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Correcting method of magnetic resonance image distortion under strong nonuniform magnetic field

A magnetic resonance image and uniform magnetic field technology, applied in the direction of measuring magnetic variables, measuring devices, instruments, etc., can solve the problems of reconstructed image residual artifacts, loss of detail signals, etc.

Inactive Publication Date: 2016-07-06
XIAMEN UNIV
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Problems solved by technology

However, while he simplifies and accelerates the algorithm by modulating the discrete resolution level, he also loses many detail signals, resulting in serious artifacts in the reconstructed image.

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  • Correcting method of magnetic resonance image distortion under strong nonuniform magnetic field
  • Correcting method of magnetic resonance image distortion under strong nonuniform magnetic field
  • Correcting method of magnetic resonance image distortion under strong nonuniform magnetic field

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Embodiment Construction

[0037] The present invention comprises the following steps:

[0038] 1) Calculate the evolution time of the inhomogeneous field: t(k x ,k y ) means that the k-space sampling position is (k x ,k y ) inhomogeneous field evolution time, expressed as

[0039]

[0040] where t c is the time difference between applying the RF pulse and before data sampling, t in the EPI sequence c The value is small and can be ignored. k x ,k y is an orthogonal discrete coordinate variable of the k-space Cartesian system. The two orthogonal coordinate directions of the k-space are respectively called the row coordinate axis direction (k x direction) and column axis direction (k y direction). Correspondingly, x and y are two orthogonal discrete coordinate variables in the image space, and the two orthogonal directions in the image space are also called the phase encoding direction (y coordinate axis direction) and the frequency encoding direction (x coordinate axis direction) . n(k y...

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Abstract

A correcting method of magnetic resonance image distortion under a strong nonuniform magnetic field relates to a magnetic resonance image. The method is characterized in that: at the aspect of model, a nonuniform field is described into the format of a four-dimensional matrix completely by the two-dimensional Fourier orthogonal transformation, and then the four-dimensional matrix is transformed into a two-dimensional large-scale matrix in a dimensionality reduction manner; at the aspect of method, iteration is mainly carried out on two modules, on one hand, the nonuniform field is given, and an l1 norm optimization model based on orthogonal base change and the compressed sensing is established and solved, on the other hand, a magnetic moment density distribution image is given, and the nonuniform field is fitted by an unwrapping algorithm and a cuckoo optimization search algorithm. According to the present invention, the magnetic resonance fast sequence imaging distortion under the strong nonuniform magnetic field and a local nonuniform magnetic field is corrected remarkably, the sensitivity of a magnetic resonance imaging fast sequence to the strong nonuniform magnetic field is overcome, and the image distortion caused by the nonuniform field is corrected.

Description

technical field [0001] The invention relates to a magnetic resonance image, in particular to a method for correcting distortion of a magnetic resonance image under a strong inhomogeneous magnetic field. Background technique [0002] Magnetic resonance imaging has good clinical safety and is widely used in medical diagnosis. The space of data collected by magnetic resonance is called k-space, and the space of magnetic resonance images is called image space. The spin echo EPI sequence is a fast sequence, which can collect the entire k-space data only by exciting one RF pulse, which can effectively overcome the shortcoming of the slow speed of magnetic resonance imaging. The traditional MRI image reconstruction method is to perform Fourier transformation on the acquired two-dimensional data. However, EPI imaging is sensitive to inhomogeneous fields, and the images reconstructed by Fourier transform usually have distortions in the inhomogeneous field regions. [0003] Zibetti...

Claims

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Application Information

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IPC IPC(8): G01R33/565
CPCG01R33/565
Inventor 陈忠庄孝星蔡聪波
Owner XIAMEN UNIV
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