Correction method for B0 field pattern of magnetic resonance system

Abstract

The invention provides a correction method for a B0 field pattern of a magnetic resonance system, and the method comprises the steps: firstly obtaining a three-dimensional B0 field pattern of the magnetic resonance system, and dividing the three-dimensional B0 field pattern into a plurality of layers along each dimension; performing 2D phase unwrapping layer by layer along at least two dimensions of the three-dimensional B0 field pattern to obtain a middle B0 field pattern; and finally, selecting one of the at least two dimensions as a reference direction, obtaining the phase difference between two adjacent layers in the B0 field pattern in the reference direction, and the phase difference meeting a global optimization rule. According to the method, 3D phase unrolling calculation is performed on the basis of a result obtained by performing 2D unrolling on each layer of a 3D phase one by one, and a global optimization rule is introduced, so that a shimming result has excellent stability and accuracy; moreover, the method disclosed by the invention is high in calculation efficiency, better meets the quick response requirement in practical application, and has a better clinical application prospect.

Description

technical field [0001] The invention relates to a method for correcting a B0 field map, in which a 3D phase unwinding method is applied; it belongs to the technical field of magnetic resonance imaging. Background technique [0002] In the magnetic resonance imaging system, the magnet itself can provide a relatively uniform static magnetic field B0 in a certain space, and the uniformity of the magnetic field is a key factor for the quality of the magnetic resonance image. However, due to the difference in tissue magnetic susceptibility, local magnetic field changes (ie, inhomogeneity) will occur at the junction, resulting in susceptibility artifacts, poor fat-pressing effects, and image distortion. Therefore, in order to improve the quality of the image, it is necessary to reduce the non-uniformity of the magnetic field (that is, shimming), so that it becomes a spatially continuous distribution, and the color does not jump to become a uniform image. In the prior art, a two-d...

AI Technical Summary

Problems solved by technology

In the path-guided method, an evaluation function for the quality of the phase image is first selected. The full winding starts from a point in the 3D data, calculates the evaluation function along all directions, selects the direction with the highest evaluation value, and then performs a one-dimensional calculation along this direction. Phase dewrapping, the accuracy of this method depends on the selection of the quality function of the phase map, if the selection of the quality map is unreasonable, it will lead to inaccurate calculation results of the algorithm

However, the path-guided method lacks the global calculation of the phase map. When a certain path is wrong, it may cause calculation errors for subsequent pixels on the path, and it also lacks practical application value.

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