WO2022095142A1 - Procédé et appareil de mesure de spectre bidimensionnel coefficient apparent de diffusion (adc)-t2, dispositif informatique et système de résonance magnétique à champ non uniforme - Google Patents

Procédé et appareil de mesure de spectre bidimensionnel coefficient apparent de diffusion (adc)-t2, dispositif informatique et système de résonance magnétique à champ non uniforme Download PDF

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WO2022095142A1
WO2022095142A1 PCT/CN2020/130626 CN2020130626W WO2022095142A1 WO 2022095142 A1 WO2022095142 A1 WO 2022095142A1 CN 2020130626 W CN2020130626 W CN 2020130626W WO 2022095142 A1 WO2022095142 A1 WO 2022095142A1
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echo signals
magnetic resonance
echo
formula
adc
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PCT/CN2020/130626
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Chinese (zh)
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张洁莹
潘子异
王伟谦
吴子岳
叶洋
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无锡鸣石峻致医疗科技有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/50—NMR imaging systems based on the determination of relaxation times, e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
    • G01R33/543—Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription

Definitions

  • the invention belongs to the technical field of nuclear magnetic resonance imaging, in particular to the technology of magnetic resonance spectrometer, and in particular to a method, device, computer equipment and non-uniform field magnetic resonance system for measuring the decay time constant of transverse magnetization vector.
  • Nuclear magnetic resonance technology is a technology that uses the nuclear magnetic resonance phenomenon of hydrogen protons to image or detect the composition and structure of substances.
  • Nuclei in the human body that contain a single number of protons, such as the nucleus of hydrogen, have protons that have spin motion.
  • the spin motions of charged nuclei are physically analogous to individual small magnets whose directional distributions are random in the absence of external conditions.
  • these small magnets will rearrange according to the magnetic field lines of the external magnetic field.
  • the nuclei are excited with radio frequency pulses of a specific frequency, so that the spins of these nuclei (small magnets) are deflected and resonance occurs. This is the phenomenon of nuclear magnetic resonance.
  • the excited atomic nuclei (resonant small magnets) will gradually return to the state before excitation.
  • electromagnetic wave signals will be released, and the magnetic resonance images will be obtained after receiving and processing the nuclear magnetic resonance signals through special equipment. Or the composition and structure information of a substance.
  • T2 also known as the spin-spin relaxation time T2
  • spin echo sequence Spin Echo, SE
  • T2 CPMG nuclear magnetic resonance sequence
  • the CPMG sequence is short and can avoid the accumulation of errors due to inaccurate 180-degree RF pulses (due to limited RF field uniformity).
  • signals are also typically acquired using CPMG sequences.
  • T2 in solids is much shorter than T2 in liquids.
  • the T2 in typical biological tissues is in the range of 20-150ms, and the free water T2 is much longer than the bound water T2. Clinically, the observed T2 prolongation at the lesion is interpreted as an increased free water ratio.
  • Molecules in matter all have a certain degree of diffusion motion, and its direction is random, which is called thermal motion or Brownian motion of molecules. If the diffusion motion of water molecules is not subject to any constraints, it can be called free diffusion. In the human body, water molecules such as cerebrospinal fluid and urine have relatively little restrictions on their diffusive movement and are considered free diffusion. In fact, the diffusion movement of water molecules in biological tissues will be restricted to different degrees due to the constraints of the surrounding medium, which is called restricted diffusion. The diffusion movement of water molecules in general tissues is restricted diffusion.
  • the apparent diffusion coefficient is a physical quantity that describes the ability of water molecules to diffuse in tissues. After the magnetic resonance signal is excited, the diffusion motion of water molecules in the direction of the gradient magnetic field will cause the attenuation of the magnetic resonance signal. The greater the change in the magnetic field, the greater the attenuation of the tissue signal. Therefore, the apparent diffusion coefficient of an object can be measured by nuclear magnetic resonance technology, thereby indirectly reflecting the microstructure characteristics and changes of the object.
  • the apparent diffusion coefficient (ADC, Apparent Diffusion Coefficient) is widely used as an important clinical diagnostic index. It is generally measured by Diffusion Weighted Imaging (DWI), such as spin echo-planar imaging (SE-EPI), that is, spin echo sequence (SE) for diffusion gradient coding , echo plane sequence (EPI) for signal readout.
  • DWI Diffusion Weighted Imaging
  • SE-EPI spin echo-planar imaging
  • SE-EPI spin echo sequence
  • EPI echo plane sequence
  • a non-uniform magnetic field magnetic resonance system also referred to as a non-uniform field magnetic resonance system
  • a similar diffusion-weighted imaging technique is introduced to measure the apparent diffusion coefficient of substances.
  • FIG. 1 is a spin echo-CPMG sequence (SE-CPMG), that is, diffusion gradient encoding is performed based on spin echo, and then an ultra-fast CPMG sequence is used for signal readout.
  • SE-CPMG spin echo-CPMG sequence
  • DSE-CPMG dual spin echo-CPMG sequence
  • STE-CPMG stimulated echo-CPMG sequence
  • the ADC measurement pulse sequence is composed of a diffusion gradient encoding module and a signal readout module.
  • the gradient magnetic field is very large, usually 2 to 3 orders of magnitude higher than that of a conventional magnetic resonance imaging system (Magnetic Resonance Imaging, MRI), and it is impossible to control the gradient magnetic field in the signal readout stage.
  • MRI Magnetic Resonance Imaging
  • DWI technology in the MRI system can control the gradient field reduction in the signal readout stage, while in a non-uniform magnet, the static gradient magnetic field G is often very large and is a constant uncontrollable gradient field
  • the gradient magnetic field In the signal readout stage it will still play the role of diffusion encoding, which will affect the accuracy of the apparent diffusion coefficient ADC measurement.
  • the purpose of the present invention is to provide a method, device, computer equipment, non-uniform field magnetic resonance system and computer-readable storage medium for measuring the decay time constant of the transverse magnetization vector.
  • the present invention provides a method for measuring the two-dimensional spectrum of ADC-T2, comprising:
  • the dimension of the ADC-T2 two-dimensional spectrum to be solved is set as p ⁇ q, and then the integral formula is converted into the following matrix formula:
  • s' vect(S'), S' represents S'(i,j), vect(S') represents the vector form of S'(i,j), and K represents the form of M ⁇ N ⁇ p ⁇ q
  • K represents the form of M ⁇ N ⁇ p ⁇ q
  • repmat() represents the function for copying and tiling the matrix
  • vect(repmat()) represents the vector form of repmat()
  • vect(S) represents the vector form of S(D, T 2 );
  • F(s) represents the function about the variable s
  • 2 represents the two-norm of the vector
  • ⁇ represents the constraint coefficient
  • the solution result of the ADC-T2 two-dimensional atlas is obtained by reduction.
  • the measurement method in a nuclear magnetic resonance system with a very uneven magnetic field or a very short echo time, it is possible to obtain echo signals from multiple CPMG sequences with different echo intervals.
  • the ADC coefficient and T2 value are fitted from the echo signal of the group, so that the ADC-T2 spectrum can be measured, so that the complex diffusion weighting sequence is no longer required, and the algorithm is simple and has low system requirements, which can reduce the need for spectrometers. Cost of hardware systems such as equipment, RF power amplifiers, and RF coils.
  • the measurement method also has the characteristics of stable algorithm, is not easily affected by flowing liquid, and is also applicable to substances with small T1/T2.
  • the measurement sequence is simple and fast, and no diffusion gradient coding module is required, which is easier to implement than the existing technology; for extremely inhomogeneous magnetic fields, or for nuclear magnetic resonance systems that cannot achieve extremely short echo times, this method can still measure ADCs -T2 spectrum; based on the aforementioned two advantages, the system hardware requirements can be reduced when designing a non-uniform field NMR system for ADC-T2 measurement, thereby reducing hardware costs; the ADC-T2 measurement method is not easily affected by flowing liquids , and it is also applicable to substances with smaller T1/T2; it can more accurately distinguish the water and fat components in the tested object.
  • the value of the diffusion sensitivity coefficient b is proportional to (t EE ) 3 , where t EE represents the time from the center point of the first 90° excitation pulse to the first time during the acquisition of a single set of echo signals The duration of the center point time of the echo signal.
  • the smallest fitting vector s greater than 0 is obtained by solving the optimization problem, including:
  • the matrix K is subjected to the following dimension reduction processing based on singular value decomposition:
  • U M ⁇ N ⁇ M ⁇ N represents the M ⁇ N ⁇ M ⁇ N order unitary matrix
  • the elements on the diagonal of ⁇ M ⁇ N ⁇ p ⁇ q are singular values
  • k′ represents dimensionality reduction
  • U M ⁇ N ⁇ k′ represents the first k′column matrix of U M ⁇ N ⁇ M ⁇ N ;
  • the vector s' is reduced from the M ⁇ N dimension to the k' dimension according to the following formula:
  • s' svd represents the vector when the vector s' is reduced from the M ⁇ N dimension to the k' dimension, is the transpose matrix of the matrix U M ⁇ N ⁇ k′ ;
  • the fitting vector s is obtained by solving:
  • the method before performing integral formula fitting on the multiple sets of echo signals, the method further includes performing the following preprocessing on the multiple sets of echo signals:
  • fast Fourier transform is performed on the multiple sets of echo signals to obtain frequency domain data, and then the low frequency part lower than the preset frequency threshold is retained and averaged to obtain the Multiple sets of echo signals with no difference in the dimension of the number of sampling points.
  • the method before performing integral formula fitting on the multiple sets of echo signals, the method further includes performing the following preprocessing on the multiple sets of echo signals:
  • averaging processing is performed on the multiple groups of echo signals to obtain multiple groups of echo signals with no difference in the dimension of average number of times.
  • the method before performing integral formula fitting on the multiple sets of echo signals, the method further includes performing the following preprocessing on the multiple sets of echo signals:
  • filtering processing based on singular value decomposition is performed on the plurality of sets of echo signals, so as to obtain a plurality of sets of echo signals without the influence of noise in the length dimension of the echo chain.
  • the present invention provides an ADC-T2 two-dimensional spectrum measurement device, comprising an echo signal acquisition module, an integral formula fitting module, a matrix formula conversion module, a problem solving conversion module, and a fitting vector that are sequentially connected in communication. Solving module and solving result restoration module;
  • the echo signal acquisition module is used to acquire multiple sets of echo signals acquired based on the CPMG nuclear magnetic resonance sequence, wherein the CPMG nuclear magnetic resonance sequence is used to perform diffusion gradient coding and read out each set of echo signals, and Different echo intervals are used for each group of echo signals;
  • the integral formula fitting module is used to fit the following integral formulas on the multiple sets of echo signals:
  • the matrix formula conversion module is used to set the dimension of the ADC-T2 two-dimensional atlas to be solved as p ⁇ q, and then convert the integral formula into the following matrix formula:
  • s' vect(S'), S' represents S'(i,j), vect(S') represents the vector form of S'(i,j), and K represents the form of M ⁇ N ⁇ p ⁇ q
  • K represents the form of M ⁇ N ⁇ p ⁇ q
  • repmat() represents the function for copying and tiling the matrix
  • vect(repmat()) represents the vector form of repmat()
  • vect(S) represents the vector form of S(D, T 2 );
  • the problem-solving conversion module is used to convert the problem of solving S(D, T 2 ) into a problem-solving optimization problem of the following formula according to the matrix formula:
  • F(s) represents the function about the variable s
  • 2 represents the two-norm of the vector
  • ⁇ represents the constraint coefficient
  • the fitting vector solving module is used to obtain the smallest fitting vector s greater than 0 by solving the optimization problem according to the solution;
  • the solution result restoration module is configured to restore the solution result of the ADC-T2 two-dimensional atlas according to the obtained fitting vector s.
  • the present invention provides a computer device, comprising a communicatively connected memory and a processor, wherein the memory is used to store a computer program, and the processor is used to read the computer program, and execute the first aspect Or any one of the first aspect may design the measurement method.
  • the present invention provides a non-uniform field magnetic resonance system, including a console, a nuclear magnetic resonance spectrometer, a magnet and a radio frequency subsystem;
  • the console connected to the nuclear magnetic resonance spectrometer in communication, is used to send instructions to the nuclear magnetic resonance spectrometer to control the parameter selection of the measurement sequence and the location of the region of interest, and to receive the data collected by the nuclear magnetic resonance spectrometer.
  • the magnetic resonance signal is obtained, and data processing is completed, wherein the data processing includes performing the measurement method according to the first aspect or any one of the possible designs of the first aspect;
  • the nuclear magnetic resonance spectrometer is connected to the radio frequency subsystem in communication, and is used for executing the instructions from the console, and transmits the radio frequency excitation signal of the measurement sequence and receives the magnetic resonance signal through the radio frequency subsystem;
  • the magnet is used to be arranged just above the object to be inspected and the signal transceiving component in the radio frequency subsystem;
  • the radio frequency subsystem is used for transmitting radio frequency excitation signals of the measurement sequence and receiving the magnetic resonance signals under the control of the nuclear magnetic resonance spectrometer.
  • the radio frequency subsystem includes a radio frequency power amplifier, a preamplifier, a transceiver switch and a radio frequency coil;
  • the signal input end of the radio frequency power amplifier is electrically connected to the signal output end of the nuclear magnetic resonance spectrometer, and the signal output end of the radio frequency power amplifier is electrically connected to the first switch end of the transceiving switch;
  • the signal input end of the preamplifier is electrically connected to the second switching end of the transceiving switch, and the signal output end of the preamplifier is electrically connected to the signal input end of the nuclear magnetic resonance spectrometer;
  • the controlled end of the transceiving switch is communicatively connected to the output end of the nuclear magnetic resonance spectrometer, and the switching common terminal of the transceiving switch is electrically connected to the radio frequency coil;
  • the radio frequency coil is used as a signal transceiver component of the radio frequency subsystem to transmit the radio frequency excitation signal to the object under inspection and receive the magnetic resonance signal from the object under inspection.
  • the present invention provides a computer-readable storage medium, where instructions are stored on the computer-readable storage medium, and when the instructions are executed on a computer, any one of the first aspect or the first aspect is executed. a possible design of the measurement method.
  • the present invention provides a computer program product comprising instructions that, when executed on a computer, cause the computer to perform the measurement as described in the first aspect or any one of the possible designs of the first aspect method.
  • FIG. 1 is an example diagram of the ADC measurement pulse sequence used in the non-uniform field magnetic resonance system in the prior art, wherein (a) SE-CPMG sequence is used; (b) DSE-CPMG sequence is used; (c) STE is used -CPMG sequence.
  • FIG. 2 is a schematic flowchart of the measurement method provided by the present invention.
  • FIG. 3 is an example diagram of the ADC-T2 measurement pulse sequence adopted in the non-uniform field magnetic resonance system provided by the present invention.
  • FIG. 5 is an example diagram of the ADC-T2 two-dimensional spectrum measured when the tested substances are 0.5mmol/L MnCl2 solution and peanut oil provided by the present invention.
  • FIG. 6 is a schematic structural diagram of the measuring device provided by the present invention.
  • FIG. 7 is a schematic structural diagram of a computer device provided by the present invention.
  • FIG. 8 is a schematic structural diagram of a non-uniform field magnetic resonance system provided by the present invention.
  • first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, a first element could be referred to as a second element, and similarly a second element could be referred to as a first element, without departing from the scope of example embodiments of this invention.
  • the measurement method of the ADC-T2 two-dimensional spectrum provided in the first aspect of this embodiment can be, but is not limited to, a method with an extremely uneven magnetic field or an extremely short echo time that cannot be achieved.
  • the console in the nuclear magnetic resonance system (which is connected to the nuclear magnetic resonance spectrometer in order to control the parameter selection of the measurement sequence and the positioning of the region of interest, and receives the magnetic resonance signals collected by the nuclear magnetic resonance spectrometer to complete the data processing) executes , in order to obtain an accurate ADC-T2 two-dimensional map.
  • the measurement method of the ADC-T2 two-dimensional spectrum includes but is not limited to the following steps S101-S106.
  • a typical ⁇ -2 ⁇ -2 ⁇ -2 ⁇ ... RF pulse sequence is used: the flip angle of the first excitation pulse is ⁇ , followed by several refocusing pulses, flipping The angle is 2 ⁇ ; the phase difference between the first excitation pulse and the first refocusing pulse is 90 degrees, the time interval between the first excitation pulse and the first refocusing pulse is ⁇ /2, and the first refocusing pulse to the first The time interval between the sampling windows is ⁇ /2; the time interval between the returning pulses is ⁇ , which is called the echo interval.
  • the constant gradient field is the natural gradient field of the magnet and does not require control.
  • N echo signals can be collected in one excitation (where N is a positive integer), it needs to be repeated many times in order to improve the signal-to-noise ratio by averaging the signals, and to obtain ADC-T2 two-dimensional It is necessary to collect multiple sets of echo signals by changing the echo interval ⁇ .
  • the multiple sets of echo signals acquired by collection can be represented by a 4-dimensional array S(m,n,a,q), wherein the first-dimensional array S(m) is based on different echoes interval, the length is a positive integer M, that is, the echo interval ⁇ corresponding to M different lengths; the second-dimensional array S(n) is based on different echo chain lengths, and the length is a positive integer N; the third-dimensional array S(a) is based on Different average times during repeated collection, the length is a positive integer A; the fourth dimension array S(q) is based on the different sampling points of the single read data, and the length is a positive integer Q.
  • the multiple sets of echo signals are a 4-dimensional array S(m,n,a,q), with too many dimensions and noise influence, which will increase the unnecessary integral calculation amount and bring about Therefore, it is necessary to perform dimensionality reduction and/or denoising processing first, that is, before performing integration formula fitting on the multiple sets of echo signals, it also includes but is not limited to performing the following methods on the multiple sets of echo signals ( A) to any one or any combination of preprocessing in (C): (A) in the dimension of the number of sampling points of the single readout data, fast Fourier transform is performed on the multiple groups of echo signals to obtain frequency domain data, Then keep the low-frequency part below the preset frequency threshold and perform averaging processing to obtain multiple sets of echo signals with no difference in the dimension of the number of sampling points; (B) in the dimension of the average number of times, for the multiple sets of echo signals The signals are averaged to obtain multiple sets of echo signals that are indistinguishable in the dimension of the average number of times; (C) in
  • the SVD algorithm is mainly used in feature decomposition, recommendation systems, and natural language processing in dimensionality reduction algorithms.
  • a linear transformation is decomposed into two linear transformations, one linear transformation represents rotation, and the other linear transformation represents stretching) filtering processing, so as to obtain no noise in the length dimension of the echo chain. of multiple sets of echo signals. Therefore, through the processing of the aforementioned methods (A) and (B), the dimension of the four-dimensional array S(m,n,a,q) can be reduced into a two-dimensional array S(m,n), which is beneficial to reduce subsequent calculations.
  • s' vect(S'), S' represents S'(i,j), vect(S') represents the vector form of S'(i,j), and K represents the form of M ⁇ N ⁇ p ⁇ q
  • K represents the form of M ⁇ N ⁇ p ⁇ q
  • repmat() represents the function for copying and tiling the matrix
  • vect(repmat()) represents the vector form of repmat()
  • vect(S) represents the vector form of S(D, T 2 ).
  • F(s) represents the function about the variable s
  • 2 represents the two-norm of the vector
  • ⁇ represents the constraint term coefficient
  • the specific process of solving the fitting vector s according to the solving optimization problem is an existing conventional solving method.
  • the dimensionality reduction solution may be performed but not limited to the following steps S501-S503.
  • U M ⁇ N ⁇ M ⁇ N represents the M ⁇ N ⁇ M ⁇ N order unitary matrix
  • the elements on the diagonal of ⁇ M ⁇ N ⁇ p ⁇ q are singular values
  • k′ represents dimensionality reduction
  • U M ⁇ N ⁇ k′ represents the first k′column matrix of U M ⁇ N ⁇ M ⁇ N ;
  • s' svd represents the vector when the vector s' is reduced from the M ⁇ N dimension to the k' dimension, is the transpose matrix of the matrix U M ⁇ N ⁇ k′ .
  • the solution result of the ADC-T2 two-dimensional map can be obtained by reduction in a conventional manner. That is to say, considering the strong gradient field existing in the non-uniform field, in the CPMG sequence, it can not only play the role of frequency coding, but also always have the role of diffusion coding. That is to say, if the echo interval of the CPMG sequence is larger, the signal will be lower.
  • the influence of the diffusion effect on the CPMG signal can be described by the following formula:
  • ⁇ represents the magnetic spin ratio of the nucleus
  • D' represents the ADC coefficient of the substance
  • G represents the magnitude of the gradient magnetic field
  • ⁇ represents the echo interval of the CPMG sequence.
  • the experimental results of this embodiment are specifically described below by taking the detection of 0.5 mmol/L MnCl 2 solution and peanut oil on a non-uniform field nuclear magnetic resonance system as an example.
  • Fig. 4 it can be seen that the signal attenuation of CPMG sequences with different echo intervals is different, which is due to the influence of molecular diffusion;
  • Fig. 5 it can be seen that the 0.5mmol/L MnCl 2 solution is a uniform peak on the ADC-T2 two-dimensional spectrum , while peanut oil showed double peaks in ADC-T2 two-dimensional spectrum, ADC coefficients and T2 values of the two substances were close to the theoretical values.
  • the peaks of MnCl 2 solution and peanut oil are clearly distinguished on the spectrum: the ADC of MnCl 2 solution is larger, while that of peanut oil has a smaller ADC.
  • a plurality of acquired echo-intervals with different echo intervals can be obtained.
  • ADC coefficients and T2 values are fitted from multiple sets of echo signals, so that the ADC-T2 spectrum can be measured, so that the complex diffusion weighting sequence is no longer needed, and the algorithm is simple and has system requirements.
  • the low cost can reduce the cost of hardware systems such as spectrometer equipment, RF power amplifiers and RF coils.
  • the measurement method also has the characteristics of stable algorithm, is not easily affected by flowing liquid, and is also applicable to substances with small T1/T2. That is, the measurement sequence is simple and fast, and no diffusion gradient coding module is required, which is easier to implement than the existing technology; for extremely inhomogeneous magnetic fields, or for nuclear magnetic resonance systems that cannot achieve extremely short echo times, this method can still measure ADCs -T2 spectrum; based on the aforementioned two advantages, the system hardware requirements can be reduced when designing a non-uniform field NMR system for ADC-T2 measurement, thereby reducing hardware costs; the ADC-T2 measurement method is not easily affected by flowing liquids , and it is also applicable to substances with smaller T1/T2; it can more accurately distinguish the water and fat components in the tested object.
  • a second aspect of this embodiment provides a virtual device for implementing the measurement method in the first aspect or any one of the possible designs of the first aspect, including an echo signal acquisition module that is sequentially communicatively connected, Integral formula fitting module, matrix formula conversion module, solving problem conversion module, fitting vector solving module and solving result restoration module;
  • the echo signal acquisition module is used to acquire multiple sets of echo signals acquired based on the CPMG nuclear magnetic resonance sequence, wherein the CPMG nuclear magnetic resonance sequence is used to perform diffusion gradient coding and read out each set of echo signals, and Different echo intervals are used for each group of echo signals;
  • the integral formula fitting module is used to fit the following integral formulas on the multiple sets of echo signals:
  • the matrix formula conversion module is used to set the dimension of the ADC-T2 two-dimensional atlas to be solved as p ⁇ q, and then convert the integral formula into the following matrix formula:
  • s' vect(S'), S' represents S'(i,j), vect(S') represents the vector form of S'(i,j), and K represents M ⁇ N ⁇ p ⁇ q
  • K represents M ⁇ N ⁇ p ⁇ q
  • repmat() represents the function for copying and tiling the matrix
  • vect(repmat()) represents the vector form of repmat()
  • vect(S) represents the vector form of S(D, T 2 );
  • the problem-solving conversion module is used to convert the problem of solving S(D, T 2 ) into a problem-solving optimization problem of the following formula according to the matrix formula:
  • F(s) represents the function about the variable s
  • 2 represents the two-norm of the vector
  • ⁇ represents the constraint coefficient
  • the fitting vector solving module is used to obtain the smallest fitting vector s greater than 0 by solving the optimization problem according to the solution;
  • the solution result restoration module is configured to restore the solution result of the ADC-T2 two-dimensional atlas according to the obtained fitting vector s.
  • a third aspect of this embodiment provides a computer device for executing the measurement method in the first aspect or any possible design of the first aspect, including a communicatively connected memory and a processor, wherein, The memory is used to store a computer program, and the processor is used to read the computer program, and execute the measurement method according to the first aspect or any one of the possible designs of the first aspect.
  • the memory may include, but is not limited to, random access memory (Random-Access Memory, RAM), read-only memory (Read-Only Memory, ROM), flash memory (Flash Memory), first-in first-out memory (First Input Memory) First Output, FIFO) and/or first-in-last-out memory (First Input Last Output, FILO), etc.; the processor may not be limited to using a microprocessor of the STM32F105 series.
  • the computer equipment may also include, but is not limited to, a power module, a display screen and other necessary components.
  • a fourth aspect of this embodiment provides a non-uniform field magnetic resonance system for performing the measurement method in the first aspect or any possible design of the first aspect, including a console, a nuclear magnetic resonance Spectrometers, magnets and RF subsystems;
  • the console connected to the nuclear magnetic resonance spectrometer in communication, is used to send instructions to the nuclear magnetic resonance spectrometer to control the parameter selection of the measurement sequence and the location of the region of interest, and to receive the data collected by the nuclear magnetic resonance spectrometer.
  • the magnetic resonance signal is obtained, and data processing is completed, wherein the data processing includes performing the measurement method according to the first aspect or any one of the possible designs of the first aspect;
  • the nuclear magnetic resonance spectrometer is connected to the radio frequency subsystem in communication, and is used for executing the instructions from the console, and transmits the radio frequency excitation signal of the measurement sequence and receives the magnetic resonance signal through the radio frequency subsystem;
  • the magnet is used to be arranged just above the object to be inspected and the signal transceiving component in the radio frequency subsystem;
  • the radio frequency subsystem is used for transmitting radio frequency excitation signals of the measurement sequence and receiving the magnetic resonance signals under the control of the nuclear magnetic resonance spectrometer.
  • the magnet is generally designed as a permanent magnet, such as a unilateral permanent magnet, so that there is still a highly non-uniform magnetic field in the region of interest.
  • the radio frequency subsystem includes a radio frequency power amplifier, a preamplifier, a transceiver switch and a radio frequency coil;
  • the signal input end of the radio frequency power amplifier is electrically connected to the signal output end of the nuclear magnetic resonance spectrometer, and the signal output end of the radio frequency power amplifier is electrically connected to the first switch end of the transceiving switch;
  • the signal input end of the preamplifier is electrically connected to the second switching end of the transceiving switch, and the signal output end of the preamplifier is electrically connected to the signal input end of the nuclear magnetic resonance spectrometer;
  • the controlled terminal of the transceiving switch is communicatively connected to the output terminal of the nuclear magnetic resonance spectrometer, and the switching common terminal of the transceiving switch is electrically connected to the radio frequency coil;
  • the radio frequency coil is used as a signal transceiver component of the radio frequency subsystem to transmit the radio frequency excitation signal to the object under inspection and receive the magnetic resonance signal from the object under inspection.
  • the radio frequency power amplifier is used to amplify the radio frequency excitation signal to be transmitted; the preamplifier is used to amplify the received magnetic resonance signal.
  • the transceiving switch is used for switching control, so that the radio frequency coil can transmit the radio frequency excitation signal and receive the magnetic resonance signal.
  • a fifth aspect of this embodiment provides a computer-readable storage medium that stores an instruction containing the measurement method in the first aspect or any possible design of the first aspect, that is, the computer-readable storage medium stores a memory on the computer-readable storage medium.
  • the instructions when executed on a computer, perform the measurement method as described in the first aspect or any one of the possible designs of the first aspect.
  • the computer-readable storage medium refers to a carrier for storing data, which may include, but is not limited to, a floppy disk, an optical disk, a hard disk, a flash memory, a USB flash drive, and/or a memory stick (Memory Stick), etc.
  • the computer may be a general-purpose computer, a special-purpose A computer, computer network, or other programmable device.
  • a sixth aspect of this embodiment provides a computer program product containing instructions, when the instructions are run on a computer, the computer is caused to perform the measurement described in the first aspect or any possible design of the first aspect method.
  • the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.

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  • Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un procédé et un appareil de mesure de spectre bidimensionnel coefficient apparent de diffusion (ADC)-T2, un dispositif informatique, et un système de résonance magnétique à champ non uniforme, qui peuvent être utilisés dans un système de résonance magnétique nucléaire ayant un champ magnétique extrêmement non uniforme ou lorsqu'un temps d'écho extrêmement court ne peut pas être obtenu. De multiples signaux d'écho collectés sur la base de séquences Carr-Purcell-Meiboom-Gill (CPMG) ayant différents intervalles d'écho sont acquis, et des coefficients ADC et des valeurs T2 sont ajustés à partir de multiples ensembles de signaux d'écho, de telle sorte qu'un spectre ADC-T2 peut être mesuré, sans utiliser de séquences de pondération de diffusion complexes, ce qui permet d'obtenir les avantages d'un algorithme simple et de faibles exigences de système, et de réduire le coût de systèmes matériels tels que des dispositifs spectromètres, des amplificateurs de puissance radiofréquence et des bobines radiofréquence. De plus, le procédé de mesure possède également les caractéristiques d'un algorithme stable, n'est pas aisément affecté par un liquide en circulation, et est également approprié pour des substances ayant de faibles valeurs T1/T2.
PCT/CN2020/130626 2020-11-09 2020-11-20 Procédé et appareil de mesure de spectre bidimensionnel coefficient apparent de diffusion (adc)-t2, dispositif informatique et système de résonance magnétique à champ non uniforme WO2022095142A1 (fr)

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