Magnetic resonance chemical-shift-encoded imaging method, apparatus and device

Patent metadata

Field	Value
Publication number	US-10459052-B2
Application number	US-201516067204-A
Country	US
Kind code	B2
Filing date	Dec 30, 2015
Priority date	Dec 30, 2015
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

Provided are a magnetic resonance chemical-shift-encoded imaging method, apparatus, and device, belonging to the technical field of magnetic resonance imaging. The method comprises: in a phasor-error plot established on the basis of a two-point magnetic resonance signal model, determining to be an initial seed point a pixel having a unique phasor and causing said plot to reach a minimal local value; according to the initial seed point, estimating the phasor value of a to-be-estimated pixel to obtain a field map; mapping and merging the field map at the highest resolution to obtain a reconstructed field map; determining a reconstructed seed point from the reconstructed field map, and estimating the reconstructed seed point to obtain the phasor value of the reconstructed to-be-estimated pixel; according to the reconstructed seed point and the phasor value of the reconstructed to-be-estimated pixel, obtaining two separate images having predetermined components. In the method, a region simultaneously containing two components is identified as a seed point, eliminating the deviation caused by phasor-value jump at high resolution and ensuring the correctness of the seed point ultimately selected.

First claim

What is claimed is:

1. A magnetic resonance chemical-shift-encoded imaging method, comprising:
providing predetermined resolutions;
establishing a phasor-error spectrum based on a two-point magnetic resonance signal model in a sampled image at each of the predetermined resolutions;
determining to be an initial seed point a pixel point having a unique phasor value in the phasor-error spectrum and enabling the phasor-error spectrum to reach a local minimum value;
estimating a phasor value of a to-be-estimated pixel point according to the initial seed point to obtain a field pattern at each of the predetermined resolutions;
mapping, at a highest resolution, the field patterns at the predetermined resolutions respectively to obtain a plurality of field patterns at the highest resolution, and merging the plurality of field patterns to obtain a reconstructed field pattern;
determining a reconstructed seed point from the reconstructed field pattern, and estimating based on the reconstructed seed point to obtain a phasor value of the reconstructed to-be-estimated pixel point; and
obtaining separated images of two predetermined components according to the phasor values of the reconstructed to-be-estimated pixel point and the reconstructed seed point.

2. The method according to claim 1 , wherein obtaining separated images of two predetermined components according to the phasor values of the reconstructed to-be-estimated pixel point and the reconstructed seed point comprises:
obtaining the separated images of the two predetermined components after smoothing the reconstructed field pattern.

3. A computer readable storage medium, comprising computer instructions, when the computer instructions are executed, executing the method of claim 1 .

4. The method according to claim 1 , wherein determining to be the initial seed point the pixel point having a unique phasor value and enabling the phasor-error spectrum to reach the local minimum value comprises:
obtaining a phasor-error spectrum of each pixel point in the image in the predetermined resolution, and determining, according to the phasor-error spectrum, the phasor value that enables the pixel point to reach the local minimum value; and
determining the pixel point to be the initial seed point if the pixel point has a signal-to-noise ratio greater than the predetermined value and has a unique phasor value.

5. The method according to claim 4 , wherein determining the pixel point having the unique phasor value comprises:
determining, if the pixel point has only one local minimum value enabling the fitting error to be less than a predetermined value, the local minimum value to be the unique phasor value of the pixel point.

6. The method according to claim 4 , wherein the phasor-error spectrum is determined through the following formula:
d =arg min err( d )=arg minΣ(1− AA + )∘( SS T )

S =[Re( Ŝ 1 );Re( Ŝ 2 );Im( Ŝ 1 );Im( Ŝ 2 )],

wherein d indicates the phasor-error spectrum; I indicates 4×4 matrix; superscript ‘+’ indicates to take matrix pseudo-inverse, A + =(A T A) −1 A T ; a connector “∘” indicates a dot product; err(d) describes a relationship between phasor d and the fitting error; and ŝ 1 and ŝ 2 indicate predetermined row vectors.

7. The method according to claim 5 , wherein estimating the phasor value of the to-be-estimated pixel point according to the initial seed point comprises:
determining, if the to-be-estimated pixel point comprises a plurality of local minimum values, the local minimum values having the fitting errors less than the predetermined value to be a plurality of phasor values of the to-be-estimated pixel point; and
selecting, from the plurality of phasor values of the to-be-estimated pixel point, the phasor value having the maximum similarity with the phasor values of adjacent seed points to be the phasor value of the to-be-estimated pixel point.

8. The method according to claim 7 , wherein a maximum similarity between a plurality of phasor values of the to-be-estimated pixel point and phasor values of adjacent seed points is determined through the following formula:
d =arg max{ D 1 ,D 2 , . . . ,D S }

wherein D 1 , D 2 . . . D s indicate the similarity of phasor and are determined through the following formula:

D
s

=

∑

k
=
1

K

⁢

m
k

⁢

cos
⁡

(

angle
⁡

(

d
s

*

conj
⁡

(

d
k

)

)

)

∑

k
=
1

K

⁢

m
k

wherein K indicates the quantity of seed points in eight neighborhoods of the current to-be-estimated pixel point; m k indicates the amplitude of the k-th seed point; the corresponding phasor value is d k , which indicates a phasor candidate value of the current to-be-estimated pixel point; conj(.) indicates to take complex conjugate; and angle(.) indicates to take an angle.

9. The method according to claim 8 , wherein estimating the phasor value of the to-be-estimated pixel point according to the initial seed point further comprises:
selecting the to-be-estimated pixel point having an amplitude greater than a first threshold to establish a first to-be-estimated pixel point set;
obtaining a phase difference between each two of adjacent seed points of each to-be-estimated pixel point in the first to-be-estimated pixel point set, and selecting the to-be-estimated pixel point having a maximum phase difference less than a second threshold to establish a second to-be-estimated pixel point set;
arranging to-be-estimated pixel points in the second to-be-estimated pixel point set in a descending order based on the quantity of the adjacent seed points, and selecting a predetermined quantity of to-be-estimated pixel points to establish a third to-be-estimated pixel point set;
obtaining the maximum phase similarity between the to-be-estimated pixel po

Assignees

• Shenzhen Inst Of Adv Tech Cas

Inventors

• Zheng Hairong
• Liu Xin
• Cheng Chuanli
• Zou Chao

Classifications

• G01R33/5608

  Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T) · CPC title

• G01R33/4625

  Processing of acquired signals, e.g. elimination of phase errors, baseline fitting, chemometric analysis · CPC title

• G01R33/4828 Primary

  Resolving the MR signals of different chemical species, e.g. water-fat imaging · CPC title

• G01R33/443

  Assessment of an electric or a magnetic field, e.g. spatial mapping, determination of a B0 drift or dosimetry · CPC title

• G01R33/56

  Image enhancement or correction, e.g. subtraction or averaging techniques {, e.g. improvement of signal-to-noise ratio and resolution} · CPC title