title: Extended hybrid-space SENSE for EPI: Off-resonance and eddy current corrected joint interleaved blip-up/down reconstruction.
abstract: Geometric distortions along the phase encode direction caused by off-resonant spins are still a major issue in EPI based functional and diffusion imaging. If the off-resonance map is known it is possible to correct for distortions. Most correction methods operate as a post-processing step on the reconstructed magnitude images.
  
  
  
  Here, we present an algebraic reconstruction method (hybrid-space SENSE) that incorporates a physics based model of off-resonances, phase inconsistencies between k-space segments, and T2*-decay during the acquisition. The method can be used to perform a joint reconstruction of interleaved acquisitions with normal (blip-up) and inverted (blip-down) phase encode direction which results in reduced g-factor penalty.
  
  
  
  A joint blip-up/down simultaneous multi slice (SMS) reconstruction for SMS-factor 4 in combination with twofold in-plane acceleration leads to a factor of two decrease in maximum g-factor penalty while providing off-resonance and eddy-current corrected images.
  
  
  
  We provide an algebraic framework for reconstructing diffusion weighted EPI data that in addition to the general applicability of hybrid-space SENSE to 2D-EPI, SMS-EPI and 3D-EPI with arbitrary k-space coverage along z, allows for a modeling of arbitrary spatio-temporal effects during the acquisition period like off-resonances, phase inconsistencies and T2*-decay. The most immediate benefit is a reduction in g-factor penalty if an interleaved blip-up/down acquisition strategy is chosen which facilitates eddy current estimation and ensures no loss in k-space encoding in regions with strong off-resonance gradients.
authors.affiliation: Stanford University, Department of Radiology, Stanford, CA, United States. Electronic address: benjamin.zahneisen@gmail.com.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Zahneisen
authors.affiliation: Stanford University, Department of Radiology, Stanford, CA, United States.
authors.forename: Murat
authors.initials: M
authors.lastname: Aksoy
authors.affiliation: Stanford University, Department of Radiology, Stanford, CA, United States.
authors.forename: Julian
authors.initials: J
authors.lastname: Maclaren
authors.affiliation: Stanford University, Department of Radiology, Stanford, CA, United States.
authors.forename: Christian
authors.initials: C
authors.lastname: Wuerslin
authors.affiliation: Stanford University, Department of Radiology, Stanford, CA, United States.
authors.forename: Roland
authors.initials: R
authors.lastname: Bammer
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D017352:Echo-Planar Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008959:Models, Neurological; D012815:Signal Processing, Computer-Assisted