Method for magnetic resonance imaging

Patent metadata

Field	Value
Publication number	US-10114100-B2
Application number	US-201615150915-A
Country	US
Kind code	B2
Filing date	May 10, 2016
Priority date	May 13, 2015
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

The present invention relates to a method for Magnetic Resonance Imaging to depict an object by an image having pixels representing volume element of the object. The method comprises: Immobilizing the object and acquiring a reference image at a first echo time immediately following an excitation, wherein said reference image is complex-valued, with a reference magnitude value and a reference phase value for each pixel; acquiring a target image of the object with said receiver coil at a pre-selected second echo time, wherein said target image is complex-valued, with a target magnitude value and a target phase value for each pixel; subtracting, pixel by pixel, the reference phase value from the target phase value to obtain a corrected phase value for each pixel; and obtaining said image from said target magnitude values and said corrected phase values.

First claim

What is claimed is:

1. A method for Magnetic Resonance Imaging to depict a 3-dimensional object by an image having pixels representing volume elements of the object, comprising:
immobilising the object and acquiring a reference image of the object with a receiver coil at a first echo time immediately following an excitation by a transmitter coil, wherein said reference image is complex-valued, representing each volume element by a pixel with a reference magnitude value and a reference phase value;
keeping the object immobilised and acquiring a target image of the object with said receiver coil at a pre-selected second echo time, longer than said first echo time, following the same or another excitation by said transmitter coil, wherein said target image is complex-valued, representing each volume element by a pixel with a target magnitude value and a target phase value;
subtracting, pixel by pixel, the reference phase value from the target phase value to obtain a corrected phase value for each pixel; and
obtaining said image from said target magnitude values and said corrected phase values, wherein the method is applied to each of a plurality of receiver coils arranged around said immobilised object to obtain a respective plurality of said images, followed by the step of calculating a combined phase image, pixel by pixel, according to

ϑ
S

=

∠
(

∑
p

⁢

⁢

m

T
,
p

·

e

-

i
⁡

(

ϑ

T
,
p

-

ϑ

R
,
p

)

)

with
<(⋅) denoting the four-quadrant tangent inverse operator,
m T,p being the target magnitude value of a pixel, representing a volume element of the object, in a target image acquired with the p th receiver coil,
ϑ T,p being the target phase value of said pixel,
ϑ R,p being the reference phase value of a pixel, representing said volume element, in a reference image acquired with the p th receiver coil, and
ϑ S being the phase value of a pixel, representing said volume element, in the combined phase image.

2. The method of claim 1 , wherein said first echo time is less than 1 ms.

3. The method of claim 1 , wherein said first echo time is less than 100 μs.

4. The method of claim 1 , wherein the reference image is acquired at a lower pixel resolution than the target image and, prior to said subtracting, is upscaled to the pixel resolution of the target image.

5. The method of claim 1 , wherein the respective reference or target images acquired with said plurality of receiver coils are all acquired following one and the same excitation.

6. The method of claim 1 , wherein the method is applied to each of a plurality of receiver coils arranged around said immobilised object to obtain a respective plurality of said images, followed by the step of calculating a combined magnitude image, pixel by pixel, according to

m
S

=



∑
p

⁢

⁢

m

T
,
p

·

e

-

i
⁡

(

ϑ

T
,
p

-

ϑ

R
,
p

)



with
|⋅| denoting the magnitude operator,
m T,p being the target magnitude value of a pixel, representing a volume element of the object, in a target image acquired with the p th receiver coil,
ϑ T,p being the target phase value of said pixel,
ϑ R,p being the reference phase value of a pixel, representing said volume element, in a reference image acquired with the p th receiver coil, and
m S being the magnitude value of a pixel, representing said volume element, in the combined magnitude image.

7. The method of claim 1 , wherein the method is applied to each of a plurality of receiver coils arranged around said immobilised object to obtain a respective plurality of said images, followed by the step of calculating a combined magnitude image, pixel by pixel, according to

m
W

=



∑
p

⁢

⁢

m

T
,
p

2

·

Assignees

• Univ Wien Med

Inventors

• Robinson Simon Daniel

Classifications

• G01R33/56536

  due to magnetic susceptibility variations · CPC title

• 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

• G01R33/56563

  caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title

• G01R33/56545 Primary

  caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts · CPC title

• G01R33/3415

  comprising arrays of sub-coils {, i.e. phased-array coils with flexible receiver channels} · CPC title