulse sequence. For example, a single radiofrequency pulse in a first MRI pulse sequence may correspond to a first phase, a single radiofrequency pulse in a second MRI pulse sequence may correspond to a second phase, and the first phase may be different from the second phase. In some embodiments, the phase of a single radiofrequency pulse in an MRI pulse sequence may be determined based on system default settings or manually set by a user (such as a doctor, technician, etc.).

[0063] By fixing the phase of a single radio frequency pulse to a constant value, the excitation effect corresponding to the single radio frequency pulse can be kept constant, thereby reducing the complexity of single radio frequency pulse applications and improving the efficiency and accuracy of MRI data acquisition.

[0064] In some embodiments, the processing device 140 can determine the waveform of a single radio frequency pulse. For example, the processing device 140 can generate a trapezoidal wave, generate an initial waveform by performing an exponential transformation on each point of the trapezoidal wave, and determine the waveform of the single radio frequency pulse by filtering the initial waveform. Further description of the determination of the single radio frequency pulse waveform can be found in other parts of this specification (e.g., Figure 5 and Figure 6 (and its description).

[0065] In some embodiments, the processing device 140 may determine the center frequency of a single radio frequency pulse. For example, the processing device 140 may determine the duration and radio frequency field strength of the single radio frequency pulse; based on the duration and radio frequency field strength, determine an estimated first frequency response curve of a first substance relative to the single radio frequency pulse and an estimated second frequency response curve of a second substance relative to the single radio frequency pulse; and determine the center frequency of the single radio frequency pulse based on the estimated first frequency response curve and the estimated second frequency response curve. Further description of determining the center frequency of a single radio frequency pulse can be found in other parts of this specification (e.g., Figure 7-11 (and its description).

[0066] By determining the phase, waveform, and center frequency of a single radio frequency pulse, the processing device 140 can determine the parameters of the single radio frequency pulse. In some embodiments, the processing device 140 can determine the parameters of the single radio frequency pulse based on information about the target object.

[0067] In some embodiments, processing device 140 may determine an MRI pulse sequence based on a single radio frequency pulse and a scanning protocol. The scanning protocol may include imaging parameters (e.g., one or more parameters related to gradient field, time, etc.). In some embodiments, the scanning protocol may be obtained from storage device 150 or an external data source. In some embodiments, the scanning protocol may be user-provided or automatically generated, for example, based on the MR scanner's default settings or automatically generated by a machine learning model.

[0068] In some embodiments, the first material has a first frequency response profile relative to a single radio frequency pulse, while the second material has a second frequency response profile relative to a single radio frequency pulse.

[0069] A frequency response profile reflects the response of a substance in a target object to a single radio frequency pulse at different frequencies (e.g., excited or suppressed state). For example, a frequency response profile can be represented by a curve or function that represents the signal strength of the substance excited by a single radio frequency pulse at different frequencies (representing the response condition). In some embodiments, the frequency response profile can be used to determine one or more passbands and one or more stopbands of the substance. The passband of a substance refers to the frequency range in which the substance is excited, and the stopband refers to the frequency range in which the substance is suppressed. For example, the passband of a substance can be the frequency range in which the signal strength of the substance is excited to a first percentage greater than or equal to the maximum signal strength of the substance. For example, the first percentage can be 90%, 92%, 95%, 98%, etc. In some embodiments, the first percentage is 95%. The stopband of a substance can be a frequency range in which the signal strength of the substance is suppressed to a second percentage less than or equal to the maximum signal strength of the substance. For example, the second percentage can be 10%, 8%, 5%, 2%, 1%, etc. In some embodiments, the second percentage is 5%. Taking water as an example, the passband of water is the frequency range in which the signal strength of water is excited to 95% or greater than or equal to the maximum signal strength of water, while the stopband of water is the frequency range in which the signal strength of water is suppressed to 5% or less than or equal to the maximum signal strength of water.

[0070] In some embodiments, a first frequency response curve of the first substance relative to a single radio frequency pulse may include one or more passbands in which the first substance is excited, and each of the one or more passbands may span a locally continuous frequency range. The locally continuous frequency range may also be referred to as a closed frequency range with a finite span. A second frequency response curve of the second substance relative to a single radio frequency pulse includes one or more stopbands in which the second substance is suppressed, and at least one of the one or more stopbands may be a semi-infinite frequency range. At least one passband and at least one stopband may have overlapping frequency ranges, and the center frequency of the single radio frequency pulse may be within the overlapping frequency range. In other words, the center frequency of the single radio frequency pulse is within the passband of the first substance and the stopband of the second substance; therefore, the single radio frequency pulse can effectively excite the first substance while effectively suppressing the second substance.

[0071] For example only, see Figure 4A , Figure 4A This is an exemplary schematic diagram showing the frequency response curves of the first and second substances relative to a single radio frequency pulse, according to some embodiments of this specification. Figure 4AAs shown, the horizontal axis represents the frequency offset (ΔF) relative to the center frequency of water, and the vertical axis represents the normalized signal strength (S). Norm The solid curve represents the frequency response curve of water, and the dashed curve represents the frequency response curve of fat. The unit on the horizontal axis is Hertz. The normalized signal strength of a substance is the ratio of the substance's signal strength to its maximum signal strength. If water is the first substance and fat is the second substance, then the first frequency response curve 410 of water relative to a single radio frequency pulse includes passbands 402 and 404 where water is excited, and each passband 402 and 404 spans a locally continuous frequency range. In some embodiments, two stopbands 406 and 407 with semi-infinite frequency ranges are located on either side of passbands 402 and 404, while a narrow stopband 408 is located between passbands 402 and 404. The center frequency of the narrow stopband 408 is the same as or substantially the same as the resonant frequency of water (e.g., 0 Hz). The second frequency response curve 420 of fat relative to a single radio frequency pulse includes stopbands 412 and 414 where fat is suppressed, each of which is a semi-infinite frequency range. The passband 402 is located within the stopband 412 and overlaps with the stopband 412 in a frequency range of 450. The center frequency of a single radio frequency pulse lies within the overlapping frequency range of 450. For example, the center frequency of the single radio frequency pulse can be determined to be 250 Hz to maximize the excitation of water while minimizing the suppression of fat. At this point, the signal strength corresponding to water is the highest, while the signal strength corresponding to fat is the lowest.

[0072] Similarly, if fat is the first substance and water is the second substance, then the passband 416 of fat lies within the stopband 406 of water, and they overlap in frequency range 460. The center frequency of a single radio frequency pulse lies within this overlap range 460. For example, the center frequency of the single radio frequency pulse can be set to -700Hz to excite fat as much as possible while suppressing water as much as possible. In this case, the signal strength corresponding to fat is the highest, while the signal strength corresponding to water is the lowest.

[0073] Therefore, by applying MRI pulse sequences including single radio frequency pulses, the first substance in the target object can be effectively excited, and the second substance in the target object can be effectively suppressed, thereby reducing the interference of the second substance on MRI data acquisition, thus improving the signal-to-noise ratio (SNR) and accuracy of MRI data.

[0074] See Figure 4B , Figure 4B This is an exemplary schematic diagram showing the frequency response curves of the first and second substances relative to a BORR pulse, according to some embodiments of this specification. Figure 4BAs shown, a portion of the passband 471 in the frequency response curve of water overlaps with the stopband 474 in the frequency response curve of fat in a frequency range 475. That is, the passband 471 is not located within the stopband 474. Therefore, the length of the overlapping frequency range 475 is shorter than that of the passband 471. Similarly, a portion of the passband 473 in the frequency response curve of fat overlaps with the stopband 472 in the frequency response curve of water in a frequency range 476. That is, the passband 473 is not located within the stopband 472. Therefore, the length of the overlapping frequency range 476 is shorter than that of the passband 473.

[0075] See Figure 4C , Figure 4C This is an exemplary schematic diagram showing the frequency response curves of the first and second substances relative to a LIBRE pulse, according to some embodiments of this specification. Figure 4C As shown, a portion of the passband 481 in the frequency response curve of water overlaps with the stopband 484 in the frequency response curve of fat in a frequency range 485. That is, the passband 481 is not located within the stopband 484. Therefore, the length of the overlapping frequency range 485 is shorter than that of the passband 481. Similarly, a portion of the passband 483 in the frequency response curve of fat overlaps with the stopband 482 in the frequency response curve of water in a frequency range 486. That is, the passband 483 is not located within the stopband 482. Therefore, the length of the overlapping frequency range 486 is shorter than that of the passband 483.

[0076] By comparison Figures 4A-4C Since the second material has a semi-infinite frequency range relative to at least one stopband of a single radio frequency pulse, and the passband of the first material usually has a large frequency overlap with at least one stopband (e.g., the entire passband of the first material can be within one stopband of the second material), the center frequency of the single radio frequency pulse can be selected within a large overlap frequency range. This can improve the selection range of the center frequency of the single radio frequency pulse, thereby improving the applicability of the single radio frequency pulse.

[0077] Furthermore, the specially designed single-RF pulse is particularly advantageous for applications in high and ultra-high fields. The single-RF pulse is not only insensitive to the B0 and B1 inhomogeneities that are typically prominent in high fields, but also exhibits a relatively low specific absorption rate (SAR) of RF energy due to its off-resonance characteristics. For example, since the frequency range of one or more stopbands is semi-infinite (i.e., the frequency range of one or more stopbands is relatively wide), even if the B0 field is inhomogeneous, the frequency corresponding to the B0 field can still fall within one or more stopbands, thus effectively suppressing secondary substances in the target object. In other words, the specially designed single-RF pulse is insensitive to B0 inhomogeneities. Even if the B1 field is inhomogeneous, the frequency response curve of the substance remains essentially the same. That is, the specially designed single-RF pulse is insensitive to B1 inhomogeneities.

[0078] In some embodiments, the processing device 140 may acquire MRI data from an MRI device (such as MRI device 110) or a storage device (such as storage device 150, a database, or an external storage device) that stores MRI data of the target object.

[0079] In 304, the processing device 140 (e.g., reconstruction module 220) can reconstruct an MR image of the target object based on MRI data.

[0080] MR images can be used for diagnosis and / or treatment.

[0081] In some embodiments, the processing device 140 can generate an MR image of a target object by reconstructing MRI data using an image reconstruction algorithm. For example, the processing device 140 can acquire k-space data by filling k-space based on MRI data using a transform operation (such as Fourier transform), and generate an MR image by reconstructing the k-space data using an image reconstruction algorithm. Exemplary image reconstruction algorithms may include Fourier reconstruction algorithms, parallel reconstruction algorithms (e.g., sensitivity coding algorithms, Generalized Auto-calibrating Partially Parallel Acquisition (GRAPPA) algorithms, iterative self-consistent parallel imaging reconstruction algorithms, simultaneous multi-slice imaging algorithms, three-dimensional parallel reconstruction algorithms, etc.), compressed sensing (CS) reconstruction algorithms, deep learning-based reconstruction algorithms, etc., or any combination thereof.

[0082] In some embodiments, the processing device 140 may further post-process the MR image. Example post-processing operations may include image warping, image enhancement, image denoising, image smoothing, or any combination thereof.

[0083] In some embodiments, the processing device 140 may display an MR image of the target object. For example, after reconstructing the MR image, the processing device 140 may display the MR image on a display screen (e.g., the display screen of terminal 130), and the user may perform diagnosis and / or treatment based on the MR image. Exemplary display screens may include liquid crystal displays, e-ink displays, etc.

[0084] According to some embodiments of this specification, MRI data of a target object can be acquired by applying an MRI pulse sequence to the target object. A single radio frequency pulse in the MRI pulse sequence can be used to excite a first substance in the target object and suppress a second substance in the target object. Therefore, interference from the second substance on MRI data acquisition can be reduced, which can improve the signal-to-noise ratio of the MRI data, thereby improving the accuracy of the MRI data and / or MRI images.

[0085] Figure 5 This is an exemplary flowchart of a process 500 for determining a single radio frequency pulse waveform according to some embodiments of this specification. In some embodiments, process 500 may be performed to achieve the same results as... Figure 3 At least a portion of the operation 302 described in the relevant description.

[0086] In 502, the processing device 140 (e.g., waveform determination module 230) can generate a trapezoidal wave.

[0087] A trapezoidal wave is a waveform with a trapezoidal shape. For example, a trapezoidal wave can consist of multiple points, each point corresponding to an amplitude and a phase. A trapezoidal wave may include a top side with a first length and a bottom side with a second length. The top side is parallel to the bottom side. The second length can be equal to the duration of a single radio frequency pulse. For example, the duration of a single radio frequency pulse can be in the range of 1 millisecond to 3 milliseconds.

[0088] In some embodiments, the first length can be greater than zero and less than the second length. For example, the first length can be greater than or equal to 0.1 times the second length and less than the second length. Another example is that the first length can be greater than or equal to 0.11 times the second length and less than or equal to 0.8 times the second length. Yet another example is that the first length can be greater than or equal to 0.12 times the second length and less than or equal to 0.6 times the second length. Yet another example is that the first length can be greater than or equal to 0.13 times the second length and less than or equal to 0.4 times the second length. Yet another example is that the first length can be greater than or equal to 0.14 times the second length and less than or equal to 0.2 times the second length. And yet another example is that the first length can be equal to 0.15 times the second length.

[0089] For example only, see Figure 6 The horizontal axis can represent time, and the vertical axis can represent amplitude (or signal strength). The top edge of the trapezoidal wave 610 has a first length τ′, and the bottom edge of the trapezoidal wave 610 has a second length τ. The first length τ′ is equal to 0.15 times the second length τ.

[0090] In some embodiments, the trapezoidal wave can be a symmetrical trapezoid. That is, the line connecting the center point of the top edge and the center point of the bottom edge is perpendicular to the top edge (or the bottom edge). Alternatively, the trapezoidal wave can be an asymmetrical trapezoid. That is, the line connecting the center point of the top edge and the center point of the bottom edge is not perpendicular to the top edge (or the bottom edge).

[0091] In some embodiments, the processing device 140 may generate a triangular waveform instead of a trapezoidal waveform. That is, the first length is equal to 0.

[0092] In 504, the processing device 140 (e.g., waveform determination module 230) can generate an initial waveform by performing an exponential transformation on each point in the trapezoidal wave.

[0093] For example, an exponential transformation can be performed on each point in the trapezoidal wave based on formula (1):

[0094]

[0095] Where I a This refers to the amplitude (or signal strength) at the midpoint of the trapezoidal wave; I b This refers to the amplitude (or signal strength) at the corresponding point in the initial waveform; q refers to the exponent of the exponential transform. As used herein, q is any value greater than 1, such as 1.1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.5, 3.0, 5.0, etc. In some embodiments, q equals 2.

[0096] In 506, the processing device 140 (e.g., waveform determination module 230) can determine the waveform of a single radio frequency pulse by filtering the initial waveform.

[0097] In some embodiments, the processing device 140 may use a filtering algorithm to filter the initial waveform. Exemplary filtering algorithms may include Gaussian filtering, median filtering, bilateral filtering, guided filtering, weighted least squares filtering, nonlocal mean filtering, and any combination thereof. For example, the processing device 140 may use a Gaussian filtering algorithm to filter the initial waveform.

[0098] For example only, see Figure 6 , Figure 6 This is an exemplary schematic diagram illustrating the determination of a single radio frequency pulse waveform according to some embodiments of this specification. For example... Figure 6 As shown, an exponential transformation can be performed on each point in the trapezoidal wave 610 based on formula (1) to generate the initial waveform 620. q equals 2. Then, the waveform 630 of the single radio frequency pulse can be determined by filtering the initial waveform 620.

[0099] Figure 7 This is an exemplary flowchart of a process 700 for determining the center frequency of a single radio frequency pulse, as shown in some embodiments of this specification. In some embodiments, process 700 may be performed to achieve the same... Figure 3 At least a portion of the operation 302 described in the relevant description.

[0100] In 702, the processing device 140 (e.g., acquisition module 210) can determine the duration and radio frequency field strength of a single radio frequency pulse.

[0101] As described above, the duration of a single radio frequency pulse is equal to the second length of the trapezoidal wave. As described in operation 502, the duration of the single radio frequency pulse can be determined when the trapezoidal wave is generated. In some embodiments, the duration of the single radio frequency pulse can be determined based on system default settings or manually set by the user. For example, the second length can be determined as any value in the range of 1 millisecond to 3 milliseconds.

[0102] The radio frequency field strength of a single radio frequency pulse can be less than or equal to the maximum radio frequency field strength of an MRI device (such as MRI device 110) that uses an MRI pulse sequence including a single radio frequency pulse. The maximum radio frequency field strength can be related to information about the MRI device (such as power, year of use, etc.). For example, the maximum radio frequency field strength can be 1.5T, 3T, 7T, 10T, etc.

[0103] In some embodiments, the radio frequency field strength of a single radio frequency pulse can be determined based on system default settings or manually set by the user. For example, the radio frequency field strength can be determined as any value within the range of 0 to the maximum radio frequency field strength (e.g., 1.5T, 3T, 7T, 10T, etc.). Further descriptions of the duration and radio frequency field strength of a single radio frequency pulse can be found in other parts of this specification (e.g., Figure 8 (and its explanation).

[0104] In 704, the processing device 140 (e.g., acquisition module 210) can determine the estimated first frequency response curve of the first substance relative to a single radio frequency pulse and the estimated second frequency response curve of the second substance relative to a single radio frequency pulse based on the duration and radio frequency field strength.

[0105] The predicted frequency response curve is the frequency response curve estimated based on the duration and radio frequency field strength.

[0106] In some embodiments, the processing device 140 may determine peak width information based on duration and peak frequency information based on radio frequency field strength. Further, the processing device 140 may determine an estimated first frequency response profile and an estimated second frequency response profile based on the peak width and peak frequency information. More detailed descriptions of determining the estimated first and estimated second frequency response profiles can be found in other parts of this specification (e.g., Figure 8-11 (and its description).

[0107] In 706, the processing device 140 (e.g., acquisition module 210) can determine the center frequency of a single radio frequency pulse based on a predicted first frequency response curve and a predicted second frequency response curve.

[0108] The center frequency of a single radiofrequency pulse can be expressed as the frequency offset relative to the center frequency of the MRI equipment or the absolute center frequency of the single radiofrequency pulse.

[0109] In some embodiments, the processing device 140 may determine one or more estimated passbands based on an estimated first frequency response curve, in which a first substance is excited, and determine one or more estimated stopbands based on an estimated second frequency response curve, in which a second substance is suppressed. The processing device 140 may determine an estimated overlap frequency range between one or more estimated passbands and one or more estimated stopbands, and determine a center frequency within the estimated overlap frequency range. Further description regarding the determination of the center frequency of a single radio frequency pulse can be found in other parts of this specification (e.g., Figure 8-11 (and its explanation).

[0110] According to some embodiments of this specification, an estimated first frequency response curve of a first substance relative to a single radio frequency pulse and an estimated second frequency response curve of a second substance relative to a single radio frequency pulse can be determined based on the duration and radio frequency field strength. Furthermore, the center frequency of the single radio frequency pulse can be determined based on the estimated first and second frequency response curves. In this way, the accuracy of determining the estimated first and second frequency response curves can be improved, which in turn improves the accuracy of determining the center frequency of the single radio frequency pulse, thereby improving the quality of the MRI image.

[0111] Figure 8 This is an exemplary flowchart of a process 800 for determining a predicted first frequency response curve and a predicted second frequency response curve, as shown in some embodiments of this specification. In some embodiments, process 800 may be executed to achieve the same results as described above. Figure 7 At least a portion of the operation 704 described in the relevant description.

[0112] In 802, processing device 140 (e.g., acquisition module 210) can determine peak width information based on the duration of a single radio frequency pulse.

[0113] Peak width information may include the peak width of each peak in the estimated frequency response curves (i.e., the estimated first frequency response curve and the estimated second frequency response curve). A peak refers to the passband peak (i.e., the peak of the passband) of the frequency response curve. In some embodiments, peak width information may be represented by the half-width at half-maximum (WHM) of each peak in the estimated frequency response curve.

[0114] In some embodiments, the duration of a single RF pulse may be related to the peak width information of the estimated frequency response curve. For example, if the duration of the single RF pulse is relatively long, the half-width at half maximum (WHM) of each peak in the estimated frequency response curve may be relatively small. Accordingly, the span of one or more passbands and one or more stopbands in the estimated frequency response curve may be relatively small. It should be noted that while the duration of the single RF pulse is related to the peak width information, the center frequency of each peak in the estimated frequency response curve is not affected by the duration of the single RF pulse. For example, when the duration of the single RF pulse changes, the distance between the center frequency of each of the one or more peaks corresponding to the first substance and the center frequency of each of the one or more peaks corresponding to the second substance remains unchanged.

[0115] In some embodiments, the duration may be inversely proportional to the peak width information (e.g., half-peak width) of each of one or more peaks. The inverse ratio can be a fixed value for a single radio frequency pulse. Therefore, the processing device 140 can determine the peak width information based on the duration of a single radio frequency pulse and the inverse ratio.

[0116] In 804, the processing device 140 (e.g., acquisition module 210) can determine peak frequency information based on the radio frequency field strength.

[0117] Peak frequency information refers to information related to the center frequency of each peak in the estimated frequency response curve. In some embodiments, peak frequency information may include the number of center frequencies (or passband peaks), the center frequency value of each peak, the amplitude (or signal strength) of each peak, or any combination thereof.

[0118] Radio frequency (RF) fields refer to electromagnetic fields generated by applying a single RF pulse. For example... Figure 6 As shown, the intensity of the radio frequency field changes as the amplitude (or signal strength) of a single radio frequency pulse changes during application. Therefore, the radio frequency field strength refers to the maximum intensity of the radio frequency field. In some embodiments, the radio frequency field strength can be related to the voltage of the radio frequency amplifier (used to apply the radio frequency pulse) of the MRI device (such as MRI device 110). The higher the voltage, the greater the radio frequency field strength can be.

[0119] In some embodiments, the radio frequency field strength of a single radio frequency pulse can be related to the shape of the predicted frequency response curve. For example, the radio frequency field strength of a single radio frequency pulse can affect the center frequency and amplitude (or signal strength) of each peak in the predicted frequency response curve.

[0120] In some embodiments, the processing device 140 may determine a threshold intensity related to the radio frequency field strength, and determine peak frequency information based on the radio frequency field strength and the threshold intensity. The threshold intensity may correspond to a preset equivalent flip angle.

[0121] The flip angle (or excitation angle) refers to the angle by which the macroscopic magnetization vector of a substance (such as the first substance or the second substance) deviates from its equilibrium state (i.e., the B0 direction of the MRI equipment). The preset equivalent flip angle refers to the excitation effect that causes the macroscopic magnetization vector of the substance to deviate from its equilibrium state by a preset flip angle. For example, if the preset equivalent flip angle is 90 degrees, the excitation effect can be a 90-degree deviation of the macroscopic magnetization vector of the substance from its equilibrium state. Since the excitation effect is the cumulative effect of a substance under a certain radio frequency field strength for a certain duration, once the duration and the preset equivalent flip angle are determined, the threshold intensity related to the radio frequency field strength can be determined.

[0122] In some embodiments, an excitation effect corresponding to the equivalent flip angle can be achieved using a radio frequency pulse with a threshold intensity corresponding to a preset equivalent flip angle. For example, when the preset equivalent flip angle is 90 degrees, a radio frequency pulse with a threshold intensity corresponding to 90 degrees can achieve an excitation effect of 90 degrees.

[0123] In some embodiments, the processing device 140 can determine peak frequency information by comparing the radio frequency field strength and the threshold strength. For example, if the radio frequency field strength is less than the threshold strength, the peak frequency information of the material may include: the estimated frequency response curve of the material includes a passband and a passband peak; two stopbands are located on both sides of the passband; the center frequency of the passband peak is the same as or substantially the same as the resonant frequency of the material; when the radio frequency field strength is less than the threshold strength, the excitation degree of the material by a single radio frequency pulse is positively correlated with the radio frequency field strength; when the radio frequency field strength is less than the threshold strength, the equivalent flip angle of a single radio frequency pulse is positively correlated with the radio frequency field strength; or any combination thereof.

[0124] For example, if the radio frequency field strength is much greater than the threshold strength (e.g., greater than or equal to twice the threshold strength), the peak frequency information of the material may include: the estimated frequency response curve of the material includes two passbands and two passband peaks; two stopbands with a semi-infinite frequency range are located on either side of the two passbands; the center frequency of each passband peak is different from the resonant frequency of the material; a third stopband (e.g., a narrow stopband) is located between the two passbands; the center frequency of the third stopband is the same as or substantially the same as the resonant frequency of the material; the equivalent flip angle of a single radio frequency pulse remains 90 degrees when the radio frequency field strength is equal to the maximum signal strength; or any combination thereof.

[0125] For example, if the radio frequency field strength is greater than the threshold strength but less than twice the threshold strength, the peak frequency information of the material can include: the estimated frequency response curve of the material includes two passbands and two passband peaks; two stopbands are located on both sides of the two passbands; the center frequency of each passband peak is different from the resonant frequency of the material; a half-stopband is located between the two passbands; the center frequency of the half-stopband is the same as or substantially the same as the resonant frequency of the material; when the radio frequency field strength is equal to the maximum signal strength, the equivalent flip angle of a single radio frequency pulse remains 90 degrees; or any combination thereof.

[0126] In 806, the processing device 140 (e.g., acquisition module 210) can determine the estimated first frequency response curve and the estimated second frequency response curve based on the peak width information and the peak frequency information.

[0127] For example, the predicted first frequency response curve and the predicted second frequency response curve can be determined by combining the peak width information, peak frequency information, and resonant frequency of the first and second substances. Taking water as an example, the number of center frequencies (or passband peaks) and the center frequency value of each peak can be determined based on the peak frequency information, and the half-width of each peak can be determined based on the peak width information, thereby determining the predicted frequency response curve of water.

[0128] In some embodiments, after determining the estimated first frequency response curve and the estimated second frequency response curve, the processing device 140 may determine the center frequency of a single radio frequency pulse based on the estimated first frequency response curve and the estimated second frequency response curve.

[0129] For ease of explanation, three examples are provided below for determining the predicted first frequency response curve, the predicted second frequency response curve, and the center frequency of a single radio frequency pulse.

[0130] Example 1:

[0131] See Figure 9 When the radio frequency field strength is less than the threshold strength, the estimated first frequency response curve 910 of water (exemplary first substance) and the estimated second frequency response curve 920 of fat (exemplary second substance) can be determined based on the peak width information and peak frequency information.

[0132] like Figure 9 As shown, the estimated first frequency response curve 910 for water includes an estimated passband 902 and two estimated stopbands 904 and 906 located on either side of the estimated passband 902. The estimated second frequency response curve 920 for fat includes an estimated passband 912 and two estimated stopbands 914 and 916 located on either side of the estimated passband 912. An estimated overlap frequency range 950 is determined between the estimated passband 902 and the estimated stopband 914, and the center frequency of a single radio frequency pulse relative to water can be within the estimated overlap frequency range 950. For example, the center frequency of a single radio frequency pulse relative to water can be located at the center frequency of the estimated overlap frequency range 950 (or the estimated passband 902 of water).

[0133] Similarly, if the first substance to be excited is fat and the second substance to be inhibited is water, the center frequency of a single radio frequency pulse relative to fat can be within the estimated overlap frequency range 960. For example, the center frequency of a single radio frequency pulse relative to fat can be located at the center frequency of the estimated overlap frequency range 960 (or the estimated passband 912 of fat).

[0134] Example 2:

[0135] See Figure 10 When the radio frequency field strength is greater than the threshold strength but less than twice the threshold strength, the estimated first frequency response curve 1010 of water (an exemplary first substance) and the estimated second frequency response curve 1020 of fat (an exemplary second substance) can be determined based on the peak width information and peak frequency information.

[0136] like Figure 10 As shown, the estimated first frequency response curve 1010 for water includes two estimated passbands 1002 and 1004, and two estimated stopbands 1006 and 1008 located on either side of the estimated passbands 1002 and 1004. The estimated second frequency response curve 1020 for fat includes two estimated passbands 1012 and 1014, and two estimated stopbands 1016 and 1018 located on either side of the estimated passbands 1012 and 1014. An estimated overlap frequency range 1050 is determined between the estimated passbands 1002 and 1016, and the center frequency of a single radio frequency pulse relative to water can be within the estimated overlap frequency range 1050. For example, the center frequency of a single radio frequency pulse relative to water can be located at the center frequency of the estimated overlap frequency range 1050 (or the estimated passband 1002 of water).

[0137] Similarly, if the first substance to be excited is fat and the second substance to be inhibited is water, the center frequency of a single radio frequency pulse relative to fat can be within the estimated overlap frequency range of 1060. For example, the center frequency of a single radio frequency pulse relative to fat can be located at the center frequency of the estimated overlap frequency range of 1060 (or the estimated passband of fat 1012).

[0138] Example 3:

[0139] See Figure 11 When the radio frequency field strength is greater than or equal to twice the threshold strength, the estimated first frequency response curve 1110 of water (exemplary first substance) and the estimated second frequency response curve 1120 of fat (exemplary second substance) can be determined based on the peak width information and peak frequency information.

[0140] like Figure 11As shown, the estimated first frequency response curve 1110 for water includes two estimated passbands 1102 and 1104, and two estimated stopbands 1106 and 1108 located on either side of the estimated passbands 1102 and 1104. A narrow estimated stopband 1109 lies between the estimated passbands 1102 and 1104, and the center frequency of the narrow estimated stopband 1109 is the resonant frequency of water (e.g., 0 Hz). The estimated second frequency response curve 1120 for fat includes two estimated passbands 1112 and 1114, and two estimated stopbands 1116 and 1118 located on either side of the estimated passbands 1112 and 1114. A narrow estimated stopband 1119 lies between the estimated passbands 1112 and 1114, and the center frequency of the narrow estimated stopband 1119 is the resonant frequency of fat (e.g., -440 Hz). A predicted overlap frequency range 1150 is determined between the predicted passband 1102 and the predicted stopband 1116, and the center frequency of a single radio frequency pulse relative to the water can be within the predicted overlap frequency range 1150. For example, the center frequency of a single radio frequency pulse relative to the water can be located at the center frequency of the predicted overlap frequency range 1150 (or the predicted passband 1102 of the water).

[0141] Similarly, if the first substance to be excited is fat and the second substance to be inhibited is water, the center frequency of the single radio frequency pulse relative to fat can be within the estimated overlap frequency range 1160. For example, the center frequency of the single radio frequency pulse relative to fat can be located at the center frequency of the estimated overlap frequency range 1160 (or the estimated passband 1112 of fat).

[0142] It should be noted that the descriptions of processes 300, 500, 700, and 800 are provided for illustrative purposes and are not intended to limit the scope of this specification. Various changes and modifications can be made by those skilled in the art based on the teachings of this specification. For example, processes 300, 500, 700, and 800 may be performed by one or more additional operations not described and / or not by one or more of the operations discussed. Furthermore, the order of operations for processes 300, 500, 700, and 800 is not intended to be limiting. However, these changes and modifications may not depart from the scope of protection of this specification.

[0143] Figure 12 This is an exemplary schematic diagram of a computing device 1200 according to some embodiments of this specification.

[0144] In some embodiments, one or more components of the MRI system 100 may be implemented on the computing device 1200. For example, a processing engine may be implemented on the computing device 1200 and configured to implement the functions and / or methods disclosed in this specification.

[0145] The computing device 1200 may include any components used to implement the MRI system 100 described herein. For example, the processing device 140 may be implemented by hardware, software programs, firmware, or any combination thereof on the computing device 1200. For illustrative purposes, Figure 12 Only one computer is described in this specification, but the computing functions associated with the MRI system 100 described in this specification can be implemented in a distributed manner through a set of similar platforms to distribute the processing load of the MRI system 100.

[0146] The computing device 1200 may include a communication port connected to a network for data communication. The computing device 1200 may include a processor (e.g., a central processing unit (CPU)), memory, a communication interface, a display unit, and an input device connected via a system bus. The processor of the computing device 1200 can be used to provide computing and control capabilities. The memory of the computing device 1200 may include non-volatile storage media and internal memory. The non-volatile storage media can store the operating system and computer programs. The internal memory can provide an environment for the execution of the operating system and computer programs in the non-volatile storage media. The communication interface of the computing device 1200 can be used for wired or wireless communication with external terminals. Wireless communication can be achieved through Wi-Fi, mobile cellular networks, near-field communication (NFC), etc. When the processor executes a computer program, a method for reconstructing MRI images can be implemented. The display unit of the computing device 1200 may include a liquid crystal display (LCD) or an electronic ink display. The input devices of the computing device 1200 may include a touch layer covering the display unit, devices disposed on the casing of the computing device 1200 (such as buttons, trackballs, touchpads, etc.), external keyboards, external touchpads, external mice, etc.

[0147] For ease of explanation, Figure 12 Only one processor is described herein. However, it should be noted that the computing device 1200 described in this specification may also include multiple processors. Therefore, the operations and / or method steps performed by one processor as described in this specification may also be performed jointly or separately by multiple processors. For example, if the processors of the computing device 1200 in this specification simultaneously execute operation A and operation B, it should be understood that operation A and operation B may also be performed jointly or separately by two or more different processors (e.g., the first processor executes operation A, the second processor executes operation B, or the first and second processors jointly execute operation A and operation B).

[0148] The basic concepts have been described above. Obviously, for those skilled in the art who have read this application, the above disclosure is merely illustrative and does not constitute a limitation of this application. Various modifications, improvements, and alterations may be made, which are intended for those skilled in the art, although not explicitly stated herein. Such modifications, improvements, and alterations are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0149] Furthermore, this application uses specific terms to describe embodiments of the application. For example, the terms "one embodiment" and / or "some embodiments" refer to specific features, structures, or characteristics related to an embodiment that are included in at least one embodiment of this specification. Therefore, it should be emphasized and understood that references to "one embodiment" or "another embodiment" two or more times in various parts of this specification do not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics may be appropriately combined in one or more embodiments of this specification.

[0150] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this application are not intended to limit the order of the processes and methods of this application. Although the foregoing disclosure has discussed some currently considered useful embodiments of the invention through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments of this application. For example, while the implementation of the various components described above can be embodied in a hardware device, it can also be implemented as a purely software solution, such as an installation on an existing server or mobile device.

[0151] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, the method of the present application should not be construed as reflecting an intention that the claimed object to be scanned requires more features than expressly recited in each claim. Rather, the subject of the invention should possess fewer features than in any single embodiment described above.

[0152] In some embodiments, numbers used to describe and claim certain embodiments of the present application representing quantities or properties should be understood to be modified in certain circumstances by the terms "approximately," "approximately," or "substantially." For example, unless otherwise stated, "approximately," "approximately," or "substantially" may represent a variation of ±20% of the value described. Accordingly, in some embodiments, numerical parameters used in the specification and claims are approximate values, which may be varied depending on the desired characteristics of individual embodiments. In some embodiments, numerical parameters are taken into account a specified number of significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of application in some embodiments of the present application are approximate values, in specific embodiments, such numerical values ​​are set as precisely as feasible.

[0153] Every patent, patent application, publication of a patent application, and other material, such as articles, books, specifications, publications, documents, things, and / or similar materials, cited herein are incorporated in their entirety by reference for all purposes, except for any related application archive history, any content inconsistent with or conflicting with this document, or any content that may limit the widest scope of the relevant claims present or thereafter. For example, if there is any inconsistency or conflict between the use of terminology in the description, definitions, and / or associated with any incorporated material and the terminology associated with this document, the terminology used in the description, definitions, and / or in this document shall prevail.

[0154] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other modifications may also fall within the scope of this application. Therefore, alternative configurations of the embodiments of this application are considered as examples and not limitations, and are regarded as consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly described and illustrated in this application.

Claims

1. A magnetic resonance imaging method, implemented on a computing device having at least one processor and at least one storage device, the method comprising: Magnetic resonance imaging data of a target object is acquired by applying a magnetic resonance imaging pulse sequence to the target object, the magnetic resonance imaging pulse sequence including a single radio frequency pulse for exciting a first substance in the target object and inhibiting a second substance in the target object; as well as The magnetic resonance image of the target object is reconstructed based on the magnetic resonance imaging data, wherein the waveform of the single radio frequency pulse is determined in the following manner: Generate a trapezoidal wave; An initial waveform is generated by performing an exponential transformation on each point of the trapezoidal wave; and The waveform of the single radio frequency pulse is determined by filtering the initial waveform.

2. The method according to claim 1, characterized in that, The phase of the single radio frequency pulse remains constant during application.

3. The method according to claim 1, characterized in that, The trapezoidal wave includes a top edge with a first length and a bottom edge with a second length, wherein the first length is greater than zero and less than the second length.

4. The method according to claim 1, characterized in that, The center frequency of the single radio frequency pulse is determined by the following method: Determine the duration and radio frequency field strength of the single radio frequency pulse; Based on the duration and the radio frequency field strength, the estimated first frequency response curve of the first substance relative to the single radio frequency pulse and the estimated second frequency response curve of the second substance relative to the single radio frequency pulse are determined. as well as The center frequency of the single radio frequency pulse is determined based on the estimated first frequency response curve and the estimated second frequency response curve.

5. The method according to claim 4, characterized in that, The estimated first frequency response curve and the estimated second frequency response curve are determined in the following manner: Peak width information is determined based on the duration. Peak frequency information is determined based on the radio frequency field strength; and Based on the peak width information and the peak frequency information, the estimated first frequency response curve and the estimated second frequency response curve are determined.

6. The method according to claim 5, characterized in that, The determination of peak frequency information based on the radio frequency field strength includes: Determine a threshold intensity related to the radio frequency field strength, the threshold intensity corresponding to a preset equivalent flip angle; and The peak frequency information is determined based on the radio frequency field strength and the threshold intensity.

7. The method according to claim 4, characterized in that, Determining the center frequency of the single radio frequency pulse based on the estimated first frequency response curve and the estimated second frequency response curve includes: Based on the predicted first frequency response curve, one or more predicted passbands are determined, in which the first substance is excited; Based on the estimated second frequency response curve, one or more estimated stopbands are determined, in which the second substance is suppressed; Determine the estimated overlap frequency range between the one or more estimated passbands and the one or more estimated stopbands; and Determine the center frequency within the estimated overlap frequency range.

8. The method according to claim 1, characterized in that, The first material's first frequency response curve relative to the single radio frequency pulse includes one or more passbands in which the first material is excited, each of the one or more passbands spanning a locally continuous frequency range. The second frequency response curve of the second substance relative to the single radio frequency pulse includes one or more stopbands in which the second substance is suppressed, and at least one of the one or more stopbands is a semi-infinite frequency range. At least one of the one or more passbands overlaps with at least one stopband in frequency range, and The center frequency of the single radio frequency pulse is within the overlap frequency range.

9. A magnetic resonance imaging method, implemented on a computing device having at least one processor and at least one storage device, characterized in that, The method includes: Acquiring magnetic resonance imaging (MRI) data of a target object, wherein the MRI data is acquired by applying an MRI pulse sequence to the target object, the MRI pulse sequence comprising single radio frequency pulses for exciting a first substance in the target object and inhibiting a second substance in the target object; and A magnetic resonance image of the target object is reconstructed based on the magnetic resonance imaging data, wherein... The first material's first frequency response curve relative to the single radio frequency pulse includes one or more passbands in which the first material is excited, and each of the one or more passbands spans a locally continuous frequency range. The second frequency response curve of the second substance relative to the single radio frequency pulse includes one or more stopbands in which the second substance is suppressed, and at least one of the one or more stopbands is a semi-infinite frequency range. At least one of the one or more passbands overlaps with at least one stopband in frequency range, and The center frequency of the single radio frequency pulse is within the overlap frequency range.

10. A magnetic resonance imaging system, characterized in that, The system includes At least one storage device including a set of instructions; as well as At least one processor is configured to communicate with the at least one storage device, wherein, when executing the set of instructions, the at least one processor is configured to direct the system to perform operations including: Acquiring magnetic resonance imaging (MRI) data of a target object, wherein the MRI data is acquired by applying an MRI pulse sequence to the target object, the MRI pulse sequence comprising single radio frequency pulses for exciting a first substance in the target object and inhibiting a second substance in the target object; and The magnetic resonance image of the target object is reconstructed based on the magnetic resonance imaging data, wherein the waveform of the single radio frequency pulse is determined in the following manner: Generate a trapezoidal wave; An initial waveform is generated by performing an exponential transformation on each point of the trapezoidal wave; and The waveform of the single radio frequency pulse is determined by filtering the initial waveform.

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