title: Automated unwrapping of MR phase images applied to BOLD MR-venography at 3 Tesla.
abstract: OBJECTIVE
  To improve the diagnostic value of BOLD MR-Venography by removing artifacts related to phase wrapping, particularly in regions of large background susceptibilities at high magnetic field strengths.
  
  
  METHODS
  High resolution, T(2)(*)-weighted, single echo images were acquired on a 3 T system (Medspec 30/80 Avance, Bruker Medical, Ettlingen, Germany) with a three-dimensional, first order velocity compensated gradient echo sequence using a quadrature transmit/receive birdcage head coil. Data of nine healthy subjects and 19 patients were evaluated (age range: 27 to 76 years). To achieve improved MR-venograms, a fully automated region-growing phase unwrapping algorithm and subsequent high pass filtering were applied to phase images prior to the computation of minimum intensity projections.
  
  
  RESULTS
  Considerably improved visualization of venous structures in regions of large background susceptibility-induced field inhomogeneities is demonstrated in healthy subjects and patients with brain tumors.
  
  
  CONCLUSIONS
  BOLD MR venograms are improved compared to previous post-processing algorithms. It is now feasible to obtain high-resolution images also in inhomogeneous regions, which increases the clinical potential of BOLD MR-Venography.
authors.affiliation: NMR Group, Institute of Medical Physics, University of Vienna, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Rauscher
authors.forename: Markus
authors.initials: M
authors.lastname: Barth
authors.forename: Jürgen R
authors.initials: JR
authors.lastname: Reichenbach
authors.forename: Rudolf
authors.initials: R
authors.lastname: Stollberger
authors.forename: Ewald
authors.initials: E
authors.lastname: Moser
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D001932:Brain Neoplasms / Q000175:diagnosis*; D002550:Cerebral Veins / Q000033:anatomy & histology* / Q000473:pathology*; D005910:Glioma / Q000175:diagnosis*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008280:Magnetics; D008875:Middle Aged; D010690:Phlebography / Q000379:methods; D012016:Reference Values