title: Spoiling without additional gradients: Radial FLASH MRI with randomized radiofrequency phases.
abstract: OBJECTIVE
  To develop a method for spoiling transverse magnetizations without additional gradients to minimize repetition times for radial fast low angle shot (FLASH) MRI.
  
  
  METHODS
  Residual steady state transverse magnetizations and corresponding image artifacts were analyzed for radial gradient echo sequences with constant and randomized RF phases in comparison with a sequence with refocused frequency-encoding gradients, constant spoiler gradient, and conventional RF spoiling (gold standard). The spoiling performance was assessed for different radial trajectories using numerical simulations, phantom experiments, and in vivo MRI studies of the human brain.
  
  
  RESULTS
  Simulations as well as phantom and in vivo measurements reveal a highly efficient spoiling capacity for randomized RF phases and radial FLASH sequences without the need for gradient rewinding and spoiler gradients. The data also demonstrate a strong dependence of the spoiling performance on the chosen radial trajectory (ie, the azimuthal angular increment between successive projections) with excellent results for an interleaved multiturn scheme.
  
  
  CONCLUSIONS
  Effective spoiling of transverse magnetizations in radial FLASH MRI may be achieved by randomized RF phases without additional spoiler gradients. The technique allows for short repetition times as required for high-speed real-time MRI.
authors.affiliation: Biomedizinische NMR Forschungs GmbH at the Max Planck Institute for Biophysical Chemistry, Goettingen, Germany.
authors.forename: Volkert
authors.initials: V
authors.lastname: Roeloffs
authors.affiliation: Biomedizinische NMR Forschungs GmbH at the Max Planck Institute for Biophysical Chemistry, Goettingen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Voit
authors.affiliation: Biomedizinische NMR Forschungs GmbH at the Max Planck Institute for Biophysical Chemistry, Goettingen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Frahm
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D025341:Principal Component Analysis; D011846:Radio Waves
keywords: Golden Angle; RF spoiling; gradient spoiling; radial MRI; real-time MRI