MRI (Magnetic resonance imaging) nonuniform field estimation method based on line-by-line gradient fitting

A non-uniform field and gradient field technology, applied in the field of MRI non-uniform field estimation based on line-by-line gradient fitting, can solve problems such as image information loss, and achieve the effect of low complexity, low time consumption and easy implementation.

Active Publication Date: 2015-03-04
UNIV OF SCI & TECH OF CHINA
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Problems solved by technology

However, the disadvantage of the method is that the non-uniform field spectrum and the image spectrum are aliased, so that the corrected image information is lost

Method used

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  • MRI (Magnetic resonance imaging) nonuniform field estimation method based on line-by-line gradient fitting
  • MRI (Magnetic resonance imaging) nonuniform field estimation method based on line-by-line gradient fitting
  • MRI (Magnetic resonance imaging) nonuniform field estimation method based on line-by-line gradient fitting

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Embodiment Construction

[0038] according to figure 1 Algorithm flow chart, the specific steps are as follows:

[0039] Step 1. Preprocessing

[0040]The original NMR image is obtained by Fourier transform of the collected k-space signal. Subject to noise due to equipment and environmental influences. The original image is first denoised before estimation to prevent the influence of noise on the gradient calculation. Secondly, extract the outline of the image, remove the background area of ​​the edge and some areas with low signal-to-noise ratio; in addition, determine the outline of the image to exclude the influence of the gradient value of the noise in the background part of the image on the reconstruction. Contours can be demarcated by thresholding the histogram of the image.

[0041] Step 2. Calculate the gradient field

[0042] Estimating an inhomogeneous field requires a fitting operation on the gradient values ​​in the region. In order to decouple the non-uniform field and the real image...

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Abstract

The invention provides an MRI nonuniform field estimation method based on line-by-line gradient fitting. According to the method, nonuniform field is supposed to be smooth and slowly changed, so that grey change caused by the nonuniform field can be small, and gradient values reflected in a gradient image can also be small. Large gradient values represent detail information in the image. By extracting the large gradient values in the image line by line to reconstruct the image, the influence of the nonuniform field is eliminated. By fitting errors of an original image and the reconstructed image, the estimation of the nonuniform field is obtained. During fitting, the method simultaneously performs primary fitting on the x-direction gradient and the y-direction gradient, so that the fitting precision can be improved.

Description

technical field [0001] Estimate and correct the inhomogeneous field caused by the inhomogeneous magnetic field and coil sensitivity in the MRI image. Background technique [0002] Magnetic resonance imaging is widely used in medical diagnosis and scientific research because of its high resolution, no ionizing radiation damage, and imaging at any angle. However, due to the interference of magnetic field inhomogeneity and coil sensitivity, etc., the reconstructed image of the MRI system shows certain inhomogeneity, which will produce certain images for doctor diagnosis and computer-aided analysis such as registration and classification. With the demand for higher-resolution scanning images, the magnetic field strength of the scanner is getting higher and higher, and the magnetic field gradient is getting finer. It's getting serious. The inhomogeneous field is the deviation field caused by the inhomogeneity of the transmitted spatial magnetic field or the inhomogeneity of the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T11/00
Inventor 凌强李朝辉李峰
Owner UNIV OF SCI & TECH OF CHINA
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