Study On Ultrafast Two-dimensional NMR Spectroscopy Based On Spatially Encode Technique

High resolution nuclear magnetic resonance(NMR)spectroscopy is an effective technique to obtain molecular information of biological tissue in non-invasive state and is widely used in various fields.The traditional two-dimensional spectrum technique breaks through the limitation of the one-dimensional spectrum technique,distributes the signal peak in the two-dimensional plane,solves the spectral aliasing to a certain extent,and improves the resolution of the spectrum.However,these methods tend to experiment with a long acquiring time,which limits its development in many areas,such as real-time monitoring of chemical reactions.In order to solve the problem of long acquiring time,many fast methods to access high-dimensional spectrum are proposed.Ultrafast spatiotemporal encoding technology,which is one of such methods,obtains a two-dimensional spectral data in the order of seconds.Compared with the traditional two-dimensional spectrum technology,ultrafast spatiotemporal encoding method greatly shortens the acquiring time.However,this method is generally considered to have some shortcomings:the contradiction between spectral width and spectral resolution of the sample with large spectral width;the need for good uniformity of magnetic field;and the demand of higher hardware requirements.In this paper,we study the ultrafast spatiotemporal encoding technology,and from the improved conventional spatiotemporal encoding sequence to the post-processing of the acquiring data,we propose two methods to improve the ultrafast spatiotemporal encoding technology to obtain two-dimensional spectrum with higher resolution,higher signal-to-noise ratio and better peak shape.The main results are as follows:First,the basic principle of nuclear magnetic resonance(NMR)is expounded,and the coding and decoding principle of ultrafast spatiotemporal encoding technology is deduced and described.The chirp pulse and chronological modulation mechanism are introduced.Second,we improve the regular ultrafast space coding correlation spectrum sequence,and to a certain extent,improve the problem of contradiction between spectral width and resolution.The signal-to-noise ratio and sample applicability of the method are analyzed,and the method is used in combination with other methods to further improve the spectral width problem.Finally,we get a larger spectral width in the conventional ultrafast coding method at the same resolution.Third,based on the conventional ultrafast spatiotemporal encoding sequence,the data post-processing method is improved,and the concept of inverse-k-space is proposed.The phase correction and amplitude correction are performed on the inverse-k-space to improve the quality of the spectrum under inhomogeneity magnetic field.And the high-resolution two-dimensional spectrum is obtained by using the ultrafast spatiotemporal encoding method under inhomogeneity magnetic field.Finally,we verify the availability of the calibration method using the real-time monitoring of chemical reactions.