WO2021114499A1 - Method for selectively detecting target object by using nuclear spin singlet state - Google Patents

Abstract

Disclosed is a method for selectively detecting a target object by using a nuclear spin singlet state. The characteristic of a nuclear spin singlet state not being affected by a pulsed gradient field is used, and after the nuclear spin singlet state of a nuclear spin coupling system of a target object is prepared, the pulsed gradient field is applied to the target object in order to disperse other magnetic resonance signals other than the nuclear spin singlet state of the target object, and a nuclear spin singlet state signal of the target object is maintained, thereby realizing the selective detection of a nuclear magnetic signal of the target object. The method for selectively detecting a target object by using a nuclear spin singlet state in the present invention has a good accuracy, sensitivity and selectivity; by means of the method, the interference of other physical signals can be eliminated, and signals of target object molecules can be accurately detected and obtained from a system with complex components; and the method has a significant application value in fields such as biology, medicine, chemistry and chemical engineering.

Description

Method for selectively detecting target using nuclear spin singlet

This application requires that the application date is December 09, 2019, the application number is 201911249189.7, the invention title is "Method for Selective Detection of Targets Using Nuclear Spin Monomorphism", the application date is December 09, 2019, and the application number is 201911248840.9, the title of the invention is "Using nuclear spin singlet to realize the method and application of magnetic resonance imaging of the target", the application date is December 9, 2019, the application number is 201911249153.9, the title of the invention is "Using nuclear spin singlet Priority of three Chinese invention patent applications in the “Method of Detecting Targets in Specified Space by Magnetic Resonance Spectroscopy with State Selectivity”.

Technical field

The invention belongs to the field of magnetic resonance detection, and specifically relates to a method for selectively detecting a target object by using a nuclear spin singlet.

Background technique

The principles of magnetic resonance imaging (MRI) and spectroscopy (MRS) both use radio frequency signals of a certain frequency to excite nuclear spins under the action of an external magnetic field, thereby generating resonance signals. Modern MRI and MRS have developed into a very powerful medical diagnostic method, especially suitable for diagnostic testing and scientific research on brain tissue, nervous system and human soft tissue. One of the core technologies in MRI and MRS is pulse sequence. Pulse sequence refers to a pulse or combination of pulses designed for a specific purpose. The pulse sequence can realize the manipulation of the nuclear spins in the object to be tested and generate the expected magnetic resonance signal. Collect the magnetic resonance signal of the test object and perform corresponding data processing to obtain the MRI and MRS of the test object.

Traditional MRI and MRS are often the observation of proton nuclear spins in the test object. If the object of observation is a living organism, the signal source is mainly water molecules in the living organism. Because of the different content of water molecules in different parts and organs of the organism, normal tissues and lesions, or different molecular relaxation properties. MRI medical diagnosis is usually realized based on the differences in the properties of these water molecules. Unlike MRI, MRS technology uses MRI technology to select a specific part of the organism to be tested, and then performs magnetic resonance spectroscopy on the selected part. In principle, MRS can detect biochemical molecules including water, fat, a variety of amino acids, and glucose. However, due to the diverse structure of various biochemical molecules and the complex environment in the organism, the signals of MRS are usually very complicated, and the signals of different biochemical molecules overlap seriously. Traditional MRS technology often fails to achieve selective observation of specific molecules.

Summary of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for selectively detecting targets using nuclear spin singlets. The nuclear spin singlet is a special spin state of the nuclear spin coupling system. This state has the following characteristics: 1. The nuclear spin singlet can be prepared by a reasonably designed pulse sequence; 2. The pulse sequence for preparing the nuclear spin singlet is related to the chemical structure of the molecule, and different molecular structures correspond to different nuclei. The spin singlet prepares a pulse sequence; 3. The spin state does not undergo spin state evolution under the action of the pulse gradient field.

Based on the above characteristics, the present invention designs a series of singlet magnetic resonance pulse sequences based on nuclear spins. The core design idea of these pulse sequences is to take advantage of the feature that the nuclear spin singlet is not affected by the pulse gradient field. After preparing the nuclear spin singlet of the target nuclear spin coupling system, apply a pulse gradient to the target. The field diffuses other magnetic resonance signals other than the target nuclear spin singlet, and maintains the target nuclear spin singlet signal, thereby achieving selective detection of the target nuclear magnetic signal. The method of the present invention has good accuracy, sensitivity, reproducibility and selectivity, can eliminate the interference of other substance signals, and accurately detect the signal of the target molecule from a system with complex composition. It has important application value in the fields of biology, medicine, chemistry, chemical engineering, etc. It is a new and original technology.

Taking advantage of the characteristics of the nuclear spin singlet preparation pulse sequence corresponding to the chemical structure of the molecule, the nuclear spin singlet preparation pulse sequence can select the signal of a specific target molecule. The target molecules are usually various compound molecules with a spin coupling system (nuclear spin number>=2). Under normal circumstances, compound molecules with multi-spin coupling systems can be used to prepare singlet states and perform selective observations. The chemical structure requirements of this molecule are: at least a pair of mutually coupled nuclear spins of the same type, there is a certain chemical shift difference between the nucleus and nuclear spins, and its chemical shift and coupling constant are relatively stable, and will not follow Changes in the external environment (such as temperature, pH, etc.). In the implementation of the present invention, it is usually necessary to design the nuclear spin singlet preparation pulse according to the chemical shift and J coupling of the target multi-spin coupling system. Among them, the design of nuclear spin singlet preparation pulse belongs to common knowledge in the field. Generally speaking, the chemical shift of each spin and the J coupling between spins in a spin coupling system (nuclear spin number>=2) are the key parameters for the preparation of a nuclear spin singlet pulse sequence. According to the different properties of the spin coupling system, the design of the nuclear spin singlet preparation pulse needs to be adjusted accordingly. Weak spin coupling system (J.Am.Chem.Soc.126(2004), 6228-6229) and strong spin coupling system (Phys.Chem.Chem.Phys., 13(2011), 5556-5560) usually have Different singlets prepare pulse sequences.

Preferably, the target is a dopamine molecule (formula (1)). In the molecule, H _a, H _b, H _d and form a three-spin coupling system. In this system, the respective spin chemical shifts (ω _x , x = a, b, d) and J coupling (J _ab , J _ad , J _bd ) are as follows (take (ω _a +ω _d )/2 as the radio frequency emission center _{): ω a = 36.5Hz, ω} b = -36.5Hz, ω c = -7.8Hz, J ab = 8.14Hz, J ad = 0Hz, J bd = 2.18Hz. Based on these properties of the spin-coupled system, the singlet pulse sequence can be designed.

In the present invention, preferably, the target substance may also include dopamine, taurine, acetylaspartic acid, AGG, hypotaurine, creatine, choline chloride, glucose, glutathione and the like.

Specifically, the implementation process of the method of the present invention includes the following steps:

Step 1: Excite the magnetic resonance signal of the target (molecule) in the system to be measured by pulse or pulse combination;

Step 2: Select a pulse or pulse combination according to the multi-spin coupling properties of the target, and prepare the nuclear spin coupling system of the target into a nuclear spin singlet through the pulse or pulse combination;

Step 3: Decoupling the nuclear spin coupling system of the target within a certain period of time by decoupling pulse (pulse or pulse combination), and maintaining the nuclear spin singlet of the target, and applying The pulse gradient field disperses all non-target nuclear spin singlet magnetic resonance signals in the system to be measured;

Step 4: Convert the target nuclear spin singlet into a signal required for magnetic resonance, such as a nuclear magnetic spectrum signal or an imaging signal, by pulse or pulse combination, to achieve selective detection of the target nuclear magnetic signal.

Among them, the targets are various substances with a multi-spin coupling system.

The main purpose of step 2 is to prepare nuclear spin singlets. According to the specific spin coupling characteristics of the target system, the nuclear spin singlet of the target is prepared through a reasonably designed pulse or pulse combination sequence. The design steps are briefly described as follows: i. Analyze the target molecule, and divide the spin coupling structure existing in its structure into strong spin coupling structure and/or weak coupling structure; ii. Prepare the respective spin coupling structure in the target molecule Compare the preparation efficiency of each singlet; iii. Select the spin-coupling structure and pulse sequence with the highest singlet preparation efficiency for selective detection of target molecules in the sequence shown in Figure 1.

The pulse or pulse combination includes an excitation pulse and a nuclear spin singlet preparation pulse. The function of the excitation pulse is to excite the nuclear spin signal. The parameters such as its form and intensity can be adjusted according to the experimental needs. Usually it is a hard pulse with higher power. The power of the pulse can be adjusted according to the specific molecular system, and the requirement is to be uniform. Groundly excite the target nuclear spin system to minimize the influence of relaxation. The role of nuclear spin singlet preparation pulse is to prepare nuclear spin singlet, using the characteristic that nuclear spin singlet will not be dispersed by the pulse gradient field, for signal selection. There are many ways to prepare the pulse of nuclear spin singlet. For example, the pulse shown in Figure 5 is a SLIC pulse (SJ DeVience, RL Walsworth, MS Rosen, Phys. Rev. Lett. 111 (2013) 173002(1-4).), in which the power of the spin lock pulse and the application time τ _SL varies with the difference in chemical shifts and coupling constants between nuclear spins. When applying a spin-lock pulse, it is necessary to align the center frequency with a specific nuclear spin. In addition to SLIC pulses, other pulses for preparing nuclear spin singlets are also applicable in the present invention, such as M2S pulses for nuclear spin systems with similar chemical shifts (G. Pileio, M. Carravetta and MHLevitt, Proc. Natl. Acad Sci.USA,2010,107,17135-17139.), for the J-coupling modulated pulse (M.Carravetta, MH Levitt, J.Am.Chem.Soc.126(2004), 6228- 6229.) Wait.

In step 3, this step contains two key components: 1. Decoupling pulse; 2. Pulse gradient field. The function of the decoupling pulse is to maintain the singlet nuclear spin of the target. The decoupling pulse needs to be designed according to the chemical shift and J coupling of the multi-spin coupling system of the target. The form of the decoupling pulse can be continuous pulse irradiation, or a combination of pulses with a specific timing. The action time of the decoupling pulse can be adjusted according to the nature of the system. The specific time needs to be measured experimentally, that is, the time of the decoupling pulse is changed experimentally, and the signal strength and selectivity of the single state are observed to determine the best Decoupling time. In principle, the power of the decoupling pulse is affected by the chemical shift difference of the spin system, and needs to be adjusted according to the magnitude of the chemical shift difference of the spin system.

In step 3, the nuclear spin coupling system of the target is decoupled by a decoupling pulse, so as to maintain the nuclear spin singlet of the target; the way to achieve decoupling can be through continuous wave decoupling, or a pulse with a specific timing Combine for decoupling. Continuous wave decoupling and pulse combination decoupling are well-known technologies in the field. The choice of decoupling time increases with the increase of the relaxation time of the nuclear spin singlet, generally from milliseconds to seconds, and can be adjusted according to the nature of the system to obtain the best effect. The decoupling time needs to be longer than the pulse gradient field action time.

In step 3, the function of the pulse gradient field is to disperse all other non-nuclear spin singlet nuclear magnetic signals except the target nuclear spin singlet. The effect of the pulse gradient field can be adjusted and optimized by adjusting the intensity, application times and position of the pulse gradient field. The application time is on the order of milliseconds. The power of the pulse gradient field can be adjusted according to the dispersion effect of the pulse gradient field. The direction of the pulse gradient field is the z-axis direction in the same direction as the static magnetic field. The best pulse gradient field effect is to retain only single-state signals.

In the pulse sequence of Fig. 1, the above-mentioned pulse gradient field is applied twice. In step 3, it is also possible to apply the decoupling pulse alone without applying the pulse gradient field. But in this way, although a certain degree of signal selection can be achieved, the overall effect is poor. In step 3, if the pulse gradient field is applied alone without applying the decoupling pulse, the purpose of selecting the target molecule signal cannot be achieved.

In step 4, the target nuclear spin singlet is converted into signals required for subsequent magnetic resonance experiments through pulses or pulse combinations, such as nuclear magnetic spectroscopy signals or imaging signals. The selection and design of pulses or pulse combinations are the same as those in step 2. The design of the pulse combination is similar, that is, different pulses or pulse combinations are selected according to the multi-spin coupling properties of different targets, and the target nuclear spin singlet is converted into signals required for subsequent magnetic resonance experiments.

In addition, the present invention also includes the following basic steps: (1) Obtain the chemical shift difference and coupling constant between the spins of the target by the traditional NMR measurement method; (2) Pulse the chemical shift difference and the coupling constant of the coupling system Sequence design, determine the power and pulse width of the single-state spin-locked pulse; (3) Implement the designed pulse sequence on the magnetic resonance instrument. These are known knowledge in the field.

The pulse sequence in Fig. 5 shows a specific example of the implementation of the above steps. Figure 5 is a schematic diagram of the pulse sequence. The sequence of the evolution of the spin state in this sequence is as follows: the 90-degree radio frequency pulse at A turns the longitudinal magnetization vector from the vertical axis to the x, y plane; after the spin-lock pulse at B is applied, the spin is generated in the state of the system Singlet; the subsequent gradient pulse g ₁ can eliminate the observable states other than the spin singlet; during the application of the decoupling pulse at C, the spin singlet is preserved, and other signals are attenuated by the effect of relaxation; then the second A gradient pulse g ₂ further eliminates other signals other than the spin singlet, and finally, the τ _SL pulse applied at D converts the spin singlet into an observable signal to realize signal detection.

When the target is AGG in the ¹ H spectrum of AGG deuterium aqueous solution (ie, amino acid molecule; L-Alanine-glycine-glycine, AGG; the following target amino acid molecules are specifically AGG), first apply the phase in the y direction according to Figure 5 90° hard pulse, and then apply ^{the center frequency between the transmitting center H b} , H ^b'signal and H ^c , H ^c'signal , the phase is in the x direction, and the time is τ ₁ (τ ₁ is the τ _{SL in Figure 5} ), the locking pulse with the locking frequency ω _SL prepares the singlet state of the AGG molecule; then the z-direction gradient fields g ₁ and g ₂ and the decoupling pulse ω _dec (decoupling time τ _m ) are applied; then the emission center is H ^b , H ^{b 'signal} and the H ^c, H ^c' between the center frequency of the signal, the phase in the x direction, the time (τ _SL τ ₁ i.e. in FIG. 5) τ _1, the locking of the locking pulse frequency ω _SL; and finally Data sampling. Preparation H ^b, H ^{b 'singlet} used locking pulse action time _{τ 1 = 80ms (τ SL τ} 1 i.e. in FIG. 5), locking the frequency ω _SL = 17.2Hz, Preparation H ^c, H ^c' singlet used locking pulse The action time τ ₁ =125 ms (τ _{1 is τ SL in} Fig. 5), and the lock frequency ω _SL =18.5 Hz. Decoupling pulse power ω _dec =85Hz, decoupling time τ _m =50ms. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms.

^{When the target is AGG in the 1} H spectrum of a deuterium aqueous solution of a mixture of AGG and leucine, glutamic acid and glycine, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction, The time is τ ₁ ＝125ms (τ ₁ is τ _{SL in} Figure 5), the locking frequency is ω _SL =18.5Hz lock pulse, the transmission center of the lock pulse is H ^b , H ^b'signal and H ^c , H ^{c '} The center frequency between the signals to prepare the singlet of the AGG molecule; then apply the z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient The field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝85Hz, the decoupling time τ _m ＝50ms; then the transmitting center is one of H ^b , H ^b'signal and H ^c , H ^c'signal _{A locking pulse with a center frequency of ω SL} =18.5 Hz, a phase in the x direction, a time of τ ₁ =125 ms (τ ₁ is τ _{SL in} Figure 5), and a locking frequency of ω SL =18.5 Hz; finally, data sampling is performed.

When the target is the AGG in the ¹ H spectrum of the AGG and insulin mixture deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction for a time of τ ₁ =125ms(τ ₁ is the τ _{SL in} Fig. 5), the lock pulse with the lock frequency ω _SL = 18.5 Hz, the transmission center of the lock pulse is the center frequency between the ^{H b} , H ^b'signal and the H ^c , H ^{c'signal, and} This prepares the singlet of the AGG molecule; then applies z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time 1ms; decoupling pulse power ω _dec ＝85Hz, decoupling time τ _m ＝50ms; then apply ^{the center frequency between H b} , H ^b'signal and H ^c , H ^c'signal , the phase is in the x direction , Time is τ ₁ =125ms (τ ₁ is τ _{SL in} Figure 5), locking pulse with lock frequency ω _SL = 18.5 Hz; finally, data sampling is performed.

When the target is dopamine in the ¹ H spectrum of the dopamine-deuterium aqueous solution, move the RF center to ^{the center frequency between the H a} and H ^b signals on the benzene ring according to Figure 8; first apply a 90° hard phase in the x direction to the sample. Pulse, and then apply the combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} =30.9ms, the purpose is to remove the chemical shift evolution, and then apply

The singlet of the dopamine molecule can be obtained with the pulse of, where τ ₂ =6.8ms; since there is no spin system that is the same as the three hydrogens on the benzene ring in the DA molecule in the mixed system, only the singlet of the DA molecule is prepared; then Apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field strength is 5 Gauss/cm, and the action time is 1 ms; decoupling pulse power ω _dec ＝550Hz, decoupling time τ _m ＝50ms; apply next

And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals; finally signal acquisition.

^{When the target is the AGG in the 1} H spectrum of a very low-concentration dopamine-deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction for a time of τ ₁ =180ms(τ _{1 is τ SL in} Fig. 5), a lock pulse with a lock frequency ω _SL = 8.1 Hz, the transmission center of the lock pulse ^{is the center frequency between the Ha} and H ^b signals on the benzene ring; then a gradient field g in the z direction is applied ₁ and g ₂ and decoupling pulse; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms; the decoupling pulse power ω _dec ＝97 Hz, decoupling time τ _m ＝50ms; then apply ^{a lock pulse whose transmission center is the center frequency between the H a} and H ^b signals on the benzene ring, the phase is in the x direction, and the time is τ ₁ =180ms (τ ₁ is τ _{SL in} Figure 5) , Locking frequency ω _SL = 8.1Hz locking pulse; finally data sampling; increasing the number of accumulation of signal acquisition to 4000 times.

When the target is taurine in the ¹ H spectrum of a deuterium taurine aqueous solution, move the center of the radio frequency to the center frequency between the hydrogen signals of No. 1 and No. 2 on the methylene group according to Figure 8; first apply the phase position to the sample 90° pulse in the x direction, then apply a combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} =10ms, apply

After the singlet of taurine molecule can be obtained by the pulse of τ ₂ =6.8ms; then the z-direction gradient fields g ₁ and g ₂ and decoupling pulse are applied; the intensity and action time of the _{gradient fields g 1} and g _{2 need to be optimized} , Usually the gradient field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝500Hz, the decoupling time τ _m ＝50ms; then apply

And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals.

When the target is creatine in the ¹ H spectrum of creatine deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction for a time of τ ₁ =220ms (τ ₁ is FIG. 5 τ _SL), locking the frequency ω _SL = 18Hz locking pulse for H ^b, the center frequency between H ^{b 'signal,} thus prepared creatine molecule singlet emission center of the locking pulse; then applying Z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms; the decoupling pulse power ω _dec =70Hz, decoupling time τ _m =50ms; then apply a lock pulse with phase in the x direction, time τ ₁ =220ms, and lock frequency ω _SL =18Hz; finally, data sampling is performed.

When the target is acetylaspartic acid in the ¹ H spectrum of acetylaspartic acid deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction for a time of τ ₁ = 105ms _{(τ SL τ 1} i.e. in FIG. 5), locking the frequency ω _SL = 17.22Hz locking pulse, the locking pulse is emitted center H ^b, the center frequency between H ^{b 'signal,} thus preparing NAA Single state of the molecule; then apply a z-direction gradient field g ₁ and g ₂ and decoupling pulse; _{the intensity and action time of the gradient field g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms ; Decoupling pulse power ω _dec = 70 Hz, decoupling time τ _m = 50 ms; then apply a lock pulse with phase in the x direction, time τ ₁ = 105 ms, and lock frequency ω _SL = 17.22 Hz; finally, data sampling is performed.

When the target is acetyl aspartic acid in the ¹ H spectrum of a mixture of acetyl aspartic acid and mouse brain tissue, first apply a 90° hard pulse with the phase in the y direction to the sample according to Figure 5, and then apply the phase in the x direction, time τ ₁ = 105ms, the locking of the frequency ω _SL = 17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA emission center of the locking pulse; then applying z Directional gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of gradient fields g 1} and g ₂ need to be optimized, usually the gradient field strength is 10 Gauss/cm, and the action time is 1 ms; decoupling pulse power ω _dec ＝90Hz , Decoupling time τ _m =50ms; then apply a lock pulse with phase in the x direction, time τ ₁ =105ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _SL =17.22 Hz; finally, data sampling is performed.

The present invention also provides a method for realizing magnetic resonance imaging of a target by using a nuclear spin singlet. The target is prepared into a nucleus by the method for selectively detecting the target using the nuclear singlet as described above. Spin singlet, and further realize the selection of the target signal, and realize the magnetic resonance imaging of the target on this basis. The method includes:

Step a: Prepare the target into a nuclear spin singlet through the method of selectively detecting the target by using the nuclear spin singlet as described above, and then realize the selection of the target signal through the pulse gradient field and the decoupling pulse Finally, the nuclear spin singlet signal of the target is converted into the signal required for the subsequent steps through a suitable pulse or pulse combination.

Step b: The main components are various types of magnetic resonance imaging pulse sequences; the target signal obtained in step a can be imaged according to actual imaging requirements to realize magnetic resonance imaging of the target.

Wherein, in the step b, magnetic resonance imaging is performed using the signal of the target obtained in step a, so as to obtain a molecular magnetic resonance image of the target. In step b, different magnetic resonance imaging pulse sequences can be adopted as required, and the method for obtaining the magnetic resonance imaging pulse sequence is a method known in the art.

The magnetic resonance imaging of specific target molecules achieved by the above methods can be applied in many fields, such as early diagnosis and treatment of diseases, evaluation of curative effects, detection of drug molecular metabolism in specific organs, and detection of chemical reaction molecule distribution in reaction vessels for chemical determination. Chemical reaction process, etc. For example, in medicine, if the target is a molecule with high expression of the disease, then this method can be used as a means of early diagnosis and treatment of the disease and evaluation of the efficacy. In the field of pharmacy, if the target is a drug molecule, then this method can be used as a means to detect the metabolism of drug molecules in specific organs. In terms of chemistry/chemical industry, if the target is a chemical reaction molecule, then this method can be used as the distribution of the chemical reaction molecule in the reaction vessel to detect the progress of the chemical/chemical reaction.

The pulse sequence in Figure 6 shows a specific example of the implementation of the above steps. Figure 6 is a schematic diagram of the pulse sequence. The sequence of the evolution of the spin state in this sequence is as follows: the 90-degree radio frequency pulse at A turns the longitudinal magnetization vector from the vertical axis to the x, y plane; after the spin-lock pulse at B is applied, the spin is generated in the state of the system Singlet; the subsequent gradient pulse g ₁ can eliminate the observable states other than the spin singlet; during the application of the decoupling pulse at C, the spin singlet is preserved, and other signals are attenuated by the effect of relaxation; then the second A gradient pulse g ₂ further eliminates other signals other than the spin singlet, and finally the τ _SL pulse applied at D converts the spin singlet into the signal required for subsequent imaging experiments. Finally, the three-dimensional imaging pulse sequence realizes molecular imaging of the target molecule.

When the target is an acetylaspartic acid molecule, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction for a time of τ ₁ =105ms (τ ₁ is τ _{SL in} Figure 6) locking the frequency ω _SL = 17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single-state molecules of acetyl-aspartate emission center of the locking pulse; then applying a z-direction gradient Fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms; the decoupling pulse power ω _dec ＝90Hz, decoupling Coupling time τ _m =50ms; then apply a lock pulse with phase in the x direction, time τ ₁ =105ms (τ ₁ is τ _{SL in} Figure 6), and lock frequency ω _SL =17.22Hz; finally, perform frequency encoding in the y direction And the phase encoding in the x direction can obtain the magnetic resonance molecular imaging of the acetylaspartic acid molecules in the sample.

When the target is an amino acid molecule, set the RF center as ^{the center frequency between the signals of the amino acid molecule H c} and H ^c' . First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, Change to τ ₁ =125ms (τ ₁ is τ _{SL in} Figure 6), lock _{pulse with frequency ω SL} = 18.2 Hz, and then apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; gradient fields g ₁ and The intensity and action time of g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms; the decoupling pulse power ω _dec =90Hz, the decoupling time τ _m =50ms; the subsequent applied phase is in the x direction, and the time is τ ₁ = 125ms (τ ₁ is τ _{SL in} Figure 6), locking pulse with lock frequency ω _SL = 18.2 Hz; finally, frequency encoding in the y direction and phase encoding in the x direction can be used to obtain the magnetic resonance molecules of the amino acid molecules in the sample Imaging.

When the object is dopamine, a radio frequency as the center frequency of the center between the signal molecule dopamine H ^a, H ^b, the first pulse is applied to hard phase is 90 ° in the y-direction of the sample, then applying a phase in the x direction, to τ ₁ =180ms (τ _{1 is τ SL in} Fig. 6), locking _{pulse with frequency ω SL} = 8.1 Hz, and then applying z-direction gradient fields g ₁ and g ₂ and decoupling pulses; gradient fields g ₁ and g ₂ The intensity and the action time of the need to be optimized, usually the gradient field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝90Hz, the decoupling time τ _m ＝50ms; the applied phase is in the x direction and the time is τ ₁ =180ms (τ _{1 is τ SL in} FIG. 6 ), a locking pulse with a locking frequency ω _SL =8.1 Hz; finally, frequency encoding in the y direction and phase encoding in the x direction can be used to obtain magnetic resonance molecular imaging of the amino acid molecules in the sample.

The present invention also provides a method for using nuclear spin singlet selectivity to perform magnetic resonance spectroscopy detection of a target in a designated space. The magnetic resonance signal in the designated space is selected by magnetic resonance imaging layer selection technology. Based on the method described above using nuclear spin singlet to selectively detect the target, the nuclear spin singlet selectivity is used to select the signal of the target in the magnetic resonance signal in the specified space, and finally the target in the specified space is realized. The magnetic resonance spectrum of the signal.

Specifically, the method includes:

Step i: Select the magnetic resonance pulse sequence with the function of layer selection, and select the magnetic resonance signal in the designated space through the magnetic resonance imaging gradient layer selection technology;

Step ii: Using the method described above, using nuclear spin singlet selectivity to select the target signal in the magnetic resonance signal obtained in step i; including selecting different preparations according to the specific spin coupling characteristics of the target system Magnetic resonance pulse sequence of singlet nuclear spin;

Step iii: Convert the signal obtained in Step ii into a detectable signal, and perform detection.

The magnetic resonance spectroscopy of a specific target molecule in a designated space realized by the above method can be applied in many fields. It can be used for early diagnosis and treatment of disease, evaluation of curative effect, detection of drug molecular metabolism in specific organs, and detection of chemical reaction molecule distribution in reaction vessels. Used to determine the progress of chemical/chemical reactions, etc. For example, in medicine, if the target is a molecule with high expression of disease, then this method can use MRI to select the signal of a specific part of the organism, and then observe the molecule with high expression of disease through signal selection. This method can be used as a means of early diagnosis and treatment of diseases and evaluation of efficacy. In the field of pharmacy, if the target is a drug molecule, then this method can be used as a means to detect the metabolism of drug molecules in specific organs. In terms of chemistry/chemical industry, if the target is a chemical reaction molecule, then this solution can be used as the distribution of the chemical reaction molecule in the reaction vessel to detect the progress of the chemical/chemical reaction.

In the present invention, the method of selecting layers by magnetic resonance imaging gradient in step i is a method well known in the art. In the specific implementation process of step i, different magnetic resonance pulse sequences with layer selection function can be selected according to actual needs. The designated space in step i refers to the position of the specific part of the observation object in the space.

In the present invention, "by the method as described above" in the step ii refers to the method of selectively detecting a target by using nuclear spin monomorphism as described above.

In the present invention, in the step iii, the signal obtained in step ii can be converted into an observable signal by designing a pulse or a combination of pulses according to actual needs.

The pulse sequence of Fig. 7 shows a specific example of the implementation of the above steps. Figure 7 is a schematic diagram of the pulse sequence. The sequence of the evolution of the spin state of the sequence is as follows: the 90-degree radio frequency pulse at A turns the longitudinal magnetization vector from the vertical axis to the x, y plane; the subsequent waveform pulse at E and the matching gradient pulse g _z achieve a specific spatial position signal Selection; then the spin singlet is generated in the state of the system after the spin-lock pulse is applied at B; the subsequent gradient pulse g ₁ can eliminate the observable states other than the spin singlet; during the application of the decoupling pulse at C, The spin singlet is preserved, and other signals are attenuated under the influence of relaxation; then the second gradient pulse g ₂ further eliminates other signals other than the spin singlet, and finally the τ _SL pulse applied at D turns the spin singlet Converted into signals required for subsequent MRS experiments. Finally, the signal is observed to realize the MRS spectrum of a specific molecule in a specific space.

When the target is an acetylated aspartic acid, as the emission center between the center frequency of the H ^b, H ^{b 'signal,} the locking pulse frequency ω _SL = 17.22Hz, action time τ ₁ = 105ms (τ ₁ in FIG. 7 i.e. In τ _SL ), the intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized. Generally, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec ＝90 Hz, and the decoupling time τ _m ＝ 50ms.

When the target molecule is an amino acid, an emission center of H ^c, the center frequency between the H ^{c 'signal,} the locking pulse frequency ω _SL = 18.2Hz, action time τ ₁ = 125ms (τ ₁ in FIG. 7 τ i.e. _SL ), the intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized. Generally, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.

When the object is dopamine, emission center between the center frequency of H ^a, H ^b signals, locking pulse frequency ω _SL = 8.1Hz, action time τ (τ _SL i.e. τ ₁ in FIG. 7) ₁ = 180ms , The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized. Generally, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.

The beneficial effect of the present invention is that: the present invention is different from other previous magnetic resonance imaging and spectroscopy technologies in that a significant feature and innovation point is that it can realize the magnetic resonance imaging and spectroscopy of specific molecules. The realization of this feature and innovation is based on the innovative use of nuclear spin singlet. The present invention makes use of the characteristic that nuclear spin singlet is not affected by pulse gradient field for the first time, and the specific selectivity of molecular structure in the preparation process of nuclear spin singlet, so as to realize the selection of magnetic resonance signal of specific molecule and combine it Applied to magnetic resonance imaging and spectroscopy. In the application of magnetic resonance imaging, the present invention can truly realize magnetic resonance imaging of specific molecules. In the application of magnetic resonance spectroscopy, the present invention can observe the magnetic resonance spectra of specific molecules in the designated parts of the test object, and thereby realize the measurement of the spatial distribution of the specific molecules in the test object. The method or its variants can be combined with existing magnetic resonance imaging and spectroscopy to derive more magnetic resonance molecular imaging and spectroscopy technologies.

This method is based on magnetic resonance technology, and besides the characteristics of conventional magnetic resonance technology, it also has good accuracy, sensitivity and molecular signal selectivity. Without damaging the sample or changing the properties of the sample, the signal interference of other substances can be eliminated simply and effectively, and the signal of the target molecule can be accurately detected from a system with complex composition. For example, the method can be used to monitor the content and distribution of endogenous target substances in the organism without injecting exogenous probe molecules into the organism. Therefore, the target can be detected without damaging tissues and cells; this method can also be used to monitor the content and distribution of target molecules in chemical reactors. It can detect the signal of the target in the chemical reactor without destroying or interfering with the chemical reaction, so as to realize the observation of the chemical reaction process. At the same time, the method can also be combined with some exogenous targeting probe molecules, and by preparing the singlet of the targeting probe molecules, the detection of the content and distribution of the targeting probe molecules in the observation object can be realized.

This method has important application value in the fields of biology, medicine, chemistry, chemical industry, industrial production and so on.

Description of the drawings

Fig. 1 is a schematic diagram of a magnetic resonance pulse sequence for selective detection of target molecules by using nuclear spin singlet. Among them, ¹ H represents the hydrogen channel, and G _z represents the pulse gradient channel in the z direction.

Figure 2 is a schematic diagram of a three-dimensional imaging sequence based on monomorphic filtering. Among them, ¹ H represents a hydrogen channel, and G _x , G _y , and G _z represent pulse gradient channels in the x, y, and z directions, respectively.

Fig. 3 is a schematic diagram of MRS sequence using nuclear spin singlet to realize magnetic resonance signal selection. Among them, ¹ H represents a hydrogen channel, and G _x , G _y , and G _z represent pulse gradient channels in the x, y, and z directions, respectively.

Figure 4 is a schematic diagram of the molecular structure of dopamine of formula (1).

Fig. 5 is a schematic diagram of a pulse sequence for preparing a nuclear spin singlet based on spin locking to realize the selection of a specific molecular magnetic resonance signal. Among them, ¹ H represents the hydrogen channel, and G _z represents the pulse gradient channel in the z direction. Among them, the black rectangle at A represents 90 pulses, the black rectangle at B represents the spin-lock pulse, the box at C represents the decoupling pulse, the black rectangle at D represents the spin-lock pulse, and g ₁ and g ₂ represent gradient pulses. ω _SL and τ _SL are the power and time of the spin-locked pulse, and ω _dec and τ _m are the power and time of the decoupling pulse.

Fig. 6 is a pulse sequence for magnetic resonance molecular imaging based on spin-locked preparation of nuclear spin singlet states. Among them, ¹ H represents a hydrogen channel, and G _x and G _y represent pulse gradient channels in the x and y directions, respectively. Among them, the black rectangle at A represents 90 pulses, the black rectangle at B represents the spin-lock pulse, the box at C represents the decoupling pulse, the black rectangle at D represents the spin-lock pulse, and g ₁ , g ₂ , g ₃ and g ₄ represent Gradient pulse. ω _SL and τ _SL are the power and time of the spin-locked pulse, and ω _dec and τ _m are the power and time of the decoupling pulse.

Fig. 7 is an MRS pulse sequence for preparing nuclear spin singlet based on spin locking. Among them, ¹ H represents the hydrogen channel, and G _z represents the pulse gradient channel in the z direction. Among them, the black rectangle at A represents 90 pulses, the black rectangle at B represents the spin-lock pulse, the box at C represents the decoupling pulse, the black rectangle at D represents the spin-lock pulse, the multilobe shape at E represents the layer selection pulse, g ₁ , G ₂ and g _z represent gradient pulses. ω _SL and τ _SL are the spin lock pulse action time, and ω _dec and τ _m are the power and action time of the decoupling pulse.

Fig. 8 is a schematic diagram of a pulse sequence for preparing nuclear spin singlets based on multi-pulse technology to realize the selection of magnetic resonance signals of specific molecules. Among them, ¹ H represents the hydrogen channel, and G _z represents the pulse gradient channel in the z direction. Among them, the black rectangle at A represents a 90-degree pulse, the square at B represents a 180-degree pulse, the black rectangle at C represents a 90-degree pulse, the square at D represents a decoupling pulse, the black rectangle at E represents a 90-degree pulse, and the square at F represents For 180 degree pulses, g ₁ and g ₂ represent gradient pulses. τ ₁ and τ ₂ represent the time interval between pulses. ω _dec and τ _m are the power and time of the decoupling pulse.

9 is: a single pulse A) an aqueous solution of a ¹ H AGG deuterium spectrum; prepared based on nuclear spin singlet, to achieve a particular molecular AGG molecule ^b) H b, H b ^'groups, and ^c) H c, H ^c' based on Spectra of selective observation of cluster magnetic resonance signals.

FIG. 10 is: a) AGG leucine, glutamic acid and glycine, a mixture of deuterium aqueous monopulse ¹ H spectra; b) prepared based on nuclear spin singlet, H ^c to achieve AGG molecule, H ^{c 'group} selection signal The spectrum of sexual observations.

11 is: a) AGG insulin aqueous mixture of deuterium ¹ H single pulse spectrum; b) prepared based on nuclear spin singlet, H ^c to achieve AGG molecules selectively observed spectrum signal H ^{c 'group.}

FIG 12 is: a) DA deuterium aqueous monopulse ¹ H spectra; b) preparing nuclear spin singlet, DA molecules Based on H ^a, H ^b group selectively observed spectrum signal pair.

Figure 13 is: a) Single pulse ¹ H spectrum of DA deuterium aqueous solution, in which the mass fraction of DA is 0.0006%; b) Based on the preparation of nuclear spin singlet, the spectrum of selective observation of the ^{H d group signal of DA molecule is realized.}

Figure 14 is: a) a single pulse ¹ H spectrum of a deuterium taurine aqueous solution; b) a spectrum of selective observation of the signals of the 1, 2 groups of taurine molecules based on the preparation of nuclear spin singlets.

15 is: a) an aqueous solution of creatine deuterium monopulse ¹ H spectra; b) preparing nuclear spin singlet, creatine molecule Based on H ^b, the signal observed selective H ^{b 'groups} spectrum pairs.

16 is: a) NAA deuterium aqueous monopulse ¹ H spectra; b) prepared based on nuclear spin singlet, NAA achieve molecule H ^b, the signal observed selective H ^{b 'groups} spectra.

FIG 17 is: a) NAA mouse brain tissue with a mixture of single-pulse ¹ H spectra; b) prepared based on nuclear spin singlet, NAA achieve molecule H ^b, the signal observed selective H ^{b 'groups} spectra.

Figure 18 is: a) the actual photo and schematic diagram of the sample. The sample is: a 4mm inner diameter glass nuclear magnetic sample tube contains a mixture of 60% water and 40% deuterium water. The glass nuclear magnetic sample contains 4 small glass tubes with a 0.9mm outer diameter, each containing 24% NAA deuterium. Aqueous solution, 11.2% AGG deuterium aqueous solution, a mixed water of 40% water and 60% deuterium water, and a mass fraction of 10% DA deuterium aqueous solution. b) Spin echo imaging image of the above sample; c) Magnetic resonance molecular imaging image of NAA molecule; d) Magnetic resonance molecular imaging image of AGG molecule; e) Magnetic resonance molecular imaging image of DA molecule.

Figure 19 is: a) Spin echo imaging image of the test sample, the white frame indicates the signal selection area in the layer selection; b) the conventional MRS spectrum of the white frame selection area; c) the MRS spectrum of the AGG molecule; d) the MRS of the NAA molecule Spectrum; e) MRS spectrum of DA molecule. The sample is the same as the sample in Example 10, which is: a 4mm inner diameter glass nuclear magnetic sample tube contains a mixed water of 60% water and 40% deuterium water, and the glass nuclear magnetic sample contains 4 small glass tubes with an outer diameter of 0.9mm, respectively It contains 24% NAA deuterium aqueous solution, 11.2% AGG deuterium aqueous solution, mixed water of 40% water and 60% deuterium water, and 10% DA deuterium aqueous solution.

Figure 20 is a flowchart of the main steps in the embodiment.

Fig. 21 is a schematic flow chart of a method for selectively detecting a target object using nuclear spin singlet in the present invention.

FIG. 22 is a schematic flow chart of a method for realizing magnetic resonance imaging of a target by using a singlet of nuclear spin in the present invention.

FIG. 23 is a schematic flowchart of a method for detecting a target in a designated space by magnetic resonance spectroscopy using nuclear spin singlet selectivity according to the present invention.

Detailed ways

The invention will be further described in detail with reference to the following specific embodiments and drawings. The process, conditions, and experimental methods for implementing the present invention, except for the content specifically mentioned below, are all common knowledge and common knowledge in the field, and the present invention has no special limitations.

The main steps of the implementation are shown in Figure 20:

1. The spin system can be roughly divided into a strong coupling system and a weak coupling system. Depending on the nature of the spin system, the corresponding pulse sequence also needs to be adjusted;

2. The parameters in the pulse sequence are closely related to the molecular characteristics of the sample. In order to obtain a better signal selection effect, the experimental parameters in the pulse sequence need to be optimized;

3. Observe the target molecular signal as required.

There is sample preparation in the examples. The configuration method and steps are well-known in the field.

Example 1-Selection of AGG NMR signal in ¹ H spectrum of L-Alanine-glycine-glycine (AGG) deuterium aqueous solution

Experimental sample: Amino acid molecule, L-Alanine-glycine-glycine (AGG) is dissolved in D ₂ O, prepared as an AGG deuterium aqueous solution with a mass fraction of 0.6%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. Using the pulse sequence shown in Figure 5, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply ^{the center frequency between the emission center H b} , H ^b'signal and H ^c , H ^c'signal , and the phase is at x direction, time is τ ₁ , locking pulse with locking frequency ω _SL prepares the singlet of AGG molecules; then z-direction gradient fields g ₁ and g ₂ and decoupling pulse ω _{dec are} applied; then the emission center is H ^b , H ^{b 'signal} and the H ^c, H ^c' between the center frequency of the signal, the phase in the x direction, the time τ _1, the locking of the locking frequency ω _SL pulses; last data sampling. Preparation H ^b, H ^{b 'singlet} used locking pulse action time τ ₁ = 80ms, locking the frequency ω _SL = 17.2Hz, Preparation H ^c, H ^c' singlet used locking pulse action time τ ₁ = 125ms, the locking frequency ω _SL = 18.5 Hz. Decoupling pulse power ω _dec =85Hz, decoupling time τ _m =50ms. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms.

The single pulse method and experiment are well-known knowledge in the field.

Measurement results: Through the pulse sequence shown in Figure 5, singlet preparation and signal selection were performed on the ^{spin coupling system (H b} , H ^b'and H ^c , H ^{c') in the AGG molecule, and two spins were obtained respectively.} Couple the signals of the system H ^b , H ^b' (Figure 9b) and H ^c , H ^c' (Figure 9c), while suppressing other signals.

Results and Discussion Analysis: Through analysis, FIG. 9, H ^b AGG molecule, H ^{b 'and} H ^c, H ^c' spin coupling system is formed independently, and may be prepared in a single-state selection signal. Since the H ^c, H ^{c 'high} signal strength, to H ^c, H ^c' as the characteristic selection signal, a signal AGG molecules can obtain better signal sensitivity.

Example 2-Selection of AGG NMR signal in the ¹ H spectrum of a mixture of AGG and leucine, glutamic acid and glycine in deuterium aqueous solution

Experimental sample: amino acid molecule, L-Alanine-glycine-glycine (AGG) and leucine, glutamic acid and glycine mixture of deuterium aqueous solution, the mass fraction of each substance is: AGG: 0.63%, leucine: 0.48% , Glutamic acid: 0.61%, Glycine: 0.53%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. The method of using the pulse sequence shown in FIG. 5 is the same as that in Embodiment 1. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply a lock pulse _{with the phase in the x direction, time τ 1} =125ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _{SL =18.5Hz} the lock pulse emission center of the center frequency between H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, in order to produce a single molecule state AGG; then applying a z-direction gradient field, and g ₁ and g ₂ Decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec =85Hz, decoupling time τ _m =50ms. ; Emission center is then applied between the center frequency of the H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, the phase in the x direction, the time τ ₁ = 125ms (τ ₁ τ _SL i.e., FIG. 5), The lock frequency is _{a lock pulse of ω SL} =18.5 Hz; finally, data sampling is performed.

The single pulse method and experiment are well-known knowledge in the field.

Measurement: by the pulse sequence shown in FIG. 5, we AGG molecule, H ^c, H ^{c 'singlet} spin systems were prepared and the selection signal, spectrum shown in Figure 10. It can be seen that, in Figure 10, the main ^{signals are H c} and H ^c' , and all other signal strengths are greatly suppressed, and the HDO signal is still less than 0.1% of the original signal.

^{Example 3-Selection of 1} H Spectrum AGG Nuclear Magnetic Signal of AGG and Insulin Mixture in Deuterium Aqueous Solution

Experimental sample: amino acid molecule, deuterium aqueous solution of a mixture of L-Alanine-glycine-glycine (AGG) and bovine insulin, in which the mass fraction of AGG is 0.05% and bovine insulin is 1.04%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. The method of using the pulse sequence shown in FIG. 5 is the same as that in Embodiment 1. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply _{a lock pulse with the phase in the x direction, time τ 1} =125ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _SL =18.5 Hz. the locking pulse emission center between the center frequency H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, in order to produce a single molecule state AGG; then applying a z-direction gradient field, and g ₁ and g ₂ went Coupled pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝85Hz, decoupling time τ _m ＝50ms; then apply ^{the center frequency between H b} , H ^b'signal and H ^c , H ^c'signal , the phase is in the x direction, and the time is τ ₁ = 125 ms (τ _{1 is τ SL in} Fig. 5 ), a locking pulse with a locking frequency ω _SL =18.5 Hz; finally, data sampling is performed.

The single pulse method and experiment are well-known knowledge in the field.

Measurement: by the pulse sequence shown in FIG. 5, we AGG molecule, H ^c, H ^{c 'singlet} spin systems were prepared and the selection signal, spectrum shown in Figure 11. It can be seen that the main ^{signals of H c} and H ^c'in Fig. 11 have achieved the suppression of the bovine insulin signal and HDO signal.

^{Example 4-Selection of 1} H spectrum DA nuclear magnetic signal of dopamine (DA) deuterium aqueous solution

_{Experimental sample: D 2} O solution of dopamine, dopamine (DA), in which the mass fraction of DA is 1.5%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 8. During the experiment, the RF center needs to be moved to the center frequency between the ^Ha and H ^{b signals on the benzene ring.} First apply a 90° hard pulse with the phase in the x direction to the sample, and then apply a combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} =30.9ms, the purpose is to remove the chemical shift evolution, and then apply

The singlet of the dopamine molecule can be obtained with the pulse of, where τ ₂ =6.8ms; since there is no spin system that is the same as the three hydrogens on the benzene ring in the DA molecule in the mixed system, only the singlet of the DA molecule is prepared; then Apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝550Hz, decoupling time τ _m ＝50ms; apply next

And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals; finally signal acquisition. Among them, in order to optimize the filtering effect, the power of the decoupling pulse needs to be optimized.

The single pulse method and experiment are well-known knowledge in the field.

Measurement: using the pulse sequence shown in FIG. 8 Preparation spin coupling system H ^a, H ^b, H ^d nuclear spin singlet state, a function of selecting the DA molecules and H ^a H ^b signals, while achieving other signals Of suppression.

Analysis Results and discussion: we DA molecules of H ^a, H ^b, H ^d singlet spin systems were prepared and the signal selected by the pulse sequence shown in FIG. 8, spectrum shown in Figure 12. It can be seen in FIG. 12 mainly DA molecules and H ^a H ^b signal, all other signal strength is greatly compressed, wherein the HDO signal remaining less than the original 0.05%.

^{Example 5-Selection of 1} H-spectrum DA nuclear magnetic signal of very low concentration dopamine (DA) deuterium aqueous solution

_{Experimental sample: D 2} O solution of dopamine, dopamine (DA), in which the mass fraction of DA is 0.0006%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. The method of using the pulse sequence shown in FIG. 5 is the same as that in Embodiment 1. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply a lock pulse _{with the phase in the x direction, time τ 1} =180ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _{SL =8.1Hz.} the locking pulse emission center between the center frequency on the benzene ring with H ^a H ^b signal; then applying a z-direction gradient field g ₁ and g ₂ and decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝97Hz, decoupling time τ _m ＝50ms; then apply ^{a locking pulse whose transmission center is the center frequency between the H a} and H ^b signals on the benzene ring, the phase is in the x direction, and the time is τ ₁ ＝ 180ms (τ _{1 is τ SL in} Fig. 5), lock pulse with lock frequency ω _SL = 8.1 Hz; finally, data sampling is performed. This experiment needs to increase the number of accumulations of signal acquisition. In the experiment of Fig. 13b, the cumulative number of times is 4000.

The single pulse method and experiment are well-known knowledge in the field.

Measurement result: The nuclear spin singlet of the ^{spin-coupling system H a} , H ^b , and H ^d was prepared by using the pulse sequence shown in Fig. 8 to realize the selection of the signal of the ^{H d group of the DA molecule while suppressing other signals.}

Analysis Results and discussion: we DA molecules of H ^a, H ^b, H ^d singlet spin systems were prepared and the signal selected by the pulse sequence shown in FIG. 8, spectrum shown in Figure 13. ^{It can be seen that the signal of DA molecule H d} is mainly in Figure 13b, and the intensity of all other signals is greatly suppressed.

^{Example 6-Selection of 1} H Spectrum Taurine Nuclear Magnetic Signal of Taurine Deuterium Aqueous Solution

Experimental sample: Taurine, Taurine (Tau) D ₂ O solution, wherein the mass fraction of Tau is 2.1%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 8. During the experiment, the center of the radio frequency needs to be moved to the center frequency between the No. 1 hydrogen and No. 2 hydrogen signals on the methylene group. First apply a 90° pulse with the phase in the x direction to the sample, and then apply a combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} ＝10ms, apply

After the single state of the taurine molecule can be obtained from the pulse of, where τ ₂ =6.8ms; then z-direction gradient fields g ₁ and g ₂ and decoupling pulses are applied. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝500Hz, decoupling time τ _m ＝50ms; then apply

And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals.

The single pulse method and experiment are well-known knowledge in the field.

Measurement result: The nuclear spin singlet of the ^{spin coupling system H 1} , H ^{2 was} prepared by using the pulse sequence shown in Fig. 8 to ^{realize the selection of the H 1} and H ² signals of the taurine molecule, and realize the selection of other signals at the same time. Suppress (see Figure 14).

Result analysis and discussion: Using the pulse sequence shown in Figure 8, the singlet of the four-spin system composed of hydrogen on two methylene groups of taurine was prepared to realize the selection of the molecular signal of taurine and the other Suppression of signals.

^{Example 7-Selection of 1} H spectrum creatine nuclear magnetic signal of creatine deuterium aqueous solution

Experimental sample: creatine molecule, creatine D ₂ O solution, in which the mass fraction of creatine molecule is 1.2%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. The method of using the pulse sequence shown in FIG. 5 is the same as that in Embodiment 1. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply a lock pulse with the _{phase in the x direction, time τ 1} =220ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _{SL =18 Hz.} the lock pulse emission center between the center frequency H ^b, H ^{b 'signal,} thus prepared creatine molecule singlet; then applying a gradient field in the z direction g ₁ and g ₂ and decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝70Hz, decoupling time τ _m ＝50ms; then apply a lock with phase in the x direction, time τ ₁ ＝220ms (τ ₁ is τ _{SL in} Figure 5), lock frequency ω _SL ＝18Hz Pulse; data sampling is done last.

The single pulse method and experiment are well-known knowledge in the field.

Test result: Using the pulse sequence shown in Figure 5, by preparing ^{the nuclear spin singlet of the spin-coupling system H b} , H ^b' , the selection of the creatine molecular signal was realized, and the suppression of other signals was realized at the same time (see Figure 15).

Results and Discussion Analysis: Using the pulse sequence shown in FIG. 5, prepared creatine molecule coupled spin system H ^b, H ^{b 'singlet} achieve the selection of the creatine molecule signal, while the other signal is achieved suppress.

^{Example 8-Selection of 1} H-spectrum NAA nuclear magnetic signal of acetyl aspartic acid (NAA) deuterium aqueous solution

_{Experimental sample: D 2} O solution of N-acetylaspartic acid molecule (NAA), in which the mass fraction of NAA is 1.1%.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. The method of using the pulse sequence shown in FIG. 5 is the same as that in Embodiment 1. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply a lock pulse _{with the phase in the x direction, time τ 1} =105ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _{SL =17.22Hz.} the locking pulse emission center between the center frequency H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA; then applying a gradient field in the z direction g ₁ and g ₂ and decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝70Hz, decoupling time τ _m ＝50ms; then the applied phase is in the x direction, time is τ ₁ ＝105ms (τ ₁ is τ _{SL in} Figure 5), lock frequency ω _SL ＝17.22Hz Lock the pulse; data sampling is done last.

The single pulse method and experiment are well-known knowledge in the field.

Measurement results: Using the pulse sequence shown in Figure 5, by preparing ^{the nuclear spin singlet of the spin-coupling system H b} , H ^b' , the NAA signal can be selected and other signals can be suppressed at the same time (see Figure 16 ).

^{Example 9-Selection of 1} H-spectrum NAA NMR signal of the mixture of acetyl aspartic acid (NAA) and mouse brain tissue

Experimental sample: a mixture of NAA deuterium aqueous solution (NAA mass fraction is 1.1%) and mouse brain tissue.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: single pulse sequence and pulse sequence shown in Figure 5. First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply a lock pulse _{with the phase in the x direction, time τ 1} =105ms (τ ₁ is τ _{SL in} Figure 5), and lock frequency ω _{SL =17.22Hz.} between the center frequency of the H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA emission center of the locking pulse; then applying a z-direction gradient field g ₁ and g ₂ and decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 10 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝90Hz, decoupling time τ _m ＝50ms; then the applied phase is in the x direction, time τ ₁ ＝105ms (τ ₁ is τ _{SL in} Figure 5), lock frequency ω _SL ＝17.22Hz Lock the pulse; data sampling is done last.

The single pulse method and experiment are well-known knowledge in the field.

Measurement results: Using the pulse sequence shown in Figure 5, by preparing ^{the nuclear spin singlet of the spin-coupled system H b} , H ^b' , the selection of NAA signals and the suppression of other signals are realized at the same time (see Figure 17). ).

Example 10-Magnetic resonance molecular imaging of NAA, AGG and DA based on singlet signal filtering

Experimental sample: a 4mm inner diameter glass NMR sample tube contains a mixed water of 60% water and 40% deuterium water, and 4 small 0.9mm outer diameter glass tubes are placed in the glass NMR sample (see Figure 18a). Inside the small glass tube are 24.2% NAA deuterium aqueous solution, 11.2% AGG deuterium aqueous solution, 40% water and 60% deuterium water mixed water, and 10.5% DA deuterium aqueous solution with mass fraction.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: spin echo imaging sequence and pulse sequence shown in Figure 6. In the experiment of molecular imaging using the pulse sequence shown in Figure 6, the spin singlets of NAA, AGG, and DA are prepared separately to realize the selection of these molecular signals, and then the molecular imaging of each of these molecular signals is performed. The specific experimental steps are as follows:

NAA molecule: First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, time τ ₁ =105ms (τ ₁ is τ _{SL in} Figure 6), and lock frequency ω _SL =17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA emission center of the locking pulse; then applying a z-direction gradient field g ₁ and g ₂ and decoupling pulse. The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms. Decoupling pulse power ω _dec ＝90Hz, decoupling time τ _m ＝50ms; then the applied phase is in the x direction, time is τ ₁ ＝105ms (τ ₁ is τ _{SL in} Figure 6), lock frequency ω _SL ＝17.22Hz Lock the pulse; finally, the frequency encoding in the y direction and the phase encoding in the x direction can obtain the magnetic resonance molecular imaging of the NAA molecules in the sample.

AGG: The experimental procedure is the same as the NAA molecular imaging procedure described above. During the experiment, the RF center needs to be set as ^{the center frequency between the signals of the AGG molecule H c} and H ^c' , the lock pulse time is changed to τ ₁ =125 ms (τ ₁ is τ _{SL in} Figure 6), and the lock frequency ω _SL = 18.2 Hz.

DA: The experimental procedure is the same as the NAA molecular imaging procedure described above. During the experiment needs to be set to the center frequency of the RF center between signals DA molecules H ^a, H ^b, the locking pulse to the time τ ₁ = 180ms (τ ₁ τ _SL i.e., FIG. 6), locking the frequency ω _SL = 8.1Hz.

Spin echo imaging methods and experiments are well-known in the field.

Measurement results: The selective molecular imaging of NAA, AGG and DA was achieved (see Figure 18).

Result analysis and discussion: The spin echo imaging result is shown in Figure 18b. The large gray disc is formed by the mixed water of 60% water and 40% deuterium water in the 4mm inner diameter glass nuclear magnetic sample tube, which represents the cross section of the 4mm inner diameter glass nuclear magnetic sample tube. There are 4 small discs with different brightness from top to bottom, and each small disc has a black circle around it. The small discs represent the cross-sections of different small glass tubes, and the brightness is related to the concentration of the solution in the small glass tubes. The black circle comes from the wall of the small glass tube. The results of NAA molecular imaging are shown in Figure 18c. Since there are only NAA molecules in the top small glass tube in the sample, only the cross-sectional signal of the NAA small glass tube appears in the image in Figure 18c. Similarly, the molecular imaging images of AGG and DA only show cross-sectional signals of small glass tubes containing AGG and DA, respectively. It can be seen that the method of the present invention can perform selective molecular imaging from a complex mixed system, so as to obtain the spatial distribution of a certain specific substance. This provides a method for detecting a specific biochemical molecule in a biological body and realizing its molecular imaging.

Example 11-Magnetic resonance molecular MRS based on NAA, AGG and DA based on singlet signal filtering

Experimental sample: a 4mm inner diameter glass NMR sample tube contains a mixed water of 60% water and 40% deuterium water, and 4 small 0.9mm outer diameter glass tubes are placed in the glass NMR sample (see Figure 18a). Inside the small glass tube are 24.2% NAA deuterium aqueous solution, 11.2% AGG deuterium aqueous solution, 40% water and 60% deuterium water mixed water, and 10.5% DA deuterium aqueous solution with mass fraction.

Measuring instrument: BrukerAVANCE III 500MHz nuclear magnetic resonance instrument. The spectrometer is equipped with a gradient power amplifier in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

Measurement method: spin echo imaging sequence and pulse sequence shown in Figure 7. In the pulse sequence shown in Fig. 7, the signal layer is selected for the sample first. Layer selection methods and experiments are well-known knowledge in the field. In this example, the layer selection is excited by a hard pulse and then a combination of sinc wave pulse and gradient field is used to select the specific spatial signal of the sample. Then, the selection of molecular signals is achieved through the preparation of nuclear spin singlets of specific molecules, and finally the magnetic resonance spectroscopy observation of these molecular signals is carried out. The experimental parameters for specific molecular signal selection are as follows:

NAA: emission center between the center frequency of the H ^b, H ^{b 'signal,} the locking pulse frequency ω _SL = 17.22Hz, action time τ ₁ = 105ms (τ ₁ τ _SL i.e., in FIG. 7), the field gradient g _{The intensity and action time of 1} and g ₂ need to be optimized. Generally, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.

AGG: emitting center H ^c, the center frequency between the H ^{c 'signal,} the locking pulse frequency ω _SL = 18.2Hz, action time τ ₁ = 125ms (τ ₁ τ _SL i.e., in FIG. 7), the field gradient g _{The intensity and action time of 1} and g ₂ need to be optimized. Generally, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.

DA: emission center between the center frequency of the H ^a, H ^b signals, locking pulse frequency ω _SL = 8.1Hz, action time τ (τ _SL i.e. τ ₁ in FIG. 7) ₁ = 180ms, the gradient field g _{1 The intensity and action time of g 2} and g 2 need to be optimized. Usually, the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.

Spin echo imaging methods and experiments are well-known in the field.

Measurement results: molecular selective magnetic resonance spectroscopy for NAA, AGG and DA was achieved (see Figure 19).

Result analysis and discussion: The spin echo imaging result of the sample is shown in Figure 18a. The large gray disc is formed by the mixed water of 60% water and 40% deuterium water in the 4mm inner diameter glass nuclear magnetic sample tube, which represents the cross section of the 4mm inner diameter glass nuclear magnetic sample tube. There are 4 small discs with different brightness from top to bottom, and each small disc has a black circle around it. The small discs represent the cross-sections of different small glass tubes, and the brightness is related to the concentration of the solution in the small glass tubes. The black circle comes from the wall of the small glass tube. The white box in Figure 18a indicates the signal selection area in the layer selection. Fig. 18b is a conventional MRS spectrum of the area indicated by the white box in Fig. 18a. The signals of DA, AGG, NAA and water (HDO) can be clearly seen in this spectrum. Figure 18c A molecular MRS spectrum after nuclear spin singlet preparation and signal selection of AGG molecules. It can be seen that NAA and DA in the spectrum have basically disappeared, and the signal of water (HDO) has also been greatly suppressed. Similarly, Figure 18d and Figure 18e show the molecular MRS spectra of NAA and DA. From these molecular MRS spectra, it can be found that the method of the present invention can perform molecular selective MRS from a complex mixed system, thereby obtaining the spatial distribution of a certain specific substance. This provides a method for detecting a specific biochemical molecule in the organism and realizing its molecular MRS.

The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be imagined by those skilled in the art are all included in the present invention, and the appended claims are the protection scope.

Claims (20)

1. A method for selectively detecting a target using nuclear spin singlet, characterized in that the method comprises the following steps:

   Step 1: Excite the magnetic resonance signal of the target in the system to be measured by pulse or pulse combination;

   Step 2: Prepare a pulse or a combination of pulses by a nuclear spin singlet, and prepare the nuclear spin coupling system of the target into a nuclear spin singlet;

   Step 3: Decoupling the nuclear-spin coupling system of the target by decoupling pulses, maintaining the nuclear-spin singlet of the target, and dispersing all non-targets in the system under test by applying a pulse gradient field Nuclear spin singlet magnetic resonance signal;

   Step 4: Convert the target nuclear spin singlet into a signal required for magnetic resonance by pulse or pulse combination, so as to achieve selective detection of the target magnetic resonance signal;

   Wherein, the target substances are various substances with a multi-spin coupling system.
2. The method according to claim 1, wherein in the step 2, the nuclear spin coupling system of the target is prepared into the nuclear spin singlet of the target through a pulse sequence, and the design of the pulse sequence It includes the following steps:

   i. Analyze the target molecule and classify the spin-coupling structure existing in its structure into a strong spin-coupling structure and/or a weak-coupling structure;

   ii. Prepare singlets of respective spin-coupled structures in the target molecule, and compare the preparation efficiency of each singlet;

   iii. Select the spin coupling structure and pulse sequence with the highest singlet preparation efficiency to prepare the nuclear spin singlet of the target.
3. The method according to claim 1, characterized in that, in the step 3, the way to achieve decoupling includes a spin-locked pulse, or a combination of pulses with a specific timing; the decoupling time is selected as the nuclear spin singlet The relaxation time increases with the increase; the decoupling time is longer than the action time of the pulse gradient field; and/or,

   In the step 3, the non-target nuclear spin singlet magnetic resonance signal in the signal from step 2 is diffused by the pulse gradient field, while maintaining the target nuclear spin singlet signal to achieve the selectivity of the target signal Observation: The selection effect of target molecule signal is achieved by adjusting the intensity, application times and position of the pulse gradient field.
4. The method according to claim 1, wherein in step 4, different pulses or pulse combinations are selected according to the multi-spin coupling properties of different targets; and/or, in step 4, pulse or The pulse combination converts the singlet signal from step 3 into the signal required for subsequent nuclear magnetic spectroscopy and/or imaging.
5. The method according to claim 1, wherein when the target is AGG in the ¹ H spectrum of AGG deuterium aqueous solution, firstly apply a 90° hard pulse with the phase in the y direction, and then apply the emission center H ^b , H ^{b 'and} signal H ^c, H ^c' between the center frequency of the signal, the phase in the x direction, the time τ _1, the locking of the locking frequency ω _SL molecules prepared AGG pulse singlet; then applying a gradient field in the z direction, and g ₁ g ₂ and decoupling pulse ω _dec ; then apply ^{the center frequency between the transmission center H b} , H ^b'signal and H ^c , H ^c'signal , the phase is in the x direction, the time is τ ₁ , and the lock frequency is ω _SL the locking pulse; last sampling data; preparation H ^b, H ^{b 'singlet} used locking pulse action time τ ₁ = 80ms, locking the frequency ω _SL = 17.2Hz, preparation H ^c, H ^c' singlet used locking pulse duration of action τ ₁ ＝125ms, lock frequency ω _SL =18.5Hz; decoupling pulse power ω _dec ＝85Hz, decoupling time τ _m ＝50ms; _{the intensity and action time of gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5Gauss/cm, the action time is 1ms; and/or,

   ^{When the target is AGG in the 1} H spectrum of a deuterium aqueous solution of a mixture of AGG and leucine, glutamic acid and glycine, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction and the time for τ ₁ = _125mt, lock-in frequency ω _SL = 18.5Hz the locking pulse, the locking pulse emission center of the center frequency between H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, thus prepared AGG molecule Single state; then apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of gradient fields g 1} and g ₂ need to be optimized, usually the gradient field strength is 5 Gauss/cm, and the action time is 1 ms; decoupling Pulse power ω _dec ＝85Hz, decoupling time τ _m ＝50ms; then apply ^{the center frequency between H b} , H ^b'signal and H ^c , H ^c'signal , the phase is in the x direction, and the time is τ ₁ = 125mt, lock pulse with lock frequency ω _SL = 18.5Hz; finally data sampling is performed; and/or,

   ^{When the target is AGG in the 1} H spectrum of AGG and insulin mixture deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, time τ ₁ =125mt, lock frequency ω _SL = 18.5Hz locking pulse, the locking pulse emission center of the center frequency between H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, in order to produce a single molecule state AGG; then applying a gradient field in the z direction g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms; the decoupling pulse power ω _dec ＝85Hz, decoupling time τ _m = 50ms; subsequently applied to the center frequency of the emission center between H ^b, H ^{b 'signal} and the H ^c, H ^c' signal, the phase in the x direction, the time τ ₁ = 125mt, locking the frequency ω _SL = 18.5 Hz lock pulse; last data sampling; and/or,

   When the target is dopamine in the ¹ H spectrum of dopamine-deuterium aqueous solution, move the RF center to ^{the center frequency between the Ha} and H ^b signals on the benzene ring; first apply a 90° hard pulse with the phase in the x direction to the sample, and then Apply a combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} =30.9mt, the purpose of which is to remove the chemical shift evolution, and then apply

   

   The singlet of the dopamine molecule can be obtained by the pulse of, where τ ₂ =t.8mt; because there is no spin system that is the same as the three hydrogens on the benzene ring in the DA molecule in the mixed system, only the singlet of the DA molecule is prepared; Then apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, and the action time is 1 ms; decoupling pulse power ω _dec ＝550Hz, decoupling time τ _m ＝50ms; apply next

   

   And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals; finally signal acquisition; and/or,

   ^{When the target is the AGG in the 1} H spectrum of a very low-concentration dopamine-deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, the time is τ ₁ =180mt, and the lock frequency ω _SL =8.1Hz lock pulse, the launch center of the lock pulse ^{is the center frequency between the H a} and H ^b signals on the benzene ring; then the z-direction gradient fields g ₁ and g ₂ and the decoupling pulse are applied; the gradient fields g ₁ and The intensity and action time of g ₂ need to be optimized, usually the gradient field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝97Hz, the decoupling time τ _m ＝50ms; the subsequently applied emission center is H on the benzene ring ^{The locking pulse of the center frequency between a} and H ^b signals, the phase is in the x direction, the time is τ ₁ ＝180mt, the locking frequency ω _SL ＝8.1Hz locking pulse; finally data sampling is performed; increasing the number of accumulation of signal acquisition to 4000 Times; and/or,

   When the target is taurine in the ¹ H spectrum of a deuterium taurine aqueous solution, move the RF center to the center frequency between the 1st hydrogen and 2nd hydrogen signals on the methylene group; first apply a phase in the x direction to the sample 90° pulse, then apply the combined pulse of _{τ 1} -π _x -τ _{1 , where τ 1} ＝10mt, apply

   

   After the singlet of the taurine molecule can be obtained by the pulse of τ ₂ =t.8mt; then the z-direction gradient fields g ₁ and g ₂ and decoupling pulse are applied; the intensity and action time of the _{gradient fields g 1} and g _{2 require} Optimization, usually the gradient field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝500Hz, the decoupling time τ _m ＝50ms; subsequently applied

   

   And τ ₁ -π _x -τ ₁ , the purpose is to detect singlet signals; and/or,

   When the target is creatine in the ¹ H spectrum of creatine deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, the time is τ ₁ ＝220mt, and the lock frequency ω _SL ＝18Hz the locking pulse, the center frequency between H ^b, H ^{b 'signal,} thus prepared creatine molecule singlet emission center of the locking pulse; then applying a gradient field in the z direction g ₁ and g ₂ and decoupling pulse ; The intensity and action time of the gradient fields g ₁ and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms; the decoupling pulse power ω _dec ＝70Hz, the decoupling time τ _m ＝50ms; then the phase is applied A lock pulse in the x direction, time τ ₁ =220mt, and lock frequency ω _SL =18Hz; finally data sampling is performed; and/or,

   When the target is acetylaspartic acid in the ¹ H spectrum of acetylaspartic acid deuterium aqueous solution, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction for a time of τ ₁ =105mt locking the frequency ω _SL = 17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA emission center of the locking pulse; then applying a gradient field in the z direction g ₁ And g ₂ and decoupling pulse; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms; the decoupling pulse power ω _dec ＝70Hz, the decoupling time τ _m =50ms; then apply a lock pulse with the phase in the x direction, time τ ₁ =105mt, and lock frequency ω _SL =17.22Hz; finally perform data sampling; and/or,

   When the target is acetyl aspartic acid in the ¹ H spectrum of a mixture of acetyl aspartic acid and mouse brain tissue, first apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction for a time of τ ₁ = _105mt, locking the frequency ω _SL = 17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single molecule state NAA emission center of the locking pulse; then applying a gradient field in the z direction g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 10 Gauss/cm, and the action time is 1 ms; the decoupling pulse power ω _dec ＝90Hz, decoupling Time τ _m =50ms; then apply a lock pulse with phase in the x direction, time τ ₁ =105mt, and lock frequency ω _SL =17.22 Hz; finally, data sampling is performed.
6. A method for realizing magnetic resonance imaging of a target by using a singlet of nuclear spin, characterized in that the method includes:

   Step a: Use the nuclear spin singlet of the target to realize the selection of the molecular signal of the target, including the following steps:

   Step a1: Excite the magnetic resonance signal of the target in the system to be measured by pulse or pulse combination;

   Step a2: preparing a pulse or a combination of pulses by a nuclear spin singlet, and preparing the nuclear spin coupling system of the target into a nuclear spin singlet;

   Step a3: Decoupling the nuclear-spin coupling system of the target through a decoupling pulse, maintaining the nuclear-spin singlet of the target, and dispersing all non-targets in the system under test by applying a pulse gradient field Nuclear spin singlet magnetic resonance signal;

   Step a4: Convert the target nuclear spin singlet into a signal required for magnetic resonance by pulse or pulse combination, so as to achieve selective detection of the target magnetic resonance signal;

   Wherein, the target substance is various substances with a multi-spin coupling system;

   Step b: Perform magnetic resonance imaging on the target signal selected and obtained in step a to obtain the spatial distribution of the target in the observation object.
7. The method according to claim 6, wherein in the step a2, the nuclear-spin coupling system of the target is prepared into the nuclear-spin singlet of the target through a pulse sequence, and the design of the pulse sequence It includes the following steps:

   i. Analyze the target molecule and classify the spin-coupling structure existing in its structure into a strong spin-coupling structure and/or a weak-coupling structure;

   ii. Prepare singlets of respective spin-coupled structures in the target molecule, and compare the preparation efficiency of each singlet;

   iii. Select the spin coupling structure and pulse sequence with the highest singlet preparation efficiency to prepare the nuclear spin singlet of the target.
8. The method according to claim 6, wherein, in the step a3, the way to achieve decoupling includes a spin-locked pulse, or a pulse combination with a specific timing; the decoupling time is selected as the nuclear spin singlet The relaxation time increases with the increase; the decoupling time is longer than the action time of the pulse gradient field; and/or,

   In the step a3, the non-target nuclear spin singlet magnetic resonance signal in the signal from step a2 is diffused by the pulse gradient field, while maintaining the target nuclear spin singlet signal to realize the selectivity of the target signal Observation: The selection effect of target molecule signal is achieved by adjusting the intensity, application times and position of the pulse gradient field.
9. The method according to claim 6, wherein in step a4, different pulses or pulse combinations are selected according to the multi-spin coupling properties of different targets; and/or, in step a4, pulse or The pulse combination converts the singlet signal from step a3 into the signal required for subsequent nuclear magnetic spectroscopy and/or imaging.
10. The method according to claim 6, characterized in that the method is used for early diagnosis and treatment of diseases, evaluation of curative effect, detection of molecular metabolism of drugs in specific organs, detection of molecular distribution of chemical reactions in reaction vessels, and determination of chemical/chemical reaction progress.
11. The method of claim 6, wherein when the target is an acetylaspartic acid molecule, a 90° hard pulse with a phase in the y direction is first applied to the sample, and then a 90° hard pulse with a phase in the x direction and a time of τ _{1 is applied to the sample.} = 105mt, locking the frequency ω _SL = 17.22Hz locking pulse, the center frequency between H ^b, H ^{b 'signal,} in order to produce a single-state molecules of acetyl-aspartate emission center of the locking pulse; then applying z Directional gradient fields g ₁ and g ₂ and decoupling pulses; _{the intensity and action time of gradient fields g 1} and g ₂ need to be optimized, usually the gradient field strength is 5 Gauss/cm, and the action time is 1 ms; decoupling pulse power ω _dec ＝90Hz , Decoupling time τ _m =50ms; then apply a lock pulse with phase in the x direction, time τ ₁ =105mt, and lock frequency ω _SL =17.22Hz; finally, perform frequency encoding in the y direction and phase encoding in the x direction to get the sample Magnetic resonance molecular imaging of middle acetylaspartic acid molecules; and/or,

    When the target is an amino acid molecule, set the RF center as ^{the center frequency between the signals of the amino acid molecule H c} and H ^c' . First apply a 90° hard pulse with the phase in the y direction to the sample, and then apply the phase in the x direction, Change to a lock pulse with τ ₁ = 125mt and lock frequency ω _SL = 18.2 Hz, and then apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; the intensity and action time of _{gradient fields g 1} and g _{2 need to be optimized, usually} The gradient field intensity is 5Gauss/cm, the action time is 1ms; the decoupling pulse power ω _dec ＝90Hz, the decoupling time τ _m ＝50ms; then the applied phase is in the x direction, the time is τ ₁ ＝125mt, the lock frequency ω _SL =18.2 Hz lock pulse; finally, frequency encoding in the y direction and phase encoding in the x direction can obtain the magnetic resonance molecular imaging of the amino acid molecules in the sample.
12. The method according to claim 6, wherein, when the object is dopamine, a radio frequency as the center frequency of the center between the signal molecule dopamine H ^a, H ^b, the first phase 90 is applied to the sample in the y direction °Hard pulse, and then apply a lock pulse whose phase is in the x direction, changed to τ ₁ =180mt, and lock frequency ω _SL =8.1Hz, and then apply z-direction gradient fields g ₁ and g ₂ and decoupling pulses; gradient fields g ₁ and The intensity and action time of g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms; the decoupling pulse power ω _dec =90Hz, the decoupling time τ _m =50ms; the subsequent applied phase is in the x direction, and the time is τ ₁ =180mt, locking frequency ω _SL =8.1Hz locking pulse; finally frequency encoding in the y direction and phase encoding in the x direction can obtain the magnetic resonance molecular imaging of the amino acid molecules in the sample.
13. A method for detecting a target in a designated space by magnetic resonance spectroscopy using nuclear spin singlet selectivity, characterized in that the method comprises:

    Step i: Select the magnetic resonance signal in the designated space by magnetic resonance imaging gradient layer selection technology;

    Step ii: using nuclear spin singlet selectivity to select the signal of the target in the magnetic resonance signal obtained in step i, including the following sub-steps:

    Step ii1: Excite the magnetic resonance signal of the target in the system to be measured by pulse or pulse combination;

    Step ii2: preparing a pulse or a combination of pulses by a nuclear spin singlet, and preparing the nuclear spin coupling system of the target into a nuclear spin singlet;

    Step ii3: Decoupling the nuclear-spin coupling system of the target by decoupling pulses, maintaining the nuclear-spin singlet of the target, and dispersing all non-targets in the system under test by applying a pulse gradient field Nuclear spin singlet magnetic resonance signal;

    Step ii4: Convert the target nuclear spin singlet into a signal required for magnetic resonance by pulse or pulse combination, so as to achieve selective detection of the target magnetic resonance signal;

    Wherein, the target substance is various substances with a multi-spin coupling system;

    Step iii: Convert the signal of the target obtained in step ii into the signal required for magnetic resonance spectroscopy through pulse or pulse combination, and finally obtain the magnetic resonance spectrum of the signal of the target in the designated space.
14. The method according to claim 13, wherein, when the object is an acetyl aspartic acid, as the emission center between the center frequency of the H ^b, H ^{b 'signal,} the locking pulse frequency ω _SL = 17.22Hz , The action time τ ₁ =105mt, _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec ＝90Hz, the decoupling time τ _m =50ms.
15. The method according to claim 13 as duration of action, wherein, when the target molecule is an amino acid, an emission center of H ^c, the center frequency between the H ^{c 'signal,} the locking of the locking pulse frequency ω _SL = 18.2Hz, τ ₁ ＝125mt, _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec ＝90Hz, the decoupling time τ _m ＝50ms .
16. The method according to claim 13, wherein, when the object is dopamine, emission center between the center frequency of H ^a, H ^b signals, locking pulse frequency ω _SL = 8.1Hz, action time τ ₁ =180mt, _{the intensity and action time of the gradient fields g 1} and g ₂ need to be optimized, usually the gradient field intensity is 5 Gauss/cm, the action time is 1 ms, the decoupling pulse power ω _dec =90 Hz, and the decoupling time τ _m =50 ms.
17. The method according to claim 13, wherein in the step ii2, the nuclear spin coupling system of the target is prepared into the nuclear spin singlet of the target through a pulse sequence, and the design of the pulse sequence It includes the following steps:

    ii21. Analyze the target molecule and classify the spin coupling structure existing in its structure into a strong spin coupling structure and/or a weak coupling structure;

    ii22. Prepare singlets of respective spin-coupling structures in the target molecule, and compare the preparation efficiency of each singlet;

    ii23. Select the spin coupling structure and pulse sequence with the highest singlet preparation efficiency to prepare the nuclear spin singlet of the target.
18. The method according to claim 13, characterized in that, in the step ii3, the way to achieve decoupling includes a spin-locked pulse, or a combination of pulses with a specific timing; the decoupling time is selected as the nuclear spin singlet The relaxation time of, increases with the increase; the decoupling time is longer than the action time of the pulse gradient field; and or,

    In the step ii3, the non-target nuclear spin singlet magnetic resonance signal in the signal from step ii2 is diffused by the pulse gradient field, while maintaining the target nuclear spin singlet signal to realize the selectivity of the target signal Observation: The target molecular signal selection effect is achieved by adjusting the intensity, application times and position of the pulse gradient field.
19. The method according to claim 13, wherein in step ii4, different pulses or pulse combinations are selected according to the multi-spin coupling properties of different targets; and/or, in step ii4, pulse or The pulse combination converts the singlet signal from step ii3 into the signal required for subsequent nuclear magnetic spectroscopy and/or imaging.
20. The method of claim 1, 6, 13, wherein the target substance comprises dopamine, taurine, acetyl aspartic acid, AGG, hypotaurine, creatine, choline chloride, glucose , Glutathione.

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