SENSE reconstruction for multiband EPI including slice-dependent N/2 ghost correction

Abstract

Purpose: Sensitivity encoding (SENSE) reconstruction of multiband echo planar imaging (EPI) may cause artifacts when simultaneously excited slices require different phase correction to remove the EPI-specific ghost shifted by half of the matrix size (N). We propose a simplified solution of this problem that combines SENSE unfolding with the EPI phase correction in the image domain. Theory and Methods: Slice-dependent phase correction was included in equations linking folded slice images reconstructed separately from even and odd echoes of all receivers with the true images of each slice. Compared with the previously proposed combination of ghost suppression with SENSE based on a direct image fit to echo data, our method reduces the problem complexity by N2/4. It was applied to reconstruct images of phantoms and human brain. Results: The proposed method tolerates high differences of phase correction between slices, which may result, e.g., from anisotropic gradient delay. It suppresses artifacts better than standard SENSE even when the latter is repeated with the ghost correction targeting each of the slices and works significantly faster than the direct fit version of ghost-correcting SENSE. Conclusion: With the proposed modification SENSE allows a rapid separation of slices simultaneously acquired with EPI even when the phase correction needed for each slice is different. Magn Reson Med 76:873–879, 2016. © 2015 Wiley Periodicals, Inc.