Non-diagnostic method for selectively observing magnetic resonance signals of lactic acid molecules in living body and application

Abstract

The invention discloses a non-diagnostic method for selectively observing a magnetic resonance signal of a lactic acid molecule 1H in a living body, which comprises the following steps of: controlling a four-spin coupling system formed by 1H on methyl and methine of a lactic acid molecule by designing a pulse sequence, and preparing a Zeeman sequence spin state of the four-spin coupling system; the method comprises the following steps of: controlling a four-spin coupling system formed by 1H on methyl and methine of the lactic acid molecules by utilizing a preparation pulse, and preparing a Zeeman sequence spin state of the four-spin coupling system; eliminating or suppressing a nuclear spin coherent signal in an observation system through a pulse gradient field, and keeping the prepared Zeeman sequence nuclear spin state at the same time; converting the prepared Zeeman sequence nuclear spin state into an observable magnetic resonance signal by using a conversion pulse; magnetic resonance signals are collected, and selective observation of the magnetic resonance signals of the methyl 1H in the lactic acid tetraspin coupling system is achieved. The invention also discloses application of the method in selective screening and detection of lactic acid signals in a living body.

Description

Technical Field

[0001] The present invention belongs to the field of magnetic resonance technology, and specifically relates to a method and application for selectively detecting magnetic resonance signals of lactic acid molecules in a living body for non-diagnostic purposes by preparing Zeeman-ordered spin states of a multi-spin system. Technical Background

[0002] Lactic acid is an important metabolic molecule in the human body. In areas with abnormal tissue metabolism, lactic acid usually accumulates, especially in tumor areas, which are often accompanied by a significant increase in the concentration of lactic acid molecules. Therefore, selective observation of lactic acid molecule signals in vivo will be of great significance for early diagnosis and prevention of diseases. Conventional magnetic resonance spectroscopy (MRS) methods for detecting lactic acid molecules mainly include long TE filtering, zero quantum and double quantum filtering. Among them, the long TE method is affected by factors such as lactic acid molecule relaxation, and only has a good effect when the lactic acid molecule content is high; zero quantum filtering can well suppress the background signal around the lactic acid molecule, but can only retain 50% of the theoretical efficiency for the lactic acid molecule signal, and the experimental efficiency will be further reduced; multi-quantum filtering technology also has similar problems, and it is difficult to efficiently and selectively observe lactic acid molecule signals in living tissues. Summary of the invention

[0003] In order to solve the problem that the existing technology cannot efficiently and selectively observe the lactic acid molecule signal in the living body, the present invention proposes a method for selectively detecting the magnetic resonance signal of lactic acid molecules in the living body by preparing the Zeeman order spin state of the multi-spin system. Specifically, it is a method for selectively detecting the magnetic resonance signal of lactic acid molecules in the living body by precisely manipulating the methyl and methine of lactic acid molecules. 1 H, and efficiently prepare the Zeeman-ordered spin state of the spin system, thus realizing a pulse sequence method for selectively detecting the magnetic resonance signal of lactic acid molecules in living bodies. 1 The Zeeman-order spin state of the four-spin coupled system composed of H is not affected by the pulse gradient field. By designing efficient Zeeman-order spin state preparation pulses and conversion pulses, selective observation of the methyl magnetic resonance signal of lactic acid molecules in living bodies can be achieved.

[0004] Specifically, the method of the present invention includes the following core steps:

[0005] Step i: Using the preparation pulse to manipulate the methyl and methine groups of the lactic acid molecule 1 A four-spin coupling system composed of H, preparing a Zeeman-order spin state of the four-spin coupling system;

[0006] Step ii: utilizing the characteristic that the Zeeman-order nuclear spin state is not affected by the pulse gradient field, eliminating or suppressing the nuclear spin coherence signal in the observation system through the pulse gradient field, while maintaining the Zeeman-order nuclear spin state prepared in step i;

[0007] Step iii: using a conversion pulse to convert the Zeeman-order nuclear spin state prepared in step i into an observable magnetic resonance signal;

[0008] Step iv: Collect magnetic resonance signals to achieve the methyl 1 Selective observation of H magnetic resonance signals.

[0009] In step i, the pulse preparation includes one or more pulse units with specific amplitude and phase, and the pulse preparation can convert the methyl and methine groups of the lactic acid molecules into 1 The spin state of the four-spin coupling system composed of H changes from the thermal equilibrium state R 1z +R 2z +R 3z +S z Transformed to Zeeman order spin state R 1z S z +R 2z S z +R 3z S z +S z The preparation pulse in the present invention can also be called the first optimization control pulse or optimization control pulse I. 1 H spin labeled with R m , m∈{1,2,3}, 1 methine 1 H spins are labeled S, see Figure 1 .

[0010] In a specific embodiment, the number of the pulse units is 1000, the action time of the preparation pulse is 70 ms, the radio frequency center is 1.33 ppm, and the maximum amplitude of the pulse unit is 200 Hz.

[0011] In step ii, the pulse gradient field includes a first gradient pulse and a second gradient pulse, and the pulse gradient field scatters the lateral signal of the non-target state. Specifically, the first gradient pulse is used to scatter the lateral signal except R 1z S z +R 2z S z +R 3z S z +S z The second gradient pulse is used to dephase the transverse signals except R. 1z +R2z +R 3z +S z The two gradient pulses disperse the phases of the non-target signals while maintaining the Zeeman order spin state of the prepared multi-spin coupling system. By adjusting the intensity, application time, number of times and position of the pulse gradient field, the elimination or suppression effect of the nuclear spin coherent signal in the observation system is optimized. Within the range allowed by the instrument gradient intensity, the intensity and width of the two gradient pulses need to be set to disperse the signal without causing signal re-convergence; in the present invention, the intensity range of the first gradient pulse and the second gradient pulse is 5Gs / cm-10Gs / cm, and the pulse width range is 1ms-2ms; preferably, the intensity of the first gradient pulse g1 and the second gradient pulse g2 are 5Gs / cm and 6Gs / cm, respectively, and the pulse width is 1ms.

[0012] In step iii, the conversion pulse includes one or more pulse units with specific amplitude and phase. By applying the reasonably designed conversion pulse, the Zeeman order spin state R of the multi-spin coupling system subjected to the pulse gradient field in step ii is converted to 1z S z +R 2z S z +R 3z S z +S z into one or more observable nuclear spin states, such as R 1z +R 2z +R 3z +S x , to achieve the methylation of lactic acid molecules 1 Selective observation of the H signal, the conversion pulse in the present invention can also be called the second optimized control pulse or the optimized control pulse II.

[0013] In a specific embodiment, the number of the pulse units is 1000, and the action time of the preparation pulse is 70 ms;

[0014] In a specific embodiment, the radio frequency center is 1.33 ppm and the maximum amplitude of the pulse unit is 200 Hz.

[0015] In step iv, magnetic resonance signal acquisition can be performed by imaging and / or spectroscopy. In in vivo spectroscopy applications, point decomposition spectroscopy can be combined to achieve the detection of methyl groups of lactic acid molecules in a specific space. 1 Selective observation of H magnetic resonance signals.

[0016] The pulse sequence of the present invention includes a pulse sequence for methyl and methine groups in a spectroscopy instrument. 1Preparation and detection of multi-spin quantum states of H and / or in imaging spectrometers for methyl and methine 1 The multi-spin quantum state preparation and detection sequence of H is modularly designed. The pulse sequence includes a lactic acid molecule magnetic resonance signal selection module and a magnetic resonance signal acquisition module; wherein the lactic acid molecule magnetic resonance signal selection module includes: 1 The multi-spin coupling system Zeeman order spin state preparation pulse composed of H, one or more gradient pulses and a conversion pulse for converting the Zeeman order spin state of the multi-spin coupling system into an observable magnetic resonance signal. The magnetic resonance signal acquisition module includes a radio frequency gradient pulse and a layer selection pulse, and uses point decomposition spectroscopy to realize the detection of lactic acid molecule methyl groups in a specific space. 1 Selective observation of H magnetic resonance signals; and / or,

[0017] In in vivo spectroscopy applications, water pulses can be used to suppress water signals.

[0018] The present invention also provides the application of the above method in controlling the nuclear spin quantum state evolution of specific groups of lactic acid molecules, realizing specific screening of lactic acid signals, improving the intensity of molecular targeted nuclear magnetic resonance signals, and in the detection of lactic acid in living organisms for non-diagnostic purposes.

[0019] In addition, the present invention also includes the following basic steps: (1) using conventional magnetic resonance imaging technology to locate the area to be tested in the living organism. (2) if necessary, using conventional nuclear magnetic resonance spectroscopy technology, magnetic resonance spectroscopy (MRS) technology to collect the spectrum of the area to be tested. (3) using conventional MRS technology for measuring lactic acid signals to collect the spectrum of the area to be tested. These are known knowledge in the field.

[0020] Specifically, the schematic diagram of the pulse sequence function design for selective observation of lactic acid molecules of the present invention is as follows: Figure 2 It is divided into four parts: preparing Zeeman order spin state; eliminating or suppressing the nuclear spin coherence signal in the system while maintaining the Zeeman order spin state prepared by the previous pulse; converting the Zeeman order spin state into an observable magnetic resonance signal; and collecting magnetic resonance signals by imaging and / or spectroscopy. The pulse sequence diagram for selectively observing lactic acid molecules is shown in Figure 3 As shown. The pulse sequence is mainly composed of a "signal selection" module and a "signal acquisition" module. The "signal selection" module is mainly composed of an "optimized control pulse I", a first gradient pulse "g1" and a second gradient pulse "g2", and an "optimized control pulse II":

[0021] "Optimized Control Pulse I": used to convert the methyl groups of lactic acid molecules into 1 H spin (labeled as R m, m∈{1,2,3}) and one methine 1 The four-spin coupled system composed of H spins (labeled as S) is composed of the thermal equilibrium state R 1z +R 2z +R 3z +S z Transform to state R 1z S z +R 2z S z +R 3z S z +S z , thereby achieving the methyl and methine 1 The Zeeman order spin state preparation of H spin coupling system. The present invention designs "optimized control pulse I" by using optimization control theory and numerical calculation method. In principle, the theoretical efficiency of "optimized control pulse I" suitable for conventional magnetic resonance imagers (1.5T and above) can reach more than 99%. Figure 4 A method for preparing the methyl and methine groups of lactic acid molecules is presented. 1 Example of optimized control pulse I of the Zeeman-ordered spin state of the H spin coupling system, where Figure 4 a is a graph showing the amplitude variation of a pulse unit in the optimized control pulse I, Figure 4 b is a phase change diagram of a pulse unit in the optimized control pulse I. The core and innovative function of the "optimized control pulse I" is to convert the methyl and methine of the lactic acid molecule into 1 The four-spin coupling system composed of H is composed of a thermal equilibrium state R 1z +R 2z +R 3z +S z Transformed to Zeeman order spin state R 1z S z +R 2z S z +R 3z S z +S z .

[0022] "Gradient pulse": used to further eliminate or suppress the nuclear spin coherence signal in the observation system, while maintaining the Zeeman order spin state of the prepared multi-spin coupling system. By adjusting the intensity, application time, number and position of the pulse gradient field, the elimination or suppression effect of the nuclear spin coherence signal in the observation system can be optimized.

[0023] "Optimized Control Pulse II" is used to convert the methyl and methine groups of lactic acid molecules into 1 Zeeman-ordered spin states of the H spin coupling system, R 1z S z +R 2z Sz +R 3z S z +S z , converted into one or more observable magnetic resonance signals. The present invention uses the optimization control theory and numerical calculation method to design the "optimized control pulse II". In principle, the theoretical efficiency of the "optimized control pulse II" suitable for conventional magnetic resonance imaging devices (1.5T and above) can reach more than 99%. Through the "optimized control pulse II", the methyl and methylene groups of the lactic acid molecules are converted into 1 Zeeman-ordered spin states of the H spin coupling system, R 1z S z +R 2z S z +R 3z S z +S z , into an observable nuclear spin state, such as R 1z +R 2z +R 3z +S x , used for magnetic resonance signal observation. Figure 4 Demonstrates a method for combining the methyl and methine groups of lactic acid molecules 1 Zeeman order spin state of the four-spin coupling system composed of H, R 1z S z +R 2z S z +R 3z S z +S z , converted to the nuclear spin state, R 1z +R 2z +R 3z +S x , an example of optimized control pulse, where Figure 4 c is the amplitude variation diagram of a pulse unit in the optimized control pulse II, Figure 4 d is the phase change diagram of a pulse unit in the optimized control pulse II. The core and innovative function of the "optimized control pulse II" is to convert the methyl and methine of lactic acid molecules into 1 The four-spin coupling system composed of the Zeeman order spin state R 1z S z +R 2z S z +R 3z S z +S z Transformed to thermal equilibrium state R 1z +R 2z +R 3z +S x .

[0024] Figure 3The "signal acquisition" module in the pulse sequence is mainly composed of radio frequency gradient pulses and slice selection pulses. This module can realize the selective observation of lactic acid molecules in a specific spatial position. In order to realize the observation of the magnetic resonance signal of lactic acid molecules in a specific spatial position, the position of the living organism in the magnetic field can be located using conventional magnetic resonance imaging methods. This part of knowledge is well known in the field and will not be further elaborated in the present invention.

[0025] Figure 3 A "saturation pulse" is applied at the beginning of the pulse sequence. The main purpose of this pulse module is to suppress the signal of water molecules in living tissues or organs. The pulse width, power and position of the "saturation pulse" can be adjusted according to the detection needs of the system. In application scenarios where the water signal intensity is not high, the "saturation pulse" can be selected not to be used according to actual needs. The "saturation pulse" used to suppress the water signal is common knowledge in the field and will not be further elaborated in the present invention.

[0026] The method of the present invention can be applied to the selective observation of magnetic resonance signals of lactic acid molecules in human cerebrospinal fluid in vitro, and specifically comprises the following steps:

[0027] 1. Apply Figure 3 The pulse sequence shown in the figure. The "saturation pulse" is composed of 4 Gaussian pulses, each with an amplitude of 35Hz and a duration of 250ms. The "optimized control pulse I" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are as follows Figure 4 a and 4b. The RF center of the "optimized control pulse I" is 1.33ppm, and the maximum amplitude of the pulse unit is 200Hz. The "optimized control pulse II" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are shown in Figure 4 c and 4d. During the experiment, the pulse amplitude and RF center can be fine-tuned to optimize the signal.

[0028] 2. Ex vivo CSF ​​Samples 1 H NMR Figure 5 As shown, the experimental parameters are as follows: the number of sampling is 64 times, the receiver gain is 128, and the acquisition time is 192s. Figure 5 a is the spectrum obtained by detecting lactic acid molecules in isolated cerebrospinal fluid using the CPMG pulse sequence, which is used to selectively obtain the hydrogen spectrum of lactic acid in isolated cerebrospinal fluid with the optimized pulse ( Figure 5 b) for comparison. 1 HNMR Figure 5c. Among them, the signals at 0.8-1.5ppm are fat and macromolecule signals. The magnetic resonance signal of the lactic acid molecule methyl group is located at 1.33ppm, showing a double peak. The signal of the lactic acid molecule overlaps with the fat signal. Figure 5 b is through Figure 3 Targeted observation of lactate obtained by pulse sequence 1 H NMR spectrum. From the spectrum, we can see that except for the lactic acid signal, other molecular signals have been suppressed. By comparison, we can see that Figure 5 The magnetic resonance signal of the lactic acid methyl group in b is slightly lower than that of the conventional hydrogen spectrum ( Figure 5 c) The magnetic resonance signal of the lactic acid methyl group, but much higher than Figure 5 The magnetic resonance signal of the methyl group of the lactic acid molecule in a indicates that the pulse method developed in the present invention has a better selection efficiency for the magnetic resonance signal of the methyl group of lactic acid.

[0029] Specifically, in the actual test, Figure 5 The signal intensity of lactate molecules in c is defined as 1, Figure 5 The ratio of the lactic acid signal intensity in a and 5b to the lactic acid molecule signal intensity in 5c is defined as the filtering efficiency. The experimental filtering efficiency of the CPMG pulse sequence is only 28%, while the experimental filtering efficiency of the method described in the present invention is 74%, which is nearly three times that of the existing CPMG pulse sequence.

[0030] The method of the present invention can also be applied to the detection of lactic acid molecules in the living brain, and specifically comprises the following steps:

[0031] 1. Use conventional T1-weighted imaging pulse sequences to locate the spatial position of the subject's head in the magnetic field. The located magnetic resonance imaging image and the area to be measured are as follows: Figure 6 As shown in a, the white box area in the figure is the area to be tested.

[0032] 2. Apply Figure 3 The pulse sequence shown in the figure. The "saturation pulse" is composed of 4 Gaussian pulses, each with an amplitude of 35Hz and a duration of 250ms. The "optimized control pulse I" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are as follows Figure 4 a and 4b, used to remove R 1z S z +R 2z S z +R 3z S z +S zThe lateral signals other than the 100 μs are dispersed. The RF center of the "optimized control pulse I" is 1.33 ppm, and the maximum amplitude of the pulse unit is 200 Hz. The "optimized control pulse II" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method. The action time is 70 ms, and it consists of 1000 70 μs pulse units. The amplitude and phase of each pulse unit are as follows: Figure 4 c and 4d, used to remove R 1z +R 2z +R 3z +S z The lateral signals other than the ion source are dephased. The duration of the 90-degree "sinc" pulse and the 180-degree "sinc" pulse are 1ms and 2ms respectively, and the amplitude is 250Hz. During the experiment, the power and RF center of the pulse can be fine-tuned to optimize the lactic acid molecule. 1 H signal.

[0033] The spatial position of the subject's brain in the magnetic field is Figure 6 As shown in a, the white box represents the area selected for the in vivo magnetic resonance spectroscopy experiment, which is near the cerebrospinal fluid. The experimental parameters are as follows: the voxel size is 20×30×20mm 3 , TE = 30ms, TR = 1.5s, the number of sampling points is 512, the sampling bandwidth is 1000Hz, and the number of sampling times is 64. The magnetic resonance spectrum obtained by the conventional MRS pulse sequence is as follows Figure 6 As shown in Figure b, the methyl signal of acetyl aspartate is located at 2.0ppm, the methylene signals of acetyl aspartate, glutamic acid and glutamine are located at 2.0-2.8ppm, the methyl signal of choline is located at 3.0ppm, the methyl signal of creatine is located at 3.2ppm. The methyl signal of lactic acid and the methylene signal of fat molecules are both located at 1.33ppm. Figure 6 The bottom curve of c is Figure 6 b is a local enlarged view, the lactic acid methyl signal and the fat molecule methine signal overlap with each other, and the lactic acid signal and the fat signal cannot be distinguished separately. Figure 6 c The middle curve is the magnetic resonance spectrum obtained using a long echo time MRS pulse sequence, in which TE was set to 144 ms. Figure 6 The top curve of c is Figure 3 Pulse sequence selective observation of lactate 1 The magnetic resonance spectrum obtained by using H signal. From the figure, we can see the double peak signal of lactic acid methyl group with chemical shift around 1.3ppm, which shows that this sequence method has good sensitivity and high selectivity for observing magnetic resonance signal of lactic acid molecule.

[0034] The beneficial effects of the present invention include: the conventional magnetic resonance spectroscopy method for observing magnetic resonance signals of lactic acid molecules in vivo is to lengthen the echo time in the pulse sequence to select the lactic acid molecule signal. Different from the conventional method, the pulse sequence method of the present invention is to efficiently manipulate the methyl and methine groups of lactic acid molecules by rationally designing pulses. 1 The invention uses a four-spin coupling system composed of H to prepare the Zeeman order spin state of the spin coupling system, and realizes the selective detection of the magnetic resonance signal of the lactic acid molecule. At the same time, the invention utilizes the Zeeman order spin state property of the spin coupling system to remove the background signal commonly found in ordinary living body spectra and solve the problem of spectral peak overlap, and can be used to detect the signal of extremely low concentration lactic acid molecules in living organs, so it has important application prospects in the fields of medicine, biology, chemistry, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a schematic diagram of the molecular structure of lactic acid. 1 H spin labeled with R m , m∈{1,2,3}, 1 methine 1 The H spin is labeled as S.

[0037] Figure 2 Schematic diagram of pulse sequence function design for selective observation of lactic acid molecules. The schematic diagram is divided into four parts: preparing Zeeman order spin states; eliminating or suppressing nuclear spin coherence signals in the system while maintaining the Zeeman order spin states prepared by the previous pulse; converting the Zeeman order spin states into observable magnetic resonance signals; and collecting magnetic resonance signals by imaging and / or spectroscopy.

[0038] Figure 3 The pulse sequence schematic diagram of the present invention for selectively observing lactic acid molecules. The pulse sequence is mainly composed of a "signal selection" module and a "signal acquisition" module in terms of function; wherein the "signal selection" module is mainly composed of an "optimized control pulse I", a first gradient pulse "g1" and a second gradient pulse "g2", and an "optimized control pulse II"; and the "signal acquisition" module is mainly composed of a radio frequency gradient pulse and a layer selection pulse. 1 H represents hydrogen channel, G x ,G y and G zThey represent the pulse gradient channels in the x, y, and z directions respectively. g1 and g2 are gradient pulses. x ,180 y ,180 y are the pulse and phase used for the layer selection pulse respectively.

[0039] Figure 4 a is a pulse sequence intensity variation diagram of one pulse unit of the "optimized control pulse I" used in the present invention, Figure 4 b is the phase change diagram of the pulse sequence of one of its pulse units; Figure 4 c is the pulse sequence intensity variation diagram of one of the pulse units in “Optimized Control Pulse II”. Figure 4 d is the pulse sequence phase change diagram of one of the pulse units in “Optimized Control Pulse II”.

[0040] Figure 5 The magnetic resonance spectra of the isolated cerebrospinal fluid sample of the embodiment of the present invention are as follows: (a) the proton spectrum obtained by detecting lactic acid molecules in the isolated cerebrospinal fluid sample using CPMG pulses; (b) the proton spectrum obtained by using Figure 3 (a) Proton spectrum obtained by targeted detection of lactate in an isolated cerebrospinal fluid sample using pulses; (c) Proton spectrum obtained by conventional single pulse detection of lactate molecules in a cerebrospinal fluid sample.

[0041] Figure 6 The magnetic resonance imaging and spectrum of the living brain of the embodiment of the present invention are as follows: (a) Magnetic resonance T1-weighted imaging of the living brain of the embodiment; (b) Conventional MRS spectrum of the voxel shown in Figure a; (c) MRS spectrum obtained by applying different magnetic resonance methods to the voxel shown in Figure a. Among them, the top spectrum is obtained by using Figure 3 The pulse sequence was applied to the lactate signal to obtain the hydrogen spectrum selectively. Figure 3 The middle spectrum is the magnetic resonance spectrum obtained after the pulse sequence; the middle spectrum is the magnetic resonance spectrum obtained using a single-pixel MRS pulse with a long echo time (TE=144ms); the bottom spectrum is the magnetic resonance spectrum obtained using a single-pixel MRS pulse with a normal echo time (TE=30ms) ( Figure 6 b Enlarged view of the part selected by the black dashed line). DETAILED DESCRIPTION

[0042] The present invention is further described in detail with reference to the following specific examples and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0043] In order to solve the shortcomings of the prior art, the present invention has developed a pulse sequence method for selectively detecting the magnetic resonance signal of lactic acid molecules in vivo for non-diagnostic purposes by preparing the Zeeman-ordered spin state of a multi-spin system. 1 H spin and single 1 The four-spin coupling system composed of H spins is transformed from the thermal equilibrium state to the Zeeman order spin state, thereby realizing the selective observation of the magnetic resonance signal of lactic acid molecules. The experimental results show that this method has the advantages of being fast, non-invasive and highly efficient, and the measurement results have good stability and sensitivity. It has important application prospects in the fields of biology and medicine, and is a new and original technology.

[0044] Example 1

[0045] Experimental sample: In vitro cerebrospinal fluid sample. Preparation method is as follows: 200 μl cerebrospinal fluid and 250 μl deuterated water are mixed and transferred to a 5 mm nuclear magnetic resonance tube.

[0046] Measurement instrument: Instrument: Bruker 500MHz Avance III liquid magnetic resonance spectrometer.

[0047] Determination method: Figure 3 Pulse sequence shown.

[0048] The specific experimental steps are as follows:

[0049] 1. Apply Figure 3 The pulse sequence shown in the figure. The "saturation pulse" is composed of 4 Gaussian pulses, each with an amplitude of 35Hz and a duration of 250ms. The "optimized control pulse I" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are as follows Figure 4 a and 4b. The RF center of the "optimized control pulse I" is 1.33ppm, and the maximum amplitude of the pulse unit is 200Hz. The "optimized control pulse II" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are shown in Figure 4 c and 4d. During the experiment, the pulse amplitude and RF center can be fine-tuned to optimize the signal.

[0050] 2. Ex vivo CSF ​​Samples 1 H NMR Figure 5 As shown, the experimental parameters are as follows: the number of sampling is 64 times, the receiver gain is 128, and the acquisition time is 192s. Figure 5a is the spectrum obtained by detecting lactic acid molecules in isolated cerebrospinal fluid using the CPMG pulse sequence, which is used to selectively obtain the hydrogen spectrum of lactic acid in isolated cerebrospinal fluid with the optimized pulse ( Figure 5 b) for comparison. 1 H NMR Figure 5 c. Among them, the signals at 0.8-1.5ppm are fat and macromolecule signals. The magnetic resonance signal of the lactic acid molecule methyl group is located at 1.33ppm, showing a double peak. The signal of the lactic acid molecule overlaps with the fat signal. Figure 5 b is through Figure 3 Targeted observation of lactate obtained by pulse sequence 1 H NMR spectrum. From the spectrum, we can see that except for the lactic acid signal, other molecular signals have been suppressed. By comparison, we can see that Figure 5 The magnetic resonance signal of the lactic acid methyl group in b is slightly lower than that of the conventional hydrogen spectrum ( Figure 5 c) The magnetic resonance signal of the lactic acid methyl group, but much higher than Figure 5 The magnetic resonance signal of the methyl group of the lactic acid molecule in a indicates that the pulse method developed in the present invention has a good selection efficiency for the magnetic resonance signal of the methyl group of lactic acid.

[0051] Example 2

[0052] Experimental subjects: 24-year-old normal male, height 175cm, weight 70kg

[0053] Measurement instrument: Instrument: Siemens 3T Prisma nuclear magnetic resonance instrument; Coil: Siemens 64-channel head coil.

[0054] Determination method: Figure 3 Pulse sequence shown.

[0055] The experimental steps are as follows:

[0056] 1. Use conventional T1-weighted imaging pulse sequences to locate the spatial position of the subject's head in the magnetic field. The located magnetic resonance imaging image and the area to be measured are as follows: Figure 6 As shown in a.

[0057] 2. Apply Figure 3 The pulse sequence shown in the figure. The "saturation pulse" is composed of 4 Gaussian pulses, each with an amplitude of 35Hz and a duration of 250ms. The "optimized control pulse I" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are as follows Figure 4a and 4b. The RF center of the "optimized control pulse I" is 1.33ppm, and the maximum amplitude of the pulse unit is 200Hz. The "optimized control pulse II" is obtained by the optimized pulse control technology of the numerical calculation GRAPE method, with an action time of 70ms and composed of 1000 70μs pulse units. The amplitude and phase of each pulse unit are shown in Figure 4 c and 4d. The duration of the 90-degree "sinc" pulse and the 180-degree "sinc" pulse are 1ms and 2ms respectively, and the amplitude is 250Hz. During the experiment, the power and RF center of the pulse can be fine-tuned to optimize the lactic acid molecule. 1 H signal.

[0058] 3. The spatial position of the subject's brain in the magnetic field Figure 6 As shown in a, the white box represents the area selected for the in vivo magnetic resonance spectroscopy experiment, which is near the cerebrospinal fluid. The experimental parameters are as follows: the voxel size is 20×30×20mm 3 , TE = 30ms, TR = 1.5s, the number of sampling points is 512, the sampling bandwidth is 1000Hz, and the number of sampling times is 64. The magnetic resonance spectrum obtained by the conventional MRS pulse sequence is as follows Figure 6 As shown in Figure b, the methyl signal of acetyl aspartate is located at 2.0ppm, the methylene signals of acetyl aspartate, glutamic acid and glutamine are located at 2.0-2.8ppm, the methyl signal of choline is located at 3.0ppm, the methyl signal of creatine is located at 3.2ppm. The methyl signal of lactic acid and the methylene signal of fat molecules are both located at 1.33ppm. Figure 6 The bottom curve of c is Figure 6 b is a local enlarged view, the lactic acid methyl signal and the fat molecule methine signal overlap with each other, and the lactic acid signal and the fat signal cannot be distinguished separately. Figure 6 c The middle curve is the magnetic resonance spectrum obtained using a long echo time MRS pulse sequence, in which TE was set to 144 ms. Figure 6 The top curve of c is Figure 3 Pulse sequence selective observation of lactate 1 The magnetic resonance spectrum obtained by using H signal. From the figure, we can see the double peak signal of lactic acid methyl group with chemical shift around 1.3ppm, which shows that this sequence method has good sensitivity and high selectivity for observing magnetic resonance signal of lactic acid molecule.

[0059] The traditional magnetic resonance spectroscopy method used to observe the magnetic resonance signal of lactic acid molecules in vivo is to lengthen the echo time in the pulse sequence to select the lactic acid molecule signal. Different from the traditional method, the pulse sequence method described in the present invention is to efficiently manipulate the methyl and methine groups of lactic acid molecules by rationally designing pulses. 1The invention uses a four-spin coupling system composed of H to prepare the Zeeman order spin state of the spin coupling system, and realizes the selective detection of the magnetic resonance signal of the lactic acid molecule. At the same time, the invention utilizes the Zeeman order spin state property of the spin coupling system to remove the background signal commonly found in ordinary living body spectra and solve the problem of spectral peak overlap. It is fast, non-invasive, and radiation-free, and can be used to detect the detection of extremely low concentration lactic acid molecule signals in living organs. It has good accuracy and sensitivity, and therefore has important application prospects in the fields of medicine, biology, chemistry, and especially in the early diagnosis of diseases.

[0060] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the present invention, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

Claims

1. A non-diagnostic method for selectively observing lactate molecules in vivo 1 H magnetic resonance signal method, characterized in that The method controls the methyl and methine groups of lactic acid molecules by designing a pulse sequence. 1 A four-spin coupling system composed of H is prepared, and the Zeeman order spin state of the four-spin coupling system is prepared to achieve selective detection of the methyl magnetic resonance signal of the lactic acid molecule; the method comprises the following core steps: Step i: Using the preparation pulse to manipulate the methyl and methine groups of the lactic acid molecule 1 A four-spin coupling system composed of H, preparing a Zeeman-order spin state of the four-spin coupling system; Step ii: eliminating or suppressing the nuclear spin coherence signal in the observation system by means of a pulse gradient field, while maintaining the Zeeman-ordered nuclear spin state prepared in step i; Step iii: using a conversion pulse to convert the Zeeman-order nuclear spin state prepared in step i into an observable magnetic resonance signal; Step iv: Collect magnetic resonance signals to realize the methyl 1 Selective observation of H magnetic resonance signals.

2. The method according to claim 1, characterized in that In step i, the pulse preparation includes one or more pulse units with specific amplitude and phase, and the pulse preparation converts the methyl and methine groups of the lactic acid molecules into 1 The spin state of the four-spin coupling system composed of H changes from the thermal equilibrium state R 1z +R 2z +R 3z +S z Transformed to Zeeman order spin state R 1z S z +R 2z S z +R 3z S z +S z ; Among them, the 3 methyl 1 H spin labeled with R m , m∈{1,2,3}, 1 methine 1 The H spin is labeled as S.

3. The method according to claim 1, characterized in that In step ii, the pulse gradient field includes a first gradient pulse and a second gradient pulse; the pulse gradient field dephases the transverse signal of the non-target state while maintaining the Zeeman order spin state of the prepared multi-spin coupling system, and optimizes the elimination or suppression effect of the nuclear spin coherent signal in the observation system by adjusting the intensity, application time, number and position of the pulse gradient field; and / or, The intensity range of the first gradient pulse and the second gradient pulse is 5Gs / cm-10Gs / cm, and the pulse width range is 1ms-2ms.

4. The method according to claim 1, characterized in that In step iii, the conversion pulse includes one or more pulse units with specific amplitude and phase, and the conversion pulse converts the Zeeman order spin state R of the multi-spin coupling system to the state R of the multi-spin coupling system under the action of the pulse gradient field in step ii. 1z S z +R 2z S z +R 3z S z +S z into one or more observable nuclear spin states, wherein the observable nuclear spin states include R 1z +R 2z +R 3z +S x .

5. The method according to claim 1, characterized in that In step iv, magnetic resonance signal acquisition is performed by imaging and / or spectroscopy; in in vivo spectroscopy applications, point decomposition spectroscopy is combined to achieve the methyl groups of lactic acid molecules in a specific space. 1 Selective observation of H magnetic resonance signals.

6. The method according to claim 2, characterized in that The number of pulse units for preparing the pulse is 1000, the action time of the pulse for preparing the pulse is 70 ms, the radio frequency center is 1.33 ppm, and the maximum amplitude of the pulse unit is 200 Hz.

7. The method according to claim 4, characterized in that The number of pulse units of the conversion pulse is 1000, and the action time of the preparation pulse is 70 ms.

8. The method according to claim 1, characterized in that The pulse sequence includes the following steps: 1 Preparation and detection of multi-spin quantum states of H and / or in imaging spectrometers for methyl and methine 1 Preparation and detection sequence of multi-spin quantum states of H.

9. The method according to claim 8, characterized in that The pulse sequence comprises a lactic acid molecule magnetic resonance signal selection module and a magnetic resonance signal acquisition module; wherein the lactic acid molecule magnetic resonance signal selection module comprises: 1 The invention relates to a multi-spin coupling system Zeeman order spin state preparation pulse composed of H, one or more gradient pulses and a conversion pulse for converting the Zeeman order spin state of the multi-spin coupling system into an observable magnetic resonance signal; the magnetic resonance signal acquisition module includes a radio frequency gradient pulse and a layer selection pulse, and uses a point decomposition spectroscopy method to realize the detection of methyl groups of lactic acid molecules in a specific space. 1 Selective observation of H magnetic resonance signals; and / or, In in vivo spectroscopy applications, water signal suppression is performed using pressurized water pulses.

10. Application of the method as claimed in any one of claims 1 to 9 in controlling the evolution of nuclear spin quantum states of specific groups of lactic acid molecules, achieving specific screening of lactic acid signals, and improving the intensity of molecular targeted nuclear magnetic resonance signals in the detection of lactic acid in living organisms for non-diagnostic purposes.

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