title: Fast susceptibility-weighted imaging with three-dimensional short-axis propeller (SAP)-echo-planar imaging.
abstract: BACKGROUND
  Susceptibility-weighted imaging (SWI) in neuroimaging can be challenging due to long scan times of three-dimensional (3D) gradient recalled echo (GRE), while faster techniques such as 3D interleaved echo-planar imaging (iEPI) are prone to motion artifacts. Here we outline and implement a 3D short-axis propeller echo-planar imaging (SAP-EPI) trajectory as a faster, motion-correctable approach for SWI.
  
  
  METHODS
  Experiments were conducted on a 3T MRI system. The 3D SAP-EPI, 3D iEPI, and 3D GRE SWI scans were acquired on two volunteers. Controlled motion experiments were conducted to test the motion-correction capability of 3D SAP-EPI. The 3D SAP-EPI SWI data were acquired on two pediatric patients as a potential alternative to 2D GRE used clinically.
  
  
  RESULTS
  The 3D GRE images had a better target resolution (0.47 × 0.94 × 2 mm, scan time = 5 min), iEPI and SAP-EPI images (resolution = 0.94 × 0.94 × 2 mm) were acquired in a faster scan time (1:52 min) with twice the brain coverage. SAP-EPI showed motion-correction capability and some immunity to undersampling from rejected data.
  
  
  CONCLUSIONS
  While 3D SAP-EPI suffers from some geometric distortion, its short scan time and motion-correction capability suggest that SAP-EPI may be a useful alternative to GRE and iEPI for use in SWI, particularly in uncooperative patients.
authors: Lucas MRI Center, Department of Radiology, Stanford University, Stanford, California, USA.
authors: Samantha J
authors: SJ
authors: Holdsworth
authors: Kristen W
authors: KW
authors: Yeom
authors: Michael E
authors: ME
authors: Moseley
authors: S
authors: S
authors: Skare
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D009038:Motion; D064847:Multimodal Imaging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: SAP-EPI; Short-Axis Propeller EPI; motion correction; susceptibility-weighted imaging, SWI