Improved elimination of phase effects from background field inhomogeneities for susceptibility weighted imaging at high magnetic field strengths.
To enhance susceptibility-related contrast of magnetic resonance images, the phase of susceptibility weighted data needs to be corrected for background inhomogeneities and phase wraps caused by them. Current methods either use homodyne filtering or a combination of phase unwrapping and high pass filtering. The drawback of homodyne filtering is incomplete elimination of phase wraps in areas with steep phase topography produced by background inhomogeneities of the static magnetic field. The disadvantage of phase unwrapping is that it requires subsequent high pass filtering, which introduces artifacts in areas with very steep transitions, such as areas near interfaces between parenchyma and bone or air. A method is proposed that reduces the artifacts associated with high pass filtering without sacrificing the advantages of phase unwrapping. This technique is demonstrated with phantom data at 1.5 T and with human data at 1.5, 3 and 7 T.
UBC MRI Research Centre, University of British Columbia, Vancouver, Canada. rauscher@physics.ubc.ca
Alexander
A
Rauscher
Markus
M
Barth
Karl-Heinz
KH
Herrmann
Stephan
S
Witoszynskyj
Andreas
A
Deistung
Jüergen R
JR
Reichenbach
D000465:Algorithms; D016477:Artifacts; D002550:Cerebral Veins / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity