title: Susceptibility mapping as a means to visualize veins and quantify oxygen saturation.
abstract: OBJECTIVE
  To create an orientation-independent, 3D reconstruction of the veins in the brain using susceptibility mapping.
  
  
  METHODS
  High-resolution, high-pass filtered phase images usually used for susceptibility weighted imaging (SWI) were used as a source for local magnetic field behavior. These images were subsequently postprocessed using an inverse procedure to generate susceptibility maps of the veins. Regularization and interpolation of the data in k-space of the phase images were used to reduce reconstruction artifacts. To understand the effects of artifacts, and to fine-tune the methodology, simulations of blood vessels were performed with and without noise.
  
  
  RESULTS
  With sufficient resolution, major veins in the brain could be visualized with this approach. The usual geometry-dependent phase dipole effects are removed by this processing, leaving basically images of the veins. Different sized vessels show a different level of contrast depending on their partial volume effects. Vessels that are 8 mm or 16 mm in size show quantitative values expected for normal oxygen saturation levels. Smaller vessels show smaller values due to errors in the methodology and due to partial volume effects. Larger vessels show a bias toward a reduced susceptibility approaching 90% of the expected value. Limitations of the method and artifacts related to different sources of errors are demonstrated.
  
  
  CONCLUSIONS
  Susceptibility maps can successfully create venograms of the brain with varying levels of contrast-to-noise depending on the size of the vessel. Partial volume effects render this approach more useful as an imaging tool or a visualization tool, although certain larger vessels have measured susceptibilities close to expected values associated with normal blood oxygen saturation levels.
authors.affiliation: Department of Radiology, Wayne State University, Detroit, Michigan 48201, USA. nmrimaging@aol.com
authors.forename: E M
authors.initials: EM
authors.lastname: Haacke
authors.forename: J
authors.initials: J
authors.lastname: Tang
authors.forename: J
authors.initials: J
authors.lastname: Neelavalli
authors.forename: Y C N
authors.initials: YC
authors.lastname: Cheng
mesh_terms: D000465:Algorithms; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008962:Models, Theoretical; D010092:Oximetry; D010101:Oxygen Consumption / Q000502:physiology; D014680:Veins / Q000502:physiology*
references.citation: Hum Brain Mapp. 1997;5(5):341-6
references.pmid: 20408238
references.citation: J Magn Reson Imaging. 2009 Jan;29(1):177-82
references.pmid: 19097156
references.citation: Neuroimage. 2009 Feb 15;44(4):1259-66
references.pmid: 19027861
references.citation: Phys Med Biol. 2006 Dec 21;51(24):6381-402
references.pmid: 17148824
references.citation: Radiology. 1997 Jul;204(1):272-7
references.pmid: 9205259
references.citation: Magn Reson Med. 2009 Aug;62(2):333-40
references.pmid: 19526517
references.citation: Phys Med Biol. 2009 Mar 7;54(5):1169-89
references.pmid: 19182322
references.citation: IEEE Trans Med Imaging. 2010 Feb;29(2):273-81
references.pmid: 19502123
references.citation: J Magn Reson Imaging. 2008 Sep;28(3):727-35
references.pmid: 18777533
references.citation: J Magn Reson Imaging. 2009 Apr;29(4):937-48
references.pmid: 19306433
references.citation: Magn Reson Imaging Clin N Am. 2009 Feb;17(1):47-61
references.pmid: 19364599
references.citation: Magn Reson Med. 2004 Sep;52(3):612-8
references.pmid: 15334582
references.citation: Magn Reson Med. 2009 Jan;61(1):196-204
references.pmid: 19097205
references.citation: Magn Reson Imaging. 2006 Feb;24(2):155-60
references.pmid: 16455403
references.citation: Med Phys. 2009 Dec;36(12):5429-36
references.pmid: 20095255