An MRI Inhomogeneous Field Estimation Method Based on Image Gradient Fitting

A non-uniform field and image gradient technology, applied in image enhancement, image analysis, image data processing, etc., can solve problems such as inability to guarantee alignment, large fitting errors, and inability to extract fitting points, avoiding errors and eliminating errors. , the effect of improving the estimation accuracy

Active Publication Date: 2017-06-27
UNIV OF SCI & TECH OF CHINA
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Problems solved by technology

The disadvantage is that the alignment cannot be guaranteed between rows. For some rows, when the high-frequency characteristics account for the majority, it is impossible to extract enough fitting points, resulting in excessive fitting errors.

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  • An MRI Inhomogeneous Field Estimation Method Based on Image Gradient Fitting
  • An MRI Inhomogeneous Field Estimation Method Based on Image Gradient Fitting
  • An MRI Inhomogeneous Field Estimation Method Based on Image Gradient Fitting

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Embodiment Construction

[0048] Step 1, denoising processing

[0049] The original NMR image is obtained by Fourier transform of the collected k-space signal. Noise due to equipment and environment. The present invention is gradient-based non-uniform field estimation, and the gradient is very sensitive to noise. Before the estimation, the original image should be denoised. The preprocessing also includes the contour extraction of the image, removing the background area of ​​the edge and some low signal-to-noise ratio areas.

[0050] Step 2. Calculate the gradient field

[0051] Estimating an inhomogeneous field requires a fitting operation on the gradient values ​​in the region. Therefore, the gradient field of the image is first calculated, including the x-direction gradient and the y-direction gradient. The image gradient is generally obtained by difference method or sobel operator. In order to reduce noise interference, the present invention proposes a new gradient operator based on Gaussian ke...

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Abstract

The invention provides an MRI (Magnetic Resonance Imaging) non-uniform field estimation method based on image gradient fitting. The method comprises the following steps: processing an image in a log-domain and decoupling a real image signal and a non-uniform field signal; obtaining the estimation of a non-uniform field through fitting a gradient in an organization region with more uniform grayscale in the image. As gradient processing is performed in the log-domain, a gradient value obtained by a certain pixel is not related to a pixel organization type but is related to the non-uniform field; a special objective function is designed during fitting, so that the estimation of the non-uniform field can be directly obtained through first-order derivatives of the image in an x direction and a y direction without integrating or calculating a second order gradient again.

Description

technical field [0001] Quickly estimate and correct for inhomogeneous fields in MRI images due to magnetic inhomogeneity or coil sensitivity. 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 receivi...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06T5/00G06T7/60A61B5/055
Inventor 凌强李朝辉李峰
Owner UNIV OF SCI & TECH OF CHINA
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