Methionine molecule targeted filtering method for multi-spin quantum state signal screening based on nuclear magnetic resonance and application

Abstract

The invention discloses a methionine molecule targeted filtering method for multi-spin quantum state signal screening based on nuclear magnetic resonance. According to the method, quantum state evolution of a methionine molecule nuclear spin coupling system is accurately controlled by optimizing control pulses, and efficient and selective observation of methionine molecule methylene magnetic resonance signals is achieved by preparing and converting multi-spin quantum states of methionine molecules. According to the method, the problem of overlapping of spectrum peak signals of different molecules in a magnetic resonance living body wave spectrum can be solved, and high-efficiency selective detection of magnetic resonance signals of methionine molecules in a target sample can be realized in a non-invasive mode. Meanwhile, the method has the advantages of being easy to operate and rapid in aging. The technology not only can be used for high-sensitivity detection of methionine molecules in biological in-vitro tissue samples with complex components, but also can be used for rapid detection of content and distribution of methionine molecules in biological in-vivo tissues, and has important application prospects in the fields of biological medicine and medicine.

Description

Technical Field

[0001] This invention belongs to the field of magnetic resonance technology, specifically relating to a targeted filtering method for methionine molecules based on multi-spin quantum state signal screening using nuclear magnetic resonance, and its application, to realize the nuclear spin evolution and detection of different groups in methionine molecules. Background Technology

[0002] Methionine is an essential amino acid for the human body and an important component of the single-carbon cycle, participating in various metabolic processes such as DNA methylation, glutathione synthesis, and folic acid metabolism coupling. Furthermore, tumor cell proliferation exhibits high uptake and dependence on methionine, and higher concentrations of methionine molecules are typically found within tumors. Methionine level detection may become a new standard for tumor detection, providing guidance for clinical differentiation of recurrence or necrosis in radiotherapy areas and for distinguishing between benign and malignant tumors. Conventional tumor detection methods include magnetic resonance imaging (MRI), biopsy, and positron emission tomography (PET), but these techniques all have certain limitations. Magnetic resonance spectroscopy, as a non-invasive in-situ detection technique, avoids secondary harm to patients and accurately identifies various amino acid and macromolecular signals. Methionine signal detection based on nuclear magnetic resonance technology holds promise as a new standard for tumor identification. However, magnetic resonance spectroscopy also presents challenges. The hydrogen atom signal typically has a relative chemical shift range of less than 20 ppm, and the diverse types of human metabolites and macromolecular signals often lead to severe proton signal overlap and uneven hydrogen spectrum baselines, hindering quantitative analysis of metabolites. Furthermore, the spin system of methionine exists in a relatively complex chemical environment, leading to increasingly severe proton signal splitting and overlap. Therefore, signal filtering for methionine molecules is particularly necessary. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention aims to provide a methionine molecule targeting filtering method based on multi-spin quantum state signal screening using nuclear magnetic resonance (NMR). To achieve efficient detection of the nuclear spin evolution of different groups within the methionine molecule, an optimized control pulse file composed of multiple sub-pulses with different amplitudes and phases is first calculated using the GRAPE numerical method. This optimized control pulse file controls the evolution of specific target groups towards the target spin state. Combined with gradient pulse module filtering, the quality of the NMR spectrum for methionine molecule targeting is significantly improved. The method proposed in this invention, based on NMR technology, can achieve highly efficient, sensitive, and selective in-situ identification and detection of methionine molecules with complex coupling networks and multi-spin systems in target samples in a non-invasive manner. Furthermore, this invention offers advantages such as simple operation, rapid response, and painless and non-invasive nature. It is universally applicable even for the detection of methionine molecules in complex biological ex vivo tissue samples, and has significant application prospects in the biomedical and medical fields, representing a novel magnetic resonance filtering technology. The specific technical solution is as follows:

[0004] This invention provides a method for preparing and detecting multi-spin quantum states of different groups in methionine molecules. By combining optimized control pulse and gradient pulse design, the method can specifically detect methionine molecule signals in test samples. The method includes the following core steps:

[0005] Step i: The six-spin system of methionine molecule, consisting of two methylene groups, one methine group and one methyl group, is transformed from thermal equilibrium state to multi-spin Zeeman order quantum state by the first optimized control pulse OCI.

[0006] Step ii: Since the Zeeman order quantum state is free from the influence of gradient pulses, the nuclear spin signal in the single quantum state in the system can be eliminated by applying gradient pulses, while the multi-spin Zeeman order quantum state of the target system will be fully preserved;

[0007] Step iii: The multi-spin Zeeman order quantum state is converted into an observable state by the second optimized control pulse OCII, and the magnetic resonance signal is acquired.

[0008] The targeted filtering method described in this invention controls the six-spin system of the methionine molecule, transforming it from a thermal equilibrium state to a multi-spin Zeeman order quantum state, thereby enabling signal recognition and detection of different groups within the methionine molecule.

[0009] In this invention, the groups used for selective observation are all derived from methionine molecules. Methionine molecules possess two sets of methylene groups (the hydrogen nuclei on the methylene groups are denoted as H2, H3, H4, and H5, respectively, see...). Figure 2 ) group, a group of methines (denoted as H1, see Figure 2) and a group of methyl groups (the hydrogen nuclei on the methyl group are all equivalent hydrogen atoms, collectively denoted as H6, see Figure 2 ).

[0010] In step i, the first optimized control pulse OCI is obtained through the GRAPE numerical calculation method. The first optimized control pulse contains one or more sub-pulses with different amplitudes and phases. The GRAPE numerical calculation method is used to calculate a numerical pulse with an efficiency higher than 98%. This process utilizes the SIMPSON numerical pulse calculation platform. A pulse calculation program is written, the spin parameters of methionine are input, the initial and final states of the spin system are determined, and the program is run. The built-in GRAPE algorithm iterates step by step, gradually changing the amplitude and phase of the numerical pulse, finally obtaining an optimized pulse with high conversion efficiency. The first optimized control pulse OCI controls the two sets of methylene groups in the methionine molecule (the hydrogen nuclei on the methylene groups are denoted as H2, H3, H4, and H5, respectively, see...). Figure 2 ), a group of methines, and a group of methyl groups (the hydrogen nuclei on the methyl groups are all equivalent hydrogens, uniformly denoted as H6, see Figure 2 The spin evolution of a nuclear spin system transforms the entire spin system from a thermal equilibrium state to a multi-spin quantum state. The initial state operator of the entire spin system is denoted as ρ(0) = I. 1z +I 2z +I 3z +I 4z +I 5z +I 6z The first optimized control pulse OCI will cause it to move towards the target three-spin Zeeman sequence ρ(1)=I 1x +I 2x +I 3x +4I 2z I 3z I 4z +4I 2z I 3z I 5z +I 6x During the transfer, in which two hydrogen nuclei in one group of methylene groups are prepared into a three-spin Zeeman order, and the remaining four spins are prepared into a single quantum state; and / or, the first optimized control pulse OCI for filtering the H6 signal of the methyl peak will control the initial state operator ρ(0) = I of the methyl group. 1z +I 2z +I 3z +I 4z +I 5z +I 6z Towards the target state ρ(1)'=I 1x +I 2x +I 3x +I 4x +I 5x +I 6z Through evolution, the methyl group is transformed into a single quantum state.

[0011] In step ii, by adjusting the power, time, and position of the pulsed gradient field, the suppression of non-target signals and the selective observation of the magnetic resonance signal of methionine molecules are achieved and optimized. Gradient pulses are used to eliminate or suppress signals other than those of the target spin system. The multi-spin Zeeman order of the target spin system will be free from gradient field interference, achieving selective preservation of the multi-spin quantum states of the target spin system. Specifically, during pulse sequence tuning, a suitable gradient pulse width is selected, and the intensity, pulse width, or number of applications of the gradient field are appropriately adjusted. After the first gradient pulse is applied, sampling is performed. If an NMR signal can still be detected, it indicates that the gradient pulse intensity is insufficient and the gradient field intensity needs to be increased. When no hydrogen nucleus signal is found in the sampling results, it indicates that the gradient intensity is appropriate. The intensity and time of the second gradient pulse can be set to be comparable to the first gradient. Preferably, the intensity of the two gradient pulses should be slightly different to avoid signal re-convergence after dephasing.

[0012] In step iii, the second optimized control pulse OCII, obtained through the GRAPE numerical calculation method, controls the entire spin system of the methylene, methine, and methyl groups of the methionine molecule to transition from the Zeeman order quantum state to the observable state. The pulse calculation process is similar to that of the first optimized pulse calculation process: determining the initial and final state forms and spin parameters, setting the amplitude and phase of the initial pulse, running the optimization program, and continuously improving the pulse transfer efficiency through numerical iteration to finally obtain a numerical pulse with the highest possible efficiency. This ensures that the second optimized control pulse OCII designed for the methylene groups H4 and H5 controls the methylene spin system to transition from the nuclear spin three-spin quantum state ρ(1)=I. 1x +I 2x +I 3x +4I 2z I 3z I 4z +4I 2z I 3z I 5z +I 6x To the observable state ρ(2)=I 4x +I 5x Transfer; the second optimized control pulse OCII controls the methionine methine (the hydrogen nucleus on the methine is denoted as H1, see...) Figure 2 ) and one group of methylene groups (H2, H3, see Figure 2 The operator rotates to the Z-axis direction, and since it cannot be detected by NMR instruments, it will ultimately achieve signal filtering except for the target spin system; and / or, the second optimized control pulse designed for the methyl peak H6 will control the methyl peak from the single quantum state ρ(1)'=I 1x +I 2x +I 3x +I 4x +I5x +I 6z Towards the observable state ρ(2)'=I 6x Evolution. It is worth noting that, due to the different chemical shift differences and coupling parameters of the two pairs of methylene groups, the pulses designed for methylene H4 and H5 can achieve the transition between the initial and final states well, but they do not transfer methylene H2 and H3 to the same state. Instead, they suppress the methylene H2 and H3 signals.

[0013] Finally, the two sets of signals are acquired by magnetic resonance imaging to obtain the magnetic resonance signal of a specific methionine group.

[0014] In addition, the present invention may also include the following basic steps: (1) locating the test area of ​​the water film sample or ex vivo tissue using conventional magnetic resonance imaging (MRI) technology. (2) If necessary, acquiring the spectrum of the test area using conventional nuclear magnetic resonance spectroscopy (NMR), magnetic resonance imaging (MRI), and magnetic resonance spectroscopy (MRS) technology. These are well-known in the field and therefore will not be specifically described.

[0015] The nuclear magnetic resonance pulse sequences included in this invention include multi-spin quantum state preparation and detection sequences for methylene H4, H5 spin pairs and / or methyl H6 spin systems in spectrometers, as well as multi-spin quantum state preparation and detection sequences for methylene H4, H5 spin pairs and / or methyl H6 spin systems in imaging spectrometers.

[0016] The pulse sequence designed in this invention typically includes a multi-spin quantum state preparation module and a multi-spin quantum state transfer module. Figure 4 The pulse amplitude and phase of the first optimized control pulse OCI for preparing methionine molecules with multispin quantum states of the methylene H4 and H5 spin pairs are shown as curves of pulse duration. Figure 4 (a) is the pulse amplitude curve of the first optimized control pulse OCI. Figure 4 (b) is the phase curve of the first optimized control pulse OCI. The first optimized control pulse OCI transforms the methionine methylene H4, H5 spin pair from thermal equilibrium to a multi-spin quantum state.

[0017] Figure 5 The curves showing the pulse amplitude and phase versus pulse time of the first optimized control pulse OCI for preparing the methionine methyl H6 spin system as a single-spin quantum state in this invention are shown. Figure 5 (a) is the pulse amplitude curve of the first optimized control pulse OCI. Figure 5 (b) shows the phase curve of the first optimized control pulse OCI. The methionine methyl H6 spin system modulated by the first optimized control pulse OCI will transition from the thermal equilibrium state to the single quantum state.

[0018] Figure 6 This invention provides pulse sequences for the preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and / or methyl H6 spin systems in spectroscopic instruments.

[0019] Figure 6 In this process, the pulse sequence includes a water-pressurized pulse (WET), a first optimized control pulse (OCI), a gradient pulse (g), and a second optimized control pulse (OCII). The water-pressurized pulse (WET) typically suppresses water signals through the T1 effect. The first optimized control pulse (OCI) acts on a specific nuclear spin, causing it to evolve from a thermal equilibrium state towards a target multi-spin quantum state. The gradient pulse (g) applies a gradient field to eliminate non-target signals generated by the secondary excitation of the first optimized control pulse. The second optimized control pulse (OCII) transfers a specific group from a multi-spin quantum state to an observable state, which can be detected by an NMR instrument.

[0020] The process of the above pulse sequence can be described as follows: First, a water-suppressing pulse (WET) is applied to suppress the water signal and enhance the detection of proton signals other than the water peak. The first optimized control pulse (OCI) converts the entire six-spin system of methionine and / or the methyl H6 nuclear spin from a thermal equilibrium state to a multi-spin quantum state. After applying the first optimized control pulse (OCI), a gradient pulse (g) is applied. The gradient pulse (g) eliminates non-target signals generated by the secondary excitation of the first optimized control pulse, retaining the multi-spin quantum state signal unaffected by the gradient field. The specific pulse width and intensity of the gradient pulse (g) will be optimized based on experimental conditions. After applying the gradient field (g), a second optimized control pulse (OCII) is applied, simultaneously converting the nuclear spin singlet state prepared by the first optimized control pulse (OCI) into an observable state. Finally, magnetic resonance signal acquisition is performed to obtain the magnetic resonance signals of the methylene H4 and H5 spin pairs and / or the methyl H6 spin system of the methionine molecule.

[0021] Figure 7 This invention provides pulse sequences for the preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and / or methyl H6 spin systems in imaging spectrometers.

[0022] Figure 7 The pulse sequence includes a saturated water pressure module (WET), a first optimized control pulse module (OCI'), a second optimized control pulse module (OCII'), a first gradient pulse (g1), a second gradient pulse (g2), and a single-line voxel point-resolved spectroscopy (PRESS) module. First, a conventional T1 weighting module is used to locate the sample position in the magnetic field, and then the sample region to be measured is selected before applying the pulse. Figure 7The pulse sequence includes: a saturated water pressure module (WET) for suppressing water signals; a first optimized control pulse module (OCI') acting on a specific nuclear spin to evolve it from a thermal equilibrium state to a target multi-spin quantum state; a first gradient pulse (g1) applying a gradient field to eliminate non-target signals generated by the secondary excitation of the first optimized control pulse module (OCI'); a second optimized control pulse module (OCII') transitioning a specific group from a multi-spin quantum state to a thermal equilibrium state; a second gradient pulse (g2) applying a gradient field to eliminate non-target signals generated by the secondary excitation of the second optimized control pulse module (OCII'); and a single-line voxel point-resolved spectroscopy (PRESS) module used for spatial positioning and signal excitation, ultimately achieving NMR signal detection.

[0023] The working process of the above pulse sequence can be described as follows: The saturated water suppression module WET suppresses the water signal and enhances the detection of proton signals other than the water peak. The first optimized control pulse module OCI' can convert the entire six-spin system of the methionine molecule and / or the nuclear spin of methyl H6 from the thermal equilibrium state to a multi-spin quantum state. After applying the first optimized control pulse module OCI', a first gradient pulse g1 is applied. The first gradient pulse g1 will eliminate the non-target signals generated by the secondary excitation of the first optimized control pulse module, and retain the multi-spin quantum state signal that is not disturbed by the gradient field. The specific pulse width and intensity of the first gradient pulse g1 will be optimized according to experimental conditions. After applying the first gradient pulse g1, a second optimized control pulse module OCII' is applied, which simultaneously converts the nuclear spin singlet prepared by the first optimized control pulse module OCI' into a thermal equilibrium state. After applying the second optimized control pulse module OCII', a second gradient pulse g2 is applied, which will eliminate the secondary non-target signals generated by the excitation of the second optimized control pulse module OCII', and retain the thermal equilibrium state signal that is not disturbed by the gradient field. The specific pulse width and intensity of the second gradient pulse g2 will be optimized according to experimental conditions. After applying the second gradient pulse g2, the singlet voxel point-resolved spectroscopy (PRESS) module is used for spatial localization. This module converts the thermal equilibrium state of the methylene H4, H5 spin pairs and / or methyl H6 spin system of the methionine molecule, prepared by the second optimized control pulse module OCII' and preserved by the second gradient pulse g2, into a single quantum coherent state. This singlet voxel point-resolved spectroscopy is well-known in the field and will not be elaborated further in this invention. Finally, magnetic resonance signal acquisition is performed to obtain the filtered signal of the methylene H4, H5 spin pairs and / or methyl H6 spin system of the methionine molecule.

[0024] The Figure 6In the pulse sequence, the duration of the pressure water pulse WET is 4 seconds, and the power is 15 dB. The application time of the first optimized control pulse OCI is 60-80 ms, and the power is 29.01 dB; the application time of the second optimized control pulse OCII is 60-80 ms, and the power is 29.01 dB; the duration of the gradient pulse g is 1.0 ms, and the intensity of the gradient pulse g is 6.8 mT / cm; the cycle waiting time before applying the pressure water pulse WET is set to 4 seconds.

[0025] The Figure 7 In the pulse sequence, the application time of the first optimized control pulse module OCI' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the application time of the second optimized control pulse module OCII' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the duration of the first gradient pulse g1 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm; the duration of the second gradient pulse g2 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm. The PRESS module, consisting of three sinc pulses (one 90-degree sinc pulse and two 180-degree sinc pulses) and gradients in three directions, achieves the selection and excitation of individual voxels in the sample to be tested; the parameters in the preparation and detection pulse sequence are set as follows: sampling interval 2.0s, echo time 30ms, sampling times 64, sampling points 512, and voxel size 10×30×15mm. 3 .

[0026] The above experimental parameters were optimized based on actual conditions.

[0027] The present invention also provides the application of the above-mentioned targeted filtering method in controlling the nuclear spin quantum state evolution of specific groups in methionine molecules, realizing the specific screening of methionine signals, and improving the intensity of molecularly targeted nuclear magnetic resonance signals.

[0028] The beneficial effects of this invention include: It differs from conventional methods for quantifying metabolites in that it is painless, non-invasive, rapid, and highly selective. Based on nuclear magnetic resonance spectroscopy, this invention precisely achieves the quantum state evolution of different functional groups in methionine molecules through optimized control methods, enabling highly efficient, sensitive, and selective in-situ identification and detection of methionine molecules in target samples in a non-invasive manner. This invention can also be applied to monitor the content and distribution of methionine molecules within living biological tissues, and has significant application prospects in the biomedical and medical fields. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the main process steps of an embodiment of the present invention.

[0031] Figure 2 This is the structural formula of the methionine molecule of the present invention.

[0032] Figure 3 The single-pulse methionine deuterium aqueous solution of the present invention in a liquid NMR instrument 1 H-spectrum. The spectrum shows the proton signals of the methionine molecule.

[0033] Figure 4 The graph shows the pulse amplitude and phase of the first optimized control pulse OCⅠ for preparing methionine molecules with H4 and H5 spin pairs as multi-spin quantum states, as a function of pulse time.

[0034] Figure 5 The curves showing the pulse amplitude and phase variations with pulse time for the first optimized control pulse module OCI' used in the preparation of the methionine molecule methyl H6 spin system as a multi-spin quantum state in this invention.

[0035] Figure 6 This invention relates to the preparation and detection of multispin quantum states in a spectroscopic instrument for methylene H4 and H5 spin pairs and methyl H6 spin systems.

[0036] Figure 7 This invention relates to the preparation and detection sequence of multispin quantum states for methylene H4 and H5 spin pairs and methyl H6 spin systems in an imaging spectrometer.

[0037] Figure 8 The images show the proton NMR spectrum and filtered spectrum of methionine in a deuterated aqueous solution obtained by NMR spectroscopy. Figure 8 (a) Single pulse of methionine deuterium aqueous solution in liquid NMR spectrometer. 1 H spectrum, Figure 8 (b) for applying Figure 6 Filtering results of the methylene H4 and H5 spin pairs after the pulse sequence. Figure 8 (c) for applying Figure 6 Filtering results of the methyl H6 spin system after pulse sequence.

[0038] Figure 9 The images show the hydrogen spectrum and filtered spectrum of methionine in aqueous solution obtained using an imaging spectrometer. Figure 9(a) Images of an aqueous methionine solution acquired using an imaging spectrometer. 1 H spectrum, Figure 9 (b) for applying Figure 7 Filtering results of the methylene H4 and H5 spin pairs after the pulse sequence. Figure 9 (c) for applying Figure 7 Filtering results of the methyl H6 spin system after pulse sequence.

[0039] Figure 10 This is a T1-weighted imaging spectrum of isolated pig brain tissue in an imaging spectrometer.

[0040] Figure 11 This is a proton spectrum obtained from isolated porcine brain tissue using a PRESS sequence in an imaging spectrometer.

[0041] Figure 12 The images show the proton spectrum and filtered spectrum of isolated porcine brain tissue after injection of methionine solution. Figure 12 (a) Proton spectrum of isolated porcine brain tissue after injection of methionine solution, acquired using PRESS sequence in an imaging spectrometer. Figure 12 (b) Applying imaging spectrometer to isolated porcine brain tissue after injection of methionine solution. Figure 7 Filtering results of the methylene H4 and H5 spin pairs after the pulse sequence. Figure 12 (c) Applying imaging spectrometer to isolated porcine brain tissue injected with methionine solution. Figure 7 Filtering results of the methyl H6 spin system after pulse sequence. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0043] This invention proposes a magnetic resonance spectroscopy method capable of selectively observing the magnetic resonance signal of methionine molecules. This method utilizes optimized control pulses to precisely control the quantum state evolution of the nuclear-spin coupling system of the methionine molecule. By preparing and transforming the multi-spin quantum state of the methionine molecule, efficient and selective observation of the methylene magnetic resonance signal of the methionine molecule is achieved. This method can solve the problem of overlapping spectral peaks of different molecules in in vivo magnetic resonance spectroscopy, enabling highly efficient and selective detection of the magnetic resonance signal of methionine molecules in target samples in a non-invasive manner. Furthermore, this invention has the advantages of simple operation and rapid response. This technology can not only perform highly sensitive detection of methionine molecules in complex biological ex vivo tissue samples, but also rapidly detect the content and distribution of methionine molecules within living biological tissues, showing significant application prospects in the biomedical and medical fields.

[0044] The main steps of the embodiments of the present invention are as follows: Figure 1 As shown:

[0045] Step 1: Obtain characteristic parameters such as the chemical shift and coupling constant of the protons in the methionine molecule in aqueous solution;

[0046] Step 2: Design and prepare multi-spin quantum states of different groups and pulse sequences for selective signal observation based on characteristic parameters such as chemical shift and coupling constant of methionine molecules.

[0047] Step 3: Apply a pulse sequence to the target sample to obtain the methionine proton signal after targeted screening.

[0048] In one specific embodiment, the present invention provides a methionine molecule targeted filtering method based on nuclear magnetic resonance multi-spin quantum state signal screening, which realizes the nuclear spin evolution and detection of different groups of methionine molecules.

[0049] The method specifically includes the following steps:

[0050] 1. Prepare a 50 mmol / L aqueous solution of methionine with deuterium, and adjust the pH of the solution to neutral. The molecular structure of methionine can be seen in [image / formula missing]. Figure 2 A 90° pulse was applied to the methionine deuterium water sample using a liquid nuclear magnetic resonance spectrometer to obtain... Figure 3 The single pulse shown 1 H-ray spectroscopy. The methionine molecule has multiple proton nuclei, and there is a complex coupling network between the proton signals. The assignments of some signals in the spectrum have been marked on the spectral peaks and in the molecular structure. The water peak signal was used as an internal standard, and its chemical shift was calibrated to 4.7 ppm. Figure 3 The signal at the chemical shift δ = 2.18 ppm is a single peak with a classic Lorentz line shape, which can be attributed to the methyl proton signal. The quartet signal at δ = 3.85 ppm can be attributed to the methylene peak H1. The multiple split signals at δ = 2.23 ppm and δ = 2.17 ppm can be attributed to the same carbon hydrogens H2 and H3 on the methylene spin pair. The triplet signal at δ = 2.69 ppm can be attributed to another set of same carbon hydrogens H4 and H5 on the methylene spin pair. There is a strong coupling between the methylene H4 and H5 spin pairs, with a coupling magnitude of -13.6 Hz; there is a weak coupling between the methylene H4 and H5 spin pairs and the methylene H2 and H3 spin pairs, with coupling magnitudes of 7.9 Hz and 7.4 Hz, respectively. The methionine methyl peak does not exhibit J coupling with other protons.

[0051] 2. Applying deuterium methionine aqueous solution Figure 6 Pulse sequences used in spectroscopic instruments for the preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and / or methyl H6 spin systems. For example... Figure 8As shown in (a), to facilitate comparison of filtering effects, a methionine deuterium aqueous solution is inserted. 1 The filtering results of H-MRS for the H4 and H5 spin pairs of methionine methylene are as follows: Figure 8 As shown in (b), compared to the original methionine molecule 1 H-MRS Figure 8 (a) Comparison, Figure 8 (b) only contains the triple splitting signal of the methylene H4 and H5 spin pairs; all non-target signals are pulse-filtered, with a filtering efficiency of approximately 68% for the H4 and H5 spin pairs. The experimental results for methionine methyl peak filtering are shown below. Figure 8 (c) The results show that the spectrum contains only a single peak of methyl peak signal, and all non-target signals are filtered by pulse. The filtering efficiency of the methyl peak spin system is about 85%.

[0052] 3. Prepare a 250 mmol / L methionine aqueous solution and adjust the pH to neutral. Use a conventional MRI pulse sequence (e.g., T1-weighted magnetic resonance imaging) to locate the methionine aqueous solution in the imaging spectrometer and select the target region. Use PRESS sequences to obtain the methionine aqueous solution in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 9 (a) Using the water peak signal as an internal standard, its chemical shift was calibrated to 4.7 ppm. The chemical shift of the methylene H4 and H5 spin pairs was 2.5 ppm, indicating strong coupling between them with a coupling magnitude of -13.6 Hz; weak coupling existed between the methylene H4 and H5 spin pairs and the methylene H2 and H3 spin pairs, with coupling magnitudes of 7.9 Hz and 7.4 Hz, respectively. The chemical shift of the methionine methyl peak was 2.0 ppm. This signal was a single peak and exhibited classic Lorentz linearity, showing no J coupling with other protons.

[0053] 4. Preparation and detection of multispin quantum states of methylene H4, H5 spin pairs or methyl H6 spin systems by applying methionine aqueous solution to an imaging spectrometer. Experimental results are as follows: Figure 9 (b) and Figure 9 As shown in (c), compared to the original methionine molecule 1 H-MRS Figure 9 (a) Comparison, Figure 9 (b) Only the triplet signal of the H4 and H5 spin pairs remains, with a chemical shift of approximately 2.5 ppm. The methyl peak is almost completely invisible at 2.0 ppm, with only a partial residual signal, and the residual signal is an inverted peak. The filtering efficiency is taken as the ratio of the peak heights before and after filtering, and the filtering efficiency of H4 and H5 is 50%. Figure 9 (c) contains only a single peak of methyl signal, while H1, H2, H3, H4, and H5 signals are all filtered out, and the filtering efficiency of the methyl peak can reach 70%.

[0054] 5. Select isolated pig brain tissue, use conventional MRI pulse sequences (such as magnetic resonance T1-weighted pulse sequences) to locate the isolated pig brain tissue in an imaging spectrometer, and select the region to be tested. Figure 10 T1-weighted imaging spectra of isolated porcine brain tissue in an imaging spectrometer. PRESS sequences were used to obtain the T1-weighted imaging spectra of isolated porcine brain tissue in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 11 In the T1-weighted imaging spectrum, areas with higher brightness have higher fat content, while areas with lower brightness have higher water content. The white boxes represent voxels selected for the PRESS sequence, with voxel sizes of 10×30×15mm. 3 The nuclear magnetic resonance (NMR) spectrum of pig brain tissue is quite similar to that of human brain tissue, and it contains a variety of metabolic molecules, such as lactic acid (Lac) at 1.2 ppm, N-acetylaspartic acid (NAA) at 1.8 ppm, and creatine (Cr) and choline (Cho) near 3.0 ppm, among other metabolites.

[0055] 6. Exogenous methionine solution was injected into isolated porcine brain tissue. The isolated porcine brain tissue was localized in an imaging spectrometer using conventional MRI pulse sequences (such as T1-weighted pulsed MRI sequences), and the region to be measured was selected. PRESS sequences were used to obtain images of the methionine-injected isolated porcine brain tissue in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 12 (a) Preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and methyl H6 spin system in porcine brain tissue injected with methionine solution and subjected to imaging spectrometry. Figure 12 (b) shows the results of the methionine H4 and H5 methylene spin pair filtering experiment in pig brain. A clearly split H4 and H5 triplet signal appeared at 2.5 ppm, indicated by a red curve. After filtering, the methyl peak signal at 2.0 ppm was almost completely eliminated, the spectral baseline was flatter, and the signal-to-noise ratio was improved. The filtering efficiency of the methionine methylene spin pair signal was approximately 50%. Figure 12 (c) shows the results of the methionine methyl peak filtering experiment in pig brain. A single methyl signal peak exists at 2.0 ppm, indicated by a blue curve. After filtering, non-target signals such as creatine and choline molecular signals are significantly suppressed, with a methyl peak filtering efficiency of 50%.

[0056] Example 1

[0057] In a liquid NMR instrument, multispin quantum states of different groups of the methionine molecule were prepared and signal-selectively observed. The instrument used in the experiment was a Bruker AVANCE III 500MHz NMR instrument, and the probe used was a Bruker dual-resonance broadband high-resolution probe. This example uses a deuterated solution of the methionine molecule.

[0058] The specific steps are as follows:

[0059] Apply a 90° pulse to obtain... Figure 8 The single pulse of the solution sample shown in (a) 1 H-spectrum. The water peak signal was used as an internal standard, and its chemical shift was calibrated to 4.7 ppm. Figure 8 (a) The signal at chemical shift δ = 2.18 ppm is a single peak with a classic Lorentz line shape, which can be attributed to the methyl proton signal; the quartet signal at δ = 3.85 ppm can be attributed to the methylene peak H1; the multiple splitting signals at δ = 2.23 ppm and δ = 2.17 ppm can be attributed to the same carbon hydrogens H2 and H3 on the methylene spin pair; the triplet signal at δ = 2.69 ppm can be attributed to another set of same carbon hydrogens H4 and H5 on the methylene spin pair. There is a strong coupling between the methylene H4 and H5 spin pairs, with a coupling magnitude of -13.6 Hz; there is a weak coupling between the methylene H4 and H5 spin pairs and the methylene H2 and H3 spin pairs, with coupling magnitudes of 7.9 Hz and 7.4 Hz, respectively. The methionine methyl peak does not exhibit J coupling with other protons.

[0060] Applying deuterium methionine aqueous solution Figure 6 Pulse sequences used for the preparation and detection of multi-spin quantum states of different groups in methionine molecules in spectroscopic instruments. Experimental results are as follows: Figure 8 As shown.

[0061] The filtering results for the methionine methylene H4 and H5 spin pairs are as follows: Figure 8 As shown in (b), compared to the original methionine molecule 1 H-MRS Figure 8 (a) Comparison, Figure 8 (b) only contains the triple splitting signal of the methylene H4 and H5 spin pairs; all non-target signals are pulse-filtered, with a filtering efficiency of approximately 68% for the H4 and H5 spin pairs. The experimental results for methionine methyl peak filtering are shown below. Figure 8 (c) The results show that only the methyl peak signal is present in the spectrum, and the non-target signals are all filtered by the pulse. The filtering efficiency of the methyl peak spin system is about 85%. This indicates that the above pulse sequence can be used to prepare and detect multi-spin quantum states of different groups of methionine molecules in a liquid NMR instrument.

[0062] The optimal experimental parameters in this invention are as follows: Figure 6In the pulse sequence, the filtered pulse parameters for the methylene H4 and H5 spin pairs are as follows: the duration of the WET (Whiplash Interruption) module is 4 s, and the power is 15 dB; the application time of the first optimized control pulse OCI is 80 ms, and the power is 29.01 dB; the application time of the second optimized control pulse OCI is 80 ms, and the power is 29.01 dB; the duration of the gradient pulse g is 1.0 ms, and the intensity of the gradient pulse g is 6.8 mT / cm. The filtered pulse parameters for the methyl H6 spin system are as follows: the duration of the WET module is 4 s, and the power is 15 dB; the application time of the first optimized control pulse OCI is 60 ms, and the power is 29.01 dB; the application time of the second optimized control pulse OCI is 60 ms, and the power is 29.01 dB; the duration of the gradient pulse g is 1.0 ms, and the intensity of the gradient pulse g is 6.8 mT / cm. Example 2

[0063] In an imaging spectrometer, multi-spin quantum states of different groups of methionine molecules were prepared and signal-selective observation was achieved. The instrument used in the experiment was a Siemens 3T Prisma nuclear magnetic resonance spectrometer, with the body coil serving as the radio frequency coil and the 64-channel head coil serving as the receiver. This example uses an aqueous solution of methionine molecules.

[0064] The specific steps are as follows:

[0065] Methionine aqueous solution was localized in an imaging spectrometer using conventional MRI pulse sequences (such as T1-weighted pulse sequences) to select the target region. PRESS sequences were used to obtain the molecular weight of methionine in the aqueous solution in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 9 (a) The water peak signal was used as an internal standard, and its chemical shift was calibrated to 4.7 ppm. The chemical shift of the methylene H4 and H5 spin pairs was 2.5 ppm, indicating strong coupling between them with a coupling magnitude of -13.6 Hz; the methylene H4 and H5 spin pairs were weakly coupled with the methylene H2 and H3 spin pairs, with coupling magnitudes of 7.9 Hz and 7.4 Hz, respectively. The methionine methyl peak had a chemical shift of 2.0 ppm. This signal was a single peak and exhibited classic Lorentz linearity, showing no J coupling with other protons.

[0066] Apply to methionine aqueous solution Figure 7 The image shows pulse sequences for the preparation and detection of multispin quantum states targeting different groups of the methionine molecule in an imaging spectrometer. Experimental results are as follows: Figure 9 (b) and Figure 9 As shown in (c), compared to the original methionine molecule 1 H-MRS Figure 9 (a) Comparison, Figure 9(b) Only the triplet signal of the H4 and H5 spin pairs remains, with a chemical shift of approximately 2.5 ppm. The methyl peak is almost completely invisible at 2.0 ppm, with only a partial residual signal, and the residual signal is an inverted peak. The filtering efficiency is taken as the ratio of the peak heights before and after filtering, and the filtering efficiency of H4 and H5 is 50%. Figure 9 In (c), only a single peak of the methyl signal exists; the signals H1, H2, H3, H4, and H5 are all filtered out, and the filtering efficiency of the methyl peak can reach 70%. This indicates that the above pulse sequence can be used to prepare and detect multi-spin quantum states of different groups of methionine molecules in an imaging spectrometer.

[0067] The optimal experimental parameters in this invention are as follows: Figure 7 In the pulse sequence, the application time of the first optimized control pulse module OCI' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the application time of the second optimized control pulse module OCⅡ' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the duration of the first gradient pulse g1 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm; the duration of the second gradient pulse g2 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm. The PRESS module, consisting of three sinc pulses (one 90-degree sinc pulse and two 180-degree sinc pulses) and gradients in three directions, achieves the selection and excitation of individual voxels in the sample to be tested. The sampling interval of the preparation and detection pulse sequence parameters is set to 2.0s, the echo time to 30ms, the number of samplings to 64, the number of sampling points to 512, and the voxel size to be 10×30×15mm. 3 .

[0068] Example 3

[0069] The method of this invention was applied to the preparation and signal targeting screening of multi-spin quantum states of different groups of methionine molecules in isolated biological samples. The instrument used in the experiment was a Siemens 3T Prisma nuclear magnetic resonance spectrometer, with a body coil as the radio frequency coil and a 64-channel head coil as the receiver. This example uses isolated porcine brain tissue and isolated porcine brain tissue injected with methionine solution.

[0070] The specific steps are as follows:

[0071] Isolated porcine brain tissue was selected, and the isolated porcine brain tissue was located in an imaging spectrometer using conventional MRI pulse sequences (such as magnetic resonance T1-weighted pulse sequences), and the region to be tested was selected. Figure 10 T1-weighted imaging spectra of isolated porcine brain tissue in an imaging spectrometer. PRESS sequences were used to obtain the T1-weighted imaging spectra of isolated porcine brain tissue in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 11In the T1-weighted imaging spectrum, areas with higher brightness have higher fat content, while areas with lower brightness have higher water content. The white boxes represent the voxels selected for the PRESS sequence. The NMR spectrum of pig brain tissue is quite similar to that of human brain tissue, containing a variety of metabolic molecules, such as lactate (Lac) at 1.2 ppm, N-acetylaspartate (NAA) at 1.8 ppm, and creatine (Cr) and choline (Cho) near 3.0 ppm, among other metabolites.

[0072] Exogenous methionine solution was injected into isolated porcine brain tissue. The isolated porcine brain tissue was localized in an imaging spectrometer using conventional MRI pulse sequences (such as T1-weighted pulsed MRI sequences), and the target region was selected. PRESS sequences were used to obtain images of the methionine-injected isolated porcine brain tissue in the imaging spectrometer. 1 H-MRS, spectrum visible Figure 12 (a) Preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and methyl H6 spin system in porcine brain tissue injected with methionine solution and subjected to imaging spectrometry. Figure 12 (b) shows the results of the methionine H4 and H5 methylene spin pair filtering experiment in pig brain. A clearly split H4 and H5 triplet signal appeared at 2.5 ppm, indicated by a red curve. After filtering, the methyl peak signal at 2.0 ppm was almost completely eliminated, the spectral baseline was flatter, and the signal-to-noise ratio was improved. The filtering efficiency of the methionine methylene spin pair signal was approximately 50%. Figure 12 (c) shows the results of the methyl peak filtering experiment for methionine in pig brain. A single methyl signal peak exists at 2.0 ppm, indicated by a blue curve. After filtering, non-target signals such as creatine and choline are significantly suppressed, with a methyl peak filtering efficiency of 50%. This indicates that the above pulse sequence can still achieve the preparation and detection of multi-spin quantum states of different groups of methionine molecules in imaging spectrometers, even in complex biological samples containing a mixture of fat and water.

[0073] The optimal experimental parameters in this invention are as follows: Figure 7In the pulse sequence, the application time of the first optimized control pulse module OCI' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the application time of the second optimized control pulse module OCⅡ' is 80ms, and the maximum amplitude of the pulse unit is 100Hz; the duration of the first gradient pulse g1 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm; the duration of the second gradient pulse g2 is 1ms, and the intensity of the gradient pulse is 2Gauss / cm. The PRESS module, consisting of three sinc pulses (one 90-degree sinc pulse and two 180-degree sinc pulses) and gradients in three directions, achieves the selection and excitation of individual voxels in the sample to be tested. The parameters of the preparation and detection pulse sequence are set as follows: sampling interval 2.0s, echo time 30ms, sampling times 64, sampling points 512, and voxel size 10×30×15mm. 3 .

[0074] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. The pulses applicable to the preparation and detection of multi-spin quantum states of different groups in the methionine molecule are not limited to optimized pulse methods. The present invention protects the multi-spin quantum state preparation and detection sequences of different groups in the methionine molecule required in steps i and iii, or numerical pulse sequences based on other optimized methods. The pulse sequences include multi-spin quantum state preparation and detection sequences for methylene H4, H5 spin pairs or methyl H6 spin systems in spectrometers, and multi-spin quantum state preparation and detection sequences for methylene H4, H5 spin pairs and methyl H6 spin systems in imaging spectrometers.

[0075] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A method for targeted filtering of methionine molecules based on multi-spin quantum state signals from nuclear magnetic resonance, characterized in that, The targeted filtering method uses nuclear magnetic resonance pulse sequences to control the evolution of the nuclear spin quantum state of methionine molecules by optimizing pulse excitation. It prepares and transforms multi-spin Zeeman-order quantum states of methionine molecules, achieving selective detection of methionine magnetic resonance signals. The method includes the following core steps: Step i: The six-spin system of methionine molecule, consisting of two methylene groups, one methine group and one methyl group, is transformed from thermal equilibrium state to multi-spin Zeeman order quantum state by the first optimized control pulse OCI. Step ii: By applying gradient pulses, the signal of the nuclear spin in the single quantum state in the system is eliminated, thus preserving the multi-spin Zeeman order quantum state of the target system; Step iii: The multi-spin Zeeman order quantum state is converted into an observable state by the second optimized control pulse OCII, and the magnetic resonance signal is acquired.

2. The targeted filtering method as described in claim 1, characterized in that, In step i, the first optimized control pulse OCI is obtained by the GRAPE numerical calculation method, and the first optimized control pulse contains one or more sub-pulses with different amplitudes and phases; By controlling the spin evolution of the methylene, methine, and methyl nuclei spin coupling systems of the methionine molecule through optimized pulsed OCI, the entire spin system is brought from thermal equilibrium state ρ(0)=I. 1z +I 2z +I 3z +I 4z +I 5z +I 6z Transformed into a multi-spin quantum state ρ(1)=I 1x +I 2x +I 3x +4I 2z I 3z I 4z +4I 2z I 3z I 5z +I 6x In one pair of methylene groups, two hydrogen nuclei are prepared as a three-spin Zeeman order, and the remaining four spins are prepared as a single quantum state; and / or, when observing the methyl hydrogen nucleus, the nuclear spin of the methyl group in the methionine molecule is changed from the equilibrium state ρ(0) = I. 1z +I 2z +I 3z +I 4z +I 5z +I 6z Transform into the target state ρ(1)'=I 1x +I 2x +I 3x +I 4x +I 5x +I 6z .

3. The targeted filtering method as described in claim 1, characterized in that, In step ii, by adjusting the power, time, and position of the pulse gradient field, the suppression of non-target signals and the selective observation of the magnetic resonance signal of methionine molecules are achieved and optimized.

4. The targeted filtering method as described in claim 1, characterized in that, In step iii, the entire spin system of methylene, methine, and methyl is controlled from the three-spin Zeeman order quantum state ρ(1)=I by the second optimized control pulse OCII. 1x +I 2x +I 3x +4I 2z I 3z I 4z +4I 2z I 3z I 5z +I 6x To the observable state ρ(2)=I 4x +I 5x Transition; and / or, when observing the methyl hydrogen, design a second optimized control pulse OCII to control the nuclear spin of the methyl group of the methionine molecule from the single quantum state ρ(1)'=I 1x +I 2x +I 3x +I 4x +I 5x +I 6z Towards the observable state ρ(2)'=I 6x The transformation was then carried out; finally, selective observation of the methionine molecule's magnetic resonance signal was obtained through magnetic resonance signal acquisition.

5. The targeted filtering method as described in claim 1, characterized in that, The pulse sequences include the preparation and detection sequences of multi-spin quantum states for methylene H4, H5 spin pairs and / or methyl H6 spin systems in a spectrometer, as well as the preparation and detection sequences of multi-spin quantum states for methylene H4, H5 spin pairs and / or methyl H6 spin systems in an imaging spectrometer.

6. The targeted filtering method as described in claim 5, characterized in that, The spectrometer includes a pulse sequence for the preparation and detection of multispin quantum states of methylene H4, H5 spin pairs and / or methyl H6 spin systems, comprising a water pressure pulse WET, a first optimized control pulse OCI, a gradient pulse g, and a second optimized control pulse OCII. The water pressure pulse WET suppresses water signals through the T1 effect; the first optimized control pulse OCI acts on a specific nuclear spin, causing it to evolve from a thermal equilibrium state toward a target spin quantum state; the gradient pulse g applies a gradient field to eliminate non-target signals generated by the secondary excitation of the first optimized control pulse. The second optimized control pulse OCII transfers a specific group from a spin quantum state to an observable state, which can be detected by an NMR instrument.

7. The targeted filtering method as described in claim 5, characterized in that, The imaging spectrometer includes a multi-spin quantum state preparation and detection pulse sequence for methylene H4, H5 spin pairs and / or methyl H6 spin systems, comprising a saturated water pressurization module WET, a first optimized control pulse module OCI', a second optimized control pulse module OCII', a first gradient pulse g1, a second gradient pulse g2, and a singlet voxel point-resolved spectroscopy module. The WET saturated pressure water module is used to suppress water signals; The first optimized control pulse module OCI' acts on a specific nuclear spin, causing it to evolve from a thermal equilibrium state toward a target multi-spin quantum state; The first gradient pulse g1 is used to apply a gradient field to eliminate non-target signals generated by the excitation of the first optimization control pulse module OCI'; The second optimized control pulse OCII' is used to transition a specific group from a multi-spin quantum state to a thermal equilibrium state; The second gradient pulse g2 is used to apply a gradient field to eliminate non-target signals generated by the secondary excitation of the second optimization control pulse module OCII'; The single-line element-resolved spectral module is used for spatial positioning and signal excitation, ultimately enabling NMR signal detection.

8. The targeted filtering method as described in claim 6, characterized in that, The duration of the pressure pulse WET is 4s, and the power is 15dB; the application time of the first optimized control pulse OCI is 60-80ms, and the power is 29.01dB; the application time of the second optimized control pulse OCII is 60-80ms, and the power is 29.01dB; the duration of the gradient pulse g is 1.0ms, and the intensity of the gradient pulse g is 6.8mT / cm; the cycle waiting time before applying WET is set to 4s.

9. The targeted filtering method as described in claim 7, characterized in that, The first optimized control pulse module OCI' has an application time of 80ms and a maximum pulse unit amplitude of 100Hz; the second optimized control pulse module OCII' has an application time of 80ms and a maximum pulse unit amplitude of 100Hz; the first gradient pulse g1 has a duration of 1ms and an intensity of 2Gauss / cm; the second gradient pulse g2 has a duration of 1ms and an intensity of 2Gauss / cm; the PRESS module uses three sinc pulses and three directional gradients to select and excite individual voxels in the sample to be tested; the parameters in the preparation and detection pulse sequence are set to a sampling interval of 2.0s, an echo time of 30ms, 64 sampling times, 512 sampling points, and a voxel size of 10×30×15mm. 3 .

10. The application of the targeted filtering method as described in any one of claims 1-9 in controlling the nuclear spin quantum state evolution of specific groups in methionine molecules, achieving specific screening of methionine signals, and improving the intensity of molecularly targeted nuclear magnetic resonance signals.

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