title: Accelerated human cardiac diffusion tensor imaging using simultaneous multislice imaging.
abstract: OBJECTIVE
  To demonstrate the feasibility of accelerating measurements of cardiac fiber structure using simultaneous multislice (SMS) imaging.
  
  
  METHODS
  SMS excitation with a blipped controlled aliasing (CAIPI) readout was incorporated into a diffusion-encoded stimulated echo pulse sequence to obtain diffusion measurements in three separate slices of the heart (8-mm thickness, 12-mm gap). A novel image entropy-based method for removing image ghosts in blipped CAIPI acquisitions is also introduced that enables SMS imaging of closely spaced slices in the heart.
  
  
  RESULTS
  The average retained signal-to-noise ratio (SNR) using this acquisition scheme is 70% ± 5%, higher than the standard 1/3 = 57% SNR penalty with three-fold acceleration. No significant difference was observed in the apparent diffusion coefficient and helix angle diffusion parameters between a time-equivalent conventional single-slice scan and the three-fold accelerated SMS acquisition. A 10% mean bias was observed in fractional anisotropy between single-slice and SMS acquisitions.
  
  
  CONCLUSIONS
  The new sequence was used to obtain high-quality diffusion measurements in three closely spaced cardiac slices in a clinically feasible nine breath-hold examination. The accelerated multiband sequence is anticipated to improve quantitative measurements of cardiac microstructure by reducing the number of breath-holds required for the scan, making it practical to incorporate diffusion tensor measurements within a comprehensive clinical examination.
authors.affiliation: Department of Cardiovascular Medicine, Oxford Centre for Clinical Magnetic Resonance Research, John Radcliffe Hospital, University of Oxford, UK; Department of Physiology, Anatomy, and Genetics, University of Oxford, UK.
authors.forename: Angus Z
authors.initials: AZ
authors.lastname: Lau
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Tunnicliffe
authors.forename: Robert
authors.initials: R
authors.lastname: Frost
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Koopmans
authors.forename: Damian J
authors.initials: DJ
authors.lastname: Tyler
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Robson
mesh_terms: D000328:Adult; D000465:Algorithms; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006352:Heart Ventricles / Q000166:cytology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: blipped CAIPI; cardiac; diffusion; multiband; parallel imaging; simultaneous multislice