title: Vascular masking for improved unfolding in 2D SENSE-accelerated 3D contrast-enhanced MR angiography.
abstract: OBJECTIVE
  To describe and evaluate the method we refer to as "vascular masking" for improving signal-to-noise ratio (SNR) retention in sensitivity encoding (SENSE)-accelerated contrast-enhanced magnetic resonance angiography (CE-MRA).
  
  
  METHODS
  Vascular masking is a technique that restricts the SENSE unfolding of an accelerated subtraction angiogram to the voxels within the field of view known to have enhancing signal. This is a more restricted voxel set than that identified with conventional masking, which excludes only voxels in the air around the object. Thus, improved retention of SNR is expected. Evaluation was done in phantom and in vivo studies by comparing SNR and the g-factor in results reconstructed using vascular versus conventional masking. A radiological evaluation was also performed comparing conventional and vascular masking in R = 8 accelerated CE-MRA studies of the thighs (n = 21) and calves (n = 13).
  
  
  RESULTS
  Images reconstructed with vascular masking showed a significant reduction in g-factor and improved retention of SNR versus those reconstructed with conventional masking. In the radiological evaluation, vascular masking consistently provided reduced background noise, improved luminal signal smoothness, and better small vessel conspicuity.
  
  
  CONCLUSIONS
  Vascular masking provides improved SNR retention and improved depiction of the vasculature in accelerated, subtraction 3D CE-MRA of the thighs and calves.
authors.affiliation: Mayo Clinic, MR Laboratory, Rochester, Minnesota, USA.
authors.forename: Eric G
authors.initials: EG
authors.lastname: Stinson
authors.forename: Eric A
authors.initials: EA
authors.lastname: Borisch
authors.forename: Casey P
authors.initials: CP
authors.lastname: Johnson
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Trzasko
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Young
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Riederer
mesh_terms: D000465:Algorithms; D003287:Contrast Media; D005260:Female; D005263:Femoral Artery / Q000033:anatomy & histology*; D005682:Gadolinium; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D016909:Tibial Arteries / Q000033:anatomy & histology*
chemical_list: D003287:Contrast Media; D005682:Gadolinium
keywords: SENSE; contrast-enhanced MR angiography (CE-MRA); masking
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