title: Reduction of artifacts in susceptibility-weighted MR venography of the brain.
abstract: OBJECTIVE
  To reduce the off-resonance artifact in susceptibility-weighted imaging (SWI)-based MR venography (MRV) in the brain regions with severe field inhomogeneity and to reduce the signal loss in the minimum-intensity projection (mIP) display of the 3D MRV.
  
  
  METHODS
  A novel postprocessing approach was presented to map the local field gradients (LFGs) using the 3D SWI data without phase-unwrapping. LFG measurements were used to assess the severity of field inhomogeneity and suppress the residual phase in the phase mask induced by the off-resonance effect. Volume segmentation of brain tissue was used to reduce the signal loss in the peripheral regions of the brain in the through-plane mIP images and enable in-plane mIP display of MRV.
  
  
  RESULTS
  Off-resonance artifact in the brain regions with severe field inhomogeneity was effectively reduced by the LFG-based phase suppression approach. Signal loss was reduced in the through-plane mIP of MRV using volume segmentation of brain tissue prior to projection. In-plane mIP of MRV also became feasible with volume segmentation.
  
  
  CONCLUSIONS
  Off-resonance artifacts and signal loss in mIP display of MRV can be effectively reduced through postprocessing.
authors.affiliation: Department of Biomedical Engineering, Zhejiang University, Hangzhou, China.
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Jin
authors.forename: Ling
authors.initials: L
authors.lastname: Xia
authors.forename: Yiping P
authors.initials: YP
authors.lastname: Du
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods; D002560:Cerebrovascular Circulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography / Q000379:methods*