Optimization methods, devices, and magnetic resonance imaging systems for multinuclear magnetic resonance imaging sequences.

Abstract

This application relates to a method, apparatus, and magnetic resonance imaging system for optimizing multinucleus imaging sequences. The optimization method includes: acquiring the multinucleus imaging sequence to be optimized and determining a target coding axis and non-target coding axes; on the target coding axis, for each nuclide, determining the secondary coding scheme of the nuclide's basic coding sequence, and determining candidate coding sequences for the nuclide based on the basic coding sequence and secondary coding scheme; determining the maximum gradient duration sum for a single scan based on the candidate coding sequences of each nuclide on the target coding axis and the fixed coding sequences of each nuclide on the non-target coding axes; and optimizing the candidate coding sequences of each nuclide on the target coding axis with minimizing the maximum gradient duration sum as the optimization objective to obtain the target coding sequence. This application solves the problems of low signal-to-noise ratio and slow multinucleus imaging speed associated with existing multinucleus imaging sequences.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance scanning, and in particular to a method, apparatus and system for optimizing magnetic resonance 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. Multi-nuclide imaging can provide information on metabolism and distribution within the body, and has become a major research focus in recent years.

[0003] Due to 1 H and 19 Nuclides outside of F have relatively low magnetic gyroscopes, while 19 The natural abundance of F is much lower than 1 H, with the same field strength, has a lower signal-to-noise ratio, therefore except 1 Imaging of nuclides outside the H region typically requires averaging multiple acquisitions and using lower resolutions to improve the signal-to-noise ratio. Since most of the time in magnetic resonance imaging is spent waiting for T1 relaxation recovery, multi-nucleus imaging can combine the imaging of multiple nuclides within the same timeframe, thus saving sampling time.

[0004] To image multiple nuclides simultaneously in multi-nucleus imaging, a corresponding multi-nucleus imaging sequence needs to be designed. Current techniques typically involve directly combining multiple single-nucleus imaging sequences to obtain a multi-nucleus imaging sequence without further optimization. Therefore, existing multi-nucleus imaging sequences have a low signal-to-noise ratio and result in slow imaging speeds.

[0005] There is currently no effective solution to the problem that existing multi-nucleus imaging sequences have low signal-to-noise ratios, which also leads to slow multi-nucleus imaging speeds. Summary of the Invention

[0006] This invention provides an optimization method, apparatus, and system for magnetic resonance imaging (MRI) multinucleus imaging sequences to address the problems of low signal-to-noise ratio and slow imaging speed in existing multinucleus imaging sequences.

[0007] In a first aspect, the present invention provides a method for optimizing a magnetic resonance multinuclear imaging sequence, the optimization method comprising:

[0008] A multinucleus imaging sequence to be optimized is obtained, and the target coding axis and non-target coding axis are determined. The multinucleus imaging sequence includes coding sequences of at least two nuclides.

[0009] On the target coding axis, for each nuclide, the secondary coding scheme of the basic coding sequence of the nuclide is determined, and the candidate coding sequence of the nuclide is determined according to the basic coding sequence and the secondary coding scheme of the nuclide;

[0010] The maximum gradient duration for a single scan is determined based on the candidate coding sequence for each nuclide on the target coding axis and the fixed coding sequence for each nuclide on the non-target coding axis.

[0011] On the target coding axis, with the goal of minimizing the maximum gradient duration, the candidate coding sequence for each nuclide is optimized to obtain the target coding sequence.

[0012] In some embodiments, the secondary encoding method includes performing encoding actions in a preset order, the encoding actions including repetition, reversal, and pause.

[0013] In some embodiments, the candidate coding sequence includes a candidate coding phase sequence;

[0014] The step of determining the candidate coding sequence of the nuclide based on its basic coding sequence and secondary coding scheme includes:

[0015] The basic coding phase sequence of the nuclide is determined based on its basic coding sequence.

[0016] The basic coding phase sequence of the nuclide is encoded by the secondary coding method of the nuclide to obtain the candidate coding phase sequence of the nuclide.

[0017] In some embodiments, the fixed coding sequence includes a fixed gradient duration sequence;

[0018] Determining the maximum gradient duration for a single scan based on the candidate coding sequence for each nuclide on the target coding axis and the fixed coding sequence for each nuclide on the non-target coding axis includes:

[0019] On the target coding axis, a gradient first moment sequence is determined based on the candidate coding phase sequence for each nuclide, and a candidate gradient duration sequence is determined based on the gradient first moment sequence.

[0020] On the non-target coding axis, a fixed gradient duration sequence is determined based on the fixed coding sequence of each nuclide;

[0021] The gradient duration for each scan is determined based on the candidate gradient duration sequence and the fixed gradient duration sequence.

[0022] The maximum gradient duration is determined based on several gradient durations.

[0023] In some embodiments, the secondary encoding method is characterized by a secondary encoding sequence, in which different elements represent different encoding actions.

[0024] In some embodiments, optimizing the candidate coding sequence for each of the nuclides with the goal of minimizing the sum of the maximum gradient durations to obtain the target coding sequence includes:

[0025] The secondary encoding scheme corresponding to the minimum value of the sum of the maximum gradient durations for each nuclide is determined as the target secondary encoding scheme;

[0026] The target coding sequence is determined based on the basic coding sequence of each nuclide and its target secondary coding scheme.

[0027] In some embodiments, the basic coding sequence is the K-space coding sequence required to perform one image acquisition;

[0028] Each encoding action in the secondary encoding method corresponds to a different image acquisition.

[0029] When the encoding action is paused, the corresponding image acquisition does not participate in the averaging of K-space data.

[0030] Secondly, this invention provides an optimization device for magnetic resonance multinuclear imaging sequences, the optimization device comprising:

[0031] An initial sequence acquisition module is used to acquire a multinucleus imaging sequence to be optimized and to determine the target coding axis and non-target coding axis. The multinucleus imaging sequence includes coding sequences of at least two nuclides.

[0032] A candidate sequence determination module is used to determine, on the target coding axis, for each nuclide, the secondary coding scheme of the basic coding sequence of the nuclide, and to determine the candidate coding sequence of the nuclide based on the basic coding sequence and the secondary coding scheme of the nuclide;

[0033] The duration determination module is used to determine the maximum gradient duration of a single scan based on the candidate coding sequence of each nuclide on the target coding axis and the fixed coding sequence of each nuclide on the non-target coding axis;

[0034] The coding sequence optimization module is used to optimize the candidate coding sequence of each nuclide on the target coding axis with the goal of minimizing the maximum gradient duration, so as to obtain the target coding sequence.

[0035] 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 method for optimizing magnetic resonance multinuclear imaging sequences as described in the first aspect.

[0036] Fourthly, the present invention provides a magnetic resonance imaging system, the imaging system including the magnetic resonance multinucleus imaging sequence optimization device described in the second aspect.

[0037] Fifthly, the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method for optimizing the magnetic resonance multinuclear imaging sequence described in the first aspect above.

[0038] Compared with related technologies, the optimization method, apparatus, and magnetic resonance imaging system for multinuclear imaging sequences provided in this invention optimize the coding sequence of the multinuclear imaging sequence on the target coding axis to minimize the maximum gradient duration of the multinuclear imaging sequence in a single scan, thereby improving the signal-to-noise ratio and imaging speed of the multinuclear imaging sequence. Therefore, this method solves the problem of low signal-to-noise ratio and slow imaging speed inherent in existing multinuclear imaging sequences.

[0039] 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

[0040] 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:

[0041] Figure 1 This is a hardware structure block diagram of the terminal that executes the optimization method of the magnetic resonance multinucleus imaging sequence in this invention;

[0042] Figure 2 This is a flowchart of the optimization method for magnetic resonance multinucleus imaging sequences provided by the present invention;

[0043] Figure 3 This is a schematic diagram of a multi-nucleus imaging sequence to be optimized in a specific embodiment of the present invention;

[0044] Figure 4This is a structural block diagram of the optimized device for magnetic resonance multinucleus imaging sequence provided by the present invention. Detailed Implementation

[0045] 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.

[0046] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as 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 such processes, methods, products, or devices. The terms “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. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0047] The method embodiments provided in this invention can be executed on a terminal, computer, or similar computing device. For example, running on a terminal. Figure 1 This is a hardware structure block diagram of the terminal that executes the optimized method for magnetic resonance multinuclear imaging sequences in this invention. For example... Figure 1 As shown, a terminal may include one or more ( Figure 1 Only 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.

[0048] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the optimization method of magnetic resonance multinuclear imaging sequences 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.

[0049] 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.

[0050] This invention provides a method for optimizing magnetic resonance multinuclear imaging sequences. Figure 2 This is a flowchart of the optimization method for magnetic resonance multinuclear imaging sequences provided by the present invention, as shown below. Figure 2 As shown, the process includes the following steps:

[0051] Step S210: Obtain the multinucleus imaging sequence to be optimized and determine the target coding axis and non-target coding axis. The multinucleus imaging sequence includes coding sequences of at least two nuclides.

[0052] In this step, the multinucleus imaging sequence to be optimized can be an existing multinucleus imaging sequence that requires further optimization, or it can be a multinucleus imaging sequence obtained by directly combining at least two single-nucleus imaging sequences after acquiring single-nucleus imaging sequences of at least two nuclides. Imaging sequences typically include multiple coding axes, such as a slice coding axis, a phase coding axis, and a readout coding axis. The optimization method in this invention typically optimizes only one coding axis in a single optimization operation. Therefore, it is also necessary to determine the target coding axis and non-target coding axes. The target coding axis is the coding axis that needs to be optimized, while the non-target coding axes are the coding axes in the imaging sequence other than the target coding axis, i.e., the coding axes that are not optimized.

[0053] It should be noted that for optimization of multiple coding axes, the optimization method in this invention can be executed separately to optimize different coding axes.

[0054] Step S220: On the target coding axis, for each nuclide, determine the secondary coding method of the basic coding sequence of the nuclide, and determine the candidate coding sequence of the nuclide based on the basic coding sequence and the secondary coding method.

[0055] This step primarily optimizes the coding sequence for each nuclide along the target coding axis. It's important to note that during the complete scan, at least one image acquisition is performed for each nuclide. Therefore, the complete imaging sequence for each nuclide consists of at least one K-space coding sequence required for one image acquisition. Thus, the K-space coding sequence required for one image acquisition can be called the basic coding sequence, which is the sequence unit constituting the complete coding sequence. For example, the basic coding sequence can be a sequential Cartesian coding sequence, a spoke coding sequence, a (pseudo)random coding sequence, or a plane wave coding sequence. The secondary coding method involves further coding the basic coding sequence. Therefore, the secondary coding method includes performing coding actions in a preset order. For a given nuclide, after secondary coding of the basic coding sequence, a candidate coding sequence for that nuclide can be obtained. The candidate coding sequence is the complete coding sequence for that nuclide, which includes at least one secondary-coded basic coding sequence.

[0056] In one embodiment, the encoding actions include repetition, inversion, and pause. Repetition refers to repeatedly executing the initial basic encoding sequence. For example, if the first and third encoding actions in a secondary encoding method are repeated, the first and third image acquisitions of the corresponding nuclide directly use the initial basic encoding sequence. Inversion refers to executing the inverted basic encoding sequence. For example, if the second and fourth encoding actions in a secondary encoding method are inverted, the second and fourth image acquisitions of the corresponding nuclide use the inverted basic encoding sequence. Pause refers to pausing the execution of the basic encoding sequence. It should be noted that the basic encoding sequence is the encoding sequence required for one image acquisition, and one image acquisition includes multiple scans. Typically, a single encoding action corresponds to a single scan. However, considering that the basic encoding sequence needs to be completely repeated or completely inverted during secondary encoding, that is, the multiple encoding actions corresponding to multiple scans in one image acquisition are the same, all being repetition or inversion, a simplification can be made by corresponding repetition and inversion actions to different image acquisitions, and pause actions to different scans. For example, assuming an image acquisition requires 20 scans, if the secondary encoding method is repeat, pause, pause, and inversion, the encoding gradient for the first image acquisition (the first 20 scans) is determined based on the base encoding sequence, without setting the encoding gradient for scans 21-22 (either not set or arbitrarily set). The encoding gradient for the second image acquisition (scans 23-42) is determined based on the inverted base encoding sequence. Correspondingly, the pause action, besides not setting any encoding gradient in the corresponding scan, can also set any encoding gradient in the corresponding scan; however, the data obtained in that scan is not involved in the averaging of the K-space data.

[0057] Step S230: Determine the maximum gradient duration for a single scan based on the candidate coding sequence of each nuclide on the target coding axis and the fixed coding sequence of each nuclide on the non-target coding axis.

[0058] In this step, since non-target coding axes are not optimized, the coding sequences on these axes remain fixed during the current optimization process. The gradient duration sum for a single scan refers to the time period during which coding gradients exist within a single scan. The maximum gradient duration sum refers to the largest gradient duration sum across all scans. It should be noted that in a single scan, due to the existence of multiple coding axes, coding gradients on different axes can overlap in time, meaning that more than two coding gradients can exist simultaneously. Therefore, the gradient duration sum is not simply the sum of the durations of all coding gradients in a single scan. When two coding gradients have overlapping duration segments, the overlapping duration segment should be recorded once, not twice. For example, assuming a first coding gradient exists in the candidate coding sequence and a second coding gradient exists in the fixed coding sequence, when the duration of the first coding gradient falls within the duration of the second coding gradient, only the duration of the second coding gradient is recorded when calculating the gradient duration sum.

[0059] Step S240: On the target coding axis, with the goal of minimizing the maximum gradient duration, optimize the candidate coding sequence for each nuclide to obtain the target coding sequence.

[0060] Through the preceding steps, given a determined candidate coding sequence, the maximum gradient duration sum corresponding to that candidate coding sequence can be calculated. When different nuclides use different candidate coding sequences, the maximum gradient duration sum per scan may differ. The optimization objective in this step is to reduce the maximum gradient duration sum per scan, thereby determining the candidate coding sequence that minimizes the maximum gradient duration sum. The candidate coding sequences that meet the requirements for each nuclide constitute the target coding sequence. The target coding sequence is the coding sequence of the optimized multi-nucleus imaging sequence on the target coding axis. Furthermore, since the candidate coding sequence is obtained by applying a secondary coding method to the basic coding sequence, this step is essentially also about determining the secondary coding sequence that minimizes the maximum gradient duration sum.

[0061] Furthermore, in one embodiment, step S240 specifically includes:

[0062] Step S241: Determine the target secondary coding scheme as the secondary coding scheme corresponding to the minimum value of the sum of maximum gradient durations for each nuclide; Step S242: Determine the target coding sequence based on the basic coding sequence of each nuclide and its target secondary coding scheme.

[0063] It should be further explained that there are two ways to determine the specific method of target secondary encoding.

[0064] In one embodiment, for some relatively simple optimization cases, the secondary coding scheme of the basic coding sequence of each nuclide can be determined, and the maximum gradient duration corresponding to each secondary coding scheme can be calculated. Finally, the secondary coding scheme corresponding to the minimum maximum gradient duration is determined as the target secondary coding scheme.

[0065] In another embodiment, for some more complex optimization situations, optimization can be performed using existing optimization algorithms. For example, a genetic algorithm can be used. Since the calculation relationship between the secondary encoding method and the maximum gradient duration sum is determined, inputting this calculation relationship into the optimization algorithm allows the algorithm to determine the minimum value of the maximum gradient duration sum and the corresponding secondary encoding method.

[0066] Through the above steps, the coding sequence of the multi-nucleus imaging sequence on the target coding axis can be optimized to minimize the maximum gradient duration in a single scan, thereby improving the signal-to-noise ratio and imaging speed of the multi-nucleus imaging sequence. Therefore, this invention provides an optimization method for magnetic resonance multi-nucleus imaging sequences. Using this optimization method to optimize multi-nucleus imaging sequences can improve the signal-to-noise ratio and imaging speed of the multi-nucleus imaging sequence, solving the problem that existing multi-nucleus imaging sequences have low signal-to-noise ratios and slow imaging speeds.

[0067] In some embodiments, the candidate coding sequence includes a candidate coding phase sequence; in step S220, determining the candidate coding sequence of the nuclide based on the nuclide's basic coding sequence and secondary coding method includes:

[0068] Step S221: Determine the basic coding phase sequence of the nuclide based on its basic coding sequence; Step S222: Encode the basic coding phase sequence of the nuclide using the secondary coding method of the nuclide to obtain the candidate coding phase sequence of the nuclide.

[0069] Specifically, the coding sequence is a combination of various coding gradients, and the coding gradient has characteristics such as coding phase, duration, and first moment. This embodiment provides a specific method for determining candidate coding sequences. First, the basic coding phase sequence of the nuclide is determined, which contains each coding phase in the basic coding sequence. Then, a secondary coding method is applied to the basic coding phase sequence to obtain a candidate coding phase sequence, which represents the coding phase of each coding gradient in the candidate coding sequence. For example, when the basic coding phase sequence is π / 2, 0, -π / 2, and the secondary coding method is repeat, repeat, and inversion, the candidate coding phase sequence is: π / 2, 0, -π / 2, π / 2, 0, -π / 2, -π / 2, 0, π / 2.

[0070] Furthermore, in some embodiments, the fixed encoding sequence includes a fixed gradient duration sequence; step S230 specifically includes:

[0071] Step S231: On the target coding axis, determine the gradient first moment sequence based on the candidate coding phase sequence for each nuclide, and determine the candidate gradient duration sequence based on the gradient first moment sequence; Step S232: On the non-target coding axis, determine the fixed gradient duration sequence based on the fixed coding sequence for each nuclide; Step S233: Determine the gradient duration sum for each scan based on the candidate gradient duration sequence and the fixed gradient duration sequence; Step S234: Determine the maximum gradient duration sum based on several gradient duration sums.

[0072] This embodiment, based on the previous embodiment, provides a specific method for determining the maximum gradient duration sum. First, on the target coding axis, the coding phase of the corresponding coding gradient can be determined based on the candidate coding phase sequence for each nuclide. Then, the first moment of each nuclide is determined based on its coding phase, thus obtaining the first moments of each coding gradient on the target coding axis. Combining the first moments of each coding gradient in sequence yields the gradient first moment sequence, which includes the first moments of all coding gradients on the target coding axis. The duration of each coding gradient can then be determined using its first moment, thus further obtaining the candidate gradient duration sequence. Simultaneously, the coding sequences on non-target coding axes are known and fixed, meaning the duration of each gradient in the coding sequence is known and fixed, allowing the acquisition of a fixed gradient duration sequence for a fixed coding sequence. Finally, the gradient duration sum for each scan is determined based on the candidate gradient duration sequence and the fixed gradient duration sequence. Based on the gradient duration sequence, the duration of each coding gradient in a single scan can be determined, and thus the gradient duration sum for each scan can be calculated.

[0073] The specific calculation method for the gradient duration sum has been described in the previous embodiments and will not be repeated in this embodiment. Crucially, the gradient duration sum is not simply the sum of the durations of all encoded gradients in a single scan. When two encoded gradients have overlapping duration segments, the overlapping duration segment should be recorded once, not twice.

[0074] Specifically, the formula for calculating the first moment of the gradient of a nuclide based on its coding phase is as follows:

[0075]

[0076] For any nuclide, its gradient first moment can be calculated using the above formula. Here, M is the first moment of the nuclide, P is the encoding phase of the nuclide, γ is the gyromagnetic ratio of the nuclide, and F is the field-of-view size of the nuclide in the encoding direction.

[0077] It should be noted that the specific method for calculating the first moment of each coding gradient on the target coding axis based on the first moment of each nuclide's gradient needs to be adaptively modified according to the combination of each nuclide, based on the formula above. This is because, in most cases, the coding gradients on the target coding axis do not have a one-to-one correspondence with each nuclide. For example, in a multi-nuclide combination, assuming there is a first nuclide and a second nuclide, the excitation of the first nuclide precedes the excitation of the second nuclide, and the acquisition of the first nuclide follows the acquisition of the second nuclide. On the target coding axis, there exist a first coding gradient and a second coding gradient, with the first coding gradient occurring between the excitation of the first nuclide and the excitation of the second nuclide, and the second coding gradient occurring between the excitation of the second nuclide and the acquisition of the second nuclide. At this point, only the second coding gradient has an encoding effect on the second nuclide, thus constituting the coding gradient of the second nuclide. Therefore, the first moment of the gradient of the second nuclide is the first moment of the second coding gradient. Both the first and second coding gradients have an encoding effect on the first nuclide, thus together they constitute the coding gradient of the first nuclide. Therefore, the difference between the first moment of the gradient of the first nuclide and the first moment of the gradient of the second nuclide is the first moment of the first coding gradient. Crucially, it is necessary to determine the interaction relationship between each coding gradient and various nuclides based on the setting position of each coding gradient. Correspondingly, if there is a one-to-one correspondence between each coding gradient on each target coding axis and each nuclide, then the first moment of each coding gradient is the first moment of the gradient of its corresponding nuclide.

[0078] The specific method for calculating the duration based on the first moment of the encoded gradient is as follows:

[0079] The maximum gradient strength of the encoding gradient to be calculated is G, and the ramp rate is S;

[0080] When the first moment When the gradient waveform with the shortest duration is a triangular wave, the shortest duration is...

[0081] When the first moment When the gradient waveform with the shortest duration is a trapezoidal wave, the shortest duration is

[0082] In some embodiments, the secondary encoding method is characterized by a secondary encoding sequence, where different elements in the secondary encoding sequence represent different encoding actions.

[0083] Specifically, different numerical elements can be used to represent different encoding actions, and thus a secondary encoding method can be characterized through a number table. For example, the number 1 can be used to represent repetition, the number 0 to represent pause, and the number -1 to represent reversal. By using the above-mentioned secondary encoding method with a number table, it is easier for the computer to recognize the encoding and then execute the optimized method.

[0084] The technical solution of the present invention will be described in more detail below through a specific embodiment.

[0085] In one specific embodiment, the optimization method includes:

[0086] Step S310: Obtain the multinucleus imaging sequence to be optimized and determine the target coding axis and non-target coding axis. The multinucleus imaging sequence includes coding sequences of at least two nuclides.

[0087] Step S320: On the target coding axis, determine the basic coding phase sequence of the nuclide based on the basic coding sequence of the nuclide;

[0088] Step S330: On the target coding axis, the basic coding phase sequence of the nuclide is encoded by the secondary coding sequence of the nuclide to obtain the candidate coding phase sequence of the nuclide;

[0089] Step S340: On the target coding axis, determine the gradient first moment sequence based on the candidate coding phase sequence for each nuclide, and determine the candidate gradient duration sequence based on the gradient first moment sequence;

[0090] Step S350: On the non-target coding axis, determine the fixed gradient duration sequence based on the fixed coding sequence of each nuclide;

[0091] Step S360: Determine the gradient duration for each scan based on the candidate gradient duration sequence and the fixed gradient duration sequence;

[0092] Step S370: Determine the maximum gradient duration based on several gradient durations;

[0093] Step S380: On the target coding axis, with the goal of minimizing the maximum gradient duration, optimize the secondary coding sequence of each nuclide to obtain the target coding sequence.

[0094] Specifically, given the basic coding order (basic coding sequence) of each nuclide, it is repeated, reversed, and paused to obtain the secondary coding sequence; the candidate coding phase sequence is calculated using the basic coding order and the secondary coding sequence; the coding gradient first moment sequence is calculated based on the candidate coding phase sequence of each nuclide; the candidate gradient duration sequence is determined based on the gradient first moment sequence and gradient system performance parameters; the maximum gradient duration is determined based on the duration sequence of the remaining gradient axes between radio frequency pulses (fixed gradient duration sequence) and the aforementioned candidate gradient duration sequence; the secondary coding sequence is optimized with minimizing the maximum gradient duration as the optimization objective; and the setting of the coding gradient first moment is determined based on the optimization results throughout the acquisition process.

[0095] The basic coding order refers to the K-space coding order required to complete one image acquisition, including existing methods such as sequential Cartesian coding, spoke coding, (pseudo)random coding, and plane wave coding, without restriction. In the basic coding order, the first moment of the coding gradient can always be 0. Pause means that any gradient first moment can be coded for this nuclide in this acquisition, and the resulting data is not directly used for averaging. The values ​​in the secondary coding sequence indicate whether the nuclide was coded according to the basic coding order, the reverse of the basic coding order, or whether the acquisition was not directly used for averaging. The longest gradient duration is the sum of the longest durations of the gradient waveforms set between the last radio frequency pulse and the first acquisition. Optimizing the coding order refers to changing the secondary coding sequence of each nuclide to minimize the longest gradient duration.

[0096] For example, if a certain secondary coding sequence is 1, 0, 1, -1, and the phase sequence corresponding to its basic coding order is π / 2, 0, -π / 2, then the candidate coding phase sequence is π / 2, 0, -π / 2, any, any, any, π / 2, 0, -π / 2, -π / 2, 0, π / 2.

[0097] Figure 3 This is a schematic diagram of a multi-nucleus imaging sequence to be optimized in a specific embodiment of the present invention. (Refer to...) Figure 3 The specific optimization process is explained below.

[0098] The subscript X is used to distinguish nuclides. If the encoding phase sequence is P, then the encoding phase that nuclide X should undergo in the nth scan is P. X (n). Let F be the field-of-view scale of the nuclide in the encoding direction and γ be the gyromagnetic ratio. Then, in the nth scan, Figure 3 The first moments M of the three coding gradients numbered 1, 2, and 3 are as follows:

[0099]

[0100]

[0101]

[0102] A negative first moment indicates that the coding gradient has the opposite polarity to the specification.

[0103] Calculating duration based on the first moment is existing technology, as explained below:

[0104] Let G be the maximum gradient strength of the encoding gradient to be calculated and S be the climbing rate;

[0105] When the first moment When the gradient waveform with the shortest duration is a triangular wave, the shortest duration is...

[0106] When the first moment When the gradient waveform with the shortest duration is a trapezoidal wave, the shortest duration is

[0107] For example, suppose Figure 3 The first moments of coding gradients 1-7 are 4.5, 8, 6.4, 7.1, 5.4, 2.1, and 6.5 (unit: μT*s / m). Coding gradients 1 and 4 coexist, with a maximum first moment of 7.1 (corresponding to coding gradient 4); coding gradients 2 and 6 coexist, with a maximum first moment of 8 (corresponding to coding gradient 2); and coding gradients 3, 5, and 7 coexist, with a maximum first moment of 6.5 (corresponding to coding gradient 7). The durations of coding gradients 4, 2, and 7 are calculated separately and then summed to obtain the gradient duration sum for that scan. The longest gradient duration sum is selected as the maximum gradient duration sum across all scans. After adjusting the secondary coding sequence, the first moment sequence of coding gradients 1-7 may become: 5.6, 9.4, 8.1, 7.1, 5.4, 2.1, and 6.5. It can be seen that the first moments of the coding gradients 1-3 (on the target coding axis) have changed, while the first moments of the coding gradients 4-6 (on the non-target coding axis) have not changed.

[0108] Finally, it should be noted that when the coding phase of a certain nuclide is "arbitrary" in a certain scan, in a better processing method, the actual coding phase adopted and the first moment of each coding gradient in the scan are determined with the goal of minimizing the gradient duration in that scan.

[0109] The optimization objective is to obtain the minimum possible maximum gradient duration. When the resolution difference between nuclides is not large, the number of repeated samplings of nuclides is relatively small, and the possibility of secondary coding sequences is relatively small. The optimal secondary coding sequence can be obtained by exhaustive search.

[0110] It should be noted that the optimization method for magnetic resonance multinucleus imaging sequences provided in this invention can be applied to both two-dimensional and three-dimensional magnetic resonance imaging. It is important to note that in one type of multinucleus imaging sequence, some nuclides are used for three-dimensional imaging while others are used for two-dimensional imaging. In this case, the slice phase encoding axis in three-dimensional imaging is the slice selection gradient axis in two-dimensional imaging; therefore, this gradient axis is not entirely an encoding axis, and thus the optimization method of this invention is not applicable. However, the optimization method of this invention is applicable to other encoding axes shared by multiple nuclides.

[0111] This invention also provides an optimization device for magnetic resonance multinuclear imaging sequences, which is used to implement the above embodiments and preferred embodiments, and will not be repeated as described previously. The terms "module," "unit," "subunit," etc., used below can refer to a combination of software and / or hardware that performs 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.

[0112] Figure 4 This is a structural block diagram of the optimized device for magnetic resonance multinucleus imaging sequences provided by the present invention, as shown below. Figure 4 As shown, the device includes:

[0113] The initial sequence acquisition module 510 is used to acquire the multinucleus imaging sequence to be optimized and to determine the target coding axis and non-target coding axis. The multinucleus imaging sequence includes coding sequences of at least two nuclides.

[0114] The candidate sequence determination module 520 is used to determine the secondary coding scheme of the basic coding sequence of a nuclide for each nuclide on the target coding axis, and to determine the candidate coding sequence of the nuclide based on the basic coding sequence and the secondary coding scheme of the nuclide.

[0115] The duration determination module 530 is used to determine the maximum gradient duration of a single scan based on the candidate coding sequence of each nuclide on the target coding axis and the fixed coding sequence of each nuclide on the non-target coding axis.

[0116] The coding sequence optimization module 540 is used to optimize the candidate coding sequence of each nuclide on the target coding axis with the goal of minimizing the maximum gradient duration, so as to obtain the target coding sequence.

[0117] The aforementioned modules can optimize the coding sequence of multi-kernel imaging sequences along the target coding axis to minimize the maximum gradient duration in a single scan, thereby improving the signal-to-noise ratio and imaging speed of the multi-kernel imaging sequence. This solves the problem of low signal-to-noise ratio and slow imaging speed in existing multi-kernel imaging sequences.

[0118] 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.

[0119] Furthermore, in conjunction with the aforementioned optimization device for magnetic resonance multinuclear imaging sequences, the present invention also provides a magnetic resonance imaging system, which includes the optimization device for magnetic resonance multinuclear imaging sequences provided in the present invention.

[0120] 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.

[0121] 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.

[0122] Furthermore, in conjunction with the optimization method for magnetic resonance multinuclear imaging sequences provided in the above embodiments, this invention can also provide a storage medium for implementation. This storage medium stores a computer program; when executed by a processor, the computer program implements any of the optimization methods for magnetic resonance multinuclear imaging sequences in the above embodiments.

[0123] Accordingly, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0124] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] The embodiments described above are merely illustrative of 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 optimizing a magnetic resonance multinuclear imaging sequence, characterized in that, The optimization method includes: A multinucleus imaging sequence to be optimized is obtained, and a target coding axis and a non-target coding axis are determined. The multinucleus imaging sequence includes coding sequences of at least two nuclides. The target coding axis is the coding axis to be optimized, and the non-target coding axis is the coding axis not to be optimized. On the target coding axis, for each nuclide, a secondary coding method of the basic coding sequence of the nuclide is determined, and a candidate coding sequence of the nuclide is determined based on the basic coding sequence and the secondary coding method; the basic coding sequence is the K-space coding sequence required to perform one image acquisition; the secondary coding method is a processing method that performs secondary coding on the basic coding sequence; The maximum gradient duration for a single scan is determined based on the candidate coding sequence for each nuclide on the target coding axis and the fixed coding sequence for each nuclide on the non-target coding axis. On the target coding axis, with the goal of minimizing the maximum gradient duration, the candidate coding sequence for each nuclide is optimized to obtain the target coding sequence.

2. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 1, characterized in that, The secondary encoding method includes executing encoding actions in a preset order, and the encoding actions include repetition, reversal, and pause.

3. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 1, characterized in that, The candidate coding sequence includes a candidate coding phase sequence; The step of determining the candidate coding sequence of the nuclide based on its basic coding sequence and secondary coding scheme includes: The basic coding phase sequence of the nuclide is determined based on its basic coding sequence. The basic coding phase sequence of the nuclide is encoded by the secondary coding method of the nuclide to obtain the candidate coding phase sequence of the nuclide.

4. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 3, characterized in that, The fixed coding sequence includes a fixed gradient duration sequence; Determining the maximum gradient duration for a single scan based on the candidate coding sequence for each nuclide on the target coding axis and the fixed coding sequence for each nuclide on the non-target coding axis includes: On the target coding axis, a gradient first moment sequence is determined based on the candidate coding phase sequence for each nuclide, and a candidate gradient duration sequence is determined based on the gradient first moment sequence. On the non-target coding axis, a fixed gradient duration sequence is determined based on the fixed coding sequence of each nuclide; The gradient duration for each scan is determined based on the candidate gradient duration sequence and the fixed gradient duration sequence. The maximum gradient duration is determined based on several gradient durations.

5. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 2, characterized in that, The secondary encoding method is characterized by a secondary encoding sequence, where different elements in the secondary encoding sequence represent different encoding actions.

6. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 3, characterized in that, The optimization of the candidate coding sequence for each nuclide, with the goal of minimizing the sum of the maximum gradient durations, to obtain the target coding sequence includes: The secondary encoding scheme corresponding to the minimum value of the sum of the maximum gradient durations for each nuclide is determined as the target secondary encoding scheme; The target coding sequence is determined based on the basic coding sequence of each nuclide and its target secondary coding scheme.

7. The method for optimizing a magnetic resonance multinucleus imaging sequence according to claim 2, characterized in that, The basic coding sequence is the K-space coding sequence required to perform one image acquisition; Each encoding action in the secondary encoding method corresponds to a different image acquisition. When the encoding action is paused, the corresponding image acquisition does not participate in the averaging of K-space data.

8. An optimization device for magnetic resonance multinuclear imaging sequences, characterized in that, The optimization device includes: An initial sequence acquisition module is used to acquire a multi-nucleus imaging sequence to be optimized and to determine a target coding axis and a non-target coding axis. The multi-nucleus imaging sequence includes coding sequences of at least two nuclides. The target coding axis is the coding axis to be optimized, and the non-target coding axis is the coding axis not to be optimized. The candidate sequence determination module is used to determine, on the target coding axis, for each nuclide, the secondary coding method of the basic coding sequence of the nuclide, and to determine the candidate coding sequence of the nuclide based on the basic coding sequence and the secondary coding method of the nuclide; the basic coding sequence is the K-space coding sequence required to perform one image acquisition; the secondary coding method is a processing method that performs secondary coding on the basic coding sequence; The duration determination module is used to determine the maximum gradient duration of a single scan based on the candidate coding sequence of each nuclide on the target coding axis and the fixed coding sequence of each nuclide on the non-target coding axis; The coding sequence optimization module is used to optimize the candidate coding sequence of each nuclide on the target coding axis with the goal of minimizing the maximum gradient duration, so as to obtain the target coding sequence.

9. A magnetic resonance imaging system, characterized in that, The imaging system includes the optimization device for the magnetic resonance multinuclear imaging sequence as described in claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for optimizing the magnetic resonance multinuclear imaging sequence according to any one of claims 1 to 7.

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