Highly accelerated EPI with wave encoding and multi‐shot simultaneous multislice imaging

作者：Jaejin Cho, Congyu Liao, Qiyuan Tian, Zijing Zhang, Jinmin Xu, Wei‐Ching Lo, Benedikt A. Poser, V. Andrew Stenger, Jason Stockmann, Kawin Setsompop, Berkin Bilgiç · 发表于：Magnetic Resonance in Medicine · 年份：2022 · DOI：10.1002/mrm.29291 · 被引用次数：9 · 研究领域：Advanced MRI Techniques and Applications、Advanced Neuroimaging Techniques and Applications、Functional Brain Connectivity Studies

Purpose To introduce wave‐encoded acquisition and reconstruction techniques for highly accelerated EPI with reduced g‐factor penalty and image artifacts. Theory and Methods Wave‐EPI involves application of sinusoidal gradients during the EPI readout, which spreads the aliasing in all spatial directions, thereby taking better advantage of 3D coil sensitivity profiles. The amount of voxel spreading that can be achieved by the wave gradients during the short EPI readout period is constrained by the slew rate of the gradient coils and peripheral nerve stimulation monitor. We propose to use a “half‐cycle” sinusoidal gradient to increase the amount of voxel spreading that can be achieved while respecting the slew and stimulation constraints. Extending wave‐EPI to multi‐shot acquisition minimizes geometric distortion and voxel blurring at high in‐plane resolutions, while structured low‐rank regularization mitigates shot‐to‐shot phase variations. To address gradient imperfections, we propose to use different point spread functions for the k‐space lines with positive and negative polarities, which are calibrated with a FLEET‐based reference scan. Results Wave‐EPI enabled whole‐brain single‐shot gradient‐echo (GE) and multi‐shot spin‐echo (SE) EPI acquisitions at high acceleration factors at 3T and was combined with g‐Slider encoding to boost the SNR level in 1 mm isotropic diffusion imaging. Relative to blipped‐CAIPI, wave‐EPI reduced average and maximum g‐factors by up to 1.21‐ and 1...