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1. US20150362575 - Apparatus and method for correcting susceptibility artefacts in a magnetic resonance image

Office
United States of America
Application Number 14764094
Application Date 31.01.2014
Publication Number 20150362575
Publication Date 17.12.2015
Grant Number 09702955
Grant Date 11.07.2017
Publication Kind B2
IPC
G06K 9/00
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
9Methods or arrangements for reading or recognising printed or written characters or for recognising patterns, e.g. fingerprints
G01R 33/565
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques
565Correction of image distortions, e.g. due to magnetic field inhomogeneities
G01R 33/56
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques
G01R 33/561
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques
561by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
G06T 5/00
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
5Image enhancement or restoration
G06T 7/00
GPHYSICS
06COMPUTING; CALCULATING OR COUNTING
TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
7Image analysis
CPC
G01R 33/565
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance [NMR]
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences ; , Generation or control of pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques ; , e.g. improvement of signal-to-noise ratio and resolution
565Correction of image distortions, e.g. due to magnetic field inhomogeneities
G01R 33/24
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
24for measuring direction or magnitude of magnetic fields or magnetic flux
G01R 33/5608
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance [NMR]
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences ; , Generation or control of pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques ; , e.g. improvement of signal-to-noise ratio and resolution
5608Data 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
G01R 33/5616
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance [NMR]
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences ; , Generation or control of pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques ; , e.g. improvement of signal-to-noise ratio and resolution
561by reduction of the scanning time, i.e. fast acquiring systems, e.g. using echo-planar pulse sequences
5615Echo train techniques involving acquiring plural, differently encoded, echo signals after one RF excitation, e.g. using gradient refocusing in echo planar imaging [EPI], RF refocusing in rapid acquisition with relaxation enhancement [RARE] or using both RF and gradient refocusing in gradient and spin echo imaging [GRASE]
5616using gradient refocusing, e.g. EPI
G01R 33/56536
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance [NMR]
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences ; , Generation or control of pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques ; , e.g. improvement of signal-to-noise ratio and resolution
565Correction of image distortions, e.g. due to magnetic field inhomogeneities
56536due to magnetic susceptibility variations
G01R 33/56545
GPHYSICS
01MEASURING; TESTING
RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
33Arrangements or instruments for measuring magnetic variables
20involving magnetic resonance
44using nuclear magnetic resonance [NMR]
48NMR imaging systems
54Signal processing systems, e.g. using pulse sequences ; , Generation or control of pulse sequences
56Image enhancement or correction, e.g. subtraction or averaging techniques ; , e.g. improvement of signal-to-noise ratio and resolution
565Correction of image distortions, e.g. due to magnetic field inhomogeneities
56545caused by finite or discrete sampling, e.g. Gibbs ringing, truncation artefacts, phase aliasing artefacts
Applicants UCL Business PLC
Inventors Sebastien Ourselin
Pankaj Daga
Agents Park, Vaughan, Fleming & Dowler LLP
Priority Data 1301795.9 01.02.2013 GB
Title
(EN) Apparatus and method for correcting susceptibility artefacts in a magnetic resonance image
Abstract
(EN)

An apparatus and method are provided for performing phase unwrapping for an acquired magnetic resonance (MR) image. The method includes modelling the MR phase in the MR image using a Markov random field (MRF) in which the true phase φ(t) and the wrapped phase φ(w) are modelled as random variables such that at voxel i of said MR image φ(t)(i)=φ(w)(i)+2πn(i), where n(i) is an unknown integer that needs to be estimated for each voxel i. The method further includes constructing a graph consisting of a set of vertices V and edges E and two special terminal vertices representing a source s and sink t, where there is a one-to-one correspondence between cuts on the graph and configurations of the MRF, a cut representing a partition of the vertices V into disjoint sets S and T such that sεS and tεT. The method further includes finding the minimum energy configuration, E(n(i)|φ(w)) of the MRF on the basis that the total cost of a given cut represents the energy of the corresponding MRF configuration, where the cost of a cut is the sum of all edges going from S to T across the cut boundary. The method further includes using the values of n(i) in the minimum energy configuration to perform the phase unwrapping from φ(w) to φ(t) for the MR image. A confidence may be computed for each voxel using dynamic graph cuts. The unwrapped phase from two MR images acquired at different times may be used to estimate a field map from the phase difference between the two MR images. The field map may be converted into a deformation field which is then used to initialize a non-rigid image registration of the acquired MR image against a reference image. The deformation field of the non-rigid registration is controlled to be smoother where the confidence is high.


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