Spectrum measurement method and apparatus in nuclear magnetic resonance, device and storage medium

Abstract

A spectrum measurement method and apparatus in nuclear magnetic resonance, a device, and a storage medium. A target sample is arranged in a uniform magnetic field, a target direction of the target sample is consistent with the uniform magnetic field, a gradient coil is arranged on the target sample, and the method comprises: applying a linear gradient magnetic field in the target direction of the target sample; determining a uniform region of a radio frequency coil on the basis of a bandwidth of a radio frequency pulse signal; during reception of a nuclear magnetic resonance echo signal, adjusting the magnitude of the linear gradient magnetic field under the condition of a target flip angle until a region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil to obtain a target linear gradient magnetic field; obtaining a target nuclear magnetic resonance echo signal on the basis of the target linear gradient magnetic field; and performing inversion on the target nuclear magnetic resonance echo signal to obtain a T1-T2 spectrum. The problem of T1‑end tailing caused by conventional T1-T2 measurements is solved, thereby greatly improving the measurement accuracy.

Description

A method, apparatus, device, and storage medium for spectral measurement in nuclear magnetic resonance.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510073863X, filed on January 17, 2025, entitled "A method, apparatus, device and storage medium for spectral measurement in nuclear magnetic resonance", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of nuclear magnetic resonance technology, specifically to a method, apparatus, equipment, and storage medium for spectral measurement in nuclear magnetic resonance. Background Technology

[0004] Nuclear magnetic resonance (NMR) technology, as a non-destructive analytical method, has wide applications in materials science, biomedicine, geological exploration, and other fields. In NMR technology, the radio frequency coil contains homogeneous and non-homogeneous regions. The homogeneous region of the radio frequency coil refers to the area where the radio frequency magnetic field strength is relatively uniform and has little variation during the NMR experiment; in contrast, the non-homogeneous region of the radio frequency coil refers to the area where the radio frequency magnetic field strength varies significantly.

[0005] In the non-uniform region, due to the inhomogeneity of the radio frequency magnetic field, atomic nuclei at different locations will be excited by radio frequency at different frequencies, leading to frequency broadening and reduced resolution of the NMR signal, severely causing data distortion and affecting quantitative test results. Furthermore, there is the T1 tailing problem. For example, in core measurements, when the core length is greater than the coil detection range, both linear and nonlinear regions contribute to the signal. However, in two-dimensional measurements, the flip angle of the nonlinear region is inconsistent with that of the linear region, often resulting in T1 non-convergence after inversion, which can introduce errors for identifying unconventional reservoir fluids. Traditional NMR T1-T2 measurements are performed in a uniform field, which imposes certain limitations on sample length. For NMR measurements of long samples, it is often necessary to cut the sample to a specified length before placing it in the uniform region for measurement.

[0006] Therefore, there is an urgent need for a spectral measurement method for long samples in nuclear magnetic resonance, which can solve the problems of signal distortion in non-uniform regions and T1 tailing in traditional spectral measurement methods in nuclear magnetic resonance. Summary of the Invention

[0007] In view of this, this application provides a spectrum measurement method, apparatus, device and storage medium in nuclear magnetic resonance, which can solve the problems of signal distortion in non-uniform regions and T1 tail in traditional spectrum measurement methods in nuclear magnetic resonance. The technical solution is as follows.

[0008] In a first aspect, this application provides a method for spectral measurement in nuclear magnetic resonance, wherein a target sample is placed in a uniform magnetic field, the target direction of the target sample is consistent with the uniform magnetic field, and a gradient coil is disposed on the target sample, the method comprising:

[0009] A linear gradient magnetic field is applied in the target direction of the target sample;

[0010] Radio frequency pulse signals are emitted to the target sample through a radio frequency coil, and the uniform region of the radio frequency coil is determined based on the bandwidth of the radio frequency pulse signal.

[0011] During the reception of nuclear magnetic resonance echo signals, the gradient value of the linear gradient magnetic field is adjusted based on the target rotation angle until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thus obtaining the target linear gradient magnetic field.

[0012] Based on the target's linear gradient magnetic field, the target's nuclear magnetic resonance echo signal is obtained;

[0013] The T1-T2 spectrum was obtained by inverting the nuclear magnetic resonance echo signal of the target.

[0014] In one alternative implementation, the gradient coil consists of a plurality of current coils; the target direction includes the axial direction of the target sample.

[0015] In one optional implementation, applying a linear gradient magnetic field in the target direction of the target sample includes: adjusting the current direction of the current coil such that a linear gradient magnetic field is applied in the axial direction of the target sample. Adjusting the gradient value of the linear gradient magnetic field includes: adjusting the magnitude of the gradient value of the linear gradient magnetic field by adjusting the current magnitude of the current coil.

[0016] In one optional implementation, the inversion of the target nuclear magnetic resonance echo signal to obtain the T1-T2 spectrum includes:

[0017] Based on the target rotation angle, determine the T1-T2 data response model;

[0018] Based on the target nuclear magnetic resonance echo signal, the T1-T2 data response model is inverted to obtain the T1-T2 spectrum.

[0019] In one optional implementation, the expression for the T1-T2 data response model is: b ij =∑∑f(T1,T2)[1-exp(-TR / T1)]exp(-TE / T2);

[0020] In the formula, T1 is the longitudinal relaxation time, T2 is the transverse relaxation time, TR is the waiting time, TE is the echo interval, and b is the number of seconds.ij This represents the signal amplitude at time j in the i-th echo train, given the TR waiting time and the TE echo interval.

[0021] In one alternative implementation, the lever rotation angle is 90 degrees.

[0022] The spectral measurement method in nuclear magnetic resonance provided in this application has the following advantages.

[0023] The spectral measurement method in nuclear magnetic resonance (NMR) of this application is applied to the measurement of long target samples. A gradient coil, composed of multiple current coils, is placed on the target sample. First, the target sample is placed within a main magnetic field, ensuring its axial direction aligns with the main magnetic field direction. The main magnetic field is set as a uniform magnetic field. Then, the current coils are energized, generating a linear gradient magnetic field. The direction of this linear gradient magnetic field is consistent with the main magnetic field, and its magnitude is controlled by the current in the current coils. Radio frequency (RF) pulse signals are emitted to the target sample through an RF coil, exciting the atomic nuclei of the target sample and generating an NMR signal. The RF coils then acquire the NMR signal generated by the target sample. The spectral measurement method in NMR of this application requires confining the NMR signal region to the uniform region of the RF coils. Therefore, the rotation angle of the T1-T2 data response model is confirmed to be 90 degrees. Using this target rotation angle as a condition, the gradient value of the linear gradient magnetic field is adjusted, i.e., the current in the current coils is adjusted, thereby confining the NMR signal region to the uniform region of the RF coils. The gradient value of the linear gradient magnetic field at this point is recorded. The uniform region of the RF coil is determined by calculating the excitation and reception thickness of the NMR signal based on the bandwidth of the RF pulse signal. The uniform region of the RF coil can then be determined from the excitation and reception thickness. The target NMR signal is acquired based on the gradient value of the linear gradient magnetic field set at this point. Since the rotation angle is constrained to 90 degrees, the expression of the T1-T2 data response model is consistent with that of the T1-T2 inversion model, solving the tailing problem caused by the inconsistency between the response model and the inversion model in conventional testing methods. Therefore, the T1-T2 spectrum can be obtained by inverting the target NMR signal. The spectral measurement method in NMR of this application, by applying a linear gradient magnetic field to the sample and adjusting the gradient output magnitude to match the bandwidth of the RF pulse signal, constrains the NMR signal within the uniform region of the RF coil. This solves the signal distortion in the non-uniform region and the T1 tailing problem that exists in traditional T1-T2 measurements of long samples, greatly improving measurement accuracy.

[0024] Secondly, this application provides a spectral measurement device for nuclear magnetic resonance, wherein a target sample is placed in a uniform magnetic field, the target direction of the target sample is consistent with the uniform magnetic field, and a gradient coil is disposed on the target sample. The device includes:

[0025] The linear gradient magnetic field application module is used to apply a linear gradient magnetic field in the target direction of the target sample.

[0026] The uniform region determination module is used to transmit an RF pulse signal to the target sample through the RF coil and determine the uniform region of the RF coil based on the bandwidth of the RF pulse signal.

[0027] The linear gradient magnetic field adjustment module is used to adjust the gradient value of the linear gradient magnetic field during the reception of nuclear magnetic resonance echo signals, based on the target rotation angle, until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thereby obtaining the target linear gradient magnetic field.

[0028] The acquisition module is used to obtain the target nuclear magnetic resonance echo signal based on the target's linear gradient magnetic field.

[0029] The inversion module is used to invert the nuclear magnetic resonance echo signal of the target to obtain the T1-T2 spectrum.

[0030] Thirdly, this application provides a computer device, including: a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor executes the computer instructions to perform the spectral measurement method in nuclear magnetic resonance as described in the first aspect or any corresponding embodiment.

[0031] Fourthly, this application provides a computer-readable storage medium storing computer instructions for causing a computer to perform the spectral measurement method in nuclear magnetic resonance according to the first aspect or any corresponding embodiment described above.

[0032] Fifthly, this application provides a computer program product, including computer instructions for causing a computer to execute the spectral measurement method in nuclear magnetic resonance according to the first aspect or any corresponding embodiment thereof. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 is a schematic flowchart illustrating a method for spectral measurement in nuclear magnetic resonance according to an exemplary embodiment.

[0035] Figure 2 is a schematic diagram of an SR-CPMG sequence diagram according to an exemplary embodiment.

[0036] Figure 3 is a schematic diagram of an SR-CPMG-G sequence diagram according to an exemplary embodiment.

[0037] Figure 4 is a schematic diagram of the turning angle according to an exemplary embodiment.

[0038] Figure 5 is a schematic diagram illustrating the results of a conventional SR-CPMG test on a long water film sample according to an exemplary embodiment.

[0039] Figure 6 is a schematic diagram illustrating the results of SR-CPMG-G testing on a long water film sample according to an exemplary embodiment.

[0040] Figure 7 is a schematic diagram illustrating the results of conventional SR-CPMG testing of a long mudstone shale sample according to an exemplary embodiment.

[0041] Figure 8 is a schematic diagram illustrating the results of SR-CPMG-G testing on a long mudstone shale sample according to an exemplary embodiment.

[0042] Figure 9 is a schematic diagram of the structure of a spectrum measurement device in nuclear magnetic resonance provided in an embodiment of this application.

[0043] Figure 10 is a schematic diagram of the structure of a computer device provided in an optional embodiment of this application. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] It should be understood that the term "instruction" mentioned in the embodiments of this application can be a direct instruction, an indirect instruction, or an indication of a relationship. For example, A instructing B can mean that A directly instructs B, such as B being able to obtain information through A; it can also mean that A indirectly instructs B, such as A instructing C, so B can obtain information through C; or it can mean that there is a relationship between A and B.

[0046] In the description of the embodiments of this application, the term "correspondence" may indicate that there is a direct or indirect correspondence between two things, or that there is an association between two things, or that there is a relationship of instruction and being instructed, configuration and being configured, etc.

[0047] In the embodiments of this application, "predefined" can be achieved by pre-storing corresponding codes, tables or other means that can be used to indicate relevant information in the device (e.g., including terminal devices and network devices). This application does not limit the specific implementation method.

[0048] Nuclear magnetic resonance (NMR) technology, as a non-destructive analytical method, has wide applications in materials science, biomedicine, and geological exploration. NMR technology can bypass the framework response of porous media and directly obtain hydrogen-containing signals in porous fluids, achieving excellent results in the evaluation of fluid properties in petroleum geology and materials science. One-dimensional NMR can obtain porosity and pore size distribution in porous media, while two-dimensional NMR can obtain fluid type and saturation information.

[0049] In NMR technology, the radio frequency (RF) coil contains both homogeneous and non-homogeneous regions. The homogeneous region of the RF coil refers to the area where the RF magnetic field strength is relatively uniform and varies little during NMR experiments. Conversely, the non-homogeneous region of the RF coil refers to the area where the RF magnetic field strength varies significantly. Within this region, due to the inhomogeneity of the RF magnetic field, atomic nuclei at different locations will be excited by RF at different frequencies, leading to frequency broadening and reduced resolution of the NMR signal, severely distorting the data and affecting quantitative test results. Furthermore, when the core length exceeds the coil's detection range during core measurements, both linear and nonlinear regions contribute to the signal. However, in two-dimensional measurements, the flip angle of the nonlinear region is inconsistent with that of the linear region, often resulting in T1 non-convergence after inversion, which can introduce errors for identifying unconventional reservoir fluids. Traditional NMR measurements of porous media are performed in a homogeneous field, which imposes certain limitations on sample length. For NMR measurements of long cores, it is often necessary to cut the sample to a specified length before placing it in the homogeneous region for measurement.

[0050] In nuclear magnetic resonance (NMR), T1 (longitudinal relaxation time) and T2 (transverse relaxation time) are important parameters describing the nuclear spin relaxation process in a sample or tissue. The tailing effect in T1 and T2 measurements can affect the accuracy of the data, leading to measurement errors. Tailing refers to the phenomenon where, during signal acquisition, the signal decay curve, after ideal exponential decay, exhibits a non-ideal tail; that is, the signal decay process becomes slower, or the curve does not completely decay to zero at the end. This phenomenon often results in the fitted curve in T1 and T2 measurements not accurately reflecting the true relaxation process, thus affecting the precision of the measurement results.

[0051] The tailing phenomenon can be caused by multiple factors. Common causes include: In NMR experiments, local magnetic field inhomogeneity can lead to different relaxation characteristics of the magnetization vector in different regions, resulting in signal tailing. Furthermore, magnetic field inhomogeneity can originate from interference from the sample itself, the container, the equipment, or the external environment. Non-ideal performance of the NMR instrument hardware (such as radio frequency pulses, probes, and receiving systems) can lead to incomplete signal attenuation. In particular, bandwidth limitations of the receiving system or incomplete time-domain response of the pulse can cause signal tailing.

[0052] Therefore, the problems of signal distortion in the non-uniform region and T1 tailing in NMR T1-T2 measurements of long samples urgently need to be solved. This application provides a spectral measurement method in NMR that, by applying a specific linear gradient magnetic field along the sample's axial direction, can effectively and selectively excite and detect information in a specific layer of the sample. This solves the problem of signal distortion in the non-uniform region. Furthermore, by changing the gradient value, the NMR signal contribution region is constrained, resolving the T1 non-convergence problem caused by signal contribution in the non-uniform region. Simultaneously, high-resolution T1-T2 measurement data of the sample can be obtained, thus solving the problems of signal distortion in the non-uniform region and T1 tailing in traditional NMR spectral measurement methods for long samples.

[0053] The spectral measurement method in nuclear magnetic resonance of this embodiment involves placing a target sample in a uniform magnetic field, with the target direction of the target sample aligned with the uniform magnetic field, and a gradient coil disposed on the target sample. The method flowchart of this embodiment is shown in Figure 1, and includes the following steps.

[0054] S101. Apply a linear gradient magnetic field in the target direction of the target sample.

[0055] Specifically, in step S101, the target sample is a long sample, which can be a long core sample. The target direction is the axial direction of the target sample; for a long core sample, it is the direction of its core length. The linear gradient magnetic field is applied by a gradient coil, which consists of multiple current coils. By changing the direction and magnitude of the current in the current coils, the direction and gradient value of the linear gradient magnetic field can be changed.

[0056] S102. A radio frequency pulse signal is emitted to the target sample through the radio frequency coil, and the uniform region of the radio frequency coil is determined based on the bandwidth of the radio frequency pulse signal.

[0057] Specifically, in step S102, an radio frequency pulse signal is emitted to the target sample through a radio frequency coil to excite the atomic nuclei of the target sample to resonate, thereby generating a nuclear magnetic resonance signal, and the generated nuclear magnetic resonance signal is acquired through the radio frequency coil.

[0058] Optionally, in traditional nuclear magnetic resonance methods, nuclear magnetic resonance echo signals are generally acquired using the SR-CPMG (Steady-State Refocusing CPMG) sequence. The SR-CPMG sequence is shown in Figure 2. The SR-CPMG sequence is a pulse sequence commonly used in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI), mainly to improve the steady-state response of the signal and reduce signal attenuation in experiments.

[0059] This embodiment introduces gradient pulses into the SR-CPMG sequence, specifically using the SR-CPMG-G sequence (Steady-State Refocusing CPMG with Gradient) for NMR echo signal acquisition. The SR-CPMG-G sequence diagram is shown in Figure 3. The SR-CPMG-G sequence combines the advantages of the steady-state refocusing CPMG (SR-CPMG) sequence with the introduction of gradient pulses to achieve spatial coding or other optimization purposes. Its main applications typically include spatial resolution enhancement and signal enhancement in NMR and MRI. The SR-CPMG-G sequence maintains steady-state magnetization and refocuses transverse magnetization through periodic 180° pulses. This helps reduce the effects of transverse relaxation and improves signal stability.

[0060] In the above steps, due to the application of a linear gradient magnetic field, there is a linear difference in the nuclear resonance frequency H at various positions of the sample along the gradient direction. The finite bandwidth of the radio frequency pulse in the frequency domain determines the excitation and reception thickness of the nuclear magnetic resonance signal, i.e., the uniform region of the radio frequency coil. The expression for the excitation and reception thickness is: h = 1 / (P²*G) ΔB0 *γ);

[0061] In the formula, P2 is the pulse width, i.e., the pulse application time; G ΔB This indicates the magnitude of the applied gradient, where γ is the gyromagnetic ratio of the H nucleus, 42.58 MH. z / T.

[0062] S103. During the reception of nuclear magnetic resonance echo signals, the gradient value of the linear gradient magnetic field is adjusted based on the target rotation angle until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thereby obtaining the target linear gradient magnetic field.

[0063] Specifically, in step S103, the region of the NMR signal needs to be constrained within the uniform region of the radio frequency coil. This ensures that the expression of the T1-T2 signal response model is consistent with that of the T1-T2 inversion model, i.e., the rotation angle is 90 degrees. As shown in Figure 4, taking a long core sample as an example, the core length is greater than the length of the uniform region of the radio frequency coil. In addition to the signal contribution from the uniform region, there is also a signal contribution from the non-uniform region. In reality, the angle of the resonance region is 90°, and the angle of the non-resonance region is less than 90°. The rotation angle of the non-resonance region is not a constant and cannot be determined. Therefore, in its inversion model, only a 90° rotation angle can be selected as the inversion response model, and the rotation angle of the non-uniform region cannot be measured. Therefore, using the target rotation angle of 90 degrees as a condition, the current of the current coil is adjusted, thereby adjusting the gradient value of the gradient magnetic field until the region of the NMR signal is constrained within the uniform region of the radio frequency coil. When adjusting the gradient value of the gradient magnetic field, for the purpose of measurement effect, the gradient ramp time is set to 1-3 ms, and the gradient stabilization time is set to 10-30 ms. By combining gradient field pulse sequences and SR-CPMG sequences, the T1 tailing problem of traditional T1-T2 measurement methods for long samples can be solved.

[0064] In the above steps, the expression for the gradient value of the linear gradient magnetic field is: G A0 =1 / (P2*G) max *h*γ);

[0065] In the formula, h represents the excitation and receiving thicknesses; G max G is the maximum gradient; A0 γ represents the gradient output amplitude; γ is the H nucleus gyromagnetic ratio, 42.58 MH. z / T.

[0066] The traditional T1-T2 data response model is expressed as follows: b ij =∑∑∑f(T1,T2,α)[1-(1-cosα)exp(-TR / T1)]exp(-TE / T2);

[0067] Setting the rotation angle α = 90°, the T1-T2 data response model of this embodiment can be obtained, and its expression is: b ij =∑∑f(T1,T2)[1-exp(-TR / T1)]exp(-TE / T2);

[0068] The T1-T2 inversion model also uses this formula, thus ensuring consistency between the inversion model and the response model, and solving the tailing problem caused by inconsistency between models in conventional testing methods.

[0069] S104. Based on the target's linear gradient magnetic field, the target's nuclear magnetic resonance echo signal is obtained.

[0070] Specifically, in step S104, the gradient value of the gradient magnetic field is adjusted by regulating the current in the current coil until the region of the nuclear magnetic resonance signal is constrained within the uniform region of the radio frequency coil. The gradient value at this point is recorded, which is the target linear gradient magnetic field. Under this target linear gradient magnetic field, a radio frequency pulse signal is emitted to obtain the target nuclear magnetic resonance signal.

[0071] S105. The nuclear magnetic resonance echo signal of the target is inverted to obtain the T1-T2 spectrum.

[0072] Specifically, in step S105, after obtaining the target nuclear magnetic resonance signal, the T1-T2 spectrum can be obtained by inversion using the T1-T2 inversion model described above.

[0073] In summary, the spectral measurement method for nuclear magnetic resonance (NMR) provided in this application is applied to the measurement of long target samples. A gradient coil, composed of multiple current coils, is placed on the target sample. First, the target sample is placed within a main magnetic field, ensuring its axial direction aligns with the main magnetic field direction. The main magnetic field is set as a uniform magnetic field. Then, the current coils are energized to generate a linear gradient magnetic field, the direction of which is consistent with the main magnetic field. The magnitude of the linear gradient magnetic field is controlled by the current in the current coils. Radio frequency (RF) pulse signals are emitted to the target sample via an RF coil to excite the atomic nuclei of the target sample, generating an NMR signal. The RF coils then collect the NMR signal generated by the target sample. The spectral measurement method for NMR in this application requires confining the NMR signal region to a uniform region within the RF coils. Therefore, the rotation angle of the T1-T2 data response model is confirmed to be 90 degrees. Using this target rotation angle as a condition, the gradient value of the linear gradient magnetic field is adjusted, i.e., the current in the current coils is adjusted, thereby confining the NMR signal region to a uniform region within the RF coils. The gradient value of the linear gradient magnetic field at this point is recorded. The uniform region of the RF coil is determined by calculating the excitation and reception thickness of the NMR signal based on the bandwidth of the RF pulse signal. The uniform region of the RF coil can then be determined from the excitation and reception thickness. The target NMR signal is acquired based on the gradient value of the linear gradient magnetic field set at this point. Since the rotation angle is constrained to 90 degrees, the expression of the T1-T2 data response model is consistent with that of the T1-T2 inversion model, solving the tailing problem caused by the inconsistency between the response model and the inversion model in conventional testing methods. Therefore, the T1-T2 spectrum can be obtained by inverting the target NMR signal. The spectral measurement method in NMR of this application, by applying a linear gradient magnetic field to the sample and adjusting the gradient output magnitude to match the bandwidth of the RF pulse signal, constrains the NMR signal within the uniform region of the RF coil. This solves the signal distortion in the non-uniform region and the T1 tailing problem that exists in traditional T1-T2 measurements of long samples, greatly improving measurement accuracy.

[0074] For example, a long water film sample and a long shale sample are used as test samples to illustrate the above-mentioned spectral measurement method in nuclear magnetic resonance. The long water film sample and the long shale sample are used as test samples to cover the entire test area. The gradient field inside the shale sample is large and greatly affected by radio frequency non-uniformity. The spectral measurement method in nuclear magnetic resonance provided in the above embodiment is used to measure the long water film sample and the long shale sample.

[0075] Figure 5 shows the results of testing long water film samples using the conventional SR-CPMG sequence. Figure 6 shows the results of testing long water film samples using the method of this embodiment, i.e., SR-CPMG-G. In Figures 5 and 6, Intensity (au) represents the signal amplitude value. Figure 7 shows the results of testing long mudstone and shale using the conventional SR-CPMG sequence. Figure 8 shows the results of testing long mudstone and shale using the method of this embodiment, i.e., SR-CPMG-G. It can be seen that the spectral measurement method in nuclear magnetic resonance provided by this application embodiment solves the T1 tail problem of the conventional spectral measurement method in long samples, and can achieve high-precision and high-efficiency measurement of specific layers inside the sample.

[0076] This application also provides a spectrum measurement device for nuclear magnetic resonance imaging, which is used to implement the above embodiments and optional implementations, and will not be repeated as already described. As used below, the term "module" can be a combination of software and / or hardware that implements 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.

[0077] This application provides a spectrum measurement device for nuclear magnetic resonance (NMR). Figure 9 is a schematic diagram of the structure of a spectrum measurement device for NMR provided in this application. A target sample is placed in a uniform magnetic field, with the target direction of the target sample aligned with the uniform magnetic field. A gradient coil is disposed on the target sample. The device includes:

[0078] The linear gradient magnetic field application module 901 is used to apply a linear gradient magnetic field in the target direction of the target sample;

[0079] The uniform region determination module 902 is used to transmit an RF pulse signal to the target sample through the RF coil and determine the uniform region of the RF coil based on the bandwidth of the RF pulse signal.

[0080] The linear gradient magnetic field adjustment module 903 is used to adjust the gradient value of the linear gradient magnetic field during the reception of nuclear magnetic resonance echo signals, based on the target rotation angle, until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thereby obtaining the target linear gradient magnetic field.

[0081] The acquisition module 904 is used to obtain the target nuclear magnetic resonance echo signal based on the target's linear gradient magnetic field.

[0082] Inversion module 905 is used to invert the nuclear magnetic resonance echo signal of the target to obtain the T1-T2 spectrum.

[0083] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0084] In this embodiment, the spectrum measurement device in nuclear magnetic resonance is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0085] This application also provides a computer device having the spectrum measurement device shown in FIG9 above in nuclear magnetic resonance.

[0086] Please refer to Figure 10, which is a schematic diagram of the structure of a computer device provided in an optional embodiment of this application. As shown in Figure 10, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting the various components, including high-speed interfaces and low-speed interfaces. The various components communicate with each other using different buses and can be installed on a common motherboard or otherwise as needed. The processor can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information in a graphical user interface on an external input / output device (such as a display device coupled to the interface). In some optional embodiments, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 10 shows an example of a single processor 10.

[0087] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0088] The memory 20 stores instructions executable by at least one processor 10 to cause the at least one processor 10 to perform the method shown in the above embodiments.

[0089] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0090] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0091] The computer device also includes an input device 30 and an output device 40. The processor 10, memory 20, input device 30 and output device 40 can be connected via a bus or other means, as shown in Figure 10, which illustrates a connection via a bus.

[0092] This application also provides a computer-readable storage medium. The methods described in this application can be implemented in hardware or firmware, or implemented as recordable on a storage medium, or implemented as computer code downloaded over a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and subsequently stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; optionally, the storage medium may also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0093] A portion of this application can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to this application through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0094] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for spectral measurement in nuclear magnetic resonance, characterized in that, The method involves placing a target sample in a uniform magnetic field, wherein the target direction of the target sample is consistent with the uniform magnetic field, and a gradient coil is disposed on the target sample. A linear gradient magnetic field is applied in the target direction of the target sample; Radio frequency pulse signals are emitted to the target sample through a radio frequency coil, and the uniform region of the radio frequency coil is determined based on the bandwidth of the radio frequency pulse signals. During the reception of nuclear magnetic resonance echo signals, the gradient value of the linear gradient magnetic field is adjusted based on the target rotation angle until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thereby obtaining the target linear gradient magnetic field. Based on the target linear gradient magnetic field, the target nuclear magnetic resonance echo signal is obtained; The T1-T2 spectrum is obtained by inverting the nuclear magnetic resonance echo signal of the target.

2. The method according to claim 1, characterized in that, The gradient coil is composed of multiple current coils; the target direction includes the axial direction of the target sample.

3. The method according to claim 2, characterized in that, Applying a linear gradient magnetic field in the target direction of the target sample includes: The current direction of the current coil is adjusted so that a linear gradient magnetic field is applied in the axial direction of the target sample.

4. The method according to claim 3, characterized in that, Adjusting the gradient value of the linear gradient magnetic field includes: The gradient value of the linear gradient magnetic field is adjusted by adjusting the current in the current coil.

5. The method according to claim 4, characterized in that, The inversion of the target nuclear magnetic resonance echo signal to obtain the T1-T2 spectrum includes: Based on the target rotation angle, determine the T1-T2 data response model; Based on the target nuclear magnetic resonance echo signal, the T1-T2 data response model is inverted to obtain the T1-T2 spectrum.

6. The method according to claim 5, characterized in that, The expression for the T1-T2 data response model is: b ij =∑∑f(T1,T2)[1-exp(-TR / T1)]exp(-TE / T2); In the formula, T1 is the longitudinal relaxation time, T2 is the transverse relaxation time, TR is the waiting time, TE is the echo interval, and b is the number of seconds. ij This represents the signal amplitude at time j in the i-th echo train, given the TR waiting time and the TE echo interval.

7. The method according to any one of claims 1 to 6, characterized in that, The turning angle is 90 degrees.

8. A spectral measurement device for nuclear magnetic resonance, characterized in that, A target sample is placed in a uniform magnetic field, the target direction of the target sample is consistent with the uniform magnetic field, and a gradient coil is disposed on the target sample. The device includes: The linear gradient magnetic field application module is used to apply a linear gradient magnetic field in the target direction of the target sample. The uniform region determination module is used to transmit an RF pulse signal to the target sample through an RF coil, and determine the uniform region of the RF coil based on the bandwidth of the RF pulse signal. The linear gradient magnetic field adjustment module is used to adjust the gradient value of the linear gradient magnetic field during the reception of nuclear magnetic resonance echo signals, based on the target rotation angle, until the region of the nuclear magnetic resonance echo signal is constrained within the uniform region of the radio frequency coil, thereby obtaining the target linear gradient magnetic field. The acquisition module is used to obtain the target nuclear magnetic resonance echo signal based on the target linear gradient magnetic field; The inversion module is used to invert the target nuclear magnetic resonance echo signal to obtain the T1-T2 spectrum.

9. A computer device, characterized in that, include: A memory and a processor are communicatively connected, the memory storing computer instructions, and the processor executing the computer instructions to perform the spectral measurement method in nuclear magnetic resonance according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a computer to perform the spectral measurement method in nuclear magnetic resonance according to any one of claims 1 to 7.

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