Magnetic resonance pulse sequence generation method and apparatus, computer device

Abstract

The application relates to a magnetic resonance pulse sequence generation method and device and a computer device. The method comprises the following steps: acquiring a plurality of candidate radio frequency pulse information each corresponding to a candidate pulse sequence; different candidate radio frequency pulse information corresponds to different sub-radio frequency pulse numbers, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform; optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; determining target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on pulse evaluation results corresponding to each optimized candidate pulse sequence; the pulse evaluation result comprises uniformity information and pulse duration information; and obtaining a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information. The method can make the expected excitation field reach a better uniformity while being closer to the effect of a real excitation field, thereby improving the magnetic resonance parallel emission pulse efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of computer, in particular to a magnetic resonance pulse sequence generation method and device, computer equipment, storage medium and computer program product. BACKGROUND

[0002] In the process of magnetic resonance ultra-high field imaging, due to the problem of non-uniformity of the transmit field caused by multi-channel transmit radio frequency pulses, while applying parallel transmit pulses, time-varying gradients in different directions need to be applied to improve the uniformity of the transmit field.

[0003] In related technologies, the method of designing multi-channel parallel transmit pulses based on gradient waveforms is usually adopted. Due to the influence of eddy current effect, the actual gradient waveform applied is inconsistent with the designed gradient waveform, resulting in inconsistency between the expected excitation field and the actual one, and the effect of magnetic resonance parallel transmit pulses is not good. SUMMARY

[0004] Therefore, it is necessary to provide a magnetic resonance pulse sequence generation method, device, computer equipment, storage medium and computer program product to solve the above problems.

[0005] In a first aspect, the present application provides a magnetic resonance pulse sequence generation method, which comprises:

[0006] obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform;

[0007] optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information;

[0008] determining target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on the pulse evaluation results corresponding to each optimized candidate pulse sequence; the pulse evaluation results include uniformity information and pulse duration information;

[0009] obtaining a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information.

[0010] In one of the embodiments, the method for obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively comprises:

[0011] obtaining a plurality of preset candidate radio frequency pulse information and a preset waveform for sub-radio frequency pulses; the candidate radio frequency pulse information is used to represent the number of sub-radio frequency pulses applied by the radio frequency pulse channel;

[0012] According to the preset waveform, a candidate pulse sequence corresponding to each candidate radio frequency pulse information is constructed.

[0013] The candidate pulse sequence includes a plurality of sub-radio frequency pulses corresponding to a number of sub-radio frequency pulses, and each sub-radio frequency pulse has a corresponding initial waveform parameter.

[0014] In one embodiment, the optimization of the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence obtains an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information, including:

[0015] For each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result;

[0016] Based on a second optimization condition, the sub-radio frequency pulse waveform in the first optimization result is adjusted to obtain a second optimization result;

[0017] The second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information.

[0018] In one embodiment, the adjustment of the sub-radio frequency pulse waveform in the first optimization result based on the second optimization condition to obtain the second optimization result includes:

[0019] The preset waveform is updated by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result.

[0020] In one embodiment, the preset waveform includes a preset gradient waveform, and the waveform parameter includes a gradient switching rate. The updating of the preset waveform by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result includes:

[0021] For each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined. The gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet a preset condition.

[0022] The second optimization result is obtained through multiple iteration optimizations.

[0023] In one embodiment, the determination of the target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on the pulse evaluation result corresponding to each optimized candidate pulse sequence includes:

[0024] The target radio frequency pulse information is determined from the candidate radio frequency pulse information based on the pulse evaluation results corresponding to the optimization candidate pulse sequences and information applied in parallel emission of magnetic resonance.

[0025] In one of the embodiments, before the step of obtaining the target pulse sequence according to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information, the method further comprises:

[0026] In the case that the homogeneity information or the pulse length information corresponding to the optimization candidate pulse sequence does not satisfy the preset evaluation condition, the candidate radio frequency pulse information is determined again, and the step of obtaining the candidate pulse sequence corresponding to each of the candidate radio frequency pulse information is returned.

[0027] In one of the embodiments, the number of different sub-radio frequency pulses is an odd number.

[0028] In a second aspect, the application further provides a magnetic resonance pulse sequence generation device, the device comprising:

[0029] A candidate pulse sequence obtaining module is configured to obtain a candidate pulse sequence corresponding to each of candidate radio frequency pulse information; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform.

[0030] A parallel optimization module is configured to optimize the radio frequency pulse and the sub-radio frequency pulse waveform in each of the candidate pulse sequences to obtain an optimization candidate pulse sequence corresponding to each of the candidate radio frequency pulse information.

[0031] A target radio frequency pulse information determining module is configured to determine the target radio frequency pulse information from the candidate radio frequency pulse information based on the pulse evaluation results corresponding to each of the optimization candidate pulse sequences; the pulse evaluation results include homogeneity information and pulse length information.

[0032] A target pulse sequence obtaining module is configured to obtain a target pulse sequence according to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information.

[0033] In a third aspect, the application further provides a computer device. The computer device comprises a memory and a processor, the memory stores a computer program, and the processor implements the steps of the magnetic resonance pulse sequence generation method as described above when executing the computer program.

[0034] In a fourth aspect, the application further provides a computer readable storage medium. The computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the magnetic resonance pulse sequence generation method as described above.

[0035] In a fifth aspect, the present application also provides a computer program product. The computer program product comprises a computer program which, when executed by a processor, implements the steps of the magnetic resonance pulse sequence generation method as described above.

[0036] The magnetic resonance pulse sequence generation method, device, computer device, storage medium and computer program product described above, by obtaining a plurality of candidate radio frequency pulse information each corresponding to a candidate pulse sequence, different candidate radio frequency pulse information corresponding to different sub-radio frequency pulse quantities, each sub-radio frequency pulse in the candidate pulse sequence having the same preset waveform, then optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information, and then determining the target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on the pulse evaluation result corresponding to each optimized candidate pulse sequence, the pulse evaluation result including uniformity information and pulse duration information, obtaining the target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information, realizes comprehensive evaluation and consideration of the vortex effect, the excitation field uniformity and the total pulse duration in the magnetic resonance pulse sequence generation process, can continuously adjust in the optimization process based on the same preset waveform, and adopts the way of optimizing the sub-radio frequency pulse waveform and the radio frequency pulse corresponding to different sub-radio frequency pulse quantities in parallel, determines the optimal sub-radio frequency pulse quantity, can make the expected excitation field reach better uniformity while being closer to the effect of the real excitation field, and improves the magnetic resonance parallel emission pulse efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A flowchart of a magnetic resonance pulse sequence generation method in one embodiment is shown;

[0038] Figure 2 A schematic diagram of a gradient basis waveform in one embodiment is shown;

[0039] Figure 3 A schematic diagram of a magnetic resonance parallel emission gradient waveform processing flow in one embodiment is shown;

[0040] Figure 4 A flowchart of another magnetic resonance pulse sequence generation method in one embodiment is shown;

[0041] Figure 5 A block diagram of a magnetic resonance pulse sequence generation device in one embodiment is shown;

[0042] Figure 6 An internal structure diagram of a computer device in one embodiment is shown. DETAILED DESCRIPTION

[0043] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0044] In one embodiment, as shown in Figure 1 A magnetic resonance pulse sequence generation method is provided, and the present embodiment is exemplified by the method applied to a terminal. It should be understood that the method can also be applied to a server, and can also be applied to a system including a terminal and a server, and can be realized through the interaction of the terminal and the server. In the present embodiment, the method comprises the following steps:

[0045] Step 101, acquiring a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively, different candidate radio frequency pulse information corresponding to different sub-radio frequency pulse numbers;

[0046] Among them, the candidate radio frequency pulse information can be used to represent the number of sub-radio frequency pulses applied by the radio frequency pulse channel, and can be optimized by setting different total numbers of sub-radio frequency pulses, such as setting the total number of sub-radio frequency pulses to 5, 7, 9, etc. to determine the optimal number of sub-radio frequency pulses.

[0047] As an example, each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform, which can include a preset gradient waveform and can also include a triangular waveform. For example, the preset gradient waveform can be used as a basic gradient waveform, and the basic gradient waveform is used to design each sub-radio frequency pulse.

[0048] In actual application, the selected basic gradient waveform can be used as the initial waveform of the gradient waveform corresponding to each sub-radio frequency pulse, so that each sub-radio frequency pulse has the same preset waveform. By setting different numbers of sub-radio frequency pulses and according to the preset waveform corresponding to each sub-radio frequency pulse, a plurality of candidate pulse sequences under different numbers of sub-radio frequency pulses can be obtained.

[0049] In an example, as shown in Figure 2 The preset gradient waveform can correspond to waveform parameters such as gradient switching rate and gradient platform value. Through gradient basic waveform design, each sub-radio frequency pulse can have corresponding initial waveform parameters, such as initial gradient switching rate s0 and initial gradient platform value G1.

[0050] In yet another example, since in the design of the gradient waveform, if the gradient waveform under a lower gradient switching rate is adopted, the eddy current effect generated is smaller, if the gradient waveform of any gradient is adopted, the eddy current effect generated is larger, it is difficult to correct through subsequent calibration, and under the condition that the gradient waveform duration of the triangular wave is too short, a larger eddy current will also be caused; in the embodiment, in order to minimize the influence of the eddy current effect on the excitation field, the basic gradient waveform is adopted for the design of each gradient waveform (that is, each sub-radio frequency pulse has the same preset waveform), and the initial gradient switching rate is set respectively, and then the gradient waveform corresponding to each sub-radio frequency pulse can be updated by adjusting the gradient switching rate when the gradient waveform and the parallel emission pulse are jointly optimized.

[0051] For example, for multi-channel emission radio frequency pulses, the number of radio frequencies applied by each radio frequency pulse channel corresponds to the total number of gradient waveform segments, that is, the total number of sub-radio frequency pulses is the total number of gradient waveform segments, and through optimization, the optimal total number of gradient waveform segments, the waveform amplitude corresponding to each gradient waveform, and the amplitude and phase of each RF (Radio Frequency) can be determined.

[0052] In an optional embodiment, the number of different sub-radio frequency pulses is an odd number, such as 5, 7, 9, etc., since when editing a 3D excitation k-space, the k-space needs to be reset to the point of k=0, and similarly for a 2D excitation k-space, the same processing is also required, so that by setting the total number of sub-radio frequency pulses to an odd number, only one sub-pulse with the maximum amplitude exists in the pulse train, which is conducive to resetting the k-space to the point of k=0.

[0053] Step 102, optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information;

[0054] In a specific implementation, in order to determine the optimal total number of gradient waveform segments (that is, the number of sub-radio frequency pulses), the parallel optimization of the gradient waveform and the radio frequency pulse corresponding to different numbers of sub-radio frequency pulses can be adopted, the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence are optimized to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information, and further judgment is performed based on each optimized candidate pulse sequence.

[0055] In an optional embodiment, for candidate pulse sequences corresponding to different numbers of sub-radio frequency pulses, the conjugate gradient method can be used to optimize the radio frequency pulse in each candidate pulse sequence, and then the interior point method can be used to optimize the sub-radio frequency pulse waveform in each candidate pulse sequence according to the obtained optimized radio frequency pulse.

[0056] In step 103, the target radio frequency pulse information is determined from the multiple candidate radio frequency pulse information based on the pulse evaluation results corresponding to the multiple optimization candidate pulse sequences.

[0057] As an example, the pulse evaluation results can include homogeneity information and pulse length information, such as the excitation homogeneity NRMSE under different numbers of sub-radio frequency pulses and the total pulse length.

[0058] After obtaining the multiple optimization candidate pulse sequences, the excitation homogeneity corresponding to each optimization candidate pulse sequence can be calculated, and the total pulse length can be determined to obtain the pulse evaluation results corresponding to each optimization candidate pulse sequence, and then the optimal number of sub-radio frequency pulses, i.e., the target radio frequency pulse information, can be determined.

[0059] Specifically, the magnetic resonance parallel transmission application information and the pulse evaluation results corresponding to each optimization candidate pulse sequence can be combined to select, such as determining the gradient waveform and radio frequency pulse under which number of sub-radio frequency pulses to use according to the specific application.

[0060] For example, the magnetic resonance parallel transmission application information can be used to indicate the specific application, such as one of the 2D layer selection scenario, the 3D slab excitation scenario, and the hard pulse three-dimensional body excitation scenario.

[0061] In step 104, the target pulse sequence is obtained according to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information.

[0062] After determining the optimal number of sub-radio frequency pulses, i.e., obtaining the target radio frequency pulse information, the optimization candidate pulse sequence corresponding to the optimal number of sub-radio frequency pulses can be selected as the target pulse sequence to be substituted into the sequence for scanning.

[0063] Compared with the traditional method, in order to obtain a more uniform excitation field, the gradient waveform needs to be optimized. However, the process of optimizing the gradient waveform is a non-convex nonlinear optimization process, and the effect obtained by using the traditional method based on global gradient waveform optimization is not good. The technical solution of the embodiment can select the basic gradient waveform for each sub-radio frequency pulse and continuously adjust the gradient waveform during the optimization process, so that the expected excitation field can reach a good homogeneity while being closer to the real excitation field.

[0064] In the above-mentioned magnetic resonance pulse sequence generation method, candidate pulse sequences corresponding to multiple candidate radio frequency pulse information are obtained. Then, the radio frequency pulse and sub-radio frequency pulse waveforms in each candidate pulse sequence are optimized to obtain the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information. Based on the pulse evaluation results corresponding to each optimized candidate pulse sequence, the target radio frequency pulse information is determined from multiple candidate radio frequency pulse information. According to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information, the target pulse sequence is obtained. This method achieves a comprehensive evaluation considering eddy current effect, excitation field uniformity, and total pulse duration during the magnetic resonance pulse sequence generation process. It can continuously adjust the waveform based on the same preset waveform during the optimization process and adopts a parallel optimization method for sub-radio frequency pulse waveforms and radio frequency pulses corresponding to different numbers of sub-radio frequency pulses to determine the optimal number of sub-radio frequency pulses. This enables the expected excitation field to achieve better uniformity while more closely resembling the effect of the real excitation field, thus improving the efficiency of parallel transmission pulses in magnetic resonance.

[0065] In one embodiment, obtaining the candidate pulse sequence corresponding to each of the multiple candidate radio frequency pulse information may include the following steps:

[0066] Acquire multiple preset candidate radio frequency pulse information and preset waveforms for sub-radio frequency pulses; the candidate radio frequency pulse information is used to characterize the number of sub-radio frequency pulses applied by the radio frequency pulse channel; construct a candidate pulse sequence corresponding to each candidate radio frequency pulse information according to the preset waveforms.

[0067] Each candidate pulse sequence can contain a corresponding number of sub-RF pulses, and each sub-RF pulse has corresponding initial waveform parameters.

[0068] In practical applications, such as Figure 3 As shown, by designing the gradient-based waveform, a preset waveform for the sub-RF pulse can be obtained. Furthermore, by setting different numbers of sub-RF pulses, multiple preset candidate RF pulse information can be obtained. Then, for multiple different numbers of sub-RF pulses, candidate pulse sequences corresponding to each candidate RF pulse information can be constructed based on the preset waveform.

[0069] Specifically, since the gradient optimization process is a non-convex nonlinear process, the optimization process depends on the selection of the initial value of the gradient waveform. Different initial values ​​of the gradient waveform can be set during the optimization process (i.e., each sub-RF pulse has a corresponding initial waveform parameter), which can include the initial gradient switching rate s0 and the initial gradient plateau value G1. Then, the gradient waveform corresponding to each initial gradient switching rate s0 and the initial gradient plateau value G1 can be optimized separately. The maximum switching rate can also be set to s1 and the maximum gradient plateau value to Gmax.

[0070] In an optional embodiment, for the scenario of parallel emission, since there is a two-dimensional slice selection excitation scenario, the radio frequency pulse is a slice selection pulse, the z direction gradient is staggered and cannot be changed, and the gradient basis waveform from the x and y directions needs to be set as an acceptable triangular wave to be substituted into the algorithm for optimization.

[0071] In this embodiment, by obtaining a plurality of preset candidate radio frequency pulse information and a preset waveform for the sub-radio frequency pulse, and then constructing a candidate pulse sequence corresponding to each candidate radio frequency pulse information according to the preset waveform, the basic gradient waveform can be selected for each sub-radio frequency pulse, so as to continuously adjust the gradient waveform in the subsequent optimization process.

[0072] In an embodiment, the optimization of the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information can include the following steps:

[0073] For each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result; the sub-radio frequency pulse waveform in the first optimization result is adjusted based on a second optimization condition to obtain a second optimization result; and the second optimization result corresponding to each candidate pulse sequence is taken as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information.

[0074] In an example, as Figure 2 shown, taking the parallel emission hard pulse scenario in the parallel emission body excitation scenario as an example, different amplitude and phase hard pulse strings are emitted by multiple channels, and gradients in three direction dimensions are applied, such as the gradient waveforms required to be applied in the x, y, and z spatial directions. The joint optimization of the gradient waveforms and the radio frequency pulse can be performed in the following manner:

[0075] The total number of sub-radio frequency pulses can be set to 5, 7, 9, etc. respectively, and then the gradient waveforms and the radio frequency pulse corresponding to each sub-radio frequency pulse number can be optimized respectively. The same initial gradient waveform is set for each sub-radio frequency pulse number to obtain each candidate pulse sequence, and then the conjugate gradient method can be used to optimize the radio frequency pulse in each candidate pulse sequence, i.e., the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition, and the interior point method can be used to optimize the sub-radio frequency pulse waveform in each candidate pulse sequence based on the optimized radio frequency pulse in the obtained first optimization result, i.e., the sub-radio frequency pulse waveform in the first optimization result is adjusted based on a second optimization condition, to jointly optimize the gradient waveforms and the radio frequency pulse under different sub-radio frequency pulse numbers, i.e., to optimize the candidate pulse sequence.

[0076] In yet another example, the optimization function for jointly optimizing the gradient waveforms and the multi-channel radio frequency pulse can be as follows:

[0077]

[0078] A = exp(i2πxk x +yk y +zk z )

[0079] k = ∫g(t)dt

[0080] where b is the desired radio frequency pulse, g is the final obtained gradient waveform in three directions, A is a system matrix determined by the gradient waveform generated by each iteration, W is a weight matrix used to weigh the weight of the excitation region and the non-excitation region, S is the collected B1 map, λ is a regularization coefficient, such as can use a digital 8, d is the expected local excitation shape determined by the selected shape mask and the folding angle α:

[0081] d = mask*sinα

[0082] In this embodiment, for each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on the first optimization condition to obtain a first optimization result, the sub-radio frequency pulse waveform in the first optimization result is adjusted based on the second optimization condition to obtain a second optimization result, and the second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information, which provides data support for further pulse evaluation of each optimized candidate pulse sequence.

[0083] In one embodiment, the step of adjusting the sub-radio frequency pulse waveform in the first optimization result based on the second optimization condition to obtain a second optimization result can include the following steps:

[0084] The preset waveform is updated by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result.

[0085] When optimizing the gradient waveform and the parallel emission pulse jointly, the gradient waveform corresponding to each sub-radio frequency pulse can be updated by adjusting the gradient switching rate (i.e., the waveform parameter), and then the waveform amplitude corresponding to each sub-radio frequency pulse and the amplitude and phase of each RF can be determined by optimization.

[0086] In this embodiment, the preset waveform is updated by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result, which can minimize the influence of eddy current effect on the excitation field and improve the effect of magnetic resonance parallel emission pulse.

[0087] In one embodiment, the preset waveform can include a preset gradient waveform, and the waveform parameter can include a gradient switching rate. The updating of the preset waveform by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result can include the following steps:

[0088] For each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined. The second optimization result is obtained through multiple iteration optimizations.

[0089] The gradient determination result can be used to represent whether the gradient maximum value and / or the gradient switching rate of the target gradient waveform meet the preset condition.

[0090] In actual application, the specific steps of optimizing the gradient waveform can be: calculating the partial derivative of the optimization function f with respect to g and the second-order approximate derivative, then the gradient waveform of each iteration (i.e. the target gradient waveform) can be calculated, and it can be judged whether the gradient maximum value and the gradient switching rate meet the maximum limit. If the maximum limit is exceeded, the gradient amplitude increment generated by each iteration can be halved.

[0091] In this embodiment, by determining the target gradient waveform corresponding to each iteration optimization and the gradient determination result for each sub-radio frequency pulse in the first optimization result, and then obtaining the second optimization result through multiple iteration optimizations, the basic gradient waveform can be selected for each sub-radio frequency pulse, and the gradient waveform can be continuously adjusted in the optimization process, so that the expected excitation field reaches a better uniformity while being closer to the effect of the real excitation field.

[0092] In one embodiment, the determination of the target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on the pulse evaluation result corresponding to each of the optimization candidate pulse sequences can include the following steps:

[0093] In combination with the magnetic resonance parallel emission application information and the pulse evaluation result corresponding to each of the optimization candidate pulse sequences, the target radio frequency pulse information is determined from the plurality of candidate radio frequency pulse information.

[0094] In an example, which gradient waveform and radio frequency pulse under which number of sub-radio frequency pulses can be used can be determined according to specific applications. If the implementation sequence is a 3D sequence body excitation, the sub-radio frequency pulse can be selected as a hard pulse. If the implementation function is 2D layer selection, the sub-radio frequency pulse can be selected as a sinc, SLR, gauss pulse, etc. If it is a corresponding layer direction gradient waveform, a rectangular waveform needs to be selected. If the implementation function is a 3D slab (3D layer block excitation, i.e. three-dimensional excitation of a relatively thick layer), the sub-radio frequency pulse can be selected as a sinc, SLR, gauss pulse, etc., and the corresponding z-direction gradient waveform is a rectangular or triangular waveform.

[0095] In this embodiment, by combining the magnetic resonance parallel transmission application information and the pulse evaluation results corresponding to each optimization candidate pulse sequence, the target radio frequency pulse information is determined from the plurality of candidate radio frequency pulse information, which can adapt to different application scenarios to generate a magnetic resonance pulse sequence.

[0096] In one embodiment, before the step of obtaining the target pulse sequence according to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information, the following steps can be included:

[0097] In the case where the uniformity information or the pulse duration information corresponding to the optimization candidate pulse sequence does not satisfy the preset evaluation condition, the plurality of candidate radio frequency pulse information is re-determined, and the step of obtaining the candidate pulse sequence corresponding to each of the plurality of candidate radio frequency pulse information is returned.

[0098] In an example, by iterating each candidate pulse sequence the same number of times, the radio frequency pulse and the gradient waveform under different sub-radio frequency pulse quantities can be obtained, as shown in FIG. 5, and then the excitation uniformity NRMSE (i.e., the uniformity information) under different sub-radio frequency pulse quantities can be calculated according to the data, which can be calculated in the following manner: Figure 3

[0099]

[0100] Wherein, b is the radio frequency pulse to be obtained, A is the system matrix determined by the gradient waveform generated by each iteration, S is the B1 map acquired, and d is the expected local excitation shape.

[0101] In another example, after the excitation uniformity is calculated, the total pulse duration (i.e., the pulse duration information) under different sub-radio frequency pulse quantities can be judged at the same time to determine the optimal sub-radio frequency pulse quantity under which the transmission radio frequency pulse and the gradient waveform have a smaller radio frequency excitation field with eddy current effect; if the total pulse duration or the uniformity is detected to be not as expected (i.e., the preset evaluation condition is not satisfied), different sub-radio frequency pulse quantities can be re-designed and optimization can be re-performed.

[0102] For example, a fixed NRMSE value can be set according to the image quality, if the calculated NRMSE value is greater than the set value, optimization is continued, and if the calculated NRMSE value is less than or equal to the set value, it is considered to be as expected.

[0103] In this embodiment, by re-determining the plurality of candidate radio frequency pulse information in the case where the uniformity information or the pulse duration information corresponding to the optimization candidate pulse sequence does not satisfy the preset evaluation condition, and returning to the step of obtaining the candidate pulse sequence corresponding to each of the plurality of candidate radio frequency pulse information, the optimization effect of the magnetic resonance parallel transmission pulse is ensured.

[0104] ​In one embodiment, as shown in FIG. 1, there is provided a flowchart illustrating another method for generating a magnetic resonance pulse sequence. In this embodiment, the method comprises the following steps: Figure 4

[0105] In step 401, a plurality of preset candidate radio frequency pulse information is acquired, and for a preset waveform of a sub-radio frequency pulse, a candidate pulse sequence corresponding to each candidate radio frequency pulse information is constructed according to the preset waveform. The candidate radio frequency pulse information is used to represent the number of sub-radio frequency pulses applied by the radio frequency pulse channel. In step 402, for each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result. In step 403, for each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet the preset condition. In step 404, through multiple iteration optimizations, a second optimization result is obtained, and the second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information. In step 405, in combination with the magnetic resonance parallel emission application information and the pulse evaluation result corresponding to each optimized candidate pulse sequence, the target radio frequency pulse information is determined from the plurality of candidate radio frequency pulse information. In step 406, in the case where the uniformity information or the pulse length information of the optimized candidate pulse sequence does not meet the preset evaluation condition, the plurality of candidate radio frequency pulse information is re-determined. In step 407, the target pulse sequence is obtained according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information. It should be noted that the specific definition of the above steps can refer to the specific definition of the above-mentioned one magnetic resonance pulse sequence generation method, and will not be described here.

[0106] It should be understood that, although each step in the flowchart involved in each embodiment as described above is displayed in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps has no strict sequence limitation, and these steps can be executed in other orders. Moreover, at least part of the steps in the flowchart involved in each embodiment as described above can include multiple steps or stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least part of other steps or steps or stages in other steps.

[0107] ​Based on the same inventive concept, the application further provides a magnetic resonance pulse sequence generation device for implementing the magnetic resonance pulse sequence generation method described above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme described in the above method, so the specific limitations in one or more magnetic resonance pulse sequence generation device embodiments provided below can be referred to the limitations of the magnetic resonance pulse sequence generation method in the above, which will not be repeated here.

[0108] In one embodiment, as shown in Figure 5 a magnetic resonance pulse sequence generation device is provided, comprising:

[0109] A candidate pulse sequence acquisition module 501 is configured to acquire a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform;

[0110] A parallel optimization module 502 is configured to optimize the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information;

[0111] A target radio frequency pulse information determination module 503 is configured to determine target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on pulse evaluation results corresponding to each optimized candidate pulse sequence; the pulse evaluation results include uniformity information and pulse duration information;

[0112] A target pulse sequence obtaining module 504 is configured to obtain a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information.

[0113] In one embodiment, the candidate pulse sequence acquisition module 501 comprises:

[0114] A pulse number and waveform acquisition sub-module is configured to acquire a plurality of preset candidate radio frequency pulse information and a preset waveform for a sub-radio frequency pulse; the candidate radio frequency pulse information is used to represent the number of sub-radio frequency pulses applied by a radio frequency pulse channel;

[0115] A candidate pulse sequence construction sub-module is configured to construct a candidate pulse sequence corresponding to each candidate radio frequency pulse information according to the preset waveform;

[0116] Wherein, the candidate pulse sequence contains sub-radio frequency pulses corresponding to the number of sub-radio frequency pulses, and each sub-radio frequency pulse has a corresponding initial waveform parameter.

[0117] In one embodiment, the parallel optimization module 502 comprises:

[0118] The radio frequency pulse optimization submodule is configured to adjust the radio frequency pulse of each candidate pulse sequence based on the first optimization condition to obtain a first optimization result;

[0119] The gradient waveform optimization submodule is configured to adjust the sub-radio frequency pulse waveform in the first optimization result based on a second optimization condition to obtain a second optimization result.

[0120] The optimization candidate pulse sequence obtaining submodule is configured to take the second optimization result corresponding to each candidate pulse sequence as the optimization candidate pulse sequence corresponding to each candidate radio frequency pulse information.

[0121] In an embodiment, the gradient waveform optimization submodule comprises:

[0122] The waveform parameter adjustment unit is configured to update the preset waveform by adjusting the waveform parameter corresponding to each sub-radio frequency pulse in the first optimization result to obtain the second optimization result.

[0123] In an embodiment, the preset waveform comprises a preset gradient waveform, the waveform parameter comprises a gradient switching rate, and the waveform parameter adjustment unit comprises:

[0124] The gradient determination subunit is configured to determine, for each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet a preset condition.

[0125] The iteration subunit is configured to obtain the second optimization result through multiple iteration optimizations.

[0126] In an embodiment, the target radio frequency pulse information determination module 503 comprises:

[0127] The application information combination submodule is configured to combine the magnetic resonance parallel emission application information and the pulse evaluation result corresponding to each optimization candidate pulse sequence to determine the target radio frequency pulse information from the plurality of candidate radio frequency pulse information.

[0128] In an embodiment, the device further comprises:

[0129] The re-optimization module is configured to, in a case where the uniformity information or the pulse length information corresponding to the optimization candidate pulse sequence does not meet a preset evaluation condition, re-determine a plurality of candidate radio frequency pulse information and return to the step of obtaining the candidate pulse sequence corresponding to each of the plurality of candidate radio frequency pulse information.

[0130] In an embodiment, the number of different sub-radio frequency pulses is an odd number.

[0131] Each module in the aforementioned magnetic resonance pulse sequence generation device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware within or independently of the processor in a computer device, or stored in software within the memory of a computer device, so that the processor can call and execute the operations corresponding to each module.

[0132] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 6 As shown, the computer device includes a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computational and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When executed by the processor, the computer program implements a method for generating magnetic resonance pulse sequences.

[0133] Those skilled in the art will understand that Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0134] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0135] Obtain candidate pulse sequences corresponding to multiple candidate radio frequency pulse information; different candidate radio frequency pulse information corresponds to different numbers of sub-radio frequency pulses, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform;

[0136] Optimize the radio frequency pulse and sub-radio frequency pulse waveforms in each of the candidate pulse sequences to obtain the optimized candidate pulse sequence corresponding to each of the candidate radio frequency pulse information;

[0137] Based on the pulse evaluation results corresponding to each of the optimized candidate pulse sequences, the target radio frequency pulse information is determined from the multiple candidate radio frequency pulse information; the pulse evaluation results include uniformity information and pulse duration information.

[0138] According to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information, a target pulse sequence is obtained.

[0139] In one embodiment, the processor, when executing the computer program, also implements the steps of the magnetic resonance pulse sequence generation method in the other embodiments described above.

[0140] In one embodiment, a computer readable storage medium is provided, and a computer program is stored on the computer readable storage medium, and the computer program, when executed by a processor, implements the following steps:

[0141] A plurality of candidate radio frequency pulse information each corresponds to a candidate pulse sequence; different candidate radio frequency pulse information corresponds to different sub-radio frequency pulse quantity, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform;

[0142] Optimize the radio frequency pulse and the sub-radio frequency pulse waveform in each of the candidate pulse sequences to obtain an optimization candidate pulse sequence corresponding to each of the candidate radio frequency pulse information;

[0143] Based on the pulse evaluation result corresponding to each of the optimization candidate pulse sequences, a target radio frequency pulse information is determined from the plurality of candidate radio frequency pulse information; the pulse evaluation result includes uniformity information and pulse duration information;

[0144] According to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information, a target pulse sequence is obtained.

[0145] In one embodiment, the computer program, when executed by a processor, also implements the steps of the magnetic resonance pulse sequence generation method in the other embodiments described above.

[0146] In one embodiment, a computer program product is provided, and the computer program product includes a computer program, and the computer program, when executed by a processor, implements the following steps:

[0147] A plurality of candidate radio frequency pulse information each corresponds to a candidate pulse sequence; different candidate radio frequency pulse information corresponds to different sub-radio frequency pulse quantity, and each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform;

[0148] Optimize the radio frequency pulse and the sub-radio frequency pulse waveform in each of the candidate pulse sequences to obtain an optimization candidate pulse sequence corresponding to each of the candidate radio frequency pulse information;

[0149] Based on the pulse evaluation result corresponding to each of the optimization candidate pulse sequences, a target radio frequency pulse information is determined from the plurality of candidate radio frequency pulse information; the pulse evaluation result includes uniformity information and pulse duration information;

[0150] According to the optimization candidate pulse sequence corresponding to the target radio frequency pulse information, a target pulse sequence is obtained.

[0151] In one embodiment, the computer program, which when executed by the processor, also implements the steps of the method of generating a magnetic resonance pulse sequence in the other embodiments described above.

[0152] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, the computer program can include the processes of the above-mentioned embodiments. Any reference to a memory, a database or other medium in the embodiments provided in the present application can include at least one of a non-volatile memory and a volatile memory. The non-volatile memory can include a read-only memory (ROM), a magnetic tape, a floppy disk, a flash memory, an optical storage, a high-density embedded non-volatile memory, a resistive random access memory (ReRAM), a magnetoresistive random access memory (MRAM), a ferroelectric random access memory (FRAM), a phase change memory (PCM), a graphene memory, etc. The volatile memory can include a random access memory (RAM) or an external cache memory, etc. As an illustration but not as a limitation, the RAM can be in various forms, such as a static random access memory (SRAM) or a dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., and is not limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., and is not limited thereto.

[0153] Any combination of the technical features of the above embodiments can be made. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0154] The above-described embodiments are merely illustrative of several embodiments of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method of magnetic resonance pulse sequence generation, characterized by, The method comprises: obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform; optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; wherein, for each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result; for each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet the preset condition; through multiple iteration optimizations, a second optimization result is obtained; the second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; determining a target radio frequency pulse information from a plurality of candidate radio frequency pulse information based on a pulse evaluation result corresponding to each optimized candidate pulse sequence; the pulse evaluation result includes uniformity information and pulse duration information; obtaining a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information.

2. The method of claim 1, wherein, The method comprises: obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform; optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; wherein, for each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result; for each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet the preset condition; through multiple iteration optimizations, a second optimization result is obtained; the second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; determining a target radio frequency pulse information from a plurality of candidate radio frequency pulse information based on a pulse evaluation result corresponding to each optimized candidate pulse sequence; the pulse evaluation result includes uniformity information and pulse duration information; 3. The method of claim 1, wherein, obtaining a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information. The method comprises:

4. The method of claim 1, wherein, obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform; optimizing the radio frequency pulse and the sub-radio frequency pulse waveform in each candidate pulse sequence to obtain an optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; wherein, for each candidate pulse sequence, the radio frequency pulse of the candidate pulse sequence is adjusted based on a first optimization condition to obtain a first optimization result; for each sub-radio frequency pulse in the first optimization result, a target gradient waveform corresponding to each iteration optimization and a gradient determination result are determined; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet the preset condition; through multiple iteration optimizations, a second optimization result is obtained; the second optimization result corresponding to each candidate pulse sequence is used as the optimized candidate pulse sequence corresponding to each candidate radio frequency pulse information; 5. The method according to any one of claims 1 to 4, characterized in that, determining a target radio frequency pulse information from a plurality of candidate radio frequency pulse information based on a pulse evaluation result corresponding to each optimized candidate pulse sequence; the pulse evaluation result includes uniformity information and pulse duration information; 6. A magnetic resonance pulse sequence generation apparatus, characterized by obtaining a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information. The number of different sub-radio frequency pulses is an odd number. The device comprises: a candidate pulse sequence acquisition module for obtaining a plurality of candidate pulse sequences corresponding to a plurality of candidate radio frequency pulse information respectively; different candidate radio frequency pulse information corresponds to different number of sub-radio frequency pulses, each sub-radio frequency pulse in the candidate pulse sequence has the same preset waveform; The parallel optimization module is configured to optimize radio frequency pulses and sub-radio frequency pulse waveforms in each of the candidate pulse sequences to obtain an optimized candidate pulse sequence corresponding to each of the candidate radio frequency pulse information; wherein, for each of the candidate pulse sequences, the radio frequency pulses of the candidate pulse sequence are adjusted based on a first optimization condition to obtain a first optimization result; for each of the sub-radio frequency pulses in the first optimization result, a target gradient waveform corresponding to each iteration of optimization and a gradient determination result are determined; the gradient determination result is used to represent whether the maximum gradient platform value and / or the gradient switching rate of the target gradient waveform meet a preset condition; through multiple iterations of optimization, a second optimization result is obtained; and the second optimization result corresponding to each of the candidate pulse sequences is taken as the optimized candidate pulse sequence corresponding to each of the candidate radio frequency pulse information; The target radio frequency pulse information determination module is configured to determine target radio frequency pulse information from the plurality of candidate radio frequency pulse information based on pulse evaluation results corresponding to each of the optimized candidate pulse sequences; the pulse evaluation results include uniformity information and pulse duration information; The target pulse sequence obtaining module is configured to obtain a target pulse sequence according to the optimized candidate pulse sequence corresponding to the target radio frequency pulse information.

7. The apparatus of claim 6, wherein, The candidate pulse sequence obtaining module includes: The pulse number and waveform obtaining submodule is configured to obtain a plurality of preset candidate radio frequency pulse information and a preset waveform of a sub-radio frequency pulse; the candidate radio frequency pulse information is used to represent the number of sub-radio frequency pulses applied by a radio frequency pulse channel; The candidate pulse sequence construction submodule is configured to construct a candidate pulse sequence corresponding to each of the candidate radio frequency pulse information according to the preset waveform; The candidate pulse sequence includes a sub-radio frequency pulse corresponding to the number of sub-radio frequency pulses, and each sub-radio frequency pulse has a corresponding initial waveform parameter.

8. The apparatus of claim 6, wherein, The target radio frequency pulse information determination module includes: The application information combination submodule is configured to combine magnetic resonance parallel emission application information and pulse evaluation results corresponding to each of the optimized candidate pulse sequences to determine the target radio frequency pulse information from the plurality of candidate radio frequency pulse information.

9. The apparatus of claim 6, wherein, The device further includes: The re-optimization module is configured to re-determine a plurality of candidate radio frequency pulse information and return to the step of obtaining a candidate pulse sequence corresponding to each of the plurality of candidate radio frequency pulse information in the case where the uniformity information or the pulse duration information corresponding to the optimized candidate pulse sequence does not meet a preset evaluation condition. 10.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-9. The processor executes the computer program to implement the steps of the method in any one of claims 1 to 5.

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