An automatic search shimming method based on line shape fitting of inhomogeneous magnetic field

Abstract

The invention discloses an automatic searching and shimming method based uneven magnetic field fitting linearity. The method includes: using a gradient echo pulse sequence to measure the uneven image of a spatial magnetic field, using the same to fit and represent the virtual spectrogram line and related performance indexes of the current magnetic field evenness; using the related performance indexes of the virtual spectrogram line as the evaluation standard for obtaining good or bad magnetic field evenness according to the multidimensional spatial vectors built by a shimming coil, performing multidimensional descending simplex method iteration search according to the evaluation standard, and returning the optimal shimming current. The method has the advantages hat during shimming, the performance indexes such as half-width and symmetry of spectrum can be fully considered; compared with the gradient shimming using gradient echo imaging, the shimming method does not need to consider measurement and fitting the shimming coil field graphs, and the shimming difficulty and limit requirements by the aid of gradient imaging are lowered; automatic fitting and searching and convergence conditions allows the method to get rid of complex manual configuration, and shimming speed and efficiency are increased.

Description

technical field [0001] The invention relates to a shimming technology of a nuclear magnetic resonance spectrometer, and more particularly relates to an automatic search shimming method based on an inhomogeneous magnetic field fitting line shape. It is suitable for high-resolution NMR experiment shimming. Background technique [0002] For modern liquid nuclear magnetic resonance (NMR) spectrometers, the resolution is an important indicator, and one of the main factors affecting the resolution of the spectrum is the spatial uniformity of the magnetic field. Since the NMR signal broadening caused by the inhomogeneity of the static magnetic field will inevitably lead to significant errors in the experimental results, so since the discovery of the NMR phenomenon, how to improve the uniformity (shimming) of the static magnetic field has always been a very important research work . [0003] With the development of spectrometer technology in recent decades, the current automatic s...

AI Technical Summary

Problems solved by technology

This introduces two problems: 1) The lock level or FID area is used as a convenient and intuitive basis for judging whether the magnetic field is good or bad, and it may not be able to achieve a good shimming effect (spectral linear standard)

The process of making the shim coil field diagram is a bit complicated and time-consuming

At the same time, the imaging of the spatial influence of the shim coil must be carried out in a relatively uniform magnetic field environment. A magnetic field with poor uniformity will easily distort the measured data of the shim coil field map and affect the fitting.

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