Jaejin Cho1,2, Avery JL Berman1,2, Borjan Gagoski2,3, Congyu Liao4, Jason Stockmann1,2, Jonathan R Polimeni1,2, and Berkin Bilgic1,2
1Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 4Radiological Sciences Laboratory, Stanford University, Palo Alto, CA, United States
1Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 4Radiological Sciences Laboratory, Stanford University, Palo Alto, CA, United States
We propose VUDU for motion-robust, distortion-free multi-shot EPI acquisition for GRE and DWI. VUDU acquires two EPI shots for each slice in quick succession and alternates the phase encoding polarity to encode B0 information.
Fig1. Proposed VUDU sequence and reconstruction for GRE contrast. Using FLEET ordering, two shots of EPI are acquired successively for each slice, before proceeding to the next slice. Phase encoding polarity is alternated between the shots. Variable flip angle (vfa) excitation maximizes the signal. A fieldmap estimated from interim blip-up and -down reconstructions is incorporated into parallel imaging model to jointly reconstruct two shots with low-rank regularization to eliminate distortion. In SE/diffusion variant, 180° refocusing pulses succeed each excitation pulse.
Fig2. shows individual SENSE reconstructions for each shot of vfa-FLEET acquisition with GRE contrast. At TRslice=80 msec, it took vfa-FLEET 160 msec to encode each slice, and 5.1 sec for the entire volume.
Horizontal lines help compare the geometric fidelity of distortion-free VUDU reconstruction relative to each shot. Yellow and blue arrows point to distortion artifacts in the sagittal views of SENSE reconstructions, which were eliminated in the VUDU result.
