title: Improved MR venography using quantitative susceptibility-weighted imaging.
abstract: OBJECTIVE
  To remove the geometry dependence of phase-based susceptibility weighting masks in susceptibility-weighted imaging (SWI) and to improve the visualization of the veins and microbleeds.
  
  
  METHODS
  True SWI (tSWI) was generated using susceptibility-based masks. Simulations were used to evaluate the influence of the characteristic parameters defining the mask. In vivo data from three healthy adult human volunteers were used to compare the contrast-to-noise-ratios (CNRs) of the right septal vein and the left internal cerebral vein as measured from both tSWI and SWI data. A traumatic brain injury (TBI) patient dataset was used to illustrate qualitatively the proper visualization of microbleeds using tSWI.
  
  
  RESULTS
  Compared with conventional SWI, tSWI improved the CNR of the two selected veins by a factor of greater than three for datasets with isotropic resolution and greater than 30% for datasets with anisotropic resolution. Veins with different orientations can be properly enhanced in tSWI. Furthermore, the blooming artifact due to the strong dipolar phase of microbleeds in conventional SWI was reduced in tSWI for the TBI case.
  
  
  CONCLUSIONS
  The use of tSWI overcomes the geometric limitations of using phase and provides better visualization of the venous system, especially for data collected with isotropic resolution.
authors.affiliation: School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Saifeng
authors.initials: S
authors.lastname: Liu
authors.forename: Karen
authors.initials: K
authors.lastname: Mok
authors.forename: Jaladhar
authors.initials: J
authors.lastname: Neelavalli
authors.forename: Yu-Chung N
authors.initials: YC
authors.lastname: Cheng
authors.forename: Jin
authors.initials: J
authors.lastname: Tang
authors.forename: Yongquan
authors.initials: Y
authors.lastname: Ye
authors.forename: E Mark
authors.initials: EM
authors.lastname: Haacke
mesh_terms: D000465:Algorithms; D064368:Healthy Volunteers; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography / Q000379:methods*; D019047:Phantoms, Imaging; D014680:Veins / Q000033:anatomy & histology*
keywords: phase imaging; quantitative susceptibility mapping; susceptibility-weighted imaging