Multi-nuclear imaging sequence determination method, apparatus and magnetic resonance system

Abstract

The application relates to a multi-nucleus imaging sequence determination method, device and magnetic resonance system, wherein the multi-nucleus imaging sequence determination method comprises the following steps: acquiring an initial multi-nucleus imaging sequence, wherein the initial multi-nucleus imaging sequence comprises the pulse arrangement of several kinds of nuclei in a single repetition time; and adjusting the pulse arrangement of at least one kind of nucleus to optimize the initial multi-nucleus imaging sequence, thereby obtaining a target multi-nucleus imaging sequence. According to the application, the target multi-nucleus imaging sequence can be obtained, and the target multi-nucleus imaging sequence is a multi-nucleus imaging sequence obtained by combining and optimizing a plurality of single-nucleus imaging sequences. Therefore, the multi-nucleus imaging sequence can complete the scanning and imaging of multiple kinds of nuclei in one scanning and imaging process, and compared with sequentially imaging each kind of nucleus respectively, the scanning time of the sequence is shortened, and the imaging efficiency is improved. The application solves the problem that there is no imaging sequence determination method for multi-nuclear magnetic resonance imaging technology in the related art.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance imaging, and in particular to a method, apparatus and magnetic resonance system for determining multinucleus imaging sequences. Background Technology

[0002] Common magnetic resonance imaging techniques mainly target 1 H nuclides are used for imaging; other naturally occurring nuclides that can be used for magnetic resonance imaging include... 23 Na、 31 P, etc., can also be externally inputted. 19 F, 129 Xe, etc. Multinoid imaging can provide information on metabolism and distribution within the body, and has become a major research hotspot in recent years.

[0003] Multinucleus imaging adds temporal constraints compared to single-nucleus imaging. Because, in addition to... 1 H and 19 Nuclide magnetization is relatively low outside of F, resulting in lower signal-to-noise ratio at the same field strength; different nuclide coil emission efficiencies require different emission powers; different nuclide have different longitudinal magnetization relaxation time constants, etc. These reasons necessitate adjusting the imaging sequence of each nuclide during multi-nuclide imaging.

[0004] While imaging each nuclide sequentially allows for convenient independent setting of the imaging sequence for each nuclide, it significantly increases the scan time and makes the imaging more sensitive to motion artifacts. How to adjust the imaging sequence when imaging multiple nuclides simultaneously is a problem that needs to be solved in multi-nucleus imaging technology.

[0005] Existing methods for determining imaging sequences are mainly for single-nuclear magnetic resonance imaging (SMRI), and there are currently no methods for determining imaging sequences for multi-nuclear magnetic resonance imaging (MMRI). Summary of the Invention

[0006] This invention provides a method, apparatus, and magnetic resonance system for determining multinuclear imaging sequences, in order to address the problem that there is no method for determining imaging sequences for multinuclear magnetic resonance imaging technology in related technologies.

[0007] In a first aspect, the present invention provides a method for determining multi-nuclear imaging sequences, the method comprising:

[0008] An initial multinucleus imaging sequence is obtained, wherein the initial multinucleus imaging sequence includes pulse arrangements of several nuclides within a single repetition time.

[0009] The pulse arrangement of at least one of the nuclides is adjusted to optimize the initial multinucleus imaging sequence, thereby obtaining the target multinucleus imaging sequence.

[0010] In some embodiments, the plurality of said nuclides include a first nuclide and a second nuclide;

[0011] During a single repetition time of the initial multinucleus imaging sequence, the excitation pulses of the first nuclide are arranged before the excitation pulses of the second nuclide, and the acquisition time of the first nuclide is arranged after the acquisition time of the second nuclide.

[0012] In some embodiments, the plurality of said nuclides include a first nuclide and a second nuclide;

[0013] During a single repetition time of the initial multinucleus imaging sequence, the excitation pulse of the first nuclide is arranged before the excitation pulse of the second nuclide, and the acquisition time of the first nuclide is arranged between the excitation pulse of the second nuclide and the acquisition time.

[0014] In some embodiments, adjusting the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes:

[0015] The polarity of the layer selection gradient of the second nuclide is reversed and used as the compensation gradient of the layer selection gradient of the first nuclide.

[0016] In some embodiments, adjusting the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes:

[0017] A first phase encoding gradient is set between the excitation pulse of the first nuclide and the excitation pulse of the second nuclide;

[0018] A second phase encoding gradient is set between the excitation pulse of the second nuclide and the readout gradient of the first nuclide;

[0019] Wherein, the second phase encoding gradient constitutes the phase encoding gradient of the second nuclide, and the first phase encoding gradient and the second phase encoding gradient together constitute the phase encoding gradient of the first nuclide.

[0020] In some embodiments, adjusting the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes:

[0021] The dephase shift of the readout gradient of the first nuclide is moved forward before the excitation pulse of the second nuclide.

[0022] In some embodiments, adjusting the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes:

[0023] The dephase shift of the readout gradient of the first nuclide is moved forward to before the excitation pulse of the second nuclide;

[0024] The convergence phase of the readout gradient of the first nuclide is used as the de-phase of the readout gradient of the second nuclide, and the polarity of the convergence phase of the readout gradient of the second nuclide is reversed.

[0025] In some embodiments, the method further includes:

[0026] The number of acquisition codes for each nuclide is determined, wherein the number of acquisition codes is the number of codes for performing one complete Fourier acquisition of the nuclide, and the number of codes is either the number of phase codes or the number of layer codes.

[0027] The number of repetitions of the target multinucleus imaging sequence is determined based on the number of acquisition codes for several types of nuclides.

[0028] For each nuclide, the acquisition method of the nuclide is determined based on the relationship between the number of acquisition codes of the nuclide and the number of repetitions of the target multinucleus imaging sequence.

[0029] In some embodiments, determining the number of repetitions of the target multinucleus imaging sequence based on the number of acquisition codes for several of the said nuclides includes:

[0030] The number of repetitions of the target multi-nucleus imaging sequence is determined to be a common multiple of the number of acquisition codes for several nuclides;

[0031] Alternatively, when the number of acquisition codes for several nuclides is not proportional to each other, the number of repetitions of the target multinucleus imaging sequence is determined to be a multiple of the number of acquisition codes for at least one of the nuclides.

[0032] In some embodiments, determining the acquisition method of the nuclide based on the relationship between the number of acquisition codes of the nuclide and the number of repetitions of the target multi-nucleus imaging sequence includes:

[0033] When the number of nuclide acquisition codes is proportional to the number of repetitions of the target multinucleus imaging sequence, the nuclide undergoes full Fourier acquisition.

[0034] When the number of nuclide acquisition codes is not proportional to the number of repetitions of the target multinucleus imaging sequence, the nuclide performs full Fourier acquisition and partial Fourier acquisition, or performs partial Fourier acquisition.

[0035] Secondly, the present invention provides an apparatus for determining a multi-nucleus imaging sequence, the apparatus comprising:

[0036] The sequence acquisition module is used to acquire an initial multinucleus imaging sequence, wherein the initial multinucleus imaging sequence includes pulse arrangements of several nuclides within a single repetition time.

[0037] A sequence optimization module is used to adjust the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence and obtain a target multinucleus imaging sequence.

[0038] Thirdly, the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the multi-core imaging sequence determination method described in the first aspect above.

[0039] Fourthly, the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the multi-core imaging sequence determination method described in the first aspect above.

[0040] Fifthly, the present invention provides a magnetic resonance system including a control device configured to control the magnetic resonance system to perform scanning operations based on a pre-given multinuclear imaging sequence determined by the multinuclear imaging sequence determination method described in the first aspect above.

[0041] Compared with related technologies, the multinucleus imaging sequence determination method, apparatus, and magnetic resonance system provided in this invention can obtain a target multinucleus imaging sequence, which is a multinucleus imaging sequence obtained by combining and optimizing multiple single-nucleus imaging sequences. Therefore, this multinucleus imaging sequence can complete the scanning imaging of multiple nuclides in a single scanning process, shortening the scanning time and improving imaging efficiency compared to imaging each nuclide sequentially. This solves the problem in related technologies that there is no method for determining imaging sequences specifically for multinucleus magnetic resonance imaging technology.

[0042] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0044] Figure 1 This is a hardware structure block diagram of a terminal that executes the multi-core imaging sequence determination method of the present invention;

[0045] Figure 2 This is a flowchart of the multi-nucleus imaging sequence determination method in an embodiment of the present invention;

[0046] Figure 3 This is a multi-nucleus imaging sequence diagram in the first specific embodiment of the present invention;

[0047] Figure 4 This is a multi-nucleus imaging sequence diagram from a second specific embodiment of the present invention;

[0048] Figure 5 This is a multi-nucleus imaging sequence diagram in the third specific embodiment of the present invention;

[0049] Figure 6 This is a structural block diagram of the multi-nucleus imaging sequence determination device in an embodiment of the present invention. Detailed Implementation

[0050] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0051] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these” used in this application do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to these processes, methods, products, or devices. Words such as “connected,” “linked,” and “coupled” used in this application are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. Normally, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," "third," etc., used in this application are merely to distinguish similar objects and do not represent a specific order of objects.

[0052] The method embodiments provided in this example can be executed on a terminal, computer, or similar computing device. For example, it can run on a terminal. Figure 1 This is a hardware structure block diagram of the terminal executing the multi-core imaging sequence determination method of the present invention. For example... Figure 1 As shown, a terminal may include one or more ( Figure 1Only one is shown in the diagram. A processor 102 and a memory 104 for storing data are also included. The processor 102 may be, but is not limited to, a microprocessor (MCU) or a programmable logic device (FPGA). The terminal may also include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that… Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the terminal described above. For example, the terminal may also include components that are larger than... Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown are illustrated.

[0053] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the multi-core imaging sequence determination method in this invention. The processor 102 executes various functional applications and data processing by running the computer programs stored in the memory 104, thereby implementing the aforementioned method. The memory 104 may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0054] The transmission device 106 is used to receive or send data via a network. This network includes a wireless network provided by the terminal's communication provider. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 can be a Radio Frequency (RF) module used for wireless communication with the Internet.

[0055] This invention provides a method for determining multi-nuclear imaging sequences. Figure 2 This is a flowchart of the multi-nucleus imaging sequence determination method in an embodiment of the present invention. Figure 2 As shown, the process includes the following steps:

[0056] Step S210: Obtain an initial multinucleus imaging sequence, which includes pulse arrangements of several nuclides within a single repetition time.

[0057] Specifically, the initial multi-nucleus imaging sequence is first obtained, which is the sequence to be adjusted in this invention. The initial multi-nucleus imaging sequence is typically a combination of multiple single-nucleus imaging sequences. Existing single-nucleus imaging sequences mainly include nuclide excitation, spatial coding, and nuclide acquisition. The initial multi-nucleus imaging sequence includes pulse arrangements of several nuclides within a single repetition time (TR), that is, it includes a basic imaging sequence of at least two single nuclides. The pulse arrangement of a single nuclide refers to its basic imaging sequence. In a single-nucleus imaging sequence, the interval between two excitation pulses is called the repetition time. In the multi-nucleus imaging sequence of this invention, assuming the multi-nucleus imaging sequence includes a first nuclide and a second nuclide excited sequentially, the interval between the preceding excitation pulse of the first nuclide and the following excitation pulse of the second nuclide can be called the repetition time. Since a complete imaging sequence is composed of repeated basic imaging sequences, the basic imaging sequence is the smallest repeating unit in the complete imaging sequence. Figures 3 to 5 The figures shown are the basic imaging sequences in different embodiments. Therefore, a single repetition time can be understood as the duration of a single basic imaging sequence. Thus, the initial multinucleus imaging sequence including the pulse arrangement of several nuclides within a single repetition time means that the single basic imaging sequence of the initial multinucleus imaging sequence includes the pulse arrangement of several nuclides.

[0058] Step S220: Adjust the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence to obtain the target multinucleus imaging sequence.

[0059] Specifically, the initial multi-nuclear imaging sequence is a combination of multiple single-nuclear imaging sequences. Although each single-nuclear imaging sequence can be used independently, the combined sequences may interfere with each other. Therefore, it is necessary to adjust the pulse arrangement of at least one nuclide, that is, to optimize at least one single-nuclear imaging sequence to balance the mutual influence among the multiple single-nuclear imaging sequences, ultimately obtaining the target multi-nuclear imaging sequence. Simultaneously, the optimization objective also includes ensuring that the pulse arrangements of at least two nuclides partially overlap in the time dimension. That is, the excitation of one nuclide is set between the excitation and acquisition of another nuclide, thereby shortening the repetition time of the multi-nucleus imaging sequence.

[0060] Through the above steps, a target multi-nucleus imaging sequence can be obtained. This multi-nucleus imaging sequence is a combination and optimization of multiple single-nucleus imaging sequences. Therefore, this multi-nucleus imaging sequence can complete the scanning imaging of multiple nuclides in a single scan, which shortens the scanning time and improves the imaging efficiency compared to imaging each nuclide sequentially. This solves the problem of the lack of a method for determining imaging sequences for multi-nucleus magnetic resonance imaging technology in related technologies.

[0061] This invention optimizes multi-nuclear imaging sequences by setting the excitation of one nuclide between the excitation and acquisition of another nuclide, thereby shortening the repetition time of the multi-nuclear imaging sequence. This optimization method mainly includes two scenarios, as detailed in the following two embodiments.

[0062] In the first embodiment, the plurality of nuclides includes a first nuclide and a second nuclide; during a single repetition time of the initial multinucleus imaging sequence, the excitation pulse of the first nuclide is arranged before the excitation pulse of the second nuclide, and the acquisition time of the first nuclide is arranged after the acquisition time of the second nuclide.

[0063] Reference Figure 3 and Figure 4 In the diagram: nuclide 1 corresponds to the first nuclide, and nuclide N corresponds to the second nuclide. Specifically, in this embodiment, this optimization method is mainly applicable to two nuclides with significantly different echo times (TE). For example, if the echo time of the second nuclide is significantly shorter than that of the first nuclide, the excitation of the second nuclide can be set after the excitation of the first nuclide, and the acquisition of the second nuclide can be set before the acquisition of the first nuclide. Therefore, the echo time arrangement of the second nuclide falls within the echo time arrangement of the first nuclide. Thus, the repetition time of the multi-nucleus imaging sequence can be greatly shortened.

[0064] In the second embodiment, the plurality of nuclides includes a first nuclide and a second nuclide; during a single repetition time of the initial multinucleus imaging sequence, the excitation pulse of the first nuclide is arranged before the excitation pulse of the second nuclide, and the acquisition time of the first nuclide is arranged between the excitation pulse of the second nuclide and the acquisition time.

[0065] Reference Figure 5 In the diagram: nuclide 1 corresponds to the first nuclide, and nuclide N corresponds to the second nuclide. Specifically, in this embodiment, this optimization method is mainly applicable to two nuclides with small differences in echo times. For example, if the echo times of the first nuclide and the second nuclide are similar, the excitation of the second nuclide can be set between the excitation and acquisition of the first nuclide, and the acquisition of the second nuclide can be set after the acquisition of the first nuclide. Furthermore, the echo time arrangement of the second nuclide partially overlaps with that of the first nuclide. Therefore, the repetition time of the multi-nucleus imaging sequence can also be shortened to a certain extent.

[0066] It should be noted that the first and second embodiments described above are merely examples of the most basic optimization methods using two nuclides as examples. For combinations of more nuclides, the optimization methods in the first or second embodiments can be reused, or a combination of the optimization methods in the first and second embodiments can be used. For example, when several nuclides include a first nuclide, a second nuclide, and a third nuclide, in one embodiment, the echo time arrangement of the first nuclide is within the echo time arrangement of the second nuclide, and the echo time arrangement of the second nuclide is within the echo time arrangement of the third nuclide; in another embodiment, the echo time arrangements of the first and second nuclides partially overlap, and the echo time arrangements of the second and third nuclides partially overlap; while in other embodiments, the echo time arrangements of both the first and second nuclides are within the echo time arrangement of the third nuclide, and the echo time arrangement of the first nuclide partially overlaps with the echo time arrangement of the second nuclide.

[0067] On the one hand, in both the first and second embodiments, step S220, adjusting the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence, includes: reversing the polarity of the layer selection gradient of the second nuclide and using it as a compensation gradient for the layer selection gradient of the first nuclide.

[0068] Reference Figure 3 and Figure 5 In the figure: G1 represents the layer selection gradient of nuclide 1, and G2 represents the layer selection gradient of nuclide N. Specifically, this optimization method is an optimization of the layer selection gradient in two-dimensional imaging with accompanying layer selection. The excitation of the second nuclide follows the excitation of the first nuclide. Since it is an accompanying layer selection, the layer selection gradients and excitation pulses of each nuclide are synchronized, that is, the equivalent center time of the excitation pulse corresponds to the center time of the layer selection gradient, which means that the layer selection gradient of the second nuclide is after the layer selection gradient of the first nuclide. In order to shorten the excitation interval between the first and second nuclides, the layer selection gradient of the second nuclide is flipped and moved forward, so that part of the layer selection gradient of the second nuclide can be used as a compensation gradient for the layer selection gradient of the first nuclide. Thus, it is not necessary to set a separate compensation gradient for the layer selection gradient of the first nuclide. This not only simplifies the gradient arrangement of the layer selection gradient, but also shortens the excitation interval between the first and second nuclides, thereby shortening the minimum echo time of the second nuclide.

[0069] It should be further explained that, typically in single-nucleus imaging sequences, the layer selection gradient is positive, and its compensation gradient is negative. By reversing the polarity of the layer selection gradient of the second nuclide, its layer selection gradient becomes negative, and its compensation gradient becomes positive. Consequently, the polarity of the layer selection gradient of the second nuclide is the same as the polarity of the compensation gradient of the layer selection gradient of the first nuclide, thus replacing the compensation gradient of the layer selection gradient of the first nuclide. Furthermore, in embodiments with multiple nuclides, such as those where the excitation of the third and fourth nuclides occurs sequentially after the second nuclide, since the polarity of the layer selection gradient of the third nuclide is the same as the polarity of the compensation gradient of the layer selection gradient of the second nuclide (both are positive), the layer selection gradient of the third nuclide can be directly shifted forward to replace the compensation gradient of the layer selection gradient of the second nuclide. Simultaneously, the polarity of the layer selection gradient of the fourth nuclide can be reversed, and after reversal, it becomes the same as the polarity of the compensation gradient of the layer selection gradient of the third nuclide. Therefore, the layer selection gradient of the fourth nuclide can be reversed and shifted forward to replace the compensation gradient of the layer selection gradient of the third nuclide.

[0070] On the other hand, in both the first and second embodiments, step S220, adjusting the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence, includes: setting a first phase coding gradient between the excitation pulse of the first nuclide and the excitation pulse of the second nuclide; setting a second phase coding gradient between the excitation pulse of the second nuclide and the readout gradient of the first nuclide; wherein the second phase coding gradient constitutes the phase coding gradient of the second nuclide, and the first phase coding gradient and the second phase coding gradient together constitute the phase coding gradient of the first nuclide.

[0071] Reference Figures 3 to 5 Specifically, this optimization method targets the phase encoding gradient axis. Since the first phase encoding gradient is positioned between the excitation of the first and second nuclides, only the second phase encoding gradient constitutes the phase encoding gradient of the second nuclide. However, both the first and second phase encoding gradients occur after the excitation of the first nuclide, thus together they constitute the phase encoding gradient of the first nuclide.

[0072] It should be further explained that, in embodiments involving multiple nuclides, such as sequential excitation of the first, second, and third nuclides, a first phase coding gradient can be set between the excitation of the first and second nuclides, a phase coding gradient can be set between the excitation of the second and third nuclides, and a third phase coding gradient can be set after the excitation pulse of the third nuclide. In this case, the third phase coding gradient constitutes the phase coding gradient of the third nuclide, the second and third phase coding gradients together constitute the phase coding gradient of the second nuclide, and the first, second, and third phase coding gradients together constitute the phase coding gradient of the first nuclide.

[0073] Reference Figure 4It should also be noted that the optimization of the layer selection gradient axis in 3D imaging without layer selection is the same as the phase-encoded gradient optimization described above. Specifically, in 3D imaging without layer selection, the layer selection gradient axis contains the layer phase-encoded gradient, which is not synchronized with the excitation pulse. Its setting method is the same as that of the phase-encoded gradient on the phase-encoded gradient axis.

[0074] There are two main ways to optimize the readout gradient axis, corresponding to the first and second embodiments described above, respectively.

[0075] Furthermore, in the first embodiment, step S220, adjusting the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence, includes: shifting the dephase of the readout gradient of the first nuclide before the excitation pulse of the second nuclide.

[0076] Reference Figure 3 and Figure 4 In the figure: G3 represents the readout gradient of nuclide N, and G4 represents the readout gradient of nuclide I. Specifically, the readout gradients of each nuclide are synchronized with the acquisition time, meaning the convergence point of the readout gradient corresponds to the center of the acquisition time. Therefore, in this embodiment, the readout gradient of the first nuclide is generally located after the readout gradient of the second nuclide. To shorten the time interval between the acquisition time arrangements of the first and second nuclides, the de-phase of the readout gradient of the first nuclide is moved forward to between the excitation of the first and second nuclides. This can also be understood as setting the de-phase of the readout gradient of the first nuclide between the excitation of the first and second nuclides. This ensures that the convergence phase of the readout gradient of the first nuclide is immediately after the readout gradient of the second nuclide, thereby shortening the time interval between the acquisition time arrangements of the first and second nuclides, and ultimately shortening the overall repetition time of the multi-nucleus imaging sequence. Here, convergence phase refers to the process of different phases reaching the same phase (re-phase), and de-phase refers to the process of changing from the same phase to different phases (de-phase). The readout gradient consists of two parts: the phase-out gradient and the phase-converging gradient. Due to differences in translation, the phase-out gradient of the readout gradient can also be called the pre-phase of the readout gradient, and the phase-converging gradient of the readout gradient can also be called the re-converging gradient.

[0077] It should be further explained that, in embodiments with more nuclides, such as those containing a first nuclide, a second nuclide, and a third nuclide, the excitation order of the three nuclides is the first nuclide, the second nuclide, and the third nuclide, and the acquisition order of the three nuclides is the third nuclide, the second nuclide, and the first nuclide. In this case, the phase dephase of the readout gradient of the first nuclide can be set between the excitation of the first and second nuclides, and the phase dephase of the readout gradient of the second nuclide can be set between the excitation of the second and third nuclides.

[0078] Meanwhile, in the second embodiment, step S220, adjusting the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence includes: shifting the phase de-phase of the readout gradient of the first nuclide before the excitation pulse of the second nuclide; using the convergence phase of the readout gradient of the first nuclide as the phase de-phase of the readout gradient of the second nuclide, and reversing the polarity of the convergence phase of the readout gradient of the second nuclide.

[0079] Reference Figure 5 In the figure: G3 represents the readout gradient of nuclide 1, and G4 represents the readout gradient of nuclide N. Specifically, the readout gradients of each nuclide are synchronized with the acquisition time, meaning the convergence point of the readout gradient corresponds to the center of the acquisition time. Therefore, in this embodiment, the readout gradient of the first nuclide is generally located between the excitation pulse and the readout gradient of the second nuclide. In single-nuclide imaging sequences, the phase de-phase of the readout gradient is negative, and the convergence phase is positive. In this embodiment, the dephase of the readout gradient of the first nuclide is set between the excitation of the first and second nuclides, so that it will not affect the readout gradient of the second nuclide. At the same time, the polarity of the readout gradient of the second nuclide is reversed. At this time, the convergence phase of its readout gradient is negative, and the dephase is positive, which is the same as the convergence phase polarity of the first nuclide. Thus, the convergence phase of the readout gradient of the first nuclide can replace the dephase of the readout gradient of the second nuclide, so there is no need to set the dephase of the readout gradient of the second nuclide separately. This not only simplifies the gradient arrangement of the readout gradient axis, but also shortens the acquisition interval between the first and second nuclides.

[0080] In some embodiments, the multi-nucleus imaging sequence determination method further includes:

[0081] Step S230: Determine the number of acquisition codes for each nuclide. The number of acquisition codes is the number of codes for one complete Fourier acquisition of the nuclide. The number of codes is either the number of phase codes or the number of slice codes. Step S240: Determine the number of repetitions of the target multinucleus imaging sequence based on the number of acquisition codes for several nuclides. Step S250: For each nuclide, determine the acquisition method of the nuclide based on the relationship between the number of acquisition codes for the nuclide and the number of repetitions of the target multinucleus imaging sequence.

[0082] In this specific embodiment, during the spatial encoding process of each nuclide, the number of phase codes for each nuclide can be equal or unequal, and the number of layer phase codes can also be equal or unequal. Several different acquisition and encoding scenarios are described below.

[0083] In one embodiment, step S240, determining the number of repetitions of the target multinucleus imaging sequence based on the number of acquisition codes of several nuclides, includes: determining the number of repetitions of the target multinucleus imaging sequence as a common multiple of the number of acquisition codes of several nuclides; or, when the number of acquisition codes of several nuclides is not in a multiple relationship, determining the number of repetitions of the target multinucleus imaging sequence as a multiple of the number of acquisition codes of at least one nuclide.

[0084] Specifically, in one scenario, the number of acquisition codes for each nuclide is the same, meaning the number of codes acquired in a single complete Fourier transform of each nuclide is the same. In this case, the number of repetitions of the target multi-nucleus imaging sequence can be determined as a multiple of the number of acquisition codes for each nuclide. For example, if the number of acquisition codes for each nuclide is 128, then the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 128, in which case each nuclide undergoes one complete Fourier transform in a single imaging process. Alternatively, the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 256, in which case each nuclide undergoes two complete Fourier transforms in a single imaging process, and then the results are averaged.

[0085] In another scenario, the number of acquisition codes for each nuclide differs but exists in a multiple relationship. In this case, the number of repetitions of the target multi-nucleus imaging sequence can also be determined as a multiple of the number of acquisition codes for each nuclide. For example, the number of acquisition codes for the first nuclide is 256, the second nuclide is 128, and the third nuclide is 64. In one imaging process, if the number of repetitions of the target multi-nucleus imaging sequence is determined to be 512, then the first nuclide undergoes 2 complete Fourier transform acquisition processes and is then averaged, the second nuclide undergoes 4 complete Fourier transform acquisition processes and is then averaged, and the third nuclide undergoes 8 complete Fourier transform acquisition processes and is then averaged.

[0086] In both of the above scenarios, since the number of repetitions of the target multi-nucleus imaging sequence is a multiple of the number of acquisition codes for each nuclide, each nuclide can undergo at least one or more complete Fourier acquisition processes. Therefore, the acquisition method used for each nuclide is complete Fourier acquisition. In other words, when the number of acquisition codes for a nuclide is a multiple of the number of repetitions of the target multi-nucleus imaging sequence, the nuclide undergoes complete Fourier acquisition.

[0087] In other cases, the number of acquisition codes for each nuclide may not be a multiple of each other. In this case, the number of repetitions of the target multi-nucleus imaging sequence can be determined as a multiple of the number of acquisition codes for at least one nuclide. This can be achieved through various processing methods. For example, assuming the number of acquisition codes for the first nuclide is 256, the number for the second nuclide is 160, and the number for the third nuclide is 64.

[0088] In one processing method, a full Fourier transform acquisition is performed on one nuclide, while a combination of full and partial Fourier transform acquisitions is performed on the other nuclides. For example, the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 256. In this case, the first nuclide undergoes one full Fourier transform acquisition, the second nuclide undergoes one full Fourier transform acquisition, and partial Fourier transform acquisitions are performed in the remaining 96 acquisition codes. The third nuclide undergoes two full Fourier transform acquisitions, and then four full Fourier transform acquisitions. Alternatively, the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 160. In this case, the first nuclide undergoes partial Fourier transform acquisitions in the 160 acquisition codes, the second nuclide undergoes one full Fourier transform acquisition, the third nuclide undergoes two full Fourier transform acquisitions, and then partial Fourier transform acquisitions are performed in the remaining 32 acquisition codes.

[0089] In another approach, the number of repetitions of the target multi-nucleus imaging sequence can be determined as a common multiple of the number of acquisition codes for each nuclide. For example, the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 1280 times. In this case, the first nuclide undergoes 5 complete Fourier transform acquisitions, the second nuclide undergoes 8 complete Fourier transform acquisitions, and the third nuclide undergoes 20 complete Fourier transform acquisitions.

[0090] Of course, the two methods mentioned above can also be combined. For example, the number of repetitions of the target multi-nucleus imaging sequence can be determined to be 512 times. At this time, the first nuclide performs 2 complete Fourier acquisitions, the second nuclide performs 2 complete Fourier acquisitions, and in the remaining 192 acquisition codes, 2 partial Fourier acquisitions are performed, and the third nuclide performs 8 complete Fourier acquisitions.

[0091] In summary, when the number of nuclide acquisition codes is not proportional to the number of repetitions of the target multinucleus imaging sequence, the nuclide can undergo full Fourier acquisition and partial Fourier acquisition, or partial Fourier acquisition.

[0092] The technical solution of this invention will be described below through some specific multi-nuclear imaging sequences.

[0093] Reference Figure 3 In one specific embodiment, a specific multinucleus imaging sequence is provided, including N different nuclides ( Figure 3 (Only two types are shown in the figure). The time-bandwidth products of the excitation pulses for nuclide 1 and nuclide N are not equal; the numerical labels are for easy description of the gradient effects in each segment. In this example, nuclide N can achieve a shorter echo time. 23 Na etc T2 * Nuclides with shorter time constants are more advantageous.

[0094] The gradient intensities shown in the figure are determined by the field of view (FOV), bandwidth, and gyromagnetic ratio, and the formula is as follows:

[0095]

[0096]

[0097]

[0098]

[0099] In the formula: G1 is the layer-selective gradient intensity of nuclide 1, G2 is the layer-selective gradient intensity of nuclide N, G3 is the readout gradient intensity of nuclide N, and G4 is the readout gradient intensity of nuclide 1. The subscripts 1 and N represent nuclide 1 and nuclide N, respectively; BW represents bandwidth, with subscripts RF and ADC representing excitation and acquisition, respectively; γ represents the gyromagnetic ratio; FOV represents the field of view size, with subscripts SS and RO representing layer selection and readout, respectively. For example, BW... RF,1 The field of view (FOV) represents the bandwidth of the radio frequency excitation pulse of nuclide 1. RO,N The field of view indicates the readout direction of nuclide N.

[0100] The gradients are labeled with numbers in the figure. The first moment of each gradient with respect to time, which is also the area in the figure, is defined as follows:

[0101]

[0102] Where M represents the first moment (area) of the gradient with respect to time. The first moment of each gradient with respect to time can be calculated using the above formula.

[0103] In specific sequence design, the following relationships must be guaranteed:

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] The numerical subscripts represent the corresponding gradients. When the first moment is negative, it indicates that its polarity is opposite to that shown in the figure. The start / end times for calculating M1, M2, and M3 are the equivalent center times of the corresponding RF pulses; the calculation of M9, M... 10 M 11The start / end times of the time are the corresponding echo center times; the start and end times of M4, M5, M6, M7, and M8 are the times of gradient ramp-up and gradient zeroing, respectively.

[0111] Where: M PE,1,i M represents the first moment of nuclide 1 during its i-th phase encoding. PE,N,j This represents the first moment of nuclide N in its j-th phase encoding, which is specifically related to the K-space filling order. Taking the unidirectional K-space filling order as an example, its calculation formula is:

[0112]

[0113]

[0114] Where Res represents resolution, γ represents gyromagnetic ratio, and FOV represents field of view size; in the subscript PE, phase encoding is indicated, and 1 and N represent nuclide 1 and nuclide N, respectively.

[0115] Reference Figure 4 In one specific embodiment, another specific multi-nucleus imaging sequence is provided. Unlike the previous specific embodiment, Figure 3 The image shown is a multi-nuclear imaging sequence for two-dimensional imaging. Figure 4 The image shows a multi-nucleus imaging sequence for three-dimensional imaging. In two-dimensional imaging, each nuclide has an accompanying layer-selective gradient. In three-dimensional imaging, hard pulse excitation without an accompanying layer-selective gradient is often used.

[0116] The phase coding gradient and readout coding gradient settings for the multi-nucleus imaging sequence in this embodiment are the same as in the previous embodiment. The main difference lies in the layer phase coding gradient. The first moment of each layer phase coding gradient with respect to time should satisfy the following relationship:

[0117]

[0118]

[0119]

[0120]

[0121] Where Res represents resolution, γ represents gyromagnetic ratio, FOV represents field of view size; in the subscript PE, phase coding is indicated, 1 and N represent nuclide 1 and nuclide N respectively, and SPE represents layer phase coding.

[0122] Reference Figure 5In one specific embodiment, another specific multi-nucleus imaging sequence is provided. The acquisition time relationship of each nuclide in this multi-nucleus imaging sequence differs from that of the multi-nucleus imaging sequence described above. In this embodiment, the first moment of each gradient with respect to time needs to satisfy the following relationship:

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] Among them, M PE,1,i M represents the first moment of nuclide 1 during its i-th phase encoding. PE,N,j Let represent the first moment of nuclide N during its j-th phase encoding. In this example, the nuclides have similar echo times.

[0130] The three specific multinucleus imaging sequences described above were designed using the multinucleus imaging sequence determination method of this invention. During the encoding process of these multinucleus imaging sequences, the number of phase codes for each nuclide can be equal or unequal, and the number of layer phase codes can also be equal or unequal. This mainly falls into the following categories.

[0131] 1. The number of codes for each nuclide is equal.

[0132] 2. The number of codes for each nuclide is in a multiple relationship.

[0133] For example, if the encoding quantity of nuclide 1 is 256, the encoding quantity of nuclide 2 is 128, and the encoding quantity of nuclide 3 is 64, then in one imaging process, nuclide 1 undergoes the same encoding acquisition process X times and then averages the results; nuclide 2 undergoes 2*X times of averaging; and nuclide 3 undergoes 4*X times of averaging.

[0134] 3. The number of codes for each nuclide is not in a multiple relationship.

[0135] If the encoding number of nuclide 1 is 256, the encoding number of nuclide 2 is 160, and the encoding number of nuclide 3 is 64, then a completely identical repetition cannot be performed in a single imaging process. In this case, several repetitions plus partial Fourier transform acquisition can be used, and / or an appropriate number of repetitions can be selected to satisfy the multiple relationship.

[0136] A. Partial Fourier sampling: For example, nuclide 1 is sampled once (there are 256 repetitions with different codes); nuclide 2 is sampled once, and partial Fourier sampling is performed in the remaining 96 repetitions; nuclide 3 is sampled four times.

[0137] Alternatively, nuclide 1 can be sampled once in a partial Fourier transform (with 160 different encoding repetitions); nuclide 2 can be sampled once in a complete transform; nuclide 3 can be sampled twice in a complete transform, and then partially in a transform transform in the remaining 32 repetitions.

[0138] B. Select the number of repetitions, such as 5 complete collections for nuclide 1 (a total of 256*5 repetitions), 8 complete collections for nuclide 2, and 20 complete collections for nuclide 3.

[0139] C. Both are combined, such as nuclide 1 undergoing 2 complete acquisitions (at which point there are a total of 256*2 repetitions); nuclide 2 undergoing 2 complete acquisitions, and in the remaining 192 acquisitions, two partial Fourier acquisitions are performed; nuclide 3 undergoing 8 complete acquisitions.

[0140] Among these methods, the signal-to-noise ratio can be improved by averaging the data after performing more than one complete acquisition; partial Fourier acquisition is an existing technology and will not be elaborated upon; complete and partial acquisitions can be averaged using existing technologies; the principle of layer phase encoding is the same. Each nuclide undergoes the same number of acquisitions regardless of resolution.

[0141] As can be seen from the above description of the specific multinucleus imaging sequence, the multinucleus imaging sequence provided in this invention includes two or more nuclide excitations, spatial encoding, and acquisition within a single repetition time, and mainly includes the following characteristics:

[0142] 1. The pulse waveform, pulse width, and flip angle used for different nuclides during the excitation process can be the same or different.

[0143] 2. During the excitation process, when a certain nuclide is excited, only a corresponding layer selection gradient is applied on a single logic axis; or when a certain nuclide is excited, there is no accompanying layer selection gradient.

[0144] 3. During the excitation and collection processes, the gradient intensities used for each nuclide can be the same or different.

[0145] 4. During the excitation and acquisition processes, the gradient intensities used by each nuclide are located on the same logical axis.

[0146] 5. During the encoding process, the phase encoding gradient of each nuclide exists within the excitation pulse interval of each nuclide.

[0147] 6. During the encoding process, the number of phase codes for each nuclide can be equal or unequal, and the number of layer phase codes can be equal or unequal.

[0148] 7. During the acquisition process, the echo time and magnitude relationship of each nuclide can be changed by setting the readout gradient.

[0149] 8. During the excitation, encoding, and acquisition processes, each nuclide can be used with asymmetric radio frequency waveforms, partial Fourier encoding, or partial echo technology.

[0150] This embodiment also provides a multi-core imaging sequence determination device, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. The terms "module," "unit," "subunit," etc., used below can refer to combinations of software and / or hardware that implement a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0151] Figure 6 This is a structural block diagram of the multi-core imaging sequence determination device in an embodiment of the present invention, such as... Figure 6 As shown, the device includes:

[0152] The sequence acquisition module 610 is used to acquire an initial multinucleus imaging sequence, which includes the pulse arrangement of several nuclides in a single repetition time.

[0153] The sequence optimization module 620 is used to adjust the pulse arrangement of at least one nuclide to optimize the initial multinucleus imaging sequence and obtain the target multinucleus imaging sequence.

[0154] The above modules can be used to obtain a target multi-nucleus imaging sequence, which is a multi-nucleus imaging sequence obtained by combining and optimizing multiple single-nucleus imaging sequences. Therefore, this multi-nucleus imaging sequence can complete the scanning imaging of multiple nuclides in a single scanning process, which shortens the scanning time and improves the imaging efficiency compared to imaging each nuclide separately. This solves the problem that there is no method for determining imaging sequences for multi-nucleus magnetic resonance imaging technology in related technologies.

[0155] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0156] The present invention also provides an electronic device including a memory and a processor, the memory storing a computer program and the processor being configured to run the computer program to perform the steps in any of the above method embodiments.

[0157] Optionally, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0158] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated in this embodiment.

[0159] Furthermore, in conjunction with the multi-core imaging sequence determination method provided in the above embodiments, this embodiment can also provide a storage medium for implementation. The storage medium stores a computer program; when executed by a processor, the computer program implements any of the multi-core imaging sequence determination methods in the above embodiments.

[0160] The present invention also provides a magnetic resonance system, the magnetic resonance system including a control device configured to control the magnetic resonance system to perform scanning operations based on a pre-given multinucleus imaging sequence, the multinucleus imaging sequence being determined by the multinucleus imaging sequence determination method provided in the present invention.

[0161] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0162] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0163] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0164] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method for determining a multi-nucleus imaging sequence, characterized in that, The method includes: An initial multinucleus imaging sequence is obtained, wherein the initial multinucleus imaging sequence includes pulse arrangements of several nuclides within a single repetition time. The pulse arrangement of at least one of the nuclides is adjusted to optimize the initial multinucleus imaging sequence to obtain a target multinucleus imaging sequence; wherein, the plurality of nuclides include a first nuclide and a second nuclide; within a single repetition time of the initial multinucleus imaging sequence, the excitation pulse of the first nuclide is arranged before the excitation pulse of the second nuclide, and the acquisition time of the first nuclide is arranged between the excitation pulse of the second nuclide and the acquisition time. The adjustment of the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes: The dephase shift of the readout gradient of the first nuclide is moved forward to before the excitation pulse of the second nuclide; The convergence phase of the readout gradient of the first nuclide is used as the de-phase of the readout gradient of the second nuclide, and the polarity of the convergence phase of the readout gradient of the second nuclide is reversed.

2. The method for determining multi-nuclear imaging sequences according to claim 1, characterized in that, The adjustment of the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence further includes: The polarity of the layer selection gradient of the second nuclide is reversed and used as the compensation gradient of the layer selection gradient of the first nuclide.

3. The method for determining multi-nuclear imaging sequences according to claim 1, characterized in that, The adjustment of the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence further includes: A first phase encoding gradient is set between the excitation pulse of the first nuclide and the excitation pulse of the second nuclide; A second phase encoding gradient is set between the excitation pulse of the second nuclide and the readout gradient of the first nuclide; Wherein, the second phase encoding gradient constitutes the phase encoding gradient of the second nuclide, and the first phase encoding gradient and the second phase encoding gradient together constitute the phase encoding gradient of the first nuclide.

4. The method for determining multi-nucleus imaging sequences according to claim 1, characterized in that, The method further includes: The number of acquisition codes for each nuclide is determined, wherein the number of acquisition codes is the number of codes for performing one complete Fourier acquisition of the nuclide, and the number of codes is either the number of phase codes or the number of layer codes. The number of repetitions of the target multinucleus imaging sequence is determined based on the number of acquisition codes for several types of nuclides. For each nuclide, the acquisition method of the nuclide is determined based on the relationship between the number of acquisition codes of the nuclide and the number of repetitions of the target multinucleus imaging sequence.

5. The method for determining multi-nucleus imaging sequences according to claim 4, characterized in that, The step of determining the number of repetitions of the target multi-nucleus imaging sequence based on the number of acquisition codes for several types of nuclides includes: The number of repetitions of the target multi-nucleus imaging sequence is determined to be a common multiple of the number of acquisition codes for several nuclides; Alternatively, when the number of acquisition codes for several nuclides is not proportional to each other, the number of repetitions of the target multinucleus imaging sequence is determined to be a multiple of the number of acquisition codes for at least one of the nuclides.

6. The method for determining multi-nuclear imaging sequences according to claim 4, characterized in that, The step of determining the acquisition method of the nuclide based on the relationship between the number of acquisition codes of the nuclide and the number of repetitions of the target multi-nucleus imaging sequence includes: When the number of nuclide acquisition codes is proportional to the number of repetitions of the target multinucleus imaging sequence, the nuclide undergoes full Fourier acquisition. When the number of nuclide acquisition codes is not proportional to the number of repetitions of the target multinucleus imaging sequence, the nuclide performs full Fourier acquisition and partial Fourier acquisition, or performs partial Fourier acquisition.

7. A multi-nucleus imaging sequence determination device, characterized in that, The device includes: The sequence acquisition module is used to acquire an initial multinucleus imaging sequence, wherein the initial multinucleus imaging sequence includes pulse arrangements of several nuclides within a single repetition time. A sequence optimization module is used to adjust the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence, thereby obtaining a target multinucleus imaging sequence; The plurality of nuclides include a first nuclide and a second nuclide; within a single repetition time of the initial multinucleus imaging sequence, the excitation pulse of the first nuclide is arranged before the excitation pulse of the second nuclide, and the acquisition time of the first nuclide is arranged between the excitation pulse of the second nuclide and the acquisition time. The adjustment of the pulse arrangement of at least one of the nuclides to optimize the initial multinucleus imaging sequence includes: The dephase shift of the readout gradient of the first nuclide is moved forward to before the excitation pulse of the second nuclide; The convergence phase of the readout gradient of the first nuclide is used as the de-phase of the readout gradient of the second nuclide, and the polarity of the convergence phase of the readout gradient of the second nuclide is reversed.

8. A magnetic resonance imaging (MRI) system, the MRI system comprising a control device configured to control the MRI system to perform scanning operations based on a pre-given multinucleus imaging sequence, characterized in that, The multinucleus imaging sequence is determined by the multinucleus imaging sequence determination method according to any one of claims 1 to 6.

Images