title: Scan time reduction for readout-segmented EPI using simultaneous multislice acceleration: Diffusion-weighted imaging at 3 and 7 Tesla.
abstract: OBJECTIVE
  Readout-segmented echo-planar imaging (rs-EPI) can provide high quality diffusion data because it is less prone to distortion and blurring artifacts than single-shot echo-planar imaging (ss-EPI), particularly at higher resolution and higher field. Readout segmentation allows shorter echo-spacing and echo train duration, resulting in reduced image distortion and blurring, respectively, in the phase-encoding direction. However, these benefits come at the expense of longer scan times because the segments are acquired in multiple repetitions times (TRs). This study shortened rs-EPI scan times by reducing the TR duration with simultaneous multislice acceleration.
  
  
  METHODS
  The blipped-CAIPI method for slice acceleration with reduced g-factor SNR loss was incorporated into the diffusion-weighted rs-EPI sequence. The rs- and ss-EPI sequences were compared at a range of resolutions at both 3 and 7 Tesla in terms of image fidelity and diffusion postprocessing results.
  
  
  RESULTS
  Slice-accelerated clinically useful trace-weighted images and tractography results are presented. Tractography analysis showed that the reduced artifacts in rs-EPI allowed better discrimination of tracts than ss-EPI.
  
  
  CONCLUSIONS
  Slice acceleration reduces rs-EPI scan times providing a practical alternative to diffusion-weighted ss-EPI with reduced distortion and high resolution. Magn Reson Med 74:136-149, 2015. © 2014 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
authors: FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors: Robert
authors: R
authors: Frost
authors: FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors: Peter
authors: P
authors: Jezzard
authors: FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors: Gwenaëlle
authors: G
authors: Douaud
authors: FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors: Stuart
authors: S
authors: Clare
authors: Siemens AG, Healthcare Sector, Erlangen, Germany.
authors: David A
authors: DA
authors: Porter
authors: FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom.
authors: Karla L
authors: KL
authors: Miller
keywords: blipped-CAIPI; diffusion MRI; distortion; readout-segmented EPI; simultaneous multislice; tractography