CN117949488A - Multidimensional nuclear magnetic resonance method for rapidly evaluating occurrence state of fluid in material - Google Patents
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Abstract
The invention relates to the technical field of fluid detection, and provides a multi-dimensional nuclear magnetic resonance method for rapidly evaluating the occurrence state of a fluid in a material, which comprises the following steps: performing data acquisition by using a nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data; performing data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result; performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result; the data acquisition by using the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data comprises the following steps: a T 1 information editing stage, a nuclear magnetic resonance relaxation imaging editing stage and a T 2 information measuring stage. The method can rapidly and nondestructively analyze the T 1、T2 value, the multidimensional distribution map and the imaging result of the measured sample, further characterize the internal structure of the sample, the occurrence condition of saturated fluid, the index of movable fluid and other important information, and has important application value in the analysis and characterization of the porous material sample.
Description
Technical Field
The invention relates to the technical field of fluid detection, in particular to a multidimensional nuclear magnetic resonance method for rapidly evaluating the occurrence state of a fluid in a material.
Background
The nuclear magnetic resonance technology is an advanced nondestructive detection means and has very wide application in a plurality of fields such as medicine, biology, energy, materials, agriculture and forestry, food, safety monitoring, chemical industry and the like.
In the research of porous materials, the specific quantification of fluid occurrence and movable fluid is an important research topic, wherein nuclear magnetic resonance technology can provide a lot of fine characterization information. Taking biomedicine as an example, the nuclear magnetic resonance T 1 imaging technology can provide the most direct and effective evidence for detecting pathological change mechanisms of biological tissues in situ due to the difference of longitudinal relaxation time of different tissue fluids, so that the method is a conventional nuclear magnetic resonance weighted imaging method. However, since the conventional method has a long detection time for the longitudinal relaxation time T 1, the next measurement can be performed after the hydrogen-containing proton spin system in the tissue reaches the thermal equilibrium, so that the whole measurement time for performing nuclear magnetic resonance on the measured sample by adopting the nuclear magnetic resonance T 1 imaging technology is long.
Meanwhile, the difference of the transverse relaxation time T 2 in the sample can also distinguish the components of the sample to a certain extent, and the types and the phase states of the fluid in the sample are identified, but the technical proposal of comprehensively utilizing the two-dimensional map T 1-T2 map to evaluate the occurrence state of the fluid in the material is less in the field.
In summary, in the prior art, the specific quantification of the fluid occurrence state and the movable fluid index by using the nuclear magnetic resonance technology has a series of defects of long overall measurement time, weak signal detection capability in small-scale pores, low measurement accuracy and the like, and it is needed to provide a nuclear magnetic resonance method capable of rapidly and accurately evaluating the fluid occurrence state in a material.
Disclosure of Invention
Based on the principle and the implementation process of the novel rapid multi-dimensional T 1-T2 imaging method for rapidly and accurately detecting the fluid occurrence state and the movable fluid index in the porous material sample, the method greatly improves the detection speed and the detection efficiency of the nuclear magnetic resonance imaging technology, and simultaneously, the measurement condition meets the condition of the existing main stream nuclear magnetic resonance equipment, so that a novel quantitative index is provided for the fluid occurrence state characterization.
Specifically, the invention adopts the following technical scheme:
In a first aspect, a multi-dimensional nuclear magnetic resonance method for rapidly evaluating fluid occurrence in a material, the method comprising:
performing data acquisition by using a nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
Performing data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result;
Performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result;
The data acquisition by using the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data comprises the following steps: a T 1 information editing stage, a nuclear magnetic resonance relaxation imaging editing stage and a T 2 information measuring stage.
In one possible implementation manner, the T 1 information editing stage includes:
S1.1: applying a series of 90-degree pulse clusters with gradually shortened time intervals to a hydrogen-containing proton spin system of a sample to be tested on a TRS channel, and eliminating a longitudinal macroscopic magnetization vector M 0;
s1.2: waiting an editing time Tw, and quantitatively and controllably recovering the longitudinal macroscopic magnetization vector M 0 from 0;
S1.3: a 90 ° pulse is applied to the hydrogen-containing proton spin system of the sample under test on the TRS channel, pulling the longitudinal macroscopic magnetization vector M 0 after recovery from the longitudinal direction coincident with the static magnetic field direction into the transverse plane.
In one possible implementation, the nuclear magnetic resonance relaxation imaging editing phase includes:
S1.4: after step S1.3, applying a phase encoding gradient pulse to the hydrogen-containing proton spin system of the tested sample on the GRD channel, wherein the width of the phase encoding gradient pulse is delta, and the highest height is g max;
S1.5: and opening an ACQ channel, and acquiring nuclear magnetic resonance signals to obtain nuclear magnetic resonance signals after gradient pulses.
In one possible implementation manner, the T 2 information measurement phase includes:
S1.6: after step S1.5, continuously applying 90-degree pulse to the hydrogen-containing proton spin system of the tested sample on the TRS channel, and collecting a solid echo signal after a certain time; the time length from the application of the 90-degree pulse in the step S1.3 to the acquisition of the solid echo signal in the step S1.6 is T E;
S1.7: setting a variable time interval (T E +i)/2, i as a first variable time;
S1.8: after waiting for a variable time interval (T E +i)/2, applying 90-degree pulse to a hydrogen-containing proton spin system of the tested sample on a TRS channel, and then after waiting for the variable time interval (T E +i)/2, collecting a solid echo signal formed by a transverse plane magnetization vector after refocusing in an ACQ channel;
s1.9: continuously adjusting the length of the first variable time i for N times according to an increasing rule, repeating the step S1.8N times, collecting solid echo signals formed by N refocused transverse plane magnetization vectors in an ACQ channel, and summing the solid echo signals collected in the step 1.6 to obtain N+1 solid echo signals;
S1.10: adjusting the height of the phase encoding gradient pulse in the step S1.4 from-g max to +g max, repeating the steps S1.4-S1.9 for accumulating S times, and realizing the data acquisition of transverse magnetization vectors under different gradient editing;
S1.11: and (3) adjusting the length of the editing time Tw in the step S1.2, repeating the steps S1.2-S1.10 for accumulating P times, realizing data acquisition under different longitudinal relaxation editing time, and finally acquiring nuclear magnetic resonance data.
In one possible implementation, the formula of the nmr data is:
M(kz,TW,n,TE,τ)＝∫∫F(z,T1,T2)·K1·K2·K3dzdT1dT2
kz＝γgmaxδ/2π
K1＝exp(i2πkzz)
Wherein k z is a wave function; t W is the edit time; n=0, 1,2,3, …, N is the number of adjustments of the variable time τ; t E is the time interval from the application of the 90 pulse in step S1.3 to the acquisition of the solid echo signal in step S1.6; τ is a variable time; f (z, T 1,T2) is the T 1-T2 imaging result; k 1、K2、K3 is a kernel function; z is a direction vector; t 1 is the longitudinal relaxation time; t 2 is the transverse relaxation time; gamma is the magnetic rotation ratio; g max is the highest height of the phase encoding gradient pulse; delta is the width of the phase encoding gradient pulse.
In one possible implementation manner, the data processing of the nmr data to obtain an nmr T 1-T2 imaging result includes:
The dimension of the nuclear magnetic resonance data is arranged, wherein the dimension of the nuclear magnetic resonance data is P (N+1), P is the change step number of the editing time T W, s is the change step number of the phase encoding gradient pulse height, and (N+1) is the number of the acquired solid echo signals;
performing Fourier transformation on the nuclear magnetic resonance data, and performing de-encoding on the data in an imaging dimension to obtain attenuation data of s nuclear magnetic resonance data;
And performing data fitting on the attenuation data of the s nuclear magnetic resonance data to obtain T 1-T2 distribution.
In one possible implementation manner, the data interpretation of the nuclear magnetic resonance T 1-T2 imaging result includes:
calculating the non-movable fluid and the movable fluid content index at each layer position of the tested sample;
continuously identifying and calculating the non-movable fluid, the movable fluid content and the movable fluid content index in the s layers along the axial direction of the tested sample, and obtaining the movable fluid index section and the movable fluid content index section of the whole sample along the imaging direction.
In a second aspect, a multi-dimensional nuclear magnetic resonance apparatus for rapidly evaluating fluid presence in a material, the apparatus comprising:
The data acquisition module is used for acquiring data by utilizing the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
The data processing module is used for carrying out data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result;
The data interpretation module is used for performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result;
The data acquisition by using the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data comprises the following steps: a T 1 information editing stage, a nuclear magnetic resonance relaxation imaging editing stage and a T 2 information measuring stage.
In one possible implementation, the data acquisition module includes:
A magnet system for providing a B 0 magnetic field;
A gradient system for providing a controllable magnetic field gradient g;
a radio frequency system for providing a B 1 magnetic field;
The B 0 magnetic field and the B 1 magnetic field are in a vertical relation in space, and the direction corresponding to the gradient magnetic field corresponding to the magnetic field gradient g is the direction of interest of the user.
In a third aspect, an electronic device, comprising:
A processor;
A memory;
And a computer program, wherein the computer program is stored in the memory, the computer program comprising instructions that, when executed by the processor, cause the electronic device to perform the method of any of the first aspects.
Compared with the prior art, the invention has the beneficial effects that: according to the technical scheme, from the perspective of quantum mechanics, saturation recovery treatment is adopted for a spin system and a magnetization vector in the preparation stage of a pulse sequence, so that the thermal balance state in the conventional scanning process is not needed, the overall measurement time is greatly shortened, and powerful conditions are provided for fluid identification in a porous material; meanwhile, corresponding pulses are reasonably arranged and optimized in a subsequent acquisition time period of the pulse sequence, so that radio frequency emission power consumption can be greatly reduced, and disturbance of a measurement technology on a sample is reduced; meanwhile, after the imaging editing segment, signal detection in an earlier time period is added, the signal detection capability in a small-scale pore is improved, the detection capability of a T 2 parameter is increased, and finally, the occurrence state and the movable fluid content of the fluid are quantitatively identified through the acquired T 1/T2 editing map and the acquired two-dimensional map T 1-T2 map at different positions. The data acquired by the technical scheme of the invention is different from the conventional method, and special attention is required in the actual data processing process, so the invention further provides a data processing method and an interpretation workflow of the fast nuclear magnetic resonance T 1-T2 imaging technology in a targeted manner.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a multi-dimensional nuclear magnetic resonance method for rapidly evaluating the occurrence state of a fluid in a material according to an embodiment of the present invention;
FIG. 2 is a pulse sequence diagram of a multi-dimensional nuclear magnetic resonance method for rapidly evaluating the occurrence state of a fluid in a material according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of T 1-T2 imaging at a certain horizon in a measured sample space obtained by a multi-dimensional nuclear magnetic resonance method for rapidly evaluating fluid occurrence states in materials according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a data interpretation flow and a movable fluid content profile of a multi-dimensional NMR method for rapidly evaluating a fluid occurrence state in a material according to an embodiment of the present invention;
FIG. 5 is a block diagram of a multi-dimensional NMR apparatus for rapidly evaluating fluid occurrence in a material according to an embodiment of the invention;
FIG. 6 is a schematic diagram showing the position relationship between magnetic fields generated by main units of a data acquisition module of a multi-dimensional nuclear magnetic resonance device for rapidly evaluating the occurrence state of a fluid in a material and a sample to be tested according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
For a better understanding of the technical solution of the present invention, the following detailed description of the embodiments of the present invention refers to the accompanying drawings.
It should be understood that the described embodiments are merely some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment provides a multi-dimensional nuclear magnetic resonance method for rapidly evaluating a fluid occurrence state in a material, and particularly please refer to a flow chart of the multi-dimensional nuclear magnetic resonance method for rapidly evaluating a fluid occurrence state in a material, which is shown in fig. 1, according to an embodiment of the present invention, the method comprises:
s1: performing data acquisition by using a nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
S2: performing data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result;
S3: and performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result.
Referring to fig. 2, a pulse sequence diagram of a multi-dimensional nuclear magnetic resonance method for rapidly evaluating a fluid occurrence state in a material according to an embodiment of the present invention is provided, and referring to fig. 2, the step S1 includes:
S1.1: a series of 90 pulse clusters with gradually shortened time intervals are applied to a hydrogen-containing proton spin system of a sample to be tested on a TRS channel, and a longitudinal macroscopic magnetization vector M 0 is eliminated.
It should be noted that the series of 90 ° pulse clusters with gradually decreasing time intervals includes at least 3 90 ° pulses, and the time intervals between adjacent 90 ° pulses decrease in sequence. The series of 90 pulse clusters with gradually shortened time intervals in this embodiment comprises 5 90 pulses, and the time intervals between adjacent 90 pulses are respectively denoted as (delta '-delta' -delta), and the four time intervals decrease in equal difference. Preferably, the longest time interval Δ' "is 5-7 times the 90 ° pulse width and the shortest time interval Δ is 90 ° pulse width.
S1.2: waiting an edit time Tw, and quantitatively and controllably recovering the longitudinal macroscopic magnetization vector M 0 from 0.
S1.3: a 90 ° pulse is applied to the hydrogen-containing proton spin system of the sample under test on the TRS channel, and the recovered longitudinal macroscopic magnetization vector M 0 is pulled from the longitudinal direction, which coincides with the direction of the static magnetic field, into the transverse plane to begin detection.
The above is the editing stage of the T 1 information, unlike the conventional technology in which a long waiting time is required for editing the T 1 information, the present invention completely eliminates the longitudinal macroscopic magnetization vector M 0 by using 90 DEG pulse clusters before the editing time Tw, and obtains the required editing magnetization vector at each editing time T W. By the technical scheme, waiting time is not needed, the execution efficiency of the pulse sequence is greatly improved, and efficient editing of T 1 information is realized.
S1.4: and applying a phase encoding gradient pulse to the hydrogen-containing proton spin system of the tested sample on the GRD channel, wherein the width of the phase encoding gradient pulse is delta, and the highest height is g max.
S1.5: and opening an ACQ channel, and acquiring nuclear magnetic resonance signals to obtain nuclear magnetic resonance signals after gradient pulses.
It is particularly noted that nuclear magnetic resonance signals after gradient pulses are critical for the characterization of ultrashort transverse relaxation times and microporosity due to the early acquisition times.
After the T 1 information is edited, the nuclear magnetic resonance relaxation imaging editing stage is carried out. The invention adopts phase encoding gradient pulse to carry out nuclear magnetic resonance relaxation imaging editing, and carries out phase encoding on each acquired echo. More importantly, the invention starts acquisition after the encoding time is pre-set from the time of T E to the time of the phase encoding gradient pulse in the prior art, thereby greatly improving the capability of imaging and editing short relaxation component information.
S1.6: after nuclear magnetic resonance signal acquisition is finished, continuously applying 90-degree pulse to a hydrogen-containing proton spin system of the sample to be detected on a TRS channel, and acquiring a solid echo signal after a certain time; the time interval from the application of the 90 pulse in step S1.3 to the acquisition of the solid echo signal in step S1.6 is T E. The certain time is preferably 100us, and the specific value depends on the tested sample.
S1.7: the variable time interval (T E +i)/2, i is set to the first variable time.
S1.8: after waiting for a variable time interval (T E +i)/2, a 90-degree pulse is applied to a hydrogen-containing proton spin system of the tested sample on a TRS channel, and after waiting for the variable time interval (T E +i)/2, a solid echo signal formed by the transverse plane magnetization vector after refocusing is acquired in an ACQ channel.
S1.9: continuously adjusting the length of the first variable time i for N times according to an increasing rule, repeating the step S1.8N times, collecting solid echo signals formed by N refocused transverse plane magnetization vectors in an ACQ channel, and summing the solid echo signals collected in the step 1.6 to obtain N+1 solid echo signals;
In this embodiment, the increment rule is preferably equal difference increment, and the steps S1.7-S1.9 specifically include:
S1.7: after waiting for a variable time interval (T E +τ)/2, applying 90-degree pulse to the hydrogen-containing proton spin system of the tested sample on the TRS channel, and then after waiting for the variable time interval (T E +τ)/2, collecting a second solid echo signal formed by the transverse plane magnetization vector after refocusing in the ACQ channel; the solid echo signal acquired in the step S1.6 is the first solid echo signal. τ is a variable time, τ is preferably 20us, the specific value depends on the sample being tested.
S1.8: and (3) after the variable time interval is regulated to be (T E +2τ)/2, repeating the step S1.7, applying 90-degree pulse to the hydrogen-containing proton spin system of the tested sample on the TRS channel, and then waiting for the variable time interval (T E +2τ)/2, and collecting a third solid echo signal formed by the transverse plane magnetization vector after the refocusing in the ACQ channel.
S1.9: continuously adjusting the variable time interval in an equal difference increasing mode until the variable time interval is (T E +Nτ)/2, repeating the steps S1.7 respectively, applying 90-degree pulse to the hydrogen-containing proton spin system of the tested sample on the TRS channel, waiting for the variable time interval (T E +Nτ)/2, and continuously obtaining N+1 solid echo signals formed by collecting the refocused transverse plane magnetization vectors in the ACQ channel, and ending all the measurement of the transverse magnetization vectors.
According to the invention, the T 2 measurement is carried out by using the solid echo signal string, so that the obtained information is more comprehensive in consideration of the fact that the information of the semi-solid phase component in the measured sample can be excited and detected; on the other hand, the radio frequency power consumption (namely energy) is reduced, and the thermal disturbance of nuclear magnetic resonance measurement on the measured sample is reduced. Meanwhile, the invention designs the echo interval of the solid echo signal string in the acquisition process to continuously change in an increasing way, so that the full-range effective acquisition of the short relaxation and long relaxation components can be still realized efficiently on the basis of further reducing the number of the used radio frequency pulses, and the detection efficiency is improved.
S1.10: adjusting the height of the phase encoding gradient pulse in the step S1.4 from-g max to +g max, repeating the steps S1.4-S1.9 for accumulating S times, and realizing the data acquisition of transverse magnetization vectors under different gradient editing;
S1.11: and (3) adjusting the length of the editing time Tw in the step S1.2, repeating the steps S1.2-S1.10 for accumulating P times, realizing data acquisition under different longitudinal relaxation editing time, and finally acquiring all original echo train signals required by the fast nuclear magnetic resonance T 1-T2 imaging, namely nuclear magnetic resonance data.
According to the correlation between the longitudinal relaxation time T 1, the transverse relaxation time T 2 and the spatial gradient coding of the measured sample, nuclear magnetic resonance data are obtained through the step S1, and the nuclear magnetic resonance data are expressed as follows:
M(kz,TW,n,TE,τ)＝∫∫F(z,T1,T2)·K1·K2·K3dzdT1dT2
kz＝γgmaxδ/2π
K1＝exp(i2πkzz)
Wherein k z is a wave function; t W is the edit time; n=0, 1,2,3, …, N is the number of adjustments of the variable time τ; t E is the time interval from the application of the 90 pulse in step S1.3 to the acquisition of the solid echo signal in step S1.6; τ is a variable time; f (z, T 1,T2) is the T 1-T2 imaging result; k 1、K2、K3 is a kernel function; z is a direction vector; t 1 is the longitudinal relaxation time; t 2 is the transverse relaxation time; gamma is the magnetic rotation ratio; g max is the highest height of the phase encoding gradient pulse; delta is the width of the phase encoding gradient pulse.
The step S2 includes:
S2.1: and (3) sorting the dimension of the nuclear magnetic resonance data, wherein the dimension of the nuclear magnetic resonance data is P x s (n+1), P is the number of steps of change of the editing time T W, s is the number of steps of change of the pulse height of the phase encoding gradient, and (n+1) is the number of acquired solid echo signals.
S2.2: and carrying out Fourier transformation on the nuclear magnetic resonance data, and de-compiling the data in an imaging dimension to obtain attenuation data of the s nuclear magnetic resonance data.
As is well known to those skilled in the art, the fourier transform is a linear transform, and is a non-pathological problem, so the specific details of step S2.2 will not be described in detail in this embodiment.
S2.3: and performing data fitting on the attenuation data of the s nuclear magnetic resonance data to obtain T 1-T2 distribution.
Further, the data fitting algorithm comprises single-index fitting, multi-index fitting and INVERSE LAPLACE inversion, and T 1-T2 distribution of the tested sample at different spatial positions is obtained.
Preferably, the data fitting is performed on the attenuation data of the nuclear magnetic resonance data using INVERSE LAPLACE inversion in this embodiment. Specifically, a regularization term is introduced to invert the attenuation data of the nuclear magnetic resonance data. In order to obtain a stable and accurate solution F, the embodiment adopts a Tikhonov regularization method, and introduces a smoothing term to solve the problem:
Wherein c is a regularization factor related to the signal-to-noise ratio of the acquired data; the term |·| represents the Frobenius norm of the matrix. The non-negative constraint solution F (T 1,T2) of each layer of the tested sample under the specific regularization factor c can be obtained through the non-negative constraint step. And continuously repeating the steps for s times, sequentially performing data fitting on the data of each point position of the tested sample, and finally obtaining the continuous (T 1-T2) distribution in the axial direction of the tested sample, namely the final T 1-T2 imaging result.
The step S3 includes:
S3.1: and calculating the non-movable fluid and the movable fluid content index at each layer position of the tested sample.
The method comprises the following steps: the imaging of T 1-T2 at a certain level in the measured sample space obtained in step S2 is shown in fig. 3. The non-movable fluid is in a fluid occurrence state due to different occurrence states of the hydrogen-containing fluid in the tested sample, but the relaxation characteristic of the non-movable fluid is expressed as short relaxation due to the strong adhesion relationship between the non-movable fluid and the solid skeleton; the relaxation time of the mobile fluid is relatively long, so that the fluid occurrence and the mobile fluid content can be rapidly identified without loss by using the parameter difference. Meanwhile, after the nuclear magnetic resonance data are subjected to data processing, a quadrilateral area is formed by using a T 1/T2 ratio and a T 2 cut-off value, and the quadrilateral area is used as a recognition judgment basis. By accumulating the display signals in the imaging of T 1-T2 at each layer of the measured sample, the non-movable fluid and the movable fluid content at each layer of the measured sample can be obtained, the non-movable fluid and the movable fluid content are respectively defined as Amp Non-movable fluid and Amp Movable fluid , and the movable fluid content index mi=amp Movable fluid /(Amp Movable fluid +Amp Non-movable fluid of the measured sample at each layer can be calculated.
S3.2: the movable fluid index section and the movable fluid content index section of the whole sample along the imaging direction can be obtained by continuously identifying and calculating the non-movable fluid content and the movable fluid content index in the s layers along the axial direction of the sample to be measured, and the data interpretation flow and the movable fluid content section schematic diagram of the embodiment of the invention are shown in fig. 4.
Conventional methods detect the mobile fluid content of a sample, either by requiring prolonged pyrolysis, evaporation, fractionation, etc., or by requiring grinding damage to the sample. Therefore, the conventional method has low working efficiency and poor detection precision, and the novel multidimensional nuclear magnetic resonance technology provided by the invention can effectively acquire the movable fluid content at the space imaging horizon by correlating the two characteristic relaxation times with the imaging editing fragments.
It should be specifically noted that, in the embodiment of the present invention, only one-dimensional z-axis imaging is taken as an example for illustration, and in the actual measurement process, the direction of the gradient magnetic field can be changed to accurately measure the movable fluid in any one-dimensional imaging or two-dimensional and high-dimensional space.
Corresponding to the embodiment, the invention also provides a multi-dimensional nuclear magnetic resonance device for rapidly evaluating the occurrence state of the fluid in the material.
Referring to fig. 5, a block diagram of a multi-dimensional nmr apparatus for rapidly evaluating a fluid occurrence in a material according to an embodiment of the present invention is shown. As shown in fig. 5, it mainly includes the following modules.
The data acquisition module 501 is configured to acquire data by using a nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
Specifically, the data acquisition module 501 includes a magnet system that can provide a B 0 magnetic field, a gradient system that can provide a controllable magnetic field gradient g, and a radio frequency system that can provide a B 1 magnetic field. Referring to fig. 6, a schematic diagram of a positional relationship between magnetic fields generated by main units of a data acquisition module of a multi-dimensional nuclear magnetic resonance device for rapidly evaluating a fluid occurrence state in a material and a sample to be measured is provided, and in combination with fig. 6, the magnetic fields B 0 and the magnetic fields B 1 are in a spatial perpendicular relationship, so as to construct a basic condition for generating a nuclear magnetic resonance phenomenon. The gradient magnetic field corresponding to the magnetic field gradient g is a necessary condition for spatial coding and imaging realization, and the direction corresponding to the magnetic field is the research direction of interest of the user. In this embodiment, the direction corresponding to the gradient magnetic field corresponding to the magnetic field gradient g is the z direction along the cylindrical axis of the sample to be measured.
The data processing module 502 is configured to perform data processing on the nmr data to obtain an nmr T 1-T2 imaging result;
And the data interpretation module 503 is used for performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result.
It should be noted that, for brevity, details of the embodiments of the present invention may be referred to the description of the embodiments of the method, and are not described herein again.
Referring to fig. 7, a schematic structural diagram of an electronic device according to an embodiment of the present invention is provided. As shown in fig. 7, the electronic device 700 may include: a processor 701, a memory 702 and a communication unit 703. The components may communicate via one or more buses, and it will be appreciated by those skilled in the art that the electronic device structure shown in the drawings is not limiting of the embodiments of the invention, as it may be a bus-like structure, a star-like structure, or include more or fewer components than shown, or may be a combination of certain components or a different arrangement of components.
Wherein the communication unit 703 is configured to establish a communication channel, so that the electronic device can communicate with other devices. It is a bridge for information exchange between devices, supporting wireless and wired communication, one of the key components.
The processor 701 is a control center for the electronic device, connects various parts of the entire electronic device using various interfaces and lines, and performs various functions of the electronic device and/or processes data by running or executing software programs and/or modules stored in the memory 702, and invoking data stored in the memory. The processor may be comprised of integrated circuits (INTEGRATED CIRCUIT, ICs), such as a single packaged IC, or may be comprised of packaged ICs that connect multiple identical or different functions. For example, the processor 701 may include only a central processing unit (central processing unit, CPU). In the embodiment of the invention, the CPU can be a single operation core or can comprise multiple operation cores.
The memory 702 for storing the execution instructions of the processor 701, the memory 702 may be implemented by any type of volatile or non-volatile memory device or combination thereof, such as Static Random Access Memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk, or optical disk.
The execution of the instructions in memory 702, when executed by processor 701, enables electronic device 700 to perform some or all of the steps of the method embodiments described above.
Corresponding to the above embodiment, the embodiment of the present invention further provides a computer readable storage medium, where the computer readable storage medium may store a program, where when the program runs, the device where the computer readable storage medium is located may be controlled to execute some or all of the steps in the above method embodiment. In particular, the computer readable storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), a random access memory (random access memory, RAM), or the like.
Corresponding to the above embodiments, the present invention also provides a computer program product comprising executable instructions which, when executed on a computer, cause the computer to perform some or all of the steps of the above method embodiments.
In the embodiments of the present invention, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relation of association objects, and indicates that there may be three kinds of relations, for example, a and/or B, and may indicate that a alone exists, a and B together, and B alone exists. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of the following" and the like means any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or plural.
Those of ordinary skill in the art will appreciate that the various elements and algorithm steps described in the embodiments disclosed herein can be implemented as a combination of electronic hardware, computer software, and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described systems, apparatuses and units may refer to corresponding procedures in the foregoing method embodiments, and are not repeated herein.
In several embodiments provided by the present invention, any of the functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a read-only memory (ROM), a random access memory (random access memory RAM), a magnetic disk, or an optical disk, etc., which can store program codes.
The foregoing is merely exemplary embodiments of the present invention, and any person skilled in the art may easily conceive of changes or substitutions within the technical scope of the present invention, which should be covered by the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A multi-dimensional nuclear magnetic resonance method for rapidly evaluating the presence of a fluid in a material, the method comprising:
performing data acquisition by using a nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
Performing data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result;
Performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result;
The data acquisition by using the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data comprises the following steps: a T 1 information editing stage, a nuclear magnetic resonance relaxation imaging editing stage and a T 2 information measuring stage.
2. The method of claim 1, wherein the step of editing the T 1 information comprises:
S1.1: applying a series of 90-degree pulse clusters with gradually shortened time intervals to a hydrogen-containing proton spin system of a sample to be tested on a TRS channel, and eliminating a longitudinal macroscopic magnetization vector M 0;
s1.2: waiting an editing time Tw, and quantitatively and controllably recovering the longitudinal macroscopic magnetization vector M 0 from 0;
S1.3: a 90 ° pulse is applied to the hydrogen-containing proton spin system of the sample under test on the TRS channel, pulling the longitudinal macroscopic magnetization vector M 0 after recovery from the longitudinal direction coincident with the static magnetic field direction into the transverse plane.
3. A multi-dimensional nuclear magnetic resonance method for rapidly assessing a fluid occurrence in a material according to claim 2, wherein the nuclear magnetic resonance relaxation imaging editing phase comprises:
S1.4: after step S1.3, applying a phase encoding gradient pulse to the hydrogen-containing proton spin system of the tested sample on the GRD channel, wherein the width of the phase encoding gradient pulse is delta, and the highest height is g max;
S1.5: and opening an ACQ channel, and acquiring nuclear magnetic resonance signals to obtain nuclear magnetic resonance signals after gradient pulses.
4. A multi-dimensional nuclear magnetic resonance method for rapidly assessing a fluid occurrence in a material according to claim 3, wherein the T 2 information measurement phase includes:
S1.6: after step S1.5, continuously applying 90-degree pulse to the hydrogen-containing proton spin system of the tested sample on the TRS channel, and collecting a solid echo signal after a certain time; the time length from the application of the 90-degree pulse in the step S1.3 to the acquisition of the solid echo signal in the step S1.6 is T E;
S1.7: setting a variable time interval (T E +i)/2, i as a first variable time;
S1.8: after waiting for a variable time interval (T E +i)/2, applying 90-degree pulse to a hydrogen-containing proton spin system of the tested sample on a TRS channel, and then after waiting for the variable time interval (T E +i)/2, collecting a solid echo signal formed by a transverse plane magnetization vector after refocusing in an ACQ channel;
s1.9: continuously adjusting the length of the first variable time i for N times according to an increasing rule, repeating the step S1.8N times, collecting solid echo signals formed by N refocused transverse plane magnetization vectors in an ACQ channel, and summing the solid echo signals collected in the step 1.6 to obtain N+1 solid echo signals;
S1.10: adjusting the height of the phase encoding gradient pulse in the step S1.4 from-g max to +g max, repeating the steps S1.4-S1.9 for accumulating S times, and realizing the data acquisition of transverse magnetization vectors under different gradient editing;
S1.11: and (3) adjusting the length of the editing time Tw in the step S1.2, repeating the steps S1.2-S1.10 for accumulating P times, realizing data acquisition under different longitudinal relaxation editing time, and finally acquiring nuclear magnetic resonance data.
5. The method of claim 1, wherein the formula of the nmr data is:
M(kz,TW,n,TE,τ)＝∫∫F(z,T1,T2)·K1·K2·K3dzdT1dT2
kz＝γgmaxδ/2π
K1＝exp(i2πkZz)
Wherein k Z is a wave function; t W is the edit time; n=0, 1,2,3, …, N is the number of adjustments of the variable time τ; t E is the time interval from the application of the 90 pulse in step S1.3 to the acquisition of the solid echo signal in step S1.6; τ is a variable time; f (z, T 1,T2) is the T 1-T2 imaging result; k 1、K2、K3 is a kernel function; z is a direction vector; t 1 is the longitudinal relaxation time; t 2 is the transverse relaxation time; gamma is the magnetic rotation ratio; g max is the highest height of the phase encoding gradient pulse; delta is the width of the phase encoding gradient pulse.
6. The method for rapidly evaluating the presence of a fluid in a material according to claim 1, wherein said processing said nmr data to obtain nmr T 1-T2 imaging results comprises:
The dimension of the nuclear magnetic resonance data is arranged, wherein the dimension of the nuclear magnetic resonance data is P (N+1), P is the change step number of the editing time T W, s is the change step number of the phase encoding gradient pulse height, and (N+1) is the number of the acquired solid echo signals;
performing Fourier transformation on the nuclear magnetic resonance data, and performing de-encoding on the data in an imaging dimension to obtain attenuation data of s nuclear magnetic resonance data;
And performing data fitting on the attenuation data of the s nuclear magnetic resonance data to obtain T 1-T2 distribution.
7. The method of claim 1, wherein the data interpretation of the results of the nuclear magnetic resonance T 1-T2 imaging comprises:
calculating the non-movable fluid and the movable fluid content index at each layer position of the tested sample;
continuously identifying and calculating the non-movable fluid, the movable fluid content and the movable fluid content index in the s layers along the axial direction of the tested sample, and obtaining the movable fluid index section and the movable fluid content index section of the whole sample along the imaging direction.
8. A multi-dimensional nuclear magnetic resonance apparatus for rapidly evaluating the presence of a fluid in a material, the apparatus comprising:
The data acquisition module is used for acquiring data by utilizing the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data;
The data processing module is used for carrying out data processing on the nuclear magnetic resonance data to obtain a nuclear magnetic resonance T 1-T2 imaging result;
The data interpretation module is used for performing data interpretation on the nuclear magnetic resonance T 1-T2 imaging result;
The data acquisition by using the nuclear magnetic resonance pulse sequence to obtain nuclear magnetic resonance data comprises the following steps: a T 1 information editing stage, a nuclear magnetic resonance relaxation imaging editing stage and a T 2 information measuring stage.
9. The apparatus of claim 8, wherein the data acquisition module comprises:
A magnet system for providing a B 0 magnetic field;
A gradient system for providing a controllable magnetic field gradient g;
a radio frequency system for providing a B 1 magnetic field;
The B 0 magnetic field and the B 1 magnetic field are in a vertical relation in space, and the direction corresponding to the gradient magnetic field corresponding to the magnetic field gradient g is the direction of interest of the user.
10. An electronic device, comprising:
A processor;
A memory;
And a computer program, wherein the computer program is stored in the memory, the computer program comprising instructions that, when executed by the processor, cause the electronic device to perform the method of any one of claims 1 to 7.
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