CN113030815A

CN113030815A - Method for magnetic resonance spectrum detection of target object in designated space by utilizing nuclear spin singlet selectivity

Info

Publication number: CN113030815A
Application number: CN201911249153.9A
Authority: CN
Inventors: 姚叶锋; 辛家祥; 李毅; 魏达秀; 王嘉琛
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2019-12-09
Filing date: 2019-12-09
Publication date: 2021-06-25

Abstract

The invention discloses a method for carrying out magnetic resonance spectrum detection on a target object in a designated space by utilizing nuclear spin singlet selectivity, which selects a magnetic resonance signal in the designated space through a magnetic resonance imaging gradient layer selection technology; selecting a signal of a target object in the magnetic resonance signal obtained in the step i by utilizing the nuclear spin singlet selectivity; the method for detecting the target object by utilizing the nuclear spin singlet state selectivity has good precision, sensitivity and selectivity, can eliminate the interference of signals of other substances, accurately detects and obtains the signal of the target object molecule from a system with complex components, and has important application value in the fields of biology, medicine, chemistry, chemical engineering and the like.

Description

Method for magnetic resonance spectrum detection of target object in designated space by utilizing nuclear spin singlet selectivity

Technical Field

The invention belongs to the field of magnetic resonance detection, and particularly relates to a method for performing magnetic resonance spectrum detection on a target object in a specified space by utilizing nuclear spin singlet selectivity.

Background

The principle of Magnetic Resonance Imaging (MRI) and spectroscopy (MRS) is to excite nuclear spins under the action of an external magnetic field with a radio-frequency signal of a certain frequency, thereby generating a resonance signal. Modern MRI and MRS have developed into a very powerful medical diagnostic means, particularly adapted to diagnostic tests and scientific studies of brain tissue, nervous system, and human soft tissue. One core technique in MRI and MRS is the pulse sequence. A pulse sequence refers to a pulse or combination of pulses designed for a particular purpose. The control of the nuclear spins in the object to be examined and the generation of the desired magnetic resonance signals can be achieved by means of a pulse sequence. And collecting the magnetic resonance signals of the object to be detected, and carrying out corresponding data processing to obtain the MRI and MRS of the object to be detected.

Conventional MRI and MRS are often observations of proton nuclear spins in an analyte. If the observed object is a living organism, the signal source is mainly water molecules in the living organism. Due to the different content of water molecules in different parts and organs of the organism, normal tissues and lesions, or different molecular relaxation properties. Medical diagnosis of MRI is usually based on these differences in water molecule properties. Unlike MRI, MRS uses MRI to select a specific part of an organism to be measured, and then performs magnetic resonance spectroscopy on the selected part. In principle, MRS can detect biochemical molecules including water, fat, various amino acids, and glucose in an organism. However, due to the diverse structures of various biochemical molecules and the complex environment in the organism, the signal of MRS is usually very complex, and the signals of different biochemical molecules are overlapped seriously. Traditional MRS techniques often fail to achieve selective observation of specific molecules.

Disclosure of Invention

To overcome the above-mentioned drawbacks of the prior art, the present invention provides a method for selectively detecting a target using a nuclear spin singlet state. The nuclear spin singlet is a special spin state of the nuclear spin coupled regime. This state has several characteristics: 1. the nuclear spin singlet state can be prepared by a reasonably designed pulse sequence; 2. preparing a nuclear spin singlet pulse sequence related to the chemical structure of the molecule, wherein different molecular structures correspond to different nuclear spin singlet pulse sequences; 3. the spin state does not evolve under the action of the pulse gradient field.

Based on the characteristics, the invention designs a series of nuclear spin based singlet magnetic resonance pulse sequences. The core design idea of the pulse sequences is that the characteristic that the nuclear spin singlet state is not influenced by a pulse gradient field is utilized, after the nuclear spin singlet state of the target nuclear spin coupling system is prepared, the pulse gradient field is applied to the target to diffuse other magnetic resonance signals except the nuclear spin singlet state of the target, and the nuclear spin singlet signal of the target is kept, so that the nuclear magnetic signal of the target is selectively detected. The method has good accuracy, sensitivity, reproducibility and selectivity, can eliminate the interference of signals of other substances, accurately detects the signals of the target molecules from a system with complex components, has important application value in the fields of biology, medicine, chemistry, chemical industry and the like, and is a novel original technology.

The characteristic that the preparation pulse sequence of the nuclear spin singlet state corresponds to the chemical structure of the molecule is utilized, and the preparation pulse sequence of the nuclear spin singlet state can select the signal of a specific target molecule. The target molecules are generally various types of compound molecules having a spin-coupled system (nuclear spin number > ═ 2). In general, compound molecules with multiple spin-coupled systems can be used to prepare singlet states and perform selective observation. The chemical structure requirements of such molecules are: the nuclear magnetic resonance imaging system is provided with at least one pair of nuclear spins of the same kind which are mutually coupled, a certain chemical shift difference exists between the nuclear spins, and the chemical shift and the coupling constant are stable and cannot change along with the change of external environments (such as temperature, PH value and the like). 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 multi-spin coupling system of the target. The design of the nuclear spin singlet preparation pulse is well known in the art. In general, the chemical shift of the respective spins in the spin-coupled system (nuclear spin number > ═ 2) and the J-coupling between the spins are key parameters for the preparation of the nuclear spin singlet pulse sequence. According to different properties of a spin coupling system, the design of the nuclear spin singlet preparation pulse needs to be correspondingly adjusted. Weak spin-coupled systems (j.am. chem. soc.126(2004), 6228-.

Preferably, the target is a dopamine molecule (formula (1)). In this molecule, H_a，H_bAnd H and_dforming a three spin coupling system. Chemical shift of each spin (omega) in the system_xX ═ a, b, d) and J coupling (J)_ab,J_ad,J_bd) As follows (in (ω)_a+ω_d) And/2 is the radio frequency transmission center): omega_a＝36.5Hz，ω_b＝-36.5Hz，ω_c＝-7.8Hz，J_ab＝8.14Hz，J_ad＝0Hz，J_bd2.18 Hz. Based on these properties of the spin-coupled system, a design to prepare a singlet pulse sequence can be made.

In the present invention, preferably, the target may further include dopamine, taurine, acetyl aspartic acid, AGG, hypotaurine, creatine, choline chloride, glucose, glutathione, or the like.

Specifically, the implementation process of the method comprises the following steps:

step 1: exciting a magnetic resonance signal of the target object (molecule) in a system to be detected through pulse or pulse combination;

step 2: selecting a pulse or a pulse combination according to the multi-spin coupling property of the target object, and preparing a nuclear spin singlet state of a nuclear spin coupling system of the target object through the pulse or the pulse combination;

and step 3: decoupling a nuclear spin coupling system of a target object within a certain time through decoupling pulses (pulses or pulse combinations), keeping the nuclear spin singlet state of the target object, and diffusing all non-target object nuclear spin singlet state magnetic resonance signals in the system to be detected by applying a pulse gradient field within the time;

and 4, step 4: the nuclear spin singlet state of the target object is converted into a signal required by magnetic resonance, such as a nuclear magnetic spectrum signal or an imaging signal, through the pulse or the pulse combination, so that the nuclear magnetic signal of the target object is selectively detected.

Wherein the target is various substances with a multi-spin coupling system.

The main purpose of said step 2 is to prepare the nuclear spin singlet state. According to the specific spin coupling characteristics of the target system, the nuclear spin singlet state of the target is prepared through a reasonably designed pulse or pulse combination sequence. The design steps are briefly described as follows: i. analyzing target molecules, and distinguishing spin coupling structures existing in the structures of the target molecules into strong spin coupling structures and/or weak spin coupling structures; ii. Preparing the single states of respective spin-coupled structures in target molecules, and comparing the preparation efficiency of each single state; and iii, selecting a spin coupling structure with highest singlet state preparation efficiency and a pulse sequence for selectively detecting target molecules in the sequence shown in the figure 1.

The pulse or combination of pulses includes an excitation pulse and a nuclear spin singlet preparation pulse. The excitation pulse is used for exciting nuclear spin signals, parameters such as form, intensity and the like of the nuclear spin signals can be adjusted according to experimental requirements, and the parameters are usually hard pulses with high power, wherein the power of the pulses can be adjusted according to a specific molecular system, and the requirements are that a nuclear spin system of a target object can be excited uniformly, and the influence of relaxation is reduced as much as possible. The nuclear spin singlet state preparation pulse has the function of preparing the nuclear spin singlet state, and the nuclear spin singlet state is not dispersed by a pulse gradient fieldThe signal selection is performed. There are various schemes for nuclear spin singlet preparation pulses. For example, the pulses shown in fig. 5 are SLIC pulses (s.j. devince, r.l. walsworth, m.s. rosen, phys.rev. lett.111(2013)173002 (1-4)), in which the power and application time τ of the spin-lock pulse_SLDepending on the chemical shift differences between the nuclear spins and the coupling constants, the application of spin lock pulses requires the center frequency to be aligned to a particular nuclear spin. In addition to SLIC pulses, other pulses for preparing nuclear spin singlet are equally suitable for use in the present invention, such as M2S pulses for nuclear spin systems with similar chemical shifts (g.pileio, m.carravetta and m.h.levitt, proc.natl.acad.sci.u.s.a.,2010,107, 17135-.

In step 3, the step contains two key components: 1. decoupling the pulses; 2. a pulsed gradient field. The effect of the decoupling pulse is to maintain the nuclear spin singlet state of the target. The decoupling pulses need to be designed according to the chemical shift and J-coupling of the multi-spin coupled system of the object. The decoupled pulses may be in the form of continuous pulsed illumination, or a combination of pulses with a specific timing. The action time of the decoupling pulses can be adjusted according to the properties of the system, and the specific time needs to be measured experimentally, namely experimentally by varying the time of the decoupling pulses, and observing the signal intensity and selectivity using the singlet state, thereby determining the optimal 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, decoupling the nuclear spin coupling system of the target object through decoupling pulses so as to keep the nuclear spin singlet state of the target object; the way in which decoupling is achieved can be by continuous wave decoupling, or pulse combinations with specific timing. Continuous wave decoupling and pulse combining decoupling are well known in the art. The decoupling time increases with the relaxation time of the singlet state of the nuclear spin, generally in the order of milliseconds to seconds, and can be adjusted according to the properties of the system to obtain the best effect. The decoupling time needs to be longer than the action time of the pulse gradient field.

In step 3, the pulse gradient field has the following functions: and dispersing all other non-nuclear spin singlet nuclear magnetic signals except the nuclear spin singlet state of the target object. The action effect of the pulse gradient field can be adjusted and optimized by adjusting the strength, the application times, the position and the like of the pulse gradient field. The application time is millisecond magnitude, the power of the pulse gradient field can be adjusted according to the diffusion effect of the pulse gradient field on signals, and the direction of the pulse gradient field is in the same direction with the direction of the z axis of the static magnetic field. The optimal effect of the pulsed gradient field is to retain only the signal of the singlet state.

In the pulse sequence of fig. 1, the above-mentioned pulsed gradient field is applied twice. In step 3, the decoupling pulses may also be applied alone, without applying a pulsed gradient field. However, in this method, although a certain degree of signal selection can be achieved, the overall effect is poor. In step 3, if a pulse gradient field is applied alone, and no decoupling pulse is applied, the purpose of target molecule signal selection cannot be achieved.

In step 4, the object nuclear spin singlet state is converted into a signal required by a subsequent magnetic resonance experiment, such as a nuclear magnetic spectrum signal or an imaging signal, through a pulse or a pulse combination, and the selection and the design of the pulse or the pulse combination are similar to those of the pulse or the pulse combination in step 2, namely different pulses or pulse combinations are selected according to the multi-spin coupling properties of different objects, and the object nuclear spin singlet state is converted into the signal required by the subsequent magnetic resonance experiment.

In addition, the invention also comprises the following basic steps: (1) obtaining chemical shift difference and coupling constant between target object spins by a traditional nuclear magnetic resonance measurement method; (2) designing a pulse sequence through the chemical shift difference and the coupling constant of a coupling system, and determining the power and the pulse width of the spin locking pulse generating the singlet state; (3) the designed pulse sequence is implemented on the magnetic resonance apparatus. These are well known in the art.

The pulse sequence of fig. 5 shows a specific example of the implementation of the above steps. Fig. 5 is a schematic diagram of a pulse sequence. The evolution process of the sequence to the spin state is as follows in sequence: 90 degree RF at AThe pulse rotates the longitudinal magnetization vector from the longitudinal axis to the x, y plane; the spin locking pulse at the position B generates spin singlet state in the state of the system after being applied; the subsequent gradient pulse g₁Observable states other than spin singlet can be eliminated; during the application of the decoupling pulse at C, spin singlet state is preserved, and other signals are attenuated under the influence of relaxation; followed by a second gradient pulse g₂Further elimination of signals other than spin singlet, finally application of τ at D_SLThe pulse converts spin singlet state into observable signal to realize signal detection.

When the target is AGG deuterium aqueous solution¹In the case of AGG in the H spectrum, a hard pulse of 90 DEG is applied with a phase in the y direction, and then an emission center of H is applied^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁With a locking frequency of ω_SLThe locking pulse of (a) produces a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupled pulses omega_dec(ii) a Subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁With a locking frequency of ω_SLThe lock pulse of (1); and finally, carrying out data sampling. Preparation H^b，H^b’Lock pulse duration tau for singlet state₁80ms, lock frequency ω_SL17.2Hz, preparation H^c，H^c’Lock pulse duration tau for singlet state₁125ms, lock frequency ω_SL18.5 Hz. Decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms.

When the target is a mixture of AGG and leucine, glutamic acid and glycine, namely deuterium aqueous solution¹In the case of AGG in the H spectrum, a 90 DEG hard pulse having a phase in the y direction is applied to a sample, and then a hard pulse having a phase in the x direction is applied for a time τ₁125ms, lock frequency ω_SL18.5Hz lockA fixed pulse having a center of emission of the lock pulse of H^b，H^b’Sum of signals H^c，H^c’The center frequency between the signals, thereby producing a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms; subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁125ms, lock frequency ω_SL18.5Hz lock-in pulse; and finally, carrying out data sampling.

When the target is a deuterium aqueous solution of a mixture of AGG and insulin¹In the case of AGG in the H spectrum, a 90 DEG hard pulse having a phase in the y direction is applied to a sample, and then a hard pulse having a phase in the x direction is applied for a time τ₁125ms, lock frequency ω_SL18.5Hz lock-in pulse with a center of transmission H^b，H^b’Sum of signals H^c，H^c’The center frequency between the signals, thereby producing a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms; subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁125ms, lock frequency ω_SL18.5Hz lock-in pulse; and finally, carrying out data sampling.

When the target is dopamine deuterium aqueous solution¹When dopamine in H spectrum, the radio frequency center is moved to H on benzene ring^aAnd H^bCenter frequency between signals; the sample is first subjected to a 90 hard pulse in the x-direction and then to tau₁-π_x-τ₁In which τ is₁30.9ms, the purpose of which is to remove the chemical shift evolution, followed by application

Can obtain a singlet state of the dopamine molecule, wherein tau₂6.8 ms; because a spinning system which is the same as three hydrogen on a benzene ring in the DA molecule does not exist in the mixed system, only the singlet state of the DA molecule is prepared; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec550Hz, decoupling time tau_m50 ms; is then applied

And τ₁-π_x-τ₁For detecting a singlet signal; and finally, signal acquisition is carried out.

When the target is a very low-concentration dopamine deuterium aqueous solution¹In the case of AGG in the H spectrum, a 90 DEG hard pulse having a phase in the y direction is applied to a sample, and then a hard pulse having a phase in the x direction is applied for a time τ₁180ms, lock frequency ω_SL8.1Hz lock pulse, which is emitted with H on the benzene ring as the center^aAnd H^bCenter frequency between signals; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec97Hz, decoupling time tau_m50 ms; followed by application of H on the benzene ring as the emission center^aAnd H^bLocking pulses of central frequency between signals, phase in x direction, time tau₁180ms, lock frequency ω_SLLock pulse at 8.1 Hz; finally, data sampling is carried out; and increasing the accumulation times of signal acquisition to 4000 times.

When the target is taurine deuterium oxideSolutions of¹When taurine is contained in the H spectrum, the radio frequency center is shifted to the center frequency between the No. 1 hydrogen signal and the No. 2 hydrogen signal on methylene; the sample is first pulsed 90 DEG in phase in the x-direction and then tau₁-π_x-τ₁In which τ is₁10ms, apply

Can obtain the singlet state of the taurine molecule, wherein tau₂6.8 ms; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec500Hz, decoupling time tau_m50 ms; subsequent application of

And τ₁-π_x-τ₁For detecting a singlet signal.

When the target is creatine deuterium aqueous solution¹When creatine is contained in H spectrum, a 90 DEG hard pulse with the phase in the y direction is firstly applied to a sample, and then a phase in the x direction is applied for a time tau₁220ms, lock frequency omega_SL18Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing a singlet state of the creatine molecule; then applying a gradient field g in z direction₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec70Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁220ms, lock frequency omega_SL18Hz lock-in pulse; and finally, carrying out data sampling.

When the target is aqueous solution of deuterium aspartate¹When the acetyl aspartic acid in the H spectrum is used, a 90-degree hard pulse with the phase in the y direction is firstly applied to the sample, and then the hard pulse is appliedPhase in x direction and time tau₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the NAA molecule; then applying a gradient field g in z direction₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec70Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; and finally, carrying out data sampling.

When the target is mixture of acetyl aspartic acid and mouse brain tissue¹When the acetyl aspartic acid in the H spectrum is in use, a 90 DEG hard pulse with the phase in the y direction is firstly applied to a sample, and then a hard pulse with the phase in the x direction and the time tau is applied₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the NAA molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 10Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; and finally, carrying out data sampling.

The invention also provides a method for realizing magnetic resonance imaging of the target object by utilizing the nuclear spin singlet state, the target object is prepared into the nuclear spin singlet state by the method for selectively detecting the target object by utilizing the nuclear spin singlet state, and the signal of the target object is further selected, so that the magnetic resonance imaging of the target object is realized on the basis. The method comprises the following steps:

step a: the target is prepared into a nuclear spin singlet state by the method for selectively detecting the target by utilizing the nuclear spin singlet state, then the selection of the target signal is realized by a pulse gradient field and a decoupling pulse, and finally the nuclear spin singlet signal of the target is converted into a signal required by a subsequent step by a proper pulse or a proper pulse combination.

Step b: the main components are various magnetic resonance imaging pulse sequences; and d, imaging the target object signal obtained in the step a according to the actual imaging requirement, and realizing the magnetic resonance imaging of the target object.

In the step b, magnetic resonance imaging is carried out by using the signal of the target object obtained in the step a, so that a molecular magnetic resonance image of the target object is obtained. Different magnetic resonance imaging pulse sequences can be adopted in the step b according to the needs, and the method for obtaining the magnetic resonance imaging pulse sequences is a method known in the field.

The magnetic resonance imaging of the specific target molecules realized by the method can be applied in many fields, and is used for early diagnosis and treatment of diseases, curative effect evaluation, specific organ drug molecule metabolism detection, chemical reaction molecule distribution detection in a reaction container, chemical/chemical reaction process determination and the like. For example, in medical applications, if the target is a highly expressed molecule of a disease, the method can be used as a means for early diagnosis and treatment of the disease and evaluation of therapeutic effects. In the pharmaceutical field, if the target is a drug molecule, the method can be used as a means for detecting the metabolism of the drug molecule in a specific organ. In chemical/chemical engineering, if the target is a chemically reactive molecule, the method can be used as a distribution of chemically reactive molecules in a reaction vessel to detect the progress of a chemical/chemical reaction.

The pulse sequence of fig. 6 gives a specific example of the implementation of the above steps. Fig. 6 is a schematic diagram of a pulse sequence. The evolution process of the sequence to the spin state is as follows in sequence: the 90-degree radio frequency pulse at A rotates the longitudinal magnetization vector from the longitudinal axis to the x and y planes; the spin locking pulse at the position B generates spin singlet state in the state of the system after being applied; the subsequent gradient pulse g₁Observable states other than spin singlet can be eliminated; spin singlet is preserved during application of decoupling pulses at C, and other informationThe signal decays under the influence of relaxation; followed by a second gradient pulse g₂Further elimination of signals other than spin singlet, finally application of τ at D_SLThe pulse converts the spin singlet state into a signal required for subsequent imaging experiments. And finally, the three-dimensional imaging pulse sequence realizes molecular imaging of the target molecules.

When the target is an acetoaspartic acid molecule, a 90 DEG hard pulse with the phase in the y direction is firstly applied to the sample, and then a hard pulse with the phase in the x direction and the time tau is applied₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the acetoacetic acid molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; finally, the magnetic resonance molecular imaging of the acetyl aspartic acid molecules in the sample can be obtained by carrying out frequency encoding in the y direction and phase encoding in the x direction.

When the target is an amino acid molecule, the radio frequency center is defined as the amino acid molecule H^c,H^c’The sample is first applied with a 90 deg. hard pulse in the y-direction and then with a phase in the x-direction, modified to tau₁125ms, lock frequency ω_SL18.2Hz lock-in pulse, and then a z-direction gradient field g is applied₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁125ms, lock frequency ω_SL18.2Hz lock-in pulse; finally, the frequency coding in the y direction and the phase coding in the x direction are carried outThe code allows magnetic resonance molecular imaging of the amino acid molecules in the sample.

When the target is dopamine, the radio frequency center is defined as dopamine molecule H^a,H^bThe sample is first applied with a 90 deg. hard pulse in the y-direction and then with a phase in the x-direction, modified to tau₁180ms, lock frequency ω_SLA lock-in pulse of 8.1Hz, followed by a z-direction gradient field g₁And g₂And decoupling the pulses; gradient field g₁And g₂The intensity and the action time of the magnetic field are required to be optimized, the gradient field intensity is 5Gauss/cm usually, and the action time is 1 ms; decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁180ms, lock frequency ω_SLLock pulse at 8.1 Hz; and finally, carrying out frequency coding in the y direction and phase coding in the x direction to obtain magnetic resonance molecular imaging of the amino acid molecules in the sample.

The invention also provides a method for detecting the magnetic resonance spectrum of the target object in the designated space by utilizing the nuclear spin singlet selectivity, which selects the magnetic resonance signal in the designated space through the magnetic resonance imaging layer selection technology, selects the signal of the target object in the magnetic resonance signal in the designated space by utilizing the nuclear spin singlet selectivity on the basis of the method for detecting the target object by utilizing the nuclear spin singlet selectivity, and finally realizes the magnetic resonance spectrum of the signal of the target object in the designated space.

Specifically, the method comprises the following steps:

step i: selecting a magnetic resonance pulse sequence with a layer selection function, and realizing selection of magnetic resonance signals in a designated space through a magnetic resonance imaging gradient layer selection technology;

step ii: selecting a target object signal in the magnetic resonance signals obtained in the step i by utilizing the nuclear spin singlet selectivity; selecting different magnetic resonance pulse sequences for preparing nuclear spin singlet state according to specific spin coupling characteristics of a target system; the method comprises the following substeps:

step ii 1: exciting a magnetic resonance signal of a target object in a system to be detected through pulse or pulse combination;

step ii 2: preparing a nuclear spin singlet state from a nuclear spin coupling system of the target by a nuclear spin singlet state preparation pulse or a pulse combination;

step ii 3: decoupling a nuclear spin coupling system of a target object through decoupling pulses, keeping the nuclear spin singlet state of the target object, and diffusing all non-target object nuclear spin singlet state magnetic resonance signals in the system to be detected by applying a pulse gradient field;

step ii 4: converting the nuclear spin singlet state of the target object into a signal required by magnetic resonance through pulse or pulse combination, and realizing selective detection of the magnetic resonance signal of the target object;

wherein the target is various substances with a multi-spin coupling system;

step iii: converting the signal obtained in step ii into a detectable signal and detecting.

The magnetic resonance spectrum of the specific target object molecules in the designated space realized by the method can be applied in a plurality of fields, and can be used for early diagnosis and treatment of diseases, curative effect evaluation, specific organ drug molecule metabolism detection, chemical reaction molecule distribution detection in a reaction container, and the like. For example, in the medical field, if the target is a disease-highly expressed molecule, the method may select a signal of a specific site of an organism using MRI, and then observe the disease-highly expressed molecule by signal selection. The method can be used as a means for early diagnosis and treatment of diseases and evaluation of curative effect. In the pharmaceutical field, if the target is a drug molecule, the method can be used as a means for detecting the metabolism of the drug molecule in a specific organ. In chemical/chemical engineering, if the target is a chemically reactive molecule, the protocol can be used as a distribution of chemically reactive molecules within a reaction vessel to detect the progress of a chemical/chemical reaction.

In the present invention, the method for 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 the layer selection function can be selected according to actual requirements. The designated space in step i refers to a position of a specific part of the observation target in the space.

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

In the present invention, in the step iii, a process of converting the signal obtained in the step ii into an observable signal by designing a pulse or a combination of pulses according to actual requirements may be performed.

The pulse sequence of fig. 7 gives a specific example of the implementation of the above steps. Fig. 7 is a schematic diagram of a pulse sequence. The evolution process of the sequence to the spin state is as follows in sequence: the 90-degree radio frequency pulse at A rotates the longitudinal magnetization vector from the longitudinal axis to the x and y planes; the waveform pulse and the matched gradient pulse g at E_zRealizing specific spatial position signal selection; then, a spin-locking pulse at the position B generates a spin singlet state in the state of the system after being applied; the subsequent gradient pulse g₁Observable states other than spin singlet can be eliminated; during the application of the decoupling pulse at C, spin singlet state is preserved, and other signals are attenuated under the influence of relaxation; followed by a second gradient pulse g₂Further elimination of signals other than spin singlet, finally application of τ at D_SLThe pulse converts the spin singlet state into a signal required for subsequent MRS experiments. And finally, observing the signal to realize the MRS spectrogram of the specific molecule in the specific space.

When the target is acetyl aspartic acid, the emission center is H^b，H^b’Center frequency between signals, lock frequency omega of lock pulse_SL17.22Hz, duration of action τ₁105ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

When the target is an amino acid molecule, the emission center is H^c，H^c’Center frequency between signals, lock frequency omega of lock pulse_SL18.2Hz, duration of action τ₁125ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

The emission center is H^a,H^bCenter frequency between signals, lock frequency omega of lock pulse_SL8.1Hz, time of action τ₁180ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

The invention has the beneficial effects that: one of the significant features and innovations of the present invention, which is different from other magnetic resonance imaging and spectroscopy techniques in the past, is that magnetic resonance imaging and spectroscopy of specific molecules can be realized. The realization of this feature and innovation is based on the innovative utilization of nuclear spin singlet. The invention utilizes the characteristic that the nuclear spin singlet state is not influenced by a pulse gradient field for the first time and the specific selectivity to the molecular structure in the preparation process of the nuclear spin singlet state, thereby realizing the magnetic resonance signal selection of specific molecules and applying the magnetic resonance signal selection to magnetic resonance imaging and spectrum. In the application of magnetic resonance imaging, the invention can really realize the magnetic resonance imaging of specific molecules. In the application of magnetic resonance spectroscopy, the invention can observe the magnetic resonance spectroscopy of specific molecules in the designated part of the object to be detected, and thereby realize the determination of the spatial distribution of the specific molecules in the object to be detected. The method or variants thereof can be combined with existing magnetic resonance imaging and spectroscopy to derive more magnetic resonance molecular imaging and spectroscopy techniques.

The method is based on the magnetic resonance technology, and has the characteristics of the conventional magnetic resonance technology, as well as good precision, sensitivity and molecular signal selectivity. The interference of signals of other substances can be simply, conveniently and effectively eliminated under the condition of not damaging a sample or changing the properties of the sample, and the signals of the target molecules can be accurately detected and obtained from a system with complex components. For example, the method can be used to monitor the content and distribution of endogenous targets in an organism without the need to inject exogenous probe molecules into the organism. Therefore, the target object can be detected on the basis of no damage to tissues and cells; the method may also be used to monitor the content and distribution of target molecules in a chemical reactor. The signal of the target object in the chemical reactor can be detected under the condition of not destroying or interfering the chemical reaction, so that the observation of the chemical reaction process is realized. Meanwhile, the method can be combined with some exogenous targeting probe molecules, and the content and distribution detection of the targeting probe molecules in the observed object is realized by preparing the monomorph of the targeting probe molecules.

The method has important application value in the fields of biology, medicine, chemistry, chemical industry, industrial production and the like.

Drawings

Fig. 1 is a schematic diagram of a magnetic resonance pulse sequence for selectively detecting target molecules by using a nuclear spin singlet state. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_zRepresenting the z-direction pulse gradient channel.

Fig. 2 is a schematic diagram of a three-dimensional imaging sequence based on a single-state filtering. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_x,G_yAnd G and_zrespectively representing the pulse gradient channels in the x, y and z directions.

Figure 3 is a schematic representation of an MRS sequence implementing magnetic resonance signal selection using nuclear spin singlet. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_x,G_yAnd G and_zrespectively representing the pulse gradient channels in the x, y and z directions.

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

Figure 5 is a schematic diagram of a pulse sequence for selecting a particular molecular magnetic resonance signal based on spin-lock preparation of nuclear spin singlet states. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_zRespectively, the pulse gradient channels in the z-direction. Wherein the black rectangle at A represents the 90 pulse, 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, g₁And g₂Representing a gradient pulse. Omega_SLAnd τ_SLFor spin-lock pulsesPower and time of action, omega_decAnd τ_mTo decouple the power and the duration of the pulse.

Fig. 6 is a pulse sequence for magnetic resonance molecular imaging based on spin-locking preparation of nuclear spin singlet. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_xAnd G_yRepresenting the pulse gradient channels in the x and y directions, respectively. Wherein the black rectangle at A represents the 90 pulse, 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, g₁，g₂，g₃And g₄Representing a gradient pulse. Omega_SLAnd τ_SLApplying power and time, omega, to the spin-lock pulse_decAnd τ_mTo decouple the power and the duration of the pulse.

Fig. 7 is a MRS pulse sequence for preparing a nuclear spin singlet state based on spin locking. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_zRepresenting the z-direction pulse gradient channel. Wherein the black rectangle at A represents the 90 pulse, 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 multi-lobe shape at E represents the layer-selection pulse, g₁，g₂And g_zRepresenting a gradient pulse. Omega_SLAnd τ_SLFor spin lock pulse duration, ω_decAnd τ_mTo decouple the power and the duration of the pulse.

Fig. 8 is a schematic diagram of a pulse sequence for selecting a specific molecular magnetic resonance signal based on a multi-pulse technique for preparing a nuclear spin singlet state. Wherein the content of the first and second substances,¹h represents a hydrogen channel, G_zRespectively, the pulse gradient channels in the z-direction. Wherein the black rectangle at A represents a 90 degree pulse, the box at B represents a 180 degree pulse, the black rectangle at C represents a 90 degree pulse, the box at D represents a decoupled pulse, the box at E represents a 90 degree pulse, the box at F represents a 180 degree pulse, g₁And g₂Representing a gradient pulse. Tau is₁And τ₂Representing the time interval between pulses. Omega_decAnd τ_mPower and time are applied to decouple the pulses.

FIG. 9 is a diagram of: a) single pulse of aqueous AGG deuterium solution¹H spectrum; based on the preparation of nuclear spin singlet state, the implementation of specific molecule AGG molecule b) H^b,H^b’A group and c) H^c,H^c’And (3) selectively observing a group magnetic resonance signal.

FIG. 10 is a diagram: a) single pulse of aqueous deuterium solution of mixture of AGG and leucine, glutamic acid and glycine¹H spectrum; b) implementation of AGG molecule H based on preparation of nuclear spin singlet^c,H^c’And (3) selectively observing a group signal.

FIG. 11 is a diagram of: a) single pulse of deuterium aqueous solution of mixture of AGG and insulin¹H spectrum; b) implementation of AGG molecule H based on preparation of nuclear spin singlet^c,H^c’And (3) selectively observing a group signal.

FIG. 12 is a diagram: a) single pulse of DA deuterium aqueous solution¹H spectrum; b) realization of DA molecule H based on preparation of nuclear spin singlet^a,H^bAnd (3) selectively observing a group signal.

FIG. 13 is a graph of: a) single pulse of DA deuterium aqueous solution¹H spectrum, wherein the mass fraction of DA is 0.0006%; b) realization of DA molecule H based on preparation of nuclear spin singlet^dAnd (3) selectively observing a group signal.

FIG. 14 is a graph of: a) taurine deuterium aqueous solution monopulse¹H spectrum; b) based on the preparation of nuclear spin singlet state, a spectrogram for selectively observing

taurine molecule

1 and 2 group signals is realized.

FIG. 15 is a schematic diagram of: a) creatine deuterium aqueous solution monopulse¹H spectrum; b) implementation of creatine pair molecule H based on preparation of nuclear spin singlet^b,H^b’And (3) selectively observing a group signal.

FIG. 16 is a graph showing: a) single pulse of aqueous NAA deuterium solution¹H spectrum; b) realization of NAA molecular H based on preparation of nuclear spin singlet^b,H^b’And (3) selectively observing a group signal.

FIG. 17 is a graph of: a) single pulse of NAA and mouse brain tissue mixture¹H spectrum; b) realization of NAA molecular H based on preparation of nuclear spin singlet^b,H^b’And (3) selectively observing a group signal.

FIG. 18 is a graph of: a) photographs and schematic representations of sample objects. The samples were: a glass nuclear magnetism sample tube with the inner diameter of 4mm is stored with mixed water of 60 percent water and 40 percent deuterium water, 4 small glass tubes with the outer diameter of 0.9mm are arranged in the glass nuclear magnetism sample, and the glass nuclear magnetism sample tube respectively contains NAA deuterium water solution with the mass fraction of 24 percent, AGG deuterium water solution with the mass fraction of 11.2 percent, mixed water of 40 percent water and 60 percent deuterium water and DA deuterium water solution with the mass fraction of 10 percent. b) Spin echo imaging images of the sample; c) magnetic resonance molecular imaging of NAA molecules; d) magnetic resonance molecular imaging of AGG molecules; e) magnetic resonance molecular imaging of DA molecules.

FIG. 19 is a graph of: a) testing a spin echo imaging image of the sample, wherein a white frame represents a signal selection area in a selected layer; b) a conventional MRS spectrogram of a white frame selection region; c) AGG molecule MRS spectrogram; d) NAA molecular MRS spectrogram; e) DA molecular MRS spectrum. The sample was the same as the sample of example 10, and was: a glass nuclear magnetism sample tube with the inner diameter of 4mm is stored with mixed water of 60 percent water and 40 percent deuterium water, 4 small glass tubes with the outer diameter of 0.9mm are arranged in the glass nuclear magnetism sample, and the glass nuclear magnetism sample tube respectively contains NAA deuterium water solution with the mass fraction of 24 percent, AGG deuterium water solution with the mass fraction of 11.2 percent, mixed water of 40 percent water and 60 percent deuterium water and DA deuterium water solution with the mass fraction of 10 percent.

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

FIG. 21 is a flow chart of the method for selectively detecting a target object by using a nuclear spin singlet state according to the present invention.

Fig. 22 is a flow chart illustrating a method for implementing magnetic resonance imaging of an object by using a nuclear spin singlet state according to the present invention.

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

Detailed Description

The invention is further described in detail with reference to the following specific examples and the accompanying drawings. The procedures, conditions, experimental methods and the like for carrying out the present invention are general knowledge and common general knowledge in the art except for the contents specifically mentioned below, and the present invention is not particularly limited.

The main step flow of the embodiment is shown in fig. 20:

1. the spin system can be roughly divided into a strongly coupled system and a weakly coupled system. According to different properties of a spinning system, the corresponding pulse sequence also needs to be adjusted;

2. parameters in the pulse sequence are closely related to the molecular characteristics of the sample, and experimental parameters in the pulse sequence need to be optimized for obtaining a better signal selection effect;

3. the target molecule signal can be observed as desired.

In the examples there is a sample formulation. The configuration methods and steps are well known in the art.

Example 1-L-Alanine-glycine (AGG) aqueous deuterium solution¹Selection of AGG Nuclear magnetic signals in H Spectrum

Experimental samples: amino acid molecule, L-Alanine-glycine (AGG) soluble in D₂And O, preparing an AGG deuterium aqueous solution with the mass fraction of 0.6%.

The measuring instrument: BrukeraVANCE III 500MHz NMR spectrometer. The spectrometer is provided with gradient power amplifiers in 3 directions. The probe is a 5mm liquid probe with 3 gradient coils.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. Using the pulse sequence shown in FIG. 5, a 90 hard pulse with a phase in the y-direction was applied to the sample, followed by an emission center H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁With a locking frequency of ω_SLThe locking pulse of (a) produces a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupled pulses omega_dec(ii) a Subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁With a locking frequency of ω_SLThe lock pulse of (1); and finally, carrying out data sampling. Preparation H^b，H^b’Lock pulse duration tau for singlet state₁80ms, lock frequency ω_SL17.2Hz, preparation H^c，H^c’Lock pulse duration tau for singlet state₁125ms, lock frequency ω_SL18.5 Hz. Decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: by the pulse sequence shown in FIG. 5, the spin coupling system (H) in the AGG molecule is controlled^b,H^b’And H^c,H^c’) Performing singlet state preparation and signal selection to respectively obtain two spin coupling systems H^b,H^b’(FIG. 9b) and H^c,H^c’(fig. 9c) while suppressing other signals.

And (4) analyzing and discussing results: from the analysis of FIG. 9, it can be seen that the AGG molecule has H^b,H^b’And H^c,H^c’Forming independent spin coupling system, and performing singlet state preparation and signal selection. Due to H^c,H^c’Has a high signal strength of H^c,H^c’The signal selection of the AGG molecule as a characteristic signal can obtain better signal sensitivity.

Example 2-AGG deuterium solution with mixture of leucine, glutamic acid and glycine¹Selection of AGG Nuclear magnetic signals in H Spectrum

Experimental samples: amino acid molecules, namely L-Alanine-glycine (AGG) and deuterium aqueous solution of a mixture of leucine, glutamic acid and glycine, wherein the mass fractions of the substances are as follows: 0.63% of AGG, 0.48% of leucine, glutamic acid: 0.61%, glycine: 0.53 percent.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. The method using the pulse sequence shown in fig. 5 is the same as that in embodiment 1. First a 90 DEG hard pulse with a phase in the y-direction is applied to the sample, and then a hard pulse with a phase in the x-direction is applied for a time tau₁125ms, lock frequency ofω_SL18.5Hz lock-in pulse with a center of transmission H^b，H^b’Sum of signals H^c，H^c’The center frequency between the signals, thereby producing a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms. (ii) a Subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁125ms, lock frequency ω_SL18.5Hz lock-in pulse; and finally, carrying out data sampling.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: by the pulse sequence shown in FIG. 5, we are dealing with H in the AGG molecule^c,H^c’The spin system was subjected to singlet generation and signal selection, and the spectrum is shown in FIG. 10. It can be seen that FIG. 10 is primarily H^c,H^c’All other signal strengths are greatly suppressed, leaving less than 0.1% of the HDO signal.

Example 3 mixture of AGG and insulin deuterium aqueous solution¹Selection of H-spectrum AGG nuclear magnetic signals

Experimental samples: amino acid molecules, namely a mixture deuterium aqueous solution of L-Alanine-glycine (AGG) and bovine insulin, wherein the mass fraction of the AGG is 0.05%, and the mass fraction of the bovine insulin is 1.04%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. The method using the pulse sequence shown in fig. 5 is the same as that in embodiment 1. First a 90 DEG hard pulse with a phase in the y-direction is applied to the sample, and then a hard pulse with a phase in the x-direction is applied for a time tau₁125ms, lock frequency ω_SL18.5Hz lock-in pulse with a center of transmission H^b，H^b’Sum of signals H^c，H^c’The center frequency between the signals, thereby producing a singlet state of the AGG molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec85Hz, decoupling time tau_m50 ms; subsequently applying an emission center of H^b，H^b’Sum of signals H^c，H^c’Centre frequency between signals, phase in x direction, time tau₁125ms, lock frequency ω_SL18.5Hz lock-in pulse; and finally, carrying out data sampling.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: by the pulse sequence shown in FIG. 5, we are dealing with H in the AGG molecule^c,H^c’The spin system was singlet-prepared and signal-selected, and the spectrum is shown in FIG. 11. It can be seen that FIG. 11 is primarily H^c,H^c’The suppression of the bovine insulin signal and the HDO signal is realized.

Example 4 Dopamine (DA) deuterium aqueous solution¹Selection of H-spectrum DA nuclear magnetic signals

Experimental samples: d of dopamine, Dopamine (DA)₂And O solution, wherein the mass fraction of DA is 1.5%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in fig. 8. In the experimental process, the radio frequency center needs to be moved to the benzene ring H^aAnd H^bThe center frequency between the signals. The sample is first subjected to a 90 hard pulse in the x-direction and then to tau₁-π_x-τ₁In which τ is₁30.9ms, the purpose of which is to remove the chemical shift evolution, followed by application

Can obtain a singlet state of the dopamine molecule, wherein tau₂6.8 ms; because a spinning system which is the same as three hydrogen on a benzene ring in the DA molecule does not exist in the mixed system, only the singlet state of the DA molecule is prepared; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec550Hz, decoupling time tau_m50 ms; is then applied

And τ₁-π_x-τ₁For detecting a singlet signal; and finally, signal acquisition is carried out. Wherein the power of the decoupled pulses needs to be optimized for optimal filtering.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: preparation of spin-coupled System H Using the pulse sequence shown in FIG. 8^a,H^b,H^dIs in a single state, realizes the H-pair DA molecules^aAnd H^bThe selection of the signal simultaneously realizes the suppression of other signals.

And (4) analyzing and discussing results: by the pulse sequence shown in FIG. 8, we are dealing with H in DA molecules^a,H^b,H^dThe spin system was subjected to singlet generation and signal selection, and the spectrum is shown in FIG. 12. It can be seen that in FIG. 12, the DA molecules H are predominant^aAnd H^bAll other signal intensities are greatly suppressed, leaving less than 0.05% of the HDO signal.

Example 5 very Low concentration Dopamine (DA) deuterium aqueous solution¹Selection of H-spectrum DA nuclear magnetic signals

Experimental samples: d of dopamine, Dopamine (DA)₂And O solution, wherein the mass fraction of DA is 0.0006%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. The method using the pulse sequence shown in fig. 5 is the same as that in embodiment 1. First a 90 DEG hard pulse with a phase in the y-direction is applied to the sample, and then a hard pulse with a phase in the x-direction is applied for a time tau₁180ms, lock frequency ω_SL8.1Hz lock pulse, which is emitted with H on the benzene ring as the center^aAnd H^bCenter frequency between signals; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec97Hz, decoupling time tau_m50 ms; followed by application of H on the benzene ring as the emission center^aAnd H^bLocking pulses of central frequency between signals, phase in x direction, time tau₁180ms, lock frequency ω_SLLock pulse at 8.1 Hz; and finally, carrying out data sampling. This experiment requires increasing the number of accumulations of signal acquisition. The number of accumulations in the experiment of FIG. 13b was 4000.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: preparation of spin-coupled System H Using the pulse sequence shown in FIG. 8^a,H^b,H^dNuclear spin singlet of (2) to DA molecule H^dThe radical signal enables selection while suppressing other signals.

And (4) analyzing and discussing results: by the pulse sequence shown in FIG. 8, we are dealing with H in DA molecules^a,H^b,H^dThe spin system was singlet-prepared and signal-selected, and the spectrum is shown in FIG. 13. It can be seen that in FIG. 13b, the DA molecules H are predominant^dAll other signal strengths are greatly suppressed.

Example 6-taurine deuterium aqueous solution¹Selection of H-spectrum taurine nuclear magnetic signals

Experimental samples: d of taurine, taurine (tau)₂O solution of Tau ofThe mass fraction is 2.1%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in fig. 8. During the experiment, the radio frequency center needs to be moved to the center frequency between the signals of hydrogen No. 1 and hydrogen No. 2 on methylene. The sample is first pulsed 90 DEG in phase in the x-direction and then tau₁-π_x-τ₁In which τ is₁10ms, apply

Can obtain the singlet state of the taurine molecule, wherein tau₂6.8 ms; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec500Hz, decoupling time tau_m50 ms; subsequent application of

And τ₁-π_x-τ₁For detecting a singlet signal.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: preparation of spin-coupled System H Using the pulse sequence shown in FIG. 8¹,H²The nuclear spin singlet state of (A) realizes the interaction with taurine molecule H¹And H²The selection of the signal, while the suppression of the other signals is achieved (see fig. 13).

And (4) analyzing and discussing results: by using the pulse sequence shown in fig. 8, a singlet state of a four-spin system is formed by preparing hydrogen on two methylene groups of taurine, so that the selection of a taurine molecular signal is realized, and the suppression of other signals is realized.

Example 7 creatine deuterium aqueous solution¹Selection of H-spectrum creatine nuclear magnetic signal

Experimental samples: creatine molecule, creatine D₂And O solution, wherein the mass fraction of creatine molecules is 1.2%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. The method using the pulse sequence shown in fig. 5 is the same as that in embodiment 1. First a 90 DEG hard pulse with a phase in the y-direction is applied to the sample, and then a hard pulse with a phase in the x-direction is applied for a time tau₁220ms, lock frequency omega_SL18Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing a singlet state of the creatine molecule; then applying a gradient field g in z direction₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec70Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁220ms, lock frequency omega_SL18Hz lock-in pulse; and finally, carrying out data sampling.

Single pulse methods and experiments are well known in the art.

And (3) testing results: by preparing the spin-coupled system H using the pulse sequence shown in FIG. 5^b,H^b’The nuclear spin singlet state realizes the selection of creatine molecule signals and simultaneously realizes the suppression of other signals.

And (4) analyzing and discussing results: the creatine spin coupling system H is prepared by using the pulse sequence shown in figure 5^b,H^b’The single state of (A) realizes the selection of creatine molecule signals and simultaneously realizes the suppression of other signals.

Example 8-Acetylaspartic acid (NAA) deuterium aqueous solution¹Selection of H-spectrum NAA nuclear magnetic signals

Experimental samples: d of N-acetylaspartic acid molecule (NAA)₂O solution, of NAAThe amount fraction was 1.1%.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. The method using the pulse sequence shown in fig. 5 is the same as that in embodiment 1. First a 90 DEG hard pulse with a phase in the y-direction is applied to the sample, and then a hard pulse with a phase in the x-direction is applied for a time tau₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the NAA molecule; then applying a gradient field g in z direction₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec70Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; and finally, carrying out data sampling.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: by preparing the spin-coupled system H using the pulse sequence shown in FIG. 5^b,H^b’The nuclear spin singlet state realizes the selection of NAA signals and simultaneously realizes the suppression of other signals. See fig. 16.

Example 9 Acetylaspartic acid (NAA) in combination with mouse brain tissue¹Selection of H-spectrum NAA nuclear magnetic signals

Experimental samples: a deuterium aqueous solution of NAA (NAA mass fraction 1.1%) was mixed with mouse brain tissue.

The determination method comprises the following steps: a single pulse sequence and the pulse sequence shown in figure 5. Firstly, a 90 DEG hard pulse with the phase in the y direction is applied to a sampleThe reapplied phase is in the x direction for a time τ₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the NAA molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 10Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; and finally, carrying out data sampling.

Single pulse methods and experiments are well known in the art.

And (3) measuring results: by preparing the spin-coupled system H using the pulse sequence shown in FIG. 5^b,H^b’The nuclear spin singlet state realizes the selection of NAA signals and simultaneously realizes the suppression of other signals.

Example 10 magnetic resonance molecular imaging of NAA, AGG and DA based on singlet Signal Filtering

Experimental samples: a4 mm inner diameter glass NMR sample tube with a mixture of 60% water and 40% deuterium water contained in it, 4 small glass tubes with an outer diameter of 0.9mm were placed in the glass NMR sample (see FIG. 18 a). In the small glass tube, a NAA deuterium aqueous solution with the mass fraction of 24.2%, an AGG deuterium aqueous solution with the mass fraction of 11.2%, a mixed water of 40% water and 60% deuterium water and a DA deuterium aqueous solution with the mass fraction of 10.5% are respectively arranged.

The determination method comprises the following steps: a spin echo imaging sequence and the pulse sequence shown in figure 6. In the experiment of molecular imaging using the pulse sequence shown in fig. 6, spin singlet states of NAA, AGG, and DA were prepared, respectively, to select these molecular signals, and then molecular imaging of each of these molecular signals was performed. The specific experimental steps are as follows:

NAA molecules by applying a 90 DEG hard pulse with a phase in the y direction to a sample, and then applying a hard pulse with a phase in the x direction for a time tau₁105ms, lock frequency ω_SL17.22Hz lock pulse with a center of transmission H^b，H^b’The central frequency between the signals, thereby producing the singlet state of the NAA molecule; then a gradient field g in the z direction is applied₁And g₂And decoupling the pulses. Gradient field g₁And g₂The intensity and the action time of (2) are optimized, and the gradient field intensity is 5Gauss/cm and the action time is 1 ms. Decoupled pulse power omega_dec90Hz, decoupling time tau_m50 ms; then the applied phase is in the x-direction for a time τ₁105ms, lock frequency ω_SLLock pulse at 17.22 Hz; and finally, carrying out frequency encoding in the y direction and phase encoding in the x direction to obtain magnetic resonance molecular imaging of NAA molecules in the sample.

AGG the experimental procedure is the same as the NAA molecular imaging procedure described above. The radio frequency center needs to be defined as AGG molecule H in the experimental process^c,H^c’The lock pulse time is changed to tau₁125ms, lock frequency ω_SL＝18.2Hz。

DA the experimental procedure was the same as the NAA molecular imaging procedure described above. The radio frequency center needs to be determined as DA molecule H in the experimental process^a,H^bThe lock pulse time is changed to tau₁180ms, lock frequency ω_SL＝8.1Hz。

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

And (3) measuring results: selective molecular imaging of NAA, AGG and DA is achieved.

And (4) analyzing and discussing results: the spin echo imaging results are shown in figure 18 b. Wherein the grey large disc is formed from a mixed water of 60% water and 40% deuterium water in a 4mm inner diameter glass nmr sample tube, representing the cross-section of the 4mm inner diameter glass nmr sample tube. From top to bottom, there are 4 small disks with different brightness, and a circle of black ring is around each small disk. The small circles represent the cross-sections of the different vials, and the brightness is related to the concentration of the solution in the vial. The black ring is from the wall of the small glass tube. The results of imaging the NAA molecules are shown in figure 18 c. Since only the top cuvette in the sample has NAA molecules, only the cross-sectional signal of the NAA-containing cuvette appears in the image of FIG. 18 c. Similarly, only the signals of the cross-sections of the glass vials containing AGG and DA are shown in the molecular images of AGG and DA, respectively. It can be seen that the method of the present invention can well perform molecular selective imaging 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 an organism and realizing molecular imaging of the molecule.

Example 11 magnetic resonance molecules MRS based on NAA, AGG and DA Filtering of the singlet signals

The determination method comprises the following steps: a spin echo imaging sequence and the pulse sequence shown in figure 7. In the pulse sequence shown in fig. 7, first, the sample is subjected to signal slice selection. Layer selection methods and experiments are well known in the art. In this example, the selection layer is excited by a hard pulse and then sample specific spatial signal selection is carried out by using a combination of sinc wave pulse and gradient field. Then, the selection of molecular signals is realized through the nuclear spin singlet preparation of specific molecules, and finally, the magnetic resonance spectrum observation of the molecular signals is carried out. The experimental parameters for the selection of specific molecular signals were as follows:

NAA with emission center H^b，H^b’Center frequency between signals, lock frequency omega of lock pulse_SL17.22Hz, duration of action τ₁105ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

AGG: the emission center is H^c，H^c’Center frequency between signals, lock frequency omega of lock pulse_SL18.2Hz, duration of action τ₁125ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

DA having an emission center of H^a,H^bCenter frequency between signals, lock frequency omega of lock pulse_SL8.1Hz, time of action τ₁180ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

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

And (3) measuring results: realizing the molecular selective magnetic resonance spectrum of NAA, AGG and DA.

And (4) analyzing and discussing results: the sample spin echo imaging results are shown in figure 18 a. Wherein the grey large disc is formed from a mixed water of 60% water and 40% deuterium water in a 4mm inner diameter glass nmr sample tube, representing the cross-section of the 4mm inner diameter glass nmr sample tube. From top to bottom, there are 4 small disks with different brightness, and a circle of black ring is around each small disk. The small circles represent the cross-sections of the different vials, and the brightness is related to the concentration of the solution in the vial. The black ring is from the wall of the small glass tube. The white boxes in fig. 18a indicate the signal selection areas in the selection layer. Fig. 18b is a conventional MRS spectrum of the area indicated by the white box of fig. 18 a. The signals for DA, AGG, NAA and water (HDO) are clearly visible in the spectrum. FIG. 18c molecular MRS spectra after nuclear spin singlet preparation and signal selection on AGG molecules. It can be seen that NAA and DA in the spectra were substantially absent, while the signal of water (HDO) was also greatly suppressed. Similarly, fig. 18d and 18e show molecular MRS spectra of NAA and DA. From the molecular MRS spectrogram, the method can well 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 an organism and realizing its molecular MRS.

The protection of the present invention is not limited to the above embodiments. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept, and the scope of the appended claims is intended to be protected.

Claims

1. A method for magnetic resonance spectroscopy of a target in a designated space using nuclear spin singlet selectivity, the method comprising:

step i: selecting magnetic resonance signals in a designated space by a magnetic resonance imaging gradient layer selection technology;

step ii: and (e) selecting a signal of the target object in the magnetic resonance signals obtained in the step (i) by utilizing the nuclear spin singlet selectivity, and the method comprises the following substeps:

wherein the target is various substances with a multi-spin coupling system;

step iii: converting the signals of the target object obtained in the step ii into signals required by magnetic resonance spectroscopy through pulse or pulse combination, and finally obtaining the magnetic resonance spectroscopy of the signals of the target object in the designated space.

2. The method of claim 1, wherein when the target is aceto-aspartic acid, the emission center is H^b，H^b’Center frequency between signals, lock frequency omega of lock pulse_SL17.22Hz, duration of action τ₁105ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

3. The method of claim 1, wherein when the target is an amino acid molecule, the emission center is H^c，H^c’Center frequency between signals, lock frequency omega of lock pulse_SL18.2Hz, duration of action τ₁125ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

4. The method of claim 1, wherein when the target is dopamine, the emission center is H^a,H^bCenter frequency between signals, lock frequency omega of lock pulse_SL8.1Hz, time of action τ₁180ms, gradient field g₁And g₂The intensity and the action time of (2) are optimized, the gradient field intensity is 5Gauss/cm, the action time is 1ms, and the decoupling pulse power omega is_dec90Hz, decoupling time tau_m＝50ms。

5. The method of claim 1, wherein the target comprises dopamine, taurine, aceto-aspartic acid, AGG, hypotaurine, creatine, choline chloride, glucose, glutathione.

6. The method according to claim 1, wherein in step ii2, the nuclear spin coupling system of the object is prepared into the nuclear spin singlet state of the object by a pulse sequence, and the pulse sequence is designed to include the following steps:

ii21, analyzing the target molecules, and distinguishing the spin coupling structure existing in the structure into a strong spin coupling structure and/or a weak spin coupling structure;

ii22, preparing the single state of each rotary coupling structure in the target molecule, and comparing the preparation efficiency of each single state;

and ii23, selecting a spin coupling structure with the highest singlet preparation efficiency and a pulse sequence for preparing the nuclear spin singlet of the target object.

7. The method of claim 1, wherein in step ii3, the decoupling is achieved by including spin lock pulses, or a combination of pulses with a specific timing; the choice of decoupling time increases with the relaxation time of the nuclear spin singlet; the decoupling time is longer than the action time of the pulse gradient field.

8. The method as claimed in claim 1, wherein in step ii3, the non-target object nuclear spin singlet magnetic resonance signal in the signal from step ii2 is dispersed by the pulsed gradient field, while the target object nuclear spin singlet signal is maintained, so as to realize selective observation of the target object signal; the target molecule signal selection effect is realized by adjusting the strength, the application times and the position mode of the pulse gradient field.

9. The method according to claim 1, wherein in step ii4, different pulses or combinations of pulses are selected based on the multi-spin coupling properties of different targets.

10. The method of claim 1, wherein in step ii4, the singlet signal from step ii3 is converted into a signal required for subsequent nuclear magnetic spectroscopy and/or imaging by a pulse or a combination of pulses.