A method for fitting magnetic resonance imaging multi-echo magnetic field distribution map

Abstract

The invention discloses a method for fitting magnetic resonance imaging multi-echo magnetic field distribution diagrams. The method comprises the following steps: collecting original magnetic resonance data by using multi-echo gradient echo sequences; and checking the phases of all echoes for linearity , discard part or all of the echo signals of the data points with poor linearity; use the nonlinear least squares method to fit the phase diagram after the linearity check to obtain a preliminary magnetic field distribution diagram; use the surrounding reliable data points (phase linearity The average value of the local magnetic field of the good point) is used to replace the local magnetic field of the point where the echo signal is all discarded, and finally a complete magnetic field distribution map is obtained. The invention can reduce the fitting error of the magnetic field distribution map, and improve the signal-to-noise ratio and accuracy of the magnetic susceptibility distribution map of the skull base and other parts.

Description

technical field [0001] The invention relates to the technical field of magnetic resonance imaging, in particular to a method for fitting magnetic resonance imaging multi-echo magnetic field distribution maps. Background technique [0002] Magnetic resonance quantitative susceptibility imaging acquires complex data through gradient echo sequences, and then uses phase information to reconstruct local susceptibility distribution maps. Quantitative magnetic susceptibility imaging has been developed so far, and it has been applied in the research of various cranial nerve diseases such as cerebral hemorrhage, multiple sclerosis and Parkinson's syndrome. [0003] The reconstruction process of quantitative magnetic susceptibility imaging mainly includes three steps: field map fitting, background field removal and magnetic susceptibility inversion. An accurate field map can improve the image quality of the magnetic susceptibility distribution map, making the magnetic susceptibility ...

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Problems solved by technology

However, it does not mean that the more the number of echoes, the more accurate the field map fitting is, which is mainly limited by two aspects: one is that the echo signal strength is affected by T 2 Due to the influence of relaxation, the greater the number of echoes, the greater the signal intensity of the subsequent echoes, and sometimes even to the noise level; the second is due to noise, uneven magnetic susceptibility of some regions of interest (such as the skull base), and blood flow. , the fluctuation of the main magnetic field itself, and other factors, every time a phase map is obtained, it will be accompanied by errors. If the phase error is too large, it will affect the accuracy of field map fitting.

[0005] The general multi-echo magnetic field distribution map fitting method uses the same echo number for all data points, without checking the phase linearity of each data point, resulting in inaccurate fitting of the magnetic field distribution map, and the obtained magnetic susceptibility distribution map The noise in the skull base and other parts is large, resulting in a low signal-to-noise ratio of the final magnetic susceptibility distribution map, which does not have good tissue resolution, and cannot accurately measure the magnetic susceptibility values ​​of the skull base and other parts

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