WO2018166250A1 - 一种抵抗不均匀磁场的超快速核磁共振二维j谱方法 - Google Patents

一种抵抗不均匀磁场的超快速核磁共振二维j谱方法 Download PDF

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WO2018166250A1
WO2018166250A1 PCT/CN2017/115473 CN2017115473W WO2018166250A1 WO 2018166250 A1 WO2018166250 A1 WO 2018166250A1 CN 2017115473 W CN2017115473 W CN 2017115473W WO 2018166250 A1 WO2018166250 A1 WO 2018166250A1
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sampling
dimensional
spectrum
pulse
magnetic field
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French (fr)
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陈忠
詹昊霖
叶奇淼
杨健
李弘�
黄玉清
蔡淑惠
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厦门大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
    • G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/46—NMR spectroscopy
    • G01R33/4616—NMR spectroscopy using specific RF pulses or specific modulation schemes, e.g. stochastic excitation, adiabatic RF pulses, composite pulses, binomial pulses, Shinnar-le-Roux pulses, spectrally selective pulses not being used for spatial selection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/46—NMR spectroscopy
    • G01R33/4633—Sequences for multi-dimensional NMR
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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    • G06F17/156—Correlation function computation including computation of convolution operations using a domain transform, e.g. Fourier transform, polynomial transform, number theoretic transform

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  • the invention relates to a nuclear magnetic resonance (NMR) spectroscopy molecular structure information detection technology, in particular to a method for obtaining a high resolution two-dimensional J spectrum by a single scan in a non-uniform magnetic field environment.
  • NMR nuclear magnetic resonance
  • nuclear magnetic resonance technology Due to the unique advantages of non-invasive detection of nuclear magnetic resonance spectroscopy, in recent decades, nuclear magnetic resonance technology has been widely used in the fields of biology, chemistry, physics, medicine and materials science.
  • scholar Jeener proposed the concept of two-dimensional spectrum on the basis of one-dimensional spectrum, and extended NMR from one-dimensional spectrum to two-dimensional spectrum.
  • the two-dimensional spectrum overcomes the problems of spectral crowding and spectral peaks that are often present in one-dimensional hydrogen spectra, and can transmit more molecular structure information and kinetic information.
  • the two-dimensional J-decomposition spectrum of nuclear magnetic resonance has the characteristics of direct dimension characterization of nuclear chemical shift information, indirect dimension characterization of scalar coupling split mode and coupling constant between nucleus, and is often applied to sample composition analysis and structure identification, which is nuclear magnetic An important means of analysis of resonance.
  • the existing method for obtaining the two-dimensional J-decomposition spectrum is a conventional sequence based on the spin echo module proposed by Richard R. Ernst in 1976.
  • the traditional two-dimensional J-spectral method provides a common method for obtaining nuclear chemical shifts and coupling information, there are some limitations in this technique.
  • the traditional two-dimensional J-spectrum method requires two-dimensional sampling, which takes a long time under the premise of ensuring the resolution of the spectrum.
  • the main technical problem to be solved by the present invention is to provide an ultra-fast nuclear magnetic resonance against an inhomogeneous magnetic field.
  • the two-dimensional J-spectrum method can quickly acquire high-resolution two-dimensional J-decomposition spectra with a single scan.
  • the single-scan two-dimensional J-decomposition spectrum method adopts a single-channel sampling method.
  • the present invention further provides a multi-channel sampling method capable of efficiently improving the above-mentioned single-scan J-spectrum signal-to-noise ratio, based on The multi-channel sampling of multi-color pulse excitation greatly improves the spectral signal-to-noise ratio performance.
  • the invention overcomes the shortcomings of the traditional two-dimensional J-spectrum acquisition method in practical application, and has important significance in improving the application range of the two-dimensional J-spectrum and detecting the chemical structure of the sample.
  • the present invention provides an ultra-fast nuclear magnetic resonance two-dimensional J-spectrum method based on single-channel sampling against a non-uniform magnetic field (especially a large single-directional linear inhomogeneous magnetic field), including the following steps. :
  • the sample tube containing the test sample is sent into the detection cavity of the nuclear magnetic resonance spectrometer, and the conventional one-dimensional hydrogen spectrum sequence is called to collect the one-dimensional hydrogen spectrum of the sample to be detected;
  • the conventional one-dimensional hydrogen spectrum sequence is a single pulse sequence integrated in a nuclear magnetic resonance spectrometer consisting of a non-selective RF pulse and a signal sampling period;
  • introducing a nuclear magnetic resonance pulse sequence designed by the invention on a nuclear magnetic resonance spectrometer the sequence comprising a selection excitation module and a re-sampling sampling module; setting experimental parameters of the selection excitation module and the re-sampling sampling module, and then performing data sampling;
  • the data processing is processed by calling the data post-processing code to obtain a two-dimensional J-decomposition spectrum that overcomes the unidirectional non-uniform magnetic field interference;
  • the data processing process is as follows: (a) Since the data collected by the odd-numbered sampling module and the even-numbered sampling module are from different order quantum, the parity data is separated during the processing, and the odd data (or even data) is separately extracted. (b) Performing a two-dimensional Fourier transform on the obtained odd-sampled data to obtain a high-resolution two-dimensional J-decomposition spectrum that is not affected by a unidirectional non-uniform magnetic field.
  • Step 3) the selective excitation module is composed of a ⁇ /2 selective Gaussian pulse and a unidirectional coding gradient and two compensation gradients simultaneously applied with the selective Gaussian pulse;
  • the direction of application of the unidirectional coding gradient and the compensation gradient is the same as the direction of the magnetic field non-uniformity in the actual detection;
  • the selective excitation module is configured to selectively flip the longitudinal magnetization vector of the sample to be tested to the xy lateral plane, and select the selected The nuclear precession frequency is associated with its spatial position;
  • the re-sampling module is composed of sampling modules that are repeated 2N times, each sampling module consisting of a sampling time TD and a non-selective 180° radio frequency pulse simultaneously acting with the single-direction decoding gradient;
  • the polysampling module is configured to decode the spectral information encoded in the selected excitation module to read a high resolution two-dimensional J-resolution spectrum.
  • the experimental parameters include a ⁇ /2 non-selective RF pulse width, a pulse width and RF power of a ⁇ /2 selective Gaussian pulse, a direct dimensional width SW, a coding gradient strength GE applied simultaneously with a selective Gaussian pulse, and a compensation gradient.
  • the invention further provides a multi-channel sampling method based on multi-color pulse excitation, which obtains a single-scan J spectrum with greatly improved signal-to-noise ratio.
  • the specific steps are basically the same as the single channel method described above, and the specific differences are as follows:
  • Step 2) further includes: generating a multi-color pulse using a Fourier coding technique, and generating a pulse width and a radio frequency power of the multi-color pulse according to an experiment requirement;
  • Step 3) the selection excitation module is composed of a multi-color pulse and a unidirectional coding gradient and two compensation gradients simultaneously applied with the multi-color pulse;
  • the direction of application of the unidirectional coding gradient and the compensation gradient is the same as the direction of the magnetic field non-uniformity in the actual detection;
  • the selective excitation module is configured to selectively flip the longitudinal magnetization vector of the sample to be tested to the xy lateral plane, and select the selected The nuclear precession frequency is associated with its spatial position;
  • the 2) Fourier-encoded multi-channel signal is first decoded; the data post-processing code is called for data processing, and the decoded signal is calibrated and superimposed to obtain the interference of the unidirectional non-uniform magnetic field. High signal-to-noise ratio two-dimensional J-resolution spectrum.
  • the present invention provides a method for obtaining a high resolution nuclear magnetic resonance two-dimensional J-decomposition spectrum by single scanning in a non-uniform magnetic field environment.
  • the method utilizes the joint action of the selective excitation module and the re-sampling sampling module to break through the limitations of the traditional two-dimensional J-spectral method, effectively eliminating the influence of the magnetic field inhomogeneity in the coding direction (z direction), and simultaneously rotating through the sample.
  • the magnetic field in the xy direction is not uniform, so that a single high-resolution two-dimensional J-spectrum is obtained by single-scan sampling in a magnetic field uneven environment, which greatly shortens the experimental time and expands the application field of the two-dimensional J-spectrum.
  • This method is applicable to conventional nuclear magnetic resonance spectrometers and does not require any special hardware devices. Moreover, it does not require any special sample pretreatment process, which is simple and easy, and provides an important means for quickly obtaining two-dimensional J-decomposition spectra of complex organic samples and biological tissue samples.
  • the method shown in Effect 1 is a single channel sampling method.
  • the present invention provides a multi-channel sampling method suitable for the above-mentioned single-scan J-spectrum signal-to-noise ratio improvement, which is based on multi-color pulse excitation.
  • Multi-channel sampling greatly improves spectral signal-to-noise performance.
  • N channel sampling can increase N times the signal to noise ratio
  • the invention provides an ultra-fast nuclear magnetic resonance two-dimensional J-spectrum method for resisting a non-uniform magnetic field, and the selection excitation module encodes spectral information by associating a selected nuclear nucleus precession frequency with its spatial position; re-sampling module decoding selection Exciting the spectral information encoded in the module to ensure the recombination of the chemical shift effect in the one-dimensional signal evolution process, while retaining only the J-coupling, and the other-dimensional signal contains the chemical displacement information related to the spatial position, thereby obtaining the two-dimensional J One-dimensional representation of the J-coupling information of the coupling relationship between the nucleus in the spectrum, and another dimension of the chemical displacement information of the nucleus in different chemical environments.
  • the ultra-fast nuclear magnetic resonance two-dimensional J-spectrum method for resisting uneven magnetic field provided by the present invention, the combination of the selective excitation module and the re-sampling sampling module in the above step (3) realizes different evolution of single experimental sampling.
  • the signal of time so that a single scan experiment can obtain a two-dimensional J spectrum, which greatly shortens the experiment time.
  • 1 is a pulse sequence diagram of an ultra-fast two-dimensional J-decomposition spectrum against an inhomogeneous magnetic field proposed by the present invention
  • the black hollow rectangular strip is a ⁇ non-selective RF pulse
  • the Gaussian shape strip is a ⁇ /2 selective Gaussian RF pulse (single channel sampling) or a multi-color pulse (multi-channel sampling)
  • the Sinc waveform represents the sampling process
  • the sampling time is TD
  • the solid rectangular bar represents the coding gradient GE
  • the linearly filled rectangular bar and the obliquely filled rectangular block respectively represent the compensation gradients GP1, GP2
  • the horizontally placed hollow rectangular bars represent the decoding gradient GD.
  • 2 is a conventional one-dimensional hydrogen spectrum of a sample of ethyl tribromopropionate solution dissolved in deuterated dimethyl sulfoxide in the case of a large uneven magnetic field in the z direction, and the line width of the inhomogeneous magnetic field is about 900 Hz.
  • Figure 4 is a projection of the J-coupling dimension at all chemical shifts in Figure 3, with scalar coupling splitting modes and corresponding coupling constants representing chemical shifts of approximately 4.2, 3.7, 3.0, and 1.3 ppm, respectively, from 1 to 4; .
  • Figure 5 is an experimental result of multi-channel sampling using multi-color pulse excitation proposed by the present invention (taking two-channel sampling as an example).
  • the sample used in the experiment was a sample of n-propanol solution dissolved in deuterated heavy water.
  • Figure 5(a) shows the change in the effective sample length for two-channel sampling relative to single-channel sampling. As shown, the effective sample length for dual-channel sampling is twice that of a single channel, which is theoretically doubled by two-channel sampling.
  • the signal-to-noise ratio (Fig. 5(b, c) is the two-dimensional J-decomposition spectrum and the projection spectrum of the chemical displacement dimension obtained by decoding the two channels respectively; Figure 5(d) is obtained after the two channels are calibrated and superimposed.
  • the invention provides a high-resolution two-dimensional J-decomposition spectrum capable of resisting magnetic field non-uniformity effects (especially a linear non-uniform magnetic field with a large unidirectional direction) and rapidly obtaining complex organic samples and biological tissue samples, thereby being useful for component analysis of samples and Structure Identification.
  • the method is simple to operate and does not require any sample pretreatment process. It can be applied to all conventional NMR spectrometers without any additional hardware.
  • Embodiment 1 Referring to FIG. 1-3, an ultra-fast nuclear magnetic resonance two-dimensional J-spectrum method for resisting an inhomogeneous magnetic field based on single-channel sampling is provided.
  • the steps of the specific implementation process are as follows:
  • Step 1 Sample loading and sampling of conventional one-dimensional hydrogen spectra
  • the test sample is loaded into a standard 5mm sample tube, and the sample tube is sent into the detection chamber of the nuclear magnetic spectrometer, and then the conventional one-dimensional hydrogen spectrum sequence is called to collect the one-dimensional hydrogen spectrum of the sample to be detected (as shown in FIG. 2). , get its signal line width information.
  • the conventional one-dimensional hydrogen spectrum sequence is a single pulse sequence composed of a non-selective RF pulse and a signal sampling period integrated in the nuclear magnetic resonance spectrometer, and the step can obtain the signal spectral width and the magnetic field uniformity information after the sample is placed.
  • the parameter settings in the following steps provide a reference.
  • the z-direction magnetic field is artificially adjusted during the experiment.
  • Step 2 measuring the RF pulse width
  • the ⁇ /2 and ⁇ non-selective RF pulse widths required to excite the sample, and the pulse width and RF power of the ⁇ /2 selective Gaussian pulse are measured.
  • the RF pulse width is twice the width of the ⁇ /2 non-selective RF pulse.
  • the pulse type of the above single pulse sequence is changed. For a Gaussian pulse, repeat the above steps to determine the pulse width and RF power of the selective Gaussian pulse required to excite the sample;
  • Step 3 import the pulse sequence and set the experimental parameters for sampling
  • the nuclear magnetic resonance pulse sequence designed by the method is introduced on a nuclear magnetic resonance spectrometer, and includes an excitation module and a refocusing sampling module.
  • the selective excitation module is composed of a ⁇ /2 selective Gaussian pulse and a unidirectional coding gradient and two compensation gradients simultaneously applied with the selective Gaussian pulse; the unidirectional coding gradient, the application direction of the compensation gradient and the actual detection
  • the medium magnetic field has the same non-uniform direction; the selective excitation module is configured to selectively flip the longitudinal magnetization vector of the sample to be tested to the xy lateral plane, and associate the selected nuclear nucleus precession frequency with its spatial position;
  • the re-sampling module is composed of sampling modules that are repeated 2N times, each sampling module consisting of a sampling time TD and a non-selective 180° radio frequency pulse simultaneously acting with the single-direction decoding gradient;
  • the polysampling module is configured to decode the spectral information encoded in the selected excitation module to read a high resolution two-dimensional J-resolution spectrum.
  • the experimental parameters of the two modules are reasonably set, including ⁇ /2 non-selective RF pulse width, pulse width and RF power of ⁇ /2 selective Gaussian pulse, direct dimensional wide SW, and simultaneous application of selective Gaussian pulse.
  • Step 4 data post processing
  • the data post-processing code is called for data processing.
  • the main processing process is as follows: (a) Since the data collected by the odd-numbered sampling module and the even-numbered sampling module are from different order quantum, the parity data is separated during processing. , extracting odd-numbered data or even-numbered data separately for data processing; (b) performing two-dimensional Fourier transform on the obtained odd-sampled data or even-numbered-sampling data to obtain a magnetic field that can resist one-direction large magnetic field Uniform two-dimensional J-spectrum.
  • Embodiment 2 On the basis of Embodiment 1, the present invention expands to a multi-channel sampling method based on multi-color pulse excitation to obtain a single-scan J spectrum with greatly improved signal-to-noise ratio.
  • the specific steps are basically the same as the single channel method described above, and include the following steps:
  • the sample tube containing the test sample is sent into the detection cavity of the nuclear magnetic resonance spectrometer, and the conventional one-dimensional hydrogen spectrum sequence is called to collect the one-dimensional hydrogen spectrum of the sample to be detected;
  • the conventional one-dimensional hydrogen spectrum sequence is a single pulse sequence integrated in a nuclear magnetic resonance spectrometer consisting of a non-selective RF pulse and a signal sampling period;
  • introducing a nuclear magnetic resonance pulse sequence designed by the invention on a nuclear magnetic resonance spectrometer the sequence comprising a selection excitation module and a re-sampling sampling module; setting experimental parameters of the selection excitation module and the re-sampling sampling module, and then performing data sampling;
  • the re-sampling module is composed of sampling modules that are repeated 2N times, each sampling module consisting of a sampling time TD and a non-selective 180° radio frequency pulse simultaneously acting on the single-direction decoding gradient;
  • the data processing is processed by calling the data post-processing code to obtain a two-dimensional J-decomposition spectrum that overcomes the unidirectional non-uniform magnetic field interference;
  • the data processing process is as follows: (a) Since the data collected by the odd-numbered sampling module and the even-numbered sampling module are from different order quantum, the parity data is separated during the processing, and the odd data (or even data) is separately extracted. (b) Performing a two-dimensional Fourier transform on the obtained odd-sampled data to obtain a high-resolution two-dimensional J-decomposition spectrum that is not affected by a unidirectional non-uniform magnetic field.
  • Step 2) further includes: generating a multi-color pulse using a Fourier coding technique, and generating a pulse width and a radio frequency power of the multi-color pulse according to an experiment requirement;
  • Step 3) the selection excitation module is composed of a multi-color pulse and a unidirectional coding gradient and two compensation gradients simultaneously applied with the multi-color pulse;
  • the direction of application of the unidirectional coding gradient and the compensation gradient is the same as the direction of the magnetic field non-uniformity in the actual detection;
  • the selective excitation module is configured to selectively flip the longitudinal magnetization vector of the sample to be tested to the xy lateral plane, and select the selected The nuclear precession frequency is associated with its spatial position;
  • Step 4) After the data sampling is completed, the multi-channel signal encoded by 2) is first decoded; the data processing is performed by calling the data post-processing code, and the unidirectional non-uniform magnetic field is obtained by calibrating and superimposing the decoded signal. High signal-to-noise ratio two-dimensional J-decomposition spectrum of interference.
  • the sample used in the above examples is a sample of ethyl tribromopropionate solution dissolved in deuterated dimethyl sulfoxide and A sample of n-propanol solution in deuterated heavy water was used for the Varian 500 MHz NMR spectroscopy.
  • the z-direction magnetic field was artificially adjusted during the single-channel experiment. According to the operation flow proposed by the present invention, the experimental sample is loaded, the RF pulse width required for the pulse sequence is measured, and the compiled pulse sequence as shown in FIG. 1 is introduced, and the corresponding experimental parameters are set.
  • ⁇ non-selective RF pulse width is 30.3 s
  • pulse width and RF power of ⁇ /2 selective Gaussian pulse are 96.2 ms and - 6dB
  • direct dimensional spectral width SW 25000Hz
  • encoding gradient intensity GE applied simultaneously with selective Gaussian pulse is 0.28G/cm
  • compensation gradient GP1 intensity is -13.5G/cm
  • action time is 1.0ms
  • the intensity of GP2 is -12.1G/cm
  • the action time is 1.5ms
  • the pulse sequence wait time is 1 s.
  • the entire experiment took about 5 s.
  • the original data is processed according to the above data post-processing process, and the two-dimensional J-spectrum shown in FIG. 3 can be obtained, wherein the vertical axis of the two-dimensional J-spectrum indicates the scalar coupling splitting mode in the detection molecule and corresponding Coupling constant; the horizontal axis represents the chemical shift of the nucleus in different chemical environments. Therefore, the figure can be used as an important basis for component analysis and structure identification of the test sample.
  • decoding gradient intensity GD 3.8G/cm
  • sampling module repetition number 2N 120
  • sampling point number np 54000
  • pulse sequence waiting time is 6s. The entire experiment took about 12 seconds.
  • the original data is processed according to the above-mentioned multi-channel sampled data post-processing process, and the experimental results are shown in FIG. 5.
  • the invention provides a method for ultra-fast acquisition of high-resolution nuclear magnetic resonance two-dimensional J-decomposition spectra in a non-uniform magnetic field environment.
  • the method utilizes the joint action of the selective excitation module and the re-sampling sampling module to break through the limitations of the traditional two-dimensional J-spectrum, effectively eliminating the influence of the magnetic field inhomogeneity in the coding direction (z-direction), and theoretically speaking through the slow rotation of the sample. Eliminate the non-uniform magnetic field in the xy direction, so that a single scan in a non-uniform magnetic field Sampling to obtain high-resolution two-dimensional J-spectrum greatly shortens the experimental time and expands the application field of two-dimensional J-spectrum. Meanwhile, based on the above single channel sampling, the present invention further provides a multi-channel sampling method capable of efficiently improving the signal-to-noise ratio of the single-scan J-spectrum described above.

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Abstract

一种在不均匀磁场环境下超快速获取高分辨核磁共振二维J分解谱的方法，利用选择激发模块和重聚采样模块的共同作用，突破了传统二维J谱的局限，有效地消除了编码方向(z方向)磁场不均匀的影响，通过样品的慢速旋转理论上消除xy方向磁场不均匀，从而在磁场不均匀环境下单次扫描获得高分辨谱图，大大缩短了实验时间，扩展了二维J谱的应用领域。基于单通道采样，还提供了一种可以高效地提高单扫描J谱信噪比的多通道采样方法。

Description

一种抵抗不均匀磁场的超快速核磁共振二维J谱方法 技术领域
本发明涉及核磁共振(Nuclear Magnetic Resonance，NMR)波谱学分子结构信息检测技术，尤其是涉及一种在不均匀磁场环境下单扫描超快速获取高分辨二维J谱的方法。
背景技术
由于核磁共振波谱技术具有无损性非侵入式检测的独特优势，近几十年来，核磁共振技术在生物、化学、物理、医学以及材料学等学科领域获得了广泛的应用。1971年，学者Jeener在一维谱的基础上提出了二维谱的概念，将NMR从一维谱扩展到二维谱。在常规的核磁共振谱学检测中，二维谱克服了一维氢谱中经常存在的谱图拥挤和谱峰归属困难等问题，可传递更多的分子结构信息和动力学信息。其中，核磁共振二维J分解谱具有直接维表征原子核化学位移信息，间接维表征原子核间的标量偶合裂分模式及偶合常数的特点，被经常应用于样品的组分分析和结构鉴定，是核磁共振的一个重要分析手段。现有的获取二维J分解谱的方法是Richard R.Ernst于1976年提出的基于自旋回波模块的传统序列。虽然传统二维J谱方法提供了一种普遍的获取原子核化学位移及偶合信息的方法，但是在实际应用中，该技术存在一些限制。首先，传统二维J谱方法需要二维采样，在保证谱图分辨率的前提下，耗时较长。这一问题限制了该方法在实时监控化学反应等领域的应用，同时也限制了该方法向多维谱发展应用。其次，传统二维J谱的获取受限于磁场均匀度，需要在较均匀磁场下才能得到理想的二维J谱。在实际应用中，对于均相溶液样品体系，需要对检测样品进行复杂耗时的匀场操作，从而获取较理想的磁场环境；而对于粘稠性样品和生物组织样品等非均相样品而言，其样品自身磁化率会带来磁场大不均匀性，足够高的磁场均匀度往往是很难甚至是不可能获得的。这一问题同样限制了传统J谱方法的应用范围。
发明内容
本发明所要解决的主要技术问题是提供一种抵抗不均匀磁场的超快速核磁共 振二维J谱方法，只需单次扫描即可快速获取高分辨二维J分解谱。上述单扫描二维J分解谱方法采用的是单通道采样方法，在此基础上，本发明又提供了一种能够高效率地提高上述单扫描J谱信噪比的多通道采样方法，通过基于多色脉冲激发的多通道采样，大幅度地提高了谱图信噪比性能。本发明克服了传统二维J谱获取方法在实际应用中的不足，在提高二维J谱的应用范围和检测样品化学结构方面具有重要意义。
为了解决上述的技术问题，首先，本发明提供了一种基于单通道采样的抵抗不均匀磁场(尤其是大的单方向线性不均匀磁场)的超快速核磁共振二维J谱方法，包括如下步骤：
1)样品装样及采样常规一维氢谱
将装有检测样品的样品管送入核磁共振谱仪的检测腔中，调用常规一维氢谱序列采集待检测样品的一维氢谱；
所述常规一维氢谱序列是集成在核磁共振谱仪中由一个非选择性射频脉冲和信号采样期组成的单脉冲序列；
2)测量射频脉冲宽度
使用所述单脉冲序列测量激发样品所需的π/2非选择性射频脉冲宽度；
3)导入脉冲序列及设置实验参数进行采样
在核磁共振谱仪上导入本发明所设计的核磁共振脉冲序列，该序列包括选择激发模块和重聚采样模块；设置选择激发模块和重聚采样模块的实验参数，然后进行数据采样；
4)数据后处理：
数据采样完成后，调用数据后处理代码进行数据处理，即可获得克服单方向不均匀磁场干扰的二维J分解谱；
所述数据处理的过程如下：(a)由于奇数次采样模块和偶数次采样模块所采集的数据来自不同阶量子，在处理过程中将奇偶数据分开，单独提取奇次数据(或偶次数据)进行处理；(b)对得到的奇数次采样数据进行二维傅里叶变换，即可获得一张不受单方向不均匀磁场影响的高分辨二维J分解谱。
进一步：
步骤3)所述选择激发模块是由一个π/2选择性高斯脉冲以及与选择性高斯脉冲同时施加的单方向编码梯度和两个补偿梯度组成；
所述单方向编码梯度、补偿梯度的施加方向与实际检测中磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
所述的重聚采样模块是由重复2N次的采样模块构成，每个采样模块由与所述单方向解码梯度同时作用的采样时间TD和一个非选择性180°射频脉冲组成；所述的重聚采样模块用于解码选择激发模块中编码的谱图信息，从而读出一张高分辨的二维J分解谱。
所述实验参数包括π/2非选择性射频脉冲宽度、π/2选择性高斯脉冲的脉冲宽度和射频功率、直接维谱宽SW、与选择性高斯脉冲同时施加的编码梯度强度GE，补偿梯度强度GP1、GP2及作用时间，每次采样模块采样时间TD、解码梯度强度GD、采样模块重复次数2N、采样点数np。
本发明又提供了一种基于多色脉冲激发的多通道采样的方法，获取信噪比大幅度提高的单扫描J谱。其具体步骤基本与上述单通道方法相同，具体差异如下：
步骤2)还包括：使用傅里叶编码技术生成多色脉冲，并根据实验需要生成多色脉冲的脉冲宽度和射频功率；
步骤3)所述选择激发模块是由一个多色脉冲以及与多色脉冲同时施加的单方向编码梯度和两个补偿梯度组成；
所述单方向编码梯度、补偿梯度的施加方向与实际检测中磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
4)数据采样完成后，首先将2)中傅里叶编码的多通道信号进行解码；调用数据后处理代码进行数据处理，并对解码信号校准和叠加，即可获得克服单方向不均匀磁场干扰的高信噪比二维J分解谱。
相较于现有技术，本发明的技术方案具备以下有益效果：
1.本发明提供了一种在不均匀磁场环境下单扫描获取高分辨核磁共振二维J分解谱的方法。本方法利用选择激发模块和重聚采样模块的共同作用，突破了传统二维J谱方法的局限性，有效地消除了编码方向(z方向)磁场不均匀的影响，同时通过样品的慢速旋转理论上消除xy方向磁场不均匀，从而在磁场不均匀环境下单次扫描采样获得一张高分辨二维J谱，大大缩短了实验时间，扩展了二维J谱的应用领域。本方法适用于常规核磁共振波谱仪，不需要任何特殊硬件装置， 而且无需任何特殊的样品预处理过程，简便易行，为快速获取复杂有机样品及生物组织样品的二维J分解谱提供了一种重要手段。
2.效果1中所示方法为单通道采样方法，在此基础上，本发明提供了一种适用于上述单扫描J谱的信噪比提高的多通道采样方法，通过基于多色脉冲激发的多通道采样，大幅度地提高谱图信噪比性能。理论上，N个通道采样可以提高N倍的信噪比
3.本发明提供的一种抵抗不均匀磁场的超快速核磁共振二维J谱方法，选择激发模块通过将选择的原子核进动频率与其空间位置相关联编码谱图信息；重聚采样模块解码选择激发模块中编码的谱图信息，保证一维信号演化过程化学位移效应的重聚，而仅保留J偶合作用，另一维信号包含与空间位置有关的化学位移信息，从而使得获得的二维J谱中的一维表征原子核间的偶合关系的J偶合信息，另一维表征不同化学环境中原子核的化学位移信息。
4.本发明提供的一种抵抗不均匀磁场的超快速核磁共振二维J谱方法，上述步骤(3)中的选择激发模块和重聚采样模块的共同作用实现了单次实验采样得到不同演化时间的信号，从而只需单次扫描实验即可获得一张二维J谱，大大缩短了实验时间。
附图说明
图1为本发明提出的抵抗不均匀磁场的超快速二维J分解谱脉冲序列图；
图中黑色空心矩形条为π非选择性射频脉冲，高斯形状条为π/2选择性高斯射频脉冲(单通道采样)或者多色脉冲(多通道采样)，Sinc波形表示采样过程，采样时间为TD，实心矩形条表示编码梯度GE，直线填充的矩形条与斜线填充的矩形块分别表示补偿梯度GP1、GP2，横放的空心矩形条表示解码梯度GD。
图2为在z方向较大不均匀磁场情况下，溶于氘代二甲基亚砜的三溴丙酸乙酯溶液样品的常规一维氢谱，不均匀磁场线宽约为900Hz。
图3为在磁场不均匀情况下，本发明提出基于单通道采样的三溴丙酸乙酯溶液样品的超快速二维J分解谱，该实验的整个数据采样时间约4s。
图4为图3中的所有化学位移处的J偶合维的投影所得到，图中从1到4分别表示化学位移约为4.2、3.7、3.0、1.3ppm的标量偶合裂分模式及对应偶合常数。
图5为本发明提出的使用多色脉冲激发的多通道采样的实验结果(以双通道采样为例)。实验使用的样品为溶于氘代重水的正丙醇溶液样品。图5(a)为相对于单通道采样，双通道采样的有效样品长度的变化，如图所示，双通道采样的有效样品长度为单通道的两倍，即理论上双通道采样提高两倍的信噪比；图5(b，c)为两个通道分别解码得到的二维J分解谱及其化学位移维的投影谱；图5(d)为上述两个通道经过校准叠加之后得到的两倍信噪比的分解谱及其化学位移维的投影谱；图5(e)为作为参考的没使用多色脉冲激发的单通道采样得到的二维J分解谱及其化学位移维的投影谱。
具体实施方式
下文结合附图和具体实施方式对本发明做进一步说明。
本发明提出的能够抵抗磁场不均匀效应(尤其是单方向大的线性不均匀磁场)并快速获得复杂有机样品及生物组织样品的高分辨二维J分解谱，从而可用于样品的组分分析和结构鉴定。该方法操作简单，无需任何样品预处理过程，可适用于所有常规核磁共振波谱仪，不需要任何额外硬件装置。
实施例1、参考图1-3，本发明一种基于单通道采样的抵抗不均匀磁场的超快速核磁共振二维J谱方法，具体实施过程的各个步骤如下：
步骤1，样品装样及采样常规一维氢谱
将检测样品装入标准5mm样品管中，并将该样品管送入核磁谱仪的检测腔内，然后调用常规一维氢谱序列采集待检测样品的一维氢谱(如图2所示)，获得其信号线宽信息。该常规一维氢谱序列是集成在核磁共振谱仪中的一个非选择性射频脉冲和信号采样期组成的单脉冲序列，该步骤可以获取样品放置完成后信号谱宽及磁场均匀性信息，为下面步骤中的参数设置提供参考。同时为证明本方法抵抗单方向磁场不均匀性的性能，实验过程中人为调偏z方向磁场。
步骤2，测量射频脉冲宽度
测量激发样品所需的π/2和π非选择性射频脉冲宽度，及π/2选择性高斯脉冲的脉冲宽度和射频功率。利用步骤1中的单脉冲序列并设置一系列脉冲作用时间采样相应信号，测量磁化矢量由纵向方向翻转到xy平面所对应的脉冲时间，即为π/2非选择性射频脉冲宽度，π非选择性射频脉冲宽度则为π/2非选择性射频脉冲宽度的两倍。同时，对于单通道采样技术，将上述单脉冲序列的脉冲类型改 为高斯型脉冲，重复上述步骤，测定激发样品所需的选择性高斯脉冲的脉冲宽度和射频功率；
步骤3，导入脉冲序列及设置实验参数进行采样
在核磁共振波谱仪上导入本方法所设计的核磁共振脉冲序列(如图1所示)，包括选择激发模块和重聚采样模块。所述选择激发模块是由一个π/2选择性高斯脉冲以及与选择性高斯脉冲同时施加的单方向编码梯度和两个补偿梯度组成；所述单方向编码梯度、补偿梯度的施加方向与实际检测中大的磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
所述的重聚采样模块是由重复2N次的采样模块构成，每个采样模块由与所述单方向解码梯度同时作用的采样时间TD和一个非选择性180°射频脉冲组成；所述的重聚采样模块用于解码选择激发模块中编码的谱图信息，从而读出一张高分辨的二维J分解谱。
同时合理设置两个模块的实验参数，包括π/2非选择性射频脉冲宽度、π/2选择性高斯脉冲的脉冲宽度和射频功率、直接维谱宽SW、与选择性高斯脉冲同时施加的编码梯度强度GE，补偿梯度强度GP1、GP2及作用时间，每次采样模块采样时间TD、解码梯度强度GD、采样模块重复次数2N、采样点数np，直接进行数据采样。
步骤4，数据后处理
数据采样完成后，调用数据后处理代码进行数据处理，其主要处理过程如下：(a)由于奇数次采样模块和偶数次采样模块所采集的数据来自不同阶量子，在处理过程中将奇偶数据分开，单独提取奇数次数据或偶数次数据进行数据处理；(b)对得到的奇次采样数据或偶数次采样数据进行二维傅里叶变换，即可获得一张可以抵抗单方向大的磁场不均匀的二维J谱。
实施例2，在实施例1的基础上本发明扩展为一种基于多色脉冲激发的多通道采样的方法，获取信噪比大幅度提高的单扫描J谱。其具体步骤基本与上述单通道方法相同，包括如下步骤：
1)样品装样及采样常规一维氢谱
将装有检测样品的样品管送入核磁共振谱仪的检测腔中，调用常规一维氢谱序列采集待检测样品的一维氢谱；
所述常规一维氢谱序列是集成在核磁共振谱仪中由一个非选择性射频脉冲和信号采样期组成的单脉冲序列；
2)测量射频脉冲宽度
使用所述单脉冲序列测量激发样品所需的π/2非选择性射频脉冲宽度；
3)导入脉冲序列及设置实验参数进行采样
在核磁共振谱仪上导入本发明所设计的核磁共振脉冲序列，该序列包括选择激发模块和重聚采样模块；设置选择激发模块和重聚采样模块的实验参数，然后进行数据采样；
所述的重聚采样模块是由重复2N次的采样模块构成，每个采样模块由与所述单方向解码梯度同时作用的采样时间TD和一个非选择性180°射频脉冲组成；
4)数据后处理：
数据采样完成后，调用数据后处理代码进行数据处理，即可获得克服单方向不均匀磁场干扰的二维J分解谱；
所述数据处理的过程如下：(a)由于奇数次采样模块和偶数次采样模块所采集的数据来自不同阶量子，在处理过程中将奇偶数据分开，单独提取奇次数据(或偶次数据)进行处理；(b)对得到的奇数次采样数据进行二维傅里叶变换，即可获得一张不受单方向不均匀磁场影响的高分辨二维J分解谱。
具体差异如下：
步骤2)还包括：使用傅里叶编码技术生成多色脉冲，并根据实验需要生成多色脉冲的脉冲宽度和射频功率；
步骤3)所述选择激发模块是由一个多色脉冲以及与多色脉冲同时施加的单方向编码梯度和两个补偿梯度组成；
所述单方向编码梯度、补偿梯度的施加方向与实际检测中磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
步骤4)数据采样完成后，首先将2)中傅里叶编码的多通道信号进行解码；调用数据后处理代码进行数据处理，并对解码信号校准和叠加，即可获得克服单方向不均匀磁场干扰的高信噪比二维J分解谱。
上述实例中所使用的样品为溶于氘代二甲基亚砜的三溴丙酸乙酯溶液样品及 溶于氘代重水的正丙醇溶液样品，使用的仪器为Varian 500MHz核磁共振波谱议。为证明本方法抵抗磁场不均匀性的性能，单通道实验过程中人为调偏z方向磁场。按照上述本发明所提出的操作流程，装入实验样品，测量脉冲序列所需的射频脉冲宽度，导入编译好的如图1所示脉冲序列，设置相应实验参数。具体对于本实例所采用的样品，本次单通道实验的具体参数设置如下：π非选择性射频脉冲宽度为30.3s；π/2选择性高斯脉冲的脉冲宽度和射频功率分别为96.2ms和-6dB；直接维谱宽SW＝25000Hz；与选择性高斯脉冲同时施加的编码梯度强度GE为0.28G/cm，补偿梯度GP1强度为-13.5G/cm，作用时间为1.0ms、第二个补偿梯度GP2强度为-12.1G/cm，作用时间为1.5ms，每次采样模块采样时间TD＝14.0ms，解码梯度强度GD＝3.6G/cm，采样模块重复次数2N＝280，采样点数np＝196000，脉冲序列等待时间为1s。整个实验用时约为5s。数据采样完成后，按照上述数据后处理过程对原始数据进行处理，可得到如图3所示的二维J谱，其中，二维J谱纵轴表示检测分子内的标量偶合裂分模式及相应偶合常数；横轴表示不同化学环境中原子核的化学位移。因此，该图可作为对检测样品的进行组分分析和结构鉴定的一个重要依据。本次多通道实验的具体参数设置如下：π非选择性射频脉冲宽度为20.45s；多色脉冲的脉冲宽度和射频功率分别为120.0ms和-10dB；直接维谱宽SW＝25000Hz；与选择性高斯脉冲同时施加的编码梯度强度GE为0.42G/cm，补偿梯度GP1强度为-25.3G/cm，作用时间为1.0ms、第二个补偿梯度GP2强度为-11.5G/cm，作用时间为1.5ms，每次采样模块采样时间TD＝9.0ms，解码梯度强度GD＝3.8G/cm，采样模块重复次数2N＝120，采样点数np＝54000，脉冲序列等待时间为6s。整个实验用时约为12s。数据采样完成后，按照上述多通道采样的数据后处理过程对原始数据进行处理，实验结果如图5所示。
上文所述，仅为本发明较佳的实施范例，不能依此限定本发明实施的范围。即依本发明专利范围及说明书内容所作的等效变化与修饰，皆应仍属本发明涵盖的范围内。
工业实用性
本发明提供了一种在不均匀磁场环境下超快速获取高分辨核磁共振二维J分解谱的方法。本方法利用选择激发模块和重聚采样模块的共同作用，突破了传统二维J谱的局限性，有效地消除了编码方向(z方向)磁场不均匀的影响，通过样品的慢速旋转理论上消除xy方向磁场不均匀，从而在磁场不均匀环境下单次扫描 采样获得高分辨二维J谱，大大缩短了实验时间，扩展了二维J谱的应用领域。同时，基于上述单通道采样，本发明又提供了一种可以高效地提高上述单扫描J谱信噪比的多通道采样方法。

Claims (4)

  1. 一种基于单通道采样的抵抗不均匀磁场的超快速核磁共振二维J谱方法，其特征在于包括如下步骤：
    1)样品装样及采样常规一维氢谱
    将装有检测样品的样品管送入核磁共振谱仪的检测腔中，调用常规一维氢谱序列采集待检测样品的一维氢谱；
    所述常规一维氢谱序列是集成在核磁共振谱仪中由一个非选择性射频脉冲和信号采样期组成的单脉冲序列；
    2)测量射频脉冲宽度
    使用所述单脉冲序列测量激发样品所需的π/2非选择性射频脉冲宽度；
    3)导入脉冲序列及设置实验参数进行采样
    在核磁共振谱仪上导入本发明所设计的核磁共振脉冲序列，该序列包括选择激发模块和重聚采样模块；设置选择激发模块和重聚采样模块的实验参数，然后进行数据采样；
    4)数据后处理：
    数据采样完成后，调用数据后处理代码进行数据处理，即可获得克服单方向不均匀磁场干扰的二维J分解谱；
    所述数据处理的过程如下：(a)由于奇数次采样模块和偶数次采样模块所采集的数据来自不同阶量子，在处理过程中将奇偶数据分开，单独提取奇次数据(或偶次数据)进行处理；(b)对得到的奇数次采样数据进行二维傅里叶变换，即可获得一张不受单方向不均匀磁场影响的高分辨二维J分解谱。
  2. 根据权利要求1所述的一种基于单通道采样的抵抗不均匀磁场的超快速核磁共振二维J谱方法，其特征在于：
    步骤3)所述选择激发模块是由一个π/2选择性高斯脉冲以及与选择性高斯脉冲同时施加的单方向编码梯度和两个补偿梯度组成；
    所述单方向编码梯度、补偿梯度的施加方向与实际检测中磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
    所述的重聚采样模块是由重复2N次的采样模块构成，每个采样模块由与所述单方向解码梯度同时作用的采样时间TD和一个非选择性180°射频脉冲组成；所述的重聚采样模块用于解码选择激发模块中编码的谱图信息，从而读出一张高分辨的二维J分解谱。
    所述实验参数包括π/2非选择性射频脉冲宽度、π/2选择性高斯脉冲的脉冲宽度和射频功率、直接维谱宽SW、与选择性高斯脉冲同时施加的编码梯度强度GE，补偿梯度强度GP1、GP2及作用时间，每次采样模块采样时间TD、解码梯度强度GD、采样模块重复次数2N、采样点数np。
  3. 根据权利要求1所述的一种基于单通道采样的抵抗不均匀磁场的超快速核磁共振二维J谱方法，进一步扩展为一种基于多色脉冲激发的多通道采样的方法，其特征在于：
    步骤2)还包括：使用傅里叶编码技术生成多色脉冲，并根据实验需要生成多色脉冲的脉冲宽度和射频功率；
    步骤3)所述选择激发模块是由一个多色脉冲以及与多色脉冲同时施加的单方向编码梯度和两个补偿梯度组成；
    所述单方向编码梯度、补偿梯度的施加方向与实际检测中磁场不均匀方向相同；所述选择激发模块用于将待测样品的纵向磁化矢量选择性地翻转到xy横向平面，并将选择的原子核进动频率与其空间位置相关联；
    4)数据采样完成后，首先将2)中傅里叶编码的多通道信号进行解码；调用数据后处理代码进行数据处理，并对解码信号校准和叠加，即可获得克服单方向不均匀磁场干扰的高信噪比二维J分解谱。
  4. 根据权利要求2或3所述的一种抵抗不均匀磁场的超快速核磁共振二维J谱方法，其特征在于所述的样品管为标准5mm样品管。
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