title: Noncontrast peripheral MRA with spiral echo train imaging.
abstract: OBJECTIVE
  To develop a spin echo train sequence with spiral readout gradients with improved artery-vein contrast for noncontrast angiography.
  
  
  BACKGROUND
  Venous T2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times.
  
  
  METHODS
  Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution.
  
  
  RESULTS
  In vivo, artery-vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery-vein contrast, better spatial resolution (1.2 mm(2) versus 1.5 mm(2) ), and was acquired in less time (1.4 min versus 7.5 min).
  
  
  CONCLUSIONS
  The spiral spin echo train sequence can be used for flow-independent angiography to generate three-dimensional angiograms of the periphery quickly and without the use of contrast agents.
authors.affiliation: Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Fielden
authors.forename: John P
authors.initials: JP
authors.lastname: Mugler
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Hagspiel
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Norton
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kramer
authors.forename: Craig H
authors.initials: CH
authors.lastname: Meyer
mesh_terms: D000328:Adult; D000465:Algorithms; D001158:Arteries / Q000033:anatomy & histology*; D001185:Artificial Intelligence; D003287:Contrast Media; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D014680:Veins / Q000033:anatomy & histology*
chemical_list: D003287:Contrast Media
keywords: flow-independent angiography; noncontrast angiography; peripheral angiography
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